Biology subjects

Whitehead, K.

Publications and source records attributed to Whitehead, K..

4 recordsLinked to original sources

bioRxiv2023

Ex-Lactobacillus Strains with Intrinsic Propensity to Stabilize Pickering Oil-in-Water Emulsions

Knowledge of surface characteristics is a major step in the evaluation of bacterial cells for potential use as Pickering emulsion stabilizers. Here, the cell surface characteristics of 31 strains of the ex-Lactobacillus genus were studied with the aim of evaluating their intrinsic abilities to serve as Pickering stabilizers of oil-in-water emulsions. About 77.42% of the tested strains demonstrated relatively highly negative zeta potential (-43.76 mV [≤] zeta potential [≤] -19.23 mV), while [~]58% of the strains demonstrated high cell surface hydrophobicity (microbial adhesion to hexadecane or MATH [≥] 30%). By combining these findings, four different cell surface features were defined (I, II, II and IV). Strains mainly demonstrated the type I surface feature ([~]45%), with most expressing strongly negative zeta potential and high surface hydrophobicity (zeta potential < -15 mV and MATH [≥] 30%, respectively). It appeared that the abundance of negative charge on the surfaces of ex-Lactobacillus cells positively influences surface hydrophobicity. Assessment of intrinsic Pickering stabilization potential using 12 selected strains indicated that four strains showed profound droplet size stability. At least one strain was observed to have natural propensity to form relativley compact and small emulsion droplets (63{+/-}3 {micro}m), leading to enhanced firmness and storage stability of the Pickering emulsions.

microbiology↗

bioRxiv2022

Spontaneous activation of cortical somatosensory networks depresses their excitability in preterm human neonates

In the developing cortex of preterm human infants, neuronal activity is discontinuous - characterized by sudden, high-amplitude bursts that interrupt periods of quiet background activity. While the functional significance of these bursts is well established, the underlying cause remains unclear. We propose that this burst-quiescence pattern arises from a temporary "refractoriness" in cortical networks following spontaneous activation. To investigate this, we examined whether spontaneous activity in sensory networks reduces their excitability by assessing how ongoing brain activity influences responses to external sensory stimuli. We recorded electroencephalographic (EEG) responses to tactile stimulation of the hands and feet in 35 preterm infants, with a median post-menstrual age of 32 weeks. This stimulation triggered increases in wideband cortical power, showing two distinct peaks: one in the delta range and another in the alpha-beta range. Delta-band activity is widespread across the scalp, while the faster alpha-beta responses were confined to somatotopically specific regions. Importantly, we found that when the baseline activity shared similar spectral and spatial characteristics with the evoked somatosensory response, the magnitude of the evoked response was reduced. This suggests that spontaneous events transiently engage and saturate both widespread (tangential) and localized (columnar) cortical circuits. As a result, the same cortical regions become temporarily less responsive--a form of refractoriness--preventing immediate reactivation. This mechanism may explain the cyclical pattern of bursting and quiescence observed in the preterm brain. Significance StatementIt is well known that the preterm human brain exhibits a characteristic alternation between high-amplitude activity and quiescence, yet the underlying mechanism remains unclear. Drawing inspiration from developmental neuroscience in animal models, the present study provides the first potential neurobiological explanation for this rhythmic pattern. Using EEG recordings and a somatosensory stimulation paradigm, it demonstrates that preterm cortical bursts induce a refractory period during which external stimuli fail to elicit a response - revealing an intrinsic, activity-dependent depression mechanism. By presenting fundamental novel insights into the neurobiology of preterm cortical activity, this work has broad implications, offering both basic neuroscientists and clinical specialists new understanding of the developmental origins of sensory processing and neonatal EEG patterns linked to later neurobehavioural outcomes.

neuroscience↗

bioRxiv2022

Neurophysiological basis of hemodynamic responses in the developing human brain before the time of normal birth

Neurovascular coupling that links neural activity to localized increases in blood flow is essential both for brain function and to prevent tissue injury. In the healthy human brain, this underlies an association between the duration of EEG microstates, which represent coordinated and metastable activation of neuronal ensembles, and increases in hemodynamic activity. However, in early human life it is not clear whether neurovascular coupling is functional as the underlying physiological mechanisms may be too immature to effectively support it. Here, we combined MRI compatible robotics with simultaneous EEG and fMRI data acquisition in 13 preterm infants to assess whether the relationship between neural activity and hemodynamic responses is present in this critical period of early life. Passive sensorimotor stimulation elicited both a distinct sequence of four EEG microstates and a significant rise in the blood oxygen level dependent (BOLD) fMRI signal in the left primary sensorimotor cortex. Furthermore, EEG microstate duration was significantly related to BOLD response amplitude. These results suggest that effective neurovascular coupling is present in the human brain even before the normal time of birth and reveal a complex relationship between EEG and fMRI signals underpinned by patterns of activity across distinct neural ensembles.

neuroscience↗

bioRxiv2022

Developmental switch in prediction and adaptation to pain in human neonates

Habituation to recurrent non-threatening or unavoidable noxious stimuli is an important aspect of adaptation to pain and indicates the ability of the brain to encode expectation of imminent nociception. However, it is not known whether the newborn brain can predict and habituate to recurrent noxious inputs. We used electroencephalography to investigate changes in cortical microstates, which represent the complex sequential processing of noxious inputs, following repeated clinically-required heel lances in term and preterm infants. Noxious stimulus repetition decreased the engagement of early sensory-related microstates and associated behavioural and physiological responses in term infants, while preterm infants did not show signs of adaptation. Nevertheless, both groups displayed a switch between different microstates at longer latencies. These data suggests that the preterm brain is capable of encoding high-level contextual differences in pain, but cannot update its prediction, which allows for adaptation, emphasising the vulnerability of this population to recurrent pain. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/486988v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@1f237bborg.highwire.dtl.DTLVardef@1290318org.highwire.dtl.DTLVardef@18a4d76org.highwire.dtl.DTLVardef@e3be5e_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗