Search PubMed⌕ Search

Biomedical subjects

S M Hwang

Publications and source records attributed to S M Hwang.

100 records · Page 6Linked to original sources
PubMed1978

The ontogeny of sugar transport in kidney.

Concentrative uptake of alpha-methyl-d-glucoside (AMG) by isolated renal tubule fragments from the newborn Sprague-Dawley rat has been demonstrated and the validity of this phenomenon confirmed by an in vivo demonstration of AMG uptake by the newborn kidney cortex. A kinetic analysis of the entry phenomenon in the newborn tubule reveals the presence of two distinct membrame transport systems for AMG, only one of which is present in the adult tubule. All transport of sugar in both newborn and adult tubules was phlorizin-sensitive, but was only partially ingibited in Na+-free buffer. Glucose was shown to inhibit uptake competitively on the shared, high capacity system. Uptake on the high affinity system in the newborn represents 15-20% of the total at physiologic sugar concentrations. It is concluded that active sugar transport is a characteristic of the newborn rat kidney and that the isolated tubule preparation is a more accurate reflection of this phenomenon than is the renal cortical slice.

Age Factors↗
PubMed1977

Ontogeny of glycine transport in isolated rat renal tubules.

Isolated renal tubule preparations were made from newborn Sprague-Dawley rats and used to study initial entry rate kinetics of glycine. The results were compared to those obtained in the isolated tubule preparation from the adult rat kidney. While initial rates of glycine uptake were identical for newborn and adult tubules, significant differences in influx kinetics were demonstrated. Of the two apparent transport Km systems shown to be present in the newborn tubule, the high-affinity, low-capacity system accounts for about 40% of total glycine uptake at physiologic concentrations. The high-affinity, low-capacity system of the adult tissue accounts for about 10% of total uptake at the same concentration range. The data lend strength to the argument against the concept that the physiologic hyperglycinuria of the newborn rat is due to either impaired ability to concentrate glycine intracellularly or to absence of one or more transport mechanisms for glycine.

Animals↗
PubMed1976

Effect of maleic acid on the kinetics of alpha-methyl-D-glucoside uptake by isolated rat renal tubules.

ALPHA-Methyl-D-glucoside has been used to study the invitro mechanism of the effect of maleic acid on sugar transport, using isolated rat renal tubule fragments. 6 mM maleate maximally inhibits the ability of the tubule to establish a concentration gradient for this model sugar with no evidence of ultrastructural changes. This inhibition is due to a 100% increase in efflux, as well as to a 50% decrease in influx with more prolonged incubation. The data presented here are consistent with those of other workers, but their work does not explain our results, which therefore deserve further investigation by other techniques.

Animals↗
PubMedDate not supplied

The efficacy of treatment with triamcinolone acetonide in calcinosis cutis following extravasation of calcium gluconate: a preliminary study.

Neonatal hypocalcemia is not an uncommon condition, especially in the premature neonate. It is effectively treated by intravenous administration of calcium gluconate. Complications of extravasation during intravenous infusion include localized calcification and occasionally necrosis. When this occurs, however, there is no specific mode of treatment except supportive management and skin graft. This experiment was designed to evaluate the efficacy and safety of treatment with triamcinolone acetonide in calcinosis cutis following extravasation of calcium gluconate. Initially, 2 cc of 10% calcium gluconate was injected subcutaneously into two rabbits at seven sites on the shaved skin of the back. Another two rabbits were injected at the same sites with 0.5 cc of triamcinolone acetonide (10 mg/dl) after injection of 2 cc of 10% calcium gluconate. As a control, 2 cc of normal saline was injected into another rabbit in the same manner. These five rabbits were observed over the next 7 weeks and underwent pathologic examination at various intervals (on days 1, 3, 8, 15, 30, 37, 45). In the 10% calcium gluconate injected rabbits, nodules and large ulcerated lesions developed after 15 days. Multiple, linear, ulcerative and indurated masses were noted on day 37. The lesions healed progressively with a decrease in ulceration, and after 2 months, the masses disappeared gradually. Histologically, on day 15 calcium deposits were seen in the walls of the arteries, veins, dermis, and muscle fibers and epidermal necrosis was seen at the injection sites. From day 37 discharge of calcium deposits began to take place by means of transepidermal elimination. After 2 months, the calcium and mucin deposition was observed focally in the dermis. In the rabbits injected with 10% calcium gluconate and triamcinolone acetonide, mild erythema and induration were seen after day 15 at the injection sites; this gradually disappeared. After 30 days the injection sites were normal in appearance. Histologically, at day 15 calcium deposition was seen in the upper dermis, but after 1 month the injection sites were histologically normal. We suggest that intralesional injection of triamcinolone acetonide for the treatment of calcinosis cutis following extravasation of calcium gluconate is effective, probably due to its antiinflammatory effect and its role in facilitating the resorption of calcium in the tissue.

Administration, Topical↗
PubMedDate not supplied

The pretreatment effect of chemical skin penetration enhancers in transdermal drug delivery using iontophoresis.

The transdermal drug delivery (TDD) system has largely been divided into physical, biochemical and chemical methods. Recently, combinations of these methods were introduced for more effective delivery with less side effects. We performed this study to identify the effectiveness and mechanism of TDD using the physical method, 'iontophoresis', plus the chemical method, 'pretreatment with chemical enhancer'. The action sites of chemical enhancers in the stratum corneum (SC) were observed by electron microscope. We also studied whether this combined method synergistically impaired the skin barrier. To confirm the synergistic effect on skin penetration by this combined method, we measured the blood glucose level after insulin iontophoresis following a chemical enhancer pretreatment in rabbits. The results were that (1) dilatation of the intercellular lipid layers of the SC and lacunae was prominent in pretreatment with chemical enhancers inducing high transepidermal water loss (TEWL); (2) the skin barrier impairment, with repeated treatments showing an increased TEWL and also epidermal proliferation, was increased with the chemical enhancers that showed a high TEWL immediately after treatment; (3) the combination of chemical enhancer pretreatment and iontophoresis showed no synergistic impairment of the skin barrier, and (4) the chemical enhancer pretreatment with greater impairment of the skin barrier could increase the delivery of insulin by iontophoresis. The results showed that a combination of chemical enhancer pretreatment and iontophoresis could deliver drugs more effectively than iontophoresis alone. Our proposed theory is that iontophoretic drug delivery may be easier through the dilated intercellular spaces of the SC which have a lower electrical impedance following the chemical enhancer pretreatment. Because the effect and the side effects in the combination are decided by the chemical enhancer rather than iontophoresis, the development of proper chemical enhancers is important in future plans.

Administration, Cutaneous↗
PubMedDate not supplied

Liquid chromatographic determination of vitamin K1 trans- and cis-isomers in infant formula.

The normal phase liquid chromatographic (LC) method for determination of trans- and cis-isomers of vitamin K1 (phylloquinone) in infant formula described here uses an Apex silica column, isocratic elution, and UV absorption detection at 254 nm. Vitamin K1 is extracted quantitatively from the product matrix by pretreating the as-fed liquid with concentrated ammonium hydroxide and methanol, and then extracting it with a 2:1 mixture of dichloromethane and isooctane. The extract is cleaned up by silica open-column chromatography and concentrated for LC analysis. For trans-vitamin K1, the method precision is less than or equal to 3.3% RSD (relative standard deviation), and the spike recovery is 98 +/- 4%. For cis-vitamin K1, the precision is less than or equal to 12% RSD, determined at levels near the detection limit, and the spike recovery is 95 +/- 9%. The detection limit is 0.3 ng for both isomers at signal/noise = 3.

Chromatography, Liquid↗