The Biosynthesis of meso-Inositol by Cultured Mammalian Cells, and the Parabiotic Growth of Inositol-dependent and Inositol-independent Strains

The role of inositol and the principles of labelling, extraction, and analysis of inositides in mammalian cells

Inositides have an important impact on diverse areas of cellular regulation. However, since this area has grown exponentially from the mid 1980s onwards, many workers find themselves relatively new to the field. In this chapter, we establish a broad foundation for the rest of the book by covering some important principles of inositide methodologies. The focus is especially directed to those methods or aspects of methodology not covered in detail in other chapters. This includes the often neglected influence of the inositide precursor, inositol, and important background information relating to the labelling and extraction of inositides from cells and tissues. This introductory section also gives a "birds eye" view of important methods and protocols found within this volume and hopefully acts as a touchstone to assess which of the methodologies described within this book is most appropriate for your particular study(ies) of inositides.

Inositol and higher inositol phosphates in neural tissues: homeostasis, metabolism and functional significance

Inositol phospholipids and inositol phosphates mediate well-established functions in signal transduction and in Ca2+ homeostasis in the CNS and non-neural tissues. More recently, there has been renewed interest in other roles that both myo-inositol and its highly phosphorylated forms may play in neural function. We review evidence that myo-inositol serves as a clinically relevant osmolyte in the CNS, and that its hexakisphosphate and pyrophosphorylated derivatives may play roles in such diverse cellular functions as DNA repair, nuclear RNA export and synaptic membrane trafficking.

Abalone, Haliotis discus hannai Ino, can synthesize myo-inositol de novo to meet physiological needs

The experiments were conducted to investigate the effects of dietary myo-inositol on the survival, growth, proximate composition and de novo synthesis of myo-inositol in abalone, Haliotis discus hannai Ino. The possible inositol-synthesizing capacity of intestinal microflora was also examined. Seven semipurified diets were formulated to provide graded levels of myo-inositol (28.7-1020.1 mg/kg diet). A control diet, the basal diet supplemented with 4 g/kg tetracycline hydrochloride, was employed to suppress synthesis of myo-inositol by intestinal bacteria. Abalone juveniles of similar size (weight, 144.6 +/- 0.8 mg; shell length, 10.92 +/- 0.10 mm) were distributed in a flow-through system using a completely randomized design with eight treatments and three replicates per treatment. They were fed the appropriate diets once daily for 16 wk. Survival, growth, crude protein, lipid, moisture of whole soft body and visceral inositol content were independent of myo-inositol supplementation (P > 0.05). The addition of the antibiotic also did not affect the survival, growth and whole soft body composition. It indicated that intestinal microflora contributed little to the myo-inositol nutrition in abalone. The present study, for the first time, demonstrated de novo synthesis of myo-inositol in mollusks because the visceral tissue of abalone showed high levels of myo-inositol synthetase activities (combined activities of myo-inositol-1-phosphate synthetase and inositol-1-phosphatase), ranging from 74.0 to 98.2 micromol/(h x g protein). The enzyme activity significantly and negatively correlated with dietary myo-inositol level (r = -0.81). Hence, dietary myo-inositol is not essential for abalone because tissue synthesis of the vitamin appears to be sufficient to support normal growth and health of this mollusk.

Myo-inositol in physiological concentrations stimulates production of prostaglandin-like material

In physiological concentrations myo-inositol stimulated production of prostaglandin (PG)-like material in a rat mesenteric vascular bed preparation. There were five lines of evidence: 1. Inositol potentiated pressor responses to both norepinephrine and potassium in a manner similar to PGE2. 2. Inositol had no potentiating effect in preparations in which endogenous PG production was blocked by indomethacin. 3. Inositol caused no further potentiation in preparations already potentiated by arachidonic acid, the PG precursor. 4. The inhibitory effect of the PG antagonist chloroquine was reduced in an apparently competitive manner by inositol. 5. As indicated by rat stomach bioassay inositol caused a three fold rise in the outflow of PG-like material from the preparation.

Occurrence and determination of inositol in the oviducts of turkey and hen

AT the junction of uterus and vagina of the turkey a few scattered tubular glands have been observed, Spermatozoa are stored there² and retain their fertilizing ability for about 45 days². Turkey semen collected for insemination, however, has to be used within an hour of ejaculation, because fertility decreases considerably after that time.