Role of intracortical inhibition in forming homo- and heterosensory interaction in sensorimotor cortex neurons in kittens

Homo- and heterosensory interaction were investigated in sensorimotor cortex neurons before and after picrotoxin application to anesthetized and immobilized kittens belonging to three age groups (12–30 days, 31–47 days, and 2–4 months old). Only slight inhibition of response to presentation of a second stimulus was observed in a small proportion of cells in the youngest age group at test intervals of 100, 200, and 300 msec. Picrotoxin application only produced the effect of raised background activity. Numbers of neurons with partially or fully inhibited response to test stimuli (especially spaced at 100 msec intervals) rose in the middle and older age groups. The dynamics of heterosensory interaction and how this is affected by picrotoxin application gradually approximated to that observed with adult animals. The subject of the development of inhibitory mechanisms and how they contribute to the organization of homo- and heterosensory interaction during early postnatal ontogenesis is considered in the light of the results obtained.A. A. Ukhtomsii Institute of Physiology, Leningrad. A. A. Zhdanov State University, Leningrad. Translated from Neirofiziologiya, Vol. 20, No. 2, pp. 234–243, March–April, 1988.     

Infections with Francisella tularensis biovar palaearctica in hares (Lepus timidus, Lepus europaeus) from Sweden

The occurrence of tularemia was studied in 1,500 hares submitted to the National Veterinary Institute, Uppsala, Sweden for postmortem examination during 1973 through 1985. A total of 109 tularemia cases was recorded based on the fluorescent antibody (FA) test for Francisella tularensis and on the gross and microscopic pathology. Tularemia was diagnosed only in the varying hare (Lepus timidus) and not in the European brown hare (Lepus europaeus). The geographical distribution of the 109 cases indicates that tularemia has not spread in Sweden during the last 45 yr, with the exception of an endemic occurrence of the disease on the island of Stora Karls? in the Baltic sea. The disease was most frequent in the autumn and only a few cases were recorded during winter. Cases were not seen in the spring. The annual prevalence varied, with several cases in 1974 and 1981, but there were no cases in 1976 and 1980. The postmortem findings in hares dying of tularemia in the autumn were characterized by focal coagulative necrosis in liver, spleen and bone marrow, with high numbers of bacteria FA-positive for F. tularensis. In hares dying during winter months, the most characteristic findings were hemorrhagic enteritis and typhlitis, although necrotic lesions could occur in liver, spleen and bone marrow. Diseased hares on the island of Stora Karls? were demonstrated to be infected with ticks, while hares on the mainland of Sweden generally were fed upon by mosquitoes. Twenty-six of the 109 hares with tularemia were examined bacteriologically and F. tularensis biovar palaearctica was isolated from eight. The lung extract antibody test for F. tularensis was performed in 18 of the 109 hares. All were negative. In addition to the field study, an experimental study with F. tularensis biovar palaearctica was performed. Four varying hares and three European brown hares were inoculated. None of the hares died from tularemia, and generalized infection was not demonstrated.     

Experimental infection of five species of raptors and of hooded crows with Francisella tularensis biovar palaearctica

Sixteen raptors and three hooded crows were infected experimentally with Francisella tularensis biovar palaearctica. The birds were infected parenterally or per os. One goshawk, one sparrow hawk and one hooded crow died during the experimental period, and the remaining 16 birds were killed 14-77 days after the first infection. Francisella tularensis was not isolated from any bird. Antibody levels against F. tularensis measured in nine birds varied from 0 to 1:1,280. In one goshawk with a titer of 1:1,280, positive fluorescent antibody reactions against F. tularensis were seen in the liver and spleen. These results are similar to those found by other authors indicating that raptors and corvids are normally resistant to infections with F. tularensis.     

The low-frequency EEG component in the healthy subject and its changes as affected by acutely developing foci at the level of the diencephalon and brain stem structures

The data are given of the analysis of the low-frequency EEG component (LF EEG--0.2--2.0 Hz) of 34 healthy subjects and 36 patients examined in dynamics in the acute period after operations: ablation of a tumour localized at the level of the diencephalon and the level of the brainstem. The LF EEGs were analyzed by a special program: auto- and crosscorrelation functions and power spectra were estimated. In the norm LF EEGs were characterized by mosaics, various frequencies and periodicity in various cortical areas, they appeared with interhemispheric asymmetry, depended on the EEG type--dominance or lack of the alpha-rhythm. In patients in the post-operative period the LF EEGs were changed; in favourable terminations, at first the period of oscillations and the coefficient of correlation increased, then they tended to normalization. In unfavourable terminations, with gross pathological foci in these areas, the LF EEGs acquired a synchronized character, with a higher frequency than in the norm.     

The lateralization of hemispheric control over pain-induced vocalizations in rats

Study was carried out on 232 white rats, male and female, fixed in a hammock and subjected to painful stimulation of the tail. The first impulse of pain vocalization was analyzed. The rats were divided into three groups--with intact brain, with inactivated left or right hemisphere. The first impulses of rats pain vocalizations may be divided into short screams with 40-140 ms duration and long squeals of 140-420 ms duration. Unilateral cortex inactivation led to a reduction of the latency, increase of the peak amplitude and change of the per cent both of the pain screams and pain squeals. After elimination of the left hemisphere as compared with that of the right one, a shorter latency and a greater per cent of the pain screams was observed and a smaller per cent of pain squeals. The obtained data testify to the dominance of the left hemisphere in the control of pain vocalizations in rats.     

Monoclonal antibodies localize events in the folding, assembly, and intracellular transport of the influenza virus hemagglutinin glycoprotein

We used monoclonal antibodies that recognize monomeric and/or trimeric forms of the influenza virus hemagglutinin (HA) to study biosynthesis of this integral membrane protein in influenza virus-infected cells. We find the following: First, the globular head of the HA folds into its mature conformation in the endoplasmic reticulum prior to the assembly of HA monomers into trimers. Second, trimerization begins within 1 to 2 min following synthesis, with a half-time of approximately 5 min. Third, trimerization occurs only after the HA has been transported from the endoplasmic reticulum. Fourth, newly formed trimers are sensitive to acid-induced conformational alterations associated with viral fusion activity.     

A quantitative study of enterotoxin production by sheep milk staphylococci

Of 124 staphylococcal strains isolated from sheep milk, 78 produced enterotoxin A, B, C, or D when evaluated by an enzyme-linked immunosorbent assay. Enterotoxins A and D, elaborated by 44 and 43 strains, respectively, showed the highest incidence. Enterotoxin production by coagulase-negative strains (one Staphylococcus cohnii, three S. epidermidis, five S. haemolyticus, and four S. xylosus) was detected. Linear and logarithmic-logarithmic regressions of optical density on enterotoxin concentration yielded the best-fitting equations for enterotoxin quantitation. A significantly higher incidence of enterotoxin producers and significantly higher levels of enterotoxins produced were recorded for coagulase-positive, thermostable nuclease-positive, hemolysis-positive, or mannitol-positive strains. Mannitol utilization was the best test for discriminating between enterotoxigenic and nonenterotoxigenic staphylococci.     

Characteristics of rhamnan isolated from preparations of Pseudomonas aeruginosa lipopolysaccharides

A polysaccharide isolated from the degraded lipopolysaccharides of P. aeruginosa serogroup O7 (Lányi--Bergan classification) was characterized by liquid chromatography, acid hydrolysis, and 1H and 13C NMR spectroscopy. It has molecular mass 15,000 and represents mainly a rhamnan of the structure----2)-alpha-D-Rha-(1----3)-alpha-D-Rha-(1----3)-alpha-D-Rha-(1 ----, identical to the structure of O-specific polysaccharides of Pseudomonas aeruginosa pvs morsprunorum and cerasi. Some minor constituents, such as glucose, mannose, an unknown sugar, and phosphate, are found in the polysaccharide preparation as well. Distribution of the rhamnan in some other P. aeruginosa serogroups is discussed and its identity to the common polysaccharide antigen of P. aeruginosa is suggested.     

Model studies at mechanical aortic heart valve prostheses--Part I: Steady-state flow fields and pressure loss coefficients

In a 3:1 scaled model of the human aorta models of the Omniscience, Bj?rk-Shiley Convexo-Concave, Bj?rk-Shiley Monostrut, Medtronic-Hall, Duromedics (Hemex) and the Saint Jude Medical heart valve prostheses are studied in steady flow representing the systolic peak flow phase. Detailed flow visualization experiments show flow separations at all inner ring surfaces as well as at most of the occluders. The resulting stagnation areas increase the risk of thrombus accumulation. Flow separations also stimulate vortex formation and turbulent mixing at the downstream jet boundaries and thus may intensify blood damage by turbulent shear stresses. The different influences of struts and occluder guides on the flow around the occluders are discussed. The effects of the individual valve components on the flow fields are analyzed and correlated with the resulting pressure losses.