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A T Cheung

Publications and source records attributed to A T Cheung.

82 records · Page 5Linked to original sources
PubMed1981

Chemotactic factor-induced effects upon deformability of human polymorphonuclear leukocytes.

We have compared the effects of the synthetic chemotactic peptide, N-formyl-methionyl-leucyl-phenylalanine (f-Met-Leu-Phe), on the deformability and chemotaxis of human polymorphonuclear leukocytes (PMNs). By utilizing the technique of cell elastimetry (deformability), which measures the negative pressure required to aspirate cells into a micropipet, we have shown a correlation between f-Met-Leu-Phe concentrations and PMN deformability which parallels the effects of that chemoattractant on filter chemotaxis. At concentrations as low as 10(-11) M, a change in the deformability characteristics of a population of neutrophils was demonstrated. The increase in deformability became most marked at peptide concentrations in the range of 1-5 x 10(-9) M, corresponding to the optimal concentration range in the filter chemotaxis assay. Concentrations of 10(-8) M and greater were associated with a significant increase in the negative pressure required to aspirate the cells into a micropipet. Alterations in PMN deformability, therefore, occur as a natural consequence of stimulation of a human PMN with a chemotactic factor and may be a prerequisite to efficient movement.

Cell Movement↗
PubMed1981

Reduced concanavalin A capping of neonatal polymorphonuclear leukocytes (PMNs).

Neonatal polymorphonuclear leukocytes (PMNs) have previously been shown to be chemotactically deficient. To probe the mechanism(s) responsible for this deficiency, we have investigated the phenomenon of concanavalin A-induced capping in neonatal PMNs. PMNs from cord blood of 17 healthy, full-term infants and 17 normal adult volunteers were isolated by standard Ficoll-Hypaque and dextran sedimentation. After incubation with and without colchicine, the cells were reincubated with fluorescein isothiocyanate-Con A, fixed, and prepared in wet mounts. Using a fluorescence microscope, PMNs were identified, and percentage of the capped cells was counted. Upon treatment with colchicine, adult PMNs showed a significant increase in the percentage of capped cells. By contrast, the cord blood PMNs showed no significant increase in capping after colchicine treatment. The difference between percentage of PMNs showing colchicine-induced capping in adult and cord blood was highly significant (P less than 0.01; Student's t test).

Adult↗
PubMed1978

Pillotinas and hollandinas: distribution and behaviour of large spirochaetes symbiotic in termites.

Pillotina spirochaetes have been observed in the hindguts of wood-eating cockroaches (Cryptocercus punctulatus), and in 25 out of 28 species of termites examined. They were especially abundant in 21 species of dry wood termites of the family Kalotermitidae, from Europe, North America and Australia. These included many species of Kalotermes and one or a few of the following: Glyptotermes, Bifidotermes, Neotermes, Ceratokalotermes, Paraneotermes, Cryptotermes, Porotermes, Marginitermes, Pterotermes, Zootermopsis, Reticulitermes, Coptotermes, Heterotermes, and nasutitermitids. Identifications of pillotinas were made on the basis of large size (0.5--2 micromtere in diameter, 50 to greater than 100 micrometers in length) and wave pattern; these were verified by electron microscopy in K. schwarzi, Pterotermes occidentis and others. Pillotinas were also present in all species of subterranean termites (Family Rhinotermitidae) examined, and in the most primitive Australian termite, Mastotermes darwiniensis (Family Mastotermitidae). They were not observed in damp wood termites (Family Hodotermidiae). Pillotinas are invariably associated with a rich, complex xylophagous microbial community composed primarily of motile prokaryotes, and hypermastigote and polymastigote flagellates. Some have been previously described by those primarily concerned with termite hindgut protozoa. Observations were made on their modes of behaviour, division, and microbial associates. A new genus of spirochaetes, Hollandina, is also described. It is distinguished from Pillotina by a smaller size and several ultrastructural features, but is otherwise closely related taxonomically. Evidence is provided to support Hollande and Gharagozlou's (1967) concept that the pillotinas and hollandinas deserve the taxonomic status of 'family' and that they should be classified with the cristispire siprochaetes a-cording to the scheme developed by Hovind-Hougen (1976). Spirochaetes are treated as a Phylum of the Kingdom Monera (Prokaryota) in the five kingdom system of Whittaker (1969).

Animals↗
PubMed1976

High speed cinemicrographic studies on rabbit tracheal (ciliated) epithelia: determination of the beat pattern of tracheal cilia.

High speed cinemicrographs reveal that the ciliary configuration and beat pattern of rabbit tracheal cilia differ significantly from classid descriptions, although the basic forward and return pattern is still observed. The tracheal cilia are short and stout (about 6 mum in length) and are of a slightly bent original configuration bent original configuration. At the start of the forward stroke, the cilia bear about 75-90 degrees to the epithelial surface in the direction of the forward stroke. The forward stroke is planar and consists of a simple "bowing" movement, without showing any progressive bending and without changing the original ciliary configuration. The complete forward stroke sweeps through an arc of about 35-40 degrees, with the tips of the cilia penetrating the bottom of the mucous layer through an arc of about 5-8 degrees at the start of each forward stroke. The return stroke starts from close to the epithelial surface and returns to the starting position of the forward stroke by reversing the planer forward pathway at a reduced speed. The stout nature of the cilia, the original bent ciliary configuration, the near vertical starting position of the forward stroke, the extent of the angular sweeps of the strokes, the peculiar "bowing" forward stroke movement, and the nature of the return stroke all serve to enhance efficiency in moving fluid forward. It has been documented that each forward stroke of the tracheal cilia caused and maintains a swift forward movement of the intermediate serous (liquid) layer of the mucociliary system. This movement, in turn, reacts hydrodynamically with the top mucous layer, and together with the clawing action of the tips of the cilia at the start of the forward stroke, causes the mucous layer to move cephalad in the manner of a conveyor belt.

Animals↗
PubMed1976

High speed cinemicrographic studies on rabbit tracheal (ciliated) epithelia: cytolytic effect of cystic fibrosis serum on tracheal epithelial cells.

High speed cinemicrographs are made on the ciliary activity of rabbit tracheal cilia with the aid of Nomarski optics. The detailed nature of the ciliary beat pattern is determined from slow motion analysis of the high speed cinemicrographs (1-3). Such documented forms of ciliary beat pattern and the physiologic state of the tracheal epithelia are utilized as basic reference controls to investigate the physiologic effects of cystic fibrosis serum on ciliated epithelia and the cystic fibrosis tracheal mucus stagnation phenomenon. Careful analyses of the high speed cinemicrographs reveal that cystic fibrosis serum has no effect on the rhythm and beat pattern of rabbit tracheal cilia. However, it is shown in controlled procedures that cystic fibrosis serum has a cytolytic effect on the tracheal epithelial cells and also at the cell junctions. Ciliary dyskinesis, as described in previous reports (6-9), is actually a secondary effect of cytolysis and cell destruction.

Animals↗
PubMedDate not supplied

Effect of implanted insulin pumps on fluorescein transcapillary escape time in type 1 diabetes mellitus.

OBJECTIVE: To determine whether significant increases in fluorescein transcapillary escape time (FTET) would occur after treatment of patients with type 1 diabetes with insulin delivered intraperitoneally by a surgically implanted pump. METHODS: Nine patients with type 1 diabetes who were otherwise healthy and had received surgically implanted insulin pumps on a study protocol were recruited to have three measurements of FTET and glycosylated hemoglobin during an 18-month period. Serum fluorescein-albumin binding was measured at the time of the final test. Control FTETs were measured in 46 patients with type 1 diabetes who did not have insulin pumps and in 15 adults without diabetes. RESULTS: In the implanted insulin pump group, 50% of the FTETs were below normal, but no significant longitudinal change in FTETs was noted in eight of the nine study patients. The mean FTETs in the implanted insulin pump group were significantly higher than those of the control patients with diabetes but without insulin pumps (mean, 88 versus 62 seconds; P<0.05) but significantly lower than those of the control subjects without diabetes (88 versus 163 seconds; P<0.001). Four of the nine patients with implanted insulin pumps had normal FTETs on all three studies. This subgroup had used insulin pumps (external + implanted) for significantly longer periods (6.2 versus 2.6 years; P<0.05) than the other five patients. These differences within the implanted pump group did not correlate with differences in glycosylated hemoglobin values or fluorescein-albumin binding; however, the glycosylated hemoglobin levels before insulin pump implantation were significantly lower than those of the other five patients. Three patients with onset of type 1 diabetes before age 10 years had the lowest FTETs. CONCLUSION: Implanted insulin pumps did not alter FTETs between 6 months and 32 months after pump implantation. Total time on insulin pumps (external and implanted) is associated with normal FTET, and onset of diabetes before age 10 years is associated with abnormal FTET.

Journal Article↗
PubMedDate not supplied

Microvascular abnormalities in the bulbar conjunctiva of patients with type 2 diabetes mellitus.

OBJECTIVE: To study and quantify microvascular abnormalities objectively in vivo in patients with type 2 diabetes mellitus (T2DM). METHODS: The conjunctival microcirculation in 14 patients with T2DM and in age-matched healthy control subjects without diabetes was videotaped and objectively studied by using computer-assisted intravital microscopy (CAIM), a novel and quantitative real-time technology. RESULTS: Patients with T2DM (N = 14) had significantly (P<0.01) wider conjunctival vessel diameters (71.9 +/- 5.2 mm) than did healthy nondiabetic control subjects (54.0 +/- 4.4 mm). In the study patients, microvascular distribution was significantly (P<0.01) abnormal (36.7 +/- 18.2 versus 45.3 +/- 9.6 cm per unit area, patients versus control subjects), and vessel distribution was uneven on the surface of the bulbar conjunctiva. The arteriole:venule (A:V) ratio in patients with T2DM was extremely variable and differed significantly (P<0.01) from that in the nondiabetic control subjects (A:V approximately 1:2). In addition, a unique sinusoidal (hypertensive) vascular pattern frequently existed in some of the large veins of all study patients with T2DM but in none of the nondiabetic control subjects. CONCLUSION: We identified the presence of microvascular changes (abnormalities) in the conjunctival microcirculation of patients with T2DM. Although all these abnormalities did not appear in the same patient at the same time, the sum total of their presence in each patient correlated significantly with disease severity, as noted in the medical records. The severity of microvascular abnormalities, however, did not correlate with the duration of the disease since diagnosis. CAIM may be a useful objective and quantitative technique for assessing microangiopathy in patients with T2DM. The easy noninvasive accessibility of the conjunctival vessels and the ability to identify and locate the same vessels repeatedly for longitudinal evaluations further emphasize the usefulness of this real-time technology.

Adult↗
PubMedDate not supplied

Chronic Pseudomonas aeruginosa endobronchitis in rhesus monkeys: I. Effects of pentoxifylline on neutrophil influx.

Host defense abnormalities in cystic fibrosis (CF) against Pseudomonas aeruginosa (PA) lead to excessive neutrophil influx into the infected lungs, resulting in pulmonary complications. We have developed a rhesus monkey model of chronic PA endobronchitis by intrabronchial instillation of PA-embedded agar beads, utilizing flexible fiberoptic bronchoscopy. Treatment of infected monkeys with pentoxifylline suppressed neutrophil influx and ameliorated pulmonary damage. The results suggest a method by which neutrophil influx and pulmonary damage in CF patients can be managed or prevented.

Animals↗