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Biomedical subjects

J Luo

Publications and source records attributed to J Luo.

At least 253 records · Page 14Linked to original sources
PubMed1997

Placental abnormalities in mouse embryos lacking the orphan nuclear receptor ERR-beta.

Classical endocrine studies have shown that steroid hormones are required for the maintenance of pregnancy and placental viability. The oestrogen-receptor-related receptor beta (ERR-beta) is an orphan member of the superfamily of nuclear hormone receptors. Although ERR-beta is homologous to the oestrogen receptor and binds the oestrogen response element, it is not activated by oestrogens. Expression of ERR-beta during embryogenesis defines a subset of extra-embryonic ectoderm that subsequently forms the dome of the chorion, suggesting that ERR-beta may be involved in early placental development. Homozygous mutant embryos generated by targeted disruption of the Estrrb gene have severely impaired placental formation, and die at 10.5 days post-coitum. The mutants display abnormal chorion development associated with an overabundance of trophoblast giant cells and a severe deficiency of diploid trophoblast. The phenotype can be rescued by aggregation of Estrrb mutant embryos with tetraploid wild-type cells, which contribute exclusively to extra-embryonic tissues. Our results indicate that ERR-beta has an important role in early placentation, and suggest that an inductive signal originating from or modified by the chorion is required for normal trophoblast proliferation and differentiation.

Animals↗
PubMed1997

Perturbation of the antigen-binding site and staphylococcal protein A-binding site of IgG before significant changes in global conformation during denaturation: an equilibrium study.

Although conformational perturbation of the active sites of many enzymes has been reported to precede global molecular conformational changes [Tsou (1993) Science 262, 380-381], little effort has been made to compare the susceptibility of the ligand-binding site of proteins and the protein molecules as a whole to perturbation by denaturants. Immunoglobulin is chosen in this study to address this problem. It is found that the variable and constant regions (Fv and Fc) of a monoclonal antibody of an IgG subclass against adenylate kinase lose their abilities to bind antigen and staphylococcal Protein A after treatment with guanidinium chloride concentrations considerably lower than those required to change the global conformation of the antibody as a whole, as detected by fluorescence and second-derivative UV absorption spectroscopy. These results indicate that both ligand-binding sites of the antibody concerned are more fragile than the molecule as a whole and that the Fv and Fc regions of the antibody molecule unfold sequentially during denaturation.

Antigens↗
PubMed1997

The Union Health Center: a working model of clinical care linked to preventive occupational health services.

As health care provision in the United States shifts to primary care settings, it is vital that new models of occupational health services be developed that link clinical care to prevention. The model program described in this paper was developed at the Union Health Center (UHC), a comprehensive health care center supported by the International Ladies Garment Workers Union (now the Union of Needletrades, Industrial and Textile Employees) serving a population of approximately 50,000 primarily minority, female garment workers in New York City. The objective of this paper is to describe a model occupational medicine program in a union-based comprehensive health center linking accessible clinical care with primary and secondary disease prevention efforts. To assess the presence of symptoms suggestive of occupational disease, a health status questionnaire was administered to female workers attending the UHC for routine health maintenance. Based on the results of this survey, an occupational medicine clinic was developed that integrated direct clinical care with worker and employer education and workplace hazard abatement. To assess the success of this new approach, selected cases of sentinel health events were tracked and a chart review was conducted after 3 years of clinic operation. Prior to initiation of the occupational medicine clinic, 64% (648) of the workers surveyed reported symptoms indicative of occupational illnesses. However, only 42 (4%) reported having been told by a physician that they had an occupational illness and only 4 (.4%) reported having field a workers' compensation claim for an occupational disease. In the occupational medicine clinic established at the UHC, a health and safety specialist acts as a case manager, coordinating worker and employer education as well as workplace hazard abatement focused on disease prevention, ensuring that every case of occupational disease is treated as a potential sentinel health event. As examples of the success of this approach, index cases of rotator cuff tendonitis, lead poisoning, and formaldehyde overexposure in three patients and their preventative workplace follow-up, affecting approximately 150 workers at three worksites, are described. Work-related conditions diagnosed during the first 3 years of clinic operation included cumulative trauma disorders (141 cases), carpal tunnel syndrome (47 cases), low back disorders (33 cases), lead poisoning (20 cases), and respiratory disease (9 cases). This pilot project represents a new model for effective integration of clinical care and occupational disease prevention efforts within a primary care center. It could serve as a prototype for development of such services in other managed and primary care settings.

Ambulatory Care Facilities↗
PubMed1997

Study of respirator effect on nasal-oral flow partition.

Factors affecting worker tolerance of respiratory personal protective devices are inadequately understood. This study evaluates whether respirator-type loads affected the switch from nasal to oral breathing. Eleven healthy subjects were studied under progressive exercise conditions, using a respirator full-face mask with inspiratory resistance (I), pressure breathing (P) (10 cm H2O end-expiratory pressure), or no load (N). A rapid-response thermistor was used to determine whether flow was predominantly oral or nasal. Both P and I increased the percentage of time that breathing was predominantly oral. The effect was most pronounced at higher exercise levels. The percentage of mouth breathing appeared to be closely related to the expiratory time. This study suggests that nasal-oral flow partitioning should be considered as a possible determinant of respirator tolerance.

Adult↗
PubMed1997

The effect of denaturants on protein structure.

Virtually all studies of the protein-folding reaction add either heat, acid, or a chemical denaturant to an aqueous protein solution in order to perturb the protein structure. When chemical denaturants are used, very high concentrations are usually necessary to observe any change in protein structure. In a solution with such high denaturant concentrations, both the structure of the protein and the structure of the solvent around the protein can be altered. X-ray crystallography is the obvious experimental technique to probe both types of changes. In this paper, we report the crystal structures of dihydrofolate reductase with urea and of ribonuclease A with guanidinium chloride. These two classic denaturants have similar effects on the native structure of the protein. The most important change that occurs is a reduction in the overall thermal factor. These structures offer a molecular explanation for the reduction in mobility. Although the reduction is observed only with the native enzyme in the crystal, a similar decrease in mobility has also been observed in the unfolded state in solution (Makhatadze G, Privalov PL. 1992. Protein interactions with urea and guanidinium chloride: A calorimetric study.

Crystallography, X-Ray↗
PubMed1997

Cattle theileriosis in China.

Amongst the piroplasmoses of livestock in China, the commonest theilerioses are caused by Theileria annulata, T. sergenti and T. mutans. Research carried out over many years has shown these to be distributed mainly in Northern China but they also occur in Southern China. T. annulata and T. sergenti are the most troublesome, affecting large numbers of cattle, especially those of exotic breeds. The incident rate and numbers of fatalities vary widely between areas and breeds of cattle. T. annulata is the most virulent species having an incident rate of 11-46% for indigeneous cattle and causing death rates of between 11-40.8%. For exotic cattle in areas free of T. annulata the sickness rate is up to 61% and mortality rates up to 31%. T. sergenti is avirulent in cattle and clinical symptoms are rarely observed, however, in some areas the infection rate could possibly be as high as 97.5%. Dairy and hybrid cattle imported from other places proved highly susceptible, with mortality rates possibly reaching 14%. The pathogenic forms, clinical signs, tick vectors and the effects of chemical and immune intervention are also discussed in this paper.

Animals↗
PubMed1997

Theileriosis of sheep and goats in China.

Theileriosis is an important disease of sheep and goats in West China. Its main distribution includes Qinghai, Gansu, Ningxia, Inner Mongolia, Shaanxi and Sichuan. The epidemic period is from late March to July with April-May being the peak months. This is the period of most intensive tick attack by Haemaphysalis qinghaiensis (77.2-99.24%) during the year. It has been proved that the nymphs and adults, which develop from larvae and nymphs engorged on infected sheep or goats can transmit the pathogen. Experimental infections revealed the incubation period, clinical signs and the pathogen's morphological characteristics. The disease was more serious in lambs and exotic adult animals than native adult animals. The sickness rates of lambs, exotic and native adult animals were 78-85%, 41% and 9% respectively; death rates were 81.41%, 62.5% and 65% respectively. Clinical prophylaxis, chemical therapy and destruction of ticks have been carried out with antiparasitic compounds to control the disease since 1982. Experiments demonstrated that the curative rate was up to 76-86%, but no satisfactory prophylactic methods were found.

Animals↗
PubMed1997

Babesiosis in China.

The importance of babesiosis in livestock in China is discussed and mainly focused on bovine and equine babesiosis. Babesiosis is still one of the most important diseases affecting livestock and has caused great economic loss. Nine species of Babesia have been recognized in livestock: B. bigemina, B. bovis, B. major, B. motasi, B. ovis, B. perroncitoi, B. trautmanni, B. equi (Theileria equi), B. caballi. The distribution of Babesia follows the distribution of the tick vectors. The main vectors of bovine babesiosis are the one-host tick Boophilus microplus and the three-host ticks Rhipicephalus haemaphysaloides haemaphysaloides, Haemaphysalis punctata and Haemaphysalis longicornis. Bovine babesiosis has caused significant losses in milk and meat from cattle in most parts of China. The disease is also a barrier to improving productivity of local cattle by cross-breeding due to the high mortality of genetically superior but highly susceptible cattle, especially dairy cattle, imported from Babesia-free areas. Dermacentor nuttalli is the major vector of equine babesiosis and the tick is distributed in almost all parts of North China. Outbreaks of equine babesiosis have not been very common, but in some districts the disease has seriously affected horses, donkeys and mules.

Animals↗
PubMed1997

Attempted transmission of Babesia major by Boophilus microplus.

Two experiments was carried out to determine if Babesia major could be transmitted by Boophilus microplus. In experiment 1, a Babesia-free batch of laboratory reared Bo. microplus larvae were applied to an intact calf infected by inoculation with a B. major stabilate. The calf showed a B. major parasitaemia while the larvae, nymphs and adult ticks were engorging. The engorged females were cultured and batches were incubated at one of the three following temperatures: 24, 28 or 32 degrees C. Approximately 10,000 larvae derived from each of the females were used to infest each of three splenectomized calves. In experiment 2, Babesia-free Bo. microplus larvae were applied to a splenectomized calf; the calf was injected with B. major stabilate and showed a B. major parasitaemia during the adult stage of tick development. The engorged females were incubated at room temperature and the resulting larvae (approximately 10,000) were used to infest a splenectomized calf. Examination of blood films for the presence of B. major from the four calves infested by the second generation larvae in the two experiments were negative.

Animals↗
PubMed1997

Analysis of urinary and faecal porphyrin excretion patterns in human porphyrias by fast atom bombardment mass spectrometry.

We report a new method for obtaining urinary and faecal porphyrin excretion patterns in human porphyrias based on fast atom bombardment mass spectrometry (FAB-MS). Porphyrins were esterified and extracted from urine or faeces as their methyl esters for analysis by FAB-MS. The protonated pseudo-molecular ion [M + H]+ observed for each porphyrin is characteristic of that porphyrin, thus allowing a mixture of porphyrins to be analysed without the need for chromatographic separation. By using tandem MS, identification and characterisation of unknown porphyrins can be achieved. The urinary and faecal porphyrin excretion patterns from various porphyric patients obtained by FAB-MS are in good agreement with those analysed by TLC or HPLC methods.

Feces↗
PubMed1997

Constitutive expression of the HTLV-I pX and env regions in Jurkat T-cells induces differential activation of SRE, CRE and NF kappa B pathways.

Human T-cell leukemia virus type I (HTLV-I) causes adult T-cell leukemia/lymphoma (ATLL). HTLV Tax, the viral transcriptional activator, can activate a variety of cellular genes. HTLV-mediated T-cell transformation, however, may involve additional viral proteins expressed from singly- as well as doubly-spliced viral mRNA. To determine the combined effect of these viral proteins on cellular gene expression in Jurkat T-cells, we derived stable transfectants that constitutively express the HTLV-I pX and env regions (J3.9). J3.9 cells show substantially increased mRNA levels of egr-1 and c-jun but no induction of either CD25 or GM-CSF by Northern blotting. This pattern corresponded to the activation of an egr-1 but not a GM-CSF promoter-driven reporter construct in transient gene expression assays. In DNA electrophoretic mobility shift assays (EMSA), nuclear extract from J3.9 cells has significantly increased binding to CRE and SRE but not nuclear factor kappa B (NF kappa B) DNA oligos, as compared to J-Neo cell extract. These results suggest that low level expression of pX and env region gene products in Jurkat T-cells stimulates persistent activation of CRE- and SRE- but not NF kappa B-induced cellular genes.

Cyclic AMP Response Element-Binding Protein↗
PubMed1997

Determination of lignocaine hydrochloride by ion-pairing flow injection with piezoelectric detection.

A rapid and simple method for the determination of lignocaine hydrochloride by ion-pairing flow injection analysis was developed. It is based on the formation of an ion pair between lignocaine hydrochloride and sodium dodecyl phenylsulfonate and piezoelectric detection. The calibration curve was linear between 0.01 and 2.00 mg ml-1, with a detection limit of 8 micrograms ml-1, an RSD of 0.29% (10 replicates) and a sampling frequency of 120 h-1. The proposed method was satisfactorily applied to the determination of lignocaine hydrochloride in pharmaceutical preparations.

Flow Injection Analysis↗
PubMed1997

The majority of N-methyl-D-aspartate receptor complexes in adult rat cerebral cortex contain at least three different subunits (NR1/NR2A/NR2B).

A monoclonal antibody (R1JHL) against the NR1 subunit of the N-methyl-D-aspartate (NMDA) receptor has been developed that recognizes an epitope in the region of the amino-terminal amino acids 341-561 (a region common to all splice variants of NR1). This monoclonal antibody identifies a broad band at 115 kDa in immunoblots using membranes from NR1-transfected cells and from rat brain tissue. No cross-reactivity with any NR2 subunit is seen. With the goal to determine quantitatively the subunit composition of cortical NMDA receptors, we used the monoclonal antibody to NR1 and polyclonal antibodies against the NR2A and NR2B subunits to perform immunoprecipitations of receptor subunits from solubilized adult rat cortical membranes. Solubilization of the receptor subunits was accomplished under both nondenaturing (native) conditions, under which the subunits seem to remain associated with one another, and denaturing conditions, under which the subunits are associated from each other. Although each of these antibodies selectively immunoprecipitates only its corresponding (cognate) subunit when the subunits have been solubilized under denaturing conditions, each of the antibodies immunoprecipitates a sizable fraction of the other two NMDA receptor subunits when membranes are solubilized under nondenaturing conditions, indicating an interaction in situ. Using quantitative immunoblot analysis of the three subunits in both the pellets and supernatants from the immunoprecipitations, we found 1) the dominant NMDA receptor complex in adult rat cortex contains at least three subunits, NR1/NR2A/NR2B; 2) a smaller fraction of NMDA receptors are composed of only two subunits, NR1/NR2B or NR1/NR2A; 3) there are no complexes that contain NR2A/NR2B that do not contain NR1; 4) only a small fraction of each subunit is not associated with any other NMDA receptor subunit; 5) no coimmunoprecipitation of noncognate subunits occurs unless the subunits are assembled with each other in situ; and 6) there is no physical interaction between these NMDA receptor subunits and the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor GluR2 or GluR3 subunits. These results suggest that functional studies with recombinant receptors composed of at least three subunits may be the most physiologically meaningful.

Animals↗
PubMed1997

Compartment-selective sensitivity of cardiovascular morphogenesis to combinations of retinoic acid receptor gene mutations.

Several aspects of normal cardiovascular development require signaling by the vitamin A metabolite retinoic acid. We have previously established germ-line mutations in mice in the genes that encode the RAR alpha 1, RAR beta, and RXR alpha retinoic acid receptors as a means of studying the function of these receptors in vivo. Although mutation of RXR alpha results in fetal ventricular defects, the RAR alpha 1 and RAR beta mutations are apparently nonphenotypic in the heart and elsewhere. In this study, we have established and analyzed combinations of these receptor gene mutations. Malformations of the ventricular chamber (chamber hypoplasia and muscular ventricular septal defects), conotruncus (double-outlet right ventricle, transposition, and membranous ventricular septal defects), aortic sac (persistent truncus arteriosus and aorticopulmonary window), and aortic arch-derived arteries were recovered in various combinations of the RAR alpha 1, RAR beta, and RXR alpha gene mutations. Depending on the combination of receptor mutations, selective defects were obtained in specific cardiovascular compartments, suggestive of differential expression or function of each receptor within domains of the developing heart.

Animals↗
PubMed1997

Clinical observations on 278 cases of cervical spondylopathy treated with electroacupuncture and massotherapy.

From Dec. 1990 to Dec. 1993, 278 cases of cervical spondylopathy were treated with electroacupuncture and massotherapy. The cure rate was 82.7%; but in the control group, it was only 61%, indicating that electroacupuncture may enhance the cure rate (P < 0.05). Of the 278 cases treated by three to five sessions, the pain and numbness disappeared in about 96% of the patients.

Acupuncture Therapy↗
PubMed1997

[Clinical experience in the treatment of chronic radiation ulcer in 32 cases].

A retrospective study was carried out, aiming at a proper treatment to the chronic radiation ulcer that is often difficult to deal with. Thirty-two cases of chronic radiation ulcer have been treated in the department since 1983. The cause, site, features and method of treatment were summarized. Thirty-one cases were cured, 26 cases healed by the first intention, 5 cases healed by the second intention. One died. It is emphasized that more knowledge should be gained for understanding and treatment of the chronic radiation ulcer. Different methods of debridement and repair should be performed according to the site, depth and pathologic features of the ulcer. To improve local circulation, an island flap is the first choice of treatment.

Breast Neoplasms↗
PubMed1997

[Experimental study of prostacyclin on the survival of random skin flaps].

The purpose of this experiment was to observe the effect of PGI2 on the survival of the random skin flap. White rats used in the experiment were divided into preoperation (prevention) group, postoperation (treatment) group and the control group. A super-long random skin flap was created on the back of the animal. Postoperatively, the treatment group received intravenous injection of PGI2 while the control group received intravenous injection of normal saline. The blood supply, metabolism and hemorheology of the flap were analyzed. Results showed that the relative blood flow on the distal part of the flap was 41.3% in the treatment group and 22.4% in the control group. The survival rate of the flap of the treatment group was higher than that of the control. There were no differences between the prevention and the control groups. It is concluded that early postoperative injection of PGI2 could improve blood supply and rheology of the flap and increase its survival rate.

Animals↗