Fine structure of the excretory system of Amphioxus (Branchiostoma floridae) and its response to osmotic stress

Summary The excretory organs of Amphioxus occur as segmentally arranged structures throughout the pharyngeal region and may be divided into three components: the solenocytes, the renal tubule, and the renal glomerulus.The solenocytes possess foot processes that rest upon the coelomic surface of the ligamentum denticulatum. The tubular apparatus of the solenocytes consists of ten triangular rods surrounding a central flagellum. The distal end of the tubular apparatus enters branches of the renal tubule. The renal tubule eventually opens into the atrial cavity of Amphioxus. The renal glomerulus is a sinus within the connective tissue of the ligamentum dentieculatum where it connects elements of the branchial circulation with the dorsal aorta. The renal glomerulus, like other blood vessels of Amphioxus, lacks an endothelial lining.If Amphioxus is adapted to artificial sea water at different concentrations there is no change in kidney morphology suggesting that Amphioxus is either is osmotic with its environment or is osmoregulating with other organs.This work was supported by U.S. Public Health Service Grant 5-T01-GM 00582.     

Thyroid stimulation test with serum thyroxine concentration as index of thyroid response

A thyrotropin (T.S.H.) test is suggested which relies on the change in the concentration of serum thyroxine as the index of thyroid response to T.S.H. stimulation. Ten such tests have been carried out in healthy volunteers and 39 in patients referred for routine thyroid stimulation tests. Among the advantages of such a test are that the patient does not receive ionizing radiation; it is independent of the presence of iodide-or mercury-containing compounds; and it minimizes the number of patient visits. In remote areas the patient need not attend the specialist centre, because the T.S.H. injection can be given and the serum samples taken locally, the samples then being sent to the appropriate laboratory for assay.     

Characterisation of amino acid incorporation by subcellular fractions from sterile beet disks

Summary The optimum concentrations of leucine, ATP, GTP and Mg²⁺ ion for the incorporation of leucine into protein by the microsomal fraction isolated from sterile disks of red beetroot are 0.06 mM, 5 mM, 0.5 mM, and 12 mM respectively. Incorporated ¹⁴C-leucine does not exchange with an excess of soluble-¹²C-leucine. Incorporation into protein is partly dependent on the addition of a high speed supernatant fraction which incorporates leucine into a product with the properties of aminoacyl RNA. Addition of polyuridylic acid to microsomes isolated from fresh disks stimulates the incorporation of phenylalanine into protein nine-fold but has no effect on leucine incorporation. Polyuridylic acid — stimulated incorporation is not inhibited by chloramphenicol. Preincubation of fresh microsomes with trypsin does not increase their activity. These results suggest that the low activity of fresh microsomes may be due to a lack of messenger RNA. The mitochondrial fraction shows a rise and fall in leucine-incorporating ability during aging similar to that shown by the microsomal fraction. Studies with inhibitors suggest that about 25% of this incorporation is due to the mitochondria themselves, the rest being attributable to large microsomes. Fractions isolated from disks aged under non-sterile conditions show large incorporations of leucine which are not dependent on an added energy source. This result confirms the importance of using aseptic techniques when studying the aging of storage tissue disks.