scholarly journals Preparation of [B23-d-alanine]des-(B25-B30)-hexapeptide-insulin by a combination of enzymic and non-enzymic synthesis

1983 ◽  
Vol 215 (3) ◽  
pp. 697-699 ◽  
Author(s):  
Y S Zhang ◽  
Q P Cao ◽  
Z G Li ◽  
D F Cui
Keyword(s):  
Biological Activity ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Enzymic Synthesis

Des-(B25-B30)-hexapeptide-insulin with B23-glycine replaced by D-alanine was prepared by a combination of enzymic and non-enzymic syntheses. The purified product was homogeneous in polyacrylamide-gel electrophoresis and could be crystallized. The biological activity in vivo of crystalline [B23-D-Ala]des-(B25-B30)-hexapeptide-insulin was determined as 58% of that of standard pig insulin (27 i.u./mg).

In-vivo and in-vitro secretion of prolactin by lactating rat adenohypophyses as a function of intracellular age

1984 ◽  
Vol 101 (1) ◽  
pp. 27-32 ◽  
Author(s):  
F. Mena ◽  
G. Martínez-Escalera ◽  
C. Clapp ◽  
C. E. Grosvenor
Keyword(s):  
Pituitary Gland ◽  
Incubation Period ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Polyacrylamide Gel ◽  
Pituitary Glands ◽  
H 26

ABSTRACT Adenohypophysial prolactin of lactating rats was pulse-labelled by [3H]leucine injected i.v. at the time of removal of the pups. The [3H]prolactin concentration in the pituitary gland, analysed by polyacrylamide-gel electrophoresis, progressively fell as the time from labelling to removal of the pituitary gland increased from 8 to 24 h, which suggests that there was a loss of hormone as it aged within the gland. Suckling effectively provoked the depletion–transformation of total and [3H]prolactin (extracted at pH 7·2) when applied after 8 h but not when applied after either 16 or 24 h after removing the pups. In rats whose pups were removed for 8 h, suckling also depleted–transformed [3H]prolactin labelled 4 h, but not that labelled 1 h before suckling. The pituitary glands of other lactating rats were labelled with [3H]leucine injected i.v. at various times before removing the glands and incubating them in medium 199. The secretion into the medium of [3H]prolactin labelled either 4, 8, 16 or 24 h beforehand was maximal during the first 30 min then declined from 30 to 240 min of incubation. However, secretion of prolactin labelled 1 h and 10 min beforehand reached a maximum after 0·5–1 h and 2 h of incubation respectively, then remained constant during the remainder of the 4-h incubation period. The total 4-h secretion of [3H]prolactin was greatest (65% of preincubation concentration) from those glands labelled 4 h before in contrast to those labelled 10 min (15%) or 1 (38%), 8 (34%), 16 (18%) or 24 h (26%) before incubation. Taken together, these data suggest that prolactin synthesized 4 h earlier is more likely to be released in response to physiological stimuli than is more recently formed prolactin or prolactin which has remained in the pituitary gland for 16 h or longer. J. Endocr. (1984) 101, 27–32

Studies of the Metabolism of Asialotransferrins: Evidence that Transferrin Does not Undergo Desialylation in Vivo

1974 ◽  
Vol 46 (6) ◽  
pp. 763-774
Author(s):  
K.-L. Wong ◽  
P. A. Charlwood ◽  
M. W. C. Hatton ◽  
E. Regoeczi
Keyword(s):  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Biological Significance ◽  
Polyacrylamide Gel ◽  
Fractional Catabolic Rate ◽  
Sialic Acid Content ◽  
Catabolic Rate ◽  
Bovine Transferrin

1. Experiments are reported which aimed at determining whether transferrin loses sialyl residues from the carbohydrate side-chains during the biological lifetime of the molecule. To explore this possibility, transferrin fractions of relatively high sialic acid content (referred to as sialotransferrin) were prepared from purified rabbit and bovine transferrin by preparative polyacrylamide-gel electrophoresis. After labelling with 125I, the preparations were injected into a group of three rabbits each. From the plasma samples obtained between 1 h and 6–8 days after injection, transferrin was partially purified, mixed with 131I-labelled asialotransferrin of the corresponding species and run in preparative polyacrylamide-gel electrophoresis. In each specimen examined, the 125I radioactivity migrated ahead of the marker asialotransferrin, and no portion of the dose was detected with the electrophoretic mobility of asialotransferrin. 2. Evidence is presented that bovine transferrin desialylated in vitro remains detectable in the plasma of rabbits for intervals which are comparable with those found in previous studies with rabbit asialotransferrin. 3. A mathematical model is described for the computation of asialo- to sialotransferrin radioactivity ratios in the plasma, continuous desialylation of pulse-injected sialotransferrin being assumed. Calculations were made at various hypothetical rates of desialylation. 4. On the basis of the experimental data and the model it is concluded that transferrin (both rabbit and bovine) is not subjected to systematic desialylation in rabbits. Random desialylation of some transferrin could take place at rates less than 5% of the fractional catabolic rate of transferrin, which would be without any biological significance.

Isolation and Analysis of Non-Histone Chromatin Proteins from Rat-Liver Nuclei by Three Different Methods

1974 ◽  
Vol 52 (12) ◽  
pp. 1143-1153 ◽  
Author(s):  
D. Suria ◽  
C. C. Liew
Keyword(s):  
Rat Liver ◽  
Gel Electrophoresis ◽  
Polyacrylamide Gel Electrophoresis ◽  
Soluble Proteins ◽  
Polyacrylamide Gel ◽  
Pulse Labelling ◽  
Rat Liver Nuclei ◽  
Liver Nuclei ◽  
Chromatin Proteins

Non-histone chromatin proteins were isolated from rat-liver nuclei by three different methods, and defined as (I) phenol-soluble proteins, (II) SDS-soluble proteins and (III) proteins not adsorbed by cation-exchange chromatography. About 62–70% of chromatin proteins were recovered from the total nuclear proteins. The yield of non-histone chromatin proteins varied from 17 to 26% of chromatin proteins, depending on the method used. The amino-acid composition of these proteins showed that they are acidic in nature. Their phosphorus content was found to be 0.9, 1.1, and 1.4%, respectively, according to method I, II, or III. In-vivo pulse-labelling experiments indicated that chromatin proteins were highly labelled with 3H-acetate and 32P-phosphoric acid. In particular, the specific activities of 32P incorporation were higher in all non-histone chromatin proteins isolated as compared with histones. One-dimensional SDS–polyacrylamide gel electrophoresis showed that at least 26 similar fractions can be detected in the samples prepared by these three methods.The similarity of some of the proteins obtained from methods I and III was further confirmed by fractionation of the non-histone chromatin proteins in an isoelectro-focusing system followed by a second-dimensional SDS–polyacrylamide gel electrophoresis. It was found that more than 100 components could be identified. However, some minor variations of the non-histone chromatin proteins were detected by this system. The differences in proteins isolated by these methods are mainly quantitative rather than qualitative. The methods examined are not specific for the fractionation of a certain class of non-histone chromatin proteins.

scholarly journals Vitellogenesis in the stick insect Carausius morosus I. Specific protein synthesis during ovarian development

1980 ◽  
Vol 46 (1) ◽  
pp. 1-16
Author(s):  
F. Giorgi ◽  
F. Macchi
Keyword(s):  
Amino Acids ◽  
Molecular Weight ◽  
Protein Synthesis ◽  
Gel Electrophoresis ◽  
Fat Body ◽  
Polyacrylamide Gel Electrophoresis ◽  
Stick Insect ◽  
Polyacrylamide Gel ◽  
Carausius Morosus

Vitellogenesis in the stick insect Carausius morosus (Br.) has been studied with the goal of identifying vitellogenin in various tissues. Following exposure to in vivo to radioactive amino acids, oocytes in the medium size range are labelled with a minimum delay of 6 h after the time of injection. Incorporation of radioactivity under these conditions is shown to depend upon accumulation of proteins rather than on a differential rate of protein synthesis in succeeding stages of oogenesis. By immunochemical analyses, it is shown that at least two antigens are common to both haemolymph and ovary and that one of these is also present in the fat body. Both antigens are labelled during exposure to radioactive amino acids. When analysed by the SDS polyacrylamide gel electrophoresis, extracts from both haemolymph and ovary appear to share a number of protein fractions which range in molecular weight from 40 000 to 200 000 Daltons. The labelling pattern exhibited by these fractions is clearly indicative of a protein transfer from the fat body to the oocyte. Fat body cultured in vivo for up to 4 h releases a major macromolecular complex in the external medium. The latter has been identified as vitellogenin by both immuno-precipitation assay and SDS polyacrylamide gel electrophoresis. The protein which is synthesized and secreted under these conditions results from the processing of a protein complex of higher molecular weight.

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