The effect of nitrogen deficiency on leaf anatomy of young spring barley plants

Spring barley cv. Spartan was cultivated in a complete and nitrogen lacking Richter’s solution. In other experimental variants the nitrogen was omitted after six days of cultivation in the complete nutrient solution or the nitrogen lacking solution was replaced with the complete solution after the same period of time. Anatomy of the second leaf blade was quantitatively analyzed after 12 days of cultivation. Continuous nitrogen deficiency resulted in thinning of the blade, reduction of the cross-section areas of the blade, vascular bundles and sclerenchyma region. The most sensitive reaction to the nitrogen deficiency was that of assimilation parenchyma. The values of characters of the other two investigated variants were between the control and permanent nitrogen lacking variant.     

A moderately repeated DNA sequence of wheat and rye genomes

A 371 base pair segment (bordered by Hind III and Eco RI cutting sites) of wheat embryo nuclear DNA has been cloned and sequenced. It is AT-rich (68%), shares some sequence features with autonomously replicating sequence (ARS) elements, and occurs in approximately 7600 copies per haploid genome. When used as probe for blot hybridization to Hind III-digested wheat DNA, it gives an irregular series of hybridization bands. Essentially the same hybridization pattern was observed for rye DNA. It is concluded that this segment is distributed irregularly but, apparently, according to the same rule in both wheat and rye genomes.     

Biological properties of prolactin-releasing peptide analogs with a modified aromatic ring of a C-terminal phenylalanine amide

Prolactin-releasing peptide (PrRP)-induced secretion of prolactin is not currently considered a primary function of PrRP, but the development of late-onset obesity in both PrRP and PrRP receptor knock-out mice indicates the unique anorexigenic properties of PrRP. In our recent study, we showed comparable potencies of peptides PrRP31 and PrRP20 in binding, intracellular signaling and prolactin release in pituitary RC-4B/C cells, and anorexigenic effect after central administration in fasted mice. In the present study, eight analogs of PrRP20 with C-terminal Phe amide modified with a bulky side chain or a halogenated aromatic ring revealed high binding potency, activation of mitogen-activated protein kinase/extracellular-regulated kinase (MAPK/ERK1/2) and cAMP response element-binding protein (CREB) and prolactin release in RC-4B/C cells. In particular, [PheNO₂³¹]PrRP20, [1-Nal³¹]PrRP20, [2-Nal³¹]PrRP20 and [Tyr³¹]PrRP20 showed not only in vitro effects comparable or higher than those of PrRP20, but also a very significant and long-lasting anorexigenic effect after central administration in fasted mice. The design of potent and long-lasting PrRP analogs with selective anorexigenic properties promises to contribute to the study of food intake disorders.     

Overexpression of Full-Length Centrobin Rescues Limb Malformation but Not Male Fertility of the Hypodactylous (hd) Rats

Rat hypodactyly (hd) mutation is characterized by abnormal spermatogenesis and sperm decapitation, limb malformation (missing digits II and III) and growth retardation. We have previously reported centrobin (centrosome BRCA2-interacting protein) truncation at the C-terminus in the hd mutant. Here, we report data from a transgenic rescue experiment carried out to determine a role of centrobin in pathogenesis of hd. The transgenic construct, consisting of full-length-coding cDNA linked to a ubiquitous strong promoter/enhancer combination, was inserted to chromosome 16 into a LINE repeat. No known gene is present in the vicinity of the insertion site. Transgenic centrobin was expressed in all tissues tested, including testis. Transgenic animals show normal body weight and limb morphology as well as average weight of testis and epididymis. Yet, abnormal spermatogenesis and sperm decapitation persisted in the transgenic animals. Western blotting showed the coexistence of full-length and truncated or partially degraded centrobin in sperm of the rescued transgenic animals. Immunocytochemistry showed a buildup of centrobin and ODF2 (outer dense fiber 2) at the sperm decapitation site in the hd mutant and rescued transgenic rats. Additional findings included bulge-like formations and thread-like focal dissociations along the sperm flagellum and the organization of multiple whorls of truncated sperm flagella in the epididymal lumen. We conclude that centrobin is essential for normal patterning of the limb autopod. Centrobin may be required for stabilizing the attachment of the sperm head to flagellum and for maintaining the structural integrity of the sperm flagellum. We postulate that the presence of truncated centrobin, coexisting with full-length centrobin, together with incorrect timing of transgenic centrobin expression may hamper the rescue of fertility in hd male rats.     

ARF6 Regulates Neuron Differentiation through Glucosylceramide Synthase

The small GTPase ADP ribosylation factor 6 (ARF6) mediates endocytosis and has in addition been shown to regulate neuron differentiation. Here we investigated whether ARF6 promotes differentiation of Neuro-2a neuronal cells by modifying the cellular lipid composition. We showed that knockdown of ARF6 by siRNA in Neuro-2a cells increased neuronal outgrowth as expected. ARF6 knockdown also resulted in increased glucosylceramide levels and decreased sphingomyelin levels, but did not affect the levels of ceramide or phospholipids. We speculated that the ARF6 knockdown-induced increase in glucosylceramide was caused by an effect on glucosylceramide synthase and, in agreement, showed that ARF6 knockdown increased the mRNA levels and activity of glucosylceramide synthase. Finally, we showed that incubation of Neuro-2a cells with the glucosylceramide synthase inhibitor D-threo-1-phenyl-2-decanoylamino-3-morpholino-1-propanol (D-PDMP) normalized the increased neuronal outgrowth induced by ARF6 knockdown. Our results thus show that ARF6 regulates neuronal differentiation through an effect on glucosylceramide synthase and glucosylceramide levels.