International Research Ethics

This article provides a critical overview of the most important issues pertaining to the ongoing debate on international research ethics. It critically describes three problems of continuing concern: 1) the question of whether the distinction between therapeutic and non-therapeutic research should be upheld; 2) the questions of whether the currently demanded best proven diagnostic and therapeutic method of treatment for all research subjects is feasible both in developed and in developing countries, and whether it should be upheld; 3) the questions of who owns international research ethics guidelines and regulatory frameworks and, how decisions about changes to such international guidelines can possibly be achieved, given that it seems to be the case that genuine disagreement about issues of content is possible and likely.     

13C NMR assignments of the protonated carbons of [d(TAGCGCTA)]2 by two-dimensional proton-detected heteronuclear correlation

The resonances of the protonated carbons of [d(TAGCGCTA)]2 have been assigned by the two-dimensional proton-detected double-quantum heteronuclear correlation experiment [( 1H-13C]-DQCOSY). 13C-coupled and 13C-decoupled versions of the experiment were used. The assignment method is discussed in detail. The deoxyribose cross peaks segregate into five well-resolved regions, and the base cross peaks have distinct features that are helpful for assignments. The cross peaks from the 1H-13C pairs at the Cyd5, Ado2 and ThdCH3 base positions fall in separate regions of the spectrum from each other; they also are resolved from the closely spaced Ado8, Guo8, Cyd6 and Thd6. Additional parameters for distinction of the base signals are their differing J-coupling values and long-range coupling patterns.     

13C NMR of the bases of three DNA oligonucleotide duplexes: assignment methods and structural features

Natural abundance 13C NMR spectra of three DNA oligomers have been obtained. Most of the base resonances are well resolved from one another. A combination of two independent methods was used in making assignments: a one-dimensional spectral comparison method and a two-dimensional proton-detected 1H-13C correlated experiment for the protonated carbons. There are large shielding changes (between 1.62 and -1.40 ppm) upon thermal dissociation of the duplex. The shapes of the chemical shift vs temperature curves are largely independent of sequence. The base carbon resonance frequencies are sensitive to hydrogen bonding, base stacking, sugar conformation, and changes in the glycosyl torsion angle.     

The effect of sugars on (pro)insulin biosynthesis

Rates of incorporation of [4,5-(3)H]leucine into insulin plus proinsulin, designated ;(pro)insulin', and total protein in rat pancreatic islets were measured. Glucose stimulates rates of total protein and (pro)insulin biosynthesis, but (pro)insulin biosynthesis is stimulated preferentially. Mannose and N-acetylglucosamine also stimulate (pro)insulin and total protein biosynthesis; inosine and dihydroxyacetone stimulate (pro)insulin biosynthesis specifically. Fructose does not stimulate (pro)insulin biosynthesis when tested alone, but does so in the presence of low concentrations of glucose, mannose or N-acetylglucosamine. Many glucose analogues do not stimulate (pro)insulin biosynthesis. Mannoheptulose inhibits synthesis of (pro)insulin and total protein stimulated by glucose or mannose but not by dihydroxyacetone, inosine or N-acetylglucosamine; phloretin (9mum) inhibits N-acetylglucosamine-stimulated (pro)insulin biosynthesis preferentially. The data are in agreement with the view that the same glucose-sensor mechanism may control both insulin release and biosynthesis, and ;substrate-site' model is suggested. The threshold for stimulation of biosynthesis of (pro)insulin and total protein is lower than that found for glucose-stimulated insulin release; moreover the biosynthetic response to an elevation of glucose concentration is slower than that found for insulin release. The physiological implication of these findings is discussed. Caffeine and isobutylmethylxanthine, at concentrations known to increase islet 3':5'-cyclic AMP and potentiate glucose-induced insulin release, were without effect on rates of glucose-stimulated (pro)insulin biosynthesis.     

Basolateral plasma membrane localization of ouabain-sensitive sodium transport sites in the secretory epithelium of the avian salt gland

The distribution of Na+ pump sites (Na+-K+-ATPase) in the secretory epithelium of the avian salt gland was demonstrated by freeze-dry autoradiographic analysis of [(3)H] ouabain binding sites. Kinetic studies indicated that near saturation of tissue binding sites occurred when slices of salt glands from salt-stressed ducks were exposed to 2.2 μM ouabain (containing 5 μCi/ml [(3)H]ouabain) for 90 min. Washing with label-free Ringer's solution for 90 min extracted only 10% of the inhibitor, an amount which corresponded to ouabain present in the tissue spaces labeled by [(14)C]insulin. Increasing the KCl concentration of the incubation medium reduced the rate of ouabain binding but not the maximal amount bound. In contrast to the low level of ouabain binding to salt glands of ducks maintained on a freshwater regimen, exposure to a salt water diet led to a more than threefold increase in binding within 9-11 days. This increase paralleled the similar increment in Na+-K+-ATPase activity described previously. [(3)H]ouabain binding sites were localized autoradiographically to the folded basolateral plasma membrane of the principal secretory cells. The luminal surfaces of these cells were unlabeled. Mitotically active peripheral cells were also unlabeled. The cell-specific pattern of [(3)H]ouabain binding to principal secretory cells and the membrane-specific localization of binding sites to the nonluminal surfaces of these cells were identical to the distribution of Na+-K+-ATPase as reflected by the cytochemical localization of ouabain-sensitive and K+-dependent nitrophenyl phosphatase activity. The relationship between the nonluminal localization of Na+-K+-ATPase and the possible role of the enzyme n NaCl secretion is considered in the light of physiological data on electrolyte transport in salt glands and other secretory epithelia.     

Expression of voltage-gated K+ channels in insulin-producing cells. Analysis by polymerase chain reaction.

We have used the polymerase chain reaction (PCR) with primers against the S5 and S6 regions of voltage-gated K+ channels to identify 8 different specific amplification products using poly(A)+ RNA isolated from islets of Langerhans from obese hyperglycemic (ob/ob) mice and from the two insulin-producing cell lines HIT T15 and RINm5F. Sequence analysis suggests that they derive from mRNAs coding for a family of voltage-gated K+ channels; 5 of these have been recently identified in mammalian brain and 3 are novel. These hybridize in classes to different mRNAs which distribute differently to a number of tissues and cell lines including insulin-producing cells.     

Protein kinase activities in rat pancreatic islets of Langerhans.

1. Protein kinase activities in homogenates of rat islets of Langerhans were studied. 2. On incubation of homogenates with [gamma-32P]ATP, incorporation of 32P into protein occurred: this phosphorylation was neither increased by cyclic AMP nor decreased by the cyclic AMP-dependent protein kinase inhibitor described by Ashby & Walsh [(1972) J. Biol. Chem. 247, 6637--6642]. 3. On incubation of homogenates with [gamma-32P]ATP and histone as exogenous substrate for phosphorylation, incorporation of 32P into protein was stimulated by cyclic AMP (approx. 2.5-fold) and was inhibited by the cyclic AMP-dependent protein kinase inhibitor. In contrast, when casein was used as exogenous substrate, incorporation of 32P into protein was not stimulated by cyclic AMP, nor was it inhibited by the cyclic AMP-dependent protein kinase inhibitor. 4. DEAE-cellulose ion-exchange chromatography resolved four peaks of protein kinase activity. One species was the free catalytic subunit of cyclic AMP-dependent protein kinase, two species corresponded to 'Type I' and 'Type II' cyclic AMP-dependent protein kinase holoenzymes [see Corbin, Keely & Park (1975) J. Biol. Chem. 250, 218--225], and the fourth species was a cyclic AMP-independent protein kinase. 5. Determination of physical and kinetic properties of the protein kinases showed that the properties of the cyclic AMP-dependent activities were similar to those described in other tissues and were clearly distinct from those of the cyclic AMP-independent protein kinase. 6. The cyclic AMP-independent protein kinase had an s20.w of 5.2S, phosphorylated a serine residue(s) in casein and was not inhibited by the cyclic AMP-dependent protein kinase inhibitor. 7. These studies demonstrate the existence in rat islets of Langerhans of multiple forms of cyclic AMP-dependent protein kinase and also the presence of a cyclic AMP-independent protein kinase distinct from the free catalytic subunit of cyclic AMP-dependent protein kinase. The presence of the cyclic AMP-independent protein kinase may account for the observed characteristics of 32P incorporation into endogenous protein in homogenates of rat islets.     

Growth,behaviour, and educational achievement of Jamaican children with sickle-cell trait.

A longitudinal study of the mental and physical development of 200 children with normal haemoglobin and 21 with the sickle-cell trait was carried out in a small rural community in Jamaica. At about 2 and 10 years of age heights and weights showed no significant differences. At about 10 years of age classroom behaviour, sociability, and educational achievement were similar. The results suggest that the sickle-cell trait does not affect growth and mental development.     

Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study

The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions.     

A multiscale optimisation method for bone growth scaffolds based on triply periodic minimal surfaces

Tissue engineered bone scaffolds are potential alternatives to bone allografts and autografts. Porous scaffolds based on triply periodic minimal surfaces (TPMS) are good candidates for tissue growth because they offer high surface-to-volume ratio, have tailorable stiffness, and can be easily fabricated by additive manufacturing. However, the range of TPMS scaffold types is extensive, and it is not yet clear which type provides the fastest cell or tissue growth while being sufficiently stiff to act as a bone graft. Nor is there currently an established methodology for TPMS bone scaffold design which can be quickly adopted by medical designers or biologists designing implants. In this study, we examine six TPMS scaffold types for use as tissue growth scaffolds and propose a general methodology to optimise their geometry. At the macro-scale, the optimisation routine ensures a scaffold stiffness within suitable limits for bone, while at the micro-scale it maximises the cell growth rate. The optimisation procedure also ensures the scaffold pores are of sufficient diameter to allow oxygen and nutrient delivery via capillaries. Of the examined TPMS structures, the Lidinoid and Split P cell types provide the greatest cell growth rates and are therefore the best candidates for bone scaffolds.