Stretch increases inositol trisphosphate and inositol tetrakisphosphate in cultured pulmonary vascular smooth muscle cells.

There are no reports of the effect of stretch on inositol phosphates in smooth muscle. Phosphoinositide and inositol phosphate metabolism was studied in cultured rat vascular smooth muscle cells subjected to stretching. The masses of inositol trisphosphate and tetrakisphosphate increased (+34 +/- 7% and +58 +/- 12%, respectively; p less than 0.001) after 25 s of a single 20% stretch and had returned to control levels by 45 s; phosphatidylinositol, phosphatidylinositol phosphate and bisphosphate did not change. Repetitive stretch did not alter the masses of any of the compounds. A single stretch also increased 45Ca2+ efflux (+52 +/- 5%, p less than 0.01). These data suggest that stretch of cultured vascular smooth muscle can elicit a rapid, short-lived increase in inositol phosphates, which may subsequently affect Ca2+.     

Nonparallel transport and mechanisms of secretion.

After many years of controversy, it is now clear that at least some cells and tissues that secrete more than one product can vary the composition of the secreted mixture as the result of the differential transport of various substances out of the cells that secrete them. In this article we discuss this phenomenon, non-parallel transport or secretion, and how it has and continues to inform us about how cells release the products they manufacture. We focus on expression of the phenomenon in the secretion of digestive enzymes by the exocrine pancreas, where it has been studied most extensively.     

Structure-activity relationship of the neurotransmitter alpha-bag cell peptide on Aplysia LUQ neurons: Implications regarding its inactivation in the extracellular space

Alpha-bag cell peptide [α-BCP (Ala-Pro-Arg-Leu-Arg-Phe-Tyr-Ser-Leu)] is a neurotransmitter that mediates bag cell-induced inhibition of left-upper-quadrant (LUQ) neurons L₂, L₃, L₄, and L₆ in the abdominal ganglion of Aplysia. Our recent biochemical studies have shown that α-BCP[1–9] is cleaved into α-BCP[1–2], [3–9], [1–5], [6–9], and [7–9] by a combination of three distinct peptidase activities located within the extracellular spaces of the CNS: A diaminopeptidase-IV (DAP-IV)-like enzyme cleaves α-BCP[1–9] at the 2–3 peptide bond; a neutral metalloendopeptidase (NEP)-like enzyme cleaves either α-BCP[1–9] or α-BCP[3–9] at the 5–6 bond; an aminopeptidase M-II (APM-II)-like enzyme cleaves α-BCP[6–9] at the 6–7 bond, but cleaves neither α-BCP[1–9], nor the other ganglionic peptidase products. To further understand the manner in which α-BCP is inactivated after release, that is loses its electro-physiological activity, we studied its structure-activity relationship by recording intracellularly from LUQ neurons in isolated abdominal ganglia that were arterially perfused with peptides dissolved in artificial sea water. The effects of α-BCP[1–9] and 15 of its fragments ([1–8], [1–7], [1–6], [1–5], [2–9], [3–9], [3–8], [6–9], [7–9], [8–9], [6–7], [6–8], [1–2], Phe, Tyr) indicated that the sequence Phe⁶-Tyr⁷ was both necessary and sufficient to produce LUQ inhibitory activity. The combined results of our electrophysiological and biochemical studies strongly suggest that α-BCP[1–9] is inactivated by the serial actions of the NEP-like and APM-II-like peptidases; that is, the NEP-like enzyme yields an electro-physiologically active product, α-BCP[6–9], that is cleaved by the APM-II-like enzyme to yield inactive α-BCP[7–9]. Furthermore, because α-BCP[6–9] is more active than α-BCP[1–9], cleavage by the NEP-like enzyme potentiates α-BCP's activity. © 1992 John Wiley & Sons, Inc.     

The c1 repressor of bacteriophage P1: I. Isolation of the c1 protein and determination of the P1 DNA region to which it Binds

A bacteriophage P1-specific DNA binding protein has been partially purified from P1-infected Escherichia coli and identified as the P1c1 repressor. This protein is absent from non-suppressing cells infected with a P1c1 amber mutant. The binding activity of the protein isolated from cells infected with a c1ts mutant is thermolabile in vitro, so the repressor protein is the product of the c1 gene. Studies on P1 DNA fragments generated by restriction endonuclease digestion indicate that the c1 repressor binds preferentially in vitro at a site or sites located close to the c1 gene itself.     

Delayed-type cutaneous hypersensitivity to melanoma antigens and its implication in active specific immunotherapy in cancer

Summary In this study, we explored whether soluble tumor-cell surface-associated antigens (TAA) might be derived from autochthonous as well as allogeneic sources as immunogens for active specific immunotherapy. Using two popular cell membrane-bound antigen extraction techniques (3 M KCl and isotonic-hypotonic NaCl), we examined the immunogenic potential of such TAA and the specificity of immunologic host reactivity through a delayed-type cutaneous hypersensitivity reaction (DTH) as a guideline for their immunogenic potential in a human malignant melanoma model system. We found that either extraction technique could provide soluble TAA from both autochthonous and allogeneic sources capable of eliciting DTH. While evidence of positive DTH with autochthonous TAA reaffirms the immunogenicity of such TAA, the specificity of host reactivity against TAA derived from allogeneic sources is extremely difficult to establish, even with TAA partially purified by column chromatography in Sephadex G-200. Patients exhibited reactivity to other TAA derived from tumors of different histologies and often to more than one component isolated by column chromatography. Furthermore, when a group of melanoma patients was tested against a panel of melanoma antigens in any random combination, DTH to allogeneic TAA was seen in an unpredictable order and with inconsistent frequency. We conclude, therefore, that while autochthonous antigen immunizations may be justified, more careful studies will be necessary to define the antigenic profile of a given tumor (individual specificity vs shared specificity), establish specificity of alloantigens, and devise suitable methods for testing immunologic specificity for alloantigens, before rational immunotherapy with allogeneic tumor antigens will be feasible.     

Fusion and protein-mediated phospholipid exchange studied with single bilayer phosphatidylcholine vesicles of different density

A novel method has been developed for the study of phospholipid exchange and fusion of phospholipid vesicles. Two homogeneous populations of single bilayer phosphatidylcholine vesicles of similar size but markedly different density have been prepared. /ldDense/rd vesicles were made from brominated dioleoyl phosphatidylcholine. /ldLight/rd vesicles were prepared from dioleoyl phosphatidylcholine. The two populations were easily separated by density gradient centrifugation. Phosphatidylcholine exchange protein from beef liver was used to promote lecithin exchange between the vesicle populations. Only the lecithin of the external monolayers of the vesicles was available for exchange by exchange protein, implying that flip-flop of vesicle phosphatidylcholine did not take place at a detectable frequency. No spontaneous intervesicle phosphatidylcholine exchange was observed. However, the dense and light vesicles did spontaneously fuse, over several hours, to produce particles of hybrid density.     

Hypothetical Outcome Plots Outperform Error Bars and Violin Plots for Inferences about Reliability of Variable Ordering

Many visual depictions of probability distributions, such as error bars, are difficult for users to accurately interpret. We present and study an alternative representation, Hypothetical Outcome Plots (HOPs), that animates a finite set of individual draws. In contrast to the statistical background required to interpret many static representations of distributions, HOPs require relatively little background knowledge to interpret. Instead, HOPs enables viewers to infer properties of the distribution using mental processes like counting and integration. We conducted an experiment comparing HOPs to error bars and violin plots. With HOPs, people made much more accurate judgments about plots of two and three quantities. Accuracy was similar with all three representations for most questions about distributions of a single quantity.     

Neurotoxicity,drugs of abuse,and the CuZn-superoxide dismutase transgenic mice

Administration of methamphetamine (METH) to animals causes loss of DA terminals in the brain. The manner by which METH causes these changes in neurotoxicity is not known. We have tested the effects of this drug in copper/zinc (CuZn)-superoxide dismutase transgenic (SOD Tg) mice, which express the human CuZnSOD gene. In nontransgenic (non-Tg) mice, acute METH administration causes significant decreases in DA and dihydroxyphenylacetic acid (DOPAC) in the striata of non-Tg mice. In contrast, there were no significant decreases in striatal DA in the SOD Tg mice. The effects of METH on DOPAC were also attenuated in SOD Tg mice. Chronic METH administration caused decreases in striatal DA and DOPAC in the non-Tg mice, but not in the SOD-Tg mice. Similar studies were carried out with 1-methyl-1,2,3,6-tetrahydropyridine (MPTP), which also causes striatal DA and DOPAC depletion. As in the case of METH, MPTP causes marked depletion of DA and DOPAC in the non-Tg mice, but not in the SOD Tg mice. These results suggest that the mechanisms of toxicity of both METH and MPTP involve superoxide radical formation.