The influence of display characteristics on active pursuit and passively induced eye movements

Summary A series of experiments has been conducted on human subjects to examine the effect of the movement of small targets located in the peripheral visual field on oculomotor response. Subjects were presented with either a single centrally positioned target or a pair of targets displaced at angles of ±5°, ±10° and ±20° from centre. Target movement was in the horizontal plane, the paired targets always moving in unison. The stimulus waveform consisted of either a sinusoidal or random target motion encompassing a frequency range from 0.1 to 4 Hz with an angular displacement of ±3.5°. Subjects made two types of response. First they were instructed to follow the single target or the centre point of the paired targets. In this active pursuit condition the gain of slow-phase eye velocity progressively decreased as the moving targets were moved from the central position to the most peripheral location (±20°). Secondly, subjects were required passively to ignore the target movement by staring blankly ahead. During this passive response nystagmic eye movements were induced for which the slowphase eye velocity also decreased with increasing target eccentricity, but the gains were always less than those induced during active pursuit. The frequency characteristics of the passive response were very similar to those of the active response, breaking down at frequencies beyond 1 Hz. The ability to suppress the passive response was also investigated by the presentation of a tachistoscopically illuminated earth-fixed target. The response was found to decline as the interval between presentations of the fixation target was decreased from 3000 ms to 100 ms. It is suggested that the passive response originates from a basic velocity drive to the oculomotor system resulting from image movement across the retina. This velocity drive may be cancelled with adequate fixation but must be enhanced to accomplish desired eye velocity during active pursuit.     

Lichtmikroskopische Untersuchungen über die Entwicklung vonTheileria annulata (Dschunkowsky und Luhs, 1904) inHyalomma anatolicum excavatum (Koch, 1844)

Summary Fully differentiated kinetes, average length 17.6m, appeared in the haemolymph of engorged nymphs usually 17 to 20 days after repletion. Kinetes were observed at first in the salivary glands on day 18 after repletion. The kinetes then transformed into fission bodies of about 10m in diameter, mainly in type III alveoli and less frequently in type II alveoli. The fission bodies grew up to a size of about 20m after several divisions of their nucleus. At this time the ticks moulted and no further development occurred until activation. Shortly before infestation the salivary glands began to proliferate, and rapid growth of the fission bodies was observed, especially in young ticks where development of infective particles (sporozoites) was concluded within two days. Development in feeding adult ticks apparently occurred in four major steps: (1) Division of primary fission bodies (sporonts) into numerous secondary fission bodies (primary sporoblasts), (2) division of secondary fission bodies into tertiary fission bodies (secondary sporoblasts), (3) production of particles (sporozoites) by tertiary fission bodies and release of particles into the saliva, and (4) degeneration of fission bodies and their host cell but further release of particles.The host cell was stimulated to giant growth, thus its diameter increased, on average, from 15 to 110 m. Heavy infections resulting from parasitaemias of >40% caused disease and mortality in the tick population. Development was much retarded by aging. In ticks starved for six months sporozoites did not develop before day five to seven of infestation. Sporozoites may not develop at all in six to nine month old female ticks during the infestation period. The significance of the described developmental stages ofT. annulata was discussed and a sexual generation postulated. The hypothetic development ofT. annulata in its tick vector was illustrated.

---

---

Gefördert von der Deutschen Forschungsgemeinschaft (DFG)     

Spatial relationship of nebulin relative to other myofibrillar proteins during myogenesis in embryonic chick skeletal muscle cellsin vitro

Summary The developmental expression of nebulin was studied in embryonic chick skeletal muscle cellsin vitro by means of immunofluorescence microscopy. Initially nebulin appeared homogeneously or in a punctate form in the cytoplasm, and then it was assembled into I-Z-I-like complexes containing actin and-actinin but not myosin and connectin (titin). Striated patterns of nebulin (singlets) in myofibrils appeared simultaneously with those of-actinin (Z-bands), myosin (A-bands) and connectin (doublets), but earlier than those of actin. After actin striations were formed as myofibrils matured, each nebulin band started to exhibit droplets. The delayed development of nebulin compared to the I-Z-I brush formation and the myofibril maturation seems to indicate that this giant myofibrillar protein is unnecessary for both the initial (formation of I-Z-I-like structures) and the subsequent (regular alignment of myofibrils) phases of myofibrillogenesis.     

An in vitro model to study myocardial ischemic injury

Summary This report describes a method to study ischemic and reperfusion damage in cultured ventricular cardiomyocytes. The cardiomyocytes were made ischemic by oxygen deprivation and volume restriction. The ischemic intervals studied were 60, 90, and 120 min. An oxygen tension of 0 mmHg was maintained throughout ischemia. Reperfusion was simulated by bathing the cells in a large volume of normally oxygenated PBSG following ischemia. Ischemia and reperfusion resulted in increased lactate production, increased membrane damage, and ATP degradation. Ischemia caused a decrease in pH. Although 90 min of ischemia caused cell structural changes and alteration of metabolism, a prolonged ischemic interval of 120 min exacerbated these abnormalities. We have found our in vitro ischemia and reperfusion model to closely mimic the in vivo condition. This model using human ventricular cardiomyocytes is a means to studying the effect and mechanism of ischemia and reperfusion at the cellular level under defined conditions.     

Oligoclonal interspecific origin of ‘North Indian’ and ‘Chinese’ sugarcanes

Sugarcanes consist of several groups of complex polyploid forms. The origin of North Indian and Chinese sugarcanes (referred to as S. barberi and S. sinense) was investigated using genomic in-situ hybridization (GISH), detection of species-specific repeated sequences and RFLP. GISH proved their interspecific hybrid origin. Together with the distribution of species-specific repeated sequences and earlier RFLP data, the results show that both taxa are derived from interspecific hybridization between S. officinarum and S. spontaneum and that no other genus has been directly involved. RFLP indicates that the clones are clustered into a few groups, each derived from a single interspecific hybrid that has subsequently undergone a few somatic mutations. These groups correspond quite well with those already defined based on morphological characters and chromosome numbers. However, the calculated genetic similarities do not support the existence of two distinct taxa. The North Indian and Chinese sugarcanes represent a set of horticultural groups rather than established species.     

Use of girth measurements for estimating body volume and body density in Indian girls aged 10–19 years

Summary Mean values and standard deviations of total body volume, body density, height, weight, and a battery of 20 girth measurements of 200 Punjabi girls aged 10–19 years are presented. Selective stepwise multiple regression equations for predicting total body volume and body density from girth measurements are also given for different age groups.Hip girth was the most commonly selected measurement at the first step in most age groups and the values of r between hip girth and total body volume ranged between 0.86–0.96 in different age groups. The values of multiple R between total body volume and a combination of first four selected girth measurements varied from 0.96–0.99 in different age groups.The values of multiple R between body density and a combination of four girth measurements selected up to fourth step ranged between 0.73–0.92 in different age groups.     

The tubular vacuolation process in amphibian skeletal muscle

The exposure of amphibian muscle to osmotic shock through the introduction and subsequent withdrawal of extracellular glycerol causes vacuolation in the transverse tubules. Such manoeuvres can also electrically isolate the transverse tubules from the surface (detubulation), particularly if followed by exposures to high extracellular [Ca2+] and/or gradual cooling. This study explored factors influencing vacuolation in Rana temporaria sartorius muscle. Vacuole formation was detected using phase contrast microscopy and through the trapping or otherwise of lissamine rhodamine dye fluorescence within such vacuoles. The preparations were also examined using electron microscopy, for penetration into the transverse tubules and tubular vacuoles of extracellular horseradish peroxidase introduced following the osmotic procedures. These comparisons distinguished for the first time two types of vacuole, open and closed, whose lumina were respectively continuous with or detached from the remaining extracellular space. The vacuoles formed close to and between the Z-lines, but subsequently elongated along the longitudinal axis of the muscle fibres. This suggested an involvement of tubular membrane material; the latter appeared particularly concentrated around such Z-lines in the electron-micrograph stereopairs of thick longitudinal sections. Open vacuoles formed following osmotic shock produced by extracellular glycerol withdrawal from a glycerol-loaded fibre at a stage when one would expect a net water entry to the intracellular space. This suggests that vacuole formation requires active fluid transport into the tubular lumina in response to fibre swelling. Closed vacuoles only formed when the muscle was subsequently exposed to high extracellular [Ca2+] and/or gradual cooling following the initial osmotic shock. Their densities were similar to those shown by open vacuoles in preparations not so treated, suggesting that both vacuole types resulted from a single process initiated by glycerol withdrawal. However, vacuole closure took place well after formation of open vacuoles, over 25 min after glycerol withdrawal. Its time course closely paralleled the development of detubulation reported recently. It was irreversible, in contrast to the reversibility of open vacuole formation. These findings identify electrophysiological detubulation of striated muscle with closure of initially open vacuoles. The reversible formation of open vacuoles is compatible with some normal membrane responses to some physiological stresses such as fatigue, whereas irreversible formation of closed vacuoles might only be expected in pathological situations as in dystrophic muscle.This revised version was published online in September 2005 with corrections to the Cover Date.     

Macrophage inflammatory protein-1 alpha expression in non-neoplastic and neoplastic lung tissue

The chemokines are members of a bipartite superfamily of soluble proteins that have been implicated in a wide range of acute and chronic inflammatory processes, as well as other immunoregulatory functions. Macrophage inflammatory protein-1 alpha (MIP-1) belongs to the C-C subfamily of these chemokines and is primarily a potent chemoattractant and activator of monocytes. MIP-1 is also thought to play a role in host defence. We examined the expression of MIP-1 in normal lung, inflammatory lung tissue and lung cancer cells by the immunoperoxidase method using a MIP-1 monoclonal antibody. MIP-1 protein was found to be expressed not only by alveolar macrophages, but also by bronchial ciliated cells, hyperplastic alveolar type II cells and activated fibroblasts surrounding malignant tissue. Of 33 cases of lung cancer, 23 (70%) expressed MIP-1. These observations suggest that lung cancer cells, non-neoplastic alveolar type II cells and fibroblasts can participate in inflammatory cell recruitment via the production of MIP-1. Tumour derived MIP- may also affect the interaction between lung cancer and host inflammatory cells.     

Synergistic effects of tumour necrosis factor-α and interferon-γ on feline haemopoietic progenitors

Pathogenic mechanisms that underlie feline leukaemia virus subgroup-C (FeLV-C) induced erythroid aplasia are unknown. FeLV-C infection is associated with higher serum levels of interferon- (IFN-) and tumour necrosis factor- (TNF-), which may act synergistically to cause haemopoietic suppression. In the present studies, the synergistic effects of TNF- and IFN- on feline bone marrow progenitors in vitro were evaluated. Bone marrow mononuclear cells from specific-pathogen-free cats were exposed to TNF- (100 and 200 pg/ml) and IFN- (100 or 200 units/ml), alone or in combination, for 2 h before plating for clonal assays of colony forming units. Our results show that TNF- and IFN- in combination caused marked suppression of feline colony forming units-erythroid (CFU-E), burst forming units-erythroid (BFU-E), and colony forming units-fibroblasts (CFU-F), whereas colony forming units-granulocyte/macrophage (CFU-GM) were minimally affected. The same concentrations of TNF- and IFN- alone had minimal effects on CFU-E, BFU-E and CFU-F. These results suggest that TNF- and IFN- may play a significant role in regulating haemopoiesis in cats and may be involved in the pathogenesis of erythroid aplasia in cats infected with feline leukaemia virus.     

Do ‘evaluation potentials’ reflect cognitive assessment?

Summary Event-related potentials were recorded when a subject evaluated the outcome of a simple TV game as successful/unsuccessful, where the goal was specified randomly as one of two areas on the screen. The evaluation potential elicited by the outcome was consistently larger for unsuccessful outcomes, regardless of the location of the goal.