The preoperative use of computed tomographic (CT) scanning continues to be the best diagnostic method for preoperative detection of metastatic neck disease. Current accepted criteria for CT diagnosis of nodal disease are not uniform, although nodal size, nodal grouping, and central necrosis correlate strongly with malignancy. To assess the relationship of nodal size and malignancy, a multicenter study was designed to evaluate the nodes from 100 neck dissections. Sixty-nine positive neck dissections were analyzed, and every node was measured. The relationship of central necrosis was also compared with node size. Our results showed that CT scanning continues to provide a reliable picture of the histologic status of lymph nodes. Using the criterion of central necrosis or node size larger than 1 cm, only 7% of necks had nodal disease that would have been missed by CT interpretation. This study supports the continued use of preoperative CT evaluation for metastatic neck disease.
A method is described for the assay of insulin. It involves pre-incubation of insulin under assay with an excess of guinea pig anti-insulin serum and subsequent incubation of the partially neutralized serum with an excess of unlabeled and/or I-131-labeled bovine insulin. If no more than about half of the antibodies in the serum are neutralized during pre-incubation, then the amount of bovine insulin bound during incubation decreases linearly and in proportion to the amount of pre-incubated insulin. Such a linear relationship was obtained with nine samples of pooled serum from five groups of guinea pigs and was shown to be applicable •over a wide range of serum and insulin concentrations. Since neutralized acid-alcohol affected the assay only when present in relatively high concentrations, the method has been applied to neutralized acid-alcohol extracts of pancreatic tissue without removal or excessive dilution of the alcohol. It is applicable at concentrations of insulin to be found in blood and is therefore a potentially simple and rapid method which would not require the use of labeled insulin of high specific activity. The uses and limitations of the method are discussed. DIABETES 27:53746, September, 1968. After partial neutralization with mammalian insulins, the ability of guinea pig anti-insulin serum to combine with bovine insulin decreases, the decrease (within limits) being proportional to the amount of pre-incubated neutralizing insulin. 1 By means of this technic, insulin secretion has been measured in vivo in the rat 2>3 and in vitro from pancreatic tissue or isolated islets of the rat, 4 -5 Chinese hamster, 6 Egyptian sand rat, 7 and mouse. 8 It is here shown that this method of insulin assay is applicable over a wide range of insulin concentrations down to those to be expected in plasma, and is little affected by low concentrations of alcohol to be found in extracts of pancreatic tissue and isolated islets.
INSULIN-IMMUNOASSAY ESTIMATED RECOVERY nomena are related. Perhaps the large initial inhibition of leucine catabolism compensates for whatever anabolic inhibition is occurring. Since less leucine i s being degraded, more is available for incorporation and this effect counteracts the process of inhibition of protein synthesis. Once the catabolic inhibition reaches a plateau, the compensation no longer exists, and the inhibition of protein anabolism can assert itself. This hypothesis represents one possibility.Another explanation is offered for the peculiar instance of PEBG-induced inhibition of protein incorporation. I t is possible that there is present in the medium an unknown substance which reacts with the PEBG to form an inactive complex ; inactive toward inhibition of protein synthesis, it would be active toward inhibition of COa release. Once 8 pmoles of PEBG were added, all of the unknown substance would be complexed and further addition of PEBG would result in the sudden drop in incorporation seen in Fig. 2. It was originally thought that this unknown substance might be glucose, since there are 8 pmoles of glucose present in each incubation flask. The data in Table IV show the fallacy of this assumption.Summary. Leucine-C14 was utilized to study the affects of 2 oral hypoglycemic agents (tolbutamide and phenethylbiguanide) on protein metabolism. Both compounds were seen to inhibit CI4O2 production and incorporation of the amino acid into protein by rat liver homogenate. Differences in the mode of inhibition are noted and discussed. Neither compound appears to be dependent on the presence of glucose for its in vitro affects on protein metabolism.
Estimations have been made on abilities of certain tissues of mice injected intravenously with insulin I-131 to concentrate and degrade this compound; change of I-131 from TCA insoluble to TCA soluble form has been used as measure of degradation. Insulin I-131, estimated as TCA insoluble I-131, was concentrated by liver and especially by kidney; formation of TCA soluble I-131 occurred most rapidly in liver. With insulin I-131 held constant but total insulin progressively increased, concentration ratios for TCA insoluble I-131 progressively increased in kidney, and decreased in other tissues. In all tissues, conversion of I-131 from TCA insoluble to TCA soluble form decreased progressively with increase in total insulin. Prior mixing of insulin I-131 with excess guinea pig anti-insulin serum (AIS) resulted in loss of tissue abilities to convert the I-131 into TCA soluble form, and in loss of abilities of all tissues other than liver to concentrate this TCA insoluble I-131.
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