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Biomedical subjects

G Horn

Publications and source records attributed to G Horn.

At least 91 records · Page 5Linked to original sources
PubMed1987

Nonisotopic M13 probes for detecting the beta-globin gene: application to diagnosis of sickle cell anemia.

M13 DNA probes labeled with biotinylated psoralen and a streptavidin-horseradish peroxidase conjugate provide nonradioactive detection of the sickle cell and normal alleles of the beta-globin locus. The two biotinylated probes contain single-stranded sequences complementary to two different Sau3AI restriction fragments from the 5' region of the beta-globin gene and double-stranded M13 vector sequences. These probes are labeled with biotinylated psoralen photochemically linked to DNA. After hybridization, the presence of biotinylated probe bound to target DNA is detected in 3 h by using a streptavidin-horseradish peroxidase conjugate and the substrate, 3,3',5,5'-tetramethylbenzidine. Digestion of the normal (beta A) allele of the beta-globin gene with MstII (or isoschizomers) yields a 1.14-kb restriction fragment, while digestion of the mutant beta S allele yields a 1.34-kb fragment. These fragments can be resolved by gel electrophoresis and detected by Southern blot hybridization. The nonradioisotopic probe system can detect the beta-globin restriction fragment in as little as 0.5 microgram of human DNA and can distinguish heterozygotes (beta A beta S) from homozygotes (beta A beta A or beta S beta S) in 2.0 micrograms of human DNA.

Alleles↗
PubMed1987

Hydrogen breath test in small intestinal malabsorption.

Jejunal biopsy and hydrogen breath test were performed in 57 children, 34 having coeliac disease and 23 with other forms of malabsorption. In children affected by coeliac disease there was a gradually increasing incidence of positive findings with the H2 breath test as villous damage progressed. In the group of subtotal villous atrophy age dependence was also observed, the majority of positive results occurring below three years of age. In the non-coeliac group the most frequent cause of the positive finding was Giardia lamblia infestation. Among 27 cases with lactose malabsorption confirmed by a positive hydrogen breath test only 11 had diarrhoea. The test proved to be useful in differentiating between the contaminated intestine syndrome and malabsorption due to reduced absorptive surface.

Adolescent↗
PubMed1986

Dissociation of recognition memory and associative learning by a restricted lesion of the chick forebrain.

Bilateral lesions of a restricted part of the chick forebrain (IMHV) have been shown to impair the acquisition and retention of imprinting preferences. The present study sought to determine the effects of such lesions on an operant conditioning task in which the reward was the presentation of one of two conspicuous objects, a stuffed jungle fowl or an illuminated red box. Twelve hours after hatching 28 domestic chicks received bilateral lesions of IMHV. Thirty-two chicks served as sham-operated controls. On the following day all birds underwent two sessions of operant training. After the second session the chicks were given a preference test. In this test the reinforcing object (box or fowl) and a novel object (fowl or box, whichever had not been seen before) were simultaneously presented. One test was given 2 hr and a second 24 hr after the termination of the operant task. The lesioned birds were not impaired on the operant task or on measures of general activity. In contrast, these birds failed to show a preference for the reinforcing object whereas the sham-operated controls strongly preferred this object. These results suggest that object recognition and associative learning can be dissociated in young chicks. This dissociation is reminiscent of certain human amnesias. The lesion did not impair an expected increase in preference for the stuffed fowl which developed in all birds between the 2-hr and 24-hr preference tests.

Animals↗
PubMed1986

Androgens and imprinting: differential effects of testosterone on filial preference in the domestic chick.

The relation between testosterone and imprinting was investigated in domestic chicks. After hatching, chicks received either testosterone enanthate in oil or oil alone (controls). The chicks were then trained by exposing them to a rotating imprinting stimulus, either a red box or a stuffed jungle fowl. A preference score was then determined, providing a measure of the strength of imprinting. Plasma testosterone concentration after testing did not differ significantly between males and females and was unaffected by the type of training stimulus. In fowl-trained chicks, but not in box-trained chicks, preference score was positively correlated with plasma testosterone concentration. Furthermore, the mean preference score of the fowl-trained chicks that had received exogenous testosterone was significantly higher than that of their controls; no such effect was found in box-trained chicks. A previous study showed that imprinting with the box, but not the fowl, is profoundly impaired by a noradrenergic neurotoxin. The results taken together suggest that some of the neural systems supporting the preference for the red box, a simple artificial object, are different from some of those supporting the preference for the stuffed jungle fowl.

Animals↗
PubMed1986

Imprinting, learning, and memory.

If a visually naive chick is exposed to one of a wide range of conspicuous objects, the chick may learn its characteristics. A series of biochemical studies has implicated a restricted part of the forebrain in this process of imprinting; a specific region (IMHV) has been identified which may be a site of information storage. Changes in the morphology of synapses occur in this region as a consequence of training. The left and right IMHV regions play different roles in the imprinting process. Exposure to a simple artificial object, a rotating red box, has different neural consequences from those associated with exposure to a complex object, a rotating stuffed jungle fowl, which resembles a conspecific. These differences may be related to the differences in complexity of the two training objects. Another possibility is that two neural systems are implicated in imprinting: a system that underlies a predisposition to approach objects resembling conspecifics and a learning system, of which IMHV is a crucial component, that is engaged by particular objects and that in "natural" circumstances also allows the chick to learn the characteristics of its mother.

Animals↗
PubMed1986

Mast cell degranulation after a single dose of gliadin in the jejunum of patients with coeliac disease.

The exact pathomechanism of jejunal damage caused by gliadin in coeliac disease has not been clarified. 0.3 g of gluten per kg bodyweight was administered to 14 children affected by coeliac disease, being on gluten-free diet, five hours before jejunal biopsy. There was no change in the number of intraepithelial lymphocytes and eosinophils while cellular infiltration of the lamina propria exhibited a marked increase and the number of mast-cells per tissue unit significantly decreased as compared with controls. It is concluded that mast-cells may play an important role in the mechanism of gluten induced jejunal damage.

Adolescent↗
PubMed1986

[The synthesis and biologic activity of analogs of 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone. 2. Substitution at the quinone ring by alkyl groups].

Because of the anticancer activity of 1,4-benzoquinone-guanylhydrazone-thiosemicarbazone (1a) some analogues were synthesized, containing alkyl groups at the quinone moiety. If necessary, the structure of the obtained compounds was confirmed by 1H-NMR-spectroscopy. The anticancer and the antibacterial activities were investigated. The guanylhydrazone-thiosemicarbazones of tolu-,p-xylo-and thymo-quinone showed much lower activities not only against the murine leukemias L 1210 and P 388, but also against Bacillus subtilis ATCC 6633. No correlation could be found between the biological activity and the redox potential.

Animals↗
PubMed1985

Effects of early experience on the development of filial preferences in the domestic chick.

Factors affecting the development of filial preferences in chicks were investigated. Four groups of chicks were hatched and maintained in darkness. When the chicks were 20-hr old, three of these groups were exposed to an overhead light ("primed") for .5 h. When 24-hr old, all groups were placed in running wheels for 2 hr. While in the wheels one group was exposed to a visually complex pattern, one group to diffuse overhead light, and the remaining two groups (one primed and one not primed) were in darkness. All chicks were then returned to a dark incubator until their preference for a red box or a stuffed jungle fowl was measured in a simultaneous choice test either 2 hr (Test I) or 24 hr (Test II) later. At Test I the chicks which had been exposed to the complex visual pattern showed a significant preference for the fowl. Chicks in the other groups showed no preference. At Test II all groups showed a significant preference for the fowl. The results of a second experiment suggested that the later emerging preference was related to the chicks experience in the running wheel. It was concluded that the preference for the fowl will develop in entirely dark-reared chicks that are allowed a period of time in a running wheel, but that this preference will appear earlier in chicks which have had experience of a complex visual pattern.

Animals↗
PubMed1985

Noradrenaline and learning: effects of the noradrenergic neurotoxin DSP4 on imprinting in the domestic chick.

The effects of the noradrenergic neurotoxin DSP4 on imprinting in domestic chicks were investigated. Chicks received either DSP4 or distilled water and were trained 60 hr after hatching by exposing them to either a rotating red box or a stuffed jungle fowl. Noradrenaline concentration was determined in Wulst and medial and basal forebrain samples. The medial forebrain sample comprised mainly the intermediate part of the medial hyperstriatum ventrale, a region previously shown to be intimately involved in imprinting. The DSP4 treatment reduced forebrain noradrenaline levels by about 65%. DSP4 profoundly impaired imprinting in box-trained chicks but not in fowl-trained chicks. In box-trained chicks, the strength of imprinting was positively correlated with noradrenaline concentration in both medial and basal forebrain samples. It is suggested on the basis of these and previous studies that some of the neural structures and mechanisms involved in imprinting on the fowl differ from those involved in imprinting on the box.

Animals↗
PubMed1985

[Pulse polarographic determination of piperacillin (Pipril) in serum and urine].

Two pulse polarographical methods for determination of the half-synthetic penicillin derivate piperacillin in serum and in urine are described. 3.7 X 10(-5) mol/l (20 micrograms/ml) can yet been proved in serum with the direct pulse polarographical determination. 1.85 X 10(-6) mol/l (1 microgram/ml) can quantitatively be determined after preceded hydrolysis. Both the methods are diffusion standards being well developed which can be evaluated in an adequate manner. The piperacillin concentrations determined by pulse polarography agree to the levels of the agar diffusion test. The precision is some reduced by the separations incorporated. Inspite of the hydrolysis, the pulse polarographical method of determination will offer more prompt and reliable results.

Chromatography, Thin Layer↗