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Biomedical subjects

M London

Publications and source records attributed to M London.

At least 55 records · Page 3Linked to original sources
PubMed1984

Oral thyroxine: variation in biologic action and tablet content.

Thirty-two patients with primary hypothyroidism were given oral thyroxine as Levothroid or Synthroid to see if the two preparations had similar effects. The serum thyroxine was used as an index of bioavailability and the serum thyrotrophin as an index of biologic activity. The serum thyroxine was lower in all 32 patients when taking Synthroid than when taking Levothroid. In 15 patients the serum thyroxine level fell low enough to raise the serum thyrotrophin; in all 15 the serum thyrotrophin rose when taking Synthroid. Direct measurement of thyroxine in the tablets showed that the tablets of Synthroid contained 20% to 30% less thyroxine than their stated content. Thus, the decreased bioavailability (lower serum thyroxine) and decreased biologic action (higher serum thyrotrophin) of Synthroid were due to the lower content of thyroxine. An incidental observation is that the range of serum thyroxine in treated hypothyroid patients is 7.6 to 16.6 micrograms/dL, higher than in normal persons. Because oral thyroxine is widely used, a cooperative effort among manufacturers, the United States Pharmacopeia and Food and Drug Administration, and clinicians to ensure the potency and biologic action of oral thyroxine is in order. Meanwhile, it seems reasonable to use oral thyroxine that is close to the stated content.

Biological Availability↗
PubMed1982

The renal handling of beta 2-microglobulin in the dog.

The renal extraction of beta 2-microglobulin (beta 2M) was investigated under steady-state conditions achieved by constant infusion of human beta 2M. Fifteen animal experiments were conducted. Beta 2 microglobulin was infused at rates ranging from 51 o 269 micrograms/min. The renal arterial and venous blood levels remained constant throughout the study period. The data showed that renal extraction of beta 2M exceeded the rate of filtration at all levels of beta 2M delivered to the kidney. The tubular uptake of filtered beta 2M increased linearly as did the extraglomerular extraction throughout the range investigated. There was no evidence of beta 2M (FE beta 2M) increased linearly with the fractional excretion of filtered water (FE H2O). The results are interpreted to indicate that beta 2M is extracted from renal blood by glomerular filtration and, in addition, by a mechanism independent of glomerular filtration rate (GFR). Under the conditions existing in these experimental animals, the linear relationship between FE beta 2M and FE H2O is evidence to suggest that factors affecting proximal tubular water reabsorption also affect beta 2M reabsorption.

Animals↗