Possible role of cell cycle-dependent morphology,geometry, and mechanical properties in tumor cell metastasis

Studies that examine the shear- and abrasion-sensitivity of proliferating cells are important in order to understand the behavior of hybridoma cells in bioreactor culture and metastasizing cancer cells in the bloodstream. Little is known about the link between morphology, structure, and mechanical properties of a given cell line, especially with respect to variations throughout the cell cycle. In our experiments with GAP A3 hybridoma cells, distinct cell morphologies were identified and correlated with phases of the cell cycle by video microscopic observation of synchronized cells, and of individual cells that were followed throughout their cell cycle. Micropipet manipulation was used to measure the geometrical (cell volume) and mechanical (apparent cell viscosity) properties of single cells. As the cell cycle progressed at 37°C, an increase in cell volume from 1400 μm³ to 5700 μm³ was accompanied by an increase in apparent cell viscosity from 430 poise to 12,000 poise, consistent with an accumulation of more cytoplasmic material in the “older” cells. Hybridomas are representative of the various leukemias derived from hemopoietic cells, and even though as a whole, they appeared to be rather shear-insensitive, the wide range of property values demonstrates that a given cell line cannot be characterized by a single value for any one property, and that properties must be related to the cell cycle when considering proliferating cells. It is interesting to see if distinct stages in the metastatic sequence of events might correlate with any of these physical features of the cell cycle, irrespective of cell type or cell line. For example, the cytokinetic doublet could represent a fragile structure that may fail and produce cell death under fluid-shear conditions that would not affect the cells at any other stage in the cell cycle. Identifying such cell cycle-dependent features in metastasizing cancer cells could lead to a better understanding of the metastatic process and to possible clinical treatments directed at making cells more shear- and abrasion-sensitive, and therefore, more likely to be killed by the natural hydrodynamic forces of the circulatory system.     

The ecology of marine exploitation in prehistoric Hawaii

Archaeological evidence for prehistoric strategies of marine exploitation in Oceania may be profitably analyzed from an ecological perspective, in which individual sites and assemblages are viewed in the context of adaptation to local environmental constraints. This perspective is illustrated through the contrastive analysis of environment, technology, and faunal remains at three prehistoric Hawaiian sites. Differing strategies of marine exploitation evidenced for each site are shown to reflect local marine environmental conditions. An ecological approach shows greater promise for an understanding of prehistoric adaptation to marine environment than the typological analyses current in much archaeological work on fishing.     

Selection of malignant melanoma variant cell lines for ovary colonization

Murine melanoma line B16-F1, which shows some specificity for metastatic organ colonization of lung but rarely metastasizes to ovary, was used to select variant cell lines with increased preference for experimental ovary metastasis. Ovary-colonizing melanoma cell lines were sequentially selected in syngeneic C57BL/6 mice by repeated intravenous administration and surgical recovery of ovarian melanoma tumors for tissue culture. After ten selections for experimental ovary metastasis, line B16-010 was established which formed experimental metastatic ovary tumors in almost every test animal. In tissue culture B16–010 cells grew in circular in circular colonies with rounded, smooth cell peripheries compared to B16-F1 cells which were flatter, grew in irregular patterns, and exhibited long cellular projections. Ovary-selected B16 lines contained less melainin pigment (B16-010 < B16-05 < B16-01 ? B16-F1) compared to the parental melanoma line. Together with previous cloning and selection data, these results are consistent with the preexistence of highly malignant cells in the parental tumor population that possess the ability to metastasize to specific organs.     

Complementarity of thermoregulatory rhythms in Micropterus salmoides and M. dolomieui

Largemouth (Micropterus salmoide) and smallmouth (M. dolomieui) blackbasses tested in an electronic shuttlebox exhibited behavioral thermoregulatory rhythms which were temporally complementary. With a LD 12 : 12 photoperiod, M. dolomieui exhibited a preferred-temperature peak of 30.1°C during the latter portion of the photophase, when M. salmoides reached a minimum of 27.1°C. M. dolomieui exhibited a minimum of 26.6°C during the latter portion of scotophase, while M. salmoides remained at a significantly higher plateau of about 29°C, with a peak of 29.5°C at the midpoint of scotophase. The phase relations of the thermoregulatory rhythms relative to photoperiod suggest that they are endogenously timed circadian rhythms entrained by photoperiod. The thermotemporal complementarity of these rhythms suggests an aspect of niche segregation between these largely sympatric congeneric species.     

Evolution, origin and age of lineages in the Californian and Mediterranean floras

This paper addresses some of the conceptual issues involved in the analysis of the age and origin of mediterranean‐climate plant taxa, paying particular attention to three topics: (1) the importance of an explicit time frame in the definition of biogeographical origins, (2) the distinction between the age of traits and the age of taxa, and (3) the idea of mediterranean‐type ecosystems as environmental islands. (1) In California, recent analyses demonstrate that the diversity of species derived from different biogeographical origins is significantly correlated with temperature and precipitation gradients. These patterns support the hypothesis that niche conservatism is an important factor structuring modern diversity gradients. However, depending on how far back in time one looks, a species may be assigned to different origins; future discussions of biogeographical origins need to address the appropriate time frame for analysis. (2) Past research has demonstrated distinctive trait syndromes among woody plants of the Mediterranean, Chile, California and Mexico, and proposed that the syndromes are associated with lineages of different age in these floras. Reanalysis of individual traits demonstrates greater variability among regions than previously reported. The classification of plants into ‘old’ and ‘new’ genera is re‐evaluated, and it is suggested that greater attention be paid to the age of traits, rather than to the age of taxa, especially at an arbitrary rank such as genus. (3) The idea of mediterranean‐climate regions as ‘climatic islands’ is examined. Space–time diagrams of climate enable one to view the emergence of distinctive climatic regions in a continental context. The terms ‘synclimatic’ and ‘anticlimatic’ are proposed, referring to migration routes that parallel climate contours in space and time versus those that cross contours (including the case of geographic stasis in the face of climate change), respectively. Mediterranean‐climate regions have served as important case studies in plant ecology and evolution, and merit continued close examination in the light of continued advances in phylogenetics and palaeoecology.     

Lymph node colonization induces tumor-immune tolerance to promote distant metastasis

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The role of causal knowledge in the evolution of traditional technology

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