The effect of body mass and fat reserves on the choice of the stopover place and on the stopover period was investigated in 3 species of passerine birds migrating through the Sahara in Egypt. Birds grounded in an oasis with food and water were more than 10% lighter than those from a desert stopover place which offered shade only. Stopover period was in general one day except for the light portion of oasis birds which stopped for up to three weeks during which they regained fat. A calculation of the maximum range which can be covered with the available fat depots revealed that nearly all birds from the desert stopover place should be able to cross the desert whereas about 60% of the oasis birds should not. An intermittant migratory strategy for the desert crossing is proposed with flight during the night and stopover during the day, even without drinking and feeding.

To investigate temporal changes in capillarization and increases in mitochondrial enzyme activity, rabbit tibialis anterior muscles underwent chronic low-frequency stimulation for up to 50 days. Capillary density (CD), capillary-to-fiber ratio (C/F), intercapillary distance (ICD), and mean capillary area (MCA), as well as several other parameters of capillarization, were examined. In addition, tissue levels of mRNA specific to vascular endothelial growth factor (VEGF) were assessed by reverse transcriptase-polymerase chain reaction. Citrate synthase (CS) activity, a marker of aerobic-oxidative metabolic potential, was measured in the same muscles. Significant increases in CD and C/F, respectively, and decreases in ICD and MCA were observed after 2 days. These changes reached stable maxima by 14 days. The increases in capillarization occurred in a fiber-type-specific manner, affecting type IId fibers before types IIda and IIa. VEGF mRNA levels increased in a bimodal time pattern with a first elevation (2.5-fold) after 1 day and a second (9-fold) after 6–8 days. Increases in CS were first noted after 8 days. Obviously, increases in capillarization as induced by enhanced contractile activity precede increases in the aerobic-oxidative potential of energy metabolism.

Radar observations of the diurnal timing of bird migration in the Sahara Desert are presented for autumn migration. Study sites were on a transect along the north-south migratory direction. Three groups of birds migrating either during day, evening or night in the northern part of the Western desert in Egypt were identified. The maximum of day and night groups occurred later the further south the study sites were. Based on the distance between sites and the timing of peak migration, birds were flying at an estimated ground speed of about 20 m/s. The maximum of the evening group was at about 2 1 :00 h at all sites. The three groups were classified according to three different strategies of migration across the Mediterranean Sea and the Sahara Desert: (1) the day group of birds performed a non-stop flight across the sea and at least the northern part of the desert;(2) the night group performed an intermittent migratory strategy with stopover at the coast of Egypt to continue migration the next evening; (3) the evening group birds were also intermittent migratory fliers, but they stopped somewhere in the desert after a continuous flight across the sea and part of the desert. About 20% of all migrants are involved in non-stop migration and 80% in intermittent migration with stopover at the coast (7OYo) or with stopover in the desert (10%). It is argued that any species of small passerine has the option to use any of the three strategies.

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In contrast to terrestrial ecology, three-dimensional (3-D) imaging technology is not well established as a method for studying species-habitat interactions in aquatic ecology. In this study, we used a semi-portable, digital, 3-D underwater observatory designed for long-term exposure in shallow water habitats to assess fish-habitat interactions to artificial structures of different complexity. The observatory was mounted on a cable-car system and was moved along a 50 m transect parallel to five artificial structures of different complexity and one control site. The optical unit took high-resolution digital images, in pairs, from each structure and the control site at a frequency of 30 min over 24 h and was then moved remotely to the next structure. The system was operated for 2 mo without being recovered and took a total of 2160 stereoscopic image pairs. The system proved highly valuable in assessing small-scale temporal patterns in fish-habitat interactions, as well as changes in habitat preferences of fish over the diel cycle. Such small-scale temporal and spatial patterns are important for a detailed understanding of specieshabitat interactions, not only in fish but also in most aquatic macro-organisms. Nevertheless, such patterns can hardly be assessed using classical sampling devices due to labor and animal protection restrictions. However, the possibility of a significant increase in quantity of sampling through the use of remote imaging technology is accompanied by a significant increase in labor costs for image analysis. Therefore, further progress in semi-and fully automated systems for image analysis is needed, including 3-D imaging tools, for ecological studies.

This study investigates early adaptive responses of fast-twitch muscle to increased contractile activity by low-frequency stimulation. Changes in metabolite levels and activities of regulatory enzymes of carbohydrate metabolism were investigated in rabbit tibialis anterior muscle after 24 h of stimulation. In addition, changes elicited during a 5-min lasting acute stimulation experiment were compared between 24-h-prestimulated and contralateral control muscles. Stimulation for 5 min reduced energy-rich phosphates and glycogen, and increased lactate in the control muscle. A transient elevation of fructose 2,6-bisphosphate demonstrated that activation of phosphofructokinase 2 was an immediate response to contractile activity. Prestimulated muscles displayed nearly normal values for ATP, phosphocreatine and glycogen, and did not augment lactate. Increased activities of hexokinase and phosphofructokinase 2 and permanently elevated levels of fructose 2,6-bisphosphate pointed to enhanced glycolysis with glucose as the main fuel in the prestimulated muscle. Isometric tension of the control muscle decreased rapidly a few minutes after the onset of stimulation. In the prestimulated muscles, tension was almost stable, but amounted to only 30%-40% of the initial tension of the control muscle. In view of the fibre type distribution of rabbit tibialis anterior, these findings suggested that a large fibre fraction of the prestimulated muscle, possibly the glycolytic type IID fibres, did not contract. Therefore, the possibility must be considered that the metabolite pattern of the 24-h-stimulated muscle primarily reflected metabolic activities of the contracting, less fatigable fibres, most likely type IIA and type I fibres.(ABSTRACT TRUNCATED AT 250 WORDS)

Objectives: Although chest CT has been widely used in patients with COVID-19, its role for early diagnosis of COVID-19 is unclear. We report the diagnostic performance of chest CT using structured reporting in a routine clinical setting during the early phase of the epidemic in Germany. Methods: Patients with clinical suspicion of COVID-19 and moderate-to-severe symptoms were included in this retrospective study. CTs were performed and reported before RT-PCR results (reference standard) became available. A structured reporting system was used that concluded in a recently described five-grade score (“CO-RADS”), indicating the level of suspicion for pulmonary involvement of COVID-19 from 1 = very low to 5 = very high. Structured reporting was performed by three Radiologists in consensus. Results: In 96 consecutive patients (50 male, mean age 64), RT-PCR was positive in 20 (21%) cases. CT features significantly more common in RT-PCR-positive patients were ground-glass opacities as dominant feature, crazy paving, hazy margins of opacities, and multifocal bilateral distribution (p < 0.05). Using a cut-off point between CO-RADS 3 and 4, sensitivity was 90%, specificity 91%, positive predictive value 72%, negative predictive value 97%, and accuracy 91%. ROC analysis showed an AUC of 0.938. Conclusions: Structured reporting of chest CT with a five-grade scale provided accurate diagnosis of COVID-19. Its use was feasible and helpful in clinical routine. Advances in knowledge: Chest CT with structured reporting may be a provisional diagnostic alternative to RT-PCR testing for early diagnosis of COVID-19, especially when RT-PCR results are delayed or test capacities are limited.

The temporal pattern of migration by passerine birds during the night, and their arrival during the day at the Egyptian coast and in the northern Sahara Desert was investigated. The mean direction of nocturnal migration at the coast was south-southeast, while at all desert sites it was south-southwest.Birds arrived at the Egyptian coast only during the second half of the night which is explained by the fact that n o birds could have taken off from the Mediterranean Sea. At least some of the birds landed at the coast where they spent the day before taking off shortly after sunset. These birds passed the desert sites at the expected time of day assuming a ground speed of 18 m per second. However, the origin of the birds passing the desert sites early a t night is unclear. They must either have spent the day in the desert north of the study sites or they had overflown the Egyptian coast in the afternoon without landing.The landing of birds during the day a t the desert sites was bimodal. This pattern of arrival is explained either by some birds having landed a t the Egyptian coast in the early morning before continuing, or by deteriorating conditions later in the day during flight or when resting in the desert, that obliged them to seek shelter at the desert sites.A correlation between the number of migrants observed during the night and the number of resting birds in the desert on the following day suggests that an unknown proportion of birds might regularly use an intermittent migratory strategy that includes rest periods by day when crossing the desert, whereas others might adapt a non-stop migratory strategy.In Europe, many migrating bird species, especially longdistance migrants, are known to migrate exclusively during the night (Dorka 1966). A number of ultimate factors have been proposed to explain this behaviour, most prominently the possibility of feeding during daylight and the avoidance of predators during the day (Palmgren 1936). better temperature regulation and water balance (Dorka 1966) and the calm atmospheric conditions that prevail at night (Kerlinger & Moore 1989). Knowledge of the temporal pattern of migratory behaviour under extreme conditions, such as a desert crossing, might give further insight into the adaptive significance of the general phenomenon of nocturnal migration. In addition it might suggest physiological constraints that limit migration.Two strategies for crossing deserts have been proposed: a non-stop migratory strategy with flight during day and night (Moreau 1961) and an intermittent migratory strategy with flight during the night and rest during the day (Biebach