Biomedical subjects

L Li

Publications and source records attributed to L Li.

At least 1,621 records · Page 90Linked to original sources

PubMed1994

Importance of the ATP-binding domain and nucleolar localization domain of HSP72 in the protection of nuclear proteins against heat-induced aggregation.

Heat treatment of cells results in an increased protein content of nuclei when isolated after the heat treatment (intranuclear protein aggregation). In a previous study, the role of HSP72 was investigated using Rat-1 fibroblasts stably transfected with the human HSP72 gene. It was observed that the expression of human HSP72 in Rat-1 cells (HR cells) confers heat resistance. The initial heat-induced increase in the nuclear protein content was lower in HR cells as compared to the parent Rat-1 cells. In the present communication, the effects of overexpression of intact or mutant human HSP72 in Rat-1 cells on heat-induced increase in intranuclear protein aggregation and their relationship to cells' thermal sensitivity were examined. Four closely related cell lines were used for this study: Rat-1 cells which constitutively expressed the intact human HSP72, or mutant human HSP72 either missing its ATP-binding domain or nucleolar localization domain, and wild type Rat-1 cells. Our results show that expression of the intact human HSP72 or mutant human HSP72 missing its ATP-binding domain confers heat resistance and protects cells against heat-induced intranuclear protein aggregation. On the other hand, cells expressing mutant human HSP72 missing its nucleolar localization domain demonstrated heat shock responses similar to control Rat-1 cells.

Adaptation, Biological↗

PubMed1994

Implantation of PNS graft inhibits the induction of neuronal nitric oxide synthase and enhances the survival of spinal motoneurons following root avulsion.

In a spinal root injury model, our previous studies have shown that induction of nitric oxide synthase (NOS) appears only in spinal motoneurons of the root-avulsed segment in which significant motoneuron loss occurs but not in those of the distal root-axotomized segment (root axotomy 5-10 mm from the spinal cord) in which most motoneurons survive the injury. One hypothesis for the different response of motoneurons to root avulsion and distal root axotomy is that neurotrophic factors produced by the remaining peripheral nervous system (PNS) component are available for the distally axotomized motoneurons but are not available following avulsion. This hypothesis is tested in the present study by implantation of a PNS graft following the root avulsion. Results of the present study show that implantation of a PNS graft significantly enhances the survival of motoneurons following avulsion. Expression of NOS due to avulsion injury is completely inhibited in all motoneurons that regrow into the PNS graft. These results indicate that induction of NOS in avulsed motoneurons may result from the deprivation of neurotrophic factors produced by the PNS component, and the survival promoting effects of neurotrophic factors may be achieved by modifying certain cellular molecules such as NOS.

Amino Acid Oxidoreductases↗

PubMed1994

Expression of mouse metallothionein-I gene confers cadmium resistance in transgenic tobacco plants.

Transgenic tobacco plants containing a mouse metallothionein-I (MT-I) gene fused to the cauliflower mosaic virus 35S (CaMV 35S) promoter and nopaline synthase (nos) polyadenylation site were obtained by transforming tobacco leaf discs with an Agrobacterium tumefaciens strain carrying the chimaeric gene. Transformants were directly selected and rooted on medium containing cadmium and kanamycin. A total of 49 individual transgenic tobacco plants were regenerated. Among them 20% showed a very high expression level and their growth was unaffected by up to 200 microM cadmium, whereas the growth of control plants was severely affected leaf chlorosis occurred on medium containing only 10 microM cadmium. The concentration of microM cadmium. The concentration of MT-I in leaves of control and transgenic tobacco was determined with Cd/haemoglobin saturation assay, a polarographic method and western blotting. In addition, seeds from self-fertilized transgenic plants were germinated on medium containing toxic levels of cadmium and scored for tolerance/susceptibility to this heavy metal. The ratio of tolerant to susceptible plants was 3:1 indicating that the metallothionein gene is inherited as a single locus.

Agrobacterium tumefaciens↗

PubMed1994

Alpha-domain of human metallothionein IA can bind to metals in transgenic tobacco plants.

With a view to exploring its use as a metal-binding factor in transgenic plants we prepared the alpha-domain of metallothionein by reconstitution of rabbit apometallothionein and proteolysis of MT-1 and MT-2 with subtilisin. The isolated alpha-domains were characterised by UV and CD spectroscopy Double-Stranded. DNA encoding the alpha-domain (106 bp) of the human MT-IA was constructed from chemically synthesized oligomers by repair synthesis and enzymatic ligation, cloned into pUC19 and sequenced. A expression construct containing the cloned alpha-domain was introduced into tobacco cells on a disarmed Agrobacterium tumefaciens Ti-plasmid. Transformed tobacco cells were selected and regenerated on medium containing cadmium and kanamycin. The growth of roots and shoots of transformants was unaffected by up to 100 microM cadmium, whereas control plants showed severe inhibition of root and shoot growth, and chlorosis of leaves on medium containing only 10 microM cadmium. Southern hybridization confirmed the presence of the transgene in the transformed plant tissues. The concentration of human alpha-domain peptides in transgenic tobacco leaves was determined by the Cd/hemoglobin saturation assay and polarography using the rabbit alpha-domain as standard. The results indicate that the alpha-domain, one of two domains in MT molecules, is not only stable in vitro, but is also expressed efficiently and functions independently in transgenic plant cells.

Agrobacterium tumefaciens↗

PubMed1994

A novel radioligand binding assay to determine diagnostic accuracy of isoform-specific glutamic acid decarboxylase antibodies in childhood IDDM.

Insulin-dependent diabetes mellitus (IDDM) is associated with autoreactivity against GAD but the diagnostic sensitivity (positivity in disease) and specificity (negativity in health) of isoform-specific GAD antibodies have yet to be defined in assay systems suitable for screening large number of samples. One set of IDDM patient (n = 10) and control (n = 50) standard sera were used to develop quantitative antibody assays with in vitro synthesized recombinant 35S-methionine-labelled GAD65 and GAD67, respectively, and protein A-Sepharose to separate free from antibody-bound ligand. Binding levels were not normally distributed (p < 0.0001) and therefore, the diagnostic accuracy of GAD antibodies was analysed by the ROC plots in population-based, consecutively-diagnosed, recent onset, 0-14 year-old patients (n = 105), and matched, healthy control subjects (n = 157). The ROC plots showed that the diagnostic sensitivity of GAD65 antibodies was 77% and the specificity 92% compared with 8% and 98%, respectively for GAD67 antibodies. In the IDDM sera, GAD65 and GAD67 antibodies were concordant in 7% (6 of 81) and GAD65 antibodies and ICA in 89% (72 of 81) without a correlation between the autoantibody levels. Autoantibodies to recombinant human islet GAD65 are specific and sensitive markers for childhood IDDM in this immunoassay with in vitro synthesized 35S-methionine-labelled recombinant GAD.

Adolescent↗

PubMed1994

The induction of specific antitumor immunity by in vivo treatment with interleukin-1 and sonicated tumor extract in a murine model.

BALB/c mice were pretreated intraperitoneally with interleukin-1 (IL-1) and sonicated tumor extract (SE) from plasmacytoma MOPC104E, 10, 7, and 4 days prior to the intraperitoneal or subcutaneous inoculation of MOPC104E cells, following which significant suppression was observed. The mean survival time and tumor diameter on day 21 were 46.7 days and 0 mm, respectively, in contrast to the 20.9 days and 20.4 mm of control mice. Mice pretreated with IL-1 and SE from MOPC104E (MOPC-SE) were not suppressed following fibrosarcoma MethA inoculation, which indicates the tumor specificity of immunity in this model. This systemically operating antitumor immunity was also achieved by the intramuscular administration of IL-1, or when tumor challenge was performed on day 7 or 14. Moreover, MOPC104E-specific delayed-type hypersensitivity was detected in these mice. The results of this study suggest the possibilities of a new type of active specific immunotherapy, which could prove useful as postsurgical adjuvant therapy for cancer patients.

Animals↗

PubMed1994

Clinical application of SPECT to the localization of corticoepileptogenic focus of intractable epilepsy.

This paper presented 51 cases of intractable epilepsy, of which 36 were males, and 15 females, with a mean age of 21. They were all verified through CT/MRI, among which 17 were proved to have lesions on the brain, and 34 to have no lesion. Before operation all the patients were identified by SPECT and cerebral blood flow imaging (CBF). During the operation they were monitored under subdural strip electrode ECoG for the localization of corticoepileptogenic focus. The results showed that the sensitivity rate of localization with SPECT for corticoepileptogenic focus location was 97.87%.

Adolescent↗

PubMed1994

Correlation of proteolytic activities of organ cultured intact mouse skin with defined hair cycle stages.

The cyclic growth activity of the hair follicle is characterized by substantial remodelling of the extracellular matrix, yet, little is known about the proteolytic activities regulating this process. In murine skin, hair cycling is highly synchronized and is associated with dramatic remodeling of all skin compartments. We therefore have assessed, in this pilot study, proteolytic activities of murine skin from various stages of the depilation-induced hair cycle. We show that the defined proteolytic activities displayed by organ cultured intact mouse skin differ between hair cycle stages. Skin with all follicles in telogen or mid anagen displayed only minimal lysis of collagen type I gels, while early anagen skin had significant collagenase activity. Skin cultured on gelatin gels at the air-liquid interphase ('histoculture') completely lysed the gel within 5 days when all follicles were in early anagen, while this was not observed with mid and very late-anagen skin. Zymography of conditioned medium from these cultures revealed the secretion of activated interstitial collagenase and of gelatinases of 72 and 92 kDa, with the maximum of interstitial collagenase activity secreted by anagen IV skin. Addition of TPA or TNF-alpha to the culture medium stimulated secreted collagenase type I activity. The C 57 BL-6 mouse offers an attractive model for dissecting and manipulating hair cycle-associated proteolysis in a physiologically relevant system.

Animals↗

PubMed1994

Study of natural diamonds by dynamic nuclear polarization-enhanced 13C nuclear magnetic resonance spectroscopy.

The results of a study of two types of natural-diamond crystals by dynamic nuclear polarization (DNP)-enhanced high-resolution solid-state 13C nuclear magnetic resonance (NMR) are reported. The home-built DNP magic-angle spinning (MAS) 13C NMR spectrometer operates at 54 GHz for electrons and 20.2 MHz for carbons. The power of the microwave source was about 30 W and the highest DNP enhancement factor came near to 10(3). It was shown that in the MAS spectra the 13C NMR linewidths of the Ib-type diamond were broader than those of IaB3-type diamond. From the hyperfine structure of the DNP enhancement as a function of frequency, four kinds of nitrogen-centred and one kind of carbon-centred free radicals could be identified in the Ib-type diamond. The hyperfine structures of the DNP enhancement curve that originated from the anisotropic hyperfine interaction between electron and nuclei could be partially averaged out by MAS. The 13C polarization time of DNP was rather long, i.e. 1500 s, and the spin-lattice relaxation time (without microwave irradiation) was about 300 s, which was somewhat shorter than anticipated. Discussions on these experimental results have been made in this report.

Diamond↗

PubMed1994

Mutations in the M4 domain of Torpedo californica acetylcholine receptor dramatically alter ion channel function.

Site-directed mutagenesis was used to mutate alpha Cys418 and beta Cys447 in the M4 domain of Torpedo californica acetylcholine receptor expressed in Xenopus laevis oocytes. The M4 region is a transmembrane domain thought to be located at the lipid-protein interface. By whole-cell voltage clamp analysis, mutation of both alpha subunits to alpha Trp418 increased maximal channel activity approximately threefold, increased the desensitization rate compared with wild-type receptor, and shifted the EC50 for acetylcholine from 32 microM to 13 microM. Patch measurements of single-channel currents revealed that the alpha Trp418 increased channel open times approximately 28-fold at 13 degrees C with no effect on channel conductance. All of our measured functional changes in the alpha Trp418 mutant are consistent with a simple kinetic model of the acetylcholine receptor in which only the channel closing rate is altered by the mutation. Our results show that changes in protein structure at the putative lipid-protein interface can dramatically affect receptor function.

Acetylcholine↗

PubMed1994

Naturally occurring and axotomy-induced motoneuron death and its prevention by neurotrophic agents: a comparison between chick and mouse.

Neuronal cell death is an important regressive event during the normal development of the peripheral and central nervous systems of many vertebrate and invertebrate species. Furthermore, when neurons are deprived of their target following axonal injury (axotomy) during embryonic, fetal, or early postnatal development, they undergo massive cell death. Both naturally occurring and axotomy-induced neuronal cell death can be prevented by treatment with growth factors or neurotrophic agents. Naturally occurring cell death of spinal MNs has been extensively studied in both avians and mammals. However, compared with mammals, there is little information on the effects of axotomy in avian species and it is not known whether trophic agents can modify axotomy-induced death in avian MNs. It is also not known whether trophic/growth factors can promote the in vivo survival of mammalian MNs during the period of naturally occurring cell death. We have examined (1) the time course of axotomy-induced death of lumbar spinal MNs in chick and mouse, and (2) the survival-promoting activity of a number of previously characterized growth and trophic factors on both programmed and axotomy-induced MN death in these two species. We show that axotomy performed on, or prior to, E12 in the chick results in a rapid decrease (i.e. 50%) in MN numbers within 3-4 days postsurgery, whereas these cells were able to survive for up to 1 week following axotomy on E14. By contrast, mouse MNs remained vulnerable to axotomy for at least 5 days after birth.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Effects of chronic and acute cocaine treatment on the onset of maternal behavior and aggression in Sprague-Dawley rats.

Pregnant rats were treated either throughout gestation (GD 1-20) with 30 mg/kg per day (chronic cocaine) or with one 15-mg/kg dose immediately following parturition (acute cocaine). Chronic and acute cocaine treatment delayed or diminished the postpartum onset of some components of maternal behavior, and chronically treated dams were significantly more aggressive toward a male intruder than acute cocaine-treated or saline-treated dams. Cocaine increased the latency to crouch over pups and decreased crouch duration during a 30-min observation period that immediately followed parturition. Latencies to nest build were also longer in more chronic cocaine-treated dams than in saline controls. On Day 6 postpartum, 83% of chronic cocaine-treated dams pinned and attacked an intruder male 8 or more times during a 10-min observation period, whereas only 4% of acute cocaine-treated and none of the saline-treated dams exhibited this much aggression.

Aggression↗

PubMed1994

A genetic linkage map of the bovine genome.

A cattle genetic linkage map was constructed which marks about 90% of the expected length of the cattle genome. Over 200 DNA polymorphisms were genotyped in cattle families which comprise 295 individuals in full sibling pedigrees. One hundred and seventy-one loci were found linked to one other locus. Twenty nine of the 30 chromosome pairs are represented by at least one of the 36 linkage groups. Less than a 50 cM difference was found in the male and female genetic maps. The conserved loci on this map show as many differences in gene order compared to humans as is found between humans and mice. The conservation is consistent with the patterns of karyotypic evolution found in the rodents, primates and artiodactyls. This map will be important for localizing quantitative trait loci and provides a basis for further mapping.

Animals↗

PubMed1994

Application of a rapid assay for detection of antibodies to human immunodeficiency virus in urine.

The use of rapid, simple tests to detect antibodies to human immunodeficiency virus (HIV) in urine could be valuable for several testing situations, such as in private offices, for epidemiologic surveys, and in developing countries. The authors evaluated the performance of the SUDS HIV type 1 test to detect antibody to HIV-1 peptides in urine. Test performance and applicability of the SUDS test were compared with a routine Food and Drug Administration-licensed enzyme-linked immunosorbent assay (ELISA) and Western blot using 139 serum and urine pairs collected from autopsy cases. Using a modified procedure when testing urine by the SUDS test, results indicated that a total of 15 serum/urine pairs were HIV-1 antibody positive by both the SUDS test and ELISA; all could be confirmed positive by Western blot. One sample produced discrepant results. The SUDS test produced no false-positive results when testing serum or urine, as compared with ELISA, and no false-negative results when compared with the Western blot. For optimal accuracy of detection of antibodies using urine, at least 100 microL of sample was required. By Western blot analysis, antibody profiles in urine were generally weaker than in serum, but confirmation of positivity was not compromised when larger volumes were used. The authors concluded that this rapid HIV-1 test, when used to detect antibodies to HIV-1 in urine, is accurate, easy to perform, and appropriate for use in certain testing situations.

Blotting, Western↗

PubMed1994

Intronic gene conversion in the evolution of human X-linked color vision genes.

Human red and green visual pigment genes are X-linked duplicate genes. To study their evolutionary history, introns 2 and 4 (1,987 and 1,552 bp, respectively) of human red and green pigment genes were sequenced. Surprisingly, we found that intron 4 sequences of these two genes are identical and that the intron 2 sequences differ by only 0.3%. The low divergences are unexpected because the duplication event producing the two genes is believed to have occurred before the separation of the human and Old World monkey (OWM) lineages. Indeed, the divergences in the two introns are significantly lower than both the synonymous divergence (3.2% +/- 1.1%) and the nonsynonymous divergence (2.0% +/- 0.5%) in the coding sequences (exons 1-6). A comparison of partial sequences of exons 4 and 5 of human and OWM red and green pigment genes supports the hypothesis that the gene duplication occurred before the human-OWM split. In conclusion, the high similarities in the two intron sequences might be due to very recent gene conversion, probably during evolution of the human lineage.

Animals↗

PubMed1994

The investigation of fatal falls and jumps from heights in Maryland (1987-1992).

This study is a retrospective analysis of 139 cases of falls and/or jumps from heights, examined at the Office of the Chief Medical Examiner for the State of Maryland during the 6-year period from 1987 through 1992. A total of 56 individuals (40%) committed suicide by jumping from heights and 72 (52%) fell accidentally. Of the 72 accidental falls, 36 (50%) were work related. Two cases involved victims of homicide and the causes in nine cases remain undetermined. Of the 139 cases examined, 89 individuals (64%) fell or jumped from buildings, 29 (21%) from bridges, 15 (11%) from ladders, and 6 (4%) from trees or electric poles. Of the 29 individuals who fell or jumped from bridges, 14 went into water. Falls and jumps most often involved whites (78%) and males (82%). Their ages ranged from 4 to 83 years, with the majority in their 20s and 30s. Of the 124 people who fell or jumped from heights and landed on the ground, the head was the most frequently injured body region (70%), followed by the chest (66%), the abdomen (48%), extremities (28%), and the neck (19%). Of the 124 victims who landed on the ground, 63 sustained lethal injuries involving multiple organs. In contrast with ground impacts, water impact injuries were much less severe. Five of the 14 victims who jumped from bridges into water were relatively uninjured and died from drowning even though they jumped from heights of 100-200 feet (30-60 m).(ABSTRACT TRUNCATED AT 250 WORDS)

Accidental Falls↗

PubMed1994

Functional state of the beta cell affects expression of both forms of glutamic acid decarboxylase.

Glutamic acid decarboxylase (GAD) is a candidate target autoantigen involved in the pathogenesis of insulin-dependent diabetes mellitus (IDDM). The functional state of the beta cells has been suggested to play a pathogenic role in IDDM by altering beta-cell autoantigen expression. In this study, we investigated expression of GAD-65 and GAD-67 in isolated Sprague-Dawley rat islets cultured at different glucose concentrations. Using GAD isoform-specific antibodies in an immunoblot assay, we found that expression of both GAD-65 and GAD-67 in cultured islets was glucose dependent and that increased expression of both forms of GAD correlated with increased functional state of the beta cell. Our data indicate that the functional state of the beta cell influences islet cell expression of GAD. Thus, decreasing islet cell expression of GAD by suppressing beta cells activity may have a potential role in blunting the autoimmune destruction of pancreatic islet beta cells.

Animals↗

PubMed1994

Characterization of Eubacterium coprostanoligenes sp. nov., a cholesterol-reducing anaerobe.

A small, anaerobic, gram-positive coccobacillus that reduces cholesterol to coprostanol was isolated from a hog sewage lagoon. This isolate, strain HLT (T = type strain) does not require cholesterol for growth, but it requires lecithin and has phospholipase activity. Much acid is produced by the fermentation of amygdalin, lactose, and salicin. Arabinose, cellobiose, fructose, glucose, mannose, and melibiose are fermented weakly. Acetic, formic, and succinic acids are produced, as is hydrogen. The isolate does not reduce nitrate, produce indole, or hydrolyze starch and gelatin. Esculin is hydrolyzed. The properties of strain HLT are most similar to those of members of the genus Eubacterium. Because strain HL (= ATCC 51222) has unique morphological and physiological properties, we propose that it should be the type strain of a new species in the genus Eubacterium, Eubacterium coprostanoligenes.

Anaerobiosis↗