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Biomedical subjects

G Horn

Publications and source records attributed to G Horn.

At least 73 records · Page 4Linked to original sources
PubMed1990

Neural bases of recognition memory investigated through an analysis of imprinting.

Through a learning process known as imprinting, the young of some animals, including the domestic chick, come to recognize an object by being exposed to it. Visually naive chicks vigorously approach a wide range of objects. After an adequate period of exposure to one object chicks selectively approach it in a recognition test. The nervous system of dark-reared chicks is not a tabula rasa, as chicks have predispositions to approach some stimuli rather than others. Nevertheless, visual imprinting leads to changes in a nervous system that may not have been 'marked' by previous visual experience, and so encourages the hope of discovering the neural bases of the learning process. The intermediate and medial part of the hyperstriatum ventrale, a sheet of cells within the cerebral hemispheres, plays a crucial role in visual imprinting, particularly in the memory process of recognition. The cellular and sub-cellular changes that take place in this part of the hyperstriatum ventrale after imprinting are described. The right and left hyperstriatum ventrale regions play different roles in the imprinting process, and evidence is given for the existence of multiple memory systems in the chick brain.

Animals↗
PubMed1990

[The value of the d-xylose loading test in the diagnosis of malabsorption syndromes].

The test of d-xylose concentration in blood has been used for approximately two decades for the examination of the absorption. The authors compared in 261 cases the total d-xylose blood level with the histological picture of the small intestine. Good correlation was observed between the 2 examinations. The d-xylose loading was found to select with favorable efficacy the new cases of celiac disease, of 63 fresh diagnosed subtotal and total villus atrophy cases the blood level of 61 was under the 1,64 mmol/l limit. At the 3rd stage of partial villus atrophy the blood level was pathological in 17 new patients. The sensitivity of the examination was 92.2% in selection of the new cases. Significant differences were found between the new cases and patients with excess gliadin (0.929 +/- 0.44 mmol/l and 1383 +/- 0.052 mmol/l) with identical rate of duodenal tissue impairments. On this basis the significant decrease of d-xylose level (0.5-1 mmol/l) must be regarded as the sign of relapse in patients with excess gliadin. Giardia lamblia and slight villus impairment was found in the biopsy material of further 28 children. The d-xylose level was pathological in 14 of them. D-xylose absorption was pathological before treatment in each of the 13 patients with contaminated (Gram-negative aerobic bacteria) small intestinal syndrome. D-xylose test is a useful method in the diagnostics of conditions associated with malabsorption and completed with other techniques it provides means for the separation of conditions associated with the diffuse impairment of the small intestine.

Celiac Disease↗
PubMed1990

[Contaminated small bowel syndrome in infants caused by gram-negative bacteria and yeasts].

The upper small intestine is usually "sterile" in a healthy individuals, but due to some reasons the number of microorganisms may reach or increase above 10(4)/ml, leading to the contamination of the small intestine, which may cause severe malabsorption. The authors have diagnosed this syndrome in 50 children, aged between 1 month and 3 years, using breath hydrogen test and duodenal juice culture. Most of these children had growth retardation. According to their experience the authors found that the oral antibiotic is the effective treatment of this syndrome.

Anti-Bacterial Agents↗
PubMed1990

[Incidence of lactose malabsorption in the population 6-18 years of age].

Breath test was performed in 664 school-aged children in order to measure lactose malabsorption. The first screening showed that 23.4% of the children evidenced malabsorption of milk sugar. In these children further stool examination for Giardia lamblia infection, and saccharose breath test was performed to identify more complex absorption problems. The remaining 146 children were tested again after a period of 3-9 month and 45.8% of this population showed lactose malabsorption. In conclusion the authors determined that 10.1% of school aged children were permanently hypo- or alactasic. During the examination, they measured the approximate consumption of milk considering the quantity of milk intake showed that the consumption of milk and lactose malabsorption were not closely related normal and abnormal absorption among children who would not normally consume milk.

Adolescent↗
PubMed1990

Are specific proteins implicated in the learning process of imprinting?

Day-old chicks were exposed for 0.5 h to overhead lighting ('primed') and then imprinted by exposing them for 90 min to a rotating red box. The chicks were otherwise maintained in darkness. Immediately after training these chicks (n = 16), together with 16 primed and 16 dark-reared controls were killed. Samples from the left cerebral hemisphere were removed including (i) the intermediate and medial part of the hyperstriatum ventrale (IMHV), a region which is crucial for imprinting, (ii) the posterior neostriatum and (iii) the visual Wulst. The samples were incubated with [35S]methionine, processed for SDS slab gel electrophoresis and autoradiographs prepared. The optical densities of various bands were measured 'blind'. For no band was there a significant interaction (ANOVA) between brain region and experience. Optical density was correlated with approach activity during training, a measure of behaviour which correlates with the amount chicks learn. Only for IMHV were correlations significant: a negative correlation (P less than 0.01) for approximately 50 kDa band and positive correlation (P less than 0.001) for an approximately 80 kDa band. These results suggest that associated with training there is a reduction and an increase in the synthesis of proteins in IMHV.

Animals↗
PubMed1990

New refractive method for laser thermal keratoplasty with the Co:MgF2 laser.

We have observed corneal curvature changes from laser thermal keratoplasty with a Co:MgF2 laser. We studied corneal curvature changes in rabbits and have identified specific treatment patterns and laser parameters that can correct myopia and astigmatism. These corneal changes, some as large as 8 diopters, have been stable for at least one year, and slitlamp examination demonstrates clear central corneas with normal appearance.

Animals↗
PubMed1989

Molecular genetic analysis of 178 I-Abm12-reactive T cells.

We have studied the genetic diversity of the TCR repertoire to the murine alloantigen I-Abm12 by generating a panel of 178 C57BL/10-derived I-Abm12-reactive T cell hybridomas. The expression of V alpha and V beta gene families was examined in this panel and the frequency of expression of V beta, but not ofV alpha, gene families differed significantly from that observed in a companion panel of random C57BL/10-derived hybridomas. The V beta 5 gene family was expressed significantly less frequently while the V beta 14, V beta 15, and V beta 16 genes were expressed significantly more frequently in the panel of I-Abm12-reactive than in the panel of random hybridomas. The junctional regions (VJ alpha and VDJ beta) of TCR V alpha and V beta genes from selected I-Abm12-specific hybridomas were amplified using the polymerase chain reaction, and directly sequenced. Surprisingly, no conserved J alpha, D beta, J beta, or N region-encoded sequences among these selected I-Abm12-reactive TCRs were identified. Thus, the T cell response to an I-A alloantigen that differs by only three amino acid residues from the I-A molecule of the responding strain is genetically complex but nonrandom. We have estimated that the repertoire to this alloantigen is comprised of at least 37 different TCRs.

Amino Acid Sequence↗
PubMed1989

Memory systems in the chick: dissociations and neuronal analysis.

Young domestic chicks learn to recognize the visual characteristics of an object to which they are exposed. A restricted part of the forebrain, the intermediate and medial part of the hyperstriatum ventrale (IMHV) is implicated in this process. This form of exposure learning can be dissociated from (i) the ability to learn certain procedures or skills, and (ii) a predisposition to attend to particular types of naturalistic objects. The first of these dissociations is reminiscent of that found in certain human organic amnesias, whilst the second may have its counterpart in the processes involved in face recognition by infants. The right and left IMHV play different roles in the memory that underlies imprinting. The cellular and molecular processes involved in this form of memory are discussed.

Animals↗
PubMed1989

Intestinal mast cells and neutrophil chemotactic activity of serum following a single challenge with gluten in celiac children on a gluten-free diet.

The number of one subtype of mast cells (formalin fixation, toluidine blue staining), cells of the lamina propria, and intraepithelial lymphocytes were counted in the intestinal biopsy specimens of 14 children with treated celiac disease following a single challenge with gluten. The serum neutrophil chemotactic activity was measured at 0, 1, 3, 5, and 24 h after challenge. There was no significant change in the number of intraepithelial lymphocytes, but the biopsy samples obtained at 5 h showed a marked increase in the inflammatory cells of the lamina propria and a significant decrease in the number of mast cells. A pronounced decrease was present at 3-5 h in the number of eosinophil cells in the blood. The neutrophil chemotactic activity of sera showed a significant increment in 10 of 14 patients. The intestinal permeability of patients became abnormal, as detected by the increased absorption of lactulose. These findings suggest that degranulation of mast cells may be involved in the pathogenesis of the small intestinal mucosal injury in children with celiac disease.

Adolescent↗
PubMed1989

Galantase (beta-galactosidase) treatment in pediatric practice.

The authors diagnosed lactose malabsorption by the breath hydrogen analysis in 11 premature and mature babies, in 16 infants and in 28 children between the ages of 3-18 years. All patients were treated with Galantase (beta-galactosidase). According to the results, Galantase is very effective in splitting of lactose of breast-milk, cow-milk and artificial formulas. Pathological hydrogen increase was not detected during the treatment.

Adolescent↗
PubMed1988

HLA class II allelic variation and susceptibility to pemphigus vulgaris.

The autoimmune dermatologic disease pemphigus vulgaris (PV) is associated with the HLA serotypes DR4 and DRw6. Susceptibility to PV could be conferred either by sequences shared between the DR4 and DRw6 haplotypes or by different sequences in these haplotypes. We have examined the distribution of DR and DQ beta-chain and DQ alpha-chain alleles in PV patients and in control subjects by hybridization with oligonucleotide probes and sequence analysis of in vitro amplified DNA. Ninety percent (34/38) of the DR4 haplotypes in patients contain a specific DR beta I sequence present in 36% (16 of 44) of DR4 controls (P = 0.001). This sequence is also found in DRw6 haplotypes. However, it is present in only 25% (6 of 24) of DRw6 patients. The results of our analysis indicate that predisposition to PV is conferred by different sequences in DR4 and DRw6 haplotypes. The DR4 susceptibility is highly associated with the Dw10 DR beta I allele, implicating the polymorphic residues in the third hypervariable region. The DRw6 susceptibility is strongly associated with a rare DQ beta allele (DQB1.3). This allele differs from a common DQ beta allele (DQB1.1) only by a valine----aspartic acid substitution at position 57.

Alleles↗
PubMed1988

Learning and memory: regional changes in N-methyl-D-aspartate receptors in the chick brain after imprinting.

An extensive series of experiments has implicated a restricted region of the chick forebrain in the learning process of imprinting. The region is the intermediate and medial part of the hyperstriatum ventrale (IMHV). Previous studies have shown that training is associated with an increase in the area of the postsynaptic density of axospinous synapses in the left but not the right IMHV. The postsynaptic density is a site of high receptor density, and at least some axospinous synapses are excitatory. We found that imprinting is associated with a 59% increase in N-methyl-D-aspartate-sensitive binding of the excitatory amino acid L-[3H]glutamic acid in the left IMHV. The increase is probably due to an increased number of binding sites. The profile of sensitivity of the sites to a series of amino-, phosphono-substituted carboxylic acids (2-amino-3-phosphonopropionate to 2-amino-8-phosphonooctanoate) is characteristic of N-methyl-D-aspartate-type receptors. There were no significant effects of training on binding in the right IMHV. The effect of training on left IMHV binding could not be attributed to light exposure, arousal, or motor activity per se but was a function of how much the chicks learned. The changes in the left IMHV could increase the effectiveness of synaptic transmission in a region crucial for information storage and so form a neural basis for recognition memory.

Animals↗
PubMed1987

The role of a restricted region of the chick forebrain in the recognition of individual conspecifics.

It has been proposed that there are two neural systems underlying filial preference behaviour in the domestic chick. Firstly, a predisposition which serves to orient the chick towards objects resembling adult fowl, and secondly a learning system which is engaged by particular objects, including the bird's own mother. Lesions to a particular region of the chick forebrain, the intermediate and medial part of the hyperstriatum ventrale (IMHV), impairs the learning system but not the predisposition. The present experiment was designed to test the hypothesis that the IMHV is involved in learning to recognise individual members of a species. Between 6 and 10 h after chicks had hatched, bilateral lesions were placed in the IMHV (n = 16), and the Wulst (n = 16). There were 52 sham-operated controls. Following recovery from surgery (20-28 h later), all chicks were exposed to one of two stuffed jungle fowl for 4 X 50 min. Two hours after the final training session all birds were given a preference test. This test involved the simultaneous presentation of the fowl to which the chicks had previously been exposed and the fowl which they had not previously seen. While both the sham-operated and the Wulst-lesioned groups had a significant mean preference for the fowl to which they had been exposed during training, the IMHV-lesioned birds had no preference. This result is consistent with the hypothesis that IMHV is involved in learning to recognise individual birds, as well as other conspicuous objects.

Animals↗
PubMed1987

Studies on clonal assignment of urinary Escherichia coli O1:K1 strains.

Fifty-nine Escherichia coli strains belonging to two clonal groupings were investigated for major outer membrane proteins, colicin production, and partly for plasmid DNA content. The membrane protein patterns of the 01:K1:H7(H-):F11 and O1:K1:H-:F9 strains obtained by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were distinctly different from each other and, therefore, are useful for clonal assignment. All of the F11 isolates had one plasmid of about 85 Md in common which is suggested to be characteristic for the clone. Their content of smaller plasmid DNA was heterogeneous and showed geographical differences. The F9 strains showed a plasmid pattern different from the F11 strains. A plasmid of 2.6 Md was found in all of these isolates. Colicin production was found to be useful for clonal assignment only in two thirds of the F9 and not in the F11 strains. Some strains with identical properties seem to be of epidemic importance.

Bacterial Outer Membrane Proteins↗