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H Hildebrandt

Publications and source records attributed to H Hildebrandt.

At least 19 recordsLinked to original sources
PubMed1995

PKA activity in the antennal lobe of honeybees is regulated by chemosensory stimulation in vivo.

The involvement of cyclic nucleotide cascades has been suggested for chemosensory signal processing as well as synaptic plasticity. Cyclic AMP-dependent protein kinase (PKA) is a major mediator for transient changes in these second messengers. The objective of this study was to examine the role of PKA in the central processing of chemosensory information by the honeybee. Effects of chemosensory stimulation in vivo were detected in the first chemosensory neuropil of the honeybee brain, the antennal lobe (AL), by using a combination of shock freezing and specific determination of PKA activity. Mechanosensory or odor stimulation of the antennae had no effect on PKA activity. Brief application of aqueous solutions (pure water or sucrose solution) to an antenna caused a rapid and transient elevation of PKA activity in the ipsilateral AL. A series of such stimuli led to a graded increase in PKA activity followed by a rapid decrease during the first 10 s after the end of stimulation, but elevated levels of PKA activity were observed for as long as 1 min. These results suggest that PKA activity and its regulation contribute to central processing of chemosensory signals.

Animals↗
PubMed1995

Octopamine mediates rapid stimulation of protein kinase A in the antennal lobe of honeybees.

In the honeybee octopamine mediates mechanisms of arousal that interfere with the appetitive proboscis extension response to food-indicating chemosensory stimuli. This study demonstrates that injections of octopamine or cyclic adenosine monophosphate (cAMP) into the primary chemosensory neuropil of the honeybee, the antennal lobe, evokes a rapid and transient activation of cAMP-dependent protein kinase (PKA). Other monoamines detectable in the antennal lobe, dopamine and serotonin, do not affect the level of PKA activity. Stimulation of the bees' antenna with the appetitive stimulus water or sucrose solution in vivo also causes a short-term activation of PKA in the antennal lobe. The increased PKA activity can be detected immediately (0.5 s) after stimulation but reverts to the basal level within 3 s. This effect can be abolished by monoamine depletion with reserpine. Since octopamine is the only monoamine that stimulates PKA, it appears to mediate the PKA activation after sucrose stimulus and may contribute to the processing of this chemosensory input.

Animals↗
PubMed1995

[Effect of task difficulty on hemispheric differences in visual image processing].

Hemispheric specialization of visual imagery processes is a topic of recurrent debate. Recent theories have argued for a left postcentral center for the generation of visual images. Because of contradictory results the process of imaging has been divided into a left hemisphere component (visual imagery) and a right hemisphere component (supramodal spatial mental imagery). An alternative and more parsimonious account would be that the degree of difficulty of visual imagery tasks is responsible for hemispheric differences: easy tasks are solved faster within the left hemisphere because of a direct access to action control, whereas more difficult tasks rely on a right hemisphere specialization for spatial processing. In our experiment we varied the degree of difficulty by introducing concurrent tasks which were interspersed at random into the series of critical stimuli. Interspersing concurrent tasks prevents subjects from automatizing of critical processes and delays reaction times. For the critical visual imagery tasks we presented either upper or lower case letters to the different visual fields and asked for figural aspects of the corresponding lower or upper case letters, respectively. The interspersed stimuli concerned an estimation of the distance of the stimuli or the localization of the stimuli in the upper or lower part of the screen. We also presented upper and lower case letters in random order, thus forcing the subjects to shift between two different visual imagery tasks. In order to look for the effect of position-repetition priming upon visual field advantages we also analyzed the interaction of the position on the screen and its repetition with hemispheric advantages. In one of the visual imagery tasks, the experiments without concurrent tasks yielded a right visual field/left hemisphere advantage. On the other hand, interspersing other tasks resulted in a left visual field/right hemisphere advantage for visual imagery tasks, though none of the concurrent tasks showed a significant visual field advantage in itself. The same holds for combined and random presentation of the two different visual imagery tasks. The results therefore argue for a right hemisphere advantage for difficult visual imagery tasks, whereas easier tasks (monotonous presentation of only one visual imagery tasks) are processed faster in the left hemisphere. The random repetition of positions on the screen yielded a significant effect but had no influence on the visual field advantages found.

Adult↗
PubMed1994

Mental disorders and economic crisis--a study on the development of admission into the psychiatric hospitals of Prussia between 1876 and 1906.

Social causes of mental disorders are a long-standing issue of controversy in psychiatric epidemiology. Following Brenner's (1977) analysis, we analysed the correlation between admissions to psychiatric hospitals and the employment figures for almost 3 decades of the last century in Prussia. The employment figures were taken as an indicator of social stress, whereas the admission figures were taken as an indicator of the incidence of mental disorders. Two groups with different diagnoses were considered in the analysis; nowadays they would more or less correspond to "functional psychosis" (ICD 295-299) and "alcoholic psychosis" (ICD 291). Three other groups, i.e. epilepsy, progressive paralysis and severe learning disabilities, served as control groups to check the influence of modifications in help-seeking behaviour. In contrast to Brenner's mono-causal social stress model, there were no significant correlations for the group of functional psychoses for men or for women, whereas the admissions of males with alcoholic psychoses showed the expected trend to a high degree. The three control groups showed no obvious correlation with employment figures, arguing against a main effect of a modification of help-seeking behaviour on the results in the two experimental groups. Results are discussed and interpreted with regard to contemporary results in psychiatric epidemiology.

Adolescent↗
PubMed1994

Immuno-gold electron microscopical detection of heat shock protein 60 (hsp60) in mitochondria of rat hepatocytes and myocardiocytes.

We characterize the specificity of a polyclonal antibody against heat shock protein 60 (hsp60) and present an application for ultrastructural localization studies of this protein. The antibody was obtained from an IgG fraction (AB 121) originally raised against the calcium binding protein calsequestrin by immunoabsorption on isolated rat liver hsp60. As shown by partial N-terminal amino acid sequence analysis of immunoprecipitated proteins AB 121 contained reactivities against hsp60, calsequestrin and the glycoprotein fetuin. In rat heart AB 121 recognized calsequestrin and hsp60. In human and rat liver the only reacting protein was hsp60. In rat erythrocytes the antibody bound to 61 kDa and 58 kDa isoforms of fetuin. According to published data no amino acid sequence homologies nor common motifs are found between calsequestrin, hsp60 and fetuin. As the first application the anti-hsp60 antibody was used for immuno-gold electron microscopical localization of hsp60: in myocardiocytes and hepatocytes of the rat strong labelling was obtained exclusively in mitochondria. No extramitochondrial structures were labelled. The specificity of the antibody and its ability to be visualized by immuno-gold electron microscopy offers the possibility to study the expression of this protein in the liver and in other organs. Possible clinical applications of these studies are discussed, since hsp60 could be a target antigen of autoantibodies in diseases such as autoimmune hepatitis, primary sclerosing cholangitis or primary biliary cirrhosis.

Amino Acid Sequence↗
PubMed1993

Oligosaccharide reprocessing and recycling of a cell surface glycoprotein in cultured rat hepatocytes.

The metabolism of the cell surface glycoprotein dipeptidyl peptidase IV(DPPIV) was studied in cultured rat hepatocytes. In pulse-chase labelling experiments using L-[35S]methionine a 100-kDa high-mannose precursor polypeptide is converted into the mature complex-type 110-kDa glycoprotein. Digestion with exo- and endoglycosidases and metabolic labelling with radioactive sugars demonstrate that the 110-kDa form contains about 6 complex-type oligosaccharides which are fucosylated and sialylated. About 25 min after the beginning of the pulse-labelled glycoprotein appears in the sinusoidal membrane. Physiologically only the 110-kDa form is found in the cell surface. If cell surface DPP IV was desialylated by sialidase at 4 degrees C, it is resialylated during incubation at 37 degrees C. This oligosaccharide reprocessing indicates that the surface glycoprotein has been recycled to the cell compartment containing terminal glycosyltransferases (presumably the trans Golgi system). Two different methods demonstrate internalization of cell surface DPP IV: 1) The complex cell surface DPPIV -anti-DPP IV-antibody -L-[35S]methionine-labelled secondary goat-anti-mouse-antibody formed at 4 degrees C becomes less accessible to trypsin during incubation at 37 degrees C. 2) Part of the complex plasma membrane DPP IV-anti-DPP IV-antibody formed in the cold cannot be recognized by the radioactive secondary antibody after rewarming. Internalization is not blocked by inhibition of protein synthesis with cycloheximide. During internalization of plasma membrane DPP IV its concentration in the membrane remains constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

[Prosthetic aids in the resection of the middle portion of the mandible].

Prosthetic aids in resections of the middle piece of the mandible. The authors describe a prosthesis which is inserted during the resection of the middle piece of the mandible. Due to its construction it prevents the soft tissues of the floor of the mouth from sinking back. Such a prosthesis has been used in 18 cases. Respiratory complications did not occur; no tracheotomy was necessary. During the postoperative phase, the prosthesis came up to expectations, but it could not prevent cicatricial contraction in the operating area. Occlusion-conformable positioning of the fragments will be achieved only it the remaining teeth are suited for function-stable prosthetic care. Consequently, secondary osteoplasty should not be abandoned.

Denture Design↗