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PubMed1974

Adaptation of the discharge of frog muscle spindles following a stretch.

1. Stretching a frog muscle spindle evoked a discharge of action potentials in its sensory axon. As the rate of this discharge decreased during the adaptation that followed the dynamic phase of a stretch, the variability of the interspike intervals of the impulse train increased.2. Adaptation occurred in two phases. At first the impulse train was almost regular and adapted rapidly, but later this gave way to a phase of slower adaptation where the variability of the discharge was much increased. In the second phase of adaptation the interspike intervals increased in length less than half as quickly as in the first phase.3. When the rate of adaptation changed from the more rapid to the slower phase there was often an abrupt change in the character of the discharge and the relationship between the mean interspike interval and the variability changed. The interspike interval at which this change-over occurred was relatively constant in records of the discharge from one afferent fibre even though stretches of different amplitude were employed, though it differed from one afferent fibre to another.4. These features of the discharge during adaptation suggest that the two sections of the impulse trains were derived from different spike generators by a process of probabilistic mixing.

Action Potentials↗

PubMed1975

Intracellular recordings of rod responses during dark-adaptation.

1. Dark-adaptation of rod photoreceptors has been studied in the isolated axolotl (Ambystoma mexicanum) retina by intracellular recordings. Rod responsiveness was greatly reduced immediately after a 30 sec partial bleach, but partially recovered with time in the dark. 2. In parallel spectrophotometric measurements using isolated retinas, regeneration of the rod pigment could not be detected after a 30 sec bleach. 3. During rod dark-adaptation, the response of a rod to a given stimulus increased in amplitude, duration, and rate of rise but did not recover completely to the dark-adapted values. Response latency was lengthened immediately after a bleach but ultimately returned to the dark-adapted level. 4. The time courses of dark-adaptation determined on the basis of the intensity of a stimulus needed to evoke a response having a criterion amplitude, a criterion duration, or a criterion rate of rise were similar. On the other hand changes in latency of the response and magnitude of the saturated amplitude followed different time courses. Change in log threshold was found to be related to change in saturated amplitude by an exponential function during dark-adaptation. 5. After bleaching 10% or less of the rod pigment, the kinetics of both recovery of log threshold and decrease in absorbance at 400 nm (metarhodopsin II+free retinal) could be described by two concurrent first-order processes having similar time constants. However, after bleaching more than 10% of the rod pigment, changes in sensitivity and absorbance did not follow parallel time courses. 6. Metarhodopsin III cannot be solely responsible for setting the axolotl rod sensitivity since rod thresholds decrease monotonically during dark-adaptation whereas meta III concentration reaches a peak 3 min after the bleach and decreases thereafter.

Ambystoma↗

PubMed1977

The dynamics of the pi 1 colour mechanism: further evidence for two sites of adaptation.

1. The visual pathway that determines Stiles's Pi(1) colour mechanism was isolated by the auxiliary field technique and studied under dynamic conditions of light adaptation and recovery by threshold measurements.2. The time courses of adaptation to Pi(1)-equated short wave-length (mu </= 500 nm) and long wave-length (mu >/= 550 nm) fields are very distinct: a large and relatively long-enduring transient threshold elevation occurs at the onset of the long wave-length, but not of the short wave-length fields.3. Similarly, the time courses of recovery from Pi(1)-equated long and short wave-length fields are quite distinctive: a large and relatively long enduring transient (;transient tritanopia') occurs at the offset of the long wave-length, but not of the short wave-length fields.4. The wave-lengths of the fields which cause the adaptation transients coincide with those shown previously (Pugh, 1976) to combine non-additively with mu = 430 nm fields in effecting Pi(1) adaptation. The failure of the time course of Pi(1) adaptation to be spectrally ;univariant' combines with the failures of field-additivity to demonstrate that signals from the long and/or middle wave-length sensitive cones affect the adaptation state of the Pi(1) pathway.5. The adaptation transients are not observed in the pathways that determine Pi(4) and Pi(5). Thus, instantaneous signals from the middle and/or long wave-length sensitive cones are not the cause of the transients. Rather the cause must lie in the path by which those cones transmit their signals to the Pi(1) pathway or in the Pi(1) pathway itself.6. The off-transient can be diminished by adding an adequately intense short wave-length field to a long wave-length field that would normally cause it. The Pi(1) pathway must receive chromatically opponent signals.

Adaptation, Ocular↗

PubMed1978

Modification by previous afferent discharge of the adaptation of frog muscle spindles following an extension.

1. Extension of a frog muscle spindle evoked a discharge of impulses in its sensory axon. The adaptation of the discharge after the dynamic phase of stretching occurred in two phases. At first the impulse train was almost regular and adapted quickly, but later this gave place to a phase of slower adaptation in which the variability of discharge was much increased. 2. The discharge of action potentials by the muscle spindle depressed the response of the receptor to a subsequent extension. This was true whether they were elicited antidromically by afferent stimulation or orthodromically by longitudinal vibration. This depression had its most marked effect on the first phase of adaptation where it greatly increased the rate of adaptation. The second, slower, phase of adaptation was little influenced. 3. The depression increased with the duration and with the frequency of afferent stimulation. It persisted for about 300 msec. 4. The results show that the properties of the spike generating mechanisms in the muscle spindle are modified by previous discharge and that this modification may influence the overall properties of the receptor. 5. The fact that afferent stimulation has different effects on the two phases of adaptation is consistent with the suggestion that the impulse train evoked by extension is derived from more than one spike generator within the muscle spindle.

Action Potentials↗

PubMed1989

Activation and adaptation of transducer currents in turtle hair cells.

1. Transducer currents were recorded in turtle cochlear hair cells during mechanical stimulation of the hair bundle. The currents were measured under whole-cell voltage clamp in isolated cells that were firmly stuck to the floor of the recording chamber. 2. Stimuli were calibrated by projecting the image of the hair bundle onto a rapidly scanned 128 photodiode array. This technique showed that, while the cell body was immobilized, the tip of the bundle would follow faithfully the motion of an attached glass probe up to frequencies of more than 1 kHz. 3. The relationship between inward transducer current and bundle displacement was sigmoidal. Maximum currents of 200-400 pA were observed for deflections of the tip of the bundle of 0.5 microns, equivalent to rotating the bundle by about 5 deg. 4. In response to a step deflection of the bundle, the current developed with a time constant (about 0.4 ms for small stimuli) that decreased with the size of displacement. This suggests that the onset of the current was limited by the gating kinetics of the transduction channel. The onset time course was slowed about fourfold for a 20 degrees C drop in temperature. 5. For small maintained displacements, the current relaxed to about a quarter of the peak level with a time constant of 3-5 ms. This adaptation was associated with a shift of the current-displacement relationship in the direction of the stimulus. The rate and extent of adaptation were decreased by lowering external Ca2+. 6. Adaptation was strongly voltage sensitive, and was abolished at holding potentials positive to the reversal potential of the transducer current of about 0 mV. It was also diminished by loading cells with 10 mM of the Ca2+ chelator BAPTA. These observations suggest that adaptation may be partly controlled by influx of Ca2+ through the transducer channels. 7. Removal of adaptation produced asymmetric responses, with fast onsets but slow decays following return of the bundle to its resting position; the offset time course depended on both the magnitude and duration of the prior displacement. 8. In some experiments, hair bundles were deflected with a flexible glass fibre whose motion was monitored using a dual photodiode arrangement. Positive holding potentials abolished adaptation of the transducer currents, but had no influence on the time course of motion of the fibre. We have no evidence therefore that adaptation is caused by a mechanical reorganization within the bundle.

Adaptation, Physiological↗

PubMed1993

Differences in adaptation between on- and off-centre ganglion cells and rod-mediated cone sensitization in cat retina.

1. Response properties of on- and off-centre retinal ganglion cells were investigated in cats. The stimulus parameters were selected so as to demonstrate interactions between the rod and the cone systems. 2. Response versus log stimulus intensity (R-log I) functions were determined for the receptive field centres while both test stimulus irradiance and the background illumination were varied over a range up to 7 log units. In order to determine the course of adaptation to chromatic stimuli, threshold versus intensity (t.v.i.) functions were measured over a wide range of adaptation levels. 3. An increase in background illuminance produced a shift of the R-log I functions to higher irradiances of test stimuli in most ganglion cells, indicating a desensitization of the centre response in the presence of background lights. Using test stimuli which most efficiently stimulate the rods (501 nm), clear differences could be seen in the adaptation behaviour of on- and off-centre ganglion cells. Chromatic backgrounds (blue-green and orange) reduced the responses of off-centre cells more than those of on-centre cells (the difference between them amounting to as much as 2 log units). Simultaneously, equivalent t.v.i. functions had significantly steeper slopes (0.94 and 1.1) in the linear proportions of off-centre cells compared to on-centre cells (0.76 and 0.75) under light levels mediated by rods. Such differences were not observed when a test stimulus of 575 nm was used which resulted primarily in stimulating the long-wavelength cone (L-cone) system. 4. In a subpopulation of off-centre cells (20% of the total number of off-centre cells recorded), a strikingly different adaptation behaviour was observed. Here, the presentation of a dim short-wavelength background produced a shift of R-log I functions to lower test stimulus irradiances. The receptive field centre became even more sensitive, by up to 1.5 log units, in the presence of dim adapting backgrounds rather than in the dark-adapted state. Accordingly, the t.v.i. function did not increase monotonically but showed a 'dip' in the presence of dim backgrounds. Only at photoic levels, the t.v.i. functions revealed a response behaviour similar to the other ganglion cells. The sensitization with dim backgrounds was only observed in the case of test stimuli designed to stimulate the cone system (575 nm) and in the presence of a rod-adapting blue-green background.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗

PubMed1983

Time course of adaptation and recovery of channels selectively sensitive to frequency and amplitude modulation.

In a series of experiments we investigated the time course of adaptation and recovery of channels in the human auditory system selectively sensitive to frequency and amplitude modulation (FM and AM). We determined the rate of loss of sensitivity to modulation using sinusoidal frequency or amplitude modulation (SFM or SAM) of a 50 dB SL, 500-Hz pure tone carrier over a 30-min period. Adaptation stimuli were modulated at ten times the preadaptation modulation detection threshold, as determined immediately before the 30-min adaptation session. Modulation rates investigated were 2, 4, 8, 16, and 32 Hz. Long exposure to SFM always elevated thresholds for detection of SFM more than this exposure elevated thresholds for detection of SAM. Similarly, adapting to SAM always elevated SAM detection thresholds more than SFM thresholds. Loss of sensitivity during adaptation was relatively slow; asymptotic loss of modulation sensitivity took 20 to 30 min. The recovery of modulation sensitivity after cessation of the modulation component of the adapting stimulus was determined in a second experiment. Recovery was found to be rapid; most of the recovery occurred within the first 60 sec. Our evidence suggests that there exist two types of modulation-sensitive channels in the human auditory system--one selectively sensitive to amplitude modulation and the other to frequency modulation. They appear to have similar time courses for adaptation and for recovery.

Adaptation, Physiological↗

PubMed1999

Constrained adaptation for feedback cancellation in hearing aids.

In feedback cancellation in hearing aids, an adaptive filter is used to model the feedback path. The output of the adaptive filter is subtracted from the microphone signal to cancel the acoustic and mechanical feedback picked up by the microphone, thus allowing more gain in the hearing aid. In general, the feedback-cancellation filter adapts on the hearing-aid input signal, and signal cancellation and coloration artifacts can occur for a narrow-band input. In this paper, two procedures for LMS adaptation with a constraint on the magnitude of the adaptive weight vector are derived. The constraints greatly reduce the probability that the adaptive filter will cancel a narrow-band input. Simulation results are used to demonstrate the efficacy of the constrained adaptation.

Adaptation, Physiological↗

PubMed2006

Adaptive resistance and differential protein expression of Salmonella enterica serovar Enteritidis biofilms exposed to benzalkonium chloride.

The development of adaptive resistance of Salmonella enterica serovar Enteritidis ATCC 4931 biofilms following exposure to benzalkonium chloride (BC) either continuously (1 microg ml(-1)) or intermittently (10 microg ml(-1) for 10 min daily) was examined. Biofilms adapted to BC over a 144-h period could survive a normally lethal BC challenge (500 microg ml(-1) for 10 min) and then regrow, as determined by increases in biofilm thickness, total biomass, and the ratio of the viable biomass to the nonviable biomass. Exposure of untreated control biofilms to the lethal BC challenge resulted in biofilm erosion and cell death. Proteins found to be up-regulated following BC adaptation were those involved in energy metabolism (TpiA and Eno), amino acid and protein biosynthesis (WrbA, TrxA, RplL, Tsf, Tuf, DsbA, and RpoZ), nutrient binding (FruB), adaptation (CspA), detoxification (Tpx, SodB, and a probable peroxidase), and degradation of 1,2-propanediol (PduJ and PduA). A putative universal stress protein (YnaF) was also found to be up-regulated. Proteins involved in proteolysis (DegQ), cell envelope formation (RfbH), adaptation (UspA), heat shock response (DnaK), and broad regulatory functions (Hns) were found to be down-regulated following adaptation. An overall increase in cellular protein biosynthesis was deduced from the significant up-regulation of ribosomal subunit proteins, translation elongation factors, and amino acid biosynthesis protein and down-regulation of serine endoprotease. The cold shock response, stress response, and detoxification are suggested to play roles in the adaptive resistance of Salmonella serovar Enteritidis biofilms to BC.

Adaptation, Physiological↗

PubMed1987

Effect of adaptation to phenol on biodegradation of monosubstituted phenols by aquatic microbial communities.

The adaptation of a mixed aquatic microbial community to phenol was examined in microcosms receiving phenol as a sole carbon source. Extended exposure (adaptation) to phenol resulted in adaptation of the microbial community to the structurally related aromatic compounds m-cresol, m-aminophenol, and p-chlorophenol. The increased biodegradation potential of the phenol-adapted microbial community was accompanied by a concurrent increase in the number of microorganisms able to degrade the three test compounds. Thus, adaptation to the three test chemicals was likely a growth-related result of extended exposure to phenol. The results indicate that adaptation to a single chemical may increase the assimilative capacity of an aquatic environment for other related chemicals even in the absence of adaptation-inducing levels of those materials.

Adaptation, Physiological↗

PubMed1991

Adaptation of Streptococcus mutans and Enterococcus hirae to acid stress in continuous culture.

Streptococcus mutans GS-5 and IB1600 adapted to growth in acidic environments in continuous culture at slow (generation time = 8.3 h) or fast (generation time = 2.4 h) rates of growth in complex medium with a restricted glucose supply. The extent of adaptation was indicated by changes in minimum pH values attained by harvested cells suspended in dense suspensions with excess glucose and by increased levels of ATPase activity assayed in permeabilized cells. Also, adapted cells better withstood potentially lethal acidification. Cells harvested from cultures growing at pH values close to 5 reduced suspension pH to lower values than cells from cultures maintained at pH 7. Cells from pH 6 cultures were intermediate. The IB1600 strain had a higher level of constitutive acid resistance than the GS-5 strain and also was better able to adapt to growth in acidified media. Both had less adaptive capacity than Enterococcus hirae ATCC 9790. Adaptation occurred rapidly, mainly within a single generation in continuous culture, while deadaptation occurred more slowly over multiple generations. The capacity of S. mutans to adapt to acid conditions is likely to be important in the ecology of dental plaque and also for the cariogenicity of the organism.

Adaptation, Physiological↗

PubMed1997

Acid adaptation sensitizes Salmonella typhimurium to hypochlorous acid.

Acid adaptation of Salmonella typhimurium at a pH of 5.0 to 5.8 for one to two cell doublings resulted in marked sensitization of the pathogen to halogen-based sanitizers including chlorine (hypochlorous acid) and iodine. Acid-adapted S. typhimurium was more resistant to an anionic acid sanitizer than was its nonadapted counterpart. A nonselective plating medium of tryptose phosphate agar plus 1% pyruvate was used throughout the study to help recover chemically stressed cells. Mechanisms of HOCl-mediated inactivation of acid-adapted and nonadapted salmonellae were investigated. Hypochlorous acid oxidized a higher percentage of cell surface sulfhydryl groups in acid-adapted cells than in nonadapted cells, and sulfhydryl oxidation was correlated with cell inactivation. HOCl caused severe metabolic disruptions in acid-adapted and nonadapted S. typhimurium, such as respiratory loss and inability to restore the adenylate energy charge from a nutrient-starved state. Sensitization of S. typhimurium to hypochlorous acid by acid adaptation also involved increased permeability of the cell surface because nonadapted cells treated with EDTA became sensitized. The results of this study establish that acid-adapted S. typhimurium cells are highly sensitized to HOCl oxidation and that inactivation by HOCl involves changes in membrane permeability, inability to maintain or restore energy charge, and probably oxidation of essential cellular components. This study provides a basis for improved practical technologies to inactivate Salmonella and implies that acid pretreatment of food plant environments may increase the efficacy of halogen sanitizers.

Acids↗

PubMed2001

Proteins induced during adaptation of Acetobacter aceti to high acetate concentrations.

As a typical product of microbial metabolism, the weak acid acetate is well known for its cytotoxic effects. In contrast to most other microbes, the so-called acetic acid bacteria can acquire significant resistance to high acetate concentrations when properly adapted to such hostile conditions. To characterize the molecular events that are associated with this adaptation, we analyzed global protein expression levels during adaptation of Acetobacter aceti by two-dimensional gel electrophoresis. Adaptation was achieved by using serial batch and continuous cultivations with increasing acetate supplementation. Computer-aided analysis revealed a complex proteome response with at least 50 proteins that are specifically induced by adaptation to acetate but not by other stress conditions, such as heat or oxidative or osmotic stress. Of these proteins, 19 were significantly induced in serial batch and continuous cultures and were thus noted as acetate adaptation proteins (Aaps). Here we present first microsequence information on such Aaps from A. aceti. Membrane-associated processes appear to be of major importance for adaptation, because some of the Aap bear N-terminal sequence homology to membrane proteins and 11 of about 40 resolved proteins from membrane protein-enriched fractions are significantly induced.

Acetates↗

PubMed2006

Effects of endogenous substrates on adaptation of anaerobic microbial communities to 3-chlorobenzoate.

Lengthy adaptation periods in laboratory studies evaluating the potential for contaminant biodegradation in natural or engineered environments may indicate that the native microbial communities are not metabolizing the contaminants in situ. In this study, we characterized the adaptation period preceding the biodegradation of 3-chlorobenzoate in anaerobic communities derived from lake sediment and wastewater sludge digesters. The importance of alternative mechanisms of adaptation of the anaerobic communities to 3-chlorobenzoate was evaluated by monitoring the concentrations of metabolic substrates and products as well as the levels of total small subunit (SSU) rRNA and SSU rRNA from populations thought to be important in 3-chlorobenzoate mineralization. The anaerobic environments from which the 3-chlorobenzoate-degrading communities were derived contained different levels of endogenous substrates. Increasing methane levels in the digester and sediment communities and decreasing chemical oxygen demand concentrations in the sediment community during the adaptation periods revealed that endogenous substrates were preferentially utilized relative to 3-chlorobenzoate. Methane and chemical oxygen demand concentrations leveled off concomitantly with the onset of 3-chlorobenzoate biodegradation, suggesting that depletion of the preferentially degraded endogenous substrates stimulated 3-chlorobenzoate metabolism. Consistent with these observations, adaptation to 3-chlorobenzoate occurred more rapidly in digester samples that were depleted of endogenous substrates compared to samples that contained high levels of these biodegradable compounds. Other potential adaptation mechanisms, e.g., genetic change or selective population enrichment, appeared to be less important based on the reproducibility and relative lengths of the adaptation events, trends in the SSU rRNA levels, and/or amplification of SSU rRNA genes from key populations.

Adaptation, Physiological↗

PubMed1998

Chemotactic adaptation is altered by changes in the carboxy-terminal sequence conserved among the major methyl-accepting chemoreceptors.

In Escherichia coli and Salmonella typhimurium, methylation and demethylation of receptors are responsible for chemotactic adaptation and are catalyzed by the methyltransferase CheR and the methylesterase CheB, respectively. Among the chemoreceptors of these species, Tsr, Tar, and Tcp have a well-conserved carboxy-terminal motif (NWET/SF) that is absent in Trg and Tap. When they are expressed as sole chemoreceptors, Tsr, Tar, and Tcp support good adaptation, but Trg and Tap are poorly methylated and supported only weak adaptation. It was recently discovered that CheR binds to the NWETF sequence of Tsr in vitro. To examine the physiological significance of this binding, we characterized mutant receptors in which this pentapeptide sequence was altered. C-terminally-mutated Tar and Tcp expressed in a receptorless E. coli strain mediated responses to aspartate and citrate, respectively, but their adaptation abilities were severely impaired. Their expression levels and attractant-sensing abilities were similar to those of the wild-type receptors, but the methylation levels of the mutant receptors increased only slightly upon addition of attractants. When CheR was overproduced, both the adaptation and methylation profiles of the mutant Tar receptor became comparable to those of wild-type Tar. Furthermore, overproduction of CheR also enhanced adaptive methylation of wild-type Trg, which lacks the NWETF sequence, in the absence of any other chemoreceptor. These results suggest that the pentapeptide sequence facilitates effective adaptation and methylation by recruiting CheR.

Adaptation, Physiological↗

PubMed2002

Induction of a DNA nickase in the presence of its target site stimulates adaptive mutation in Escherichia coli.

Adaptive mutation to Lac(+) in Escherichia coli strain FC40 depends on recombination functions and is enhanced by the expression of conjugal functions. To test the hypothesis that the conjugal function that is important for adaptive mutation is the production of a single-strand nick at the conjugal origin, we supplied an exogenous nicking enzyme, the gene II protein (gIIp) of bacteriophage f1, and placed its target sequence near the lac allele. When both gIIp and its target site were present, adaptive mutation was stimulated three- to fourfold. Like normal adaptive mutations, gIIp-induced mutations were recA(+) and ruvC(+) dependent and were mainly single-base deletions in runs of iterated bases. In addition, gIIp with its target site could substitute for conjugal functions in adaptive mutation. These results support the hypothesis that nicking at the conjugal origin initiates the recombination that produces adaptive mutations in this strain of E. coli, and they suggest that nicking may be the only conjugal function required for adaptive mutation.

Adaptation, Physiological↗

PubMed1994

Effect of simultaneous administration of cold-adapted and wild-type influenza A viruses on experimental wild-type influenza infection in humans.

On the basis of the ability of the attenuated cold-adapted strain of influenza A virus to suppress disease production in ferrets simultaneously infected with epidemic influenza virus (P. Whitaker-Dowling, H.F. Maassab, and J.S. Youngner, J. Infect. Dis. 164:1200-1202, 1991), an evaluation of the ability of the cold-adapted virus to modify clinical disease in humans was made. Adult volunteers with prechallenge serum hemagglutination-inhibition titers to the influenza A/Kawasaki/86 (H1N1) virus of < or = 1:8 received either 10(7) 50% tissue culture infective doses of the wild-type A/Kawasaki virus or a mixture of 10(7) 50% tissue culture infective doses of each of the wild-type virus and a cold-adapted A/Kawasaki reassortant virus by intranasal drops in a randomized, double-blind fashion. Symptoms and wild-type virus shedding were assessed daily for 6 days following challenge. Results were compared with those derived from another group of volunteers who received only cold-adapted virus. Volunteers who received the mixed inoculum of cold-adapted and wild-type viruses had lower symptom scores than those who received wild-type virus alone, suggesting that coinfection with the cold-adapted virus may modify wild-type virus infection, but the differences were not statistically significant in this small study. The data demonstrate that administration of cold-adapted influenza A virus to humans at the time of wild-type virus infection is a safe procedure.

Adaptation, Physiological↗

PubMed1997

Cell culture adaptation of Puumala hantavirus changes the infectivity for its natural reservoir, Clethrionomys glareolus, and leads to accumulation of mutants with altered genomic RNA S segment.

This paper reports the establishment of a model for hantavirus host adaptation. Wild-type (wt) (bank vole-passaged) and Vero E6 cell-cultured variants of Puumala virus strain Kazan were analyzed for their virologic and genetic properties. The wt variant was well adapted for reproduction in bank voles but not in cell culture, while the Vero E6 strains replicated to much higher efficiency in cell culture but did not reproducibly infect bank voles. Comparison of the consensus sequences of the respective viral genomes revealed no differences in the coding region of the S gene. However, the noncoding regions of the S gene were found to be different at positions 26 and 1577. In one additional and independent adaptation experiment, all analyzed cDNA clones from the Vero E6-adapted variant were found to carry substitutions at position 1580 of the S segment, just 3 nucleotides downstream of the mutation observed in the first adaptation. No differences were found in the consensus sequences of the entire M segments from the wt and the Vero E6-adapted variants. The results indicated different impacts of the S and the M genomic segments for the adaptation process and selective advantages for the variants that carried altered noncoding sequences of the S segment. We conclude that the isolation in cell culture resulted in a phenotypically and genotypically altered hantavirus.

Adaptation, Physiological↗