Biomedical subjects
Publications and source records attributed to J K Liu.
A new C(18)-phytosphingosine ceramide containing non-hydroxy fatty acid, armillaramide (1), has been isolated together with ergosterol peroxide from the fruiting bodies of the basidiomycete Armillaria mellea. Its structure was established as (2S,3S,4R)-2-hexadecanoylamino-octadecane-1,3,4-triol by spectroscopic and chemical methods.
The green alga Selenastrum capricornutum expresses a unique ascorbate peroxidase, that responds to copper and lead. Attempts were made to test if this peroxidase could be used to monitor the levels of copper and lead in natural waters. When S. capricornutum was exposed to a stormwater sample, the specific activity of the peroxidase in the cell extract was commensurate with the combined copper and lead contents in the sample. The peroxidase responses were also correlated with the 96 hr biomass toxicity assay of S. capricornutum. However, unlike the biomass toxicity assay, the peroxidase activity was not affected by the anions in the samples. The use of this peroxidase can be used as a marker for testing heavy metal toxicity in the water.
STATEMENT OF PROBLEM: When inexperienced clinicians perform class II composite restorations, improper placement techniques can lead to problems, including marginal adaptation and void formation. PURPOSE: The aim of this study was to determine the influence of flowable composite linings on marginal microleakage and internal voids in class II composite restorations performed by practitioners with different levels of experience. MATERIAL AND METHODS: Eighty extracted molars were prepared with mesial and distal class II cavity preparations and divided into 4 groups. Each group was restored separately with the following materials: Prodigy/Revolution lining (group I), Prodigy (group II), Tetric Ceram/Tetric Flow lining (group III), and Tetric Ceram (group IV). Each group was equally divided and restored by 2 practitioners, one experienced and another untrained in composite restorations. After restoration, all teeth were stored for 24 hours, thermocycled (at 5 degrees C to 60 degrees C) 1500 times, and soaked in 2% basic Fuchsin dye for 24 hours. After soaking, the teeth were sectioned, and gingival marginal microleakage and internal voids (at the gingival wall interface and in the cervical and the occlusal parts) were recorded. Data were analyzed with the Kruskal-Wallis test. RESULTS: There was no significant reduction in microleakage for either practitioner. There were fewer interface voids within pairs with or without flowable composite linings made by the experienced practitioner (P<.05). CONCLUSION: When flowable composite lining was placed at the gingival floor of a class II composite restoration by an experienced practitioner, voids in the restored interface were reduced. Gingival marginal sealing was not improved by the same technique.
Initial attempts at transcranial approaches to the pituitary gland in the late 1800s and early 1900s resulted in a mortality rate that was generally considered prohibitive. Schloffer suggested the use of a transsphenoidal route as a safer, alternative approach to the sella turcica. He reported the first successful removal of a pituitary tumor via the transsphenoidal approach in 1906. His procedure underwent a number of modifications by interested surgeons, the culmination of which was A. E. Halstead's description in 1910 of a sublabial gingival incision for the initial stage of exposure. From 1910 to 1925, Cushing, combining a number of suggestions made by previous authors, refined the transsphenoidal approach and used it to operate on 231 pituitary tumors, with a mortality rate of 5.6%. As he developed increasing expertise with transcranial surgery, however, Cushing reduced his mortality rate to 4.5%. With the transcranial approach, he was able to verify suprasellar tumors and achieve better decompression of the optic apparatus, resulting in better recovery of vision and a lower recurrence rate. As a result he and most other neurosurgeons at the time abandoned the transnasal in favor of the transcranial approaches. Norman Dott, a visiting scholar who studied with Cushing in 1923, returned to Edinburgh, Scotland, and continued to use the transsphenoidal procedure while others pursued transcranial approaches. Dott introduced the procedure to Gerard Guiot, who published excellent results with the transsphenoidal approach and revived the interest of many physicians throughout Europe in the early 1960s. Jules Hardy, who used intraoperative fluoroscopy while learning the transsphenoidal approach from Guiot, then introduced the operating microscope to further refine the procedure; he thereby significantly improved its efficacy and decreased surgical morbidity. With the development of antibiotic drugs and modern microinstrumentation, the transsphenoidal approach became the preferred route for the removal of lesions that were confined to the sella turcica. The evolution of the transsphenoidal approaches and their current applications and modifications are discussed.
Objective. To study the serum antioxidant status in civil aircrew members who had more than 4000 h of cumulative flight hours, therefore exposed to a higher dose of cosmic radiation comparing to the dose received by ground residents. Method. Differences in the serum levels of total antioxidant capacity (TAOC), superoxide dismutase (SOD) and malondialdehyde (MDA) were investigated in 230 crew members, 37 local ground residents in Xinjiang, and 37 ground residents in Tianjin. Result. Significantly higher levels of all the three serum indexes were found in civil aircrew members. Serum levels of TAOC and SOD were higher in Xinjiang than in Tianjin ground residents, although no difference was found for MDA. Positive correlations were observed among the three serum indexes in this study. Conclusion. The elevated serum level of MDA in civil aircrew members deserves a proper attention by health care policy makers.
The ribonucleoprotein enzyme telomerase extends chromosome ends by copying a specific template sequence within its integral RNA component. An active recombinant telomerase RNP is minimally composed of this RNA and the telomerase reverse transcriptase (TERT) protein, which contains sequence motifs conserved among viral reverse transcriptases (RTs), flanked by N- and C-terminal extensions specific to TERTs. We have used site-directed mutagenesis to explore the roles of Tetrahymena TERT in determining features of telomerase activity in general and in establishing the boundaries and use of an internal RNA template in specific. We identify a new ciliate-specific motif in the TERT N-terminus required for template definition. Moreover, several residues in reverse transcriptase motifs 1, 2, A and D are critical for specific aspects of internal template use. Our results indicate that the unique specificity of telomerase activity is conferred to a reverse transcriptase active site by TERT residues both within and beyond the RT motif region.
Repeated prenatal exposure to cocaine is associated with attenuated respiratory and arousal responses in infants and piglets. As the normal development of these functions is influenced by medullary opioid systems, the present study explored the possible contribution of the opioid systems to the attenuation induced by cocaine. Methionine-enkephalin (met-enkephalin), an endogenous opioid peptide, was delineated by immunocytochemistry in respiratory- and arousal-related medullary regions of relatively immature (6-7-day-old) and more mature piglets (20-21-day-old). The animals were either unexposed, or exposed prenatally to 2 mg/kg cocaine four times daily administered to the pregnant sows intravenously throughout the last third of gestation. At control, met-enkephalin was found in the neurons, fibers and terminals of the respiratory- and arousal-related medullary regions throughout the age range studied. Prenatal cocaine exposure increased met-enkephalin immunoreactivity in the respiratory-related hypoglossal and solitary tract nuclei of both age groups. These findings support a modulatory role of met-enkephalin in the normal development of respiratory control, and an involvement of this peptide in the attenuation of respiration by repeated prenatal exposure to cocaine.
Two novel secoergosterols, 3beta-hydroxy-8alpha,9alpha-oxido-8, 9-secoergosta-7,9(11),22-triene (tylopiol A) (1) and 3beta-hydroxy-8alpha,9alpha-oxido-8,9-secoergosta-7,22 -dien-12-one (tylopiol B) (2), were isolated from the fresh fruit bodies of Tylopilus plumbeoviolaceus, along with three known compounds, ergosta-7,22-dien-3beta-ol, uridine, and allitol. Their structures were elucidated by NMR techniques, including (1)H NMR, (13)C NMR, HMQC, HMBC, and MS. The structure and stereochemistry of compound 1 were demonstrated by X-ray crystallography.
Computerized cephalometric analysis can include both landmark identification and determination of linear or angular measurements. Although its use is time saving compared with a manual method, the accuracy of automatic landmark identification remains unclear. The purpose of this study was to evaluate the accuracy of a computerized automatic landmark identification system that used an edge-based technique. The technique divides the scanned cephalogram into 8 rectangular subimage regions. After the resolution of these subimages is reduced, the edges are detected and the landmarks are located automatically. Thirteen landmarks were selected for assessment on a set of 10 test cephalograms. The results showed that the errors between manual and computerized identification for landmarks were not significantly different (P > .05) for 5 of 13 landmarks: sella, nasion, porion, orbitale, and gnathion. These results suggest that the accuracy of computerized automatic identification is acceptable for certain landmarks only. Further studies to improve the accuracy of computerized automated landmark identification are needed.
Statistical models were used to predict the effects of tryptone, glucose, yeast extract (TGY) and Mn on biomass formation of the highly radioresistant bacterium Deinococcus radiodurans. Results suggested that glucose had marginal effect on biomass buildup, but Mn was a significant factor for biomass formation. Mn also facilitated glucose interactions with other nutrient components. These predictions were verified by in vivo and in vitro experiments. TGY-grown cells metabolized glucose solely by the pentose phosphate pathway (PPP). Although only a fraction of glucose from the medium was transported into the cells, glucose was incorporated into the DNA efficiently after cells were exposed to UV light. The presence of glucose also enhanced the radioresistance of the culture. Mn could induce an Embden-Meyerhof-Parnas (EMP) pathway in D. radiodurans. The EMP pathway and the PPP of the Mn-treated cells oxidized glucose simultaneously at a 6:1 ratio. Although glucose was hydrolyzed rapidly by the Mn-treated cells, most glucose was released as CO(2). Mn-treated cultures retained less glucose per cell than cells grown without Mn, and still less glucose was incorporated into the DNA after cells were exposed to UV light. Mn-treated cells were also more sensitive to UV light. Results suggested that metabolites of glucose generated from the PPP enhanced the survival of D. radiodurans. Induction of the EMP pathway by Mn may deplete metabolites for DNA repair and may induce oxidative stress for the cell, leading to reduction of radioresistance.
Dlx2, a member of the distal-less gene family, is expressed in the first branchial arch, prior to the initiation of tooth development, in distinct, non-overlapping domains in the mesenchyme and the epithelium. In the mesenchyme Dlx2 is expressed proximally, whereas in oral epithelium it is expressed distally. Dlx2 has been shown to be involved in the patterning of the murine dentition, since loss of function of Dlx1 and Dlx2 results in early failure of development of upper molar teeth. We have investigated the regulation of Dlx2 expression to determine how the early epithelial and mesenchymal expression boundaries are maintained, to help to understand the role of these distinct expression domains in patterning of the dentition. Transgenic mice produced with a lacZ reporter construct, containing 3.8 kb upstream sequence of Dlx2, led to the mapping of regulatory regions driving epithelial but not mesenchymal expression in the first branchial arch. We show that the epithelial expression of Dlx2 is regulated by planar signalling by BMP4, which is coexpressed in distal oral epithelium. Mesenchymal expression is regulated by a different mechanism involving FGF8, which is expressed in the overlying epithelium. FGF8 also inhibits expression of Dlx2 in the epithelium by a signalling pathway that requires the mesenchyme. Thus, the signalling molecules BMP4 and FGF8 provide the mechanism for maintaining the strict epithelial and mesenchymal expression domains of Dlx2 in the first arch.
A novel monoterpenoid-derived metabolite, paeonilide, was isolated from the roots of Paeonia delavayi. Its structure was established by a combination of spectroscopic and X-ray crystallographic analyses. It showed an anti-PAF effect with an IC50 value of ca. 8 microg/ml.
The prevalence of the blood-borne TT virus (TTV) in Italian hemophiliacs treated with different preparations of factor VIII was determined. Of the 178 hemophilic patients (mean age, 29 years), TTV-DNA was found in 123 (69%), in comparison to 22 of 100 (22%) blood donors (P <.0001). Of the 123 patients who tested positive for TTV, significant numbers were also infected with human hepatitis viruses and/or human immunodeficiency virus (HIV): 31% had TTV and hepatitis C virus (HCV), 22% had TTV, and at least 2 of the 4 known human blood-borne viruses tested, whereas 15% had TTV alone. The risk of acquiring TTV alone was only slightly higher in recipients of unmodified plasma factor concentrates (78%, odds ratio, 1.24; 95% confidence interval [CI], 0.27 to 5.79) than in patients treated with virus inactivated concentrates (67%), whereas the risk was significantly lower in recipients of recombinant factors (11%, odds ratio, 0.09; 95% CI, 0.01 to 0.52). Serum alanine aminotransferase (ALT) levels were elevated in 2 of 27 patients (7%) with TTV alone compared with 43 of 56 patients (77%) coinfected with TTV and HCV and compared with 16 of 21 patients (76%) with HCV alone. Taken together, these results indicate that TTV frequently infects Italian hemophiliacs treated with plasma-derived factor VIII concentrates, both unmodified and virus-inactivated. Our results do not suggest a causal effect of TTV on chronic liver disease in these patients.
The homeobox genes in the Dlx family are required for differentiation of basal forebrain neurons and craniofacial morphogenesis. Herein, we studied the expression of Dlx-1, Dlx-2, and Dlx-5 RNA and protein in the mouse forebrain from embryonic day 10.5 (E10.5) to E12.5. We provide evidence that Dlx-2 is expressed before Dlx-1, which is expressed before Dlx-5. We also demonstrate that these genes are expressed in the same cells, which may explain why single mutants of the Dlx genes have mild phenotypes. The DLX proteins are localized primarily to the nucleus, although DLX-5 also can be found in the cytoplasm. During development, the fraction of Dlx-positive cells increases in the ventricular zone. Analysis of the distribution of DLX-1 and DLX-2 in M-phase cells suggests that these proteins are distributed symmetrically to daughter cells during mitosis. We propose that DLX-negative cells in the ventricular zone are specified progressively to become DLX-2-expressing cells during neurogenesis; as these cells differentiate, they go on to express DLX-1, DLX-5, and DLX-6. This process appears to be largely the same in all regions of the forebrain that express the Dlx genes. In the basal telencephalon, these DLX-positive cells differentiate into projection neurons of the striatum and pallidum as well as interneurons, some of which migrate to the cerebral cortex and the olfactory bulb.
The respiratory system of a cyanide-resistant Klebsiella oxytoca was analyzed by monitoring the changes in the cytochrome contents in response to various inhibitors in the presence of various concentrations of cyanide. The cells grown in the medium without cyanide (KCN) have two terminal oxidases, cytochrome d (Ki = 10(-5) M KCN) and o (Ki = 10(-3) M KCN). When cells were grown on medium with 1 mM KCN, the expression of both b-type cytochrome and cytochrome d in the plasma membranes of the cell decreased by more than 50%, while cytochrome o increased by 70%, as compared with the cells grown in the absence of KCN. Two terminal oxidases with Ki values of about 10(-3) M and 1.7 x 10(-2) M KCN were observed in the plasma membrane fractions of the cells growing on KCN enriched medium. 2-n-Heptyl-4-hydroxyquinoline-N-oxide markedly inhibited the oxidation of NADH by the plasma membranes from the cells grown in the medium without KCN, but not in those plasma membranes from KCN-grown cells. The NADH oxidases in plasma membranes of K. oxytoca grown with and without KCN were equally sensitive to UV irradiation. Adding freshly isolated quinone to the UV-damaged plasma membranes restored the NADH oxidase activity from both types of plasma membranes. From these results, we propose the presence of a non-heme type of terminal oxidase to account for the KCN resistance in K. oxytoca.
A novel DNA virus designated TT virus (TTV) has been reported to be involved in the development of posttransfusion non-A-C hepatitis. We evaluated the frequency and natural course of TTV infection in a cohort of transfusion-dependent thalassemic patients in a 3-year follow-up study. Ninety-three serum hepatitis C virus (HCV) antibody-negative patients (median age of 8 years; range, 0 to 25) from eight centers were studied. Of them, 34 (37%) had an abnormal alanine-aminotransferase (ALT) baseline pattern, and the other 12 (13%) showed ALT flare-ups during the follow-up. TTV DNA in patient sera collected at the time of enrollment and at the end of follow-up was determined by polymerase chain reaction (PCR). In parallel, serum samples from 100 healthy blood donors were also tested. At baseline, 87 patient sera (93.5%) tested positive for the TTV DNA. Of these TTV DNA-positive patients, 84 (96.5%) remained viremic at the end of the study period. Of the 6 TTV DNA-negative patients, 3 acquired TTV infection during follow-up. However, no definite relation was observed between the results of TTV DNA determination and ALT patterns. TTV viremia was also detectable in 22% of blood donors. In conclusion, TTV infection is frequent and persistent among Italian transfusion-dependent patients. The high rate of viremia observed in healthy donors indicates that the parenteral route is not the only mode of TTV spread.
The piglet displays similar postnatal development in respiration and sleep-wake behavior to the human. To shed light on the possible influence of opioid systems on these functions, this study assessed the density of mu- and delta-opioid receptors in brainstems of 2-3 and 5-7 (young), 14-17 (intermediate) and 20-21 (older) day-old piglets, using quantitative autoradiography. Serial 10 microns sections from fresh-frozen brains were incubated with either mu-(125I-DAGO) or delta-(125I-DPDPE) opioid ligands. The binding characteristics of each receptor remained unchanged over the age-range studied. delta-opioid receptor density was minimal in the young piglets, and increased over the age-range studied in all brainstem regions. mu-opioid receptor density exceeded delta-opioid density in all brainstem regions in young and older piglets, and remained unchanged with age. We conclude that, as in other species, the development of delta-opioid receptors in swine lags behind that of mu-opioid receptors, and that the distribution of each in the piglet's brainstem is distinct. The present findings help explain the changing influence of the mu- and delta-opioid systems on breating and state during postnatal development.
We report the generation and analysis of mice homozygous for a targeted deletion of the Dlx5 homeobox gene. Dlx5 mutant mice have multiple defects in craniofacial structures, including their ears, noses, mandibles and calvaria, and die shortly after birth. A subset (28%) exhibit exencephaly. Ectodermal expression of Dlx5 is required for the development of olfactory and otic placode-derived epithelia and surrounding capsules. The nasal capsules are hypoplastic (e.g. lacking turbinates) and, in most cases, the right side is more severely affected than the left. Dorsal otic vesicle derivatives (e. g. semicircular canals and endolymphatic duct) and the surrounding capsule, are more severely affected than ventral (cochlear) structures. Dlx5 is also required in mandibular arch ectomesenchyme, as the proximal mandibular arch skeleton is dysmorphic. Dlx5 may control craniofacial development in part through the regulation of the goosecoid homeobox gene. goosecoid expression is greatly reduced in Dlx5 mutants, and both goosecoid and Dlx5 mutants share a number of similar craniofacial malformations. Dlx5 may perform a general role in skeletal differentiation, as exemplified by hypomineralization within the calvaria. The distinct focal defects within the branchial arches of the Dlx1, Dlx2 and Dlx5 mutants, along with the nested expression of their RNAs, support a model in which these genes have both redundant and unique functions in the regulation of regional patterning of the craniofacial ectomesenchyme.