THE HORMONAL INTEGRATION OF SEXUAL REPRODUCTION IN OEDOGONIUM

Rawitscher -Kunkel , Erika , and L. Machlis . (U. California, Berkeley.) The hormonal integration of sexual reproduction in Oedogonium. Amer. Jour. Bot. 49 (2) : 177–183. Illus. 1962.—Sexual reproduction in a heterothallic, nannandrous species of Oedogonium was investigated cytologically and physiologically. Several new observations are reported. Oogonial mother cells release a substance which attracts androspores to them. The androspores, when attached to the oogonial mother cells, grow in well-defined directions apparently in response to a hormone originating in the oogonial mother cells. An oogonial mother cell divides into an oogonium and a suffultory cell only after the attached androspores complete their development into dwarf males, each bearing an antheridium. Presumably the developing dwarf males provide a chemical stimulus for the division of the oogonial mother cell. During development, the oogonia become enveloped in a massive gel which also encases the antheridia cut off at the apical ends of the dwarf male plants. The gel appears to function as a sperm trap, preventing the dissemination of the sperm into the surrounding liquid. The sperm are attracted to the protoplasmic papilla which briefly protrudes through the oogonial pore indicating the operation of a second chemotactic agent.     

Mice Lacking Platelet-Derived Growth Factor D Display a Mild Vascular Phenotype

Platelet-derived growth factor D (PDGF-D) is the most recently discovered member of the PDGF family. PDGF-D signals through PDGF receptor β, but its biological role remains largely unknown. In contrast to other members of the PDGF family of growth factors, which have been extensively investigated using different knockout approaches in mice, PDGF-D has until now not been characterized by gene inactivation in mice. Here, we present the phenotype of a constitutive Pdgfd knockout mouse model (Pdgfd^-/-), carrying a LacZ reporter used to visualize Pdgfd promoter activity. Inactivation of the Pdgfd gene resulted in a mild phenotype in C57BL/6 mice, and the offspring was viable, fertile and generally in good health. We show that Pdgfd reporter gene activity was consistently localized to vascular structures in both postnatal and adult tissues. The expression was predominantly arterial, often localizing to vascular bifurcations. Endothelial cells appeared to be the dominating source for Pdgfd, but reporter gene activity was occasionally also found in subpopulations of mural cells. Tissue-specific analyses of vascular structures revealed that NG2-expressing pericytes of the cardiac vasculature were disorganized in Pdgfd^-/- mice. Furthermore, Pdgfd^-/- mice also had a slightly elevated blood pressure. In summary, the vascular expression pattern together with morphological changes in NG2-expressing cells, and the increase in blood pressure, support a function for PDGF-D in regulating systemic arterial blood pressure, and suggests a role in maintaining vascular homeostasis.     

Preferential expression of cellular retinoic acid binding protein in a subpopulation of neural cells in the developing mouse embryo

The cellular retinoic acid binding protein is thought to be involved in the retinoic-acid-mediated signal transduction pathway. We have isolated the mouse cellular retinoic acid binding protein cDNA from an embryonal-carcinoma-derived cell line by using differential cDNA cloning strategies. In situ hybridization on sections of mouse embryos of various developmental stages indicated that the cellular retinoic acid binding protein gene, which we localized on mouse chromosome 9, is preferentially expressed in a subpopulation of neurectodermal cells. This restricted expression pattern suggests an important role for cellular retinoic acid binding protein in murine neurogenesis.     

Atrial granules in the dog heart after cardiac denervation

Summary Because the increase in sodium excretion during left atrial distension in conscious dogs is abolished after chronic cardiac denervation, we have investigated whether this is a result of the disappearance of specific atrial granules. Electron microscopy and light-microscopical and ultrastructural immunohistochemistry of canine atria show that atrial granules displaying immunoreactivity for cardiac hormones of the cardiodilatin/atrial natriuretic polypeptide (CDD/ANP) family are still present in denervated left and right atria, although reduced in quantity. It is concluded that the atrial-induced natriuresis is not only related to the existence of specific atrial granules. The functional link between atrial-induced natriuresis provoked by atrial distension and the release of atrial polypeptide hormones remains uncertain because the denervated heart can secrete CDD although the diuretic-natriuretic effect is altered.     

Localization of receptors for atrial natriuretic polypeptide (ANP) in the glomerulus: in vitro electron microscopic autoradiographical investigation using 125I-labeled ANP

The localization of receptors for atrial natriuretic polypeptide (ANP) in the glomerulus of the rat was studied by electron microscopic autoradiography using 125I-labeled ANP. A total of 1,134 silver grains counted in 30 glomeruli were distributed as follows: processes of the podocytes (36.4%), cell bodies of the podocytes (14.8%), basement membrane (12.3%), endothelial cells (6.3%), mesangial cells (7.7%) and others, for example the vascular spaces (22.5%). This finding indicates that ANP binding sites are mainly localized on the foot processes of the podocytes in the glomerulus.     

Characterization of the nontransformed and transformed androgen receptor and heat shock protein 90 with high-performance hydrophobic-interaction chromatography

The hydrophobicity of the nontransformed and transformed androgen receptor from rat submandibular gland and heat shock protein 90 (hsp90) from rat submandibular gland and liver was characterized by using high-performance hydrophobic-interaction chromatography on TSK gel Ether-5PW. In the absence of molybdate, cytosol [3H]R1881-androgen receptor complexes were mainly eluted in the 1.3 M region (Peak 1) with a small peak in the 0.8 M region (Peak 2) of a descending salt gradient (2 to 0 M) of ammonium sulfate. In the presence of molybdate, Peak 2 was predominant. When labeled-cytosol was applied after being heated at 25 degrees C for 30 min, a third peak (Peak 3) at around 0.64 M ammonium sulfate was newly observed. Peaks 2 and 3 were observed, while Peak 1 completely disappeared with the labeled-cytosol precipitated at 40% saturated ammonium sulfate. The Stokes radius of Peak 1 was 7 nm, and of Peak 2 was 8 nm. Both peaks were retained poorly by DNA-cellulose but bound rather well to DEAE-cellulose. These results suggest that these two peaks represent the nontransformed receptor, indicating that there are isoforms of the nontransformed androgen receptor which are distinguished by their hydrophobic properties and Stokes radii. Peak 3 had a Stokes radius of 5 nm and preferentially bound to DNA-cellulose, suggesting that this peak corresponds to the transformed receptor. These results indicated that the transformation of the androgen receptor accompanies the enrichment of the hydrophobicity of the receptor molecule. Hsp90 purified from rat livers and hsp90 in the cytosol both from livers and submandibular glands were eluted from Ether-5PW at 0.8 M ammonium sulfate, at almost the same position as Peak 2. This finding suggests that the enrichment of hydrophobicity on transformation is due to dissociation of hsp90 from the nontransformed androgen receptor.     

CAM Photosynthesis under Drought Conditions in Kalanchoe blossfeldiana Grown with Nitrate or Ammonium as the Sole Nitrogen Source

K. blossfeldiana Poelln. cv. Hikan was grown in vermiculite,supplied daily with nutrient solution containing 1 mM (or 10mM) nitrate or ammonium as the sole nitrogen source. The nitrate-grownplants had more activity of CAM (Crassulacean acid metabolism)photosynthesis (nocturnal CO₂ uptake in the shoot and nocturnalincreases of titratable acidity and malate content in the leaves)than the ammonium-grown plants. Interruption of the solutionsupply for 5 or more days (drought conditions) increased theactivity of CAM photosynthesis in nitrate- or ammonium-grownplants, and the diurnal CO₂ uptake pattern in the nitrate-grownplants shifted from ‘weak-CAM’ to ‘full-CAM’.The difference in the activity of CAM photosynthesis betweennitrate- and ammonium-grown plants increased under the droughtconditions. When the solution was resupplied, the activity ofCAM photosynthesis rapidly decreased to the levels before theinterruption. The physiological mechanism and ecological significanceof the effect of the nitrogen source on CAM photosynthesis arediscussed (Received January 5, 1988; Accepted April 13, 1988)     

Changes in Crassulacean Acid Metabolism of Kalanchoe blossfeldiana by Different Nitrogen Sources

Kalanchoe blossfeldiana Poelln. cv. Hikan (a Crassulacean acidmetabolism (CAM) plant) was grown in pots containing soil for6 months and then cultured in nutrient solution containing 10mM nitrate or ammonium as a sole nitrogen source for 2 or 3months, under a long-day (16 h) condition. Plant growth was better in the nitrate medium. Leaves of thenitrate-grown plants showed greater diurnal fluctuations intitratable acidity and malate content than those of the ammonium-grownplants. The diurnal patterns in CO₂ exchange of nitrate-grownplants were basically similar for both groups, but the amountof net CO₂ uptake at night was twice as large in the nitrate-grownplants. The leaves of the nitrate-grown plants had 1.3 to 2.5times higher activities of phosphoenolpyruvate carboxylase (PEPC),phosphofructokinase (PFK) and NAD glycelaldehyde-3-phosphatedehydrogenase (G3PDH). These results indicate that K. blossfeldianagrown in nitrate medium showed more CAM activity than thosein ammonium medium. (Received August 13, 1987; Accepted February 22, 1988)