Block of axoplasmic transport in vitro by vinca alkaloids

The three potent antimitotic vinca alkaloids: vincristine (VCR), vinblastine (VLB), and vindesine (VDS) were compared for their effect in blocking axoplasmic transport in vitro using a desheathed preparation of the peroneal branch of cat sciatic nerve. A range of vinca alkaloid concentrations from 1–100μM was examined. The relative order of potency in blocking axoplasmic transport was VCR > VLB > VDS at a concentration of 25μM. At the higher concentrations block occurred so rapidly that a statistically significant difference between these agents could not be obtained. The relation of vinca block ot the transport mechanism is discussed.     

Initial synthesis of globin peptide chains in differentiating embryonic red blood cells

The initial time of synthesis of globin polypeptide chains in differentiating red cells has been delineated. Three analytical techniques were used, namely, SDS-polyacrylamide gel electrophoresis, acid urea polyacrylamide gel electrophoresis, and two-dimensional gel electrophoresis. The results indicate that globin peptide chains are synthesized in proerythroblasts at the initial time when globin mRNA first enters into the cytoplasm, and there is no apparent time gap between these two events.     

Toxic shock syndrome in a patient with systemic lupus erythematosus.

A case is presented of toxic shock syndrome in a patient with systemic lupus erythematosus. Toxic shock syndrome is rarely reported in patients who are immunosuppressed, perhaps because such patients are often treated vigorously with antibiotics at the earliest sign of infection. The association in this case may have been coincidental.     

Sequential passage of alpha2mu-globulin through the hepatic endoplasmic reticulum and Golgi apparatus during secretion.

Studies on the synthesis and secretion of the sex-dependent urinary protein, alpha2mu-globulin, have been extended by establishing its sequential passage from the rough to the smooth endoplasmic reticulum and Golgi-rich fractions of the liver of adult male rats. After injection of 14C-labeled amino acids, the maximum radioactivity of alpha2mu occurred at 20 min in the rough, 25 min in the smooth microsomes and 30 or 35 min in the Golgi-rich fractions. Radioactive alpha2mu-globulin appeared in the bloodstream and kidneys after a lag of 20--25 min. Results indicate that alpha2mu-globulin follows a secretory pathway similar to that of serum albumin.     

The effect of repetitive haemorrhage on plasma cortisol, beta-endorphin and N-terminal pro-opiomelanocortin in conscious sheep

We measured the effect of repeated haemorrhagic stress, performed on four consecutive days in conscious adult sheep, on the plasma concentrations of cortisol and ACTH-related peptides to determine whether the pituitary-adrenal response was altered by stress repetition. Peptides from the C-terminus of the ACTH pro-hormone was measured by beta-endorphin RIA. Glycopeptides derived from the N-terminus of the ACTH pro-hormone were measured by tau 3-MSH RIA. The immunoreactive tau 3-MSH in sheep plasma was found to have an apparent molecular weight of approximately 10,000 by gel chromatography through Sephadex G-75, which is similar to the size of the major circulating form of pro-tau-MSH found in human and rat plasma. Daily haemorrhage consistently elevated plasma concentrations of cortisol and pro-tau-MSH. There was no significant difference in the daily responses of either cortisol or pro-tau-MSH when considered individually. However, there was a significant change over the four days in the relationship between the cortisol and pro-tau-MSH responses, as judged by analysis of variance of the difference in daily z-scores of cortisol and pro-tau-MSH. This trend indicated a relative increase in the secretion of pro-tau-MSH from the pituitary compared to the cortisol response, and suggested that repeated exposure to stressful stimuli may alter the pituitary-adrenal-axis.     

Insertion of a foreign nucleotide sequence into mitochondrial DNA causes senescence in Neurospora intermedia

The kalilo variants of Neurospora contain a cytoplasmic genetic factor that causes senescence. This factor is a 9.0 kb transposable element (kalDNA) that lacks nucleotide sequence homology with mtDNA and is inserted into the mitochondrial chromosome, often at sites located within the open reading frame in the intron-DNA of the mitochondrial 25S-rRNA gene. Genomes containing the "foreign" DNA insert accumulate during growth, and death occurs as the cells become deficient in functional large and small subunits of mitochondrial ribosomes. The kalDNA transposon may be an "activator" element that causes breaks in mtDNA. Nonsenescing [+] strains of Neurospora do not contain kalDNA.     

Acrosomal enzymes of human spermatozoa before and after in vitro capacitation

The effect of in vitro capacitation (events that occur before the acrosome reaction) on the acrosomal enzymes of human spermatozoa was determined. Capacitation of human spermatozoa was assessed by their ability to penetrate denuded hamster oocytes. The activities of a number of enzymes commonly associated with the sperm acrosome, including nonzymogen acrosin, proacrosin, inhibitor-bound acrosin, hyaluronidase, acid phosphatase, beta-glucuronidase, beta-glucosidase, beta-N-acetylglucosaminidase, beta-galactosidase and beta-N-acetylgalactosaminidase were assessed. With the exception of acid phosphatase, no alteration in enzyme activity occurred after 4 h of incubating the spermatozoa under capacitation conditions although gamete fusion took place. The acid phosphatase levels decreased twofold, presumably due to the loss of seminal (prostatic acid phosphatase that loosely adheres to spermatozoa. After 8 h of capacitation, a large decrease in sperm enzyme levels took place only in the case of hyaluronidase, although small decreases were also noted in total acrosin, proacrosin and inhibited acrosin. No new electrophoretically migrating forms of acrosin were observed. Decreases in total acrosin and proacrosin, but not in inhibited acrosin, also occurred when spermatozoa were incubated under noncapacitating conditions for 8 h, indicating that capacitation may specifically cause the release of some acrosin inhibitor from human spermatozoa. It is concluded that, with the possible exception of hyaluronidase, the in vitro capacitation of human spermatozoa does not cause a major change in its acrosomal enzyme content so that these hydrolases are fully present before the acrosome reaction takes place during gamete fusion. Serum albumin appears to protect against the loss of some of these enzymes since the activity of several glycosidases was significantly reduced when the spermatozoa were incubated for 8 h in human serum albumin-free medium.     

Complexation and phase transfer of nucleotides by gramicidin S

Gramicidin S (GrS), an amphiphilic cyclosymmetric decapeptide produced by Bacillus brevis G-B and Nagano, binds nucleotides in water to yield a complex which partitions into organic solvents. The observed phase-transfer efficiencies at a given pH increase in the order AMP less than ADP less than ATP. The lipophilic complexes have well-defined stoichiometries, which were determined to be 1:1 for ADP-GrS at pH 7 and ATP-GrS at pH 3 and 1:2 for ATP-GrS at pH 7. The interaction is primarily ionic, involving coordination of the ornithine N delta H3+ groups of the peptide and the phosphoryl groups of the nucleotide, with little contribution from the nucleoside moiety. Exchange of organic and inorganic phosphates was also found to be mediated by GrS. The nucleotide complexes are sparingly soluble in water and self-associate extensively in CHCl3, most likely by cross-beta-aggregation, to yield large, ribbonlike aggregates which give rise to broad NMR resonances. Structures for the 1:1 and 1:2 complexes are proposed. In the latter, two GrS molecules envelop the nucleotide, orienting their apolar faces externally in opposite directions, while the lateral faces retain considerable polar character and direct aggregation in organic media. The 1:1 complex possesses a single apolar face and is less lipophilic. Binding constants were estimated by simulation of the extraction data. For the 1:1 complexes, K1:1 congruent to 4 X 10(4) M-1 for either ADP or ATP. Phase transfer of the ATP complex at pH 7 could be modeled either by stochastically independent binding to two noninteracting sites on the nucleotide with K1 approximately K2 approximately K1:1 or by a sequential process with K1 approximately K1:1 and K2/K1 less than 100. It is concluded that the apparent selectivity of GrS for ATP over ADP is a consequence of the greater lipophilicity and tendency to aggregate of the 1:2 complex, rather than an intrinsically higher binding affinity for triphosphates. GrS is, to our knowledge, the first peptide known to possess phase-transfer activity toward nucleotides; this is, in addition, the first molecular recognition process in which GrS is demonstrated to participate in vitro at physiologically active concentrations.