Search

Sixteen subjects, affected by chronic tension-type headache (TTH) accordingly to the International Headache Society Classification (1988) criteria, in presence of tenderness in pericranial muscles,with a mean age of 37 ± 11.8 years, and ten healthy volunteer subjects, age and sex matched, were submitted to postural analysis by Static Posturography (S.Ve.P. Amplaid). Aim of the study was to evaluate whether patients with TTH have disturbed postural control, as compared to normal subjects. Postural analysis considered all posturographic variables but focused on spectral frequency analysis of body sway. In both open (OE) and closed eyes (CE) condition, spectral frequency analysis showed a significantly increased body sway at low (OE= p⩽0.01; CE= p⩽0.01) and middle (OE= p⩽0.01; CE= p⩽0.01) frequencies on the antero-posterior ( y) plane and at low frequencies (OE= p⩽0.05; CE= p⩽0.05) on the lateral ( x) plane. Statistical analysis was performed using the Student's ttest for unpaired data, pvalue ⩽0.05 defined significant.

Starting from a model of the electron in 6-D spacetime which has been shown to give rise to the right values for spin and magnetic moment, if subject to an attractive potential due to vacuum polarization, the quantization of charged lepton masses is obtained with the additional hypothesis that a virtual pair of particles is created in the “time” subspace. This hypothesis suggests an infinity of charged leptons, each one in turn “fixing” the mass of a lighter one.

The electron is considered as a massless point-particle which moves in a spacetime with (3+3) dimensions subjected to a field that attracts it towards the (3+1) standard spacetime. This field is assumed to be described by the radial time component of the e.m. 6-potential and to be due to the vacuum polarization arising when the charge of the electron is removed from the (3+1) spacetime. The pertinent Klein-Gordon equitation in 6 dimensions is solved and the right values for the electron magnetic moment and spin are derived. The rest mass of the electron, as it appears in the standard (3+1) spacetime, is obtained as an integration constant from the motion in the two extra time dimensions. The very simple form assumed as a first approximation for the attractive potential does not give quantized rest masses.

AbstractRecent studies have suggested that the stylostome of parasitic larval water mites of the genus ArrenurusDugès is a product of the mite, not the host. We tested this hypothesis by comparing stylostomes of the similar species Arrenurus novimarshallaeWilson and Arrenurus pseudotenuicollisWilson formed in each of two mosquito species, Anopheles cruciansWiedemann and Anopheles quadrimaculatusSay: if the stylostome is produced by the mite, not the host, then stylostome form is likely to be constant in different host species parasitized by the mite.The stylostome of A. pseudotenuicollisis a short, broad, convoluted sac, and stylostomes within the two host species did not differ significantly. The stylostome of A. novimarshallaeis a long, thin, convoluted tube, and although it was significantly smaller in A. quadrimaculatusthan in A. crucians, its form remained constant. Dark pigment deposits around the stylostome’s attachment point and along the tube may represent host defense that reduces stylostome growth in A. quadrimaculatus. Laboratory-reared A. novimarshallaeoften die after a brief engorgement period on A. quadrimaculatusbut not on A. crucians.Thus, the stylostome of these two mite species has a consistent form in each of two host species, an observation compatible with the hypothesis that the stylostome is a product of the mite. In addition, the ease of distinguishing these two mite species on the basis of stylostome morphology attests to the potential value of the stylostome as a taxonomic character.

Resource partitioning was studied in 20 species of the water mite genus Eylais, the larvae of which parasitize adult Coleoptera and Hemiptera living in shallow ponds. Co—existence of sympatric species is possible because the mites exploit host resources in different ways. Most commonly they parasitize different species, but when hosts are identical, the mites remain segregated by differences in the precise site of attachment, biotope, or season of parasitism. Mite biology, host dispersal, and competition for attachment sites from other water mite species may restrict further subdivision of host resources.

Hill, L. R. (Università Statale, Milano, Italy), L. G. Silvestri, P. Ihm, G. Farchi, and P. Lanciani. Automatic classification of staphylococci by principal-component analysis and a gradient method. J. Bacteriol. 89:1393–1401. 1965.—Forty-nine strains from the species Staphylococcus aureus, S. saprophyticus, S. lactis, S. afermentans, and S. roseuswere submitted to different taxometric analyses; clustering was performed by single linkage, by the unweighted pair group method, and by principal-component analysis followed by a gradient method. Results were substantially the same with all methods. All S. aureusclustered together, sharply separated from S. roseusand S. afermentans; S. lactisand S. saprophyticusfell between, with the latter nearer to S. aureus. The main purpose of this study was to introduce a new taxometric technique, based on principal-component analysis followed by a gradient method, and to compare it with some other methods in current use. Advantages of the new method are complete automation and therefore greater objectivity, execution of the clustering in a space of reduced dimensions in which different characters have different weights, easy recognition of taxonomically important characters, and opportunity for representing clusters in three-dimensional models; the principal disadvantage is the need for large computer facilities.

The effect of 2 species of water mites on the instantaneous death rate of their hosts was measured on the basis of laboratory experiments. In both parasite-host association — the parasitic water mite Hydryphantes tenuabilis on the aquatic insect host Hydrometra australis and the parasitic water mite Arrenurus pseudotenuicollis on the mosquito Anopheles crucians — the effect of mite load on the instantaneous death rate of the host appeared to be linear. Also, the impact of a single parasite on the host's death rate was apparently related to the ratio of parasite to host body weight. The results of this study are in general agreement with recent theoretical investigations of the regulation of host populations by parasites.

Pigmented eyespot size of the benthic cladoceran Simocephalus exspinosus was measured in individuals sampled from four freshwater ponds that differed in the extent of visually-oriented predation. In ponds with such predation (from fish, salamander larvae, and dragonfly nymphs), eyespot size was found to be significantly smaller, relative to body size, than in a pond without visually-oriented predation. Reduction in pigmented eyespot size may represent an adaptation to reduce vulnerability to predation.

Several letters to the editor are presented including one which conveys the gratitude of a reader for the website of the journal, a poem on Madame Alexander Doll Club (MADC) and one which expresses the printing problem of a subscriber and a response from the editor.

The number of larval water mites of the genus Arrenurus attached to the mosquito host Anopheles crucians was compared with the number of stylostomes present in the host tissues to determine the pattern of mite detachment from the host. All hosts carrying small and lightly pigmented mites had the same number of attached mites and stylostomes, indicating that detachment does not occur among mites that are not highly engorged. However, the number of attached mites was often less than the number of stylostomes in hosts carrying large and heavily pigmented mites, indicating that detachment does not necessarily occur synchronously at the time of oviposition of the mosquito but that some mites detach prior to oviposition. Survival of detached mites in laboratory rearings increased as individuals grew to lengths greater than 0.25 mm, a size that would place a mite in the larger and heavily pigmented class. If such mites fell into water as they left the host, they would stand a good chance of surviving.

The effect of parasitic larvae of the water mite Arrenurus pseudotenuicollis on adult, female mosquitoes of Anopheles crucians was determined from laboratory experiments on field-collected, nulliparous mosquitoes. The parasites significantly reduced the survivorship of both starved and raisin-fed, unengorged female mosquitoes. They significantly reduced the number of eggs produced by both field-engorged and laboratory blood-fed mosquitoes. In field collections of nulliparous An. crucians, the proportion of unengorged females bearing parasites was always higher and the average number of parasites carried by unengorged females was always greater than in engorged females. These results suggest that heavily parasitized females have a higher probability of dying before they feed on blood than do unparasitized or lightly parasitized females.

The effect of parasitic water mites on a natural population of their mosquito host was investigated by noting differences between the average number of mite stylostomes in 2 age groups of the host. In 6 consecutive samples, the average number of stylostomes was always higher in young than in old hosts, a consequence apparently of the higher mortality suffered by individuals that carried larger mite loads,

All active stages of the marsh treader Hydrometra myrae Bueno are attacked by larvae of the water mite Hydryphantes tenuabilis Marshall, but the parasitic mites become fully engorged on only adult hosts. All mites attach for the 1st time by jumping onto the host from the water surface, but as the host molts, the mites crawl to the next instar. Initially attaching mites predominate on the venter and legs; transferring mites on the dorsum of the host. Adult hosts bear mites of similar sizes on the dorsum because transferring mites attach simultaneously and engorgement proceeds at the same rate, but they carry mites of smaller and variable sizes on the venter and legs because initially attaching mites can parasitize the host for as long as 6 or 7 days after ecdysis. The incidence of parasitized hosts and the mean number of mites per host increase as the host develops from instar I to the adult. Mite loads appear to be linearly related to host age.