The effect of insulin on renal handling of sodium, potassium, calcium, and phosphate in man

The effects of insulin on the renal handling of sodium, potassium, calcium, and phosphate were studied in man while maintaining the blood glucose concentration at the fasting level by negative feedback servocontrol of a variable glucose infusion. In studies on six water-loaded normal subjects in a steady state of water diuresis, insulin was administered i.v. to raise the plasma insulin concentration to between 98 and 193 muU/ml and infused at a constant rate of 2 mU/kg body weight per min over a total period of 120 min. The blood glucose concentration was not significantly altered, and there was no change in the filtered load of glucose; glomerular filtration rate (CIN) and renal plasma flow (CPAH) were unchanged. Urinary sodium excretion (UNaV) decreased from 401 plus or minus 46 (SEM) to 213 plus or minus 18 mueq/min during insulin administration, the change becoming significant (P smaller than 0.02) within the 30-60 min collection period. Free water clearance (CH2O) increased from 10.6 plus or minus 0.6 to 13 plus or minus 0.5 ml/min (P smaller than 0.025); osmolar clearance decreased and urine flow was unchanged. There was no change in plasma aldosterone concentration, which was low throughout the studies, and a slight reduction was observed in plasma glucagon concentration. Urinary potassium (UKV) and phosphate (UPV) excretion were also both decreased during insulin administration; UKV decreased from 66 plus or minus 9 to 21 plus or minus 1 mueq/min (P smaller than 0.005), and tupv decreased from 504 plus or minus 93 to 230 plus or minus 43 mug/min (P smaller than 0.01). The change in UKV was associated with a significant reduction in plasma potassium concentration. There was also a statistically significant but small reduction in plasma phosphate concentration which was not considered sufficient alone to account for the large reduction in UPV. Urinary calcium excretion (UCaV) increased from 126 plus or minus 24 to 200 plus or minus 17 mug/min (P smaller than 0.01). These studies demonstrate a reduction in UNaV associated with insulin administration that occurs in the absence of changes in the filtered load of glucose, glomerular filtration rate, renal blood flow, and plasma aldosterone concentration. The effect of insulin on CH2O suggests that insulin's effect on sodium excretion is due to enhancement of sodium reabsorption in the diluting segment of the distal nephron.

Metabolism of N-carbobenzoxyl-L-tryptophan by Chromobacterium violaceum

Chromobacterium violaceum (ATCC 12472) metabolizes N-carbobenzoxyl-L-tryptophan into its 2', 3'-dehydro-derivative, and indole-3-propionic acid into indole-3-acrylic acid. The biotransformation accurs in resting cell incubations, and in growing cultures of the bacterium. Tryptophan in fermentation media enhances the ability of Chromobacterium violaceum to perform the conversion by an undetermined mechanism. The amino acid also prevents stored cultures from losing the ability to accomplish the biotransformation. The reaction apparently requires oxygen, and preliminary experiments suggest that it is catalyzed by a dehydrogenase.

Binding of thyroid hormone in rabbit serum: definition of a prealbumin and effects of strain variation on binding

Sera from inbred rabbit strains have been studied to determine radio-thyroxine distribution after electrophoresis, to measure protein binding capacity for thyroxine (T4) and to examine possible interrelationships of binding capacity and serum protein-bound iodine (PBI). In electrophoretic studies at pH 7·4, serum albumin and prealbumin, the latter a previously unrecognized carrier of T4 in the rabbit, are the principal transport proteins. At pH 9·0, prealbumin is the major carrier (61% of tracer). Prealbumin also binds significant quantities of tri-iodothyronine. The mean binding capacity of serum prealbumin for T4 in 12 rabbit strains was 500 μg/100 ml.

Protein-bound iodine levels are known to be strain-dependent in the rabbit. In the current studies, however, there was no strain-specificity of prealbumin binding capacity, and no correlation between PBI and binding capacity of prealbumin, the principal T4-specific transport protein. These observations suggest that factors other than the capacity of binding proteins for T4 may be primary determinants of hormone levels (PBI) in blood in the rabbit.

Thyroid hormone binding by human serum prealbumin (TBPA). Electrophoretic studies of triiodothyronine-TBPA interaction

Thyroxine-binding prealbumin (TBPA) in normal human serum has been shown in a polyacrylamide gel electrophoresis system to bind 7-9% of tracer level purified [(125)I]triiodothyronine (T3), and more than 30% of T3 in serum deficient in thyroxinebinding globulin (TBG). The T3-TBPA interaction has been confirmed at pH 9.0 and pH 7.4 in this electrophoretic demonstration of TBPA binding of T3 in serum. Purified human TBPA has also been shown to bind T3. Progressive additions of unlabeled thyroxine (T4) to serum containing tracer [(125)I]T3 displace T3 from TBG, its principal carrier, to TBPA and albumin; however, T4 loading does not lead to significant T3 displacement from TBPA even at T4 levels known to saturate TBPA. Loading of serum with unlabeled T3 results in displacement of more than 50% of [(125)I]T3 from TBPA, as well as from TBG, to albumin. Studies carried out with serum containing diphenylhydantoin (DPH) or MK-185, known inhibitors of T4 binding by TBG, also showed T3 displacement from TBG to TBPA and albumin. Although salicylate and tetraiodothyroacetic acid (TETRAC) displace T4 from sites on TBPA, they have only minimal effects on T3-TBPA interaction.

"Wits" appraisal in southern Chinese children

The sagittal difference between the maxillary and mandibular apical bases in orthodontic diagnosis and treatment planning can be evaluated by means of the angle ANB or alternatively, by means of the "Wits" appraisal. The lateral cephalometric radiographs of a randomly selected sample of 101 Southern Chinese children aged 10-15 years, with 55 males and 46 females were traced and analyzed by the standardized method taught to dental undergraduates. The "Wits" appraisal and angulation of the A-B line to the functional occlusal plane were added in order to generate data relevant to the local population, on whom the flatness of the nose-nasion-forehead region imposes a genuine difficulty in the identification of the cephalometric nasion. Data analyses were performed under landmark nasion. Data analyses were performed under different categories with respect to age groups, 10-12 years and 13-15 years; the types of malocclusion and sex. It was found that both the angular and linear measurements were comparable to the existing norms established for the Chinese population. The "Wits" appraisal values have to be modified in order to be applicable to this population with -4.9 millimeters and -4.5 millimeters being the normal values for male and female children respectively.