Showing papers by "Dalhousie University published in 1970"
TL;DR: A continuing study of the physiological controls of growth and development as part of a general investigation on productivity of marine zooplankton.
Abstract: It has been argued (McLaren, 1963, 1965) that reproduction and development of copepods may be physiologically (rather than trophically) determined when food is sufficiently abundant: thus, under these conditions the rates of development and egg production, and the total number of eggs laid by a female in her lifetime vary only with the physical factors of the environment such as temperature, salinity and pressure, temperature being by far the most important. This paper is part of a continuing study of the physiological controls of growth and development as part of a general investigation on productivity of marine zooplankton.
142 citations
TL;DR: In this article, the authors propose a method to solve the problem of the problem: this article...,.. ].. ).. ]... )...
Abstract: CONTENTS
138 citations
TL;DR: In this paper, the authors analyzed samples from 50 stations in the North Atlantic for particulate organic carbon and found that organic matter comprises about one third of the total mass of suspended matter.
96 citations
TL;DR: A spectral analysis technique for locating the site of an epileptic focus in the cat brain with the use of multielectrode data, obtained during a generalized seizure, is described.
Abstract: A spectral analysis technique for locating the site of an epileptic focus in the cat brain with the use of multielectrode data, obtained during a generalized seizure, is described. The data, indicating widespread appearance of epileptic activity, does not lend itself to conclusive analysis by conventional means. Three channels of data are examined at a time. One channel is said to drive the other channels if the first channel explains or accounts for the linear relation between the other two over a frequency interval corresponding to the interval of greatest energy concentration. The method of analysis involves computation of the coherence and partial coherence between data from all electrode pairs.
89 citations
TL;DR: In this article, organic particles greater than 5 μ from 38 North Atlantic stations were examined using phase microscopy and four morphological categories were evident: aggregates, flakes, fragments and unclassifiable particles.
86 citations
TL;DR: Cells of Leptomonas collosoma showed, without exception, a clockwise spiral as the tubules approached the posterior apex, and both the direction of spiraling and the manner of spreading were consistent.
Abstract: SYNOPSIS. Flagellates of 7 species from 5 genera of the family Trypanosomatidae were prepared for electron microscopy using a combination of surface tension spreading on a simplified Langmuir trough followed by critical point drying. These technics opened the cells and showed the microtubular complex in its 3-dimensional configuration or in a flat sheet with the inside surface facing-up.
Tears originated near the flagellar end and proceeded in a posterior direction usually paralleling the tubules. Major differences in the spreading pattern were species-specific. A connection between the flagellum and microtubules was not shown but strongly indicated by their constant association in all degrees of spreading. Most microtubules follow a spiral course from the flagellar end toward the posterior apical area and terminate short of the apex. It is suggested that the concept of antero-posterior orientation in the genus Trypanosoma be reconsidered.
Cells of Leptomonas collosoma showed, without exception, a clockwise spiral as the tubules approached the posterior apex. Therefore, both the direction of spiraling and the manner of spreading were consistent.
The number of microtubules varied among cells of the same species as well as on different levels of the same cell. Highest counts coincided with the level of greatest circumference. No connections or anastomoses between tubules were found. The microtubules are believed to have limited flexibility. Changes in diameter were interpreted to mean flattening had occurred. An intertubular substance, believed to surround the microtubules in the living cell, was present in all species.
83 citations
TL;DR: This study involved comparison of three techniques for increasing range of motion, and IA-CA, a modified version of proprioceptive neuromuscular facilitation (PNF) was compared using 24 normal male Ss.
Abstract: This study involved comparison of three techniques for increasing range of motion. Fast stretch (ballistic), slow stretch, and IA-CA, a modified version of proprioceptive neuromuscular facilitation (PNF) were compared using 24 normal male Ss. Controlling for serial order effects, 6 groups of 4 Ss each were administered the treatments, and the differences between pre- and post-exercise measures were observed. Multiple regression analysis indicated the superiority of the IA-CA approach.
77 citations
TL;DR: Although congenital cytomegalovirus infection in more than one sibling may be rare, the possibility of its occurrence should not be overlooked; infants born to the mother of a previously affected child should be subjected to long-term follow-up.
76 citations
TL;DR: The volcanic layer may be only 200 m thick at 45° N and oxidation of titanomagnetite may be responsible for the decrease in amplitude of the magnetic anomalies away from the ridge axis as discussed by the authors.
Abstract: The volcanic layer may be only 200 m thick at 45° N and oxidation of titanomagnetite may be responsible for the decrease in amplitude of the magnetic anomalies away from the ridge axis.
72 citations
TL;DR: The disinhibition phenomenon was found to be highly general, occurring under almost all test conditions, and could be produced during extinction only when the level of responding lay within a critical low range of values.
72 citations
TL;DR: The research extends the techniques used by Herrnstein and Loveland (1964), and confirms their finding that pigeons can master the concept of "person-present" in a visual display.
Abstract: Pigeons were trained to discriminate the presence of one or more human forms in displays projected on a panel above the response key. This task was mastered, although imperfectly, with successive and with simultaneous presentations of positive and negative instances. The course of acquisition of the discrimination was similar for the two training procedures. Animals were able to transfer the discrimination from the successive to the simultaneous situation. Various tests were carried out to control for artifactual cues on which the discrimination might have been based. The discrimination was maintained when new displays were presented, when reinforcement was omitted, and when displays were inverted 180°. Animals were also able to discriminate between pairs of displays that were identical, except that one member of the pair contained a human form. The research extends the techniques used by Herrnstein and Loveland (1964), and confirms their finding that pigeons can master the concept of “person-present” in a visual display.
TL;DR: Fötale menschliche Fibroblasten wurden in einem109Cd und65Zn enthaltenden Kultur medium gezÜchtet, der Zellsaft wurde in allen Zellen kontinuierlich absorbiert.
Abstract: Fotale menschliche Fibroblasten wurden in einem109Cd und65Zn enthaltenden Kultur medium gezUchtet109Cd wurde in allen Zellen kontinuierlich absorbiert Mit Gel-Filtration wurde der Zellsaft in 2 Komponenten aufgetrennt, die beide109Cd enthielten ahnliche,109Cd bindende Komponenten wurden auch in Rattenleber-Homogenaten gefunden
TL;DR: The trimethylsilyl derivatives of the anions SiO44−, Si2O76− and Si3O96− were resolved below 290° on SE-30 (methylpolysiloxane) liquid phase using a temperature-programmed operation and were identified by high-resolution mass spectrometry as discussed by the authors.
TL;DR: Long's citation of Bader's conclusions as a criticism of my weighting procedure appears to depend tacitly on an assumption fairly widely made by biologists: that the coefficient of variation is the only meaningful way to measure variability in organisms.
Abstract: sions do not bear directly on the truth or falsity of my hypothesis concerning the relationship between conservatism and variation Long's citation of Bader's conclusions as a criticism of my weighting procedure appears to depend tacitly on an assumption fairly widely made by biologists: that the coefficient of variation is the only meaningful way to measure variability in organisms Since we know what selection operates ultimately on genetic variances and not on genetic coefficients of variation and since we are now faced with the case of a data set in which different ways of measuring "variability" lead to different and seemingly paradoxical conclusions, it would seem the coefficient of variation should be used somewhat more cautiously in biological investigations LITERATURE CITED
TL;DR: The retina of nudibranch eyes contains two types of large cells; pigment cells which comprise about two-thirds of the total, with unpigmented sensory cells making up the remainder.
Abstract: The retina of nudibranch eyes contains two types of large cells; pigment cells which comprise about two-thirds of the total, with unpigmented sensory cells making up the remainder. Both pigment and receptor cells carry microvilli on their distal borders, but no traces of cilia were observed among them. The cornea of the eyes of aeolid and dendronotid nudibranchs is composed of a single layer of small cells, unlike the dorids where the cornea is made up of one of more large cells. The latter contain nuclei comparable in size with those of the pigment cells in the retina, but are themselves unpigmented.
TL;DR: It is interesting that the only overtly malignant “retinal anlage” tumors as yet published, arose in the female genital organs, and the location of the tumor suggests teratoid origin.
Abstract: An unusual malignant melanogenic tumor of the ovary is reported. Although our tumor bears close histologic resemblance to the so‐called retinal anlage tumor, it differs from it radically in biological behavior. To our knowledge, a tumor like ours has never been reported to occur in the ovary, although two somewhat similar tumors have been described in the corpus uteri. It is also interesting that the only overtly malignant “retinal anlage” tumors as yet published, arose in the female genital organs. The location of our tumor suggests teratoid origin.
TL;DR: Examination of the products of conception showed a normal fetus and placenta, but the fetal membranes presented foci of chorioamnionitis in which hyphae and spores suggestive of Candida could be demonstrated.
TL;DR: A case of a rare congenital malformation, duplication of the rectum, has been presented and various theories of etiology considered and the pathology, clinical features and treatment discussed.
Abstract: A case of a rare congenital malformation, duplication of the rectum, has been presented. The literature has been reviewed, various theories of etiology considered and the pathology, clinical features and treatment discussed.
TL;DR: A progressive increase in the ratio of cholesterol ester to free cholesterol was observed in the degenerating nerve in hen sciatic nerve at 8, 16 and 32 days after nerve section, and hydrolytic cholesterol esters activity decreased progressively inThe degenerating nerves at the same time.
Abstract: —
To study the involvement of cholesterol esters in myelination and demyelination, we determined the concentration of free cholesterol and cholesterol esters and the activity of hydrolytic cholesterol esterase (sterol ester hydrolase; EC 3.1.1.13) in hen sciatic nerve during Wallerian degeneration. A progressive increase in the ratio of cholesterol ester to free cholesterol was observed in the degenerating nerve at 8, 16 and 32 days after nerve section. Hydrolytic cholesterol esterase activity decreased progressively in the degenerating nerves at the same time.
In addition we measured the ratio of RNA to DNA, and the activity of the NADP+-dependent isocitrate dehydrogenase [L8-isocitrate: NADP oxidoreductase (decarboxylating); EC 1.1.1.42] at 8, 16 and 32 days after nerve section. The RNA to DNA ratios decreased progressively in the degenerating nerves. NADP+-dependent isocitrate dehydrogenase increased in activity after nerve section, reaching a peak at 16 days.
TL;DR: Generalization gradients obtained on the dimension of speed indicated a broad range of movement detection and suggested formation of a "movement concept" in pigeons.
Abstract: Pigeons were trained to discriminate between the presence and absence of apparent movement in visual displays. Generalization gradients obtained on the dimension of speed indicated a broad range of movement detection. Extremely accurate discrimination performance on displays varying in direction of movement suggested formation of a "movement concept".
TL;DR: A spectrophotometric method for the quantitative determination of isonicotinic acid hydrazide (INH) in whole blood is described and Streptomycin and known metabolites of INH do not react, but p -amino-salicylic acid should be absent.
TL;DR: A wide choice of spray reagents is given and the uses of this method for many other systems, including selenium-containing compounds, is suggested.
TL;DR: In this article, the effect of the reduced $s$-wave character on the virtual-bound-state (resonance) model of the Heusler alloys has been investigated.
Abstract: The effective magnetic fields at all non-Mn sites, the nuclear-hyperfine contributions to the specific heat, and the paramagnetic Curie temperatures have been calculated for the Heusler alloys ${\mathrm{Cu}}_{2}$MnAl, ${\mathrm{Cu}}_{2}$MnIn, and ${\mathrm{Cu}}_{2}$MnSn, by an extension of the virtual-bound-state (resonance) model previously used by Caroli and Blandin. The required electronic $\ensuremath{\xi}$ factors are determined from paramagnetic-susceptibility and Knight-shift data on dilute Cu-base binary alloys; and a phenomenological procedure is used to estimate the reduction in $\ensuremath{\xi}$ factors appropriate for the corresponding ions in the Heusler alloys. The latter effect is important, and failure to take the reduced $s$-wave character into account yields hyperfine fields which are too large by a factor of 2-4 for the polyvalent ions. Our predictions for those saturation hyperfine fields which have not yet been determined are -355\ifmmode\pm\else\textpm\fi{}45 KOe for In in ${\mathrm{Cu}}_{2}$MnIn, and -280\ifmmode\pm\else\textpm\fi{}45 and -260\ifmmode\pm\else\textpm\fi{}100 kOe for Cu and Sn, respectively, in ${\mathrm{Cu}}_{2}$MnSn. The nuclear-hyperfine contribution to the specific heat of ${\mathrm{Cu}}_{2}$MnIn is predicted to be $\frac{(5.94\ifmmode\pm\else\textpm\fi{}1.11 \mathrm{mJ}\ifmmode^\circ\else\textdegree\fi{}\mathrm{K}{\mathrm{mole}}^{\ensuremath{-}1})}{{T}^{2}}$. We give a critical and comprehensive comparison of theoretical results and available experimental data.
TL;DR: In the flagellum of the antennae of the German cockroach, Blattella germanica (L.), new annuli are formed lie fore each molt within the meriston and by division within the next several annuli distal to the Meriston (meristal annuli).
Abstract: In the flagellum of the antennae of the German cockroach, Blattella germanica (L.), new annuli are formed lie fore each molt within the meriston (3rd segment) and by division within the next several annuli distal to the meriston (meristal annuli). Doublets produced by division of meristal annuli do not themselves divide nor do the 17 or 18 terminal annuli (singletons) of the 1st instar. The latter are gradually lost during nymphal development. The overall result is that a 1st-instar flagellum having 24 or 25 annuli may become an adult flagellum having as many as 95 annuli.
Meristal annuli range from 4 to 12. The mode changes during development, being least in the 2nd instar (6) and greatest (9) in 4th, 5th, and 6th instars.
Only in the 1st instar do the annuli distal to the meriston increase gradually in length without discontinuities.
In all subsequent instars there are more or less obvious points in the flagellum at which the progression in length of annulus changes. These saltation points occur between groups of annuli; i.e., between the meristal annuli and the adjacent doublet group, between adjacent doublet groups, and between the distal doublet group and the group of singletons. These discontinuities make it possible to determine the instar of flagella that have singletons. The 2 annuli comprising a doublet are conspicuously unequal in length when first formed. In subsequent instars the difference in length diminishes and may undetectable when the doublet group of the 2nd instar reaches the 6th instar.
The growth in length of the flagellum as a whole like that of other hard parts of insects, increasing about 1.3 times at each molt. But within the flagellum the growth ratio ranges from about 4.0 in the meriston 1.0 at the apex, declining continuously from base apex, not only between groups of annuli but within groups. The observations summarized above apply to both sexes.