Experimental hematotympanum--aspects to the tympanosclerosis development

The etiology of tympanosclerosis is very complex and has not been entirely clarified. In order to find out if blood could be a provoking factor and cause tympanosclerosis, the authors injected the blood into the ears of 32 guinea pigs. The animals were sacrificed at weekly intervals up to one month and the histological analysis of the temporal bones was performed. Their experiment has shown that mucosal changes, similar to those seen in the early stage of tympanosclerosis, can appear in a certain number of cases. As a result, they recommend the aspiration of blood from the middle ear cavity in the cases of middle ear trauma with hematotympanum. They recommend the same procedure for operations of the middle ear, which should be performed with adequate hemostasis to prevent possible tympanosclerosis development.     

Characteristics of the sound conduction in mammals in the aqueous medium

Experimental investigations of sound-conducting tracts in man, seals and dolphins are reviewed. Underwater hearing is considered in connection with anatomical, morphological, and functional features of species and ecological factors.     

Age-independent constancy of mineral contents in human vertebra and auditory ossicle

To elucidate age-related changes of mineral contents in human bones, element contents of human vertebrae and auditory ossicles were determined by inductively coupled plasma atomic-emission spectrometry. The cervical, thoracic, and lumbar vertebrae were removed from 12 vertebral columns. The mallei of auditory ossicle were removed from 27 cadavers. It was found that average relative contents (RCs) of calcium and phosphorus in cervical, thoracic, and lumbar vertebrae remained almost constant within ages ranging from 46 to 99 y. In addition, it was found that the RCs of calcium and phosphorus in men’s and women’s mallei remained constant within ages ranging from 40 to 98 yr. These results support the view that there is no significant agedependent change of mineral contents in human bones.     

Conduction of the cardiac impulse. 3. Characteristics of very slow conduction

The excitability of short segments (5–7 mm) of bundles of canine Purkinje fibers was depressed by exposure to 15–18 mM K⁺, to 15–18 mM K⁺ plus 5 x 10^-6 epinephrine or norepinephrine, to low K⁺, and to low Na⁺. The depressed segment was in the center chamber of a three-chamber bath; the ends of the bundle were exposed to normal Tyrode solution. Each method of depression resulted in slow and probably decremental conduction with an effective conduction velocity in the middle chamber of about 0.05 m/sec, or one-way block, or two-way block with summation of the graded responses in the depressed region. The action potential in the depressed segment (the slow response) differs from the normal action potential in its response to applied stimuli. A second active depolarization can be evoked by cathodal stimulation during much of the slow response. The response in the depressed segment is graded. The response of depressed fibers may depend on excitatory events similar to those responsible for the slow component of the cardiac action potential. It is suggested that the slow response can propagate, at least decrementally, in fibers in which the rapid, Na⁺-dependent upstroke is absent, and can cause reentrant excitation by so doing.     

Re-assessment of ossicle frequency patterns in sediment cores: rate of sedimentation related to Acanthaster planci

Data on Acanthaster planci skeletal element distribution in reefal subsurface sediment cores of two reefs of the central Great Barrier Reef (Walbran et al. 1989 a, b) were shown to be readily interpretable after a timescaled evaluation of element frequencies. After re-scaling using ¹⁴C bulk sediment ages, high frequencies of elements were recognized in the top layers of John Brewer Reef sediment cores and attributed to the two recent A. planci population outbreaks. Beneath these top layers, the subsurface sediments contain consistently low element frequencies down to bulk-sediment ages of 7750±100 years BP. From Green Island, the maximum abundance of skeletal elements was found in the sediment layers of about 1900 to 2300 years BP in some cores, but patterns were too inconsistent and the number of cores too small to suggest former A. planci outbreaks from these data. A strong correlation was found between the frequency of A. planci elements and the rate of sedimentation per time unit in sediment cores of all sites. This correlation was attributed to increased erosion of coral reefs as a consequence of the activities of high-density populations of A. planci. We conclude that reef erosion, after intense predation of reef-constructing organisms, has to be considered when causes of deterioriation of reef growth or termination of a reef facies in the geological past are discussed.     

Ear ossicle morphology of the Jurassic euharamiyidan Arboroharamiya and evolution of mammalian middle ear

The middle ear bones of Mesozoic mammals are rarely preserved as fossils and the morphology of these ossicles in the earliest mammals remains poorly known. Here, we report the stapes and incus of the euharamiyidan Arboroharamiya from the lower Upper Jurassic (～160 Ma) of northern China, which represent the earliest known mammalian middle ear ossicles. Both bones are miniscule in relation to those in non‐mammalian cynodonts. The skull length/stapedial footplate diameter ratio is estimated as 51.74 and the stapes length as the percentage of the skull length is 4%; both numbers fall into the stapes size ranges of mammals. The stapes is “rod‐like” and has a large stapedial foramen. It is unique among mammaliaforms in having a distinct posterior process that is interpreted as for insertion of the stapedius muscle and homologized to the ossified proximal (stapedial) end of the interhyal, on which the stapedius muscle attached. The incus differs from the quadrate of non‐mammalian cynodonts such as morganucodontids in having small size and a slim short process. Along with lack of the postdentary trough and Meckelian groove on the medial surface of the dentary, the ossicles suggest development of the definitive mammalian middle ear (DMME) in Arboroharamiya. Among various higher‐level phylogenetic hypotheses of mammals, the one we preferred places “haramiyidans” within Mammalia. Given this phylogeny, development of the DMME took place once in the allotherian clade containing euharamiyidans and multituberculates, probably independent to those of monotremes and therians. Thus, the DMME has evolved at least three times independently in mammals. Alternative hypothesis that placed “haramiyidans” outside of Mammalia would require independent acquisition of the DMME in multituberculates and euharamiyidans as well as parallel evolution of numerous derived similarities in the dentition, occlusion pattern, mandibles, cranium, and postcranium between the two groups and between “haramiyidans” and other mammals. J. Morphol. 279:441–457, 2018. © 2016 Wiley Periodicals, Inc.     

Characteristics of ATPase activity and the subunit composition of myosin in the conduction system of bovine heart

The ATPase activity, light chains and isoenzymes of myosin from specialized myocardial tissue (the A-V node, bundle of His, and right and left bundle branches) of bovine heart were compared with those of atrial and ventricular myosins. The order of Ca2+-activated ATPase activity was atrial greater than specialized myocardial tissue greater than ventricular myosin. SDS-polyacrylamide gel electrophoresis showed that myosin from the specialized myocardial tissue contained the light chains of both atrial and ventricular myosins. On the other hand, the specialized myocardial tissue contained one V3 isomyosin and showed no difference from ventricular myocardial tissue on pyrophosphate gel.     

Proton conduction in phosphatidylethanolamine

The dc conductivity of polycrystalline phosphatidylethanolamine (PE) was measured in the temperature range 60–120°C. Since no conclusive evidence had so far been obtained for the presence of proton conduction in this phospholipid, hydrogen gas was shown in the present experiment to evolve during the electrolysis in its premelted state between 91 and 124°C. In this temperature range molecules assume rotation around the molecular axes and proton conduction of the Grotthus type takes place possibly along two chains of intermolecular hydrogen bonds running in parallel. Zwitter-ions behave cooperatively as proton donors and acceptors in transferring proton from molecule to molecule via the hydrogen bond networks. This efficient push-pull way of proton transferring seems to account for the fact that no polarization was observed in the dc conduction experiments. The amount of evolved gas appears to be not exactly in accordance with Faraday's law and discussions are made on possible causes for this slight deviation.     

Ossicle change in Holothuria scabra with a discussion of ossicle evolution within the Holothuriidae (Echinodermata)

Ossicles of Holothuria (Metriatyla) scabra Jaeger 1833 vary mainly in early juveniles between 0.9 and 15mm long. While ossicles were not observed in auricularia and doliolaria larvae, which instead possessed elastic balls, ossicles were present in late pentactulae. Specimens 0.9–1.5mm long have tables with tall spire (4–5 cross beams), no buttons, and large irregular perforated plates. Specimens 5–6mm long have tables with moderate spire (2–4 cross beams) and a few smooth buttons. Specimens 9–16mm long have tables with low spire (1–2 cross beams) and knobbed buttons. From 30mm, ossicle are similar to those of adults, with more buttons and fewer tables. Several features of the ossicles of early juveniles, including their size, shape and prevalence, are unique to the species. Comparison with holothurian juveniles of other species indicates that presence of tables with tall spire and absence of buttons are plesiomorph characters in the evolution of the Holothuriidae.     

Nerve conduction in childhood diabetes

Sixty-nine diabetic children were studied with respect to the motor nerve conduction velocities, duration of illness and adequacy of control.As a group there was a trend for children with diabetes to have slower MNCV than non-diabetic children, and for the slowing to become progressive as the duration of their disease increased. Poorer quality of diabetes control was also associated with progressive slowing of conduction but the exact relationship is uncertain, since no patient who had diabetes for more than four years was well controlled.Theories of causation of peripheral neuropathy in diabetic patients are reviewed; metabolic changes, rather than other factors, are thought most likely in children.     

The conduction of sap

Summary Experiments are described in which the uptake of water by leaves exposed to severe water stress (80–95% R. W. C.) was found to deviate markedly from those of leaves with smaller water deficits. In its most extreme form the deviation appears as a curious increase in rate of water absorption some time after uptake has commenced. It could not be detected during the absorption of water by leaf discs suffering comparable severe water deficits.It is suggested that the differences are caused by cavitation in the xylem conducting channels during wilting. On restoring a water supply the reverse process takes place causing unusual patterns of water uptake.Since restoration takes place at 1° C it appears that metabolism is not involved; the process is physical in character.     

Bistable nerve conduction

It has been demonstrated experimentally that slow and fast conduction waves with distinct conduction velocities can occur in the same nerve system depending on the strength or the form of the stimulus, which give rise to two modes of nerve functions. However, the mechanisms remain to be elucidated. In this study, we use computer simulations of the cable equation with modified Hodgkin-Huxley kinetics and analytical solutions of a simplified model to show that stimulus-dependent slow and fast waves recapitulating the experimental observations can occur in the cable, which are the two stable conduction states of a bistable conduction behavior. The bistable conduction is caused by a positive feedback loop of the wavefront upstroke speed, mediated by the sodium channel inactivation properties. Although the occurrence of bistable conduction only requires the presence of the sodium current, adding a calcium current to the model further promotes bistable conduction by potentiating the slow wave. We also show that the bistable conduction is robust, occurring for sodium and calcium activation thresholds well within the experimentally determined ones of the known sodium and calcium channel families. Since bistable conduction can occur in the cable equation of Hodgkin-Huxley kinetics with a single inward current, i.e., the sodium current, it can be a generic mechanism applicable to stimulus-dependent fast and slow conduction not only in the nerve systems but also in other electrically excitable systems, such as cardiac muscles.     

Transcallosal conduction in paroxysmal kinesigenic dyskinesia

Objectives: Detecting whether a possible disequilibrium between the excitatory and inhibitory interhemispheric interactions in paroxysmal kinesigenic dyskinesia (PKD) exists.

Methods: This study assessed measures of motor threshold, motor evoked potential latency, the cortical silent period, the ipsilateral silent period and the transcallosal conduction time (TCT) in PKD patients. Data were compared between the clinically affected hemisphere (aH) and the fellow hemisphere (fH).

Results: The transcallosal conduction time from the aH to the fH was 11.8?ms (range?=?2.3–20.7) and 13.6?ms (range?=?2.8–67.7) from the fH to the aH. The difference in TCT in the affected side was significant (p?=?.019).

Conclusion: The findings demonstrated that, although inhibitory interneurons act normally and symmetrically between the motor cortices and transcallosal inhibition was normal and symmetrical between both sides, the onset of transcallosal inhibition was asymmetrical. The affected hemisphere’s inhibition toward the unaffected hemisphere is faster compared to the inhibition provided by the fellow hemisphere. These results are consistent with an inhibitory deficit in the level of interhemispheric interactions.

Significance: This study revealed a defect in inhibition of the motor axis could be responsible in the pathological mechanisms of kinesigenic dyskinesia.