Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1962. / Vita. / Includes bibliographical references (leaves 155-162). / by Thomas Freud Wiener. / Sc.D.

In situ measurements of the fertilization success of broadcast spawning marine invertebrates have been conducted mainly on shallow subtidal echinoderm and coral species. In this study, field fertilization success was measured for two infaunal, intertidal polychaetes Arenicola marina and Nereis virens. Both species are epidemic spawners, with populations of A. marina spawning over a few days in autumn while N. virens spawns in early spring. The fertilization success of female Arenicola marina is highly variable, ranging from 0 to 100%, and is determined by male spawning density. It is hypothesised that fertilization success over the entire spawning period is the result of an accumulation of fertilizations each day in the spawning period. Fertilization success was measured indirectly in Nereis virens by transplanting oocytes into the field. At least two spawning periods occurred for the population studied here. Fertilization success was uniformly high during the first period, and in the second fertilization success was highest among those eggs located high in the water column as opposed to those at substratum level. The fertilization strategies of these polychaetes are discussed in the light of these results. Comparative laboratory experiments were performed on factors that affect fertilization success in Arenicola marina. Nereis virens, Asterias rubens and Echinus esculentus, including sperm:egg ratio, sperm-egg contact time and sperm concentration. The extent to which each of these factors affects fertilization success varies with species, and this is explained by gamete attributes and mathematical models. Gamete longevity significantly affects fertilization success, and eggs and sperm of Arenicola marina are extraordinarily long lived compared to those of the other species studied here and elsewhere. Eggs are viable for 5 days after spawning, while dilute sperm remains capable of fertilizing eggs for more than 48 hours. The laboratory data are discussed in terms of the fertilization strategies of each of the species.

1. The mechanisms underlying hindgut movements in the lobster, Homarus gammarus (Lo) have been studied. 2. The hindgut is innervated from the sixth abdominal ganglion (6A.G.) by the posterior intestinal nerves (P.I.N.'s). Stimulation of any of the connectives of the ventral nerve cord (V.N.C.) will elicit hindgut and anal movements. 3. The hindgut is divisible into anterior and posterior regions, whose basic co-ordination is undisturbed by sectioning the hindgut, so long as the nerves remain intact. 4. Numerous endogenous oscillators mediating spontaneous contractions are thought to lie within the muscles of the rectum. Oscillators within the radial muscles of the anus can be activated by nervous discharge. 5. Receptors responding to anal dilation and closure have been described both anatomically and physiologically. They lie in the anal nerves. No physiological evidence exists for the presence of receptors on the rectum. 6. Hindgut and anal movements may be initiated by either 'phasic' or 'tonic' motor neurones. Bursts of tonic discharge will cause powerful hindgut movements (the defaecatory response), whilst those elicited phasically are rather weaker. The form of the bursting discharge is, apparently, immutable and is unaffected by extirpation of all sensory input. 8. The structure of the 6A.G. has been determined. It is a highly complex ganglion and it is suggested that it was derived from three fused ganglia in the course of evolution. 9. The somata of neurones causing efferent discharge to the hindgut have been shown to lie in the anterior part of the posterior ventral cortical lobe of the 6A.G. 10. Some of these neurone somata have been penetrated using glass microelectrodes. Three categories of neurones, responsible for hindgut control at the level of tine 6A.G., are thought to exist phasic neurones, tonic neurones and driver neurons. 11. The neurones within the 6A.G. represent a final motor pathway to the hindgut. These neurones are thought to be under the ultimate control of a centre lying in the tritocerebral region of the brain. Several interneurones connect the two.

In six experiments event-related potentials (ERPs) were recorded while subjects performed modified recognition memory tests. All experiments consisted of an initial study phase in which subjects studied words which were presented in one of two contexts. In a subsequent test phase subjects discriminated between old and new items, and between old items which had been presented in one of the two contexts at study. The design of these experiments permitted a comparison of three critical classes of ERPs: those to words correctly judged new, and those to words correctly judged old which were either correctly or incorrectly assigned to study context. All six experiments revealed reliable differences between the ERPs to correctly identified old and new words. In experiments 3-6 the analyses of the differences between the ERPs to correctly identified old and new words revealed two topographically and temporally dissociable modulations. The first of these was maximal at parietal sites over the 500-900 msec time window, and was larger over the left hemisphere than over the right. The second modulation was more temporally extended, maximal at frontal scalp locations, and displayed a right-greater than-left hemisphere asymmetry. Both of these modulations were of greater magnitude for words which were correctly assigned to study context. These findings are consistent with the view that multiple neural systems contribute to memory for context. The experimental findings are discussed in relation to theories of the relationship between memory for prior occurrences, and memory for contextual details of those occurrences.

If d(M) denotes the rank of the Schur multiplicator of a finite group G, then a group is efficient if -def G = d(M). Efficient presentations of the simple groups PSL(2,p), p an odd prime > 3, were obtained by J.G. Sunday. This raised the question of whether or not all finite simple groups are efficient. In this thesis, we investigate the deficiency of the groups PSL(2,pn). J.A. Todd gave presentations for PSL(2,pn) which use large numbers of generators and relations. Starting with these, we obtain, at best, deficiency -1 presentations for PSL(2,2n) (= SL(2,2n)) and deficiency -6 presentations for PSL(2,pn), p an odd prime. If pn = -1(mod 4), the latter can be reduced to a deficiency -4 presentation. Efficient presentations for PSL(2,25), PSL(2,27) and PSL(2,49) are obtained. The Behr-Mennicke presentation for PSL(2,p) is one of the most fundamental in the sense that it forms the basis for others, such as those given by Sunday, Zassenhaus and Sidki. Behr and Mennicke derived their presentation indirectly, and it would be desirable to have a more direct proof. The groups G[sub]p(a) are defined as < U, R, S | U3 = (UR)2 = (US)2 = Sp = Rt = (SaRU)3= 1, Sa2R = RS > where a ε GF(p)* and a2t = 1 (mod p) . We show that G[sub]p (2) is isomorphic with the Behr-Mennicke presentation for PSL(2,p), p > 3. Conditions are found to discover when Gp (a) is isomorphic with PSL(2,p) and, under these conditions, this provides a direct proof of the Behr-Mennicke presentations. For any odd positive integer m, we show that the groups SL(2,Z (m)) and PSL(2,Z(m)) are efficient.

Fatty acids containing a furan ring system were recently discovered by North American Scientists in the liver and testicular lipids of northern pike. We developed an analytical procedure based on urea crystallization and argentation thin layer chromatography for the isolation of small quantities of these novel acids. Using this method a large number of fish lipids taken from both freshwater and marine habitats wore examined. Our results show the wide occurrence of furanoid acids in fish at a low level (up to 5%), These unusual acids tend to concentrate in the cholesterol esters and appear to be absent from the phospholipids. Contrary to claims by the North American researchers we do not find a significant relation between the occurrence of these acids and the sex of the species or on whether the lipid is derived from a freshwater or marine source. We consider rather that the nutritional status of the animal is more significant. Cod liver oil usually contains furanoid acids at about 1% level but in two starved cod the proportion of these acids rose dramatically to 34 and 48% respectively. We also examined four commercial fish meals but furanoid acids were not present in any of them. Furanoid fatty acids were found to accumulate in the adipose tissue of rats given cod liver oil. No furanoid acids were demonstrable in comparable samples from rats given synthetic 10,13-furan acid. A furanoid fatty acid has been isolated from Exocarpus cupressiformis seed oil. In two samples of this seed available to us we did not detect any furanoid acids but found 8-hydroxyoctadoc-trans-11-en-9-noic acid (5%).The methodology used in the isolation of furanoid acids also allowed the study of methyl-branched acids. Whilst confirming the wide distribution of three phytol-based acids in fish lipids we have also detected three other compounds which we believe are diunsaturated derivatives of 7,9-dimethylhexadecanoic, 7,9- and 9,11-dimethyloctadecanoic acids respectively. The opportunity was also taken to study the more common acids of some fish species not previously examined. Besides confirming the well-known differences between the lipids of freshwater and marine origin, we find a significant difference between the fatty acids of male and female fish of freshwater origin, with the female containing more n-3 polyene acids and less monoene acids than does the male. The n-3/n-6 ratio is the most significant feature distinguishing freshwater from marine fish lipids. The 10,13-, 9,12-, and 8,11-isomers of the C18 furanoid acids were prepared by one or more of the following methods. (i) Pd(II)-catalysed cyclodehydrogenation of oxygen-containing unsaturated acids, (ii) dehydration of diepoxides and dehydrogenation of epoxy alkenes with propyl iodide-sodium iodide-dimethylsulphoxide, and (iii) dehydration of endoperoxides. Synthesis of heterocyclic compounds by Pd(II)-promoted cyclization reactions is a fairly new development. The reactivity of various long-chain oxygenated esters with this unique reagent is discussed. The endoperoxide route is also novel and leads to speculation about the biosynthesis of natural furanoid acids. Recognition and identification of long-chain furanoid acids by their chromatographic and spectroscopic behaviour is discussed. Mass spectrometry is a powerful method of structure determination of these substances. Some chemical reactions of long-chain furanoid acids are also described.

Photoelectric scanner observations are combined with infrared photometry in the JHKL bands to give interstellar extinction curves by the colour difference method for 25 reddened stars in the Southern Milky Way. The observed stars are distributed from galactic longitude ℓ^II = 260°; through the Galactic Centre to ℓ^II = 30°. The scanner data ranges in wavelength from 3A80 to 5240 A with a resolution of 40 A in the second order of diffraction, and from 5080 to 8040 A with a resolution of 80 A in the first order. The infrared photometry extends the wavelength coverage to 3.5 µ. The normalized extinction curves show appreciable variations from star to star which are not apparently related to galactic structure. In several cases stars quite close together in the sky show appreciably different curves, suggesting that fluctuations in the grain size distribution may be occurring on a fairly localized scale. Using a graphite-iron-silicate grain model, extinction curves computed from the Mie theory are fitted to the observational data. This provides a theoretical basis for extrapolation of the curves to λ ⁻¹=0, allowing the ratio of total to selective extinction, R, to be deduced. R varies between 2.6 and 3.5 for 22 stars lying within 10° of the galactic plane, and between 3.8 and 4.3 for 3 stars in Upper Scorpius. One of the Upper Scorpius stars studied, HD 147889, lies in an HII region near the centre of the p Oph complex of dust and nebulosity, A variable extinction analysis applied to members of the Sco OB-2 association indicates an increase in the value of R for stars lying towards nebulosity in the complex; for these stars alone a result of R = 4.2 ± 0.5 is derived, whilst for the remainder, R = 3.3 ± 0.3. The distance modulus of the association is deduced to be 6.1 ± 0.1, which is in good agreement with the kinematical value. The scanner extinction curves contain considerable broadband structure. In particular, a depressed region between wavenumbers 1.6 and 1.97 µ⁻¹ is a common feature of the curves. A similar depression was noted by Whiteoak in the extinction curves of Northern Milky Way stars. Its depth correlates well with reddening, suggesting that the feature originates in the grains. The extinction curve of HD 147889 shows a -1 cusp-like depression at 1.97 µ⁻¹ which divides the curve into two distinct sections. The ratio of the 4430 A diffuse interstellar band height to colour excess shows signs of systematic variation with longitude for stars whose reddening occurs mainly in the local spiral arm.

Treatment of waste water by freshwater microalgae is rapidly becoming a popular sewage treatment practice throughout the world, but only a few studies have been made into the use of marine strains or of their potential for heavy metal removal. This study examines the heavy metal tolerance of a range of marine microalgal species and examines some of the biological processes involved in metal uptake. Initially over 350 marine microalgal species/isolates were screened for (a) growth in the presence of heavy metals (10 ppm), (b) growth in the presence of wastewater (1:1 sewage : seawater), and (c) heavy metal uptake. Of the microalgae examined, only one isolate, Tetraselmis sp. (TSAW92) was found to satisfy all of the screening conditions. Metal uptake was found to be a biphasic process, with an initial rapid saturable metabolism-independent stage followed by a slower nonsaturable metabolism-dependent stage. Using a novel filtration technique metal uptake was measured at ten second intervals. The results show that most of the metal uptake occurs within one minute after exposure. The second stage of metal uptake was found to be associated with the extracellular release of up to three copper binding proteins of ca. 28, 30, 55 kDa. Protein release was specifically induced by the presence of heavy metals and was not due to metal mediated increases in cell membrane permeability. Two practical applications of Tetraselmis sp. (TSAW92) metal uptake were investigated. First dried biomass was evaluated in a simple packed column. Second, live cells were grown on a wastewater treatment raceway (2m), upstream of a Dunaliella salina stocked nutrient removal raceway. Dried Tetraselmis sp. (TSAW92) was capable of removing copper from a 1:1 seawater : sewage solution to a final loading of 30% at an efficiency of approaching 100%. Over four weeks live TSAW92 removed 100% of the applied copper to a final loading of 37%, and, after the second stage, the raceway was found to remove 95% of the applied nitrogen and 87% of the applied phosphorus. This thesis shows that marine microalgae are capable of removing heavy metals from wastewater in vitro, on raceways, and as dried biomass. Live marine microalgae on raceways were further found to remove inorganic nutrients (nitrogen and phosphorous). In addition work is presented which suggests that copper uptake by the marine chlorophyte Tetraselmis sp. (TSAW92) is mediated through extracellular copper binding proteins.

No description available.

In this thesis, the structures and selected properties of TPA-like tumour promoters and of Myo-inositol polyphosphates are calculated and compared with their promoting and calcium releasing activities respectively. Three different levels of theory are used in the calculations, namely ab initio, semi empirical and molecular mechanics, though the majority of the calculations are performed using the MNDO derived semi-empirical methods implemented in MOPAC. A detailed description of the phorbol ester / DAG binding site is obtained from the structure / activity relationships derived for the tumour promoters and molecular dynamics simulations of the phorbol ester, TPA, in a lipid bilayer is carried out to investigate the position of the binding groups in relation to the surface of the bilayer. In order to carry out this simulation, a method (HYDRO) has been developed to produce close packed heterogeneous bilayers in which the headgroups of the components lie in random orientations. Thus the simulations are more realistic than calculations in which the lipids are placed in a regular array and interstitial spaces due to the difference in surface area of the bilayer components are kept to a minimum. The effects of the number and position of phosphate groups on the ring conformations of myo -inositol phosphates and the connection between this and calcium releasing activity are studied in chapter 5. As the molecules are particularly flexible with a large number of potential local minima, phosphate groups have been added sequentially to keep the required number of starting points as low as possible and rotation of phosphate hydroxyls has been ignored. The heats of formation, calculated with the different semi-empirical parametrisations, differ considerably, so the final calculations chapter compares energies and selected properties calculated for model organics phosphates using different methods and theory. The results using the new parametrisation, PM3, are compared with those of the earlier AMI for both the phorbol systems and the inositol phosphates to test its suitability.