Biomedical subjects

B Ulfhake

Publications and source records attributed to B Ulfhake.

81 records · Page 5Linked to original sources

PubMed1984

Electrophysiological and morphological measurements in cat gastrocnemius and soleus alpha-motoneurones.

Intracellular recording and staining with HRP was used to study the electrical properties and anatomical size of medial gastrocnemius (MG) and soleus (SOL) alpha-motoneurones in curarized cats. The MG motoneurones were divided into two groups on the basis of their input resistance (RN), namely low-resistance MG-LR cells (RN less than 1.0 M omega) and high-resistance MG-HR cells (RN greater than 1.0 M omega). Analysis of the voltage transients following applied current pulses indicated that the SOL neurones had longer membrane time constants (tau o) than the MG-LR cells, while the MG-HR group exhibited intermediate values. Using Rall's equivalent cylinder model, a difference in specific membrane resistivity (Rm) between the MG-LR (low Rm) and SOL (high Rm) cells was obtained. This difference was observed also in neurones of similar anatomical size, and was consistent with the observed difference in tau o. In two neurones Rm was in addition calculated directly from anatomy and input resistance according to the general solution for a continuous neurone model with arbitrary geometry given by Rall. The latter method was found to yield significantly lower values for Rm, although the observed difference between the neurone types remained similar. Also the values for electrotonic length (L) were found to differ considerably between the calculations based on voltage transient analysis and those obtained from combined physiological and anatomical measurements. The observed variations in results are discussed in relation to possible sources of error in the experimental techniques and/or in the theoretical assumptions, particularly that of Rm being uniform over the entire soma-dendritic membrane. It is suggested that Rm might be larger in the dendritic regions than in the soma. A crude approximation of the dendrite to soma conductance ratio (Q) indicated that most cells (80%) had Q greater than 5.

Action Potentials↗

PubMed1984

A morphometric study of the soma, first-order dendrites and proximal axon of cat lumbar alpha-motoneurones intracellularly labelled with HRP.

Intracellularly HRP-labelled cat hindlimb alpha-motoneurones were reconstructed light microscopically from a series of 1 micron or 2 micron thick consecutive sections. The volume and surface area of the soma as well as the size of the very proximal part of the dendritic and axonal processes were estimated morphometrically. Similar measurements were also made on adjacent unlabelled neurons in the same series of sections. A close relation was found between the soma volume and surface area on one hand the combined cross-sectional area of the proximal dendrites and axon on the other. The combined axonal and dendritic bases occupied on the average 16% of the soma surface. The accuracy in using the diameters and cross-sectional area of the cell body as indirect estimates of soma volume and surface area was analyzed. Combined measurements in both the transversal and sagittal planes were then found to yield more satisfactory estimates then when the measurements were confined only to the transversal plane. Several different formulas using the soma axes for indirect calculations of the soma volume and surface area were compared with respect to the accuracy of the results.

Animals↗

PubMed1983

A quantitative morphological study of HRP-labelled cat alpha-motoneurones supplying different hindlimb muscles.

Cat alpha-motoneurones supplying the quadriceps (Q), posterior biceps (PB), gastrocnemius (G), soleus (SOL) and short intrinsic plantar foot (SP) muscles were studied after retrograde or intracellular labelling with HRP. The average soma sizes were rather similar for the different pools, the SOL cells being the smallest. The median number of first-order dendrites ranged from 10 (PB) to 12 (SOL). The median diameters of the first-order dendrites ranged from 6 (SOL) to 8.5 (PB, G) micrometer. The dendritic projection patterns were rather similar for the different motoneurone groups, except for a prominent dorsomedial projection of SP dendrites. A considerable fraction of the dendrites extended into the white matter. The diameter of the first-order dendrite correlated positively to the number of end branches as well as to the combined length, surface area and volume of the whole dendrite. These relations appeared to be independent of motoneurone group and dendritic orientation. The combined diameter of the first-order dendrites, which reflects the total dendritic size of a motoneurone, exhibited median values between 82 micrometers (SOL) and 112 micrometers (Q). With respect to the relative scaling of soma and dendrites, motoneurones with large somas tended to have proportionally larger dendritic trees. The distribution of dendritic diameters, number of branches, dendritic surface area and volume, and the combined dendritic parameter (epsilon d3/2) at various distances from the soma were quite similar for the different motoneurone groups.

Animals↗

PubMed1982

Does alpha-motoneurone size correlate with motor unit type in cat triceps surae?

The cell bodies and first-order dendrites of alpha-motoneurones supplying different functional types of muscle units in the cat gastrocnemius (type FF, FR and S units) and soleus (type SOL-S units) muscles, were studied after intracellular injection of horseradish peroxidase. The SOL-S neurones had smaller values for cell body diameter in comparison with both the FF and FR neurones. The SOL-S neurones also had significantly thinner first-order dendrites than the FF, FR and S neurones. In the gastrocnemius pool the S neurones had smaller values for dendritic diameters than the FF and FR cells. The values for combined diameter of the first-order dendrites indicated that the dendritic trees of the FF and FR neurones are, on the average, larger than those of the S and SOL-S neurones. Furthermore, the relationship between the combined dendritic diameter and the mean soma diameter, indicated that a difference in relative scaling of soma and dendrites exists between the FF and FR neurones on the one hand and the S and SOL-S neurones on the other. Similar results were obtained also when relating the combined dendritic parameter sigma d3/2 to the soma surface area. Although a certain statistical relation seems to exist between motoneurone size and motoneurone type, it should be emphasized, however, that the range of values for each parameter studied overlapped considerably between the different types of motoneurones.

Animals↗

PubMed1982

Evidence for a postnatal elimination of terminal arborizations and synaptic boutons of recurrent motor axon collaterals in the cat.

Triceps surae alpha motoneurons in cats of different postnatal ages were stained intracellularly with horseradish peroxidase (HRP). The recurrent axon collateral trees of the neurons were studied light microscopically. A large reduction of the number of axon collateral end branches and swellings, interpreted as synaptic boutons, was found to occur during the first two weeks of postnatal life.

Aging↗

PubMed1981

A quantitative light microscopic study of the dendrites of cat spinal alpha-motoneurons after intracellular staining with horseradish peroxidase.

The cell bodies and dendrites of cat spinal alpha-motoneurons were studied after intracellular staining with horseradish peroxidase. The mean diameter of the soma was positively correlated to both the mean diameter and the combined diameter of the first-order dendrites, but not to the number of first-order dendrites. On the average, 11.2 dendrites originated from the soma. The dendritic trees were more extensive than has been described previously. The mean value for the combined length of a whole dendrite was 4.7 mm, while the mean values for the total surface area and volume of a dendrite were 33.0 x 10(3) micron (2) and 27.2 x 10(3) micron (3), respectively. The diameter of the first-order dendrite was positively correlated to the combined length of the entire dendrite, the number of dendritic branching points, and the number of dendritic end branches. The diameter of the first-order dendrite was also directly proportional to the volume and the surface area of the entire dendrite. About 75% of the dendritic surface area and 55% of the dendritic volume was located more than 300 micron away from the soma. The dendrites constituted about 97% of the surface area and about 75% of the volume of the entire motoneuron (excluding the axon). The dendritic tapering was moderate. On the average, the distal decrease in dendritic diameters caused a reduction in the combined dendritic parameter (sigma d 3/2) by 1.5% and 15% at 500 micron and 800 micron distance, respectively, from the soma.

Animals↗

PubMed1981

A quantitative light microscopic study of the dendrites of cat spinal gamma -motoneurons after intracellular staining with horseradish peroxidase.

By use of intracellular staining with horseradish peroxidase (HRP), the dendritic systems of spinal gamma-motoneurons of the adult cat were studied with a light microscope. The dendrites extended in various directions up to 1.5 mm from the cell body. The dendritic branching was sparse and even unbranched dendrites were occasionally seen. The number and combined diameter of the first-order dendrites increased in parallel with the mean cell body diameter. The number of dendritic end branches, the combined dendritic length, the membrane surface area, and the volume of the entire dendrite correlated positively with the diameter of the parent first-order dendrite. In comparison with the alpha -motoneurons (Ulfhake and Kellerth, '81) the gamma -motoneurons had smaller values for mean cell body diameter and mean diameter of the first-order dendrites and they also had a smaller number of first-order dendrites. The dendrites of the gamma-motoneurons were also found to have fewer branching points and larger values for combined dendritic length. The relation between the diameter of the first-order dendrite and the surface area of the entire dendrite was almost identical for the two types of motoneurons.

Animals↗

PubMed1979

Relations between cell body size, axon diameter and axon conduction velocity of triceps surae alpha montoneurons during the postnatal development in the cat.

Triceps surae alpha-motoneurons in cats of different postnatal ages were stained intracellularly with horseradish peroxidase (HRP) and studied light microscopically. In individual neurons, the mean diameter of the cell body and the intramedullary axon diameter were measured and related to the axon conduction velocity. The mean diameter of the cell body grew from 39.6 micrometer at birth to 57.6 micrometer in the adult cat, while the corresponding figures for the intramedullary axon diameters were 2.4 micrometer and 6.7 micrometer. During the same period of time, the axon conduction velocity increased from 11.3 m/s to 93.5 m/s, and the ratio between the conduction velocity and the intramedullary diameter of the axon (CV/d ratio) increased from 4.6 to 14.1. The results indicate that the growth of the cell body is smaller and completed earlier than the growth in diameter of the intramedullary and, in particular, the peripheral parts of the axon. The considerable change of the CV/d ratio during the postnatal development may be explained by previously described immature morphological properties of the axons in very kittens, and by a changing relation between the dimensions of the intramedullary and peripheral parts of the axon.

Animals↗

PubMed1979

Observations on the morphology of intracellularly stained gamma-motoneurons in relation to their axon conduction velocity.

Hindlimb gamma-motoneurons of adult cats were stained intracellularly with horseradish peroxidase. The gamma-motor-axons had intramedullary diameters between 2.0 micron and 2.4 micron and lacked recurrent collaterals. The conduction velocity of the gamma-motor-axons (20-29 m/sec) was close to what could be predicted from the relationship between conduction velocity and intramedullary diameter of much thicker adult alpha-motor-axons. However, the gamma-motor-axons were conducting much faster than alpha-motor-axons of 1-week-old kittens in spite of the fact that these two types of axons had about the same dimensions intramedullarly.

Age Factors↗