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Biomedical subjects

G Horn

Publications and source records attributed to G Horn.

At least 109 records · Page 6Linked to original sources
PubMed1985

Connections of the hyperstriatum ventrale of the domestic chick (Gallus domesticus).

The intermediate part of the medial component of the hyperstriatum ventrale (IMHV) of the chick telencephalon is implicated in the learning process of imprinting. The afferent connections of this region were investigated using the retrograde neuronal tracers horseradish peroxidase (HRP), nuclear yellow and fast blue. Labelled cells were found (i) ipsilaterally in the visual Wulst, neostriatum pars intermedia and caudalis, the posterior part of the hyperstriatum ventrale, the dorsal part of the archistriatum, paleostriatum augmentatum, dorsomedial part of the thalamus, and (ii) bilaterally in the hippocampus, area septalis, ventromedial part of the thalamus and the stratum album centrale of the tectum opticum. The efferent projections of the IMHV were studied using the anterograde tracer, [3H]leucine. Labelling was seen ipsilaterally over the dorsolateral part of the hemispherium telencephali, the paleostriatum augmentatum and the posterior and dorsal parts of the archistriatum. Double labelling with nuclear yellow and fast blue revealed (i) neurons in the IMHV which project to both the paleostriatum augmentatum and the archistriatum, and (ii) neurons in the hippocampus which project bilaterally to the IMHV.

Afferent Pathways↗
PubMed1985

Changes in the structure of synapses associated with learning.

Two experiments were conducted to investigate the effects of training on a region of the chick brain known to be critically involved in imprinting, the intermediate and medial extent of the hyperstriatum ventrale (IMHV). In the first experiment, three groups of chicks were used: (i) dark-reared (n = 9), (ii) trained for 20 min (n = 17), and (iii) trained for 140 min (n = 7). Chicks were trained by exposing them when they were approximately 21 hr old to a flashing red light. Chicks were killed when they were approximately 30 hr old and blocks of tissue were removed from the right and left IMHV. Stereological techniques were used to measure from electron micrographs the numerical density of dendritic spine and shaft synapses and the length of the postsynaptic density of these synaptic junctions. There was a significant effect of training only in the left IMHV and on only one measure, the overall mean length of the postsynaptic density of spine synapses, SPL. This measure was significantly greater by 17.2% in chicks trained for 140 min than in dark-reared controls. There was no significant effect of training for 20 min. In the second experiment one group of chicks (n = 15) was exposed to a rotating red box for a total of 3 hr. Another group of chicks was dark-reared (n = 15). The chicks were killed when they were approximately 46 hr old. Samples from the hyperstriatum accessorium and IMHV of the right and left sides were analyzed. Training was associated with a significant change, an increase, only of SPL in the left IMHV.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1984

Long-term consequences of exposure to an imprinting stimulus on 'spontaneous' impulse activity in the chick brain.

Young chicks were exposed in a running wheel to an imprinting object, a rotating flashing red box (n = 36 chicks) or a rotating stuffed jungle fowl (n = 18). The net number of revolutions of the wheel toward the imprinting object provided a measure of approach activity during training. The chicks were subsequently anaesthetized and the 'spontaneous' firing rates of units were recorded simultaneously in two regions of the left forebrain hemisphere. One microelectrode penetration was made through a region, the intermediate and medial part of the hyperstriatum ventrale (IMHV) known to be critical for imprinting; simultaneously another microelectrode penetration was made through the visual Wulst. The electrodes were advanced in steps of 250 micron and the spontaneous discharge of multiple units at each site recorded. The mean firing rate from greater than or equal to 3 sites was calculated for IMHV and for the hyperstriatum accessorium of the Wulst. There was a negative correlation between mean firing rate of units in IMHV and approach activity for chicks trained on the box. The effect was: stimulus specific since it was not found in chicks trained on the jungle fowl; and regionally specific since approach activity, depending on conditions which are described, was either not correlated or positively correlated with mean firing rate for neurons in the hyperstriatum accessorium. The positive correlation was not dependent on the training stimulus but on the presence of a visually responsive lamina deep to the hyperstriatum accessorium.

Action Potentials↗
PubMed1984

Modifiability of responsiveness in a visual projection area of the chick brain: visual experience is only one of several factors involved.

The effects of visual experience on neuronal responsiveness in the hyperstriatum accessorium, a visual projection area, were investigated in 4 groups of domestic chicks, each comprising dark-reared (total = 44) and visually experienced (total = 34) birds. Visually experienced birds were placed singly in running wheels facing a flashing red light for 3 h; wheel revolutions were used as a measure of the chicks' locomotor activity. At approximately equal to 48 h after hatching each chick was anaesthetized and a microelectrode advanced in 250 micron steps through the left Wulst. After each step the responsiveness of units to diffuse retinal illumination (light flashes) was tested. Each recording site at which responses greater than or equal to 5 successive flashes could be evoked was classified as a response site. In some chicks at least one site responding briskly to greater than or equal to 15 successive flashes was found deep to the hyperstriatum accessorium. The zone of markedly increased responsiveness is referred to as the visually responsive lamina. The effect of visual experience on the response of units in the hyperstriatum accessorium varied between the groups of chicks. Visual experience did not significantly effect neuronal responsiveness in this region for chicks without a visually responsive lamina. For chicks with a lamina there was an effect of visual experience, but the effect again varied between groups. When data from inactive, visually experienced chicks were excluded, the group-to-group variation ceased to be significant. Thus visual experience alone was not adequate consistently to bring about long-term changes in the responsiveness of neurones in the hyperstriatum accessorium. Such experience was likely to increase neuronal responsiveness provided the chicks: were behaviourally active; and possessed a visually responsive lamina.

Animals↗
PubMed1984

[Electrochemical reduction of the anthracycline antibiotic 5-iminodaunorubicin. Isolation and structural clarification of the reduction products].

After electrochemical reduction of the potential cancer chemotherapeutic 5-iminodaunorubicine two new compounds, were isolated purely by chromatographic separation. Based on 1H-NMR, IR-, UV/VIS- and MS-investigations the one reaction product was identified as 7-desoxy-5-iminodaunorubicinone as expected, while the other was proofed as 9-acetyl-9,12-dihydroxy-4-methoxy-7,8,9,10-tetrahydroxy-6,11-naphthac enchinone.

Daunorubicin↗
PubMed1983

General practice orthopaedic outpatient referrals in North Staffordshire.

A study was made of 813 orthopaedic referrals by 134 general practitioners in North Staffordshire. The referral rates showed no relation to practice list size or the doctors' previous orthopaedic experience. The published waiting times did not accurately reflect clinic vacancies, and no effective priority rating of letters by consultants was shown. Less than 1% of patients had an appointment within four weeks. One quarter of the patients failed to attend and, of those who did, 27% received physiotherapy or a "simple" appliance, or both, while 16% received treatment already available from their general practitioner. Patients from high referring doctors showed the same pattern of distribution in body area affected and treatment outcome as those from low referring doctors, but had a significantly longer time to wait for their appointment. A survey of non-attenders showed that 56% of the patients failed to attend because the condition had resolved.

England↗
PubMed1983

Putative cholinergic afferents of the chick hyperstriatum ventrale: a combined acetylcholinesterase and retrograde fluorescence labelling study.

The retrograde fluorescent tracers Fast Blue and Nuclear Yellow were injected into the intermediate part of the medial hyperstriatum ventrale (IMHV) of the chick telencephalon. After the appropriate survival times, the brains were processed for acetylcholinesterase (AChE) histochemistry using the thiocholine technique. In some telencephalic regions, fluorescent retrograde labelling and brown AChE reaction product were observed simultaneously in the same neurones by using a combination of ultraviolet and bright-field illumination. These AChE-positive afferents of IMHV arose from the hippocampus, septum, septal nuclei, hyperstriatum ventrale and neostriatum.

Acetylcholinesterase↗
PubMed1983

Imprinting in the domestic chick: the role of each side of the hyperstriatum ventrale in acquisition and retention.

Previous experiments have shown that the acquisition of a preference through imprinting is impaired if part (IMHV) of the hyperstriatum ventrale is destroyed bilaterally before chicks are exposed to a visually conspicuous (training) object. The present experiments were undertaken to determine (i) whether the acquisition of a preference for the training object is possible with only one IMHV intact and, if acquisition is possible, (ii) whether destruction of this IMHV impairs retention. Chicks were hatched and reared in darkness to congruent to 12 h posthatch. The chicks were then anaesthetised and a lesion placed in (i) the left IMHV (N = 12 chicks), (ii) the right IMHV (N = 12), (iii) the left hyperstriatum accessorium (HA) (N = 12) or (iv) the right HA (N = 12). There were 48 sham operated controls. Approximately 24 h after the operation chicks were exposed to the training stimulus. Their approach to this stimulus and to a second, novel stimulus were then measured and a preference score calculated. All five groups of chicks preferred the training stimulus and the magnitude of the preference was similar in all groups. To determine whether the IMHV region which had been intact during training was essential for retention, all chicks were anaesthetised for a second time, congruent to 20 h after the end of training. The remaining IMHV region was then destroyed. Approximately 28 h later the chicks' preferences were again measured. The sham operated and HA lesioned chicks continued strongly to prefer the training stimulus, but the birds lesioned in IMHV showed no such retention, the preference score of the IMHV chicks being significantly lower than that of the sham operated and HA lesioned chicks. The order in which the right and left sides were destroyed did not significantly influence the preference score; this result was true both for IMHV and for HA chicks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Changes in telencephalic catecholamine levels in the domestic chick. Effects of age and visual experience.

The concentrations of adrenaline, dopamine and noradrenaline were measured in 3 regions of the domestic chick telencephalon: (a) the Wulst; (b) a medial forebrain sample comprising mainly the intermediate part of the medial hyperstriatum ventrale (IMHV); and (c) a basal forebrain sample comprising mainly paleostriatum augmentatum. There was no significant left/right hemispheric asymmetry in the concentration of any of these catecholamines in any region studied. Adrenaline was undetectable in the Wulst and medial forebrain samples and only trace amounts were found in the basal forebrain samples of 1-day-old, light-reared chicks. Dopamine concentrations of 9.13 +/- 1.13 (S.E.M.) ng/g were present in the Wulst, 16.66 +/- 2.56 ng/g in the medial forebrain and 121.19 +/- 33.06 ng/g in the basal forebrain samples at hatching. These levels did not alter with age or with visual experience of an imprinting stimulus during the first 50 h post-hatch. At hatching, noradrenaline concentrations of 35.83 +/- 8.61 ng/g were present in the Wulst, 26.09 +/- 3.75 ng/g in the medial forebrain and 53.13 +/- 7.85 in the basal forebrain samples. The noradrenaline concentrations in the Wulst and medial forebrain samples increased significantly over the first 50 h post-hatch in dark-reared chicks. Visual experience increased noradrenaline levels in all 3 regions of the telencephalon studied.

Aging↗
PubMed1983

An intraocular lens carrier.

An intraocular lens carrier for anterior and posterior chamber lenses has been developed. The device consists of a protective polypropylene envelope with an insertion leaf, which allows anterior chamber lenses to be inserted without iris or corneal touch and posterior chamber lenses to be guided into the ciliary sulcus or capsular bag with minimal or no haptic manipulation. +

Anterior Chamber↗
PubMed1983

Nucleotide sequence of the structural gene for diphtheria toxin carried by corynebacteriophage beta.

A 1,942-base-pair DNA segment encoding the structural gene for diphtheria toxin was sequenced, and the primary structure of the toxin was deduced. Restriction enzyme fragments corresponding to nontoxic or hypotoxic peptides of the toxin were isolated from corynebacteriophage beta and cloned into Escherichia coli on plasmid pBR322, and the sequence was determined. The mature toxin molecule deduced from the sequence has 535 amino acid residues and a molecular weight of 58,342. The deduced sequence for the fragment A moiety was the same as that determined at the protein level, except for a single serine residue, which had been mispositioned in the earlier study. Several differences were noted with respect to the partial sequence data available on the fragment B moiety, some or all of which may reflect genetic variations among populations of corynephages carrying the toxin gene. The DNA sequence predicts a 25-residue leader peptide preceding the mature protein, which is presumably involved in secretion of the toxin from lysogenized Corynebacterium diphtheriae. We infer that initiation of translation probably occurs at a GTG codon (codon -25). Cloned restriction fragments containing sequences for the amino-terminal region of toxin, together with 5' flanking regions, were expressed in E. coli. Toxin-related peptides were synthesized and secreted into the periplasmic space. These results provide a basis for applying recombinant DNA methods to the study of diphtheria toxin and for producing novel, genetically altered forms of the toxin suited to the construction of new classes of immunotoxins.

Amino Acid Sequence↗
PubMed1983

[Ergotropic efficacy of 2,3-dimethylquinoxaline-1,4-dioxide and 2-methylquinoxaline-1,4-dioxide in growing broilers using hydrocolloid-rich rations as well as broiler fattening feed].

2,3-dimethyl-quinoxaline-1,4-dioxide and 2-methyl-quinoxaline-1,4-dioxide proved to be ergotropic in the feeding of a hydrocolloid ration as well as of a broiler fattening feed. They are at least equal to Nitrovin. The ergotropic effect of the hydrocolloid ration was higher than that of the conventional ration. For this reason methylated quinoxaline-1,4-dioxides are considered as belonging to the intestinal stabilisers. They increased nutrient and energy retention and decreased feed efficiency by approximately equal to 10%. Residues in the liver, the kidneys and the intestines could only be detected after 10 times the ergotropic amount.

Animal Feed↗
PubMed1983

Disaccharidases in coeliac disease.

In 30 children presenting with complaints characteristic of malabsorption in whom congenital enzyme deficiency could be excluded, determination of the enzymes lactase, saccharase and maltase was performed in the tissue sample obtained by jejunal biopsy; histology was also carried out in all cases. In 23 cases the diagnosis of coeliac disease could subsequently be confirmed, in the other 7 cases the diagnosis could neither be rejected nor established with certainty. All three enzymes had a decreased activity in cases displaying subtotal or total villous atrophy, the most sensitive among them being lactase: in 69% of cases no lactase activity could be shown while saccharase and maltase were absent in 29 respectively 4% of the cases. No close correlation exists between the light-microscopic findings and the activity of enzymes since total absence of enzyme activity may be associated with only moderate villous atrophy. Lack of disaccharidase activity in the upper section of the small bowel does not necessarily mean disaccharide malabsorption exhibiting clinical symptoms, it only indicates a reduced capacity of disaccharide splitting. It has been concluded that routine determination of disaccharidase activities is not justified within the diagnostic procedure of coeliac disease.

Atrophy↗
PubMed1983

The D-xylose test in coeliac disease.

The results of more than 500 D-xylose loading tests are described. In almost half of the cases proven or suspected to be coeliac disease, the blood xylose level was low. In 69 patients the result was compared to that of small bowel biopsy. Abnormal levels were found in 98% of total or subtotal villous atrophy. It is therefore suggested to apply the test for screening in severe cases. Since with increasing age the absorption of xylose improves, this is to be considered when evaluating the test. At the time of gluten readministration the D-xylose test suggests the presence of histological changes well before their clinical manifestation. Therefore the result of the D-xylose test serves as an indication for small bowel biopsy. An abnormal D-xylose test after introduction of the gluten-free diet points to its deficiency.

Adolescent↗