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Biomedical subjects

J C Chan

Publications and source records attributed to J C Chan.

At least 325 records · Page 18Linked to original sources
PubMed1988

Chronic renal failure in infants and children.

Chronic renal failure is an uncommon problem for pediatricians, but early recognition is important for maximizing growth and minimizing complications. Marked strides have been made in understanding and treating renal osteodystrophy. Recombinant erythropoietin holds the promise of reversing the anemia associated with renal insufficiency. Dialysis remains an important therapy for sustaining these children, and transplantation offers realistic hope for a functioning kidney.

Aluminum↗
PubMed1988

Acid alpha-neuraminidase deficiency: a nephropathic phenotype?

Isolated neuraminidase deficiency is a member of the relatively rare group of storage disorders known as glycoproteinoses. We report the long-term natural history of the disease in one of the first patients described in the literature. An unusual feature of the disease is the abrupt onset and fulminant nature of the nephrotic syndrome, complications of which caused the demise of our patient. Pathological examination of the kidneys from this child revealed renal epithelial cell damage, most marked in the membranes of the glomeruli and proximal tubules, findings which are consistent with the high sialic acid content of the membrane in these areas of the nephron. Chemical analysis indicated that the bulk of the stored material in the kidney was in the form of polar sialyloligosaccharides of high molecular weight. On the basis of our experience, as well as the previous reports of neuraminidase-deficient patients with nephropathy, we propose a nephropathic phenotypic variant of type 2 infantile sialidosis.

Brain↗
PubMed1988

Aluminum metabolism in rats: effects of vitamin D, dihydrotachysterol, 1,25-dihydroxyvitamin D and phosphate binders.

In order to study the effects of vitamin D on aluminium balance when different forms of vitamin D and phosphate binders are used simultaneously for therapeutic purposes, 30 Sprague-Dawley weanling rats, weighing 44-66 g, were randomly assigned to 5 groups: (A) control, (B) aluminum hydroxide, (C) dihydrotachysterol at 16 micrograms/kg/day, (D) 1,25-dihydroxyvitamin D at 16 ng/kg/day and (E) vitamin D at 2,000 IU/kg/day. Aluminum hydroxide (60 mg/kg/day) in the feed was provided to all except the control group. The vitamin D or metabolites were fed by stomach tube daily for a period of 10 days. At the end of the study, the mean (+/- SEM) serum aluminum concentration, as determined by flameless atomic absorption spectrophotometry, was 5.0 +/- 2.4 micrograms/l; there were no significant differences in these results between groups. During the last three days of the study, 24-hour urine and stool collections were made with the usual precautions against trace mineral contamination. The means (+/- SEM) of aluminum balances for groups A, B, C, D and E were -388 +/- 261, 1,121 +/- 331; 2,316 +/- 304; 2,387 +/- 245, and 1,968 +/- 337 micrograms/day, respectively. We conclude that at therapeutic doses of aluminum hydroxide and vitamin D or its metabolites, hyperaluminemia was not observed. However, the positive aluminum balances imply retention, and the use of vitamin D, especially its potent metabolites dihydrotachysterol and 1,25-dihydroxyvitamin D, intensified this risk.

Aluminum↗
PubMed1988

The use of the "Bi-Digital O-Ring Test" to determine whether or not to give acupuncture in pain conditions.

The "Bi-Digital O-Ring Test" was used as a guide in determining the modality of treatment of pain conditions. Seven cases are presented in which patients came primarily for acupuncture. They were not treated with acupuncture; instead, they were given antibiotic therapy because the Bi-Digital O-Ring Test had revealed the presence of infection. The antibiotic therapy resulted in dramatic improvement.

Acupuncture Therapy↗
PubMed1988

Spontaneous group B Salmonella enteritidis peritonitis in cirrhotic ascites and acquired immune deficiency syndrome.

Salmonella represents an infrequent cause of spontaneous bacterial peritonitis in cirrhotic ascites. A cirrhotic patient, an alcoholic and former intravenous drug abuser, developed spontaneous group B Salmonella enteritidis (undetermined serotype) bacterial peritonitis. The isolation of this pathogen, a common cause of bacteremia in acquired immune deficiency syndrome, led to the serological determination of infection with human immune deficiency virus (HIV).

Ascites↗
PubMed1987

Rat transformation-associated proteins (TAP) induced by Moloney murine sarcoma virus interact with specific receptors on normal rat kidney cells.

In this report, data are presented to show that transformation-associated proteins (TAP) secreted from the transformed 6M2 cells have mitogenic activities in the stimulation of DNA synthesis and proliferation of normal rat kidney (NRK-2) cells and of nonpermissively grown 6M2 cells. TAP also bound specifically to NRK-2 cells with a binding dissociation constant (Kd) of 1.4 pM. Approximately 2 X 10(5) binding sites per cell were found. Therefore, TAP may represent a set of virally-induced growth stimulatory factors.

Animals↗
PubMed1987

Renal hypophosphatemic rickets. Growth and mineral metabolism after treatment with calcitriol (1,25-dihydroxyvitamin D3) and phosphate supplementation.

To delineate the mineral metabolism of renal hypophosphatemic rickets and to update progress in linear growth after calcitriol (1,25-dihydroxyvitamin D3) therapy, the medical records of 19 patients were examined retrospectively from January 1978 through December 1985. With a mean (+/- SD) follow-up period of 42.0 +/- 5.4 months after calcitriol had been administered for at least 12 months, the growth measurements were as follows: the percentile weight (mean +/- SD) remained unchanged, with the initial being 12.3% +/- 17.3% and the final being 15.3% +/- 18.6%, and the length/height percentiles were -2.7% +/- 5.9% and -2.4% +/- 4.4%. The growth velocity index showed a significant improvement from mean values of 61.7% (at age 2 years) to mean values of 101.2% (at age 11.2 years). Serum phosphate concentrations rose from the initial value of 2.9 +/- 0.6 to 3.5 +/- 0.8 mg/dL (0.9 +/- 0.2 to 1.1 +/- 0.3 mmol/L). The effects of calcitriol on renal function were tested by creatinine clearance values, which were 127 +/- 22 mL/min/1.73 m2 (2.12 +/- 0.37 mL/s/1.73 m2) at the conclusion of the study, compared with 128 +/- 25 mL/min/1.73 m2 (2.13 +/- 0.41 mL/s/1.73 m2) obtained at the initiation of calcitriol therapy. We conclude that calcitriol treatment of renal hypophosphatemic rickets in children results in improvement of growth velocity and serum phosphate concentration without deterioration of renal function.

Adolescent↗
PubMed1987

Nutritional management of children with chronic renal failure. Summary of the task force on nutritional management of children with chronic renal failure.

Current information on the adaptations to progressive loss of renal function is presented. The assessment of renal function in infants and children using serum creatinine concentration and its derivatives is considered as are various methods for assessment of growth. Children with creatinine clearances less than 50% of normal, who do not have uremic symptoms (and who are not on dialysis), should be ingesting diets providing close to 100% of the RDA for calories with 8% of the calories as protein. Recommendations for nutritional management of children on chronic peritoneal dialysis are also presented.

Child↗
PubMed1987

Monoclonal antibody study of the subcellular localization and DNA-stimulating activity of murine sarcoma virus-activated transformation-associated proteins.

Previously, we reported the monoclonal antibody detection of transformation-associated proteins (TAP) in ts110 murine sarcoma virus-transformed normal rat kidney (6M2) cells (Chan et al., 1986). In this study, we used the same monoclonal antibody to investigate the subcellular localization, the fate and the mitogenic activity of TAP, as well as the correlationship between TAP synthesis and the expression of transformation properties of 6M2 cells. It was found that TAP were localized in the cytoplasm (probably the Golgi apparatus) of 6M2 cells. TAP were found as three intracellular polypeptides (mol wt of 66K, 63K, and 60K, respectively), and were rapidly released into extracellular medium. Upon release, TAP changed to two extracellular polypeptides (mol wt of 68K and 64K, respectively). Furthermore, the synthesis of TAP was temperature sensitive and correlated closely with the expression of transformation properties of the 6M2 cells. TAP have been purified by monoclonal antibody-affinity column chromatography and found to have a synergistic effect with insulin in stimulating the DNA synthesis of normal rat kidney cells.

Animals↗
PubMed1987

Maps of auditory cortex in cats reared after unilateral cochlear ablation in the neonatal period.

The responses of many neurons recorded in the high best-frequency region of primary auditory cortical field, AI, of the normal adult cat depend upon intensity differences of the sounds arriving at the two ears. These binaural interactions are exhibited early in postnatal life, well before structural maturation of the auditory pathways from the ear to the cortex is complete. The aim of the present work was to study certain aspects of the functional development of the auditory cortex in adult cats unilaterally deaf from birth. In adult animals reared with a neonatal cochlear ablation, field AI ipsilateral to the non-operated ear showed a normal tonotopic map, which was derived from single neurons and neuron clusters driven securely by best-frequency tonal stimulation in virtually every electrode penetration. The acoustic thresholds at many recording sites were as low as those obtained in AI contralateral to the non-operated ear. These findings are in marked contrast to those from control experiments on normal adult cats where only about 65% of AI neurons were excited by a sound delivered to the ipsilateral ear and where thresholds to ipsilateral ear stimulation were significantly higher than contralateral thresholds. The spatial distribution of cortical neurons based on acoustic thresholds also appeared to be different in cats unilaterally deaf from birth when compared to control cats. Closely spaced electrode penetrations in AI ipsilateral to the non-operated ear suggested that neurons were separated into low-threshold regions and high-threshold regions. There was no evidence for this type of non-random segregation in control experiments.

Animals↗
PubMed1987

Effects of interaural time delays of noise stimuli on low-frequency cells in the cat's inferior colliculus. II. Responses to band-pass filtered noises.

1. We studied cells in the central nucleus of the inferior colliculus of the cat that were sensitive to interaural time delays (ITDs) in order to evaluate the influence of the stimulus spectrum of noise signals. Stimuli were sharply filtered low-, high-, and band-pass noise signals whose cutoff frequencies and bandwidths were systematically varied. The responses to ITDs of these noise signals were compared with responses obtained to ITDs of broadband noise and pure tones. 2. The discharge rate in response to band-pass noise as a function of ITD was usually a cyclic function with decreasing peak amplitudes at longer ITDs. The reciprocal of the mean interval between adjacent peaks indicated how rapidly the response rate varied with ITD and was termed the response frequency (RF). This RF was approximately equal to the median frequency of the stimulus spectrum filtered by the cell's sync-rate curve, which was the product of the synchronization to interaural phase and the discharge rate plotted against frequency. This suggests that the RF was determined by all the spectral components in the stimulus that fell within the frequency range in which the cell's response was synchronized. The contribution of each component was proportional to the sync-rate for that frequency. 3. The central peak of the ITD function usually fell within the physiological range of ITDs (+/- 400 microseconds). The location of this peak did not vary significantly with changes in stimulus spectrum by comparison with responses to tones of different frequency. Its shape also remained constant, except for a decrease in width when high-frequency components within the range of the sync-rate curve were added to the stimulus. A few cells responded with a minimal discharge instead of a maximal near-zero ITD, and this central minimum had similar properties as the central peak. The amplitude of the secondary peaks of the ITD function decreased as the stimulus bandwidth that overlapped the sync-rate curve broadened. 4. The sum of the ITD functions to two band-pass signals was similar to that of a broadband signal whose spectrum was composed of the sum of the band-pass spectra. 5. From these binaural responses we could make inferences about the response characteristics of the monaural inputs to binaural neurons. We then verified these predictions by studying responses of low-frequency trapezoid body fibers to band-pass noises.

Acoustic Stimulation↗
PubMed1987

Effects of interaural time delays of noise stimuli on low-frequency cells in the cat's inferior colliculus. III. Evidence for cross-correlation.

1. We tested the coincidence, or cross-correlation, model of Jeffress, which proposes a neuronal mechanism for sensitivity to interaural time differences (ITDs) in low-frequency cells in the central nucleus of the inferior colliculus (ICC) of the cat. Different tokens of Gaussian noise stimuli were delivered to the two ears. We studied the neural responses to changes in ITDs of these stimuli and examined the manner in which the binaural cells responded to them. All of our results support the idea that the central binaural neurons perform an operation very similar to cross-correlation on the inputs arriving from each side. These inputs are transformed from the actual acoustic signal by the peripheral auditory system, and these transformations are reflected in the properties of the cross-correlations. 2. The responses to ITDs of identical broadband noise stimuli to the two ears varies cyclically as a function of ITD at a frequency close to the best frequency of the neuron. This cyclic response is a consequence of the narrowband filtering of the wideband acoustic signal by the auditory nerve fibers. To examine the effects of using stimuli to the two ears that were correlated to each other to different degrees, we generated pairs of noises. Each pair consisted of one standard noise, which was delivered to one ear, and a linear sum of two standard uncorrelated noises, which was delivered to the other ear. The responses of 34 neurons in the ICC to ITDs of noises with variable interaural coherence were examined. When partially correlated noises were delivered, there was a positive and approximately linear relationship between the degree of modulation of the response as a function of ITD and interaural coherence. The degree of modulation was measured by the synchronization coefficient, or vector strength, over one period of the ITD curve. 3. We examined the effects of altering the interaural phase relationships of the input noise stimuli. The phase of the noise stimuli was changed by digitally filtering the standard noise so that only a phase delay was imposed. The responses to ITDs with differing interaural phase relationships were then studied by delivering a phase-shifted noise to one ear and the standard noise to the other. The ITD curves in response to phase-shifted noise were shifted by about the same amount as the shift of the stimulus; the shift of the response was measured with respect to the case with identical noises to the two ears.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗
PubMed1987

Synthesis of specific transformation-associated proteins (TAPs) in two rat cell lines is closely related to the expression of the v-mos gene product of Moloney murine sarcoma virus (Mo-MSV).

The 6M2 cell line was established by transformation of normal rat kidney cells with the ts110 mutant of Moloney murine sarcoma virus (Mo-MSV). P85gag-mos was found to be the only known viral-transforming protein in this cell system. Previously, we described the detection in 6M2 cells of rat-specific transformation-associated proteins (TAPs) using a monoclonal antibody (MC). In this study, we used MC to investigate further the expression of TAPs at different temperatures and the time course of turn-on and shut-off of TAPs upon temperature shifting. It was found that TAPs were expressed at 24, 28 and 33 degrees C, but not at 37 and 39 degrees C. In experiments of temperature shifting, TAPs reappeared in about 6 h in 6M2 cells after the temperature was shifted from 39 to 33 degrees C, following closely the reappearance of P85gag-mos. The data in this communication support the notion that TAPs might be activated by the v-mos gene product during the process of transformation.

Animals↗
PubMed1987

Effect of variations in dietary calcium on renal and intestinal calcium-binding proteins.

This study was designed to determine if protein-induced calciuria was related to alterations in the intestinal and renal calcium-binding proteins (CaBP). Weanling Sprague-Dawley rats were fed diets containing low, normal, or high Ca and protein diets for 2 wk. Twenty-four-h urine and fecal samples were collected before the termination of the study. Plasma, kidney, duodenum, ileum, and femur samples were obtained for selected mineral and CaBP analyses. Growth was significantly depressed on the low protein diets and this was independent of Ca levels. Hypercalcemia, hypercalciuria, and increased renal CaBP were associated with the high Ca intakes but not with the high protein diets. It is suggested that in conditions where Ca intakes are high, the renal CaBP has a role in Ca excretion and responds to changes in Ca concentrations occurring in the distal tubule. No loss of femur Ca was seen in rats on the high protein diets.

Animals↗
PubMed1987

Detection of human plasma-associated hepatitis B surface antigens by monoclonal antibodies (MAb): the same MAb can be used as both capture and tracer antibody.

We have produced a monoclonal antibody (MAb), designated 11G12, of IgG1 isotype that recognizes group-specific epitopes of the HBsAg. It was demonstrated that the same MAb 11G can be used effectively as both the capture and tracer antibody to detect HBsAg in human plasma samples, using sandwich radioimmune assays (11G-11G sRIA) and sandwich avidin-biotin types of enzymatic assays (11G-11G sABC). The sensitivities for 11G-11G sRIA and 11G-11G sABC is 2.5 ng/ml and 5.0 ng/ml of HBsAg, respectively. Our data suggest that sufficient numbers of the same epitope exist on the HBsAg so that the use of the same MAb as both capture and tracer antibody does not reduce the sensitivity of the assays. The use of MAb 11G as both capture and tracer also minimizes the "hook effect" often encountered in testing high concentrations of plasma HBsAg by other assays. We also experimented with a sandwich RIA in which MAb 11G was used as the capture and polyclonal anti-HBs antibody as the tracer and found that such a combination increased the sensitivity of detection to 1.25 ng/ml of HBsAg.

Antibodies, Monoclonal↗