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Biomedical subjects

J C Chan

Publications and source records attributed to J C Chan.

At least 271 records · Page 15Linked to original sources
PubMed1991

Concurrent acute myeloid leukemia and systemic mastocytosis.

A 51-year-old woman presented with concurrent systemic mastocytosis and acute myeloid leukemia associated with a clonal karyotypic anomaly of t(8;21). Cytochemical, histologic, and cytogenetic studies helped in the distinction from a recently described entity: acute myeloid leukemia with marrow basophilia. Although the leukemia responded well to aggressive chemotherapy, the mastocytosis component worsened, illustrating the inherent resistance of mastocytosis to chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Attenuation of LPS-induced neutrophil thromboxane b2 release and chemiluminescence.

Polymorphonuclear leukocytes (PMN) may play a key role in acute lung injury and ARDS. The mechanisms of PMN-mediated lung injury include the release of inflammatory mediators, such as oxygen free radicals which cause direct tissue injury, and arachidonic acid metabolites which cause pulmonary vasoconstriction and increased vascular permeability. The goals of this in vitro study were 1) to assess the effects of PMN-activating agents (lipopolysaccharide, LPS; phorbol myristate acetate, PMA; tumor necrosis factor, TNF) on PMN thromboxane B2 (TXB2) release and oxygen free radical production and 2) to determine the effects of agents purported to suppress PMN activity (pentoxifylline, PTX; adenosine; dibutyryl cyclic AMP, DBcAMP; and terbutaline, TBN) on activator-induced PMN TXB2 release and oxygen free radical production. PMN TXB2 release was determined by radioimmunoassay and oxygen free radical production was monitored by chemiluminescence. Our results show that 1) LPS and PMA significantly increase PMN TXB2 release, whereas tumor necrosis factor (TNF) has no effect; 2) LPS and PMA significantly increase PMN chemiluminescence; 3) DBcAMP and TBN significantly reduce LPS-induced PMN TXB2 release whereas PTX and adenosine do not; 4) TBN significantly reduces PMA-induced PMN TXB2 release whereas other agents do not; 5) All agents (PTX, adenosine, DBcAMP, and TBN) significantly reduce LPS-induced PMN chemiluminescence but none attenuate PMA-induced PMN chemiluminescence. We conclude that: LPS and PMA activate PMN manifested by TXB2 release and chemiluminescence. Additionally, all the PMN suppressing agents do attenuate some PMN functions. Of interest, PTX, adenosine, DBcAMP, and TBN have different effects depending upon functional assay and activating agent. It will be important to investigate the mechanisms by which PMN suppressing agents alter signal transduction resulting in differential effects on PMN function.

Adenosine↗
PubMed1991

Uptake of fluoride by sound and artificially carious enamel in vitro following application of topical sodium and amine fluorides.

The aim of this investigation was to compare fluoride uptake and retention by sound and artificially carious enamel, after the topical application of a neutral sodium fluoride solution (NaF) or a commercial preparation containing aqueous amine fluorides (AF) 297 and 335 (Elmex Fluid, GABA International, Basel, Switzerland). Ten pairs of extracted premolars were used, one of each pair being treated with NaF and the other with AF. A lactic acid gel technique was used to produce artificial caries lesions on one-half of the buccal surface of the premolar crowns. Estimates at selected depths of pretreatment fluoride concentration, uptake and retention were made using a step-wise acid-etch sampling technique. AF produced much greater uptake than NaF, the difference being most marked in the deeper layers of the artificial lesions, suggesting that the amine fluorides had a strong affinity for demineralized enamel. After storage in normal saline for 1 week during which partial loss of the acquired fluoride occurred, the percentages retained ranged from 37 (NaF) to 65 percent (AF). It was concluded that AF enhanced both uptake and retention of fluoride by (artificial) early enamel caries lesions.

Adolescent↗
PubMed1991

Systemic effects of inflammation in bronchiectasis.

A group of bronchiectatic subjects in the clinically stable state were studied for systemic evidence of inflammation. The following parameters were evaluated: body weight, serum albumin, serum globulin, serum alpha 1-antitrypsin (alpha 1 AT) and peripheral white cell count. For serum albumin and globulin, comparison was made between subjects with bronchiectasis and control subjects with no known pulmonary disease matched for sex and age, and for serum alpha 1 AT and peripheral white cell count, matched for smoking habit as well. The bronchiectatic subjects showed systemic effects of inflammation as indicated by lower body weight and serum albumin (P less than 0.01), higher serum globulin (P less than 0.001), serum alpha 1 AT (P less than 0.05) and total leucocyte count (P less than 0.05). Differential white cell count showed that the elevation was distributed in most cell types. Correlation matrix was done for the above systemic parameters and indices of airway inflammation including sputum volume, purulence, and polymorph count and FEV1. There was an inverse correlation between total peripheral WBC count and FEV1 in percentage of predicted (P less than 0.01), and a positive correlation between sputum purulence and sputum polymorph score (P less than 0.05). This suggests that host peripheral leucocyte response may be a factor in the determination of lung function.

Adolescent↗
PubMed1991

Cortisone effects on growth, food efficiency, and in vitro growth hormone release.

These studies were designed to investigate the cause of growth retardation during glucocorticoid treatment in rats. In young animals, body weights and amounts of food consumed were measured at two-day intervals, beginning at 29 days of age. Average food intake and food efficiency were calculated. Animals were treated with cortisone (CORT, 5 mg/rat/day, s.c.) or saline (SAL) for eight days between 37 and 44 days. Growth hormone (GH) release by dispersed pituitary cells in response to nine concentrations of GH-releasing hormone (GHRH) were tested by in vitro perifusion at 45 and 73 days. As previously shown, CORT caused a cessation of growth during the treatment period, and body weight failed to catch up. Food efficiency was decreased during CORT treatment. All parameters of in vitro GH release including basal GH secretory rate, overall GH response to GHRH, and the GHRH concentration-response curves were significantly increased by CORT in the 45-day-old animals. An age-related increase in GH release was also observed between the 45 and 73 day saline-treated animals. These results support the hypothesis that glucocorticoids inhibit growth by induction of changes in food metabolism and GH secretion. The effect on the pituitary gland itself paradoxically involves an increase in GH secretory capacity in response to GHRH.

Animal Nutritional Physiological Phenomena↗
PubMed1991

Case report: hypothyroidism due to pneumocystis carinii thyroiditis in a patient with acquired immunodeficiency syndrome.

Pneumocystis carinii is the most common cause of opportunistic pulmonary infection in AIDS patients and disseminated disease is being recognized with increasing frequency. We describe a patient with cavitary pulmonary disease, lymphadenopathy, thyroiditis, and associated hypothyroidism, all a result of P. carinii. The organism was easily demonstrated in a fine-needle aspirate specimen of the thyroid. This is the second reported case of clinically apparent Pneumocystis thyroiditis and the first reported case of hypothyroidism due to an opportunistic infection in a patient with AIDS. Clinicians should be aware of this entity and request a Grocott-Gomori methenamine-silver nitrate stain of appropriate cytology specimens to make the diagnosis.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Histiocytosis X involving the thyroid and hypothalamus.

A case of histiocytosis X involving the thyroid and hypothalamus is reported. A 16 year old female presented with amenorrhoea and diabetes insipidus. She subsequently developed a painful goitre with biochemical hypothyroidism, and stridor. The stridor and goitre responded to cyclophosphamide. Previous publications on the use of cytotoxics in histiocytosis X involving the thyroid are reviewed. We describe for the first time both the ultrasound appearances of the thyroid in this condition and the use of serial volumetric measurements to monitor therapy.

Adolescent↗
PubMed1991

Hypercalciuria due to combined growth hormone and calcitriol therapy in uremia: effects of growth hormone on mineral homeostasis in 75% nephrectomized weanling rats.

The administration of growth hormone (GH) in conjunction with calcitriol in uremia may increase urinary calcium and decrease renal phosphate excretion, which could have an adverse effect on the kidney in chronic renal insufficiency. The effect of 40 d of ovine GH, calcitriol, and the combination of GH and calcitriol on mineral excretion was studied in rapidly growing uremic rats. Uremia was produced by 75% nephrectomy, and the animals were fed a diet containing 8% protein with equal quantities of calcium (0.6%) and phosphate (0.6%). The uremic rats treated with ovine GH were significantly longer and heavier than the uremic control rats and the uremic rats treated with calcitriol alone. However, the combination of calcitriol and GH abolished the beneficial effect of GH on growth and increased urinary calcium excretion 4-fold over uremic controls whether expressed as calcium excretion per 100 g body weight, urine calcium to creatinine ratio, or as fractional calcium excretion. Calcitriol therapy alone also significantly increased calcium excretion, but not to the extent that the combination therapy did. This increased urinary calcium excretion in the GH plus calcitriol group was not associated with an increase in calcium and sodium intake, plasma ionized calcium, or urinary sodium excretion. The calcium content of the femurs from all uremic rat groups was significantly lower than that of the sham control rats; however, there was also no further decrease in bone calcium content in the GH plus calcitriol group compared with uremic controls. This indicated that bone was not the source of this excess urinary calcium.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Immunochemical comparison of transformation-associated protein and secreted phosphoprotein.

Transformation-associated protein (TAP) has been detected in MSV-M-transformed rat cell lines as glycosylated, weakly phosphorylated protein of molecular weight (Mr) 66,000 and 68,000. In the ts-MSV-M-transformed rat kidney cell line (6m2), the synthesis of TAP and the v-mos gene product is temperature-sensitive and accompanies the expression of transformation phenotypes. Therefore, TAP potentially plays a role in cellular transformation. On the other hand, SPP represents a family of glycosylated phosphoprotein with apparent Mr ranging from 42,000 to 69,000. SPP has been detected in osteoblasts and in avian and murine retrovirus-transformed rat and mouse epithelial cells. Therefore, the potential relatedness of TAP and SPP was studied. Using the 6m2 cells, we found that SPP was strongly phosphorylated and was synthesized at both the permissive (33 degrees C) and non-permissive (39 degrees C) temperatures. By contrast, TAP was weakly phosphorylated, and was synthesized, as we found previously, only at the permissive temperature of 33 degrees C. Furthermore, in 35S-methionine incorporation studies, TAP became heavily labelled whereas SPP was not (consistent with its amino acid composition having few methionine residues). Using 125I-TAP in both immunoprecipitation and radioimmunoassays, it was found that an antiserum raised against SPP did not cross-react with 125I-TAP. Additionally, SPP has now been found in many human and rodent cells, while TAP thus far has only been detected in MSV-transformed rat cells. These data suggest that structurally, TAP and SPP are not closely related phosphoproteins.

Animals↗