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Biomedical subjects

P Chang

Publications and source records attributed to P Chang.

At least 199 records · Page 11Linked to original sources
PubMed1993

Tyrosine phosphorylation is required for Fc receptor-mediated phagocytosis in mouse macrophages.

Although Fc receptor-mediated phagocytosis is accompanied by a variety of transmembrane signaling events, not all signaling events are required for particle ingestion. For example, Fc receptor-mediated phagocytosis in mouse inflammatory macrophages (Di Virgilio, F., B. C. Meyer, S. Greenberg, and S. C. Silverstein. 1988. J. Cell Biol. 106:657; Greenberg, S., J. El Khoury, F. Di Virgilio, and S. C. Silverstein. 1991. J. Cell Biol. 113:757) and neutrophils (Della Bianca, V., M. Grzeskowiak, and F. Rossi. 1990. J. Immunol. 144:1411) occurs in the absence of cytosolic calcium transients. We sought to identify transmembrane signaling events that are essential for phagocytosis. Here we show that tyrosine phosphorylation is an early event after Fc receptor ligation in mouse inflammatory macrophages, and that the formation of tyrosine phosphoproteins coincides temporally with the appearance of F-actin beneath phagocytic cups. The distribution of tyrosine phosphoproteins that accumulated beneath phagocytic cups was punctate and corresponded to areas of high ligand density on the surface of the antibody-coated red blood cells, which provided the phagocytic stimulus. A tyrosine kinase inhibitor, genistein, but not several inhibitors of protein kinase C, blocked the appearance of tyrosine phosphoproteins as assessed by immunofluorescence, the focal accumulation of F-actin beneath immunoglobulin G-opsonized particles, and the ingestion of these particles as well. We suggest that tyrosine phosphorylation is a critical signaling event that underlies Fc receptor-mediated phagocytosis in mouse macrophages, and is necessary for the engulfment per se.

Actins↗
PubMed1993

Perfluorochemical reperfusion yields improved myocardial recovery after global ischemia.

Reperfusion injury remains a limiting factor in extending ischemic storage time for human heart transplantation. In this study, initial myocardial reperfusion with an oxygenated perfluorochemical (Fluosol) was investigated as a means of limiting such injury. Neonatal piglet hearts were arrested with crystalloid cardioplegia, excised, and stored for 12 hours in saline solution at 0 degrees C. Initial reperfusion (10 minutes) was either with whole blood (n = 6), unmodified perfluorochemical (n = 8), or aspartate/glutamate-enriched perfluorochemical cardioplegia (n = 6), and was followed by an additional 40 minutes of whole blood perfusion. Functional evaluation was then completed, and left ventricular biopsy specimens were taken. A control group (n = 7) was evaluated without an intervening period of ischemia. At a left ventricular end-diastolic pressure of 9 mm Hg, hearts stored in whole blood cardioplegia developed a left-ventricular stroke work index of 3.8 +/- 2.3 x 10(3) erg/g (mean +/- standard error of the mean). Under the same conditions, perfluorochemical-reperfused hearts achieved a stroke work index of 14.6 +/- 1.3 x 10(3) erg/g, significantly greater than that of the whole blood group (p < 0.001). Stroke work index for hearts reperfused with aspartate/glutamate-enriched perfluorochemical cardioplegia was 19.8 +/- 1.6 x 10(3) erg/g, significantly increased over that of the nonenriched perfluorochemical group (p < 0.01) and not different from values obtained in controls (19.2 +/- 0.8 x 10(3) erg/g).(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1993

Acquired perforating disease: report of nine cases.

BACKGROUND: A study of nine Guatemalan patients with acquired perforating disease associated with chronic renal failure, diagnosed at the Guatemalan Social Security Institute, General Hospital, during the period of January 1990 to March 1993, is presented (Table 1). METHODS: A dermatological examination and skin biopsy were done on all patients. RESULTS: Six of the patients were men and three were women; one case was associated with diabetes mellitus. Three of the patients were diagnosed as Kyrle-like acquired perforating disease, and the other six as perforating folliculitis. The lesions were predominantly located in the lower extremities with hyperkeratotic papules and nodules; some of these were accompanied by pruritus and Koebner's phenomenon. CONCLUSION: The acquired perforating disease is a clinical cutaneous manifestation of chronic renal failure with or without treatment. The lesions can disappear spontaneously with stabilization of the renal damage.

Adult↗
PubMed1993

Effects of sham and real auricular needling: implications for trials of acupuncture for cocaine addiction.

We conducted a single-blind study (n = 48) comparing subjective evaluations of needles inserted into sham and real auricular acupuncture points. Both ears were needled concurrently, one in sham sites and the other in active points used in the treatment of cocaine addiction. Subjects then completed a questionnaire rating the intensity of five sensations in each ear, and also attempted to identify which ear received sham and which ear received real acupuncture. Results showed that real points were more painful than sham; there were no other overall differences. Subjects' ability to identify which ear received sham and which ear received real acupuncture did not rise above the level of chance.

Acupuncture Points↗
PubMed1993

Effects of smoked substance abuse on nonspecific airway hyperresponsiveness.

Previous data suggest that regular tobacco smoking may lead to nonspecific airway hyperresponsiveness (AHR) independent of airway obstruction, possibly because of effects on bronchial inflammation or mucosal permeability. Little is known concerning the effects on AHR of other widely smoked substances besides tobacco such as marijuana or cocaine. The smoke of both marijuana and cocaine contains respiratory irritants that elicit cough and produce abnormalities in airway dynamics and bronchial mucosal histopathology in habitual smokers. Therefore, regular smoking of one or both of these illicit substances could cause AHR or augment the AHR associated with tobacco smoking. The present study examined the influence of habitual smoking of marijuana, cocaine, and/or tobacco on nonspecific AHR in 542 (456 male) healthy participants (mean age, 34.8 +/- 6.8 SD yr) in an ongoing cohort study of the pulmonary effects of habitual smoking of illicit substances. Subjects with a history of intravenous drug abuse, significant occupational exposures, asthma, or recent upper respiratory tract infection were excluded. Inhalation challenge studies were performed using solutions of diluent and methacholine chloride (1.25 to 25 mg/ml) aerosolized by a DeVilbiss no. 646 nebulizer attached to a breath-activated dosimeter inhaled by three to five inspiratory capacity breaths. Positive responses to methacholine were defined by > or = 20% or > or = 10% declines in FEV1 from the postdiluent control value after inhalation of each concentration of methacholine. Participants were categorized by smoking status (nonsmoking and smoking of marijuana, cocaine, and/or tobacco alone and in combination); most analyses were performed in men and women separately.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Comparison of the results of spinal fusion for spondylolisthesis in patients who are instrumented with patients who are not.

Eighty-five patients who had surgery for spondylolisthesis were studied retrospectively both clinically and radiologically to determine if instrumentation lead to better fusion rates and clinical outcome. Degenerative spondylolisthesis accounted for 57 cases and patients who had instrumentation did have a better fusion rate and clinical outcome, with 60% of patients having complete relief from pain. In the group with isthmic spondylolisthesis (28 patients), there was also an improved fusion rate with instrumentation. However, these patient took a longer time before returning to work and had to be protected in a polythene brace. The improved fusion rate radiologically with instrumentation did not translate to better clinical results with regard to pain relief and disability. One patient developed ascending epidural haematoma with instrumentation and resulted in paraplegia. She had incomplete recovery during the follow-up.

Absenteeism↗
PubMed1993

Normocalcemic blood or crystalloid cardioplegia provides better neonatal myocardial protection than does low-calcium cardioplegia.

Although standard blood cardioplegia provides good myocardial protection for cardiac operations in adults, protection of the cyanotic, immature myocardium remains suboptimal. Calcium, which has been implicated in reperfusion injury and in the development of "stone heart" in mature myocardium, is routinely lowered in standard cardioplegic solutions. Immature, neonatal myocardium has lower intracellular calcium stores and is more reliant on extracellular calcium for contraction. To determine if normocalcemic cardioplegia would result in improved cardiac function in the neonatal heart, we conducted a series of experiments using an isolated, blood-perfused working heart model. Thirty-two neonatal piglet hearts (24 to 48 hours) were excised without intervening ischemia and were placed directly on a blood-perfused circuit. Baseline stroke work index was assessed. Hearts were then arrested with cold cardioplegic solution delivered at 45 mm Hg for 2 minutes: group I, low-calcium blood cardioplegic solution (Ca = 0.6 mmol/L); group II, normal-calcium blood cardioplegic solution (Ca = 1.1 mmol/L); group III, University of Wisconsin solution; and group IV, University of Wisconsin solution with added calcium (Ca = 1.0 mmol/L). Cardioplegic solution was administered every 20 minutes for 2 hours and topical hypothermia was used. Hearts were then reperfused with warm whole blood. Functional recovery, expressed as a percentage of control stroke work index, was determined minutes after reperfusion. Hearts preserved with normocalcemic cardioplegic solution (groups II and IV) had complete functional recovery at 60 minutes, whereas hearts preserved with low-calcium cardioplegic solution (groups I and III) achieved functional recoveries of only 80% and 65%, respectively, at a left atrial pressure of 9 mm Hg. Electron micrographs taken 1 hour after reperfusion showed minimal edema and only mild myofibrillar changes. They were identical in both the low-calcium and normocalcemic groups. Complete functional recovery is possible in immature myocardium when calcium is added to either blood or an intracellular crystalloid cardioplegic solution. The addition of calcium does not result in ultrastructural damage and does result in good functional recovery.

Adenosine Triphosphate↗
PubMed1993

[Ventilation tube insertion for treating adult otitis media with effusion].

The etiologic factors and treatment of otitis media with effusion (OME) in children are well described and established. On the contrary, little has been published with regard to OME in adults and its treatment. To further investigate this problem, we reviewed the records of all adult patients who had received ventilation tube (VT) insertion for OME in VGH-Taipei from 1983 to 1986. There were 335 VT insertions performed on 140 adult patients whose follow-up periods were longer than 6 months. Among them, fifty patients received more than one VT insertion due to recurrence of OME in one or both ears. The average follow-up period was more than 4 years. The coexistence of nasal diseases was found in 46% of the adult OME patients. The mean extrusion time of the VT was 10.2 months. After VT insertions, the improvements of mean air conduction and mean air-bone conduction gap were 10.1 and 11.8 dB respectively. After the extrusion or removal of VT, there was no recurrence of OME in 50 ears (14.9%). Recurrence of OME occurred in 199 ears (59.4%). Dry persistent perforations of the eardrums were found in 27 ears (8.1%). Discharging persistent perforations were noted in 24 ears (7.2%). No recurrence of OME was observed in 24.2% of the ears with serous effusion fluids, whereas only 4.8% of the ears with mucoid fluids were free from recurrence during the follow-up period. Post-intubation otorrhea, which was the most common complication, developed in 92 ears (27.5%). Our results suggest that the recurrence rate of OME after extrusion of VT is high in the adult patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1993

The microvascular distribution of cardioplegic solution in the piglet heart. Retrograde versus antegrade delivery.

The uniform distribution of cardioplegic solution to all areas of the microvasculature is considered critical for myocardial protection. Despite this, little information exists regarding the ability of retrogradely infused cardioplegic solution to perfuse the microvasculature of the heart. In this report, the microvascular distribution of retrogradely delivered cardioplegic solution was studied by means of a technique to quantitatively demonstrate capillary perfusion. Duroc piglet hearts were subjected to either antegrade (n = 4) or retrograde (n = 8) perfusion fixation with 2.5% glutaraldehyde and subsequently perfused with NTB-2 (an intracapillary marker). The results indicate that retrogradely delivered NTB-2 consistently perfused the anterior half of the intraventricular septum and the anterior and lateral free walls of the left ventricle but inconsistently perfused the posterior half of the intraventricular septum, the posterior wall of the left ventricle, and a small paraseptal region of the right ventricle. The remainder of the right ventricle was not perfused. In contradistinction, all regions of the heart were consistently perfused by the antegrade technique. In regions of the heart in which retrograde microvascular perfusion occurred, no statistical difference was found in the quantitative degree of capillary perfusion achieved by either the antegrade or retrograde technique. These results have important implications for planning strategies of myocardial protection and suggest that further investigation concerning the microvascular distribution of retrogradely delivered cardioplegic solution in human beings is merited.

Animals↗
PubMed1992

Synthesis and structure-activity relationships of 7-diazabicycloalkylquinolones, including danofloxacin, a new quinolone antibacterial agent for veterinary medicine.

A series of novel 6-fluoro-7-diazabicycloalkylquinolonecarboxylic acids substituted with various C8 (H, F, Cl, N) and N1 (ethyl, cyclopropyl, vinyl, 2-fluoroethyl, 4-fluorophenyl, 2,4-difluorophenyl) substituents, as well as, 9-fluoro-10-diazabicycloalkylpyridobenzoxazinecarboxylic acids, were prepared and evaluated for antibacterial activity against a range of important veterinary pathogenic bacteria. The diazabicycloalkyl side chains investigated at the 7-position (benzoxazine 10-position) include (1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]heptane (2), (1S,4S)-2,5-diazabicyclo[2.2.1]heptane (3), (1R,4R)-5-methyl-2,5-diazabicyclo[2.2.1]heptane (4), 8-methyl-3,8-diazabicyclo[3.2.1]octane (5), 9-methyl-3,9-diazabicyclo[4.2.1]nonane (6), 1,4-diazabicyclo[3.2.2]nonane (7), 1,4-diazabicyclo[3.3.1]nonane (8), and 9-methyl-3,9-diazabicyclo[3.3.1]nonane (9). Among these side chains, in vitro potency was not highly variable; other properties therefore proved more critical to the selection of possible development candidates. However, the relative potencies observed for several of these compounds in mouse, swine, and cattle infection models correlated well with those seen in vitro. A combination of the N1 cyclopropyl group and the C7 (1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1]hept-2-yl appendage conferred the best overall antibacterial, physiochemical, and pharmacodynamic properties. Hence, danofloxacin (Advocin, 2c) (originally CP-76,136, 1-cyclopropyl-6-fluoro-7-[(1S,4S)-5-methyl-2,5-diazabicyclo[2.2.1] hept-2-yl]-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid) was selected as a candidate for development as a therapeutic antibacterial agent for veterinary medicine.

Actinobacillus Infections↗