Comparison of water immersion and saline infusion as a means of inducing volume expansion in man.

Although previous studies have demonstrated that water immersion to the neck (NI) results in both central hypervolemia and a significant natriuresis, it is unclear whether the magnitude of the "volume stimulus" of NI is comparable to that induced by the extracellular fluid volume expansion (ECVE) induced by acute saline administration. The present study was undertaken therefore to compare the natriuresis induced by these two different stimuli. All subjects were studied on four occasions while in balance on a diet containing 150 meq of sodium and 80 meq of potassium daily: seated control; seated immersion; and saline administration in both the seated and recumbent posture. The increment in UNaV during NI was indistinguishable from that of seated saline. Similarly, the kaliuretic response during NI was similar to that induced by seated saline infusion. In contrast, supine saline infusion resulted in a greater increment in UNaV than either NI or seated saline. The present data indicate that the "volume stimulus" of immersion is identical with that of standard saline-induced ECVE in normal seated subjects. Furthermore, the ability of NI to induce a natriuresis without a concomitant increase in total blood volume and with a decrease in body weight, rather than the increase which attends saline infusion, suggests that NI may be a preferred investigative tool for assessing the effects of ECVE in man.     

Uptake and fate of IAA in apple callus tissues: metabolism of IAA-2-14C

Young and old apple callus tissues were incubated in light ordarkness with IAA-2-¹⁴C. A large portion of the IAA disappearedfrom the medium with both young and old calluses. Whereas withold calluses the loss was mainly due to IAA destruction, youngcalluses accumulated IAA to a level which exceeded the externalconcentration and, in addition, seemed to protect it from breakdown.After 24 hr the level of IAA-2-¹⁴C in the medium dropped to50% with old calluses both in the dark and light, and with youngcalluses to 20% in the light and 50% in the dark. Chromatographyand scanning of the media and calluses showed that IAA was convertedinto two compounds (comp. A and comp. B). The amounts and proportionsof these metabolites in the medium and tissue were dependenton the different treatments and callus age. The breakdown ofIAA by old tissue gave rise to a higher level of comp. B bothin the tissue and medium, particularly after 6 hr of incubation.In the medium of young tissues the level of comp. A was higherthan comp. B while equal amounts of the two compounds were detectedin the tissue, itself. The origin of the IAA products in thetissue was probably endogenous and not via absorption from themedium. The IAA metabolism of apple callus tissues seems toproceed via the oxindole pathway and it is proposed that compoundsA and B are 3-hydroxymethyloxindole and 3-methylene oxindole,respectively. ¹ Contribution from the Agricultural Research Origanization,The Volcani Center, Bet Dagan, Israel. 1973 Series No. 275-E. (Received May 30, 1974; )     

The influence of electric fields red blood cells.

The effect of electric fields as related to red blood cell sizing techniques, hemolysis, mobility, and general behavior is examined. A review is made of the varying theories concerning these effects. In addition, the physical ramifications of electric field experimentation is viewed. Criticisms are made with regard to technique and lack of consideration for certain experimental variables.     

Eudicot primary cell wall glucomannan is related in synthesis,structure, and function to xyloglucan

Hemicellulose polysaccharides influence assembly and properties of the plant primary cell wall (PCW), perhaps by interacting with cellulose to affect the deposition and bundling of cellulose fibrils. However, the functional differences between plant cell wall hemicelluloses such as glucomannan, xylan, and xyloglucan (XyG) remain unclear. As the most abundant hemicellulose, XyG is considered important in eudicot PCWs, but plants devoid of XyG show relatively mild phenotypes. We report here that a patterned β-galactoglucomannan (β-GGM) is widespread in eudicot PCWs and shows remarkable similarities to XyG. The sugar linkages forming the backbone and side chains of β-GGM are analogous to those that make up XyG, and moreover, these linkages are formed by glycosyltransferases from the same CAZy families. Solid-state nuclear magnetic resonance indicated that β-GGM shows low mobility in the cell wall, consistent with interaction with cellulose. Although Arabidopsis β-GGM synthesis mutants show no obvious growth defects, genetic crosses between β-GGM and XyG mutants produce exacerbated phenotypes compared with XyG mutants. These findings demonstrate a related role of these two similar but distinct classes of hemicelluloses in PCWs. This work opens avenues to study the roles of β-GGM and XyG in PCWs.

Patterned β-GGM resembles xyloglucan in structure, biosynthesis, and function.

In a Nutshell Background: Plant primary cell walls (PCWs) need to be rigid enough to define the plant shape and yet allow cell expansion at the same time. Plants achieve this by forming a complex network that is composed of cellulose and various non-cellulosic polysaccharides, such as hemicelluloses. Cell walls differ in the abundance of the various hemicelluloses, and their roles are poorly understood. In contrast to xyloglucan (XyG), which has been the most extensively studied hemicellulose in the PCWs, neither the structure nor functions of glucomannan has been resolved. Question: Are the functions of the glucomannan in PCWs distinct from the roles of the most abundant hemicellulose, XyG? Findings: We discovered a type of glucomannan in eudicot PCWs, which we named β-galactoglucomannan (β-GGM) because of its distinctive structures: disaccharide side chains of β-Gal-α-Gal and alternating repeats of Glc-Man in the backbone. Similarity to XyG in structure and biosynthesis led us to identify a β-galactosyltransferase for the β-GGM biosynthesis. We found that β-GGM contributed to normal cell expansion, in a way that was masked by the presence of XyG. These results suggest related functions of β-GGM to XyG, highlighting the necessity to consider the contribution of multiple hemicelluloses in the functional study of plant cell walls. Next steps: We would like to know how β-GGM binds to cellulose, and how this differs to cellulose binding of XyG. Investigation of the precise arrangements and interactions of cellulose and hemicelluloses including β-GGM and XyG will help further understanding of the enigmatic functions of hemicelluloses.     

The gut supports neurogenic differentiation of periocular mesenchyme, a chondrogenic neural crest-derived cell population

Periocular mesenchyme (PM) is a mesencephalic neural crest derived cell population which as a result of an interaction with the retinal pigment epithelium forms the scleral cartilage of the avian eye. Enteric neurons are derived from vagal crest cells which invade the gut. To study factors which regulate neuronal differentiation, we investigated whether the gut could direct neurogenesis in PM, a cell population that does not produce neurons in vivo. We report here that PM cultured in the presence of aneural chick hindgut on the chorioallantoic membrane (CAM), invaded the gut and formed large numbers of neurons. These were localized in enteric ganglia and contained neurofilament immunoreactivity, vasoactive intestinal peptide immunoreactivity, and somatostatin immunoreactivity. In the control PM cultured alone on the CAM, a small number of cells contained neurofilament immunoreactivity but lacked the appearance of mature neurons.     

Kinetics of actin-myosin binding. II. Two-variable model and actin gelation

We consider a model of actin-myosin interaction in which the sites belonging to each seven-site regulated actin unit are subdivided into two classes, "internal" and "external." The time evolution of each class of sites is considered separately, leading to a pair of coupled differential equations that may be integrated numerically. We also consider the critical sol-gel transition point for actin filaments crosslinked by two-headed heavy meromyosin (HMM). The possibility of new types of chemical oscillation and pattern formation arising from periodic sol-gel transitions is discussed.     

Stainless steel mesh supports high density cell growth and production of recombinant Mullerian Inhibiting Substances

Summary Stainless steel mesh supported the high density growth of anchorage dependent CHO fibroblasts without the use of a special culture system. CHO cells, designated B-9, containing an amplified genomic construct of the human gene for Mullerian Inhibiting Substance (MIS), grew to a high confluent density on stainless steel meshwork while producing substantial amounts of human recombinant MIS over a long period of time. The mesh could be easily coated with various extracellular matrix proteins, such as Laminin, Fibronectin, Collagen or Matrigel, which permitted the testing of the effects of surface modifications on cell yield and recombinant protein production. Since the amount of medium per surface area required for optimal cell growth is lower than for some large volume cell culture methods, media costs can be reduced using mesh. In addition, no special cell culture equipment or complex manipulations are required. Thus, the use of meshwork for anchorage-dependent cells can increase the efficiency of growth and decrease the cost of recombinant protein production. This work is supported by NIH grant CA 17393 and American Cancer Society grant PDT 221A to P. K. D. and NIH grant EY 06535 to J. E. Editor's Statement This approach to large scale, high density cultivation of cells, one of several which are based on increasing surface area of the cultures, allows the production of large amounts of recombinant product within a research laboratory with modest bulk culture capability.     

Identification of Protor as a novel Rictor-binding component of mTOR complex-2

The mTOR (mammalian target of rapamycin) protein kinase is an important regulator of cell growth. Two complexes of mTOR have been identified: complex 1, consisting of mTOR-Raptor (regulatory associated protein of mTOR)-mLST8 (termed mTORC1), and complex 2, comprising mTOR-Rictor (rapamycininsensitive companion of mTOR)-mLST8-Sin1 (termed mTORC2). mTORC1 phosphorylates the p70 ribosomal S6K (S6 kinase) at its hydrophobic motif (Thr389), whereas mTORC2 phosphorylates PKB (protein kinase B) at its hydrophobic motif (Ser473). In the present study, we report that widely expressed isoforms of unstudied proteins termed Protor-1 (protein observed with Rictor-1) and Protor-2 interact with Rictor and are components of mTORC2. We demonstrate that immunoprecipitation of Protor-1 or Protor-2 results in the co-immunoprecipitation of other mTORC2 subunits, but not Raptor, a specific component of mTORC1. We show that detergents such as Triton X-100 or n-octylglucoside dissociate mTOR and mLST8 from a complex of Protor-1, Sin1 and Rictor. We also provide evidence that Rictor regulates the expression of Protor-1, and that Protor-1 is not required for the assembly of other mTORC2 subunits into a complex. Protor-1 is a novel Rictor-binding subunit of mTORC2, but further work is required to establish its role.