Showing papers by "Memorial University of Newfoundland published in 1973"

Comparative light and electron microscopic study of retinal histogenesis in normal and rd mutant mice.

Abstract: Mice, homozygous for the mutant gene rd show selective degeneration of the photoreceptor cells after their initial differentiation. Phenotypic expression in the mutant and in normal mice was studied by light and electron microscopy. The sequential emergence of developmental deviations in the mutant retina falls into three categories. First, predegenerative differences are manifest within the photoreceptor cells during 4–8 days after birth in retarded growth of the inner segments, reduced outer segment production, delayed development of the outer plexiform layer and slower segregation of the perikarya. Next, degenerative changes are recognized from 6 day onwards with swelling and vacuolization of the Golgi cisternae in the inner segments followed by cytolytic alterations affecting the ultrastructure of the entire cell. Lastly, with increasing loss of photoreceptor cells post-degenerative effects are seen in deepening of the basal infoldings and microvilli of the pigment epithelium and increase of Muller's fibres. The progress of degeneration in the mutant retina corresponds to the phase of rapid growth of the Golgi apparatus and rod outer segments in the normal retina. The role of the Golgi apparatus in the differentiation of the photoreceptor cells and its relation to the expression of the rd gene are discussed.

Movement time in an underwater environment.

Abstract: The effect of an underwater environment on the human motor capacity, as measured by Fitts’ Law, was determined. Five Ss performed a reciprocal tapping task both on land and underwater. The results showed that movement time (MT) was significantly slower (p < 01) underwater than on land. Underwater the amplitude of the movement was found to have a greater influence on MT than the required precision of the movement. On land the reverse was found to be true with movement precision having a greater influence on MT.

The Earth's rotation

Abstract: The most ancient and fundamental concern of astronomy is the orientation and motion of a terrestrial observer relative to the stars. Its geophysical aspects date from the time of Newton and Halley, and its mathematical foundations were laid by Euler 200 years ago. Despite this honorable antiquity, the subject is far from moribund and today presents a rich and fascinating array of challenges to observation, experiment, data analysis, and theory. The many-faceted problems of the three-dimensional rotation of the earth about its center of mass now attract astronomers and paleontologists, solid earth geophysicists and electrical engineers, general relativists and oceanographers, and applied mathematicians and scholars of classical texts.

Radial Distribution Function of Liquid Sodium

Abstract: The radial distribution function and static structure factor of liquid sodium at temperatures of 100 and 200\ifmmode^\circ\else\textdegree\fi{}C have been calculated by a Monte Carlo method using a realistic ion-ion potential. The calculated structure factor is in excellent agreement with recent x-ray-diffraction measurements.

Saccharin aversions induced by lithium chloride toxicosis in a backward conditioning paradigm

Abstract: Seven experimental groups of seven rats each were allowed to consume saccharin solution at different times relative to intubation of lithium chloride solution. Six backward conditioning (BWDj groups were intubed 0.5, 1,2,3,4, and 8 h before saccharin consumption, and a forward conditioning (FWD) group was intubed 0.5 h after saccharin consumption. A no-lithium control group of 14 rats received no intubation. Only the 0.5-h FWD and the 0.5-h BWD groups showed an aversion to saccharin relative to the no-lithium controls. The aversion to saccharin in the 0.5-h FWD group was more pronounced than that in the 0.5-h BWD group. This shows that the aversive effects of lithium toxicosis dissipate far sooner than the aversive effects of X-irradiation. If ingestion of a flavored substance, such as saccharin solution, is followed by toxicosis induced by some independent means, such as X-irradiation, rats will avoid the flavored substance on subsequent occasions (Revusky & Garcia, 1970). With saccharin. this is true even if the interval between ingestion and exposure is extended up to 12 h (Smith & Roll, 1967). Furthermore, it has been shown that rats will form an aversion to saccharin solution when the solution is consumed up to 12 h after exposure to radiation ceases (Scarborough, Whaley, & Rogers, 1964). It was initially suspected that the reduced preference was due to unlearned factors (Mel.aurin, 1964), or to backward conditioning, which is generally considered impossible (Kimble, 1961). A better explanation is that the aversive physiological aftereffects of the radiation continue long after exposure ceases (Scarborough et aI, 1964; Smith, Taylor, Morris, & Hendricks, 1965; Revusky & Garcia. 1970). Thus, although the operational paradigm may involve backward conditioning, consumption of the saccharin solution may well precede the peak of the sickness. Lithium chloride is the most effective known chemical toxicosis for producing flavor aversions in animals (Nachman & Ashe, in press). Nachman (1970) has shown that forward conditioning can take place when the interval between saccharin consumption and lithium toxicosis is up to at least 4 h. However. the backward conditioning curve for lithium has not been investigated. The best guess is that the backward curve for lithium would be much shorter than that for X-irradiation. In radiation sickness with humans, the prodromal symptoms of nausea and vomiting do not become pronounced until approximately 7 h after radiation (Gerstner, 1960). According to reports of investigators who themselves consumed lithium, lithium

Amphibolite Associated with Newfoundland Ophiolite: Its Classification and Tectonic Significance

Abstract: Amphibolite is invariably associated with ophiolites, forming an integral part of them. Studies of Newfoundland ophiolites and island-arc assemblages provide a genetic framework based on plate tectonics in which the amphiolites can be classified.

Intense Vibrational Absorption Spectra of Trapped Triatomic Radicals

Abstract: Intense spectra of triatomic radicals have been produced by means of a surface reaction of hydrogen atoms, formed by a microwave discharge in flowing gas, with diatomic oxides. Failure of this method to produce detectable formyl radicals is attributed to existence of an activation energy greatly exceeding 200 cm−1 for reaction of H with CO. New NH and ND fundamental vibrations of HNO and DNO, at 2,719 and 2,043 cm−1, are now consistent with the known large bond length. The weak absorption due to the bending mode of DO2 has at last been located at 1,085.3 cm−1, enabling a vibrational assignment for hydroperoxyl radical to be completed.

The gastric mucosal response to acetylsalicylic acid in the ferret. An ultrastructural study.

Abstract: An electron microscopic investigation was undertaken on adult fasted ferrets in order to clarify the acute gastric mucosal, morphologic response to orally ingested acetylsalicylic acid. A single, clinically relevant dose (10 mg/kg) was administered and gastric surface responses were studied by scanning electron microscopy, and differential early, cytologic responses of the glandular cells were evaluated by transmission electron microscopy. Gastric bleeding was derived from minute, surface erosions morphologically indistinct from stress-type erosions. Parietal cells underwent drug-specific changes and chief cells, nonspecific degenerative changes. Mucous epithelial cells were disrupted only in localized regions, and tight junctions between surface epithelial cells remained intact. The order of decreasing cellular sensitivity to this acute (10–45 min) exposure to HCl-acidified aspirin solution was: parietal cells, chief cells, and surface epithelial cells. Argentaffin cells and mucous neck cells were resistant.

Parasitoid wasps as flower visitors in the Canadian High Arctic

Abstract: Collections and observations were made in 1963 and 1967 on insects visiting flowers at Hazen Camp and Gilman Camp on Ellesmere Jsland, N. W. T. Canada. The results giving the species of parasitoid Hymenoptera, the flowers visited, and their activity, are shown in this paper (Table 1).

The effects of scopolamine on fixed-interval behaviour in the rat: a rate-dependency effect.

Abstract: Eight rats trained on a fixed-interval of 2 min for food reinforcement were injected with scopolamine hydrobromide at 3.2 mg/kg on a number of sessions. On this schedule the animal normally pauses after reinforcement, then response rates increase as the interval progresses until responding reaches a high stable rate. The drug altered the normal patterning by producing a fairly stable response rate throughout each interval. An analysis of base rate change showed that the drug increased responding that was normaly slow early in each interval and decreased high rates of responding normally seen near the end of each interval. This demonstrated that scopolamine has a rate dependent effect similar to amphetamine and other drugs.

Possible Cryptic Suture in South-west Newfoundland

Abstract: THE concept of an important fault, the Cabot Fault, cutting across western Newfoundland was proposed by Wilson1 who interpreted it as a great sinistral fault and correlated it with the Great Glen Fault system in Scotland. There is, however, a second large fault in south-west Newfoundland, the Cape Ray Fault, the importance of which has previously been unrecognized. This fault separates two entirely different pre-Ordovician gneissic terrains which, when traced north-eastwards from Port aux Basques (Fig. 1) form the eastern and western margins of the Newfoundland Central Mobile Belt. This belt contains Lower Ordovician rocks in its central part which are interpreted as remnants of an old ocean floor, the proto-Atlantic1–5. The Cape Ray Fault thus effectively cuts out this ocean toward the south and juxtaposes its eastern and western margins. It may therefore represent a cryptic suture along which complete closure of the proto-Atlantic took place.

Lushs Bight and Roberts Arm Groups of Central Newfoundland: Possible Juxtaposed Oceanic and Island-Arc Volcanic Suites

Abstract: The Lushs Bight Group in the Pilleys Island area of central Newfoundland consists of basaltic pyroclastic rocks, pillow lavas, and sheeted diabase dikes, cut by plugs of gabbro and quartz diorite which have produced local amphibolitization. The Lushs Bight rocks are commonly gently folded but locally strongly schistose along shear belts and fault zones and around the intrusive bodies. The sheeted diabase has been metamorphosed to the upper greenschist (actinolite) facies, while in the flows, chlorite is dominant over actinolite, indicating a lower grade of metamorphism. The Roberts Arm Group consists of basaltic pillow lava locally overlain by dacite representing volcanic centers. This group has a strong bimodal chemistry; it differs from the Lushs Bight Group in the presence of dacite, in a lack of actinolite-grade metamorphism, and in that the basalt of the Roberts Arm Group is richer in K 2 O, Na 2 O, TiO 2 , Ba, Rb, and Zr, and poorer in CaO. These data are taken as evidence that the Roberts Arm volcanic rocks possibly represent an island-arc suite which was deposited upon oceanic crust now represented by the Lushs Bight Group.

Ferromagnetic behaviour of interacting superparamagnetic particle aggregates in basaltic rocks

Abstract: Studies on two rare cases of magnetic behaviour in basaltic rocks are reported. In both the cases a peak in susceptibility occurs at −160°C. However, one sample shows only normal hysteresis loops at low temperatures in a wide range of fields, while the other sample shows a constricted hysteresis loop in 1000 Oe at −190°C. Both types of behaviour can occur as a result of differing states of aggregation of interacting superparamagnetic particles in the respective samples.

Observations on the life‐history of bryopsis hypnoides lamour. from newfoundland: a new variation in culture1,2

Abstract: SUMMARY At its northernmost distributional limit in northeastern America, in Newfoundland, Bryopsis hypnoides Lamour. appears to have a heteromorphic, monophasic life-history. Zygotes resulting from fusion of anisogametes develop in culture into prostrate filamentous germlings, these also reproducing sexually by anisogametes to form a new generation of the prostrate type. Erect Bryopsis later grew from the prostrate phase: asexual stephanokontic zooids were entirely absent. The life-history in Newfoundland compares in part with that for B. hypnoides from northern parts of its European range; the presence of sexual reproduction in the prostrate phase in Newfoundland, however, is unique in Bryopsis and is not apparently a temperature dependent phenomenon. In the field Newfoundland B. hypnoides reaches sexual maturity in winter at temperatures less than 0°C. Germling phases studied in culture could not be located in the field. The question is raised as to the possible genetic isolation of Newfoundland B. hypnoides from populations in Europe.

Environmental impact of insect control by microorganisms.

Abstract: Most of the data concerning this topic are still to be collected. To address oneself to this subject now is thus comparable with, for example, attempting to review the environmental impact of insect control by synthetic organic chemicals two decades ago. The modern era dawned for both biological and chemical insect control near the beginning of World War 11. At that time, milky disease was registering microbial control’s first real success, the target organism being the Japanese beetle in the eastern United States.’ Also, at a point in history when food production had never been more important, DDT was scoring the first of its spectacular successes by saving Switzerland’s potato crop from the Colorado beetle.3 There we have, right at the outset, the two chief actors in our environmental drama: the chemical, linked with the powers of darkness (man-made), and the biological, representing the powers of light (from nature). Bacillus popilliae and DDT do share certain attributes. Modern technology makes both available in sufficient amounts and at a price that permits practical use; both are environmentally persistent and were first utilized under crisis conditions without an adequate amount of information concerning their potential impact upon nontarget organisms. Had they not been so used, both might still be waiting on the shelf. We still do not possess full information about the consequences of using either. Nevertheless, subsequent events have not shaken earlier confidence in the strict host specificity of B. popilliae (although exacting safety tests are now being contemplated in the United States?). The broad spectrum of effectiveness of DDT has been convincingly demonstrated and so has the fundamental importance to control of these two issues-resistance by target economic pests and disease vectors and hazard to nontarget species. Concerning the first issue, for example, seven years ago housefly resistance to Bacillus thuringiensis exotoxin was noted.4 With respect to environmental hazard, there has never been a weapon that lacked the capacity to harm innocent victims-usually when employed rashly, though sometimcs when used with the greatest discrimination. Thus, considering the above and the thesis that the key to control efficacy and selectivity is not the individual agent but rather the overall methodology, we must not lightly discard any weapon from our arsenal. My subject is the safety of “microbial pesticides,” as related to environmental quality. Ignoffo5 concentrated upon man as the nontarget organism of primary concern. Obviously man is the nontarget organism of ultimate primary concern. He fires the rifle and casts the rod to destroy for pleasure those game animals reserved for this purpose by conservationists; and he alone is capable of manifesting more than ephemeral concern for, or appreciation of the beauty of, any of those co-occupants of the earth’s ecosystems defended by environmentalists. What we know of the environmental impact of insect control by microorganisms is almost all related to economic entomology. It concerns apparently obli-