Spatial epidemiology: an emerging (or re-emerging) discipline

Spatial epidemiology is the study of spatial variation in disease risk or incidence. Several ecological processes can result in strong spatial patterns of such risk or incidence: for example, pathogen dispersal might be highly localized, vectors or reservoirs for pathogens might be spatially restricted, or susceptible hosts might be clumped. Here, we briefly describe approaches to spatial epidemiology that are spatially implicit, such as metapopulation models of disease transmission, and then focus on research in spatial epidemiology that is spatially explicit, such as the creation of risk maps for particular geographical areas. Although the spatial dynamics of infectious diseases are the subject of intensive study, the impacts of landscape structure on epidemiological processes have so far been neglected. The few studies that demonstrate how landscape composition (types of elements) and configuration (spatial positions of those elements) influence disease risk or incidence suggest that a true integration of landscape ecology with epidemiology will be fruitful.     

New and old problems in the taxonomy of the Gelidiales (Rhodophyta)

The order Gelidiales includes over 140 agar-producing taxa. Many species are taxonomically confused; the boundaries of one family and all but four genera recently have been contested, and the controversy over ordinal status has lasted for over 25 years. This study reviews recent developments in the taxonomy of the group and suggests future areas for studies. The order cannot be defined by a few exclusive characters, as intended in the past, but it shows a unique combination of characters. Additional studies on Gelidiella and Acanthopeltis seem advisable to clarify family limits. The segregation of Onikusa and Pterocladiastrum is doubtful. Only three of six characters discriminate Gelidium from Pterocladia. None allows complete generic segregation and all need variability studies. Analysis of nomenclatural types in the light of morphological variation would permit an understanding of species limits in Gelidium and Pterocladia. Similar studies are needed in Gelidiella and Ptilophora.     

Seed dispersal and seedling emergence in an old field community in central New York (USA)

Summary Seed dispersal and seedling emergence of common taxa growing in a Solidago-dominated old field in central New York (USA) were monitored from May 1982 to June 1984. Over 3.5x10⁴ seeds per m² were captured on seed traps in each of the two years, with peaks occuring in July (due to Hieracium) and in November (due to Solidago). About 4.0x10³ seedling/m² emerged beneath the intact community in each of the two years. Although seedlings emerged predominantly in the early spring, a secondary peak occurred in September and October when many seedlings of introduced grasses appeared. Two additional aspects of the reproductive biology of the major taxa were related to the seasonal timing of seed dispersal: As the date of peak seed dispersal (among taxa) became progressively later in the season, (1) the duration of dispersal increased from about one week to about one-half year, and (2) the delay between the peak of seed dispersal and the peak of seedling emergence increased from a few days to about one-half year.     

New glimpses of an old machine.

Two recent studies illustrate the ability of the Mre11/Rad50 DNA repair complex to bind and connect DNA ends. Specific stimulation of DNA ligase IV-mediated end-joining by Mre11 complexes from S. cerevisiae suggests the possibility of a direct role in nonhomologous end-joining in eukaryotic cells.     

New functions of an old protein: the eukaryotic porin or voltage dependent anion selective channel (VDAC)

Mitochondrial porin or VDAC (Voltage Dependent Anion selective Channels) was identified for the first time in 1976, on the basis of the evolutionary similarity between the gram negative and mitochondrial outer membranes. Since this achievement VDAC has been extensively investigated: its functional features have been sharply defined upon reconstitution in artificial membranes and its sequence has been determined in many genomes. Unfortunately the tertiary structure has not yet been solved, mainly because it proved to be very difficult to get suitable crystals. Despite this established knowledge, in the last few years this protein has attracted renewed interest. There are two main reasons for this interest: the discovery, in most eukaryotes, of a family of genes encoding VDAC isoforms and the claims of VDAC involvement in the intrinsic pathway of apoptosis and in particular in the mechanism of cytochrome c release from mitochondria. We can affirm that nowadays the eukaryotic porin (or VDAC) is studied in a more general cellular contest, looking at the interactions and integration with other molecules, since VDAC is in a crucial position in the cell, forming the main interface between the mitochondrial and the cellular metabolisms. In this minireview we will briefly focus our attention onto the following topics: 1) recent advances about the structure of VDAC; 2) the VDAC-related multigene families; 3) the presence, targeting and function of VDAC in various cell membranes.     

New roles for an old molecule in axon-glial interaction

Axons need to be above a minimum size before they can be ensheathed by myelin-forming glia. But it has generally been assumed that the axonal signals that initiate myelination, whatever they are, would act similarly in both the CNS and the PNS. The surprising finding of Chan et al. in this issue of Neuron is that NGF can act as a regulator of ensheathment but that it has opposite effects on CNS and PNS axons.     

Milk molars or extra premolars in Mesotheriinae (Mesotheriidae,Notoungulata): New insights into an old controversy

A recently recovered specimen of Mesotheriinae (Mesotheriidae, Notoungulata) from the late Miocene-early Pliocene of La Rioja Province (Argentina), CRILAR Pv 433, corresponds to an individual with three upper premolars, which appears to be an “anomaly” among mesotheriines. The detailed study of this specimen, however, brings up an old controversy on the interpretation of different mesotheriine specimens with three upper or two lower premolars. After being described as different taxa, these were later considered to be juvenile representatives of other known species. The three upper or two lower teeth were interpreted as the milk molars DP2–4 and dp3–4, respectively, which would be replaced in adult life by two upper (P3–4) and one lower (p4) permanent premolars. The new material leads us to set up a different interpretation. In our opinion, all these specimens actually preserve the permanent dentition, corresponding to different ontogenetic stages of more or less young individuals. This consideration implies the necessity of a deep systematic revision of the whole subfamily, keeping in mind this new point of view and the ontogenetic variation within a species. Therefore, the presence of P2/p3 is not enough to define a different taxon at this moment. Pending this taxonomic revision, the dental morphology of CRILAR Pv 433 resembles both Typotheriopsis (e.g., upper premolars with one labial sulcus) and Pseudotypotherium (e.g., P4 with lingual groove, wide median lobe of M3) as these two late Miocene genera are currently characterized. Furthermore, P2/p3 could be expelled soon in the lifetime of individuals, and even the presence of P2/p3 could be a variable character within the same taxon; if so, this might reflect an evolutionary trend to the loss of a dental element within mesotheriines, but the revision of a large sample is necessary to support or reject these hypotheses.     

Study of the "survival" of knowledge among graduates of a sanitation and hygiene college with regard to epidemiology and ways of improving the teaching of this discipline]

The authors present the results obtained in the survey of graduates from the sanitary and hygienic departments of 4 medical institutes of the Ukrainian SSR carried out in a special pedagogical experiment with the aim to determine the "survival" of their knowledge in epidemiology. As a result, variations in the stability of knowledge in different branches of this discipline, especially in disinfection, the problems requiring the integration of knowledge in epidemiology and hygiene (municipal and alimentary), etc., have been revealed. The authors propose some measures for the improvement of teaching.