ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143934

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

The article assembles and elaborates evidence which indicates that an ‘old’ enzyme, oxalate oxidase, and an even ‘older’ substrate, calcium oxalate, have significant and previously uncontemplated roles in the biochemistry of the extracellular matrix (ECM) of higher plants. These possibilities emerged by chance, but not really by chance, when computerized comparisons of amino acid sequences inevitably led to the discovery that germin, long known to be a protein marker of the onset of growth in germinating wheat, and later known to be an ECM protein, is an oxalate oxidase [J. Biol. Chem.268, 12239‐12242 (1993)]. Dissolution of calcium oxalate, and germin‐induced degradation of the resulting soluble oxalate, can release Ca2+and H2O2, both of which are known to have central roles in the biochemistry of the ECM in higher plants. It is therefore timely to survey the implications of the recent finding that germin is an oxalate oxidase in the context of how oxalate may participate not only in the biochemistry of the ECM, but in the development of higher plants. The findings about oxalate, as a source of H2O2, are a complement to Varner's contemporaneous advocacy of a central role for H2O2in the development, differentiation, vascularization and signaling processes of higher plants.—Lane, B. G. Oxalate, germin, and the extracellular matrix of higher plants.FASEB J.8: 294‐301; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143935

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Stability of body composition requires that energy intake equals energy expenditure when integrated over prolonged periods. As recent human studies have failed to demonstrate active changes in energy expenditure with changes in body composition, it is likely that energy intake is continually adjusted to preserve a constant total adipose tissue mass. If adipose tissue mass is regulated directly, then there must be some input reflecting this quantity to the central nervous system for the purpose of making corrective changes in appetite when total body fat content fluctuates. The nature of this input has been examined in a variety of animal experiments involving induced weight change, lipectomy, plasma transfer from obese or satiated animals to hungry animals, and parabiosis between obese and lean animals. The bulk of evidence suggests that the plasma level of one or more currently unidentified stable circulating molecules increases in proportion to total body fat content and augments the effect of meal‐related satiety signals in the central nervous system. The implications of this adipose tissue‐related satiety factor for the pathogenesis of obesity, and the possible nature of the factor are discussed.—Weigle, D. S. Appetite and the regulation of body composition.FASEB J.8: 302‐310; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143936

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Knowledge of the molecular mechanisms involved in chemomechanical transduction and the regulatory elements determining contraction and relaxation are largely derived from cross‐striated muscle. However, it has become clear that vertebrate smooth muscles have features lacking in striated muscle. These derive from regulated crossbridge cycling rates observed as variable shortening velocities and ATP consumption rates. The special properties of smooth muscle are associated with differences in the physiological roles of muscle in the walls of hollow organs and reflect a common molecular motor governed by different regulatory mechanisms. A remarkably simple scheme involving Ca2+‐dependent phosphorylation of crossbridges in smooth muscle can predict much of the mechanical and energetics behavior characterizing the muscle of hollow organs. Nevertheless, many unresolved issues are identified that are the focus of current research efforts.—Murphy, R. A. What is special about smooth muscle? The significance of covalent crossbridge regulation.FASEB J.8: 311‐318; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143937

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Considerable attention has been focused on the purine nucleoside, adenosine, in the control of renal blood flow, epithelial transport, and renin secretion; however, surprisingly little attention has been directed toward the renal effects of purine nucleotides such as adenosine triphosphate (ATP). Recent studies utilizing in vivo micropuncture and in vitro techniques have demonstrated that renal vascular, epithelial, and mesangial cells respond to extracellular ATP via mechanisms distinct from those elicited by adenosine. ATP vasoconstricts afferent but not efferent arterioles whereas adenosine vasoconstricts both vascular segments. Adenosine‐mediated afferent arteriolar vasoconstriction is abolished by adenosine receptor antagonists, whereas the response to ATP is enhanced. ATP‐mediated vasoconstriction reaches a maximum within seconds of exposure while the vasoconstriction induced by adenosine develops more slowly. L‐type calcium channel antagonists such as diltiazem or felodipine prevent the sustained afferent vasoconstriction produced by ATP. Data from micropuncture experiments indicate that peritubular capillary infusion of ATP reduces glomerular pressure and results in marked attenuation of the tubuloglomerular feedback mechanism, which transmits signals from the macula densa to the afferent arteriole. These data support the existence of ATP‐sensitive P2purinoceptors in the preglomerular microvasculature that contribute to the control of renal vascular function via activation of calcium channels.—Inscho, E. W., Mitchell, K. D., Navar, L. G. Extracellular ATP in the regulation of renal microvascular function.FASEB J.8: 319‐328; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143938

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Two types of collagens have been identified inCaenorhabditis eleganscorresponding to two types of extracellular matrix, the cuticle and basement membranes. Cuticle collagens are encoded by a developmentally regulated family of ~100 genes. Mutations in cuticle collagens can produce animals that are longer or shorter than normal and/or that are helically twisted. Mutations in different collagens can cause different morphological abnormalities, as can different mutations in the same collagen. Genetic interactions between collagen genes have been described and may identify collagens that interact to form the cuticle. Two basement membrane (type IV) collagen genes have been identified inC. elegans.They encode proteins similar in structure to vertebrate type IV collagen. One of the genes produces two alternatively spliced forms, one predominantly expressed in embryos and the other in larvae and adults, suggesting that embryonic basement membranes may have unique properties. Most mutations in the type IV genes cause embryonic lethality, indicating that normal basement membranes are required for embryogenesis. Temperature‐sensitive mutations have been used to show that type IV collagen function is also required for larval development and adult fertility.—Kramer, J. M. Structures and functions of collagens inCaenorhabditis elegans. FASEB J.8: 329‐336; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143939

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

There are two major reasons for interest in antibodies to DNA: autoantibodies to DNA are characteristic of the autoimmune disease systemic lupus erythematosus and contribute to its pathology; and both autoantibodies and experimentally induced antibodies to nucleic acids serve as useful biochemical reagents. Physical biochemistry and molecular biology are applied increasingly to questions of the structure and origin of antibodies to DNA and how antibodies recognize specific structures in DNA. Cloning of cDNA for Ig V regions of anti‐DNA antibodies reveals that some cells making IgG disease‐related autoantibodies are derived from precursor cells that produce natural autoantibodies unrelated to disease. In addition, some immunization‐induced antibodies to DNA use gene segments similar to those found in autoantibodies. Cloning and expression of recombinant V regions allow detailed analysis of antibody structures required for DNA binding. Domain swapping and mutagenesis with vectors for bacterial expression of single chain Fv molecules revealed the importance of CDR3 sites of both H and L chain V regions for specific antigen binding by antibody to Z‐DNA. In certain autoantibodies, the H chain plays a dominant role in determining DNA binding. Molecular analysis opens doors to studies of normal immune tolerance and its loss in autoimmune disease as well as to development of antibodies with modified specificity.—Stollar, B. D. Molecular analysis of anti‐DNA antibodies.FASEB J.8: 337‐342; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.7511550

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

Gene transcription mediated by steroid hormones has become one of the most extensively characterized model systems for studying the regulation of gene expression in eukaryotic cells. However, specific details of gene regulation by steroid hormones are often complex and may be unique in specific cell types. Diverse regulatory mechanisms leading to either activation or repression of particular genes frequently involve interactions between steroid hormone receptors and other ubiquitous and/or cell‐specific transcription factors that act on the complex promoter of the regulated gene. Interplay between steroid receptor‐mediated and other signal transduction pathways may also be involved. In addition, recent novel results indicate that moderate variations in the intracellular concentration of pyridoxal 5'‐phosphate (PLP), the biologically active form of vitamin B6, can have pronounced modulatory effects on steroid‐induced gene expression. Specifically, elevation of intracellular PLP levels leads to decreased transcriptional responses to glucocorticoid, progesterone, androgen, or estrogen hormones. Conversely, cells in a vitamin B6‐deficient state exhibit enhanced responsiveness to steroid hormones. One aspect of the mechanism by which these transcriptional modulatory effects of PLP occur has recently been shown to involve interruption of functional interactions between steroid hormone receptors and the nuclear transcription factor NF1. These findings — that the vitamin B6nutritional status of cells modulates their capacity to respond to steroid hormones — impose an additional level of cell‐specific control over steroid hormone regulation of gene expression and will serve as the focal point for this review.—Tully, D. B., Allgood, V. E., Cidlowski, J. A. Modulation of steroid receptor‐mediated gene expression by vitamin B6.FASEB J.8: 343‐349; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.8143940

出版商:Wiley    

年代:1994

数据来源: WILEY

摘要:

The gut receptor of trypsin‐modulating oostatic factor (TMOF), a decapeptide hormone that regulates trypsin biosynthesis in the mosquito gut, has been characterized. The binding of TMOF to mosquito gut membranes reached maximum at pH 7.4 and 24°C. No binding was observed at pH 2.5 and the binding to the membranes declined rapidly at pH 8.0. At equilibrium, maximum binding to the receptor was observed at 60 min and 24°C. A synthetic complementary decapeptide NH2‐Ile‐Leu‐Gly‐Arg‐Gly‐Gly‐Gly‐Gly‐Gly‐Gly‐COOH (FOMT) for TMOF successfully competed with the gut receptor, and specifically bound TMOF (Kd= 4 μmandKassoc= 2.5 × 105m−1). TMOF binding to gut membranes was characterized with FOMT and a specific ELISA to the hormone at 24 and 72 h after blood feeding. Two classes of binding sites were found on the gut membrane; high affinity (Kd1= 4.6 ± 0.7 × 10−7m;Kassoc= 2.2 × 106m−1Bmax= 0.1 pmol/gut) and low affinity (Kd2= 4.43 ± 1 × 10−6m;Kaggoc= 2.3 × 105m−1;Bmax= 0.2 pmol/gut). The total binding sites for high and low affinity classes of TMOF per gut were estimated as 6.3 × 1010and 1.1 × 1011sites, respectively. Specific binding sites on the gut increased after the blood meal and were visualized by immunocytochemical staining. These results suggest that TMOF regulates trypsin biosynthesis by binding to specific receptor sites that are located on the mosquito gut, and that this receptor can be studied using a complementary peptide approach.—Borovsky, D., Powell, C. A., Nayar, J. K., Blalock, J. E., Hayes, T. K. Characterization and localization of mosquito‐gut receptors for trypsin modulating oostatic factor using a complementary peptide and immunocytochemistry.FASEB J.8: 350‐355; 1994.

ISSN:0892-6638    

DOI:10.1096/fasebj.8.3.7908271

出版商:Wiley    

年代:1994

数据来源: WILEY

ISSN:0892-6638    

DOI:10.1096/j.1530-6860.1994.tb93358.x

出版商:Wiley    

年代:1994

数据来源: WILEY