Vitamin A and bone formation. Different responses to retinol and retinoic acid of chick bone cells in organ culture

The response of bone cells in organ culture to retinol and retinoic acid was studied. Both stimulated incorporation of [3H]thymidine into DNA by 16-day embryonic chick calvaria, but the time-course of the responses differed; the peak responses to retinol and retinoic acid occurred at about 18 h and 48 h, respectively. Although retinol inhibited chick bone collagen synthesis retinoic acid had no effect, but it did stimulate non-collagenous protein synthesis, whereas the effect on the latter of retinol was, if anything, inhibitory. When present with retinol, retinoic acid was able to attenuate the inhibitory effect of the former on chick bone collagen synthesis, but preincubation with retinoic acid had no such effect. In neonatal murine calvarial cultures, retinoic acid inhibited collagen synthesis selectively in the same manner as did retinol. The ability of chick osteoblasts to respond differently to retinol and retinoic acid suggests that both forms of the vitamin may have a role in bone formation and that their intracellular models of action may differ although the attenuation response indicates there may be some interaction between the two.     

Ultrastructural changes occurring during germination and outgrowth of spores of the thermophile Bacillus acidocaldarius

Spores of the thermophilic, acidophilic, Bacillus acidocaldarius were covered by a thick outer coat and a laminated inner coat (5.5 nm periodicity). Small membranous vesicles were present in the spore core and they disappeared as germination proceeded. After depolymerization of the cortex, and a 30% increase in spore diameter, a localized gap appeared in the laminated inner coat only. This inner coat gap was narrow and could be the whole length of the spore. The germ cell appeared to grow, or to be pushed towards the inner coat gap, at which stage the outer coat disappeared in the same localized area. As the vegetative cell grew out the spore coat fell away, with loose cortical material still attached to it. The young germ cell developed a large spherical electron dense inclusion body in the cytoplasm, at the same time as the ribosomal and nuclear areas became distinct.     

Purification and analysis of isoforms of soluble immune response suppressor (SIRS)

Soluble immune response suppressor (SIRS) isolated from the T cell hybrid 393D2.6 was originally reported to exist as at least two m.w. forms and to migrate on reverse-phase high-performance liquid chromatography columns as three separate species. In experiments presented here, a further analysis of the different chromatographic forms of SIRS has been carried out. SIRS-alpha elutes from C-18 reverse-phase columns in 20% propanol. When SIRS-alpha is subjected to isoelectric focusing, three biologically active species are isolated at approximately pH7, approximately pH6, and approximately pH5 (SIRS-alpha 7, SIRS-alpha 6, and SIRS-alpha 5, respectively). SIRS-beta elutes in 30% propanol, and on isoelectric focusing the biologic activity is found only at approximately pH7 (SIRS-beta 7). Both the alpha and beta forms of SIRS have nearly identical m.w. when subjected to molecular sieve chromatography and migrate with a m.w. of 11,000. The molecular basis for these isoforms is not yet clear but is consistent with earlier studies showing two separate messenger RNA species coding for SIRS.     

Association of an MHC Class II Haplotype with Increased Risk of Polymyositis in Hungarian Vizsla Dogs

A breed-specific polymyositis is frequently observed in the Hungarian Vizsla. Beneficial clinical response to immunosuppressive therapies has been demonstrated which points to an immune-mediated aetiology. Canine inflammatory myopathies share clinical and histological similarities with the human immune-mediated myopathies. As MHC class II associations have been reported in the human conditions we investigated whether an MHC class II association was present in the canine myopathy seen in this breed. 212 Hungarian Vizsla pedigree dogs were stratified both on disease status and degree of relatedness to an affected dog. This generated a group of 29 cases and 183 “graded” controls: 93 unaffected dogs with a first degree affected relative, 44 unaffected dogs with a second degree affected relative, and 46 unaffected dogs with no known affected relatives. Eleven DLA class II haplotypes were identified, of which, DLA-DRB1*02001/DQA1*00401/DQB1*01303, was at significantly raised frequency in cases compared to controls (OR = 1.92, p = 0.032). When only control dogs with no family history of the disease were compared to cases, the association was further strengthened (OR = 4.08, p = 0.00011). Additionally, a single copy of the risk haplotype was sufficient to increase disease risk, with the risk substantially increasing for homozygotes. There was a trend of increasing frequency of this haplotype with degree of relatedness, indicating low disease penetrance. These findings support the hypothesis of an immune-mediated aetiology for this canine myopathy and give credibility to potentially using the Hungarian Vizsla as a genetic model for comparative studies with human myositis.     

Potentiation of synaptic responses in slices from the chick forebrain.

Coronal slices, containing part of the medial hyperstriatum ventrale (MHV), were cut from the left forebrains of domestic chicks and maintained in vitro. Records were made of the field responses evoked in the MHV by local electrical stimuli provided at 0.1 Hz. Two 1 min periods of stimulation at 5 Hz, separated by 10 min, were used in attempts to induce a persistent increase in the size of the postsynaptic response to test stimulation at 0.1 Hz. This procedure produced a potentiation which usually lasted longer than 2 h. The probability of inducing this persistent potentiation of the response (PPR) is not distributed evenly over the whole anteroposterior length of the MHV but is higher in slices that also contain the septo-mesencephalic tract ventrally. These are the slices that contain the intermediate part of the medial hyperstriatum ventrale (IMHV); an area that is essential for early behavioural learning. At this level PPR is not confined to the IMHV. It can also be produced in the lateral neostriatum in response to similar local stimulation at 5 Hz. No PPR was observed in either the caudal ectostriatum, or the paleostriatum.     

Frequent,low‐amplitude disturbances drive high tree turnover rates on a remote,cyclone‐prone Polynesian island

Aim How important are frequent, low‐intensity disturbances to tree community dynamics of a cyclone‐prone forest? We tested the following hypotheses concerning the ‘inter‐cataclysm’ period on a remote Polynesian island: (1) tree turnover would be high and recruitment rates would be significantly higher than mortality; (2) low‐intensity disturbance would result in a marginal increase in tree mortality in the short term; (3) turnover would vary among species and would be associated with plant traits linked to differences in life history; and (4) mortality and recruitment events would be spatially non‐random. Location Tutuila, a volcanic island in the Samoan Archipelago, Polynesia. Methods We censused the tree (stem diameter ≥ 10 cm) community in 3.9 ha of tropical forest three times over a 10‐year period, 1998–2008. We calculated annual mortality, recruitment and turnover rates for 36 tree species. We tested for non‐random spatial patterns and predictors of mortality, and non‐random spatial patterns of tree recruitment. A 2004 cyclone passing within 400 km allowed us to measure the effects of a non‐cataclysmic disturbance on vital rates. Results Annual turnover was 2.8% and annual recruitment was 3.6%; these are some of the highest rates in the tropics, and likely to be a response to a cyclone that passed < 50 km from Tutuila in 1991. Species turnover rates over 10 years were negatively correlated with wood specific gravity, and positively correlated with annual stem diameter increment. Mortality was spatially aggregated, and a function of site, species and an individual’s growth rate. Recruitment was highest on ground with low slope. The low‐magnitude cyclone disturbance in 2004 defoliated 29% of all trees, but killed only 1.8% of trees immediately and increased annual mortality over 5 years by 0.7%. Main conclusions The inter‐cataclysm period on Tutuila is characterized by frequent, low‐amplitude disturbances that promote high rates of tree recruitment and create a dynamic, non‐equilibrium or disturbed island disequilibrium tree community. Species with low wood density and fast growth rates have enhanced opportunities for recruitment between cataclysms, but also higher probabilities of dying. Our results suggest that increases in the frequency of cyclone activity could shift relative abundances towards disturbance‐specialist species and new forest turnover rates.     

Development of a Prototype System for Archiving Integrative/Hybrid Structure Models of Biological Macromolecules

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