Empty Areas Research Articles

Sexual experience, androgens and female choice of a mate in laboratory rats.

Sexual experience produces long-lasting changes in both the behaviour and reproductive system of a male rat. The response of the female rat to an area that had recently housed a previously mated male was investigated in three experiments. In experiments 1 and 2 females preferentially urine marked in an area vacated by a sexually experienced (SE) male relative to areas vacated by a sexually inexperienced (SI) or castrated (C) male. The density of female marks were ranked SE greater than SI greater than C greater than empty area. In experiment 3 female preference of an SE male with varied and multiple mating experiences was magnified when compared with an SI male. There was the suggestion that the multiple SE male was even preferred to a male with only a single mating experience. A fourth experiment demonstrated an acute increase in circulating testosterone in multiple SE males exposed to oestrous or non-oestrous females, and the increase was observable for up to 7 days after exposure to an oestrous female. The conclusion is that chronic changes in androgen-dependent urinary by-products released by the SE male mediate the discrimination and choice of a mate by the female rat.

Effect of cannabis (hashish) on mitosis of Allium cepa L. root tips. II. Dissolution of the chromatic material in the interphase nuclei of Allium cepa cells after long exposure times with cannabis (hashish).

Cannabis causes the dissolution of the chromatin substances of Allium cepa cells. We were able, in this present investigation, to pursue the process of chromatin dissolution by applying cannabis for long exposure periods. Exposure to cannabis for a long treatment time dissolved the chromatin material within the nuclei, leaving only the nuclear membrane bounding an empty area. It seems that the process of dissolution of the chromatin substance is irreversible.Micronuclei can be induced in long exposure time with cannabis. Micronuclei can be considered as a test of chromosomal damage. But in short exposure treatment cannabis has not the ability to affect the chromosome structure.As far as the nuclear membrane is concerned, there does not seem to be any difference between normal and treated cells. The only unusual feature which is frequently found is deep invaginations of the membrane into the nucleoplasm. These infoldings are responsible for the irregular outline of many nuclei observed in root tips treated with cannabis.

Ultrastructural changes in the rat metrial gland in the latter half of pregnancy

The ultrastructural changes occurring in the metrial gland in the latter half of pregnancy in the rat have been studied. Typical palely stained granulated cells are present in the metrial gland up to day 20 but many granulated cells show variations in appearance which may be associated with degeneration. In some the cytoplasm is more darkly stained and such cells often have apparently empty areas of cytoplasm adjacent to the granules. From day 14 onwards many areas of the gland show cellular debris, apparently resulting from lysis of the granulated cells. However, occasionally normal granulated cells are present in blood vessels and have been observed apparently penetrating the vascular endothelium. A variety of changes was also noted in the stromal cell population. Inclusions became apparent in many of these cells; some of these consisted of lipid while others resembled granules from the typical granulated cells. Other cells with numerous inclusions appeared to be macrophages. Lysis of granulated cells in situ is compatible with suggestions that the metrial gland produces a holocrine secretion, though some normal granulated cells enter blood vessels. The stromal cells may have a phagocytic role in late pregnancy but evidence for this was inconclusive.

Morphologic and morphometric studies on human C cells in disorders of calcium metabolism.

The distribution of immunohistochemically detectable C cells in 49 human thyroid glands obtained at autopsy was investigated by determining the percentage of single-lying and grouped C cells. Eight patients suffered from primary, and 7 from secondary hyperparathyroidism; 2 had a hypercalcemia due to osteolytic bone metastases. Thirty two thyroids from normocalcemic patients (aged 0–76 years) served as controls. Innormocalcemic controls, two different C cells were found. Non-autolyzed tissue contained large, polygonal C cells with big, round nuclei. The orientation of the cytoplasm was such that its calcitonin-laden granules were adjacent to capillaries (type Ia). Autolyzed tissue displayed rounded C cells with small, pyknotic nuclei. The cytoplasm in proximity to the colloid appeared light-optically empty (type Ib). Sections passing through such cellular portions rendered their recognition as C cells impossible. Consequently, larger populations of C cells seemed to be subdivided into smaller cell groups. From birth to the age of 14 years, the number of visible C cells increased exponentially with a constant of 0.02/year. Inhypercalcemic patients (serum calcium >14mg%), neither immunohistochemical methods nor silver stains permitted the demonstration of C cells. They were obviously devoid of granules. Instates of uremia, hypocalcemia, and secondary hyperparathyroidism, a third type of C cells appeared (type II). The calcitonin-containing granules were scattered diffusely through the cytoplasm. Even when the nuclei were pyknotic, the cytoplasm did not display light-optically empty areas. Such cells retained their coherent, even follicular arrangement. A division into smaller subgroups was therefore lacking. In cases withprimary hyperparathyroidism whose calcium level had been lowered therapeutically prior to death, the overall distribution pattern of C cells corresponded to that in chronic hypocalcemia. The fall in serum calcium induced C cells to store calcitonin and the histologically empty forms were therefore absent. We conclude that the distinct cellular arrangement of demonstrable C cells as seen in different disturbances of calcium metabolism need not necessarily result from their cellular proliferation, but may well reflect their varying morphologic forms induced in part by autolysis and in part due to their functional state.

Behavioral and spatial change in response to an altered behavioral setting

A behavioral setting termed “free time” was identified in the dayroom of an institution for the retarded. The behavioral mapping technique was used to record behavior and spatial use within this setting. A 3-week period was identified in which the second week served as treatment period, and the first and third served as nontreatment periods. The second period consisted of placing novel materials into the dayroom in four conceptually distinct groupings: arts and crafts, games, empty, and lounge. During treatment patients engaged in more active and socially involved behaviors, avoided isolated behaviors and empty dayroom areas, and evidenced adaptive behavior to novel environmental objects. Discussion centers on the treatment implications of these changes, the use of the technique for future studies, and the methodological issues inherent in the procedure.

Spacing and calling in Pacific tree frogs, Hyla regilla

Calling male Pacific tree frogs space out more than if they were distributed at random on the available calling sites. When new frogs are added to an area that is already occupied by some calling males, fewer additional frogs call than in a control situation where frogs are added to an empty area. This shows that behavioral interactions between frogs limit the number that call in a local area. A further experiment showed that the mating call played through loudspeakers is sufficient to inhibit additional frogs from calling. We conclude that calling leads to spacing out, which in turn limits the density of calling frogs in a local area.

The Anolis Lizards of Bimini: Resource Partitioning in a Complex Fauna

The tiny island of South Bimini contains 4 species of lizards of he genus Anolis, a number surpassed only on the 4 largest islands of the Greater Antilles and on 2 very large and nearby satellite islands. These species are syntopic with respect to a two—dimensional area of the ground but divide the habitat according to perch height and perch diameter: sagrei is partly terrestrial but occurs more often on small and large low perches; distichus prefers the trunks and large branches of medium to large trees; angusticipes inhabits small twigs, especially at great heights; and carolinensis is found mostly on leaves or on the adjacent twigs and brances. The size classes of the species are staggered in such a way that the interspecific classes which overlap most in habitat overlap least in prey size. Similarities in prey size and prey taxa for classes of the same species are somewhat greater than those expected on the basis of habitat and morphology alone. The distribution of the species among the vegetation communities of Bimini can be explained on the basis of perch height and diameter preference. Within the same species, the larger lizards usually eat larger food, fewer items, and in sagrei more fruit; and they have a greater average range of food size per digestive tract. One species (distichus) is extremely myrmecophagous: about 75—90% of its food items are ants. In 3 of the 4 species, subadult males take more food and average smaller prey then females of the same head length. That species (distichus) which takes the smallest food items and whose classes overlap the most in habitat preference with those of other species is least dimorphic is size between the sexes. It is suggested that such small, nondimorphic species are best suited for insinuation into complex faunas, whereas larger, dimorphic forms are best for the colonization of empty areas. The usefulness of various measures of overlap and specialization is evaluated for this lizard association.

Utilization and Human Geography of the Deserts

THE PRESIDENT of the Institute, Professor R. F. Peel has given us an excellent review of the geomorphological aspects of the deserts.2 Although I am myself more a geomorphologist than a human geographer, I shall try to balance his address by some words on the human problems of the deserts, trying to testify, at least for myself, and perhaps at my own expense, to the old and worthy theory of the unity of geography, and to collect together some observations I have had the opportunity to make in the various deserts I have studied. Everybody knows that arid and semi-arid areas result from a deficit of water and humidity balance and that, consequently, the vegetation cover is sparse and poor. That is why these areas can only be occupied, first, by pastoral nomadic people, seeking pasture over the large area occupied by a tribe whenever it has been raining and the soil remains somewhat wet; secondly, by farmers gathered in generally rather small areas, called oases, where water is available for irrigation. When the rain is less scanty and its annual or seasonal distribution more suitable, pasture becomes more abundant and dry cultivation possible, so that either pastors or farmers can adopt new and more diversified types of soil utilization and of life, ranging from nomadism, semi-nomadism and transhumance to dry extensive or irrigated intensive agriculture. In any case, every type of people has to maintain relations, both economic and social, with its neighbours, because they need one another, the more so when they are exclusively nomadic or, on the contrary, gardeners in the oases. So that, when they live either inside the desert or in the semi-arid margins, people must cross these empty areas. The pastoral people, the owners of the beasts of burden, have, or had, to set up caravans; they were carriers and traders, related to the merchants of the towns, the main harbours of the desert, where the oases were halting places and markets along the roads. This, in a few words, is, or rather was till recent times, the traditional life, somewhat different from one place to the other, but everywhere well adapted to a most difficult and determining natural environment. It has been so for a long time; for, in the Old World, desert occupation by either pastoral or cultivating people can be noticed, at least since the last humid period of the Holocene, between 5,500 and 2,500 B.P., and probably before that time. And we know that agriculture could be even older in Asia, and in South America as well. Nowadays, if the people leading a traditional life in arid and semi-arid areas play a valuable role since they occupy very wide surfaces, they do not play the same part in world economic activity. Their number appears reduced if we compare it to the population of other climatic regions, and they appear frequently to the geographer as some of those archaisms which are typical of 'underdeveloped' countries. Now, in our time, natural conditions can be mastered better than formerly, but the new techniques are mainly applied to areas where they have the most

Electron microscopy of the localization of formic dehydrogenase in regenerating forms ofProteus vulgaris

The localization of the formic dehydrogenase system was studied by means of nitro-blue tetrazolium, using the ultrathin section technique, in large long bodies ofProteus vulgaris, which form the intermediate stage in regeneration of penicillin-induced spheroplasts. In the electron microscope, empty areas, numbering on an average four per cell section, were found at the site of formazan deposits, while in the controls (without tetrazolium salts) the average number was 0.05. From these findings, and from the findings of other authors showing that formic dehydrogenase is bound to cell structures, it can be concluded that inProteus cells this enzyme is bound to the cytoplasmic membrane.

The Empty Areas of the Northeastern United States

The Empty Areas of the Northeastern United States

The Witwatersrand a Unique Gold Mining Community

is now a vigorously growing industrial and manufacturing community. No other discovery of gold has wrought such a change. Other gold rushes have attracted settlers and helped to populate otherwise empty areas, such as California, Siberia, or Australia. But in none of these has the influence of gold mining been so forceful or lasting as to affect the entire nation. In every other gold mining area the mines have sooner or later declined in both relative