Production of Poly-β-Hydroxyalkanoic Acid by Pseudomonas cepacia

The possibility of using the nutritionally versatile bacterium Pseudomonas cepacia to produce poly-β-hydroxyalkanoic acid was evaluated. Chemostat culture showed that growth of P. cepacia became nitrogen limited when the molar carbon-to-nitrogen ratio of the medium fed into the fermentor was above 15. When grown under nitrogen limitation in batch culture with fructose as the sole source of carbon, P. cepacia accumulated poly-β-hydroxybutyric acid (PHB) in excess of 50% of the dry weight of its biomass. In batch culture, almost no PHB was produced until the onset of nitrogen limitation. After this point, PHB was produced at a linear rate of 0.12 g liter⁻¹ h⁻¹ (from a constant value of 1.6 g of cellular protein liter⁻¹). PHB produced by P. cepacia had a weight-average molecular weight of 5.37 × 10⁵ g mol⁻¹ and a polydispersivity index of 3.9. Poly(β-hydroxybutyric acid-β-hydroxyvaleric acid) copolymer was produced with a poly-β-hydroxybutyric acid-poly-β-hydroxyvaleric acid ratio of up to 30% by weight when propionic acid was added to the medium.     

Adenosine, a cytoprotective autocoid: effects of adenosine on neutrophil plasma membrane viscosity and chemoattractant receptor display

At inflammatory sites neutrophils are stimulated to produce a variety of toxic agents, yet rarely harm the endothelium across which they migrate. We have recently found that endothelium releases adenosine which, acting via receptors on the surface of human neutrophils, inhibits generation of toxic metabolites by stimulated neutrophils but, paradoxically, promotes chemotaxis. Agents which diminish plasma membrane viscosity affect neutrophil function similarly, possibly by modulating chemoattractant receptor number or affinity. We therefore determined whether adenosine receptor agonists modulate neutrophil function by decreasing membrane viscosity and/or chaning the affinity of chemoattractant (N-fMet-Leu-Phe, FMLP) receptors. Surprisingly, 5′-(N-ethylcar☐amido)adenosine (NECA, 10 μM), the most potent agonist at neutrophil adenosine receptors, increased plasma membrane viscosity, as measured by fluorescence anisotropy of the plasma membrane specific probe 1-(4-trimethylaminophenyl)-6-diphenyl-1,3,5-hexatriene (TMA-DPH), in unstimulated neutrophils from a mean microviscosity of 1.67 ± 0.02 (S.E.) to 1.80 ± 0.02 (p < 0.001) while inosine (10 μM), a poor adenosine receptor agonist, had no effect (1.73 ± 0.04, p =n.s. vs. control, p < 0.01 vs. NECA). Adenosine receptor agonists increased plasma membrane viscosity in neutrophils with the same order of potency previously seen for inhibition of superoxide anion generation and enhancement of chemotaxis (NECA > adenosine = N⁶-phenylisopropyladenosine). The adenosine receptor antagonist 8-(p-sulfophenyl)theophylline reversed the effect of NECA on plasma membrane viscosity. Unlike other agents which modulate plasma membrane viscosity, NECA (10 μM) did not significantly change the number or affinity of [³H]FMLP binding sites on neutrophils. In contrast to the hypothesis of Yuli et al. these results indicate that occupancy of adenosine receptors on neutrophils increases plasma membrane viscosity without affecting chemoattractant receptor display.     

Different patterns of glycolipid antigens are expressed following differentiation of TERA-2 human embryonal carcinoma cells induced by retinoic acid, hexamethylene bisacetamide (HMBA) or bromodeoxyuridine (BUdR)

NTERA-2 cl.D1 human embryonal carcinoma (EC) cells were induced to differentiate by either bromodeoxyuridine (BUdR) or hexamethylene bisacetamide (HMBA), and also by retinoic acid. Following exposure to each of these inducers, the globoseries glycolipid antigens stage-specific embryonic antigens -3 and -4 (SSEA-3 and -4) and the glycoprotein antigen TRA-1-60, all characteristic of the human EC cell surface, underwent a marked reduction in expression within about 7 days. At the same time, the lactoseries glycolipid antigen SSEA-1, and ganglioseries antigens A2B5 (GT3) and ME311 (9-0-acetyl GD3) were induced in BUdR- and retinoic acid-treated cells. However, these antigens did not appear during the first 7-14 days of HMBA-induced differentiation. The observations of cell surface antigen expression were paralleled by analysis of glycolipids isolated from the cells by thin-layer chromatography. This analysis, in which the new monoclonal antibodies VINIS-56 and VIN-2PB-22 were included, also revealed expression of gangliosides GD3 and GD2 in all differentiated cultures, albeit at much lower levels following HMBA exposure than following retinoic acid or BUdR-exposure. Further, disialylparagloboside was detected in retinoic acid and BUdR-induced, but not HMBA-induced, cultures. Taken with morphological observations, the results suggest that HMBA induces differentiation of NTERA-2 cl.D1 EC cells along a pathway distinct from the pathway(s) induced by retinoic acid and BUdR.     

Breeding program for the lesser kudu (Tragelaphus imberbis) in North America

The lesser kudu (Tragelaphus imberbis) has been kept in North American zoological parks since 1930 but has never been a common species in collections. In 1987 this population totaled 28 animals: 15 males and 13 females. A pedigree evaluation in 1987 of the existing population indicated that eight effective founders and one potential founder were represented in the North American herd. Three new potential founders from European captive populations were added to the population in 1987 to increase the number of existing founder lines to 12 animals. As this species is not endangered or threatened in its native habitat, it is not a high priority to qualify for designation as an SSP species. Because of this, the institutions holding lesser kudu in North America decided to join informally and draft a breeding program to better manage this small captive population. This program was designed to minimize inbreeding and equalize genetic representation of founder animals to maximize genetic diversity. It requires a shift in management philosophy to establish stable groups of breeding females at participating institutions while rotating appropriate breeder males through these herds in a controlled manner to ensure minimization of inbreeding and maximization of genetic diversity. It is hoped that this program can serve as a model for the management of other small captive populations of non-SSP species.     

Hensen's node,but not other biological signallers,can induce supernumerary digits in the developing chick limb bud

Summary The purpose of this study was to determine whether the organizer regions of early avian and amphibian embryos could induce supernumerary (SN) wing structures to develop when they were grafted to a slit in the anterior side of stage 19–23 chick wing buds. Supernumerary digits developed in 43% of the wings that received anterior grafts of Hensen's node from stage 4–6 quail or chick embryos; in addition, 16% of the wings had rods of SN cartilage, but not recognizable SN digits. The grafted quail tissue did not contribute to the SN structures. When tissue anterior or lateral to Hensen's node or lateral pieces of the area pellucida caudal to Hensen's node were grafted to anterior slits, the wings usually developed normally. No SN structures developed when Hensen's nodes were grafted to posterior slits in chick wing buds. Wings developed normally when pieces of the dorsal lip of the blastopore from stage 10–11.5 frog (Xenopus laevis and Rana pipiens) embryos were grafted to anterior slits. No SN digits developed when other tissues that have limb-inducing activity in adult urodele amphibians [chick otic vesicle, frog (Rana pipiens) lung and kidney] or that can act as heteroinductors in neural induction (rat kidney, lung, submaxillary gland and urinary bladder; mouse liver and submaxillary gland) were grafted to anterior slits in chick wing buds. SN digits also failed to develop following preaxial grafts of chick optic vesicles. These results suggest that although the anteroposterior polarity of the chick wing bud can be influenced by factors other than the ZPA (e.g., Hensen's node, retinoids), the wing is not so labile that it can respond to a wide variety of inductively-active tissues.     

Distribution of FMRFamide-like immunoreactivity in the nervous system of the slug Limax maximus

Summary The distribution of FMRFamide-like immunoreactive neurons in the nervous system of the slug Limax maximus was studied using immunohistochemical methods. Approximately one thousand FMRFamide-like immunoreactive cell bodies were found in the central nervous system. Ranging between 15 m and 200 m in diameter, they were found in all 11 ganglia of the central nervous system. FMRFamide-like immunoreactive cell bodies were also found at peripheral locations on buccal nerve roots. FMRFamide-like immunoreactive nerve fibres were present in peripheral nerve roots and were distributed extensively throughout the neuropil and cell body regions of the central ganglia. They were also present in the connective tissue of the perineurium, forming an extensive network of varicose fibres. The large number, extensive distribution and great range in size of FMRFamide-like immunoreactive cell bodies and the wide distribution of immunoreactive fibres suggest that FMRFamide-like peptides might serve several different functions in the nervous system of the slug.