Guanylyl cyclases and signaling by cyclic GMP.

Guanylyl cyclases are a family of enzymes that catalyze the conversion of GTP to cGMP. The family comprises both membrane-bound and soluble isoforms that are expressed in nearly all cell types. They are regulated by diverse extracellular agonists that include peptide hormones, bacterial toxins, and free radicals, as well as intracellular molecules, such as calcium and adenine nucleotides. Stimulation of guanylyl cyclases and the resultant accumulation of cGMP regulates complex signaling cascades through immediate downstream effectors, including cGMP-dependent protein kinases, cGMP-regulated phosphodiesterases, and cyclic nucleotide-gated ion channels. Guanylyl cyclases and cGMP-mediated signaling cascades play a central role in the regulation of diverse (patho)physiological processes, including vascular smooth muscle motility, intestinal fluid and electrolyte homeostasis, and retinal phototransduction. Topics addressed in this review include the structure and chromosomal localization of the genes for guanylyl cyclases, structure and function of the members of the guanylyl cyclase family, molecular mechanisms regulating enzymatic activity, and molecular sequences coupling ligand binding to catalytic activity. A brief overview is presented of the downstream events controlled by guanylyl cyclases, including the effectors that are regulated by cGMP and the role that guanylyl cyclases play in cell physiology and pathophysiology.

Establishment and characterization of a line of adipose-derived human microvascular endothelial cells (HADMEC-5) transformed by simian virus 40 large T antigen expression: application to endotoxin research.

This paper reports the establishment and initial characterization of an immortalized line of human, adipose tissue-derived microvascular endothelial cells. Transfection of primary endothelial cell cultures was accomplished by the introduction of a plasmid, which contained simian virus 40 large T antigen DNA as well as a Rous sarcoma viral promoter region. One emergent colony, termed HADMEC-5, was isolated and has been passaged 45 times to date. The cells express simian virus 40 large T antigen protein, are immunohistochemically positive for factor VIII-related antigen, bind Ulex europaeus lectin, and accumulate Dil-labeled acetylated low density lipoprotein. The HADMEC-5 line demonstrates a highly proliferative growth rate in the absence of supplemental growth factors, when compared with primary cultures of nontransformed endothelial cells. HADMEC-5 growth remains serum dependent, but exhibits a lower serum requirement than nontransformed cells. The transformed cells grow well upon a variety of matrix compounds and in a variety of growth media. When grown upon Matrigel, the HADMEC-5 cells form three dimensional tube-like structures. The HADMEC-5 line was also tested for its ability to produce eicosanoids in response to bacterial lipopolysaccharide. The transformed cells, tested at passages 7 and 45, displayed a dose-dependent production of prostaglandin E2 in response to lipopolysaccharide in a manner similar to that seen in primary cell cultures. Threshold sensitivity to lipopolysaccharide was 10 pg/mL of media. The HADMEC-5 cell line represents a unique model in which to investigate lipopolysaccharide interactions with microvessel-derived endothelial cells and is of potential value in the study of other aspects of endothelial cell physiology.

Efficacy of bomb shelters: with lessons from the Hamburg firestorm.

Shelters for protection against the effects of nuclear weapons are often stated to be useless, largely because of firestorms. Recent models purport to show that nuclear weapons are more likely to cause firestorms than previously thought. These controversial models are based on uncertain assumptions, which are difficult or impossible to test. Regardless of the predictive validity of fire models, conclusions about the ability of shelters to protect their occupants against firestorms, if they occur, are based primarily on historical experience. A review of the original data from the Hamburg firestorm shows that almost all persons in adequate shelters survived, contradicting a currently prevailing belief that all died. The results of the strategic bombing during World War II and of nuclear weapons tests show that a considerable level of population protection can be achieved through attention to proper shelter design.