t(21q21q)/r[t(21q21q)] mosaic in two unrelated patients with mild stigmata of Down's syndrome

Two cases of t(21q21q)/r[t(21q21q)] mosaic in unrelated infants, 17 and 14 months old respectively are reported. The proportion of cells with the ring chromosome was 45% in the former, 80% in the latter. Both cases had mild manifestations of the Down's syndrome. The origin of this unusual mosaicism as well as the significance of the difference in the proportions of the ring chromosome in the two have been discussed.     

Cystine accumulation in cystinotic fibroblasts from free and protein-linked cystine but not cysteine

The accumulation of cystine in cystinotic fibroblasts from free and protein-linked cystine has been investigated. Cystine is not accumulated from cysteine but is readily accumulated from cystine. The accumulation from free cystine does not occur as a result of pinocytosis or from the degradation of a rapidly metabolized protein pool. Further studies of the degradation of disulphide-containing proteins by these cells may aid understanding of the mechanisms of proteolysis.     

The regulation of glycoprotein synthesis by cAMP in Dictyostelium

Dictyostelium discoideum (Dd) 1-H vegetative amoebae exposed to cAMP differentiate into mature stalk cells within 48 h [6]. It was of interest to monitor the patterns of glycoprotein synthesis in the amoebae during the first 5 h of exposure to cAMP and phosphate buffer (PB) controls. Following the exposure period the amoebae were labeled with -[6-³H]fucose. It was determined by both silver grain counts of autoradiographs and scintillation spectroscopy that within minutes cAMP effects an inhibition of [³H]fucose incorporation. However, by 5 h of exposure both experimentals and controls lose a major amount of their labeling capacity based upon the initial PB control value. Vegetative amoebae exposed to cAMP mimics the sparse labeling found in prestalk cells. Prestalk cells synthesize cellulose as a result of cAMP-induced gluconeogenesis and consequently glycoprotein synthesis is reduced. Cellular interactions promoted by cAMP appears to initiate prestalk cell differentiation during the pre-aggregation phase of development. This event is accompanied by a loss in the ability of the aggregating cells to synthesize glycoprotein.     

Identification of glycoproteins in goblet cells of epidermis and gill of plaice (Pleuronectes platessa L.), flounder (Platichthys flesus (L.)) and rainbow trout (Salmo gairdneri Richardson)

Synopsis A quantitative analysis has been made of the glycoproteins present in the goblet cells of the epidermis, gill filaments and gill lamellae of three species of teleost fish. The glycoproteins have been identified by a combination of techniques, including the use of the enzyme sialidase followed by Alcian Blue staining, at pH 2.6 or I. o, in combination with periodic acid-Schiff. The selected fish were representative of species living in marine, freshwater and estuarine environments.The range of glycoproteins identified in these fish was similar to that found in mammalian tissue in that both neutral and acid glycoproteins were present, the latter included both sialomucins sensitive and resistant to sialidase, and sulphomucin. A single goblet cell contained either neutral or acid glycoproteins alone or in combination. Only the epidermis of the plaice and rainbow trout contained uniform cell populations producing acid glycoproteins, the former sulphomucin and the latter mainly sialomucin. At each site in the flounder and in the gill epithelia of the plaice and rainbow trout, the goblet cell population was mixed, with cells producing each type of glycoprotein. The number of goblet cells producing each type of glycoprotein varied at each tissue site.     

Recognition of the neural chemoattractant Netrin-1 by integrins alpha6beta4 and alpha3beta1 regulates epithelial cell adhesion and migration

Netrins, axon guidance cues in the CNS, have also been detected in epithelial tissues. In this study, using the embryonic pancreas as a model system, we show that Netrin-1 is expressed in a discrete population of epithelial cells, localizes to basal membranes, and specifically associates with elements of the extracellular matrix. We demonstrate that alpha6beta4 integrin mediates pancreatic epithelial cell adhesion to Netrin-1, whereas recruitment of alpha6beta4 and alpha3beta1 regulate the migration of CK19+/PDX1+ putative pancreatic progenitors on Netrin-1. These results provide evidence for the activation of epithelial cell adhesion and migration by a neural chemoattractant, and identify Netrin-1/integrin interactions as adhesive/guidance cues for epithelial cells.     

Adult:Child Differences in the Intraspecies Uncertainty Factor: A Case Study Using Lead

Adults and children differ in their susceptibility to the toxic effects of lead. Lead was therefore used as a case study to evaluate intraspecies differences by comparing the adult and child minimal Lowest Observed Adverse Effect Level (LOAEL) or the No Observed Adverse Effect Level (NOAEL), allowing an evaluation of the ten-fold intraspecies uncertainty factor (UF). The lead intakes (in µg/kg/d) necessary to achieve target blood lead (PbB) levels reflecting the minimal LOAEL or NOAEL were determined using biokinetic slope factors (BKSFs), which relate lead uptake to PbB levels. The analyses assumed chronic, low-level oral exposure to lead, and the response of a typical adult and child. Child analyses used a target geometric mean (GM) PbB of 4.6?µg/dL (95% of population <10?µg/dL), resulting in lead intakes of 1.9?µg/kg/day (assuming 100% soluble lead) and 4.9?µg/kg/day (assuming 25% soluble lead and 75 % soil lead). Adult analyses assumed intake of 100 % soluble lead, and used target GM PbB levels of 4.2?µg/dL (95% of population <11.1 µg/dL) and 11.4?µg/dL (95% of population <30?µg/dL), resulting in lead intakes of 1.9?µg/kg/day and 5.1?µg/kg/day, respectively. The results indicate that despite the greater vulnerability of young children to the effects of lead as compared to adults, the minimal LOAEL or NOAEL for lead is remarkably similar between children and adults. In this case, the application of a tenfold intraspecies uncertainty factor to adjust the adult minimal LOAEL or NOAEL for a child would be unnecessary, despite the well-established vulnerability of children to lead.     

Effects of environmental conditions on isoprene emission from live oak

Live-oak plants (Quercus virginiana Mill.) were subjected to various levels of CO₂, water stress or photosynthetic photon flux density to test the hypothesis that isoprene biosynthesis occurred only under conditions of restricted CO₂ availability. Isoprene emission increases as the ambient CO₂ concentration decreased, independent of the amount of time that plants had photosynthesized at ambient CO₂ levels. When plants were water-stressed over a 4-d period photosynthesis and leaf conductance decreased 98 and 94%, respectively, while isoprene emissions remained constant. Significant isoprene emissions occurred when plants were saturated with CO₂, i.e., below the light compensation level for net photosynthesis (100 mol m^-2 s^-1). Isoprene emission rates increased with photosynthetic photon flux density and at 25 and 50 mol m^-2 s^-1 were 7 and 18 times greater than emissions in the dark. These data indicate that isoprene is a normal plant metabolite and not — as has been suggested — formed exclusively in response to restricted CO₂ or various stresses.Abbreviation PPFD photosynthetic photon flux density     

BSD2 is a Rubisco‐specific assembly chaperone,forms intermediary hetero‐oligomeric complexes,and is nonlimiting to growth in tobacco

The folding and assembly of Rubisco large and small subunits into L₈S₈ holoenzyme in chloroplasts involves many auxiliary factors, including the chaperone BSD2. Here we identify apparent intermediary Rubisco‐BSD2 assembly complexes in the model C₃ plant tobacco. We show BSD2 and Rubisco content decrease in tandem with leaf age with approximately half of the BSD2 in young leaves (~70 nmol BSD2 protomer.m²) stably integrated in putative intermediary Rubisco complexes that account for <0.2% of the L₈S₈ pool. RNAi‐silencing BSD2 production in transplastomic tobacco producing bacterial L₂ Rubisco had no effect on leaf photosynthesis, cell ultrastructure, or plant growth. Genetic crossing the same RNAi‐bsd2 alleles into wild‐type tobacco however impaired L₈S₈ Rubisco production and plant growth, indicating the only critical function of BSD2 is in Rubisco biogenesis. Agrobacterium mediated transient expression of tobacco, Arabidopsis, or maize BSD2 reinstated Rubisco biogenesis in BSD2‐silenced tobacco. Overexpressing BSD2 in tobacco chloroplasts however did not alter Rubisco content, activation status, leaf photosynthesis rate, or plant growth in the field or in the glasshouse at 20°C or 35°C. Our findings indicate BSD2 functions exclusively in Rubisco biogenesis, can efficiently facilitate heterologous plant Rubisco assembly, and is produced in amounts nonlimiting to tobacco growth.     

A restatement of recent advances in the natural science evidence base concerning neonicotinoid insecticides and insect pollinators

A summary is provided of recent advances in the natural science evidence base concerning the effects of neonicotinoid insecticides on insect pollinators in a format (a ‘restatement'') intended to be accessible to informed but not expert policymakers and stakeholders. Important new studies have been published since our recent review of this field (Godfray et al. 2014 Proc. R. Soc. B 281, 20140558. (doi:10.1098/rspb.2014.0558)) and the subject continues to be an area of very active research and high policy relevance.