PubMed Health⌕ Search

Biomedical subjects

A T Cheung

Publications and source records attributed to A T Cheung.

At least 73 records · Page 4Linked to original sources
PubMed1987

Biliary motility: postnatal changes in guinea pigs.

Intravital microscopy, a new in vivo technique, documented age-dependent changes in choledochoduodenal junction motility in male guinea pigs. In the guinea pig, the choledochoduodenal junction served as a pump that actively emptied its luminal contents into the duodenum. In the neonates (less than or equal to 1 wk old), this choledochoduodenal junction pump was not fully developed. Unlike the older guinea pigs, some neonates had an incompetent sphincter ductus choledochi (SDC) allowing retrograde flow of bile during ampullary contractions. While fasting, neonates had decreased frequency of SDC (1.2 +/- 0.4 contractions/min) and ampullary (0.1 +/- 0.1 contractions/min) contractions as compared to juveniles (4-6 wk old) (SDC = 6.4 +/- 1.0; ampulla = 1.2 +/- 0.2 contractions/min) and adults (greater than 1 yr old) (SDC = 6.7 +/- 1.6; 0.8 +/- 0.2 contractions/min). Following a meal (Ensure), unlike older guinea pigs, the neonate did not have a significant increased duration and decreased frequency of SDC contractions. Altered neonatal SDC motility correlated with an incompletely developed SDC including decreased muscle mass and mucosal thickness. By 4 wk of age, choledochoduodenal junction motility was similar to that of the adult. These developmental alterations in junctional motility and structure may affect the flow of bile into the duodenum contributing to physiologic cholestasis and decreased intraduodenal bile acids seen in neonates.

Animals↗
PubMed1987

Bronchoalveolar lavage in the newborn foal.

Two bronchoalveolar lavages, 24 h apart, were performed on 15 foals, ranging in age from 1 to 21 days. In the first lavage, a numerical deficiency in alveolar macrophages was demonstrated in foals up to 2 weeks of age when compared with older (2-3 years of age) horses. Alveolar macrophages obtained from the lungs of 2-3-day-old foals also demonstrated significant impaired chemotactic function. In the second lavage, although an increase of alveolar macrophages was noted, a dramatic increase of polymorphonuclear neutrophil (PMN) mobilization occurred in the foals, thus providing a phagocytic back-up for the alveolar macrophage host defence mechanism. In contrast, PMN response to lower respiratory tract perturbation in older horses was negligible. The results of this study suggest that the numerical and chemotactic deficiency found in alveolar macrophages of the neonate may play a role in the foal's susceptibility to respiratory disease.

Animals↗
PubMed1986

A quantitative method for the analysis of cell shape and locomotion.

A rapid, semiautomated system to quantitate and analyze leukocyte shape and locomotion was developed. Video images of moving leukocytes were obtained using a Vidicon camera mounted on a Nikon phase microscope. The video signal was either inputted directly, or indirectly via a video cassette recorder, to a Datacube video analog-digital, digital-analog converter. A Digital Equipment Corporation LSI 11/23 computer using the RT-11/TSX-Plus operating system and computer programs written in FORTRAN and MARCO assembly language permitted image segmentation, image display, and calculation of position, speed, direction of movement and orientation of each leukocyte at 10 s intervals. These data were stored on a winchester disk for subsequent evaluation of the leukocyte orientation, speed and direction of movement using statistical and graphical methods. The reproducibility of measurements made with the video system was tested by comparison with manual measurements; a correlation coefficient of 0.998 was obtained for the two methods. Rates of chemokinesis were then determined for unstimulated and chemokinetically stimulated polymorphonuclear leukocytes (PMNs) and found to average 12.8 micron/min and 18.1 micron/min, respectively. The high speed, ease of data analysis, and potential for multiparameter evaluation makes this system useful for directly evaluating leukocyte locomotion.

Cell Movement↗
PubMed1986

The functional competence of uterine-derived polymorphonuclear neutrophils (PMN) from mares resistant and susceptible to chronic uterine infection: a sequential migration analysis.

The functional competence of uterine-derived polymorphonuclear neutrophils (PMNs) from 28 mares was measured for migration responsiveness by use of a chamber (filter) assay. Uterine infection was induced with Streptococcus zooepidemicus in mares considered resistant to chronic uterine infection (Grade I). In sequential analysis of uterine flushings obtained from these mares 5, 12, 15, 20, and 25 h after infection was induced, PMNs showed an initial rise at 12 h (from 5), then a general decline in migration response and in concentration of cells per ml from 12 through 25 h post-inoculation. In contrast, PMNs obtained from the uterine flushings from mares considered susceptible to chronic uterine infection (Grade III) demonstrated premature migration dysfunction 12 h after infection. Subsequent increases in functional competence of the PMNs were demonstrated at 15 and again at 25 h after induced infection. The concentration of uterine PMNs per ml from mares considered susceptible to chronic endometritis remained elevated from 12 through 25 h after inoculation, which suggests a possible continued recruitment of new PMNs from the peripheral circulation. The results of this study suggest that uterine-derived PMNs obtained from mares susceptible to chronic uterine infection have a compromised ability to migrate. This dysfunction may play an important role in rendering the endometrium (uterus) susceptible to chronic endometritis.

Animals↗
PubMed1986

Host defense deficiency in newborn nonhuman primate lungs.

We have investigated two major aspects of the pulmonary host defense mechanism--alveolar macrophage function as a "first line of bacterial defense" and induced neutrophil migration into the lung as a "back-up defense." Chemotactic and phagocytic/killing assays revealed a functional deficiency in the alveolar macrophages of newborn primates. Serial bronchoalveolar lavage investigations revealed diminished neutrophil migration into the newborn primate lung. The overall pulmonary host defense capability in newborn primates was deficient. The results of this investigation may have direct clinical relevance to the susceptibility of newborns to infections and pneumonia.

Animals↗
PubMed1985

Reactivation of tritonated models of human polymorphonuclear leukocytes (PMNs): a computer-assisted analysis.

The orientation (chemotaxis) and locomotion (chemokinesis) of human polymorphonuclear leukocytes (PMNs) are generated by an internal movement mechanism that involves active cytoplasmic movement; they are influenced by external environmental and ionic conditions. We have studied the degree to which the orientation and movement mechanisms of PMNs are self-contained within the cell and the degree to which they are under membrane control. PMNs were partially and selectively demembranated by treatment with the non-ionic detergent, octyl-phenoxyl-polyethoxyethanol (commercially known as Triton X-100) under controlled conditions. The tritonated PMNs (referred to in the literature as models) were non-motile and non-locomotory. Addition of ATP/Mg++ with a trace amount of Ca++ to the medium was followed by reactivation of the tritonated PMN models to move again as motile cells. Although these reactivated PMN models actively locomoted, they could no longer orient to chemoattractants. Thus, the reactivation process restored the physical self-contained movement parameters but could not reestablish the orientation capacity (chemotactic responsiveness) that was characteristic of live PMNs. The demembranation process apparently destroyed the chemotactic receptors and/or eradicated the coordination function of the membrane. Videotapes of normal (control) as well as reactivated PMN movement were analyzed for movement characteristics. These characteristics were objectively analyzed with a newly designed computer-assisted micro-image-processing technique whereby the videotapes were digitized and quantified and the actual PMN movement printed out in computer-graphics and tracings (Freeman codes) for confirmation of orientation and movement arising as a result of reactivation.

Adenosine Triphosphate↗
PubMed1985

Monocyte function in rhesus monkeys with simian acquired immune deficiency syndrome.

Monocyte function in rhesus monkeys with simian acquired immune deficiency syndrome (SAIDS) was compared with that in age-matched normal juvenile rhesus monkeys. The functional tests were 1) chemotaxis, 2) phagocytosis of opsonized Candida albicans, 3) killing and/or growth inhibition of Candida albicans, 4) generation of respiratory burst, and 5) monocyte-derived macrophage response (morphology and/or respiratory burst) to stimulating agents such as lymphokines, gamma interferon, endotoxin, and phorbol myristate acetate. The monkeys tested had either clinical SAIDS (alive with lymphadenopathy, splenomegaly, and lymphopenia or neutropenia) or had terminal SAIDS (moribund due to the disease). Responses of monocytes from 14 monkeys with clinical SAIDS were indistinguishable from those of 9 normal juvenile rhesus monkeys, whereas monocytes from 3 monkeys with terminal SAIDS had enhanced phagocytosis and respiratory burst capacity. Chemotaxis, candidacidal/stasis activity, and response to stimulating agents were normal in these terminal cases. Plasma from the SAIDS monkeys was as capable of opsonizing yeasts and of being able to generate chemotactic factors by endotoxin as was control plasma. SAIDS retrovirus (SRV) was detected by co-cultivation of pure monocyte-derived macrophage cultures with Raji cells, an indicator cell line which forms syncytia in the presence of SRV. Four terminal SAIDS cases and one late-stage clinical SAIDS case were virus-positive when the number of macrophages in the cultures ranged from less than 50 to about 500. Terminal SAIDS monocyte-derived macrophages in culture as long as 17 days produced SRV. These data show that in monkeys with SAIDS the major effector functions of monocytes and macrophages involved in host defense are intact (even up until death). Additionally, some of the monocytes are productively infected, and these infected monocytes are viable and adherent in culture.

Acquired Immunodeficiency Syndrome↗
PubMed1985

Studies of marginal zinc deprivation in rhesus monkeys: VI. Influence on the immunohematology of infants in the first year.

Rhesus monkey infants fed a marginally zinc-deficient diet (4 ppm) from conception through 12 mo of postnatal life were monitored for changes in hematological, biochemical, and immunological parameters. These zinc-deprived (ZD) infants were compared to control infants whose mothers were fed a zinc-replete (100 ppm) diet either ad libitum (AL) or pair-fed (PF) throughout gestation and lactation. Blast transformation of peripheral blood lymphocytes to phytohemagglutinin (PHA-P), concanavalin A (Con A), and pokeweed mitogen (PWM), was dramatically depressed in the zinc-deficient (ZD) group. Similarly, ZD infants had reduced polymorphonuclear leukocyte function as measured by chemotaxis to endotoxin-activated plasma and phagocytosis of Candida albicans. Levels of serum IgM were significantly altered in zinc-deficient infants compared to controls. Serum concentrations of IgG and IgA were similar in zinc-deficient and control infants. ZD infants also manifested a hypochromic microcytic anemia at one month of age, reduced activity of the zinc metalloenzyme alkaline phosphatase, and lower activity of SGPT.

Alkaline Phosphatase↗
PubMed1985

Phagocytic and killing capacities of uterine-derived polymorphonuclear leukocytes from mares resistant and susceptible to chronic endometritis.

The host defense competence of uterine-derived polymorphonuclear leukocytes (PMN) from mares considered resistant (grade I uteri) and susceptible (grade III uteri) to chronic endometritis was evaluated for phagocytic and killing (bactericidal) capacities, using a fluorochrome assay. Peripheral blood PMN from noncategorized mares and from grade I and grade III mares were used as controls. Uterine-derived PMN from mares with grade I uteri were functionally competent for phagocytosis and killing of Candida albicans, whereas uterine-derived PMN from mares with grade III uteri had significantly less phagocytic and killing capacities (P greater than or equal to 0.0001). Results of the present study, together with data obtained from chemotactic responsiveness and deformability assays of a previous study, indicated an overall deficiency in the host defense mechanism of uterine-derived PMN from mares with grade III uteri obtained 12 hours after induced Streptococcus zooepidemicus infection. This deficiency may account for the susceptibility of mares with grade III uteri to chronic endometritis.

Animals↗
PubMed1985

Comparison of peripheral blood and uterine-derived polymorphonuclear leukocytes from mares resistant and susceptible to chronic endometritis: chemotactic and cell elastimetry analysis.

The functional competence of peripheral blood and uterine-derived polymorphonuclear leukocytes (PMN) from 12 mares were analyzed for chemotactic responsiveness using a chemotactic chamber (filter) assay and for deformability by cell elastimetry analysis. Peripheral blood PMN obtained from control mares and from 8 mares experimentally inoculated via the uterus with 1 x 10(9) Streptococcus zooepidemicus had similar normal chemotactic responsiveness and were highly deformable before and at 12 hours after inoculation. Uterine PMN obtained 12 hours after uterine inoculation with S zooepidemicus from resistant mares were not as deformable as peripheral blood PMN, but were within normal functional limits. The chemotactic responsiveness of uterine PMN from these mares was normal. Uterine PMN obtained from mares considered susceptible to endometritis 12 hours after uterine infection did not have chemotactic responsiveness and were nondeformable. The results indicated profound differences in the functional competence of uterine PMN between mares considered resistant and susceptible to chronic endometritis.

Animals↗
PubMed1985

Concanavalin a capping of rhesus monkey polymorphonuclear leukocytes.

The technique of capping, a probe designed to evaluate the fluidity and functional competence of human polymorphonuclear leukocytes (PMNs), has been successfully adapted for rhesus monkey PMNs. The capping characteristics of rhesus monkey PMNs are very similar to those of human PMNs. Utilizing this capping technique as an evaluation tool and with fetal/neonatal rhesus monkey as a functional animal model, the ontogeny of movement and chemotactic characteristics of PMNs can now be studied.

Animals↗
PubMed1984

Kinetics of interaction of N epsilon-fluorescein isothiocyanate-lysine-23-cobra alpha-toxin with the acetylcholine receptor.

We have studied the kinetics of N epsilon-fluorescein isothiocyanate-lysine-23 cobra alpha-toxin (FITC-toxin) binding to the membrane-associated acetylcholine receptor from the Torpedo californica electric organ. The fluorescent toxin not only enabled us to monitor the binding reaction continuously but also to examine simultaneously the enhancement of ligand fluorescence and the increase in steady state polarization of fluorescence associated with binding of the alpha-toxin. Over the range of concentrations employed, both parameters yielded identical kinetic constants, suggesting that the enhancement of fluorescence of fluorescein and its immobilization are occurring in the same time frame. Both an initial rate analysis and the integrated rate expression showed association to be a simple, reversible bimolecular process. The apparent second-order association rate constant derived from the integrated rate analysis was constant within a factor of 2 over a 40-fold concentration range (6.7 +/- 1.7 X 10(3) M-1 S-1). The unimolecular dissociation rate constant was found to be 3.3 +/- 0.5 X 10(-5) S-1.

Animals↗
PubMed1983

Movement of polymorphonuclear leukocytes: an elastimetry analysis.

By utilizing the technique of cell elastimetry, which measures the negative pressure required to aspirate human polymorphonuclear leukocytes (PMNs) into a micropipette, a correlation between PMN deformability and cellular movement is confirmed. The effects of the synthetic chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (f-met-leu-phe) on the deformability and chemotaxis of PMNs have been investigated, and a relationship between peptide concentrations and PMN deformability, which parallels the effects of the peptide on filter (chemotactic) studies, has been established. Experimental evidences indicate that alterations in PMN deformability occur as a natural consequence of stimulation of PMNs with a chemoattractant and that cellular deformation is a prerequisite to PMN movement. Introduction of this analytical technique into the study of PMN movement disorders has already yielded significant insights which implicate a membrane-associated abnormality intrinsic to the impaired motility of neonatal PMNs. This technique can, therefore, serve to provide a sensitive probe with which to dissect the various perturbations of PMN dysfunction. Cell elastimetry can also be utilized to generate quantitative information on mechanical and deformability properties of PMNs; such information is needed for the establishment of a rheological model (for PMNs) which can assist the analysis of almost every functional problem involving PMNs.

Adult↗
PubMed1982

Functional alterations in the membrane of motile polymorphonuclear leukocytes.

We have applied microdocumentary techniques to the study of movement of human PMN's and their behavioral response to a chemoattractant. We discuss here findings which suggest a different interpretation from currently accepted theory. Videotape recordings were made on the movement of human PMN's. A slide modified from previous descriptions was designed to predict a straight-line gradient which could be maintained for periods up to 60 minutes. PMN suspensions were placed on the bridge of the slide with the chemoattractant N-formylmethionylleucyl-phenylalanine (F-Met-Leu-Phe) placed in one wall and PMN suspension medium in the well on the other side of the bridge. Videotapes were traced on the monitor screen at 15-second intervals. A lack of consistent orientation and "head-tail" polarity of any individual PMN was observed. Apparent polarity was observed less than 10% of the time. The net movement of cells in a given field was always toward the direction of the approaching and maintained gradient, but any individual cell failed to show a sustained directional orientation or movement toward the gradient. Individual cells constantly reoriented. Analysis of time-dependent characteristics of the chemotactic response is essential to the ultimate understanding of PMN motility.

Cell Membrane↗