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L Walloe

Publications and source records attributed to L Walloe.

At least 19 recordsLinked to original sources
PubMed2000

On the direction and velocity of blood flow in the extradural intravertebral vein of harp seals (Phoca groenlandica) during simulated diving.

Ronald et al. (1977) suggested that blood flow in the caudal/lumbar sections of the extradural intravertebral vein (EIV) of seals changes direction from running towards the head before diving, to the opposite during diving. The possible advantage would be that the oxygen-depleted venous effluent from the brain is routed via the EIV to the posterior parts of the hepatic sinuses and the inferior caval vein and, hence, is prevented from mixing with the more oxygen-rich venous blood in their anterior parts. We have re-examined this hypothesis by use of Doppler flowmetry. A catheter-tip flow probe was introduced into the EIV of two similar-sized juvenile harp seals, and flow direction and rate determined before, during and after simulated dives lasting for 5 min, at three positions (caudal, lumbar and thoracic) along the EIV. Regardless of probe position, blood was mainly flowing towards the head in 11 of 13 experiments prior to diving, in 8 of 13 experiments during diving and in 11 of 13 experiments during recovery after diving (and away from the head in the remaining experiments). Flow direction was most variable in the caudal position. Mean blood velocity in the EIV was substantially lower during diving (0.10 +/- 0.22 cm s-1 (n=5) in thoracic position) than in the pre-dive (3.98 +/- 3.32 cm s-1 [n=5]) and post-dive (5.75 +/- 4.07 cm s-1 [n=5]) situations. Thus, the direction and rate of flow in the EIV was variable, particularly during diving, as is to be expected in a system of anastomosing, valveless veins. We conclude that the hypothesis of Ronald et al. (1977) most likely is false.

Animals↗
PubMed1986

[Not Available].

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Demography↗
PubMed1976

Menarcheal age in Norway in the 19th century: a re-evaluation of the historical sources.

A fall in the age of menarche during the last fifty years is well documented from many parts of the world, among them Norway. Tanner says that this trend can be extended back at least to the middle of the last century, and he uses Norwegian sources to support this hypothesis. Re-examination of these Norwegian sources indicates that there was no fall at all during the ninetheenth century, and that the age at menarche was constant at approximately 16.0 years for the lower social classes throughout this period. It is also suggested that the age at menarche was constant at approximately 14 years for the higher social classes.

Adolescent↗
PubMed1975

Reflex inhibition of the slowly adapting stretch receptors in the intact abdomen of the crayfish.

The reflex inhibition of abdominal stretch receptors in crayfish was studied by controlled passive flexion of individual abdominal joints. The results are very similar to those obtained by electrical or mechanical stimulation of individual stretch receptors in immobilized abdomens. Reflex effects from posterior to anterior abdominal segments are somewhat stronger than in the opposite direction. Flexion of one abdominal joint excites the stretch receptors of that joint and inhibits the stretch receptors in neighbouring abdominal segments. Without reflex inhibition flexion of one abdominal joint excites the stretch receptors in several abdominal segments.

Action Potentials↗
PubMed1970

On the transmission of information through sensory neurons.

Information about muscle length is transmitted to the cerebellum from muscle spindle receptors through the dorsal spinocerebellar tract (DSCT). The "transinformation" about muscle length in single DSCT fibers was calculated from steady-state spike trains by two different methods, assuming that the decoding mechanisms use a frequency code. By the first method, the number of distinguishable muscle lengths (and thus the transiformation) was determined from the rate of convergence of the mean frequency of firing (with increasing number of intervals). The observation time necessary to estimate the mean frequency of the impulse train with a certain accuracy was independent of the stretch level, even though the number of intervals necessary to make this estimate was different at high and low levels of stretch. By the second method an input frequency-output frequency matrix was calculated. The transinformations and the rate of transinformation was then calculated from this matrix. There was an acceptable agreement in the estimates of transinformation by the two methods. The rates of transinformation are significantly increased by the particular time structure of the discharge patterns of the nerve cells. Consequently, the loss of information due to the synaptic coupling is appreciably reduced.

Action Potentials↗