The animal musks and a comment of their biogenesis

Summary The macrocyclic compounds occurring in animal glandular secretions are reviewed. Early hypotheses for their biogenesis from fatty acids via and -oxidations are found to be inadequate. Radio-active acetate was incorporated into macrocyclic ketones of muskrat (Ondatra sp.) preputial glandular secretion, but radiolabelled stearate, oleate, anda, -octadecandioic acid were not incorporated.Acknowledgment. We wish to thank Dr.W.J. Doude van Troostwijk, Research Institute for Nature Management, Arnhem, for his assistance in obtaining muskrats, and Mr J. Vellekoop, Leiden, for the Shakespeare quotations.     

Regulation of nicotine biogenesis 2: Increased production of nicotine by urea in tobacco tissue cultures

Summary The floral bud callus ofNicotiana tabacum L. was successfully grown on 10 mM urea as sole nitrogen source. Nicotine content in the urea-treated tissues was 3.5 times higher than in the control on the basis of dry weight, and 2.5-fold higher per culture. Contents of ornithine, citrulline and arginine, urea cycle intermediates, and known precursors of nicotine, were higher in urea-treated callus. The implications of the results are discussed.Financial support given to one of us (GAR) by the Maharaja Sayajirao University of Barado is gratefully acknowledged. Reference No. represents part 1 of the series on regulation of nicotine biogenesis.     

Mechanism of tryptophane biogenesis and decomposition

Zusammenfassung Für den biosynthetischen Vorgang: Indol + Serin Tryptophan wird ein detaillierter chemischer Reaktionsverlauf vorgeschlagen. Der Verlauf des Abbaus von Tryptophan zu Indol, Brenztraubensäure und Ammoniak wird in ähnlicher Weise gedeutet.     

Acceleration of the cerebral dopamine turnover by chlorpromazine

Zusammenfassung Im Stammhirn von normothermen Ratten bewirkt Chlorpromazin einen Anstieg von Homovanillinsäure (HVS), der bei Hypothermie verringert wird. Dieser Anstieg geht nicht mit einer Verminderung der Dopaminkonzentration einher und bleibt nach Hemmung der Monoaminoxydase aus. Die durch Vorbehandlung mit einem kurzwirkenden Monoaminfreisetzer (Benzochinolizinderivat Ro 4-1284) erhöhte endogene HVS zeigt nach Chlorpromazin keinen verzögerten Abfall.     

The biogenesis and function of eukaryotic porins

Summary Like most other mitochondrial proteins porin is synthesized in the cytosol and imported posttranslationally into the outer mitochondrial membrane. This transport follows the general rules for mitochondrial, protein import with a few aberrations: a) porin contains an,uncleaved NH₂-terminal signal sequence, b) also its carboxyterminus might be involved in the import process, and c) this transport does not seem to require a membrane potential , although it is ATP-dependent. Most likely the actual import step occurs at contact sites between the outer and the inner mitochondrial membrane and involved at least one receptor protein.Although porin is known to be the major gate through the outer mitochondrial membrane, its absence only causes transient respiratory problems in yeast cells. This could mean a) that there is a bypass for some mitochondrial functions in the cytosol and/or b) that there are alternative channel proteins in the outer membrane. The first idea is supported by the overexpression of cytosolic virus-like particles in yeast cells lacking porin and the second by the occurrence of residual pore activity in mitochondrial outer membrane purified from porinless mutant cells.     

Cellular turnover and extracellular matrix remodeling in female reproductive tissues: functions of metalloproteinases and their inhibitors

Female reproductive tissues possess a unique ability to accommodate a remarkable amount of cell turnover and extracellular matrix (ECM) remodeling following puberty. Cellular structures within ovary, uterus, and mammary tissue not only change cyclically in response to ovarian hormones but also undergo differentiation during pregnancy, and eventually revert to that resembling the pre-pregnant stage. Cell proliferation, apoptosis, invasion, and differentiation are integral cellular processes that are precisely regulated in reproductive tissues, but become dysregulated in pathologies such as cancer. Explicit reorganization of ECM and basement membranes is also critical to preserve the form and function of these tissues. Here we review the evidence that coordinated spatiotemporal expression patterns of matrix metalloproteinase (MMP) genes and their tissue inhibitors (TIMPs) are important in cell and ECM turnover of the ovary, uterus, and mammary tissues. We discuss how perturbation in these gene families may impact the biology of these reproductive tissues and the factors implicated in the control of MMP and TIMP gene expression. The observed trends in MMP and TIMP expression involved in ovarian and mammary carcinomas are also presented.     

Routes and machinery of primary cilium biogenesis

Primary cilia are solitary, microtubule-based protrusions of the cell surface that play fundamental roles as photosensors, mechanosensors and biochemical sensors. Primary cilia dysfunction results in a long list of developmental and degenerative disorders that combine to give rise to a large spectrum of human diseases affecting almost any major body organ. Depending on the cell type, primary ciliogenesis is initiated intracellularly, as in fibroblasts, or at the cell surface, as in renal polarized epithelial cells. In this review, we have focused on the routes of primary ciliogenesis placing particular emphasis on the recently described pathway in renal polarized epithelial cells by which the midbody remnant resulting from a previous cell division event enables the centrosome for initiation of primary cilium assembly. The protein machinery implicated in primary cilium formation in epithelial cells, including the machinery best known for its involvement in establishing cell polarity and polarized membrane trafficking, is also discussed.     

The biogenesis and function of eukaryotic porins.

Like most other mitochondrial proteins porin is synthesized in the cytosol and imported posttranslationally into the outer mitochondrial membrane. This transport follows the general rules for mitochondrial protein import with a few aberrations: a) porin contains an uncleaved NH2-terminal signal sequence, b) also its carboxyterminus might be involved in the import process, and c) this transport does not seem to require a membrane potential delta psi, although it is ATP-dependent. Most likely the actual import step occurs at contact sites between the outer and the inner mitochondrial membrane and involves at least one receptor protein. Although porin is known to be the major gate through the outer mitochondrial membrane, its absence only causes transient respiratory problems in yeast cells. This could mean a) that there is a bypass for some mitochondrial functions in the cytosol and/or b) that there are alternative channel proteins in the outer membrane. The first idea is supported by the overexpression of cytosolic virus-like particles in yeast cells lacking porin and the second by the occurrence of residual pore activity in mitochondrial outer membrane purified from porinless mutant cells.     

Sequential biogenesis of host cell membrane rearrangements induced by hepatitis C virus infection

Like most positive-strand RNA viruses, hepatitis C virus (HCV) forms a membrane-associated replication complex consisting of replicating RNA, viral and host proteins anchored to altered cell membranes. We used a combination of qualitative and quantitative electron microscopy (EM), immuno-EM, and the 3D reconstruction of serial EM sections to analyze the host cell membrane alterations induced by HCV. Three different types of membrane alteration were observed: vesicles in clusters (ViCs), contiguous vesicles (CVs), and double-membrane vesicles (DMVs). The main ultrastructural change observed early in infection was the formation of a network of CVs surrounding the lipid droplets. Later stages in the infectious cycle were characterized by a large increase in the number of DMVs, which may be derived from the CVs. These DMVs are thought to constitute the membranous structures harboring the viral replication complexes in which viral replication is firmly and permanently established and to protect the virus against double-stranded RNA-triggered host antiviral responses.     

Prevention or acceleration of type 1 diabetes by viruses

Type 1 diabetes is an autoimmune disease characterized by the destruction of insulin-producing pancreatic β-cells. Even though extensive scientific research has yielded important insights into the immune mechanisms involved in pancreatic β-cell destruction, little is known about the events that trigger the autoimmune process. Recent epidemiological and experimental data suggest that environmental factors are involved in this process. In this review, we discuss the role of viruses as an environmental factor on the development of type 1 diabetes, and the immune mechanisms by which they can trigger or protect against this pathology.     

The biogenesis of the morphine alkaloids and related topics

Zusammenfassung Die biologische Entstehung von Thebain und Sinomenin aus zwei enantiomorphen Formen von Laudanin wird zur Diskussion gestellt. Der Schluss der 4,5-Oxyd-Brücke bei 7-Hydroxy-,7-Amino-, Bromo- und 6-Oximino-Verbindungen verläuft analog dem vorgeschlagenen, biologischen Entstehungsweg. Es wird angenommen, dass die Bromierung der 6-Keto-7:8-dihydro-Verbindungen aus der Morphingruppe in Stellung 7 vor sich geht.