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Biomedical subjects

G Hoch

Publications and source records attributed to G Hoch.

18 recordsLinked to original sources
PubMed2006

13C labelling reveals different contributions of photoassimilates from infructescences for fruiting in two temperate forest tree species.

The pathways of currently fixed carbon in fruit bearing branchlets were investigated in two temperate forest tree species (CARPINUS BETULUS and FAGUS SYLVATICA), which differ in texture of their vegetative infructescence tissues (leaf-like in CARPINUS vs. woody in FAGUS). During late spring, (13)C pulse-labelling was conducted on girdled, defoliated, girdled plus defoliated and untreated fruiting branchlets of mature trees IN SITU, to assess changes in C relations in response to the introduced C source-sink imbalances. At harvest in early August, 75 - 100 % of the recovered (13)C label was bound to infructescences (either fruits or vegetative infructescence tissue), revealing them as the prime C sinks for current photoassimilates. Leaves on girdled branchlets were not stronger labelled than on ungirdled ones in both species, indicating no upregulation of the leaves' photosynthetic capacity in response to the prevention of phloemic transport, which was also supported by measurements of light saturated photosynthesis. In contrast, (13)C labels tended to be higher after complete defoliation in the vegetative infructescence tissues of CARPINUS, suggesting enhanced net photosynthesis of green infructescence parts as compensation for the loss of regular leaves. The total labelling-derived (13)C content of whole infructescences was very similar between foliated and defoliated CARPINUS branchlets. Cupulae of FAGUS, on the other hand, remained almost unlabelled on defoliated branchlets, indicating the photosynthetic inactivity of this woody infructescence tissue. Consequently, CARPINUS still produced relatively high fruit masses on girdled plus defoliated branchlets, while in FAGUS fruit development ceased almost completely at this most severe treatment. Our results highlight that green vegetative infructescence tissue assimilates substantial amounts of C and can partly substitute regular leaves as C sources for successful fruit development.

Betulaceae↗
PubMed2001

Effects of Glyptapanteles liparidis (Hym.: Braconidae) parasitism, polydnavirus, and venom on development of microsporidia-infected and uninfected Lymantria dispar (Lep.: Lymantriidae) larvae.

Effects of parasitism, polydnavirus, and venom of the endoparasitoid Glyptapanteles liparidis on Lymantria dispar larvae infected with the microsporidium Vairimorpha sp. and uninfected hosts were studied. We tested the impact on growth and development of hosts, as well as on microsporidian infection. Both parasitism and polydnavirus/venom treatment alone caused a slight increase in growth rate and relative growth rate in uninfected fourth instar hosts. This effect was more pronounced with the addition of Vairimorpha infection. With no parasitism, however, infection reduced host growth markedly. Microsporidiosis delayed larval molts of L. dispar, and additional polydnavirus/venom treatment or parasitization induced significantly earlier molting. Polydnavirus/venom treatment of uninfected L. dispar resulted in prolonged larval development due to supernumerary molts and in higher pupal mortality. Infected larvae treated with polydnavirus/venom died earlier than infected larvae that were not treated and produced more Vairimorpha spores per unit fresh mass of the host.

Animals↗
PubMed2000

Interactions between an entomopathogenic microsporidium and the endoparasitoid Glyptapanteles liparidis within their host, the gypsy moth larva.

Interactions in the host-parasitoid-pathogen system, Lymantria dispar L. (Lep., Lymantriidae)-Glyptapanteles liparidis (Bouché) (Hym., Braconidae)-Vairimorpha sp. (Protista, Microspora), were investigated. Host selection experiments revealed that G. liparidis females did not discriminate between infected and uninfected host larvae for oviposition. Transmission of the microsporidium from infected to uninfected hosts by stinging female wasps could not be ascertained. Females that developed in infected L. dispar larvae did not transmit the pathogen via oviposition. Vairimorpha infection of the host negatively affected the performance of the braconid, when inoculation took place either before or after parasitization. Microsporidiosis of the host caused delayed development, reduced pupation and adult eclosion, reduction in size and weight, and reduction of adult longevity of G. liparidis. Parasitoids themselves were not systemically infected by Vairimorpha sp., but braconid larvae did ingest microsporidian spores at the end of their endoparasitic development and accumulated the undigested and ungerminated spores in the blind midgut. Negative effects of host infection on parasitoid larvae were detectable from the beginning of parasitoid larval development. Lethal time was reduced when L. dispar larvae were infected and parasitized, often at the expense of the parasitoid when G. liparidis were unable to complete endoparasitic development before the host died. Intensity of infection, measured as number of spores produced per milligram fresh weight of L. dispar larva, was slightly higher in parasitized and infected hosts than in unparasitized and infected hosts.

Animals↗
PubMed1999

Purification and characterization of stachyose synthase from lentil (Lens culinaris) seeds: galactopinitol and stachyose synthesis.

Stachyose synthase (STS) (EC 2.4.1.67) was purified 313-fold from mature seeds of lentil. The final preparation had a specific activity of 9.09 nkat stachyose formed per milligram of protein. The enzyme was a monomeric protein with a molecular mass of 88.6 kDa (SDS-PAGE) and an isoelectric point of 4.8 (chromatofocusing). Western analysis revealed cross-reactivity of polyclonal antibodies raised against STS from adzuki bean with the lentil enzyme. The purified enzyme catalyzed a range of different galactosyl transfer reactions. In addition to the genuine STS reaction (raffinose + galactinol --> stachyose + myo-inositol), the enzyme catalyzed the reversible galactosyl transfer from galactinol to d-pinitol (1d-3-O-methyl-chiro-inositol), yielding galactopinitol A (O-alpha-d-galactopyranosyl-(1 --> 2)-4-O-methyl-d-chiro-inositol) and myo-inositol. Galactopinitol A could be further galactosylated by STS to give ciceritol (O-alpha-d-galactopyranosyl-(1 --> 6)-O-alpha-d-galactopyranosyl-(1 --> 2)-4-O-methyl-d-chiro-inositol). Enzymatic synthesis of galactopinitol A and ciceritol is a new observation. However, STS was not only able to utilize galactopinitol A as galactosyl acceptor, but also as galactosyl donor to form stachyose from raffinose. The role of STS in the metabolism of galactosyl cyclitols and oligosaccharides in plant seeds is discussed.

Disaccharides↗
PubMed1998

The development of experimental autoimmune encephalomyelitis in the mouse requires alpha4-integrin but not alpha4beta7-integrin.

Because monoclonal antibodies (mAbs) directed against alpha4-integrin and VCAM-1 inhibit the development of experimental autoimmune encephalomyelitis (EAE) in vivo, it has been concluded that the successful therapeutic effect is due to interference with alpha4beta1/VCAM-1-mediated interaction of autoaggressive T cells with the blood-brain barrier. A possible role for alpha4beta7-integrin, or interference with other T cell mediated events during the pathogenesis of EAE, has not been considered. We have compared the effects of mAb therapy on the development of EAE in the SJL/N mouse, using a large panel of mAbs directed against alpha4, beta7, the alpha4beta7-heterodimer, and against VCAM-1. Although encephalitogenic T cells express both alpha4-integrins, mAbs directed against the alpha4beta7-heterodimer or against the beta7-subunit did not interfere with the development of EAE. In contrast, mAbs directed against alpha4 and VCAM-1 inhibited or diminished clinical or histopathological signs of EAE. Our data demonstrate for the first time that alpha4beta7 is not essential for the development of EAE. Furthermore, our in vitro studies suggest that the therapeutic effect of anti-alpha4-treatment of EAE might also be caused by inhibition of antigen-specific T cell proliferation.

Animals↗
PubMed1998

T cell interaction with ICAM-1-deficient endothelium in vitro: essential role for ICAM-1 and ICAM-2 in transendothelial migration of T cells.

Transendothelial migration is a crucial step in the complex process of lymphocyte extravasation during lymphocyte homing, immunosurveillance and inflammation. However, little is known about the precise role of cell adhesion molecules (CAM) involved in this particular event. To define the CAM involved in T cell adhesion versus transendothelial migration, we have previously established an in vitro transendothelial migration system using mouse T cells and mouse endothelioma cells. We demonstrate here that, using ICAM-1-deficient endothelioma cells derived from ICAM-1 mutant mice, transendothelial migration of T cells was inhibited to a much greater extent when compared to migration across wild-type cells treated with a blocking anti-ICAM-1 monoclonal antibody. This unexpected result was confirmed by a rescue experiment using retroviral transfer of wild-type ICAM-1 into ICAM-1-deficient endothelial cells. Additional experiments showed that, in the absence of functional ICAM-1, only ICAM-2 was involved in transendothelial migration, but not PECAM-1, VCAM-1, or E-selectin. Taking this novel approach, we show that ICAM-1 and ICAM-2 are essential for transendothelial migration of T cells.

Animals↗
PubMed1997

Immunosurveillance modelled in vitro: naive and memory T cells spontaneously migrate across unstimulated microvascular endothelium.

As a model for T cell immigration into non-lymphoid tissue we set up an in vitro assay that would allow us to investigate the phenotype of T lymphocytes from peripheral lymph nodes (PLN), mesenteric lymph nodes (MLN) or peripheral blood (PBL) of mice, which were able to spontaneously migrate across unstimulated microvascular endothelium. The transendothelial migrating T cell population was enriched for T lymphocytes expressing a "recently activated/memory' phenotype: LFA-1/CD44/ICAM-1high, but also contained CD45RBhigh and LFA-1low T cells, which in the case of MLN T cells were phenotyped as CD4+ and thus characterized as naive T cells. Transmigrated T cells could be further distinguished from their original populations and from each other by their distinct but heterogeneous expression patterns for L-selectin, alpha 4 beta 7-integrin and PECAM-1. This observation suggests the presence of phenotypically different migratory T cells among MLN, PLN and PBL. Additional studies provided evidence that the capacity to migrate across unstimulated microvascular endothelium was a characteristic of a T cell population that could phenotypically be differentiated from activated T cells. The endothelial cells were found to play an active role in selecting the traversing T cell population, as they controlled the number and phenotype of spontaneously transmigrating T cells. Our studies suggest that the capacity to transmigrate across unstimulated microvascular endothelium and hence to immigrate into non-lymphoid tissue is owned by a phenotypically heterogeneous T cell population, which is enriched for memory T cells but not devoid of naive T cells.

Animals↗
PubMed1996

Simultaneous evaluation of articulatory velopharyngeal function under different dynamic conditions with EMA and videoendoscopy.

Objective examination of velopharyngeal (VP) sphincter function has been described based on multiple methods. Videofluoroscopy and videoendoscopy represent today's clinical standard. A new concept of analysis of VP functioning is described using electromagnetic articulography (EMA) for midsagittal measurement of velar movement and videoendoscopy in a setting for simultaneous recording. Multidimensional analysis of VP functions using this setting is demonstrated for a normal subject. Timing aspects of VP closure and a transverse-sagittal ratio of VP port diameter are reported under different conditions of speech dynamics.

Adult↗
PubMed1996

Midsagittal velar kinematics during production of VCV sequences.

We present data on velar speech movements examined by electromagnetic articulography (EMA), a tool for the study of velar kinematics. Based on investigations on 22 normal German subjects (15 male, 7 female), movement paths of the velum using a sensor positioned on the midsagittal anterior surface were recorded using a series of high and low vowel VCV utterances. Maximum velar elevation (mean = 13.5 +/- 0.6 mm [SD]) with the rest position as a reference was observed during the production /iti/. The average maximum articulatory velocity of velar movements during /iti/ production was 141.0 mm/sec. Maximum movement of the velum observed during production of /ana/ averaged 7.5 +/- 1.1 mm. The direction of velar movement ranged between 44.6 degrees and 50.4 degrees relative to the bite plane registered electromagnetically. The influence of loudness variation of sequence production is demonstrated and discussed with the literature.

Adult↗
PubMed1995

Electromagnetic articulography as a method for detecting the influence of spikes on tongue movement.

In orthodontics dysfunctions of the tongue are discussed as a factor in the development of malocclusion. A new objective method for examining tongue movement is the electromagnetic articulography (EMA). This enables movements of the tongue to be followed using the principle of inductive distance measurements. A helmet made of acrylic material serves as a carrier for three transmitter coils. These are located in front of the forehead, in front of the chin, and at the back of the neck. Receiver coils are fixed to the tip of the tongue and at two points on the dorsum of the tongue. The distance between the receiver and the transmitter coils is calculated by means of a personal computer. The movement trajectories are displayed on a computer screen in x-y-coordinates. Tongue movements of one patient with an anterior open bite are shown during characteristic test sounds and during swallowing. The first examination took place without any orthodontic appliance. In a second series in the same session, tongue movement was recorded under the influence of an orthodontic appliance with spikes. While the patient shows vertical combined with sagittal components in the movement pattern of the tongue without an orthodontic appliance, the same patient, under the influence of an orthodontic appliance with spikes, shows a change of the rest and work position of the tongue and in the pattern of tongue movement with a more posterior position of the tongue, and with an increase in the vertical and a decrease in the sagittal components of the movement pattern.

Acrylic Resins↗
PubMed1994

[Simultaneous electromagnetic articulography and video endoscopy. A case contribution to the objective diagnosis of the velopharyngeal sphincter].

An objective examination of velopharyngeal sphincter function (VP) is possible using a variety of signal and pictorial methods to differing degrees. Video endoscopy and videofluoroscopy are the currently accepted clinical standard. With the help of a new concept described here it is possible both to analyze VP function in the midsagittal plane using electromagnetic articulography (EMA) and also to examine simultaneously the horizontal plane video endoscopically. This multidimensional analysis of VP function is presented in a case study of a healthy test person and the timing aspects of VP closure and transverse-sagittal ratio of VP port-diameters ist reported.

Adult↗
PubMed1993

Speech freezing in Parkinson's disease: a kinematic analysis of orofacial movements by means of electromagnetic articulography.

Kinematic recordings of orofacial movements by means of electromagnetic articulography were performed in an akinetic-rigid Parkinsonian patient presenting with intermittent speech freezing in diadochokinesis tasks (rapid repetitions of the syllable /ta/). During freezing periods the patient produced a sustained /a/ instead of the required consonant-vowel sequences. The underlying articulatory trajectories were characterized by repetition rates amounting to 8-10 Hz concomitant with reduced movement amplitudes. Obviously, the undershooting of articulatory gestures failed to establish a sufficient occlusion of the vocal tract giving rise to the perceived speech freezing. In contrast, preserved diadochokinesis occurred at frequencies of 4-6 Hz. Most probably, the increased articulatory repetition rate reflects a pacing of orofacial movements by released tremor oscillations. Due to slowing of articulatory movements spastic dysarthrics can also present with missing syllabic modulation during oral diadochokinesis. The results of the articulographic recordings demonstrate the different pathophysiology of Parkinsonian freezing.

Articulation Disorders↗
PubMed1992

Erythrocyte pyruvate kinase deficiency: relations of residual enzyme activity, altered regulation of defective enzymes and concentrations of high-energy phosphates with the severity of clinical manifestation.

The defective enzymes of 54 patients with pyruvate kinase (PK) deficiency were characterized according to the recommendations of the International Committee for Standardization in Haematology (ICSH). The erythrocyte PK activity in whole blood was calculated considering the 16-fold higher activity of the reticulocyte enzyme (AR) compared to the erythrocyte enzyme (AE). The following parameters turned out to give a good correlation to the degree of haemolytic anaemia and can therefore serve as a prognostic tool: All patients with a severe course of the disease had residual erythrocyte PK activities less than 33% of the normal enzymes (percentage activity), and patients with mild haemolytic anaemia exhibited residual activity values below and above this threshold value. Studies of enzyme cooperative showed that positive cooperative or mixed cooperative phosphoenolpyruvate (PEP) binding with a predominant positive cooperative part appeared in all cases with a mild clinical course, and about one-third of the severe ones. Negative cooperativity or mixed cooperativity with predominant negative cooperative part was observed only with severe haemolytic anaemia. Furthermore, the determination of glucose-6-phosphate (G-6-P) turned out to be a good prognostic criterion, i.e. all patients with mild clinical course exhibited G-6-P-concentrations lower than 0.11 mumol/l red blood cells. In the case of patients with severe haemolytic anaemia, about 80% showed values higher than 0.11 mumol/l RBC.

2,3-Diphosphoglycerate↗
PubMed1987

Influence of phytate on in vitro digestibility of casein under physiological conditions.

The phytic acid content of four different varieties of beans under different processing conditions was estimated. It was highest in red kidney (1.86-2.13%) slightly lower in pigeon (1.86-2.03%), white (1.80-1.96%) and black eyed beans (1.15-1.64%). There was no significant change in phytic acid content of beans after soaking at 25 degrees C for 22 hours. However, both soaking and cooking revealed 26-37% loss of phytic acid in all four varieties of beans. The rate of in vitro casein digestibility with and without phytic acid at concentrations found in legumes was determined at pH 8 and 37 degrees C using multienzyme technique. Addition of 5 mg Na-phytate reduced the casein digestibility up to 20% compared to the control. However, only 25% reduction of casein digestibility was observed in the presence of 25 mg of Na-phytate. Higher concentration of Na-phytate had no significant effect on the rate of casein digestibility. Data strongly suggest the formation of protein phytate complex at alkaline pH of small intestine.

Caseins↗