The epidemiology of hydatidosis with special reference to the Mediterranean area.

In the Mediterranean area 2 subspecies of Echinococcus granulosus exist: E. g. equinus and E. g. granulosus. The latter is divided into sheep, cattle, pig and camel strains, the adult forms of which mainly occur in farm-dogs but sometimes in wild canidae. Some of these strains can infect man: namely, the sheep and the pig strain. The infectivity of the cattle strains for man is not certain. The epidemiological cycle is mainly a rural one, but it can become sylvatic or even urban. Thus, the epidemiological features of hydatidosis in the Mediterranean area are not basically different from the general epidemiology of the disease. But extensive rearing of sheep, combined with the carelessness and ignorance of people and with some particular habits, favours the maintenance of the infection.     

Production and properties of theta-toxin of Clostridium perfringens with special reference to lethal activity.

theta-Toxin of Clostridium perfringens produced in a synthetic medium showed high toxicity. The mouse was killed with 5-10 hemolytic units of the toxin. Neutralization experiments showed that lethal and hemolytic activities were due to the same toxic entity. The amount of theta-toxin expressed in lethal activity reached more than 30% that of alpha-toxin in the synthetic medium SM67. Although the activities of alpha-and theta-toxins were not additive in terms of LD50, increase in the ratio of theta-toxin to alpha-toxin resulted in reduction of the survival time of the mouse injected with a lethal dosis of the mixture of the two toxins when compared with alpha-toxin alone. Unlike those produced in other media, the hemolytic and lethal activities of theta-toxin produced in the synthetic medium was not activated by reduction with thioglycollate, even after partial purification. In other respects, the toxin was not different significantly from those reported in the past. The toxic form was detected also in complex medium. It was suggested that theta-toxin may be produced as a nascent entity.     

The biogeography of species,with special reference to ferns

An important element of the biogeography of species is the geographic aspects of speciation. The geography of species has a role in the processes of speciation which have a reciprocal role in species geography. The homosporous ferns provide an especially favorable group for biogeographic studies because nearly all species have an equivalent capacity for dispersal and migration. Species ranges are based on the ecology of the environment, rather than on animal vectors of dispersal or pollination. However, with allowance for these differences, the processes of geographic speciation are basically the same in ferns and other vascular plants, although often on a broader geographic scale in the ferns. Speciation most frequently produces a new species with a small range, which can rapidly expand to occupy the geography of the environment to which the species is adapted. The members of a closely related speciesgroup retain their morphological and geographic relations for a relatively short time. With speciation, changes in distribution, and extinction, the original relations of the species and the biogeographical history of the group will be lost. High regional species diversity occurs in the wet mountainous regions of the tropics, where there is greatest ecological diversity and maximal opportunities for speciation and persistence.     

Identification of species and capsular types of Klebsiella clinical isolates, with special reference to Klebsiella planticola

In the 77 reference strains for Klebsiella K types, there are 17 strains (22.1%) of Klebsiella planticola, 6 strains (7.8%) of Klebsiella oxytoca, 1 strain (1.3%) of Klebsiella terrigena, and 53 strains (68.8%) of Klebsiella pneumoniae. The species K. planticola, which was originally isolated from botanical and aquatic environments and hence thus named, was also identified at high incidence (81 strains, 18.5%) among the 439 recent clinical isolates of Klebsiella species. Among these K. planticola strains of hospital origin, 52 (64%) were isolated from sputum, 17 (21%) from urine, and the remaining 12 (15%) from other sources. The capsular types of these isolates were determined by the gel precipitation reaction. Seventy of 81 K. planticola isolates (86.4%) were typable by antisera to Klebsiella reference strains for K types and the K types of the clinical isolates distributed to 35 kinds of K types. The proportion of typable strains among clinical isolates of K. planticola was very similar to those in K. pneumoniae (87.5%) and K. oxytoca (86.0%).     

Association of beta2 toxin production with Clostridium perfringens type A human gastrointestinal disease isolates carrying a plasmid enterotoxin gene

Clostridium perfringens type A isolates carrying an enterotoxin (cpe) gene are an important cause of human gastrointestinal diseases, including food poisoning, antibiotic-associated diarrhoea (AAD) and sporadic diarrhoea (SD). Using polymerase chain reaction (PCR), the current study determined that the cpb2 gene encoding the recently discovered beta2 toxin is present in <15% of food poisoning isolates, which typically carry a chromosomal cpe gene. However, >75% of AAD/SD isolates, which usually carry a plasmid cpe gene, tested cpb2(+) by PCR. Western blot analysis demonstrated that >97% of those cpb2(+)/cpe(+) AAD/SD isolates can produce CPB2. Additional PCR analyses, sequencing studies and pulsed field gel electrophoresis experiments determined that AAD/SD isolates carry cpb2 and cpe on the same plasmid when IS1151 sequences are present downstream of cpe, but cpb2 and cpe are located on different plasmids in AAD/SD isolates where IS1470-like sequences are present downstream of cpe. Those analyses also demonstrated that two different CPB2 variants (named CPB2h1 or CPB2h2) can be produced by AAD/SD isolates, dependent on whether IS1470-like or IS1151 sequences are present downstream of their cpe gene. CPB2h1 is approximately 10-fold more cytotoxic for CaCo-2 cells than is CPB2h2. Collectively, these results suggest that CPB2 could be an accessory toxin in C. perfringens enterotoxin (CPE)-associated AAD/SD.     

The problem of proprietary dyes,with special reference to alamar blue,a proprietary dye revealed

A short strip of adhesive transfer cellophane tape is applied to the face of the block to provide backing for the section during cutting and handling. The tape is sealed to the nuclear track plate with the section against the dry emulsion. After exposure the cellophane backing is removed by immersion in water, and the adhesive is dissolved from the section in unleaded gasoline. The section is hydrated and photographic and histological processing are carried out in the usual manner.     

The blastomere periphery ofXenopus laevis,with special reference to intercellular relationships

Summary The peripheral region of theXenopus laevis blastomere is considered to be comprised of the extracellular material, the plasma membrane and the subsurface cytoplasm. These regions were examined with the electron microscope during cleavage and blastula stages (stages one to seven, Nieuwkoop and Faber, 1967). The cell contact relationships varied according to the location of the cell in the embryo. Superficially, a dense terminal junction occurred, possessing point contacts where the membranes approached to within 30 Å. More deeply, a variety of relationships appeared: wide intercellular spaces bridged by pseudopodia, long regions of unbridged parallel membrane or complex interdigitation. Tight junctions were found in limited numbers and developed at about stage seven. Extracellular material was examined using histochemical techniques on dissociated andin situ cells. The latter had appreciable amounts of such material, but dissociated cells reacted inconsistently to different techniques. The cytoplasm subjacent to the membrane possessed a filamentous network at all stages examined, but extensive microfilament tracts and microtubules appeared only at gastrulation.