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Biomedical subjects

J T Li

Publications and source records attributed to J T Li.

At least 19 recordsLinked to original sources
PubMed1992

Adsorption behavior of milk proteins on polystyrene latex. A study based on sedimentation field-flow fractionation and dynamic light scattering.

Sedimentation field-flow fractionation (SdFFF) has been used to characterize the adsorption of the proteins beta-casein (BCN) or beta-lactoglobulin (BLG) on colloidal polystyrene latices; this system was used to model hydrophobic interactions between the proteins and the surfaces of fat droplets in protein-stabilized emulsions. It was found that the SdFFF technique could determine directly the surface concentrations of BCN and BLG irreversibly adsorbed to the latex surface, provided care was taken to maintain the ionic strength of the carrier at a level which suppressed particle-wall repulsion in the separation channel. The measured surface concentrations were similar for the two proteins (about 1 mg/m2), and this was verified by quantitative amino acid analysis. These concentrations were smaller than those found in depletion studies (3 and 4 mg/m2 respectively for BCN and BLG), in which loosely associated protein may have been included in the determinations. The thickness of the adsorbed layers was determined in situ by dynamic light scattering and was found to differ significantly for the two proteins (up to 15 nm for BCN vs. 2-3 nm for BLG). The implication of these findings in terms of different surface arrangements of the two proteins is discussed.

Calorimetry↗
PubMed1992

Sequence and complementation analysis of recF genes from Escherichia coli, Salmonella typhimurium, Pseudomonas putida and Bacillus subtilis: evidence for an essential phosphate binding loop.

We have compared the recF genes from Escherichia coli K-12, Salmonella typhimurium, Pseudomonas putida, and Bacillus subtilis at the DNA and amino acid sequence levels. To do this we determined the complete nucleotide sequence of the recF gene from Salmonella typhimurium and we completed the nucleotide sequence of recF gene from Pseudomonas putida begun by Fujita et al. (1). We found that the RecF proteins encoded by these two genes contain respectively 92% and 38% amino acid identity with the E. coli RecF protein. Additionally, we have found that the S. typhimurium and P. putida recF genes will complement an E. coli recF mutant, but the recF gene from Bacillus subtilis [showing about 20% identity with E. coli (2)] will not. Amino acid sequence alignment of the four proteins identified four highly conserved regions. Two of these regions are part of a putative phosphate binding loop. In one region (position 36), we changed the lysine codon (which is essential for ATPase, GTPase and kinase activity in other proteins having this phosphate binding loop) to an arginine codon. We then tested this mutation (recF4101) on a multicopy plasmid for its ability to complement a recF chromosomal mutation and on the E. coli chromosome for its effect on sensitivity to UV irradiation. The strain with recF4101 on its chromosome is as sensitive as a null recF mutant strain. The strain with the plasmid-borne mutant allele is however more UV resistant than the null mutant strain. We conclude that lysine-36 and possibly a phosphate binding loop is essential for full recF activity. Lastly we made two chimeric recF genes by exchanging the amino terminal 48 amino acids of the S. typhimurium and E. coli recF genes. Both chimeras could complement E. coli chromosomal recF mutations.

Amino Acid Sequence↗
PubMed1992

Management of insect sting hypersensitivity.

Approximately 1 to 3% of the general population has had a systemic reaction to insect stings. Adults whose reactions include urticaria, obstruction of the upper or lower airway, or hypotension and children whose reactions include obstruction of the upper or lower airway or hypotension have an increased risk of future systemic reactions to stings. Allergy skin tests to Hymenoptera venoms can help to identify the offending insect and to classify the reactions as allergic; however, because 15% of the general population may have positive results to such tests, persons who have not experienced a systemic reaction to insect stings should not be tested. Venom immunotherapy is highly effective and confers 98 to 99% protection in patients who have experienced previous systemic reactions to insect stings. Reaction rates to venom skin tests or venom immunotherapy are low and are similar to those in allergy testing and immunotherapy for hay fever. Generally, patients who have had systemic reactions to stings should be assessed by an allergist to determine whether they are candidates for immunotherapy with Hymenoptera venom. The decision to institute venom immunotherapy should be based on the disposition of the patient, the severity of the reaction, and the risk of subsequent stings. Deliberate sting challenges are clinically useful for guiding immunotherapy.

Animals↗
PubMed1992

Purification of beta-lactamases and enzyme kinetic studies on aztreonam.

Standard beta-lactamases K1, P99, TEM-1, SHV-1 and beta-lactamase K-CAZ purified using FPLC through ion-exchange chromatography and filtration chromatography, were identified by determination of isoelectric points, molecular weights and substrate profiles. The results showed that the beta-lactamase stability of domestic aztreonam was very similar to that of cefotaxime, ceftazidime and much better than that of cefoperazone. Aztreonam showed a high affinity to chromosomal-mediated cephalosporinase P99, its Ki for inhibition of P99 with cephaloridine as substrate was 0.0159 microns. Aztreonam and the three third generation cephalosporins tested were not stable to beta-lactamase K-CAZ, which hydrolysed them in different degrees.

Aztreonam↗
PubMed1992

Refractory periorbital edema in a 29-year-old man.

A 29-year-old man developed periorbital edema which was initially diagnosed as angioedema. Further clinical investigation by orbital CT and orbital biopsy showed this to be orbital pseudotumor. Immunofluorescence staining for major basic protein clearly demonstrated tissue eosinophilia and extracellular major basic protein deposition. Orbital pseudotumor can mimic angioedema or allergic rhinoconjunctivitis and should be familiar to allergists and primary care physicians. The demonstration of striking extracellular major basic protein in biopsy specimen implicates a role for eosinophils in the pathogenesis of this disease.

Adult↗
PubMed1992

Pemirolast, a new oral nonbronchodilator drug for chronic asthma.

Pemirolast is a new oral, nonbronchodilator antiallergy medication that is being evaluated for the therapy of asthma. In this multicenter, double-blind, randomized study, 96 patients with mild asthma received pemirolast, 50 mg (n = 34); pemirolast, 25 mg (n = 31); or placebo (n = 31) BID for 6 weeks. Patients were evaluated weekly at the research centers; they maintained daily symptom diaries and measured peak expiratory flow rates twice a day. Methacholine challenge was performed at the start and end of the study. Results with pemirolast, 50 mg BID, showed statistically significant decrease in nocturnal symptoms (P = .02), in composite symptom scores (P = .02) and in bronchodilator use (P = .05) when compared with placebo. There were no statistically significant differences between treatments in pulmonary function tests or in methacholine challenge sensitivity. Pemirolast, 25 mg BID, did not differ from placebo. There were no significant adverse effects. Pemirolast, 50 mg BID, demonstrated sufficient antiasthma activity to warrant further studies in patients with more severe asthma and with higher doses.

Administration, Oral↗
PubMed1991

The stability of mesna in beverages and syrup for oral administration.

We evaluated the stability of the aqueous formulation of mesna during storage in syringes and after dilution in beverages and syrups. Measurements of the concentrations of mesna showed that the undiluted formulation was stable for at least 9 days in standard polypropylene syringes at 5 degrees, 24 degrees, and 35 degrees C. There was no detectable oxidation of mesna to dimesna over the course of at least 1 week when mesna was diluted 1:2 and 1:5 in syrups and incubated at 24 degrees C in capped tubes. Concentration changes were clinically negligible for 1:2, 1:10, and 1:100 dilutions of mesna in six carbonated drinks, two juices, and milk after incubation for 24 h at 5 degrees C. Thus, the aqueous mesna formulation is stable when diluted and stored in a variety of beverages and syrups under conditions suitable for oral administration.

Administration, Oral↗
PubMed1991

Source of the aeroallergen of soybean dust: a low molecular mass glycopeptide from the soybean tela.

Airborne soybean allergens in the dust generated during the unloading of soybeans in the harbor caused asthma epidemics in Barcelona, Spain. The major allergen causing the epidemics was a glycopeptide less than 14 kd molecular mass abundant in soybean dust. This allergen occurs in all parts of the soybean plant at all stages of growth, but the telae (hulls) and pods are by far the richest source. Small amounts of a similar cross-reacting allergen are found in some other grain dusts. The botanical function and significance of this soybean plant component is not known nor is the potential for airborne dispersion of this allergen at other grain-handling sites.

Air Pollution↗
PubMed1991

Tissue eosinophilia and eosinophil degranulation in orbital pseudotumor.

To investigate the participation of the eosinophil in orbital pseudotumor, the authors studied surgical biopsy specimens from nine patients with pseudotumor. Surgical biopsy specimens of orbital tissue from four patients with Graves' ophthalmopathy and autopsy specimens of orbital tissue from six patients without orbital diseases served as controls. Eosinophil infiltration and degranulation were assessed by immunofluorescence staining of formalin-fixed, paraffin-embedded tissues for the cytotoxic eosinophil granule major basic protein. Eosinophil infiltration and extracellular major basic protein deposition were evident in all orbital pseudotumor specimens. In contrast, no eosinophil infiltration or extracellular major basic protein deposition was present in any of the ten control specimens. These findings indicate that eosinophil degranulation is found in orbital pseudotumor, and they also identify yet another clinical entity where eosinophil infiltration and degranulation are associated with fibrosis.

Adolescent↗
PubMed1991

A novel perspective on medical education.

Participants on a course entitled 'Planning and Evaluating a Course' generated a theoretical framework to simplify consideration of the essential components of clinically skilled behaviour. Five superordinate facets were elucidated and elaborated with reference to specific teaching situations. This paper illustrates the effective use of buzz-groups to encourage active participation of individual group members. The exercise revealed some serious shortcomings in the current teaching of clinical skills.

Clinical Competence↗
PubMed1990

Lack of suppression of IgE production by recombinant interferon gamma: a controlled trial in patients with allergic rhinitis.

Recent evidence suggests that interferon-gamma (IFN-gamma) is a potent inhibitor of IgE synthesis in rodents. We conducted a randomized, placebo-controlled, two-period clinical trial of human recombinant IFN-gamma in the treatment of allergic rhinitis. Forty-five adults with well-documented ragweed-allergic rhinitis were randomized into three groups of 15 adults each and received subcutaneous injections three times weekly. The first treatment period (4 weeks during the off season) began on April 18, 1988; the second treatment period (6 weeks during ragweed pollination) began on August 15, 1988. All subjects received the same treatment in both periods. Group 1 received 0.2 mg per injection of IFN, group 2 received 0.02 mg of IFN, and group 3 received placebo. One subject in group 1 and three subjects in group 2 withdrew because of adverse reactions, and three subjects withdrew for personal reasons. There were no significant differences in mean weekly symptom scores or supplemental medication scores among the three groups in either treatment period. Furthermore, there were no significant differences in the changes of serum IgE antibody to crude ragweed extract or in serum total IgE among the three groups during or before the ragweed-pollination season. These results indicate that this treatment regimen with IFN-gamma does not alter IgE production in patients with ragweed hay fever and indicate the need for further clinical research of lymphokine modulation of IgE production.

Adolescent↗
PubMed1989

Proper use of aerosol corticosteroids to control asthma.

Aerosol glucocorticoids are highly effective in the treatment of bronchial asthma. Clinically apparent systemic hypercortisolism is virtually nonexistent in patients who receive such therapy, although local effects of candidiasis or dysphonia may occur. Treatment failures can often be attributed to poor patient compliance or incorrect use of the pressurized aerosol inhaler. The addition of a spacer device to the inhaler improves the technique and the results in many patients. Furthermore, many patients with asthma require 2 or 3 times the conventional dose of aerosol corticosteroids for optimal control of pulmonary function. Careful coaching is essential for the successful use of aerosol corticosteroids.

Administration, Inhalation↗
PubMed1989

[Affinity of penicillin-binding proteins of Escherichia coli K-12 for furbenicillin and other beta-lactam antibiotics].

Penicillin-binding proteins (PBP) are vitally important targets in relation to the killing of bacteria by beta-lactams. The affinities of PBP of Escherichia coli K 12 for ampicillin, mecillinam and for ureidopenicillins were studied by sodium dodecylsulphate polyacrylamide slab gel electrophoresis and fluorography. The results showed that furbenicillin, a semisynthetic ureidopenicillin developed in China, bound to all 3 essential target proteins of E coli. The IC50 values of furbenicillin to PBP 1 b, PBP 2 and PBP 3 were 4.55 mg/L, 0.37 mg/L and 0.06 mg/L, respectively. The affinities of the 3 proteins of E coli for furbenicillin were 2.5-, 3.5-, and 2.5-fold, respectively higher than that of azlocillin. Mecillinam bound exclusively to PBP 2 (IC50: 0.16 mg/L). Mezlocillin and piperacillin showed higher affinities for PBP 3 than furbenicillin, but their affinities for PBP 1 b and PBP 2 were much lower than furbenicillin.

Anti-Bacterial Agents↗
PubMed1989

Five steps toward better asthma management.

The primary goal of asthma management is to eliminate all of the symptoms and maintain normal pulmonary function with the safest medical program. Important management issues, which are often overlooked, include identification and management of respiratory allergy to dust mites, pets and occupational exposures; appropriate (sparing) use of antibiotics; proper dosing and instruction in the use of aerosol corticosteroids; recognition and management of nocturnal asthma, and continuing assessment of the severity of asthma by measuring and monitoring pulmonary function. Adherence to these and other principles of management will help achieve the goal of symptom-free asthma.

Adrenal Cortex Hormones↗
PubMed1988

Nocturnal asthma: approach to the patient.

Nocturnal asthma can be diagnosed by asking patients whether they awaken at night with asthmatic symptoms and feel the need to use an aerosol bronchodilator. The primary objective in treating nocturnal asthma is to help patients sleep through the night. The bronchoconstriction that underlies nocturnal asthmatic symptoms is a reflection of bronchial hyperresponsiveness, and this hyperresponsiveness is greatly increased by airway inflammation. In patients with allergic asthma, airway inflammation can be reduced by reducing exposure to allergens and, in some cases, by immunotherapy. Nocturnal bronchoconstriction is best controlled by scheduling sustained-release bronchodilators, particularly theophylline, to provide the maximal theophylline blood concentration at the time of maximal obstruction, usually between 4:00 and 6:00 A.M.

Asthma↗