Expression of Genes for Photosynthesis and the Relationship to Salt Tolerance of Alfalfa (Medicago sativa) Cells

The basis for the salt tolerant phenotype of a line of Medicagosativa (alfalfa) cells (HG2-N1) derived by selection from asalt sensitive line (HG2) was studied. The salt tolerant HG2-N1cell line shows eleven fold elevated chlorophyll content overthat of the parent salt sensitive HG2 cell line, with an additionaltwo fold increase in chlorophyll levels when the cells are grownin 1% NaCl. In this study, we demonstrate that the chlorophyllaccumulation and response to salt was associated with largeincreases in the two photosynthesis related mRNAs, rbcL (ribulose-l,5-bis-phosphatecarboxylase [Rubisco] large subunit) and rbcS (Rubisco smallsubunit) and a substantial increase in the activity of the holoenzyme.The salinity-induced increase in catalytically competent Rubiscoprotein in the salt tolerant cell line was highly responsiveto light and correlated with the salt tolerant phenotype. Inaddition, NaCl stimulated rbcL and rbcS mRNA and Rubisco accumulationin dark grown salt tolerant cells, indicating that salt couldsubstitute to some degree for light in stimulating increasesin specific mRNA and protein concentrations. Increased photosyntheticcompetence associated with these increased protein levels wasapparently important in contributing to the salt tolerant phenotypeof HG2-N1, since PS II electron transport inhibitors (DCMU,cyanazine) were found to significantly reduce the growth ofthis cell line in the presence of salt, but not in the absenceof salt. These results suggest that the salt-induced increasein mRNA and protein accumulation involved in photosynthesismay play a significant role in the salt tolerant capabilityof HG2-N1 alfalfa cells. (Received April 2, 1990; Accepted September 10, 1990)     

COMPARATIVE ULTRASTRUCTURAL STUDIES OF SPERMATOGENESIS IN THE METZGERIALES (HEPATOPHYTA) II. THE BLEPHAROPLAST OF BLASIA PUSILLA

As in other hepatics, the young spermatid of Blasia pusilla contains a well-developed blepharoplast comprising a four-layered multilayered structure (MLS) and two overlying dimorphic basal bodies. The asymmetrical spline (S₁ or upper stratum of the MLS) numbers 20 or 21 microtubules (MTs) at its anterior tip and reduces to eight at the posterior limit of the lamellar strip (LS). Behind this the shank of the spline is five or six tubules in width over most of its length, approximately one revolution of the circumference of the gamete. The three-microtubule spline aperture underlies the anterior basal body and like those of most hepatics, it is closed at its anterior end. The asymmetrical LS (approx. 2.0 μm in length) is characterized by a right-hand posterior notch which lies below the spline aperture at the region of the cartwheel configuration of the anterior basal body (ABB). The staggered dimorphic basal bodies overlap for approximately one third of their lengths. Both lie parallel to the long axis of the spline. As in other hepatics, the ABB (1.2 μm in length) is subapical and comprises an anterior hub extension with progressive rearward additions of lateral, dorsal and ventral triplets. Over most of its length (2.1 μm) the longer posterior basal body (PBB) consists of a distinct central hub and three ventral triplets. Transition zones of both basal bodies contain stellate configurations into which the two central axonemal MTs frequently extend. The blepharoplast of Blasia shows several features in common with leafy, simple thalloid and complex thalloid liverworts. Compared with the few Metzgeriales observed thus far, the LS is less elongate and the basal bodies less staggered. Dimensions of basal body components and spline dimensions, however, are comparable to those of most leafy and thalloid hepatics. Striking similarities with the complex thalloid liverworts include a posterior notch in the LS and a spline aperture three MTs wide.     

Functional morphology of the gills of the shortfin mako,Isurus oxyrinchus,a lamnid shark

This study examines the functional gill morphology of the shortfin mako, Isurus oxyrinchus, to determine the extent to which its gill structure is convergent with that of tunas for specializations required to increase gas exchange and withstand the forceful branchial flow induced by ram ventilation. Mako gill structure is also compared to that of the blue shark, Prionace glauca, an epipelagic species with lower metabolic requirements and a reduced dependence on fast, continuous swimming to ventilate the gills. The gill surface area of the mako is about one‐half that of a comparably sized tuna, but more than twice that of the blue shark and other nonlamnid shark species. Mako gills are also distinguished from those of other sharks by shorter diffusion distances and a more fully developed diagonal blood‐flow pattern through the gill lamellae, which is similar to that found in tunas. Although the mako lacks the filament and lamellar fusions of tunas and other ram‐ventilating teleosts, its gill filaments are stiffened by the elasmobranch interbranchial septum, and the lamellae appear to be stabilized by one to two vascular sacs that protrude from the lamellar surface and abut sacs of adjacent lamellae. Vasoactive agents and changes in vascular pressure potentially influence sac size, consequently effecting lamellar rigidity and both the volume and speed of water through the interlamellar channels. However, vascular sacs also occur in the blue shark, and no other structural elements of the mako gill appear specialized for ram ventilation. Rather, the basic elasmobranch gill design and pattern of branchial circulation are both conserved. Despite specializations that increase mako gill area and efficacy relative to other sharks, the basic features of the elasmobranch gill design appear to have limited selection for a larger gill surface area, and this may ultimately constrain mako aerobic performance in comparison to tunas. J. Morphol. 271:937–948, 2010. © 2010 Wiley‐Liss, Inc.     

Dopamine receptors in the learning,memory and drug reward circuitry

As primary targets of a variety of abused drugs G-protein-coupled dopamine receptors in the brain play an important role in mediating the various drug-induced alterations in neural and psychological processes thought to underlie the transition from voluntary drug use to habitual and progressively compulsive drug-taking. This review considers the functional involvement of the five major dopamine receptor subtypes in drug reinforcement and reward and discusses the development of addiction as a series of learning transitions from initial goal-directed behaviour to pathological stimulus–response habits in which drug-seeking behaviours are automatically elicited and maintained by cues and stimuli associated with drug rewards.     

Effect of estradiol-17β on glucose and proline uptake in plasma membrane vesicles from the R3230AC rat mammary carcinoma

Purified plasma membrane vesicles isolated from R3230AC rat mammary tumors displayed carrier-mediated and stereospecific uptake. Uptake was shown to be proportional to protein concentration, sensitive to increasing osmolarity, and inhibited only by substrates entering by the same carrier. Carrier-mediated glucose uptake was inhibited rapidly by estradiol-17β and phloretin in a dose-dependent manner, whereas proline uptake was not affected by estradiol-17β. The data suggest that the inhibition of glucose by estradiol and phloretin, originally observed in whole cells, occurs by an interaction of the steroid with a component on the plasma membrane. In contrast, the lack of effects of estradiol on proline transport into vesicles implies that intracellular components may have mediated the estrogen-induced effects observed in whole cells.