F.t.-i.r. and laser-Raman spectra of thymine and thymidine

F.t.-i.r. and laser-Raman spectra of thymine and thymidine in the solid state were recorded. Assignments were proposed for the frequencies observed. The influence of the deoxy sugar on the vibrations of the nucleoside are discussed as a function of its particular puckering. The aim of this work is to elucidate the differences between the molecules constituting the nucleic acids, in order the better to comprehend their biological functions.     

F.t.-i.r. and laser-Raman spectra of cytosine and cytidine

Fourier-transform infrared (F.t.-i.r.) and laser-Raman spectra of cytosine and cytidine in the solid state have been recorded and assignments of the frequencies made. Comparison of the observed frequencies for cytosine with those for cytidine permits identification of the bands characteristic of the sugar on the one hand, and of the pyrimidine base on the other.     

R.b.e. and o.e.r. of extended-Bragg-peak helium ions: survival and development of rat embryos.

Rats were exposed under aerobic or hypoxic conditions to 200-1200 rads of 60Co gamma-rays or extended-Bragg-peak helium ions on the eighth day of gestation. Uterine contents were examined on the twentieth day of gestation. At the 50 per cent embryonic survival level, helium ion r.b.e. was 1(.0) (aerobic) and 1(.2) (hypoxic). Maximum attainable gamma-ray and helium-ion o.e.r.s. were 2(.2) and 1(.7) respectively, indicating an oxygen-effect gain (o.e.g.) of 1(.2). At the 10 per cent survival level helium ion r.b.e. was 1(.1) (aerobic) and 1(.4) (hypoxic). Gamma-ray and helium-ion 0.e.r.s. were 2(.0) and 1(.5) respectively, indicating a helium ion o.e.g. of 1(.3). These data demonstrate that the small fraction of high-LET radiation present in this helium ion beam has a neglible effect on the aerobic r.b.e., but lowers the effective o.e.r. of the beam approximately 25 per cent relative to that of gamma-rays. Helium ions were significantly more effective than gamma-rays in killing embryos under hypoxic conditions, in producing congenital abnormalities under aerobic conditions, and in stunting foetal growth under both conditions.     

F.t.-i.r. and laser-Raman spectra of guanine and guanosine

Fourier-transform infrared (F.t.-i.r.) and laser-Raman spectra have been obtained for solid guanine. The F.t.-i.r. spectrum of guanosine in the solid state was also recorded. Assignments are proposed for the i.r. bands. The molecular basis of the spectral differences between guanine and guanosine are discussed.     

1H- and 13C-N.M.R. spectra of eledoisin and intermediate oligopeptides.

The 1H- and 13C-n.m.r. spectra of eledoisin and minor oligopeptides were measured and assigned. The proton spectra were interpreted on the basis of homonuclear decoupling, chemical shift criteria and spectra simulation. The information obtained was used in the assignment of the 13C spectrum via heteronuclear 1H-13C. The steric arrangement of proline residue was deduced from the 13C spectrum. Moreover the similarity of the 13C spectrum of eledoisin with that of component oligopeptides suggests that no considerable conformational change occurs in the undecapeptide relative to the component fragments.     

Neurobiology of Stomotoca. II. Pacemakers and conduction pathways.

Evidence is presented for separate conduction pathways for swimming and for tentacle coordination in the marginal nerves of the jellyfish Stomotoca. The effector muscles are fired through junctions sensitive to excess Mg++, probably represented by the neuromuscular synapses observed by electron microscopy. The swimming effector (striated muscle) fires one-to-one with nerve input signals and myoid conduction occurs. Tentacle responses (smooth muscle contractions) involve facilitation, presumably at the neuro-effector junction; responses are graded and nonpropagating. Electrical correlates of two further conducting systems using the marginal nerves have been recorded. Their functions are unknown. One, the bridge system, extends up the four radii and encircles the peduncle; the other (ring system) is confined to the margin. A fifth conducting system is inferred in the case of the pointing response and its distribution is plotted. Signals have not been obtained from it. Pointing is accompanied by a burst of muscle potentials in the radial smooth muscles and is exhibited after a lengthy latency, indicating a local pacemaker. A sixth conducting pathway is the epithelial system, which mediates crumpling, a response involving the radial muscles without pacemaker intervention. Characteristic conduction velocities and wave forms are noted for the first four systems and for epithelial pulses. All systems, except perhaps the pointing conduction system, through-conduct under excess Mg++. Spontaneous activity patterns are described for the swimming, tentacle pulse, and ring systems. Abrupt increases in light intensity inhibit spontaneous activity, sudden decreases augmenting it. In the absence of specialized photoreceptors, light is presumed to act directly on central neurons. Epithelial pulses inhibit swimming, apparently by blocking the generation or conduction of the primary nervous events. This observation, taken in conjunction with evidence of feedback inhibition of the primary swimming system by the cells it fires, is discussed in relation to possible mechanisms whereby the output of nerve cells might be altered by activity in the excitable epithelial cells which envelop them.     

Proline-containing beta-turns. IV. Crystal and solution conformations of tert.-butyloxycarbonyl-L-prolyl-D-alanine and tert.-butyloxycarbonyl-L-prolyl-D-alanyl-L-alanine

The conformations of the dipeptide t-Boc-Pro-DAla-OH and the tripeptide t-Boc-Pro-DAla-Ala-OH have been determined in the crystalline state by X-ray diffraction and in solution by CD, n.m.r. and i.r. techniques. The unit cell of the dipeptide crystal contains two independent molecules connected by intermolecular hydrogen bonds. The urethane-proline peptide bond is in the cis orientation in both the molecular forms while the peptide bond between Pro and DAla is in the trans orientation. The single dipeptide molecule exhibits a "bent" structure which approximates to a partial beta-turn. The tripeptide adopts the 4----1 hydrogen-bonded type II beta-turn with all trans peptide bonds. In solution, the CD and i.r. data on the dipeptide indicate an ordered conformation with an intramolecular hydrogen bond. N.m.r. data indicate a significant proportion of the conformer with a trans orientation at the urethane-proline peptide bond. The temperature coefficient of the amide proton of this conformer in DMSO-d6 points to a 3----1 intramolecular hydrogen bond. Taken together, the data on the dipeptide in solution indicate the presence (in addition to the cis conformer) of a C7 conformation which is absent in the crystalline state. The spectral data on the tripeptide indicate the presence of the type II beta-turn in solution in addition to the nonhydrogen-bonded conformer with the cis peptide bond between the urethane and proline residues. The relevance of these data to studies on the substrate specificity of collagen prolylhydroxylase is pointed out.     

Preliminary evaluation of anti-inflammatory and anti-arthritic activity of S. lappa, A. speciosa and A. aspera.

Saussurea lappa, Argyreia speciosa and Achyranthes aspera are well known Indian medicinal plants used in the indigenous systems of medicine for the treatment of inflammatory conditions. The ethanolic extracts of the plants at the doses of 50, 100 and 200 mg/kg, p.o. were screened for their effect on acute and chronic inflammation induced in mice and rats. S. lappa and A. speciosa were found to significantly inhibit paw edema induced by carrageenan and Freund's complete adjuvant and to prevent accumulation of inflammatory cells in carrageenan-induced peritonitis at doses of 50-200 mg/kg. A. aspera inhibited these inflammatory responses at doses of 100-200 mg/kg. The studies reveal that the ethanolic extracts of S. lappa, A. speciosa and A. aspera possess anti-inflammatory and anti-arthritic activity and support the rationale behind the traditional use of these plants in inflammatory conditions.     

Ascaridoid nematodes of amphibians and reptiles: Gedoelstascaris n.g. and Ortleppascaris n.g.

Two new genera, Gedoelstascaris and Orleppascaris, are proposed for species of ascaridoid nematodes occurring in crocodilians and previously included in Dujardinascaris. Species included in Gedoelstascaris are vandenbrandeni Baylis, 1929 as type species and australiensis Baylis, 1931 (= salomonis Kreis, 1940). These species occur in Crocodylus spp. in Africa and Australia respectively and are characterised by lips with a rostral plate, without interlocking processes or dentigerous ridges, with well-developed interlabia, lobulated ventriculus, and excetory pore in front of the nerve ring. Species included in Ortleppascaris are: nigra Gedoelst, 1916 (= tasmani Ortlepp, 1932) as type species; alata Baylis, 1947: antipini Mozgovoy, 1950. These species occur in Crocodylus, Caiman and Alligator and are characterized by flat lips with alate margins, without anterior rostral plate, interlocking processes or dentigerous ridges, with weakly developed interlabia, by an irregular-shaped ventriculus, excretory pore behind or between the subventral lips, and by the presence of lateral alae or cuticular thickenings in the oesophageal region. The significance of this proposal is discussed in relation to the radiation and dispersal of ascaridoids of crocodilians.     

PAF-receptor. III. Conformational and electronic properties of PAF-like agonists and antagonists.

In order to compare electronic and conformational properties of PAF-agonists and PAF-antagonists, 14 analogues structurally related to PAF were studied. A common conformation of the glycerol backbone was present in all agonists and all constrained or flexible antagonists. The distinction between agonists and antagonists appears to be casted on position-2 where the folded conformation of the substituent for agonists should be the most probable. In position-3 the gauche conformation can be adopted by all the analysed compounds. The electrostatic potential well at -30 kcal/mol stretches to the carbonyl group in position-2 in the folded conformation of the agonists. On the contrary, in constrained antagonists, a second negative zone appears around the carbamate group. Given the modelling results, the triethylammonium PAF analogue considered in literature as a weak agonist, was resynthesized and proved to be more potent than previously reported. These experimental results confirm our hypothesis in terms of a common conformation of agonist and antagonist PAF-like molecules.     

Allosteric and non-allosteric phosphofructokinases from Lactobacilli. Purification and properties of phosphofructokinases from L. plantarum and L. acidophilus.

Phosphofructokinase (ATP : D-fructose-6-phosphate 1 phosphotransferase, EC 2.7.1.11) from two different lactobacilli, Lactobacillus plantarum and Lactobacillus acidophilus were isolated and purified. Both enzymes have a molecular weight of 154 000 and consist of four subunits of identical size. Antisera from sheep immunized against the purified phosphofructokinase from L. plantarum showed immunologic cross reaction with the enzyme from L. acidophilus. In spite of the close molecular relationship indicated by the immunologic cross reaction, the kinetic behaviour of the two enzymes was strikingly different. Phosphofructokinase from L. plantarum showed pure Michaelis-Menten behaviour. Phosphofructokinase from L. acidophilus, however, showed sigmoidal substrate saturation curves for fructose 6-phosphate in the presence of slightly alkaline pH and high ATP concentrations; it was activated by fructose 1,6-biphosphate and inhibited by ADP. The results indicate that even enzymes which are structurally very similar may differ greatly with respect to their kinetic and regulatory properties and suggest that allosteric and non-allosteric phosphofructokinases have the same origin in evolution.     

Senior house officers and their training. II. Perceptions of service and training.

Aspects of teaching and learning at senior house officer level in South East Thames region were investigated by analysis of the responses of consultants, senior registrars, registrars, and senior house officers to a postal questionnaire. Responses to sections about who teaches senior house officers, how senior house officers learn, and the relation between the service and training elements of these posts varied significantly, according to the status of the respondents; certain grades commonly overestimated their own contribution when compared with the estimates of the other grades. Although the replies of senior house officers showed that they were taught by various grades, 47% of this group did not regard the consultant as their main teacher. Senior registrars and registrars rather than consultants were regarded by senior house officers as best at teaching (63% v 48% respectively). Consultants and registrars were considered to require more commitment to training, personal educational training, and to be more approachable. Inquiry about teaching methods used most by senior house officers showed absence of a systematic approach to training. Only about half of senior house officers cited ward rounds with consultants. Views on the relation between training and service were significantly different among grades, but there was general dissatisfaction. Overall, the findings disclosed the ineffectiveness of senior house officer training posts. This arises from lack of a clear distinction between training and service elements, of educational training for teachers, of a clear contractual obligation to teach im the consultant grade, and of allotted time for training and study for the teachers and senior house officers respectively. Reversal of these current trends is needed for senior house officer posts to fulfil their main training function.     

Comparative Observation on Leaf Anatomy and Pollen of Vernicia Lour. and Aleurites J. R. et G. Forst.

The folial anatomy and pollen of one species of Aleurites and two species of Vernicia were studied. The former genus is characterized by the presence of echinolophate sculpture of pollen and a single outer stomatal ledge, curved cuticular ridges of peristomatal rim as well as large nodular ornamentation on the surface of epidermis beneath which there is no hypodermis. The latter one is characterized by the verruca-murate sculpture of pollen and the cuticular striate ornamentation on leaf surface of epidermis beneath which there is one layer of hypodermis, although they both have paracytic stomata and the Crotonic type of pollen. The genus Vernicia has not been accepted for a long time, but these micromorphological characters show as additional evidence that recent separation of the two genera by Airy Shaw (1966)^[6] is reasonable. Both genera possess very similar xeromorphic feature designated here as orbicular lustrous spot.