Tyrosine hydroxylase and serotonin containing cells in embryonic rat rhombencephalon: a whole-mount immunocytochemical study

Rhombencephala from rat embryos were processed as whole-mounts for immunocytochemical detection of monoaminergic cell populations, using antibodies to tyrosine hydroxylase (TH) and serotonin (5-HT). Specific advantages of the whole-mount technique over the classical serial-section method were that even isolated immunoreactive (IR) cells could be detected easily, and three-dimensional relationships could be ascertained without the need for serial reconstruction. Embryos between embryonic days (E) 12 and 16 (the day following nocturnal mating being considered as E1) were used in this study. Both TH and 5-HT immunoreactivities were already detectable at E12, even in the smallest embryos (crown-rump length: 6 mm), but there was a striking difference in the number and regional distribution of these two types of IR cells. TH was expressed in several cell groups located in the rostral rhombencephalon (the presumed anlage of the A4-7 complex) as well as in the caudal rhombencephalon (the presumed anlagen of groups A1-2 and C1-3), whereas 5-HT was expressed in very few cells located near the rostral border of the rhombencephalon (presumed anlage of the B4-9 complex). Although the three-dimensional distribution of the TH-IR cell groups underwent some modifications during the period studied, its general pattern remained relatively stable after E12. This contrasted with the sequential appearance of the 5-HT-IR cell groups and their spatial transformations during this period. Using the rhombencephalic isthmus as a landmark, we found that conspicuous 5-HT-IR fibre bundles penetrated into the mesencephalon from E13 onwards, but that the 5-HT IR cell bodies were exclusively located caudal to the borderline between the mesencephalon and the rhombencephalon (the rhombencephalic isthmus). We therefore suggest the term "rostral rhombencephalic raphe nuclei" for the rostral 5-HT cell groups instead of "mesencephalic raphe nuclei," which is a misnomer. Close spatial association between TH and 5-HT-IR elements was observed mainly in the caudal rhombencephalon, where 5-HT-IR fibres coursed through an area containing numerous TH-IR cell bodies (the presumed anlagen of groups A1-2 and C1-3).     

The depressing effect of tetracaine and ryanodine on the slow outward current correlated with that of contraction in voltage-clamped frog muscle fibres

The effects of tetracaine (10–50 M) and ryanodine (0.1–10 M) were tested on the slow outward K⁺ current (I _so) and the mechanical tension of isolated frog muscle fibres in a voltage-clamp device (double mannitol-gap) connected to a mechanoelectric transducer. In the concentration range tested, both drugs induced a simultaneous inhibition of tension and current. In all cases the effect on tension was twice that on current. The tetracaine-induced current and tension blocks were fully reversible and dose-dependent. In contrast the ryanodine effects on current and tension were not reversible and did not exhibit a dose dependence except for the delay before the onset of the response, which was shortened when the concentration was raised. Linear regression analysis of the time-dependent and dose-dependent effects of both drugs indicated a strong correlation between the decreases in tension and current. It is concluded that the slow outward current is partly under the control of the Ca²⁺ release from sarcoplasmic reticulum during contraction.     

Maintenance of targeting errors by isthmo-optic axons following the intraocular injection of tetrodotoxin in chick embryos.

We have studied the role of electrical activity in the elimination of axonal targeting errors, which is a normal process in brain development. The experiments were focused on the isthmo-optic nucleus (ION), which, in adults, projects in topographical order on the contralateral retina. During embryogenesis, however, a few isthmo-optic neurons project to the ipsilateral retina, and many project to topographically inappropriate parts of the contralateral one; both kinds of targeting error are known to be eliminated by the deaths of the parent neurons. We injected tetrodotoxin (TTX) intraocularly at embryonic days 13 and 15 and, on the latter, applied a retrograde label to the retina of the same eye. Embryos were fixed at embryonic day 17. In some embryos, the label was a peripherally placed fleck of the carbocyanine dye "diI"; the resulting retrogradely labeled neurons in the contralateral ION were much more widely scattered in the TTX-injected embryos than in controls (errors in topography). In other embryos, the label was a solution of rhodamine-B-isothiocyanate (RITC) injected into the vitreous body; this yielded several ipsilaterally labeled isthmo-optic neurons in the TTX-injected embryos, but virtually none in the controls. The numbers of both kinds of aberrantly projecting neuron approached those previously reported near the beginning of the ION's period of neuronal death. We conclude that electrical activity plays an important role in the elimination of axonal targeting errors in the chick embryo's isthmo-optic system.     

The effect of design of residential homes in creating dependency among confused elderly residents: A study of elderly demented residents and their ability to find their way around homes for the elderly

A study of 13 homes for elderly people examining the effect of the environment on demented residents looked into the complexity of the design from the residents' point of view. Two principal tools were used in this investigation: ‘route diagrams’, which describe a resident's use of the home, and a measure devised to indicate each resident's ability to find her way around the home. These are described and the relationship between them explored. From this the following tentative conclusions are drawn:

• (i) The variables that influence a resident's ability to find her way around differ between group and communally designed homes.
• (ii) It would appear that group homes provide a more favourable design, especially in the case of physically frail demented elderly people.
• (iii) In group homes, the level of lighting is an important aid to a demented person in finding her way around.
• (iv) In communal homes, residents seem most able to find their way around homes that have been adapted from older premises.
• (v) In both types of home, ‘meaningful decision points’ can be seen as aids to a resident finding her way around.

     

Plateau potentials evoked by climbing-fibre stimulation are restricted to the Purkinje cell dendrites of the cat

The present study investigated the duration of afterdepolarizations in Purkinje cell somata following climbing-fibre activation. Intracellular recordings revealed that, in cells with membrane potentials more negative than -50 mV and with normal spike-generating capabilities, climbing-fibre activation resulted in somatic responses with short afterdepolarizations. As the cell deteriorated and the resting membrane potential became more positive, the duration and form of the climbing-fibre response resembled the plateau potentials recorded from proximal dendrites. The absence of plateau potentials in undamaged Purkinje cell somata was confirmed by extracellular recording of test spike amplitudes following evoked climbing-fibre responses.     

Intermediate filament expression in human vascular smooth muscle and in arteriosclerotic plaques

Summary Different regions of human aorta and of other human arteries obtained at autopsy were analyzed with regard to their topography and to the different stages of arteriosclerosis. Material was studied by immunocytochemical techniques with antibodies specific for either desmin (D) or for vimentin (V), the two types of intermediate filament proteins present in vascular smooth muscle cells. In normal arteries endothelial cells as well as the adjacent intimal cells were D–V+. In the media D+V+ as well as D–V+ cells were present, with the relative numbers of each cell type dependent on the particular blood vessel. When cells in arteriosclerotic plaques at different stages of development were examined an occasional plaque showed cells of the D+V+ type. In the majority of plaques however the cells were V– D+. In plaques where severe ulceration and necrotic material was present D–V+ cells were found at the border of the lesion: foam cells when they could be identified appeared to be D–V+.     

Intramuscular pressure,EMG and blood flow during low-level prolonged static contraction in man

Seven men performed one-legged isometric knee-extension at 5% MVC for 1 h. Intramuscular pressure increased with contraction from its resting value of 14 (2–31) mmHg. Some intramuscular pressure recordings stayed at an almost constant level throught the 1 h contraction, but most recordings showed large fluctuations from resting values up to 90 mmHg. The overall mean intramuscular pressure was twice the resting value. In some cases, EMG recordings confirmed that the changes in intramuscular pressure were related to alternating recruitment of various parts of the knee-extensors. Blood flow in the femoral vein increased within 3 min of 5% MVC to a level of 1.58 (1.25-2.22) 1 min^-1 and no significant changes occurred during the 1 h contraction. In two subjects blood flow was measured also in the recovery period, and this decreased almost immediately when the muscle relaxed. It is concluded that during low-level static contractions, the blood supply to the exercising muscle is maintained at a sufficiently high level, and that the alternating recruitment of muscle fibres may result in a heterogeneously distributed blood flow within the contracting muscle. Despite this the muscle was fatigued after the 1 h at 5 % MVC. The rating of perceived exertion (RPE) increased from 1.9 (1–3) at the beginning to 4.5(2–8) at the end of contraction, and MVC was decreased by 12% after the contraction.     

Spectral analysis of spontaneous contractions of the isolated portal vein of rats

Summary The spontaneous contractions of segments of rat portal veins have been examined in vitro under isotonic and isometric conditions. The power density spectra of recorded time series lasting 10–60 min were calculated. The spectra usually consist of harmonic frequency components. Only during shorter periods of analysis (10 min time series) we sometimes found additional non-harmonic components. All frequency components are proportionally shifted by changes of the bath temperature according to an average Q₁₀ of 2.0. Increase of the load decreases the frequency of the contractions.The results of the spectral analysis, indicating a preponderance of a single source of periodicity, were supported by direct evidence of a pacemaker region. By recording contractions after systematic dissections of the portal vein segment, we found that spontaneous activity is generated at the central end of the segment.This work was supported by the Austrian Research Fund     

Changes in fibre-type composition and myosin heavy-chain IId isoform in rat soleus muscle during recovery period after hindlimb suspension

We examined the changes in myosin heavy-chain (HC) isoforms and fibre-type composition in rat soleus muscle using both myosin adenosine triphosphatase staining and sodium dodecyl sulphate/polyacrylamide gel electrophoresis (SDS-PAGE) analyses during the recovery period after 4 weeks of hindlimb suspension. Although there was no change in type IIc fibres after the suspension, an increase in this type of fibres was observed during the 1- to 4-week recovery period. The increase in type Ilc fibres was considered to be due to a shift from type Ila to IIc fibres. The SDS-PAGE analysis revealed the presence of the HC IId isoform, which was not observed in the control muscle, after a 4-week hindlimb suspension. The HC IId isoform gradually decreased over 3 weeks of recovery and disappeared in the 4th week of recovery after the suspension. These results suggest that the hypogravity conditions induced by hindlimb suspension stimulated the synthesis of the HC IId isoform, whereas an increase in mechanical load to the muscle accelerated the degradation of the HC IId isoform and the synthesis of type Ilc fibres during the recovery period after hindlimb suspension.     

Effect of different types of high carbohydrate diets on glycogen metabolism in liver and skeletal muscle of endurance-trained rats

Male Wistar rats were fed ad libitum four different diets containing fructose, sucrose, maltodextrins or starch as the source of carbohydrate (CH). One group was subjected to moderate physical training on a motor-driven treadmill for 10 weeks (trained rats). A second group received no training and acted as a control (sedentary rats). Glycogen metabolism was studied in the liver and skeletal muscle of these animals. In the sedentary rats, liver glycogen concentrations increased by 60%–90% with the administration of simple CH diets compared with complex CH diets, whereas skeletal muscle glycogen stores were not significantly affected by the diet. Physical training induced a marked decrease in the glycogen content in liver (20%–30% of the sedentary rats) and skeletal muscle (50%–80% of the sedentary rats) in animals fed simple (but not complex) CH diets. In liver this was accompanied by a two-fold increase of triacylglycerol concentrations. Compared with simple CH diets, complex CH feeding increased by 50%–150% glycogen synthase (GS) activity in liver, whereas only a slight increase in GS activity was observed in skeletal muscle. In all the animal groups, a direct relationship existed between tissue glucose 6-phosphate concentration and glycogen content (r = 0.9911 in liver, r = 0.7177 in skeletal muscle). In contrast, no relationship was evident between glycogen concentrations and either glycogen phosphorylase activity or adenosine 5-monophosphate tissue concentration. The results from this study thus suggest that for trained rats diets containing complex CH (compared with diets containing simple CH) improve the glycogenic capacity of liver and skeletal muscle, thus enabling the adequate regeneration of glycogen stores in these two tissues.