PubMed Health⌕ Search

Biomedical subjects

J Brandenburg

Publications and source records attributed to J Brandenburg.

13 recordsLinked to original sources
PubMed2006

Acute neuromuscular responses to resistance training performed at different loads.

The aim of this study was to compare the acute neuromuscular responses during resistance exercise performed with different loading protocols. Thirteen (N=13) college-aged male subjects experienced in weight training completed two different weight training protocols involving a single elbow flexion exercise. During both protocols subjects performed three sets of the exercise with a 3-min rest between each set. One protocol required the subjects to perform each set to failure using 100% 10 repetition maximum (RM) load whereas the second protocol required the subjects to perform 10 repetitions for the first two sets using 90% 10RM load and only go to failure on the third set. Maximal voluntary isometric contraction (MVIC), integrated EMG recording (iEMG) of the biceps brachii, and blood lactate were measured before and upon completion of the two training protocols. Subjects were able to perform a significantly greater volume of work (total repetitionsxload) in the 90% 10RM protocol compared to the 100% 10RM protocol. Both protocols elicited similar cumulative levels of fatigue as reflected by a decrease in MVIC and iEMG(max) and an increase in blood lactate (p< or =0.05). As a result of the drop in repetitions performed in successive sets, it was concluded that training with 100% 10RM while exercising to failure in each set may not optimise the training volume, which may have implications for chronic muscle adaptation.

Adult↗
PubMed2005

Biotinylated fluorescent peptide substrates for the sensitive and specific determination of cathepsin D activity.

Cathepsin D (CatD) is a member of the mammalian aspartic protease family and is involved in cellular protein degradation and in several pathological processes. A sensitive and specific assay for the determination of CatD activity in biological samples was developed. The peptide amide substrates Amca-EDKPILF downward arrowFRLGK(biotin)-CONH2 (I), Amca-EEKPIC(Acm)F downward arrowFRLGK(biotin)-CONH2 (II) and Amca-EEKPISF downward arrowFRLGK(biotin)-CONH2 (III) contain a CatD cleavage site (F downward arrowF) flanked by a N-terminal Amca-fluorophore (7-amino-4-methylcoumarin-3-acetic acid) and a C-terminal biotin moiety. Substrates II and III proved to be specific substrates containing only one cleavage site for CatD. After cleavage of the Phe-Phe bond by CatD all biotin conjugated peptides were removed with streptavidin-coated magnetic beads. The remaining fluorescent peptides in solution represent the amount of digested substrate. The versatility of this CatD digest and pull down assay was demonstrated by measuring the activity of CatD in different subcellular fractions of human EBV-transformed B cells and human monocytes. The described method based on the designed CatD substrates represents a valuable tool for routine assays.

Amino Acid Sequence↗
PubMed2004

Human B lymphoblastoid cells contain distinct patterns of cathepsin activity in endocytic compartments and regulate MHC class II transport in a cathepsin S-independent manner.

Endocytic proteolysis represents a major functional component of the major histocompatibility complex class II antigen-presentation machinery. Although transport and assembly of class II molecules in the endocytic compartment are well characterized, we lack information about the pattern of endocytic protease activity along this pathway. Here, we used chemical tools that visualize endocytic proteases in an activity-dependent manner in combination with subcellular fractionation to dissect the subcellular distribution of the major cathepsins (Cat) CatS, CatB, CatH, CatD, CatC, and CatZ as well as the asparagine-specific endoprotease (AEP) in human B-lymphoblastoid cells (BLC). Endocytic proteases were distributed in two distinct patterns: CatB and CatZ were most prominent in early and late endosomes but absent from lysosomes, and CatH, CatS, CatD, CatC, and AEP distributed between late endosomes and lysosomes, suggesting that CatB and CatZ might be involved in the initial proteolytic attack on a given antigen. The entire spectrum of protease activity colocalized with human leukocyte antigen-DM and the C-terminal and N-terminal processing of invariant chain (Ii) in late endosomes. CatS was active in all endocytic compartments. Surprisingly and in contrast with results from dendritic cells, inhibition of CatS activity by leucine-homophenylalanine-vinylsulfone-phenol prevented N-terminal processing of Ii but did not alter the subcellular trafficking or surface delivery of class II complexes, as deferred from pulse-chase analysis in combination with subcellular fractionation and biotinylation of cell-surface protein. Thus, BLC contain distinct activity patterns of proteases in endocytic compartments and regulate the intracellular transport and surface-delivery of class II in a CatS-independent manner.

Antigen Presentation↗
PubMed1983

Circadian changes in the response of the rabbits retina to flashes.

It was previously shown that in rabbits the electroretinogram (ERG) and the visually evoked potential show a circadian rhythm consisting of a stable phase during which the animals respond to flashes with day time potentials and another phase with night time potentials (NTPs) and that the occurrence of the sharp phase transitions is programmed by the time course of the preceding light-dark schedule. From the present investigation it follows that photic sensitivity to flashes is markedly higher during the NTP-phase than in the other phase, whereas dark adaptation runs the same time course in both phases. With respect to the ERG it appears that, over a wide range of flash intensities its b wave only is affected by phase of the rhythm. The differences in photic responses between the 2 phases are discussed in the light of possibly synchronous changes in the influence of sympathetic nerve fibres on eye structures.

Animals↗
PubMed1981

Evidence for the existence of a retino-hypothalamo-retinal loop in rabbits.

Rabbits which have previously been exposed to 24-h light/dark alternations exhibit in their photic responses at all levels of the visual pathway, and in the electroretinogram, simultaneous circadian changes with a time course that is programmed by the preceding light/dark schedule. The occurrence of simultaneous changes in the response of the visual cortex to electrical stimulation at subcortical levels could not be established. After bilateral sectioning of the optic nerves, there were still changes in the electroretinogram which were now no longer programmed, but reflected the existence of a free-running rhythm. Bilateral sectioning of the cervical sympathetic nerves resulted in a complete absence of circadian changes in photic responses. The results suggest the possible existence of a retino-hypothalamo-retinal loop by means of which the responses to photic stimuli on a given day are modulated according to the time course of the light/dark alternations on the immediately preceding day. The possible role of this feedback loop in the origin of animal photoperiodism is discussed.

Animals↗
PubMed1978

Treatment of frontal sinus mucoceles with the osteoplastic flap technique.

The osteoplastic flap technique for treating frontal sinus mucoceles is described. This procedure has the advantages of: being a direct approach, which allows exposure of the entire sinus, provides complete obliteration of the sinus to prevent recurrence of the sinus disease, and prevents blind curettage of any exposed dura mater; leaving no facial deformity after the operation; being a relatively atraumatic procedure with low morbidity and minimum postoperative care; and allowing simultaneous surgery on both frontal sinuses when indicated.

Adult↗
PubMed1978

Diurnal changes in the rabbit's visual evoked potential.

Rabbits that have been exposed to the natural cycles of day and night exhibit marked diurnal changes in the shape of their Visual Evoked Potential in constant environmental conditions. The results of exposure to artificial 24 hr light-dark cycles strongly suggest that it is the regular alternation of daylight and darkness which acts as the synchronizing "Zeitgeber" for the V.E.P. rhythm which exists after exposure to the natural cycles of day and night. It would seem further that the V.E.P. changes reflect a square-wave like rhythm in the sensitivity of the visual system to photic stimuli, in which the sensitivity is much higher at night than in the day-time. The probable importance of the diurnal V.E.P. rhythm for the occurrence of daily fluctuations in behaviour is discussed.

Animals↗
PubMed1978

Photoperiodic programming of diurnal changes in rabbit visual evoked potentials.

Rabbits which have been exposed for several weeks to the natural cycles of daylight and darkness, or to various fixed 24 hr light-dark alternations, exhibit in constant environmental conditions large diurnal changes in the shape of the Visual Evoked Potential. These changes run a square-wave like time course and seem to reflect a similar diurnal rhythm in the sensitivity of the visual system to photic stimuli. The relation between the durations of the two phases of the rhythm can, within wide limits, be changed by variations in length of the artificial or natural photoperiod. It further appears that after exposure to continuous illumination or darkness rabbits have either a free-running V.E.P. rhythm or no such rhythm at all. The probable importance of the diurnal changes in the visual system for the occurrence of seasonal fluctuations in behaviour is discussed.

Animals↗
PubMed1978

Seasonal fluctuations of the circadian changes in rabbit visual evoked potentials.

Two rabbits were exposed for more than a year to the natural cycles of daylight and darkness. At intervals of 2 months and less records were taken of the time course of the 24 hr rhythm appearing in constant conditions in their cortical flash-evoked responses. It appeared that the rhythm can be programmed as well by the natural light-dark alternations as by artificial cycles. In temperate zones this "natural programming" causes large seasonal fluctuations in the time course of the rhythm which reflects, over the major part of the year and with remarkable precision, the times of sunrise and sunset and, in consequence, the length of the day. The possible significance of fixing daylength temporarily in the nervous system is discussed in connection with Bünning's hypothesis on the causation of seasonal photoperiodism.

Animals↗