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Biomedical subjects

E Horn

Publications and source records attributed to E Horn.

At least 91 records · Page 5Linked to original sources
PubMed1985

Recombinant DNA techniques: storage and screening of cDNA libraries with large numbers of individual colonies from initial transformations.

A typical cDNA library with a large number of initial transformants, plated in soft agarose, can be stored and shipped in 12% glycerol at -70 degrees C. To prepare the library for storage, the soft agarose layer is made into a paste and the agarose is removed by Sephadex G-25 filtration. This method of cDNA library storage does not alter the relative representation of the plasmids carried in the library. To achieve a very uniform distribution of colonies at high colony density, an aliquot of the cDNA library is diluted to 3000 to 10,000 colonies/ml. One milliliter of this suspension is evenly distributed on a nitrocellulose filter on an agar plate and air-dried. Filter copies are made and screened by published methods.

Cloning, Molecular↗
PubMed1982

The influence of ACTH fragments on habituation of the prey catching behaviour in the European toad (Bufo bufo L.).

Earlier observations on the influence of the ACTH molecule on habituation in toads revealed a capacity, which resembles the improvement of learning and memory processes in rats [6]. In the present investigation ACTH, ACTH1-10 and ACTH11-24 were tested on habituation of turning reaction, a stereotypic component of the prey catching behaviour in the European Toad, Bufo bufo L.. Furthermore the time relationship of the ACTH-effect was determined by injections at different times prior to the beginning of the habituation. ACTH as well as ACTH1-10 caused a dramatic decline in turning reactions per minute towards a prey dummy, when administered 30 min prior to habituation. Therefore, the capacity to facilitate behavioral adaptations must be located mainly in the first ten amino acids of ACTH.

Adrenocorticotropic Hormone↗
PubMed1980

Body movements and retinal pattern displacements while approaching a stationary object in the walking fly, Calliphora erythrocephala.

When a walking fly approaches a stationary object two types of body movements are distinguishable. Type I body movements are characterized by low frequencies (0.4-1.3 Hz) and large amplitudes (28-65 degrees). Superimposed on these movements are type II body movements which are characterized by high frequencies (7.3-10.6 Hz) and small amplitudes (5.9-8.2 degrees) (Figs. 3-6; Table 1). Type II movements occur no matter whether the fly is fixating a pattern or orientating itself in homogeneous surroundings without any pattern. In contrast, only 72% of the flies with immobilized heads and 62% of the flies with movable heads make type I body movements. The amplitude of type I and type II body movements increases slightly after immobilization of the head. Binocular as well as monocular pattern projection occurs for the whole walking trajectory (Fig. 7-9). Monocular pattern projection seems to be more frequent in flies with immobilized heads than in those with movable heads. The degree of pattern fluctuations in the visual field of the flies increases slightly along the walking trajectory. Near the starting point in the centre of the arena it amounts to 5-7 degrees, while at the end of the walking trajectory it amounts to 8-10 degrees (Table 2). The following conclusions and hypothesis can be drawn from these experiments. 1. The graph BT for the direction of the fly's longitudinal axis can be approximated by the first derivative of the walking trajectory WT, that means, dWT(x)dx approximately BT(x) (Fig. 11) 2. The amplitudes of type II body movements are caused by the alternating movements of the legs during forward motion, while type I body movements are classified as exploring movements. During evolution of visually guided behaviour it is possible that blowflies have adapted their elementary movement detector system to type II body movements. 3. The types of pattern projection into the visual field of the fly while approaching an object can be explained by a simple neuronal network characterized by either inhibitory and/or excitatory influences of the visually activated neurones on the motor neurones generating the propulsive forces, that means the forward motion. In addition it is postulated that the large frontal and antero-lateral receptive fields of these neurones are not coupled with the motor centres on the same side of the body (Fig 12).

Animals↗
PubMed1980

Perforation of the stomach due to trichlorofluoromethane (Freon 11) ingestion.

Accidental ingestion of trichlorofluoromethane (Freon 11) by a healthy adult male resulted in necrosis and multiple perforations of the stomach. The patient recovered after surgical intervention, the excision of necrotic tissue and the reestablishment of gastrointestinal continuity. The freezing action of Freon 11 is postulated as the cause of tissue necrosis.

Adult↗
PubMed1978

The mechanism of object fixation and its relation to spontaneous pattern preferences in Drosophila melanogaster.

The orientation behavior of walking flies, Drosophila melanogaster, towards a single 6 degrees wide black vertical stripe (elementary stripe) can be explained by use of the turning tendency function H(beta). This function is characterized by maximal values at an angular distance of beta = 25 degrees from the stable zero position (= orienting direction), a sharp decline from this maximum to beta = 60 degrees, and a very slow approach to the unstable zero position (Horn and Wehner, 1975). The shape of this function is influenced by both translatory and rotatory components of movement. If the translatory component is minimized by measuring the turning function W(beta) (see 2.3) at a distance of 10 mm (C1) from the center of the arena, a change in the strength of this decline is caused. But with increasing translatory component, i.e. at a greater distance from the center of the arena, W(beta) approximates the heuristical function H(beta) (Fig. 12). The turning functions W(beta) are pattern-specific; the angular positions of the maximum responses shift to greater angles with increasing width of the patterns (Fig. 2). In the two-pattern configuration with double or single stripes, there is always a coincidence between the stable zero positions of Wsigma(beta), the mean of the frequency distributions P(beta) of the flies' positions and ng(beta) of the straight courses, and the stable zero positions of Hsigma(beta) obtained from an additive superposition of two or more angular shifted turning tendency functions H(beta) (Fig. 5, 7). Therefore, the mean positions of the flies in a multi-stripe experiment composed of elementary stripes can be predicted from the addition of many angular shifted turning tendency functions H(beta). Between H(beta) and the frequency distribution P(beta) of the flies' positions beta, the following formula holds: P(beta) = C.intregal of H(beta)dbeta (Fig. 13). With this equation, the spontaneous preference of the broader of two double stripes can be explained presuming lateral interactions between the components of the patterns (Fig. 8, 10). The strength chii of this lateral interaction depends on the width delta of the double stripes. The greater delta, the smaller is chii. chii is a pattern-specific value (Table 1, 2).

Animals↗
PubMed1978

Fixation-sensitive areas in the eyes of the walking fly, Calliphora erythrocephala.

In Calliphora erythrocephala the visual fixation behaviour in one-eyed flies and partial blinded flies has been investigated. One-eyed flies show approximately the same stripe and edge fixation response as intact flies. Elimination of the frontal eye parts including the binocular field of vision does not effect the visual stripe fixation. On the other hand, if only the frontal areas of both eyes including the binocular field of vision are left open, no preferential direction can be observed (Fig. 1--3). The results imply the existence of a fixation-sensitive area of the eye located outside the binocular field of vision.

Animals↗