Ultrasound; its effect on the cardiovascular system when applied over the carotid sinus and stellate ganglion

In a study of 29 patients to observe untoward reactions to applications of ultrasound over the carotid sinus and stellate ganglion areas, it was noted that cough was evoked in five patients, premature ventricular systoles in three and a burning sensation of the skin at the point of treatment in five. No considerable effect on heart rate or blood pressure was observed.     

Production and litter processing by crayfish in an Appalachian mountain stream

SUMMARY 1. Mean annual density and biomass () of Cambarus bartonii in an Appalachian mountain stream (U.S.A.) was 12 individuals m⁻² and 1669 mg (ash-free dry weight) m⁻².
2. Annual production ( P ) of C bartonii was 961 mg AFDW m⁻². Despite high biomass, low growth rates resulted in low production and a low P/ ratio of 0.58.
3. While C bartonii constituted 61% of the total macroinvertebrate biomass, it contributed only 13% of annual community secondary production.
4. Litter processing was positively related to temperature and crayfish size. Cambariis bartotnii was estimated to comminute 36 g m⁻² y⁻¹ of leaf litter (>1 mm²) to 24 g m−^>2 y⁻¹ fine particulate material (<1 mm²). The annual pattern of litter comminution by crayfish was regulated by temperature. As a result, >5()% of shredding activity by crayfish occurred from June to September which was also the period of lowest litter standing crops and activity of other shredding macroinvertebrates.
5. We speculate that during summer crayfish play an important role in temperate woodland streams by converting slowly processed leaf litter species (e.g. Rhododendron ) to fine particles which are then available to collector-gatherers (e.g. Chironomidae, Oligochaeta).     

Shoot growth and morphometric analyses of Serengeti graminoids

Nine species from the Serengeti National Park, Tanzania, were studied to provide morphometric and growth rate parameters for a simulation model of their growth (Coughenour, McNaughton & Wallace, 1984). Short grasses had a much greater capability than taller species for packing a large number of shoots with a high proportion of lamina on a given crown biomass. Absolute growth rates varied with species height group, shoot type and growth phase. The frequency distribution of growth rates indicated that maximum growth rates were similar but that modal growth rates decreased with height. This may be an important trait allowing short grasses both to endure unfavourable conditions and to effectively exploit transient showers and resultant water availability. The ability of smaller-statured specie's to concentrate a high number of shoots with a large proportion of blade on a given crown area is an effective mechanism for increasing productivity early in the growing season. Taller grasses could achieve the same production rates as short grasses only with greater individual growth rates of fewer shoots. These patterns may help to explain gradients of graminoid stature along rainfall and growing season gradients.     

Coexistence of competing species of seaweed flies: the role of temperature

Abstract.

• 1 Competition is shown to be occurring within and between the congeners Coelopa frigida and C.pilipes; it is noted that the two species frequently coexist despite ongoing competition.
• 2 Observations on natural wrack-beds indicate that there is a marked difference in the distributions of the larvae: C.frigida larvae aggregate in cooler parts of the bed, C.pilipes in warmer parts. This difference in microdistribution reflects a broader-scale difference in the geographical distributions of the species - C.pilipes being the more southerly of the two.
• 3 The larval distributions are shown to be caused primarily by the behaviour of the larvae themselves - not by choices made by ovipositing females, nor (at least to any great extent) by differential survival.
• 4 The different micro-distributions within beds constitute a form of niche difference which will cause competitive abilities to be frequency-dependent and hence have a stabilizing effect. It is possible that this effect may be supplemented by others; and, in particular, effects operating at the level of the‘linear meta-population’may be worthy of further investigation both in Coelopa and in other coastal species.

     

Alternative Model for Gene Amplification

The number of nucleoli increases shortly after the conversion of germ cells into oogonia or spermatogonia in Xenopus laevis. This event demands a modification of the theory of gene amplification. A new explanation is proposed which involves non-chromosomal genes restricted to the germ-line.     

Establishment of Ureolytic Staphylococci in the Rumen of Gnotobiotic Lambs

Six strains of ureolytic staphylococci isolated from rumen digesta and the rumen wall of conventionally reared sheep were inoculated per os into two germ-free lambs. High numbers of staphylococci established in rumen fluid, and urease activity and normal NH₃ and urea concentrations were maintained for approximately 4 weeks until slaughter. Staphylococci were found also to be associated with the rumen wall, conferring urease activity on this tissue.     

The identification of British limnephilid larvae (Trichoptera: Limnephilidae) which have single-filament gills

SUMMARY. Keys are provided to identify those British limnephilid larvae which are characterized by having gill sites occupied solely by single filaments at the final instar. Most species can be identified at the final instar but many species can also be identified at the earlier instars. A key is also supplied to distinguish the early instar larvae as a group from other limnephilid larvae. Brief notes on distribution and habitat are given. The species identified at least at the final instar are:- Apatania wallengreni, A. auricula, A. muliebris, Drusus annulatus, Ecclisopteryx guttulata, Potamophylax latipennis, P. cingulatus, P. rotundipennis, Melampophylax mucoreus, Allogamus auricollis, Hydatophylax infumatus, Chaetopteryx villosa . It was not possible to segregate Halesus radiatus from H. digitatus, Stenophylax permistus from S. vibex , or S. lateralis from S. sequax .