The effect of modified atmospheres on the survival of the eggs of four storage mite species

The results of a laboratory investigation into the effects of modified atmospheres (MA) on the eggs of mite pests of grain and cheese are presented. Four species of astigmatid mite were tested; Acarus farris (Oudemans). A. siro L., Lepidoglyphus destructor (Schrank) and Tyrophagus longior (Gervais). All are found in many habitats including grain and cheese stores. Three low oxygen (O2) MA mixtures were used, based on carbon dioxide (CO2), nitrogen (N2) or simulated burner gas (0.5 or 2% O2, 10% CO2, balance N2) plus 60% CO2 in air (8% O2). The mites were exposed at 15 degrees C and 80% r.h., a combination of conditions that occurs at the surface of stored grain during the autumn which promotes mite population growth. The exposure periods required to prevent egg hatch for each species in every mixture are given. Tyrophagus longior was the most tolerant species, followed by A. siro and A. farris, with L. destructor the most susceptible. Burner gas was the most effective mixture overall with 0.5% O2 but with an increase in the O2 level to 2% for all the mixtures, CO2 became the more effective control agent. With 60% CO2 in air some loss of efficacy was observed against the three most tolerant species and even more so for L. destructor. Sublethal exposures to MAs for at least 4 days in L. destructor, 6 days in A. farris and A. siro and 8 days for T. longior caused a delay in egg hatch.     

Somatotropic axis in hypocretin-deficient narcoleptic humans: altered circadian distribution of GH-secretory events

Narcolepsy is a sleep disorder caused by impaired hypocretin (orexin) neurotransmission. Growth hormone (GH) secretion may be altered in narcolepsy for various reasons. Slow-wave sleep episodes, which are closely associated with GH-secretory events, are more randomly dispersed over 24 h in narcoleptics. Furthermore, hypocretins may inhibit pituitary GH release. We assessed the function of the somatotropic axis in narcolepsy by deconvolving 24-h (10-min sampling interval) plasma GH concentration profiles in seven hypocretin-deficient narcoleptic patients and in seven healthy controls matched for age, sex, and body weight. Both basal and pulsatile GH secretion rate and secretagogue-induced GH release were similar in patients and controls. However, narcoleptics secreted approximately 50% of their total production during the daytime, whereas controls secreted only 25% during the day. Also, the GH output pattern of narcoleptics was significantly less regular. We propose that hypocretin deficiency disrupts the circadian distribution of hypothalamic GH-releasing hormone release in narcoleptic patients to simultaneously cause daytime GH release and promote their propensity to fall asleep during the day.     

Glucose-dependent insulinotropic polypeptide receptor null mice exhibit compensatory changes in the enteroinsular axis

The incretins glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are gut hormones that act via the enteroinsular axis to potentiate insulin secretion from the pancreas in a glucose-dependent manner. Both GLP-1 receptor and GIP receptor knockout mice (GLP-1R(-/-) and GIPR(-/-), respectively) have been generated to investigate the physiological importance of this axis. Although reduced GIP action is a component of type 2 diabetes, GIPR-deficient mice exhibit only moderately impaired glucose tolerance. The present study was directed at investigating possible compensatory mechanisms that take place within the enteroinsular axis in the absence of GIP action. Although serum total GLP-1 levels in GIPR knockout mice were unaltered, insulin responses to GLP-1 from pancreas perfusions and static islet incubations were significantly greater (40-60%) in GIPR(-/-) than in wild-type (GIPR(+/+)) mice. Furthermore, GLP-1-induced cAMP production was also elevated twofold in the islets of the knockout animals. Pancreatic insulin content and gene expression were reduced in GIPR(-/-) mice compared with GIPR(+/+) mice. Paradoxically, immunocytochemical studies showed a significant increase in beta-cell area in the GIPR-null mice but with less intense staining for insulin. In conclusion, GIPR(-/-) mice exhibit altered islet structure and topography and increased islet sensitivity to GLP-1 despite a decrease in pancreatic insulin content and gene expression.     

Selective toxicity of engineered lentivirus lytic peptides in a CF airway cell model

Lentivirus lytic peptides (LLPs) are derived from HIV-1 and have antibacterial properties. LLP derivatives (eLLPs) were engineered for greater potency against Staphylococcus aureus (SA) and Pseudomonas aeruginosa (PA). Minimum bactericidal concentration (MBC) was determined in low and physiologic salt concentrations. MBC was decreased against SA and equivalent against PA in physiologic salt when compared to the parent compound LLP1. In a novel cystic fibrosis (CF) airway cell model, one derivative, WLSA5, reduced the number of adherent PA and only moderately affected CF cell viability. Overall, eLLPs are selectively toxic to bacteria and may be useful against CF airway infections.     

Efficient use of a 'dead-end' GA 5' splice site in the human fibroblast growth factor receptor genes

We have investigated use of a conserved non-canonical GA 5' splice site present in vertebrate fibroblast growth factor receptor (FGFR) genes. Despite previous studies suggesting that GA at the beginning of an intron is incompatible with splicing, we observe efficient utilization of this splice site for human FGFR1 gene constructs. We show that use of the GA splice site is dependent on both a conventional splice site six nucleotides upstream and sequence elements within the downstream intron. Furthermore, our results are consistent with competition between the tandem 5' splice sites being mediated by U6 snRNP, rather than U1 snRNP. Thus the GA 5' splice site represents an extension of the adjacent conventional 5' splice site, the first natural example of such a composite 5' splice site.     

Inhibition of nicotinoprotein (NAD+-containing) alcohol dehydrogenase by trans-4-(N,N-dimethylamino)-cinnamaldehyde binding to the active site

Ethanol oxidation by nicotinoprotein alcohol dehydrogenase (np-ADH) from the bacterium Amycolatopsis methanolica is inhibited by trans-4-(N,N-dimethylamino)-cinnamaldehyde through direct binding to the catalytic zinc ion in a substrate-like geometry. This binding is accompanied by a characteristic red shift of the aldehyde absorbance from 398 nm to 467 nm. Np-ADH is structurally related to mammalian ADH class I, and a model of np-ADH shows how the cinnamaldehyde derivative can be accommodated in the active site of the nicotinoprotein, correlating the structural and enzymological data.     

Ethnic variation in tyrosinase and TYRP1 expression in photoexposed and photoprotected human skin

The relative expression of a number of key mediators of human pigmentation including tyrosinase, tyrosinase related protein-1 (TYRP1), endothelin-1 and adrenocorticotrophic hormone (ACTH) proteins were analysed and quantified in immunohistochemically stained skin sections using semiquantitative computer assisted image analysis. Comparisons were made between a range of different ethnic skin types including European, Chinese, Mexican, Indian and African at both chronically photoexposed and photoprotected sites. Melanocyte number varied little with ethnicity except in the European group which had 60-80% more melanocytes than other skin types (P < 0.01, n = 10; Student Neuman-Keuls). However, melanocyte number was increased approximately twofold in chronically photoexposed skin of all ethnic groups (P < 0.001, n = 48; paired t-test). Tyrosinase protein expression in melanocytes did not vary with ethnicity, but TYRP1 protein was significantly elevated (approximately 2.6-fold) in darkly pigmented African and Indian skin types compared with lightly pigmented Mexican, Chinese and European skin types. In melanocytes from chronically photoexposed skin, there was a modest but significant increase in the expression of tyrosinase protein (approximately 1.2-fold, P < 0.001, n = 48; paired t-test), together with a significant and slightly larger increase in the expression of TYRP1 protein (approximately 1.6-fold, P < 0.005, n = 48; paired t-test). In contrast, the expression of endothelin-1 and ACTH showed no significant variation with either ethnicity or photoexposure. These data are consistent with the view that maintenance of a chronically hyperpigmented phenotype in chronically photoexposed human skin is largely the result of a stable increase in the number of tyrosinase positive melanocytes at these sites. Moreover, the observed ethnic variation in TYRP1 protein expression suggests that TYRP1 may play a significant role in mediating ethnic differences in melanogenesis and constitutive skin pigmentation in vivo.     

Comparison of the structural and physical properties of human hair eumelanin following enzymatic or acid/base extraction

Eumelanin was isolated from a sample of black, Indonesian human hair using three different published procedures: two different acid/base extractions and an enzymatic extraction. The morphology and spectroscopic properties of the isolated pigments differ significantly. The acid/base procedures both yield an amorphous material, while enzymatic extraction yields ellipsoidal melanosomes. Amino acid analysis shows that there is protein associated with the isolated pigments, accounting for 52, 40 and 14% of the total mass for the two acid/base extractions and the enzymatic extraction, respectively. The amino acid compositions do not correlate with those of keratin or tyrosinase. Metal elemental analysis shows that the acid/base extraction removes a majority of many metal ions bound to the pigment. Chemical degradation analysis by KMnO4/H+ and H2O2/OH- indicates significant differences between the pigments isolated by acid/base and enzymatic extraction. After correction for the protein mass in the two pigments, the lower yields of both pyrrole-2,3,5-tricarboxylic acid and pyrrole-2,3-dicarboxylic acid, eumelanin degradation products, indicate acid/base extraction modifies the chemical structure of the melanin, consistent with the result of Soluene solubilization assay. While the optical absorption spectra of the bulk pigments are similar, the spectra of the molecular weight less than 1000 mass fractions differ significantly. The data clearly indicate that pigment obtained from human hair by acid/base extraction contains significant protein, exhibits destruction of the melanosome, and possesses altered molecular structure. The acid/base extracted hair melanin is not representative of the natural material and is a poor model system for studying the physical and biological properties of melanins. The enzymatically extracted hair melanin, on the contrary, retains the morphology of intact melanosomes and is an excellent source of human melanin.     

Components of spatial patterning in a serpentine grassland

We analyzed the components of spatial patterning in species abundance in a diverse grassland dominated by early season, annual forbs. Species abundance, soil depth and gopher disturbances were measured by means of a nested spatial design on two 8m×20m plots that differed in the amount of larger scale variability in soil depth. Species distributions at the scale of the 10cm×10cm quadrat were highly clumped, with a decline in clumping with mean abundance. Even with the effect of abundance on clumping removed, species showed differences in the degree of clumping and these differences were consistent between the two plots. The abundance of the species and the frequency of disturbance correlated weakly to moderately with soil depth. Semivariance analyses indicated that the most common species all showed complex spatial patterning at a range of scales. Some of this variation corresponded to patterns of soil depth variation and patterns of gopher disturbance; however, a large amount of the spatial patterning in species abundance remains unexplained.