Biomedical subjects

C C Lee

Publications and source records attributed to C C Lee.

At least 343 records · Page 19Linked to original sources

PubMed1993

Criteria for in vitro alternatives for the eye irritation test.

A proposal encompassing considerations and criteria for the development of in vitro alternatives to the eye irritation test has been developed and is presented here. Two factors need to be considered initially in developing an alternative test. The first is to determine whether the alternative assay is to be used as a screen or as a replacement for the eye irritation test. Less stringent acceptance criteria are required for an assay used as a screen than for that used as a replacement test. A screen is a preliminary test for the assessment of eye irritation. It is used for making preliminary decisions or establishing the direction for further testing. Screens answer fewer and less complex questions than a replacement test would, since the results from screens are usually confirmed by more definitive testing. A replacement test, however, must provide the same answers as in vivo methods for the assessment of eye irritation and must provide data for making a definitive toxicological assessment of eye irritation. The second factor to be considered is knowledge of the in vivo assay intended to be replaced. This knowledge should include the procedural aspects of the test and the regulatory information it provides. The following may be considered as criteria for in vitro tests used as screens or as replacements for the eye irritation test in rabbits: rationale (there should be a clear statement regarding the rationale for the use of a particular test in relation to the availability of other tests); relevance (the in vitro endpoint should have biological or physiological relevance to the effect to be detected in vivo); and validational (intralaboratory as well as interlaboratory validation must be conducted).

Animal Testing Alternatives↗

PubMed1993

Screening procedures for eye irritation.

Screens aid in identifying some severe irritants or corrosives and eliminating them from consideration for in vivo eye irritation testing. Products may be evaluated for ocular irritation potential in a stepwise progression as follows: (1) products at pH extremes of 2 or below or of 11.5 or above may be considered to be ocular irritants; (2) based on chemical structure-activity considerations, some products may be judged to have ocular irritation potential; (3) validated and accepted in vitro systems may possibly be used as a screen in the future; (4) when a test material demonstrates severe acute dermal toxicity (lethality at < or = 200 mg/kg body weight), further testing for either dermal or ocular irritation may not need to be undertaken; (5) if a substance shows a primary dermal irritation index of 5 or above, it may be considered to be an ocular irritant; (6) materials that are not removed from consideration based on these proposed screens may then be considered for testing for ocular irritation in rabbits under accepted procedures. In a survey given to participants in the workshop, a high percentage believed that screens should be used. However, opinions on the use of the individual screens varied between the different interested groups attending, with the possible future use of in vitro screens for specific product lines having the highest percentage of agreement (57-100%).

Animal Testing Alternatives↗

PubMed1993

Use of ophthalmic topical anaesthetics.

Pretreatment of the eyes of rabbits with a topical anaesthetic can be viewed as a refinement of the test for eye irritation. It reduces pain at the time of test-material administration, decreases animal distress and permits easier application of the test agent to the eye. In some cases, however, use of an anaesthetic either alone or in combination with the test substance may alter ocular responses or provide little benefit. Although anaesthetic pretreatment may result in decreased pain at the time of test-compound administration, it does not affect possible pain after the effects of the anaesthetic have dissipated. Some anaesthetics are themselves irritating to eyes. In addition, anaesthetics reduce blinking and tearing, thereby maintaining the test-material concentration at the surface of the eye longer. Corneal permeability may also be increased with pretreatment use of an anaesthetic, and may bring the test agent into contact with more structures of the eye. Some anaesthetics delay healing after ocular injury. All of these varied effects may result in increased irritation to the eye. Overall, pretreatment with anaesthetics has usually resulted in a tendency for slightly higher irritation scores; eye irritancy classification is usually unaffected.

Anesthetics, Local↗

PubMed1993

The use of low-volume dosing in the eye irritation test.

The Draize rabbit eye test was developed to provide a method for assessing the irritation potential of materials that might come in contact with human eyes. The method involves the instillation of 0.1 ml of a test liquid (100 mg solid) into the conjunctival sac of an animal's eye. A refinement of the Draize test is the low-volume eye test in which 0.01 ml of a substance is placed directly on the cornea of the eye. Studies indicate that the low-volume method provides a better correlation to human eye irritation experience for some substances. The Interagency Regulatory Alternatives Group (IRAG) proposes that the low-volume eye test can be used to substantiate the irritancy of suspect severe ocular irritants that have not been eliminated by various pre-eye test 'screens'. A substance testing positive by the low-volume method can be classified as an irritant; one that tests negative will require further testing by the use of the 0.1-ml volume procedure. For all other definitive testing, the Draize test (0.1 ml) should be used. Results from a questionnaire distributed at the IRAG workshop showed that many workshop participants thought that the low-volume test should be used as an eye irritation screening procedure.

Animal Testing Alternatives↗

PubMed1993

Number of animals for sequential testing.

US regulatory agencies have used six animals in eye irritation tests. Analyses of eye irritation tests on pesticides (n = 48), consumer products and cosmetics (n = 53), Marzulli and Ruggles database (n = 139), and cleaning products and ingredients (n = 30) have greatly extended previous investigations of the merit of reducing animal sample size in the eye test. Given the existing scoring system for positive animal responses (corneal opacity > or = 1, iritis > or = 1, conjunctival redness > or = 2 and conjunctival chemosis > or = 2), the accuracy of the classification systems currently used by these agencies was determined. The US Consumer Product Safety Commission, US Food and Drug Administration, and US Occupational Safety and Health Administration use a classification system by which a substance is designated as an irritant when at least four of six animals give a positive response. This decision rule leads to a very high accuracy of at least 99% with essentially no false positive and false negative judgments. In contrast, the system used by the US Environmental Protection Agency pesticide program, in which only one or more of six treated animals result in an irritant decision, has an accuracy of only 50-80% with very high false positive rates. Analyses indicated that test sample size could be reduced to three and still preserve very good accuracy, whereas two-animal and one-animal tests did not give satisfactory responses. A two-stage test, in which two animals are tested and evaluated in the first stage before the need for testing one more animal in the second stage is determined, also demonstrated good operating characteristics. Both the one-stage/three-animal test and the two-stage test deserve consideration.

Animals↗

PubMed1993

Scoring for eye irritation tests.

Scoring of the rabbit eye test and the resulting evaluation and classification should provide useful information about the likelihood that a test material may cause injury on contact with the human eye. When an animal test is necessary, a rabbit eye test based on the following characteristics is proposed for deriving the maximum information from the fewest animals. The ocular effects of interest should include corneal opacity, iritis and conjunctival redness. Animals should be scored for each ocular effect at 24, 48 and 72 hr after the test substance is administered. If an animal is negative at all three scoring times, it can be removed from the test at 72 hr. If it shows a positive effect at a scoring time but the lesion clears at 72 hr, it can be removed at 72 hr. If it shows a positive effect that does not clear at 72 hr, it should be scored again on day 7 when the test ends. However, if an animal shows severe effects at one or more scoring times, it can be removed from the test at 72 hr. An animal is positive if any one of the following criteria is observed at 24, 48 or 72 hr: corneal opacity of 1 or above, iritis of 1 or above, or conjunctival redness of 2 or above. Severe ocular effects (noted at 24, 48 or 72 hr) that may endanger sight deserve special recognition for the classification of chemicals and include corneal opacity of 3 or above, or iritis of 2. This proposal is consistent with the opinions of the majority of respondents who attended the Workshop on Updating Eye Irritation Test Methods, Proposals for Regulatory Consensus. The most notable exception was the suggestion by respondents to add conjunctival chemosis as one of the scoring parameters.

Animals↗

PubMed1993

Progesterone inhibits the estrogen-induced prolactin gene expression in the rat pituitary.

The present study examines the inhibitory action of progesterone (P) on prolactin (PRL) gene expression in the anterior pituitary of ovariectomized, estradiol (OVX+E) treated adult rats. A single injection of P (1 mg) was administered s.c. to OVX+E treated rats, and animals were killed at 3, 6, 9, and 36 h following P administration. Northern blot analysis showed that P suppressed the E-enhanced PRL mRNA level at 3, 6, and 9 h, but not at 36 h following P administration. When the second injection of P (1 mg) was given at 30 h after the first P, it again suppressed the E-induced PRL mRNA level, indicating that the inhibitory effect of P may not last until 36 h. The inhibitory action of P was dose-dependent, and the pretreatment of RU486 (100 micrograms/rat), a P receptor antagonist at 1 h before P injection partially restored PRL mRNA level which was inhibited by P. These data indicate that P plays a crucial role in the regulation of PRL gene expression in the rat pituitary.

Animals↗

PubMed1993

Full-scale evaluation of the thermal stability-based hazardous organic waste incinerability ranking.

The results of a full-scale evaluation of the thermal stability-based hazardous organic waste incinerability ranking are presented. Tests were conducted for a surrogate mixture consisting of sulfur hexafluoride, chlorobenzene, toluene, tetrachloroethene, methylene chloride, 2-chloropropene and 1,1,1-trichloroethane under nominal incinerator operating conditions. Based on median surrogate DREs, the results indicated that the pyrolytic ranking was statistically significant at the 90 percent confidence level while the oxidative ranking was statistically significant at the 97.5 percent confidence level. The heat of combustion ranking failed to give a statistically significant correlation at the 90 percent confidence level. The statistical success of the thermal stability rankings and statistical failure of the heat of combustion ranking suggest that chemical reaction kinetics controlled the relative emission rates of the surrogate compounds during these tests.

Journal Article↗

PubMed1993

Mdx transgenic mouse: restoration of recombinant dystrophin to the dystrophic muscle.

We report the restoration of the 430-kD dystrophin in mdx, the mouse model of Duchenne muscular dystrophy, by expression of a single-copy recombinant dystrophin transgene. Muscle-specific expression was achieved using a creatine kinase promoter influenced by two enhancers. Immunostaining with anti-Xp21-coded dystrophin monoclonal antibodies showed that the recombinant dystrophin was localized to the muscle fiber membrane. However, there was variability in the level of dystrophin expression in various animals with aging, between fast and slow muscles, and within different regions of the same muscle. Curiously, recombinant dystrophin was relatively absent in the diaphragm muscle of these mdx transgenic animals. Our studies indicate that there is a direct correlation between the level of muscle fibers expressing recombinant dystrophin and the level of muscle fibers with peripheral nuclei, indicating an improvement in muscle pathology. These studies indicate that the regional expression of recombinant dystrophin in dystrophic muscle leads to regional restoration of normal muscle morphology.

Animals↗

PubMed1993

Leukotrienes D4 and E4 produced in myocardium impair coronary flow and ventricular function after two hours of global ischaemia in rat heart.

OBJECTIVE: Leukotrienes D4 and E4 are potent coronary vasoconstrictors and myocardial depressants. The aim was to investigate the contribution of myocardial leukotrienes to impairment of coronary flow and recovery of contractile function in rat hearts subjected to 2 h of global ischaemia. METHODS: Rat hearts were mounted on a working Langendorff apparatus and perfused with oxygenated Krebs-Henseleit solution at 37 degrees C for 30 min. Hearts were then arrested with either standard potassium crystalloid cardioplegic solution (n = 6), or with cardioplegic solution containing the leukotriene D4, E4 receptor antagonist Ly171883 (n = 6). Arrested hearts were maintained at 15 degrees C for 2 h, then rewarmed to 37 degrees C during 30 min working reperfusion. Coronary effluent was analysed by radioimmunoassay for leukotriene C4, D4, E4, and F4 levels. Immediately prior to cardiac arrest, and again after 30 min reperfusion, coronary flow, and aortic outflow and pressure were measured. RESULTS: Postischaemic leukotriene levels were increased compared to preischaemic levels in both groups [pooled measurements: 133.3 (SD 136.4) v 20.7(17.8) pg.0.1 ml-1, p < 0.05]. Postischaemic coronary vascular resistance was increased by 80% in controls (p < 0.001) compared to 19% (p = NS) in treated hearts. In addition, functional recovery was significantly greater in treated hearts compared to controls [82(3)% v 53(3)% for coronary flow; 79(3)% v 50(2)% for cardiac output; 82(4)% v 54(3)% for stroke work]. CONCLUSIONS: Leukotrienes are endogenously produced by the heart, and this production is significantly increased after global ischaemia and reperfusion. Reversal of significantly increased coronary vascular resistance coupled with improved functional recovery in hearts treated with LY171883 demonstrates an important contribution of endogenously produced leukotrienes to coronary vascular impairment and functional stunning of the globally ischaemic, reperfused heart.

Acetophenones↗

PubMed1993

Analysis of arterial waves by the single-pulse-response method.

This study introduces an improved method to determine experimentally the characteristic arterial impedance, and the forward and backward wave components in the carotid artery of the rabbit. This method is based on the concept of the "single-pulse response," i.e., the pressure and flow responses to a single cardiac contraction.

Animals↗

PubMed1993

Overlapping syndrome of MERRF and MELAS: molecular and neuroradiological studies.

We describe a 42-year-old woman with overlapping syndrome of MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes) and MERRF (myoclonus epilepsy and ragged-red fibers). Clinically, she had episodic headache, stroke-like episode with left hemiparesis and lactic acidosis commonly found in MELAS syndrome. However, myoclonus seizure, and ataxia with dyssynergic gait characteristic of MERRF were also noted. Computed tomographic scans showed a right temporo-parietal hypodense lesion. The lesion disappeared 20 months later, even magnetic resonance images also failed to reveal this abnormality. A molecular analysis of mitochondrial DNA was conducted by using restriction endonucleases ApaI and NaeI. A transition from A to G was found at the nucleotide position 3243, but not found at the 8344th nucleotide pair. In this report, we document the fluctuating CT changes and emphasize the importance of molecular analysis in patients with overlapping syndrome of mitochondrial encephalomyopathies.

Adult↗

PubMed1993

Sympathectomy and beta-adrenergic blockade during lung maturation stimulated by TRH and cortisol in fetal sheep.

To test whether beta-adrenergic mechanisms and the sympathetic nervous system are involved in the synergistic action of thyrotropin-releasing hormone (TRH) and cortisol on lung maturation, fetal sheep (n = 32) were infused from 121 to 128 days of gestation with saline, TRH + cortisol, TRH + cortisol + beta-adrenergic blocker, or TRH + cortisol after chemical sympathectomy with 6-hydroxydopamine. TRH + cortisol increased lung distensibility and stability and alveolar concentrations of saturated phosphatidylcholine two- to threefold over control fetuses. beta-Adrenergic blockade prevented the increase in distensibility in response to TRH + cortisol. Sympathectomy did not impair the increase in distensibility and stability in response to TRH + cortisol but inhibited the increase in alveolar total phospholipids. Tissue concentrations of saturated phosphatidylcholine increased in TRH + cortisol-treated fetuses after either sympathectomy or beta-adrenergic blockade. We concluded that during lung maturation by TRH + cortisol 1) sympathetic mechanisms are requisite for surfactant release, 2) nonneurogenic beta-adrenergic mechanisms are requisite for the maturation of the mechanical properties of the lung and 3) stimulation of surfactant synthesis is independent of beta-adrenergic action and the sympathetic nervous system.

Adrenergic beta-Antagonists↗

PubMed1993

A partial blockade of catecholaminergic neurotransmission with 6-hydroxydopamine decreases mRNA level of gonadotropin releasing hormone in the male rat hypothalamus.

Central catecholamines (CA) are known to be involved in the regulation of synthesis and secretion of gonadotropin releasing hormone (GnRH) from the hypothalamus. However, no attempt has been yet made to determine whether CA affects GnRH gene expression. To this end, the effect of 6-hydroxydopamine (6-OHDA), a catecholaminergic neurotoxin, on GnRH mRNA level was examined. Hypothalamic tissues obtained from adult male rats were incubated with medium containing 6-OHDA. To ensure the effect of 6-OHDA on CA depleting action, CA levels in media and in postincubation tissues were determined. Increasing concentrations of 6-OHDA resulted in decrease in norepinephrine (NE) and dopamine (DA) contents in a dose dependent manner. Treatment with 6-OHDA (5 x 10(-4) M produced a time-dependent decrease in NE but not DA, when CA levels in media were determined at 30 min intervals during the incubation period. To determine changes in GnRH mRNA level in response to 6-OHDA treatment in vitro, for 2.5 h total cytoplasmic RNA fractions were isolated from postincubation hypothalamic tissues and used for RNA-blot hybridization with 32P-labeled GnRH riboprobe. A blockade of CA neurotransmission with 6-OHDA (5 x 10(-4) M) significantly reduced GnRH mRNA level by half over its control and internal control (actin mRNA) groups. Northern blot analysis revealed that addition of NE (1 x 10(-6) M) reversed the decreased GnRH mRNA level by 6-OHDA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

NMDA receptor antagonist decreases the progesterone-induced increase in GnRH gene expression in the rat hypothalamus.

We previously reported that GnRH gene expression was enhanced by progesterone (P) in the hypothalamus from ovariectomized and estrogen (OVX+E) treated immature rats. Recent studies indicate that excitatory amino acids may play an important role in the regulation of GnRH secretion and gene expression by steroids. Therefore the present study attempts to examine whether excitatory amino acids are involved in the P-induced GnRH gene expression and release in vitro. MK-801, an NMDA receptor antagonist or CNQX, a non-NMDA receptor antagonist, was administered to OVX+E+P-treated prepubertal female rats. GnRH mRNA was determined by Northern blot hybridization using 32P-labeled antisense RNA, and GnRH release in vitro from the hypothalamic fragments was monitored by GnRH radioimmunoassay. The administration of MK-801 (0.2 mg/kg) for 2 h significantly reduced the P-induced GnRH gene expression and release, whereas CNQX (0.4 mg/kg) had no effect. These results clearly indicate that excitatory amino acids by way of NMDA receptor are involved in the transsynaptic regulation of GnRH gene expression.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1993

Acute lung injury at Baragwanath ICU. An eight-month audit and call for consensus for other organ failure in the adult respiratory distress syndrome.

To test the expanded definition of acute lung injury (ALI), we prospectively, over a period of 8 months, studied all adult ICU admissions who fitted the definition. Our study consisted of 83 patients with the adult respiratory distress syndrome (ARDS) and 60 with mild to moderate ALI. Sepsis and trauma were the most common diagnoses on admission. The overall mortality rate was 45 percent for ARDS and 38 percent in the other group. Mortality rose significantly with associated other organ failure, the incidence of which was as follows: hepatic, 39 percent; cardiac, 38 percent; hematologic, 22 percent; renal, 21 percent; neurologic, 5 percent. Sepsis syndrome eventually occurred in 73 percent and septic shock in 38 percent of all cases of ALI. We found the expanded definition a useful grading system and consider this definition of ARDS to be currently the best. There are, however, problems with the determination of lung compliance, the effect of inverse ratio ventilation, and the lack of consensus in defining other organ failure.

Adult↗

PubMed1993

Structure, genetic mapping, and expression of the mouse Hgf/scatter factor gene.

The cytokine termed hepatocyte growth factor or scatter factor (HGF/SF) has been implicated in embryonic development and liver regeneration. Mouse HGF/SF cDNA clones were obtained by screening a mouse liver cDNA library with synthetic oligonucleotides, as well as by using the method of reverse transcription-polymerase chain reaction (RT-PCR) with mRNA isolated from adult mouse brain. Sequence analysis of mouse HGF/SF cDNA clones spanning the entire coding region revealed an overall amino acid identity of 90% and 98% with human and rat HGF, respectively. Using mouse HGF antisense RNA as a probe, we observed the expression of HGF/SF mRNA in the liver, kidney, whole brain and cerebellum of adult mice as well as in day 9 and day 10 mouse embryos. The mouse HGF/SF cDNA was utilized for mapping Hgf to the centromeric region of mouse Chromosome 5 in apparent close proximity to the reeler mutation by the analysis of two multilocus crosses. The relationship of Hgf to the reeler mutation is discussed. The availability of mouse HGF/SF cDNA clones should facilitate further analysis of HGF/SF function during development.

Amino Acid Sequence↗

PubMed1993

Hematuria due to nutcracker phenomenon of left renal vein: report of a case.

The nutcracker phenomenon refers to compression of the left renal vein between the aorta and the superior mesenteric artery, which leads to painless intermittent gross hematuria. An 11-year-old girl presented with a two-year history of recurrent painless hematuria. Physical examination and routine laboratory examinations were noncontributory. Renal ultrasonographic study, selective left renal angiography and retrograde left renal venography showed evidence of compression of the left renal vein where it crossed between the aorta and the superior mesenteric artery. A needle biopsy of the right kidney revealed no abnormal histologic change. These results led to a diagnosis of the nutcracker phenomenon; to the best of our knowledge, this may be the first case reported in Taiwan. Herein, we present our experience with this case and discuss the diagnostic options.

Angiography, Digital Subtraction↗