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G A Cook

Publications and source records attributed to G A Cook.

At least 55 records · Page 3Linked to original sources
PubMed1993

Lymphokine expression in granulomas of Schistosoma mansoni-infected mice.

Lymphokine mRNA for IL-2, IL-4, IL-5, IL-10, and IFN-gamma was identified in total RNA, extracted from granuloma and spleen cells of Schistosoma mansoni-infected mice. The specific mRNA in these preparations was identified after reverse transcription and polymerase chain reaction amplification. In some experiments, spleen cells were incubated in the presence of soluble egg antigens or mitogen before RNA extraction. Also, the secretion of these lymphokines from cells maintained in vitro was measured by ELISA or bioassay. The spleen cells from either uninfected or infected mice constitutively released no detectable cytokines and expressed only IL-10 mRNA prominently. Mitogen induced spleen cells from either source to express IL-2 and IFN-gamma mRNAs and their corresponding proteins. Also, spleen cells from noninfected mice stimulated with mitogen expressed IL-4 mRNA, but not IL-5 mRNA, and no detectable protein products. Yet, IL-5 was inducible in spleen cells from infected animals. Soluble egg antigens induced spleen cells from infected mice to prominently express a variety of cytokine genes and produced large amounts of cytokine proteins, but spleen cells from uninfected mice did not respond. Unlike the spleen, the granulomas constitutively expressed mRNAs for all the cytokines examined. Yet, there was limited expression of IL-2 mRNA as compared to that of other cytokines. Except for IL-5, unfractionated granuloma cells constitutively released cytokines at low or undetectable levels. Soluble egg antigens or mitogen enhanced the production of all cytokines to different extents. These observations indicate that schistosome granulomas and spleens express both Th1 and Th2 cytokines. The various lymphokines display complex differences in both lymphokine mRNA and product expression. These results suggest that the production of granuloma lymphokines is governed selectively, possibly by a variety of undetermined regulatory pathways.

Animals↗
PubMed1993

Dietary cholesterol stimulates hepatic biosynthesis of triglyceride and reduces oxidation of fatty acids in the rat.

Experiments were conducted in the intact rat and in the isolated, perfused rat liver to investigate the possibility that the increase in the concentration of hepatic triglyceride and increase in the secretion of the very low density lipoprotein (VLDL)-triglyceride (TG) resulting from addition of cholesterol to the diet are due to stimulation of synthesis of triglyceride, reduced fatty acid oxidation, or both. Male rats were fed for 7 days with either a cholesterol-free diet to which 5% (w/w) corn oil was added, or with the same diet supplemented with 0.5% cholesterol. Fed animals received [1-14C]oleic acid via the tail vein, as a complex with rat serum, and were killed 2 h later. Feeding cholesterol for 7 days increased hepatic triglyceride and cholesteryl ester (CE) concentrations, moderately elevated free cholesterol, but did not affect phospholipid (PL) levels, as we had previously observed after a feeding period of 3 weeks. Incorporation of [1-14C]oleic acid into hepatic and plasma triglyceride increased significantly (60 and 48%, respectively) with cholesterol feeding. Incorporation of [1-14C]oleic acid into hepatic and plasma cholesteryl esters increased by 63 and 79%, respectively, while incorporation into phospholipid was unaffected. Increasing the fat (corn oil) content of the diet to 20% (w/w) did not change these effects of dietary cholesterol. Studies using isolated, perfused rat livers were carried out in vitro after rats were fed the 5% corn oil diet for 3 weeks. [Perfusions lasted 4 h. The perfusion medium contained 3% bovine serum albumin and 30% washed bovine erythrocytes in Krebs-Henseleit-HCO3 buffer.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Carnitine palmitoyltransferase in the heart is controlled by a different mechanism than the hepatic enzyme.

Diminished sensitivity of hepatic carnitine palmitoyltransferase to inhibition by malonyl-CoA in the fasting and diabetic states is a well-recognized aspect of the regulatory mechanism for hepatic fatty acid oxidation. Inhibition of myocardial carnitine palmitoyltransferase by malonyl-CoA may play an important role in regulation of fatty acid oxidation in the heart, but there has been a discrepancy in data relating to changes in malonyl-CoA sensitivity of the myocardial carnitine palmitoyltransferase during fasting. Analysis of malonyl-CoA inhibition of myocardial carnitine palmitoyltransferase in fasting and fed states under a variety of conditions has indicated that under no condition could any difference be found in malonyl-CoA sensitivity that was attributable to fasting. Proteolysis of the outer carnitine palmitoyltransferase led to artifactual changes in sensitivity due to the appearance of partial inhibition. We have concluded that the sensitivity of myocardial carnitine palmitoyltransferase to malonyl-CoA does not change during fasting. Changes in fatty acid oxidation in the heart are probably due to changes in malonyl-CoA concentrations or to other inhibitors.

Animals↗
PubMed1992

Myocardial carnitine palmitoyltransferase of the mitochondrial outer membrane is not altered by fasting.

The regulation of heart carnitine palmitoyltransferase was studied during the transition to the fasting state. Using decanoyl-CoA or palmitoyl-CoA as substrates, we found no differences in carnitine palmitoyltransferase activity or in its sensitivity to inhibition by malonyl-CoA between fed and fasted states. No cooperativity was seen with either substrate, and the malonyl-CoA-induced shift to sigmoid kinetics normally observed with liver mitochondria was not obvious with heart mitochondria. Analysis of malonyl-CoA inhibition data revealed that mitochondria from rat heart exhibited incomplete maximum inhibition of carnitine palmitoyltransferase (partial inhibition). Homogenization of intact liver mitochondria resulted in a similar pattern of incomplete inhibition and suggested that the malonyl-CoA-insensitive carnitine palmitoyltransferase of the inner membrane was also being assayed. Carnitine palmitoyltransferase in mitochondrial outer membranes, isolated from the heart, proved to be extremely sensitive to malonyl-CoA inhibition and had maximum inhibition values of 90-100% with either decanoyl-CoA or palmitoyl-CoA as substrates, but fasting had no effect. Fasting produced no change in the Ki for malonyl-CoA (0.10 +/- 0.04 and 0.14 +/- 0.02 microM for the fed and fasted groups, respectively). Acyl-CoA chain length specificity was C10 greater than C16 greater than C14 greater than C12 greater than C18 = C8 for carnitine palmitoyltransferase in heart mitochondrial outer membranes. It is concluded that the regulation of carnitine palmitoyltransferase of heart mitochondrial outer membranes differs from regulation of the liver enzyme in three characteristics--the heart enzyme (a) has greater sensitivity to malonyl-CoA inhibition, (b) is resistant to the effects of fasting and (c) has somewhat different acyl-CoA substrate specificity.

Animals↗
PubMed1992

Vasoactive intestinal peptide stimulates T lymphocytes to release IL-5 in murine schistosomiasis mansoni infection.

In murine schistosomiasis, granulomas form around ova deposited in the liver and intestines of infected mice. The granulomas have eosinophils that produce vasoactive intestinal peptide (VIP) and T cells that display VIP receptors. IL-5 is a lymphokine important for the development and maturation of eosinophils. It seemed plausible that VIP, released from eosinophils, may interact with lymphocyte VIP receptors and modulate IL-5 production as part of a feedback regulatory circuit. Thus, we determined whether granuloma T cells make IL-5 and whether VIP modulates IL-5 production. Isolated granuloma cells enriched for T lymphocytes spontaneously released IL-5. Culture of these cells in the presence of VIP increased IL-5 secretion. Spleen cells were also studied. Spleen cells from infected mice did not spontaneously release IL-5 or express IL-5 mRNA and VIP did not stimulate these resting spleen cells to produce this IL. However, these cells did express IL-5 mRNA and secreted IL-5 in response to Con A or soluble egg Ag. VIP could not appreciably modulate IL-5 release when cells were cultured with VIP and the Ag or mitogen. Spleen cells washed free of Con A ceased IL-5 secretion within 24 h. These preactivated splenic T cells resumed vigorous IL-5 secretion in response to either Con A or VIP. Yet only Con A prominently induced IL-5 mRNA expression. VIP was an effective stimulus at concentrations equal to or above the kDa of the VIP receptor on both splenic and granuloma T cells (10(-8) M). It is concluded that, in murine schistosomiasis, VIP invokes IL-5 release from activated T cells that are not undergoing immediate TCR stimulation.

Animals↗
PubMed1992

Proteinase treatment of intact hepatic mitochondria has differential effects on inhibition of carnitine palmitoyltransferase by different inhibitors.

Proteolysis of intact mitochondria by Nagarse (subtilisin BPN') and papain resulted in limited loss of activity of the outer-membrane carnitine palmitoyltransferase, but much greater loss of sensitivity to inhibition by malonyl-CoA. In contrast with a previous report [Murthy & Pande (1987) Proc. Natl. Acad. Sci. U.S.A. 84, 378-382], we found that trypsin had no effect on malonyl-CoA sensitivity. Even when 80% of activity was destroyed by trypsin, there was no difference in the malonyl-CoA sensitivity of the enzyme remaining. Trypsin caused release of the intermembrane-space enzyme adenylate kinase, indicating loss of integrity of the mitochondrial outer membrane, whereas Nagarse and papain caused no release of that enzyme. Citrate synthase was not released by any of the three proteinases, indicating no damage to the mitochondrial inner membrane. When we examined the effects of proteolysis on the inhibition of carnitine palmitoyltransferase by a wide variety of inhibitors having different mechanisms of inhibition, we found differential proteolytic effects that were specific for those inhibitors (malonyl-CoA and hydroxyphenylglyoxylate) that have their inhibitory potencies diminished by changes in physiological state. Both of those inhibitors protected carnitine palmitoyltransferase from the effects of proteolysis, but did not inhibit the proteinases directly. Inhibition by two other inhibitors (DL-2-bromopalmitoyl-CoA and N-benzyladriamycin 14-valerate) was not altered by proteinase treatment, even when most of the enzyme activity had been destroyed. Inhibition by glyburide, which is minimally affected by physiological state, was affected only to a slight extent at the highest concentration of trypsin tested. Proteolysis by Nagarse appeared to produce loss of co-operativity in malonyl-CoA inhibition. The effects of proteolysis are discussed and compared with changes in Ki occurring with changing physiological states.

Adenylate Kinase↗
PubMed1992

Murine mucosal T cells have VIP receptors functionally distinct from those on intestinal epithelial cells.

Reports suggest that vasoactive intestinal peptide (VIP) binds to lymphocytes and modulates immune responses. The intestines are richly innervated with VIP-producing nerves. Thus, VIP from nerves or other sources may participate in mucosal immunoregulation. To explore this hypothesis further, murine intestinal mucosal inflammatory cells were scrutinized for functional VIP receptors. An [125I]VIP competitive binding assay characterized VIP receptors. Unfractionated lamina propria inflammatory cells bound [125I]VIP specifically. This binding was abrogated by T cell depletion. The VIP receptor on lamina propria T cells was of a single class with a Kd of 9.08 x 10(-9) M. It bound PHI and other peptide analogs poorly. The intestinal epithelial cell had a high-affinity VIP receptor (Kd 4.17 x 10(-10) M) that bound one VIP analog with moderate affinity. Both VIP and ConA stimulated mucosal inflammatory cells to release interleukin-5 (IL-5). Mucosal inflammatory cells depleted of T cells did not release IL-5 in response to VIP or ConA. It is concluded that: (1) some murine mucosal T lymphocytes have VIP receptors that may be distinct from those displayed on mucosal epithelial cells; (2) VIP affects mucosal T lymphocyte function.

Animals↗
PubMed1992

Potential for hepatic and renal dysfunction during influenza B infection, convalescence, and after induction of secondary viremia.

Whether infection with influenza B virus alters hepatic function was examined in the ferret. Also, the possibility that viral-specific antibodies (Ab) could be produced well before their detection in serum was explored. During the febrile period of influenza, reductions in the serum potassium, anion gap, ammonia, albumin and CPK and elevations of the BUN, creatinine and the GGTP levels occurred. With convalescence, the electrolytes, BUN and creatinine normalized, FFA, SGPT and CPK levels rose and the serum GGTP rose even further. Hepatic fatty acid (FA) oxidation, ornithine transcarbamylase (OTC) and carnitine palmitoyltransferase (CPT) activities were minimally altered and liver ATP and total lipid content remained normal. Following experimental secondary viremia, serum FFA continued to rise, TG decreased and CPK remained elevated while SGPT and GGTP levels normalized. In the liver, FA oxidation and OTC rates remained unchanged but CPT activity was inhibited and the liver content of ATP was significantly reduced. Immune complex (IC) protein recovered from postmicrosomal supernatant fractions by polyethylene glycol precipitation was progressively increased in livers from convalescent and viremic animals. While the amount of IC protein recovered in the spleen also increases during convalescence, this is not the case after viremia when the IC formed seem to be processed largely by the liver. By SDS/PAGE, the major proteins identified in the IC were IgM and other viral proteins. However, the viral proteins could not be validated by immunoblot with Ab produced against purified influenza B hemagglutinin (HA) and neuraminidase (NA) most probably due to phagocytic alterations of glycoprotein immunodeterminants. These findings indicate that during influenza, convalescence and post viremia changes in the concentrations of several serum and liver components occur that reflect hepatic involvement. Also, antiviral Ab, largely IgM, appears to be produced early, complexes with Ag and can be found sequestered in both the liver and spleen at a time when Ab is not detectable in the serum.

Adenosine Triphosphate↗
PubMed1991

Malonyl-CoA inhibits proteolysis of carnitine palmitoyltransferase.

Incubation of isolated mitochondria in the presence of malonyl-CoA prevented proteolysis of the outer carnitine palmitoyltransferase by Nagarse and trypsin. Malonyl-CoA had no direct action on trypsin when present in a chromogenic assay system for proteolysis or when preincubated with the proteases in the absence of mitochondria. As reported previously, Nagarse had a differential effect on carnitine palmitoyltransferase in which malonyl-CoA inhibition was diminished to a greater extent than activity was lost, but all effects were blocked by malonyl-CoA in a concentration-dependent manner. These data suggest a specific effect of binding of malonyl-CoA to carnitine palmitoyltransferase as the protective mechanism.

Animals↗
PubMed1991

Substance P does not alter interleukin-1 expression by splenic or granuloma macrophages in murine schistosomiasis.

Substance P (SP) is an undecapeptide with neurotransmitter and immunoregulatory properties. In murine schistosomiasis, ova naturally induce liver and intestinal granulomas. These granulomas contain macrophages, and eosinophils that produce SP. A report showed that human blood monocytes isolated by adherence release interleukin-1 (IL-1) in response to SP (Lotz et al. (1989) Science 241, 1218). IL-1 is important for initiation of hypersensitivity granulomas. Therefore, it was determined whether SP modulates granuloma macrophage IL-1 production in murine schistosomiasis. Macrophages were obtained from lung and liver granulomas, and from spleens of infected mice. A thymocyte proliferation assay measured IL-1 activity in culture supernatants. Total RNA, extracted from macrophages, was assayed for IL-1 alpha and beta mRNA by Northern blotting using cDNA probes. In response to lipopolysaccharide (LPS), splenic macrophages and macrophages from young lung granulomas released appreciable IL-1. Macrophages from liver granulomas, that were lesions older than the lung granulomas, were unresponsive to LPS with regard to IL-1 secretion. Yet, granuloma macrophages spontaneously expressed IL-1 alpha and beta mRNA. LPS enhanced IL-1 mRNA expression in both splenic and granuloma macrophages. Exposure of macrophages from all sources to SP did not alter IL-1 secretion or gene expression. Similarly, the responsiveness of macrophages to LPS was not affected by concomitant exposure to SP. It is concluded that, in the murine system, SP does not directly influence splenic or granuloma macrophage IL-1 secretion or gene expression. Also, it appears that macrophage secretion of IL-1 is rapidly down-regulated following granuloma elicitation.

Animals↗
PubMed1991

Acute alterations in the regulation of lipid metabolism after intravascular reexposure to a single bolus of homologous virus during influenza B infection in ferrets: possible model of epiphenomena associated with influenza.

Metabolic responses occurring 24 h following the secondary haematogenous dissemination of influenza B virus during convalescence from infection were examined in the ferret as a possible model for epiphenomena which can occur following infection with influenza. Among the major changes found were a further rise in the mean fasting serum free fatty acid (FFA) level to three times the control mean value and a 50% drop in the mean serum triglyceride (TG) concentration after the intravascular administration of a single bolus of virus compared to levels found in uninfected or convalescent animals. In adipose tissue, hormone-sensitive and lipoprotein lipase activities were increased six and three-fold, respectively, over mean control values, probably accounting for the changes that were observed in serum lipid concentrations. In the liver, total carnitine palmitoyltransferase (CPT) activity was affected only slightly and the total lipid content of the liver remained unchanged. These findings indicate that 24 h after the intravascular dissemination of homologous virus in a single bolus during convalescence from influenza B infection, major distortions in the regulation of lipid metabolism occur in the ferret. Loss of the synchronous regulation of the two adipose tissue lipases is a significant consequence leading to the mobilization of a large amount of FFA during fasting from both adipose tissue and the circulating plasma TG stores.

Adipose Tissue↗
PubMed1990

Inhibition of mitochondrial carnitine palmitoyltransferases by adriamycin and adriamycin analogues.

Adriamycin (ADR; doxorubicin) and its highly lipophilic, less toxic analogue N-benzyl-adriamycin-14-valerate (AD 198) were found to inhibit rat heart and liver carnitine palmitoyltransferases of both mitochondrial outer and inner membranes. The outer membrane enzyme was more sensitive to inhibition by these drugs than the inner membrane enzyme, and AD 198 was a more potent inhibitor of these enzymes than ADR. Other analogues of ADR, N-trifluoroacetyladriamycin-14-valerate (AD 32) and N-trifluoroacetyladriamycin-14-O-hemiadipate (AD 143), which are documented as being noncardiotoxic, were also more potent inhibitors of the mitochondrial carnitine palmitoyltransferases than ADR. Overall, the cardiac mitochondrial carnitine palmitoyltransferases seemed to be slightly more sensitive to the inhibitory effects of ADR and its analogues than the liver enzyme. ADR was an uncompetitive inhibitor with respect to palmitoyl-CoA and a noncompetitive inhibitor with respect to carnitine for both mitochondrial outer and inner membrane enzymes. Our data suggest that mitochondria can take up ADR and concentrate it within the matrix, as is known to happen with other positively-charged compounds. More ADR was found associated with the mitochondrial inner membrane than with the outer membrane; this could be due to the greater protein content of the inner membrane rather than drug binding to cardiolipin. Although inhibition of cardiac inner membrane carnitine palmitoyltransferase has been implicated previously as part of the cardiotoxicity mechanism of ADR, the present findings with ADR and its noncardiotoxic analogues do not support this view.

Animals↗
PubMed1990

The gene family encoding eggshell proteins of Schistosoma japonicum.

The four closely related genes encoding eggshell proteins in the human parasite Schistosoma japonicum are described. A cDNA and a genomic DNA library were constructed and members of the eggshell protein gene family isolated. The four genes in this family do not contain introns, and differ in organization and nucleotide sequence from the related set of genes in Schistosoma mansoni and Schistosoma haematobium. The coding sequences of two of the S. japonicum genes and their flanking regions were determined. Transcription start sites for these genes were shown by primer extension analysis to occur 47 and 50 nucleotides in front of the start codon. A female-specific component in nuclear extracts binds to a DNA fragment containing conserved sequences upstream of the transcription start sites. The deduced protein sequences of 207 and 212 amino acids are composed of 50% glycine with continuous glycine regions as long as 11 residues. In vitro translations of male and female RNAs revealed female-specific translation products, the sizes of which were consistent with the eggshell proteins.

Amino Acid Sequence↗