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Start dating in Schwabach today! Sign up in 30 seconds and meet someone. Nurenberg Personal Ads macporto. Coming from the magic Douro river that surround the unbeaten city of Porto, land of warriors, musicians and poets. As Viriathus and Sertorius, the people of Lusus, a people predestined by the Fates Online Dating in Nürnberg ScreedGather. Just to start somehow and see where it goes This electric current creates action potentials within the connected afferent neurons.
OHCs are different in that they actually contribute to the active mechanism of the cochlea. They do this by receiving mechanical signals or vibrations along the basilar membrane, and transducing them into electrochemical signals. The stereocilia found on OHCs are in contact with the tectorial membrane. Therefore, when the basilar membrane moves due to vibrations, the stereocilia bend. The direction in which they bend, dictates the firing rate of the auditory neurons connected to the OHCs.
The bending of the stereocilia towards the basal body of the OHC causes excitation of the hair cell. Thus, an increase in firing rate of the auditory neurons connected to the hair cell occurs. On the other hand, the bending of the stereocilia away from the basal body of the OHC causes inhibition of the hair cell. Thus, a decrease in firing rate of the auditory neurons connected to the hair cell occurs.
OHCs are unique in that they are able to contract and expand electromotility. Therefore, in response to the electrical stimulations provided by the efferent nerve supply, they can alter in length, shape and stiffness. These changes influence the response of the basilar membrane to sound. The active mechanism is dependent on the cochlea being in good physiological condition.
However, the cochlea is very susceptible to damage. Firstly, the entire hair cell might die. Secondly, the stereocilia might become distorted or destroyed. Damage to the cochlea can occur in several ways, for example by viral infection, exposure to ototoxic chemicals, and intense noise exposure. Damage to the OHCs results in either a less effective active mechanism, or it may not function at all. Thus, damage to the OHCs results in the reduction of sensitivity of the basilar membrane to weak sounds.
Amplification to these sounds is therefore required, in order for the basilar membrane to respond efficiently. However, if they become damaged, this will result in an overall loss of sensitivity.
The traveling wave along the basilar membrane peaks at different places along it, depending on whether the sound is low or high frequency. Due to the mass and stiffness of the basilar membrane, low frequency waves peak in the apex, while high frequency sounds peak in the basal end of the cochlea. These specifically tuned frequencies are referred to as characteristic frequencies CF.
If a sound entering the ear is displaced from the characteristic frequency, then the strength of response from the basilar membrane will progressively lessen. The fine tuning of the basilar membrane is created by the input of two separate mechanisms. The first mechanism being a linear passive mechanism, which is dependent on the mechanical structure of the basilar membrane and its surrounding structures.
The second mechanism is a non-linear active mechanism, which is primarily dependent on the functioning of the OHCs, and also the general physiological condition of the cochlea itself. The base and apex of the basilar membrane differ in stiffness and width, which cause the basilar membrane to respond to varying frequencies differently along its length. The base of the basilar membrane is narrow and stiff, resulting in it responding best to high frequency sounds.
The apex of the basilar membrane is wider and much less stiff in comparison to the base, causing it to respond best to low frequencies. This selectivity to certain frequencies can be illustrated by neural tuning curves.
These demonstrate the frequencies a fiber responds to, by showing threshold levels dB SPL of auditory nerve fibers as a function of different frequencies. This demonstrates that auditory nerve fibers respond best, and hence have better thresholds at the fiber's characteristic frequency and frequencies immediately surrounding it.
This shape shows how few frequencies a fiber responds to. However, where there is partial or complete damage to the OHCs, but with unharmed IHCs, the resulting tuning curve would show the elimination of sensitivity at the quiet sounds. However, due to IHC damage, the whole tuning curve becomes raised, giving a loss of sensitivity across all frequencies See Figure 6.
This supports the idea that the incidence of OHC damage and thus a loss of sensitivity to quiet sounds, occurs more than IHC loss. Dead regions can be defined in terms of the characteristic frequencies of the IHC, related to the specific place along the basilar membrane where the dead region occurs. Assuming that there has been no shift in the characteristic frequencies relating to certain regions of the basilar membrane, due to the damage of OHCs.
This often occurs with IHC damage. Dead regions affect audiometric results, but perhaps not in the way expected. For example, it may be expected that thresholds would not be obtained at the frequencies within the dead region, but would be obtained at frequencies adjacent to the dead region.
Therefore, assuming normal hearing exists around the dead region, it would produce an audiogram that has a dramatically steep slope between the frequency where a threshold is obtained, and the frequency where a threshold cannot be obtained due to the dead region.
However, it appears that this is not the case. Dead regions cannot be clearly found via PTA audiograms. This may be because although the neurons innervating the dead region, cannot react to vibration at their characteristic frequency. If the basilar membrane vibration is large enough, neurons tuned to different characteristic frequencies such as those adjacent to the dead region, will be stimulated due to the spread of excitation. Therefore, a response from the patient at the test frequency will be obtained.
This will lead to a false threshold being found. Thus, it appears a person has better hearing than they actually do, resulting in a dead region being missed. Therefore, using PTA alone, it is impossible to identify the extent of a dead region See Figure 7 and 8. Consequently, how much is an audiometric threshold affected by a tone with its frequency within a dead region?
This depends on the location of the dead region. Thresholds at low frequency dead regions, are more inaccurate than those at higher frequency dead regions. This has been attributed to the fact that excitation due to vibration of the basilar membrane spreads upwards from the apical regions of the basilar membrane, more than excitation spreads downwards from higher frequency basal regions of the cochlea.
If the tone is sufficiently loud to produce enough excitation at the normally functioning area of the cochlea, so that it is above that areas threshold. The tone will be detected, due to off-frequency listening which results in a misleading threshold. To help to overcome the issue of PTA producing inaccurate thresholds within dead regions, masking of the area beyond the dead region that is being stimulated can be used.
This means that the threshold of the responding area is sufficiently raised, so that it cannot detect the spread of excitation from the tone. Based on research it has been suggested that a low frequency dead region may produce a relatively flat loss, or a very gradually sloping loss towards the higher frequencies. As the dead region will be less detectable due to the upward spread of excitation.
Whereas, there may be a more obvious steeply sloping loss at high frequencies for a high frequency dead region.
Although it is likely that the slope represents the less pronounced downward spread of excitation, rather than accurate thresholds for those frequencies with non-functioning hair cells. PTCs are similar to neural tuning curves. They illustrate the level of a masker dB SPL tone at threshold, as a function of deviation from center frequency Hz. The masker level is varied, so that the level of masker needed to just mask the test signal is found for the masker at each center frequency.
The tip of the PTC is where the masker level needed to just mask the test signal is the lowest. For normal hearing people this is when the masker center frequency is closest to the frequency of the test signal See Figure 9. In the case of dead regions, when the test signal lies within the boundaries of a dead region, the tip of the PTC will be shifted to the edge of the dead region, to the area that is still functioning and detecting the spread of excitation from the signal.
In the case of a low frequency dead region, the tip is shifted upwards indicating a low frequency dead region starting at the tip of the curve.
For a high frequency dead region, the tip is shifted downwards from the signal frequency to the functioning area below the dead region. However, more research to validate this method is required, before it can be accepted clinically.
Audiogram configurations are not good indicators of how a dead region will affect a person functionally, mainly due to individual differences. However, the individual may well be affected differently from someone with a corresponding sloped audiogram caused by partial damage to hair cells rather than a dead region. They will perceive sounds differently, yet the audiogram suggests that they have the same degree of loss. Huss and Moore investigated how hearing impaired patients perceive pure tones, and found that they perceive tones as noisy and distorted, more on average than a person without a hearing impairment.
However, they also found that the perception of tones as being like noise, was not directly related to frequencies within the dead regions, and was therefore not an indicator of a dead region. There is an enhancement in the ability to distinguish between tones that differ very slightly in frequency, in regions just beyond the dead regions compared to tones further away.
An explanation for this may be that cortical re-mapping has occurred. Whereby, neurons which would normally be stimulated by the dead region, have been reassigned to respond to functioning areas near it. This leads to an over-representation of these areas, resulting in an increased perceptual sensitivity to small frequency differences in tones. Presbycucis is the leading cause of SNHL and is progressive and nonpreventable, and at this time, we do not have either somatic or gene therapy to counter heredity-related SNHL.
But other causes of acquired SNHL are largely preventable, especially nosocusis type causes. This would involve avoiding environmental noise, and traumatic noise such as rock concerts and nightclubs with loud music.
Use of noise attenuation measures like ear plugs is an alternative, as well as learning about the noise levels one is exposed to. Currently, several accurate sound level measurement apps exist.
Reducing exposure time can also help manage risk from loud exposures. Treatment modalities fall into three categories: As SNHL is a physiologic degradation and considered permanent, there are as of this time, no approved or recommended treatments. So I fired off a short Letter to the Editor that essentially suggested in so many words that from an evolutionary perspective the bacteria were doing exactly what they were supposed to do — extract energy from otherwise useless dietary ingredients for their host.
After all, our track record as a species when it comes to creating unintended consequences from tweaking ecological systems — in which the human gut is one — is not good. Despite the dire warnings in that second letter, I would argue — 6 years on — that the publication of that article in the New York Times Magazine along with the years of research that formed its content, encouraged tens of millions in additional research dollars in human-microbe interactions that has resulted in the most significant advances in our understanding of human health and disease of any previous decade in human history.
And that includes our understanding of obesity. Building on that earlier research and utilizing many of the genomic and analytical tools that were either completely created in the last decade or greatly improved upon, researchers in labs all over the world are unraveling the role of the gut microbes in the pathogenesis of obesity.
But a year-old man that wondered into a microbial lab at the Shanghai Jiao Tong University in Shanghai, China in that may have provided a critical border piece to the puzzle that scientists are methodically filling in. The researchers would soon discover, at five-foot eight and pounds, this morbidly obese man from the Shanxi Province was carrying a pathogen that was likely contributing to his obesity.
Following his initial visit to the university, the year-old was asked to join a study the researchers were conducting. Based on the initial evaluation the man agreed to a new diet composed of whole grains, traditional Chinese medicine and prebiotics. This cuisine was provided in four, carefully made and weighed cans that were consumed daily. In all, only 1, calories a day! Starting with Day 1, and continuing every few days for 23 weeks, the researchers collected the standard data like height, weight, and blood pressure in addition to blood, urine and stool samples.
It was the ratio of Firmicutes to Bacteroidetes that first tipped researchers off that bacteria play some role in obesity that was reported on in that New York Times Magazine article. So the researchers kept an eye on this particular genus over the course of the 23 weeks to see what happened. He had shed an astounding pounds. At only 1, calories a day, this was definitely a calorie-restriction diet. Accompanying the weight loss was a normalizing of his triglycerides, total cholesterol, fasting plasma glucose and insulin, and so on — all of this despite the fact that he still weighed pounds and had a BMI of But one of the most intriguing changes at the end of the 23 weeks was the abundance of Enterobacter.
While the abundance of other bacteria went either up or down over the 23 weeks, the changes were minor. The researchers wondered if this shift had something to do with his initial weight gain, and subsequent weight loss. That is, were the Enterobacter contributing or causing the obesity, or were they a result of it? Classic causation versus correlation. The genus Enterobacter — and many other members of the Enterobacteriaceae family for that matter — are significant producers of lipopolysaccharide LPS endotoxins.
LPS is the primary structural component of the outer membrane of Gram-negative bacteria like Enterobacter. Numerous studies have shown that if endotoxins translocate leak from the gut into serum blood , they can cause low-grade inflammation that can contribute to obesity and insulin-resistance think type 2 diabetes. When the researchers looked at the serum-endotoxin load from Day 1 to Week 23, they noticed a sharp drop.
They also noted a substantial improvement in inflammation, as measured by several biomarkers in the blood. So, as the abundance of Enterobacter dropped over the 23 weeks, so did the LPS load and inflammation. In addition, the researchers also conducted a more in-depth shotgun metagenomic analysis of his stool samples, which reveals the genes present with his microbial community Note: This allowed them to measure the LPS biosynthetic pathway — that is, the metabolic endotoxin-producing capacity of his entire gut microbial system, across all the bacteria.
As expected, and in keeping with the reduction of the big endotoxin producing Enterobacter throughout the 23 weeks, the overall metabolic output of LPS from the system i. So whether it was something in the new diet, or something removed by discontinuing the old diet, his microbiome shifted in a significant way and system-wide inflammation had been greatly reduced in the process as the endotoxin load went down.
A match came back for Enterobacter cloacae subsp. For ease, B29 became its new name. Once they isolated B29, they grew bunch of them in the lab and prepared to inject them in germ free mice. Previous research has shown that germ free mice fed a high fat diet HFD resisted weight gain, but when inoculated with bacteria in their gut , they would gain weight. In other words, the bacteria played some role in the weight gain.
In these previous studies the mice were often injected with a cocktail of bacteria, represented numerous species. The researchers took a group initially 14 in total, but a few died along the way of genetically identical mice and split them into two equal groups.
One group was fed NCD diet and was inoculated with one trillion B29 cells our Enterobacter strain , and the other group was fed a HFD and inoculated with the same number of B29 cells. The researchers also tested a group of mice using another single-strain strategy, this time with Bifidobacterium animalis.
Using the same diets, neither group HFD or NCD inoculated with the single strain became obese demonstrating that obesity cannot be induced by just any bacteria under a HFD. The specific species or strain of bacteria is important.
In other words, higher levels of LPS endotoxins in your gut does not mean you will have elevated levels in you blood, which increases inflammation that is associated with insulin resistance and obesity. And since the B29 was the only microbe in the mice, then the inflammation-causing LPS endotoxins could have only come from the gut. But how did the endotoxins get from the gut into the blood, and why was this most pronounced during a high fat diet, even though a normal chow diet produced greater numbers of endotoxins in the gut — and presumably a larger source pool of endotoxins that could end up in the blood?