Hans A. Dahl

Fine structure of cilia in rat cerebral cortex.

SummaryCilia have been demonstrated on granular neurons and astroglial cells in the fascia dentata, a part of the hippocampal region, in the rat. Every granular cell seems to possess one cilium, which shows an 8+1 pattern in the greater part of its length. This 8+1 pattern is shown to result from the displacement of one peripheral doublet of a 9+0 cilium into the middle of the cilium. The neuronal cilia have a two-centriole basal organization, and fine rootlets radiate from the basal body proper into the cytoplasm. The possible function and significance of these cilia are discussed on the basis of earlier literature.

Actomyosin ATPase activity of middle ear muscles in the cat

SummaryWhen incubated for histochemical demonstration of actomyosin ATPase both the tensor tympani and the stapedius were found to contain two types of muscle fibres, one with high actomyosin ATPase activity, indicating a high speed of contraction, and one with low actomyosin ATPase activity, indicating a low speed of contraction. In the tensor tympani 59% and 41% of the muscle fibres had a high and low ATPase activity, respectively. The corresponding numbers in the stapedius muscle were 82% and 18%. These findings are discussed with reference to previous physiological and morphological studies.

The effect of polyvinyl alcohol and polyvinyl pyrrolidone on diffusion artifacts in lactate dehydrogenase histochemistry

SummaryThe effect of polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP), alone and in combination, on diffusion artifacts in histochemical incubations has been investigated using LDH as model enzyme. By measuring the amount of formazan in the medium at the end of the incubation it has been shown that both substances, but especially PVA, are effective in limiting diffusion. The significance of this is discussed in general as well as in relation to other procedures used to reduce diffusion artifacts.

On the cilium cell relationship in the adenohypophysis of the mouse.

SummaryThe 8+1 cilia previously reported in the adenohypophysis have been reinvestigated with special emphasis on their relation to the parent cell. In contrast to the fibril pattern which is remarkably constant, this relation shows great variation, supporting the hypothesis that the cilia are rudimentary.

Different effects of physical training on the morphology of motor nerve terminals in the rat extensor digitorum longus and soleus muscles.

SummaryThe morphology of nerve terminals in the rat extensor digitorum longus and soleus muscles was studied with light microscopy in 13-week-old male animals after 6 weeks of treadmill running and compared with data from untrained controls. The terminals were stained with methylene blue. Physical training tended to increase the area and length of the nerve terminals in relation to the corresponding muscle fiber diameter, and to reduce the density of nerve terminal varicosities, but significant differences between the trained group and the control group were obtained only in the extensor digitorum longus muscle. The different degrees of effect on the nerve terminals in the two muscles may be due to different abilities to respond to the training, but may also be due to differences in work load caused by the training. The effect of training on extensor digitorum longus junctions may reflect some transformation from fast to slow morphological characteristics.

Oxidative capacity of tissues contributing to thermogenesis in eider (Somateria mollissima) ducklings: changes associated with hatching

Summary1.The development of liver and skeletal muscle oxidative capacities during hatching of the common eider (Somateria mollissima) in the Arctic has been investigated by monitoring tissue cytochrome c oxidase activity.2.The specific activity of the liver enzyme did not change as the embryo underwent hatching, nor during subsequent growth of the duckling into adulthood.3.Thigh muscle enzyme specific activity increased by a factor of 3.4 during the 24 h prehatching period, remained elevated for at least 48 h after hatching, and then returned to the embryonic (−24 h) level in adults.4.Histochemically visualized NADH-tetrazolium reductase of a typical red thigh muscle, M. vastus lateralis, showed a distinct increase in activity as the hatching process progressed to completion.5.Electron microscopy of sectioned M. vastus lateralis revealed a dramatic increase in the density of the myofibrillar structure (number of mitochondrial profiles per unit area), and in the surface area of mitochondrial crista membranes in the course of the 48 h interval from 1 day prehatching to 1 day after hatching.6.The significance of these changes for the scaling of thermoregulatory heat generation in the newly hatched eider duckling is discussed.

Actomyosin ATPase activity in Atlantic hagfish muscles

SummaryIncubation for Ca++-activated myosin ATPase reveals three types of muscle fibres in m. parietalis of the Atlantic hagfish (Myxine glutinosa), while m. craniovelaris and m. longitudinalis linguae both contain one type of muscle fibres.The fast twitch white fibres of m. longitudinalis linguae and m. parietalis show relatively high ATPase activity, while the intermediate fibres of m. parietalis show low activity. Despite of being slow non-twitch, the superficial red fibres of m. parietalis and the fibres of m. craniovelaris show an ATPase activity even higher than that of the fast twitch muscle fibres.

Effect of training with different mechanical loadings on MyHC and GLUT4 changes

PURPOSE There is an inverse relationship between insulin sensitivity and percentage of myosin heavy chain IIx (MyHC IIx) isoform in sedentary, obese, and type 2 diabetic humans. How different exercise conditions may reduce the proportion of MyHC IIx and in parallel elevate glucose transporter 4 (GLUT4) content is interesting in a therapeutic setting. This study investigates the nature of exercise signals regulating MyHC gene switching and whether it is accompanied by GLUT4 changes. METHODS Thirty-two subjects performed high loading (60% of 1 repetition maximum [RM]) or low loading (30% of 1 RM) elbow extensions in a training apparatus and exercised three times per week for either 5 wk (low volume) or 8 wk (high volume). MyHC and GLUT4 contents in the musculus triceps brachii were measured by Western blotting pre- and posttraining and after 8 wk of detraining. RESULTS All training regimes resulted in MyHC IIx changes of similar magnitude, and differences in training volume had no effect on the outcome. The reduction in MyHC IIx content after high loading, high volume was similar to low loading, matching volume of training. Thus, there was no effect of training load on MyHC changes. GLUT4 increased more after high than low loading (P < 0.0.1). In addition, the larger increases in the GLUT4 were associated with the larger reductions in MyHC IIx content (r = -0.56, P < 0.01). Detraining returned GLUT4 to baseline, but MyHC IIx content was still higher than baseline (P < 0.01). CONCLUSION Magnitude of loading is not important for suppression of MyHC IIx but for increases in GLUT4 content. The GLUT4 content responded, however, more rapidly to detraining than the MyHC IIx and IIa isoforms.

Some effects of polyvinyl alcohol and polyvinyl pyrrolidone on the activity of lactate dehydrogenase and its isoenzymes

SummaryThe activity of Sigma type II LDH (containing all LDH isoenzymes), type VII (LDH 1) and type V (LDH 5) has been evaluated in 0.1 M phosphate buffer and 0.4 M tris-HCl buffer, both at pH 7.4, before and after addition of PVP and PVA. A slight reduction of reaction velocity occurred when PVP and PVA were added, probably because of the increased viscosity of the medium. More specifically, PVA seemed to reduce the LDH 1 activity in phosphate buffer, but it seemed to counteract, together with PVP, conformational changes due to tris-HCl buffer of high molarity. None of these effects were found to influence the results of section histochemistry, but it could be shown that PVA was able to reduce urea inhibition of LDH 5 in tris-HCl buffer.

Lengths of the external hip rotators in mobilized cadavers indicate the quadriceps coxa as a primary abductor and extensor of the flexed hip.

BACKGROUND The primary function of the external rotators of the hip is inadequately described. The descriptions for peak strength and stretch take no account of how these muscles change their length during normal movement. The latter relationship is known to greatly influence contraction forces and reflect moment arms. The aim of the present study was to indicate positions and directions for peak strength and stretch of piriformis and obturator internus (including the gemelli), collectively defined as the quadriceps coxa, by measuring their changes in length due to normal movements. METHODS Repeated measurements of muscle lengths and range of motions were acquired from dissected muscles on human cadaver hips. We measured at every 15° of flexion with and without adding end ab/adduction, rotations, and combinations thereof. Measurements were taken in three normal hips (1 female aged 59 years, 2 males aged 68 and 70 years) using a custom-engineered frame, electronic calipers, goniometer, and a string muscle model. Movement-lengthening relations were differentiated into movement-moment arm relations. FINDINGS The piriformis and obturator internus were maximally lengthened (35 and 30mm) by 105° flexion and 10° adduction and relaxed by extension and abduction. With significant moment arms for extension and abduction in the movement-lengthening range deduced as force-efficient, our findings indicate peak strength by extension and abduction at 60° to 90° flexed positions. INTERPRETATION This cadaver study indicates that the quadriceps coxa is a primary abductor and extensor from flexed positions, a strength function which may be of major importance in rising and propulsive motions.