Cytochalasin D (CD) was used to perturb actin filaments of the Sertoli ectoplasmic specialization (ES)--a cytoskeletal complex of the Sertoli cell related to spermatids. CD (500 microM for 6 h) produced a loss of 88% of the ES facing the head region of early (Step 8) elongating spermatids as compared to vehicle (dimethylsulfoxide:saline) controls. Nitrobenzoxadiazole-phallacidin staining of F-actin revealed a CD-related loss of uniform fluorescence over the head of elongated spermatids. To examine for a possible relationship between the presence of actin and cell attachment at ES sites, hypertonic fixatives were introduced to provoke cell shrinkage and stress ES-associated junctions. After osmotic stress, cell-to-cell adhesion at ES sites remained intact in vehicle-treated animals. CD treatment caused Sertoli cells to separate from elongating spermatids at sites where ES had been lost from the Sertoli cell surface. It is suggested that actin of the ES plays a role in cell-to-cell interaction analogous to its possible role at the Sertoli cell barrier. In CD-treated animals, structures resembling tubulobulbar complexes frequently developed at sites where ES was lost, suggesting that the loss of ES has a facilitatory role in tubulobulbar complex formation. It is hypothesized that tubulobulbar complexes are devices that rid the cells of ES-associated junctional links to effect dissociation of the spermatid from the Sertoli cell during spermiation. Spermatids at Step 8 of development are known to become oriented with their acrosomes facing the base of the Sertoli cell. After CD treatment, a 5.8-fold increase in malorientation of Step 8 spermatids was noted. A role for the ES cytoskeletal complex in orienting the spermatid acrosome toward the basal aspect of the Sertoli cell is also suggested.

Modern cities are characterised by intense human interactions and economic activities that- in many cases- have little or no consideration of the surrounding environment. Every day, the process of urbanisation is becoming more resource-intensive, and the results are grave, including, climate change, the loss of natural fertility of farmland and the loss of biodiversity all over the world. High-consumption modern lifestyles are mainly fossil-fuel powered, relying on resources from the world’s ecosystems: a practice that increases the ecological footprints of cities. This paper aims at exploring means of decreasing the ecological footprints of cities: regenerative urban development practices being some of them. By concentrating on one of these practices, namely urban agriculture, the paper demonstrates how it would be possible to decrease the ecological footprints of cities through its integration on the city level.It starts out by briefly defining the environmental problems our cities are facing today, then it moves on to explaining the concept of the ecological footprint. It shows how cities could decrease their ecological footprints through simple practices: such as those of regenerative urban development. This is done through demonstrating regenerative practices in different parts of the world, with a concentration on urban agriculture, as one of the most effective regenerative practices. It then moves on to explaining how it could be integrated within a comprehensive system in cities, so as to improve the environmental condition, to work on decreasing the ecological footprint and to start setting the stage for a regenerative city.

Modern cities are characterized by intense human interactions and economic activities that in many cases have little or no consideration of the surrounding environment. Every day, the process of urbanization is becoming more resource-intensive which results in climate change, the loss of natural fertility of farmland, and the loss of biodiversity all over the world. High-consumption modern lifestyles are mainly fossil-fuel powered and rely on resources from the world’s ecosystems; a practice that increases the ecological footprints of cities. This paper aims at exploring the means of decreasing the ecological footprints of cities; regenerative urban development practices being some of them. By concentrating on one of these practices, namely urban agriculture, the paper demonstrates how it would be possible to decrease the ecological footprints of cities through its integration on the city level. It starts out by briefly defining the environmental problems our cities are facing today and then moves on to explaining the concept of the ecological footprint. It shows how cities could decrease their ecological footprints through simple practices such as those of regenerative urban development. This is done through demonstrating regenerative practices in different parts of the world with a concentration on urban agriculture as one of the most effective regenerative practices. It then moves on to explaining how it could be integrated within a comprehensive system in cities in order to improve the environmental condition. It also explains how to work on decreasing the ecological footprint in order to start setting the state for a regenerative city.

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