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Indian Journal of Ophthalmology Aug 2021Red reflex test (RRT) screening is yet to be a part of the neonate's normal examination before discharge from hospital in a majority of low- and middle-income countries.... (Meta-Analysis)
Meta-Analysis Review
Red reflex test (RRT) screening is yet to be a part of the neonate's normal examination before discharge from hospital in a majority of low- and middle-income countries. The purpose was this review was to systematically evaluate the diagnostic accuracy of RRT for the detection of ocular abnormalities in newborns. PubMed, EMBASE, Scopus, Web of Science, and Cochrane database of systematic reviews were the data sources. Quality of Diagnostic Accuracy Studies-2 (QUADAS-2) was utilized for quality assessment of bias and applicability. Random effects models were used to summarize sensitivities, specificities, positive likelihood ratio (PLR), negative likelihood ratio (NLR), diagnostic odds ratio (DOR), and respective confidence intervals (CI). The pooled sensitivity, calculated from the meta analysis of 11 studies, was 23% (95% CI: 21-24%) and pooled specificity was 98% (95% CI: 98-98%). The PLR was 32.52 (95% CI: 7.89-134.15), NLR was less than 1 (0.69 [95% CI: 0.55-0.88]), and DOR calculated was 138.48 (95% CI: 23.85-803.97). The area under the curve (AUC) and Q* index for RRT were 0.98 ± 0.02 and 0.95 ± 0.045, respectively. The results of our study justify the conclusion that RRT is a highly sensitive and specific test for the detection of anterior segment abnormalities.
Topics: Humans; Infant, Newborn; Reflex
PubMed: 34304165
DOI: 10.4103/ijo.IJO_3632_20 -
Experimental Physiology Jul 2021This article reviews a unique direct injection technique that complements the more conventional right atrial injection and aerosol delivery methods to study sensory and... (Review)
Review
NEW FINDINGS
This article reviews a unique direct injection technique that complements the more conventional right atrial injection and aerosol delivery methods to study sensory and reflex effects of the lung sensors. Used in combination with other methods, this technique should contribute to the pulmonary sensory research.
ABSTRACT
The lungs house sensory receptors (sensors) that mediate a variety of sensory and reflex responses to mechanical or chemical changes. These reflexes are mainly carried through pulmonary sympathetic and vagal afferent pathways. The chemosensors in the lung periphery are especially important in pulmonary diseases and their reflex responses have traditionally been studied either by aerosol delivery, which also activates receptors in the central airways, or by right atrial injection, which also activates receptors lying outside the lung. Thus, these techniques may confound the interpretation of sensory function. Our laboratory has developed a direct injection technique to deliver agents into the lung parenchyma, which complements the conventional techniques with some important advantages. This article reviews the technique.
Topics: Afferent Pathways; Lung; Reflex; Sensory Receptor Cells; Vagus Nerve
PubMed: 33719104
DOI: 10.1113/EP089261 -
Journal of Hypertension Jul 2023The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously...
BACKGROUND
The blood pressure (BP) regulatory impact of the arterial baroreflex has been well established in health and disease. Under normotensive conditions, we have previously demonstrated functional differences in the central processing of the left versus right aortic baroreceptor afferent input. However, it is unknown if lateralization in aortic baroreflex function remains evident during hypertension.
METHOD
We therefore, investigated the effects of laterality on the expression of baroreflex-driven cardiovascular reflexes in a genetic model of essential hypertension, the spontaneously hypertensive rat (SHR). Anesthetized male SHRs (total n = 9) were instrumented for left, right, and bilateral aortic depressor nerve (ADN) stimulation (1-40 Hz, 0.2 ms, and 0.4 mA for 20 s) and measurement of mean arterial pressure (MAP), heart rate (HR), mesenteric vascular resistance (MVR), and femoral vascular resistance (FVR).
RESULTS
Left right, and bilateral ADN stimulation evoked frequency-dependent decreases in MAP, HR, MVR, and FVR. Left and bilateral ADN stimulation evoked greater reflex reductions in MAP, HR, MVR, and FVR compared with right-sided stimulation. Reflex bradycardia to bilateral stimulation was larger relative to both left-sided and right-sided stimulation. Reflex depressor and vascular resistance responses to bilateral stimulation mimicked those of the left-sided stimulation. These data indicate a left-side dominance in the central integration of aortic baroreceptor afferent input. Furthermore, reflex summation due to bilateral stimulation is only evident on the reflex bradycardic response, and does not drive further reductions in BP, suggesting that reflex depressor responses in the SHRs are primarily driven by changes in vascular resistance.
CONCLUSION
Together, these results indicate that lateralization in aortic baroreflex function is not only evident under normotensive conditions but also extends to hypertensive conditions.
Topics: Rats; Animals; Male; Rats, Inbred SHR; Pressoreceptors; Electric Stimulation; Blood Pressure; Baroreflex; Hypertension; Heart Rate; Aorta
PubMed: 37074354
DOI: 10.1097/HJH.0000000000003448 -
The Journal of Physiology Jul 2020Cutaneous reflexes were tested to examine the neuronal mechanisms contributing to muscle spasms in humans with chronic spinal cord injury (SCI). Specifically, we tested...
KEY POINTS
Cutaneous reflexes were tested to examine the neuronal mechanisms contributing to muscle spasms in humans with chronic spinal cord injury (SCI). Specifically, we tested the effect of Achilles and tibialis anterior tendon vibration on the early and late components of the cutaneous reflex and reciprocal Ia inhibition in the soleus and tibialis anterior muscles in humans with chronic SCI. We found that tendon vibration reduced the amplitude of later but not earlier cutaneous reflex in the antagonist but not in the agonist muscle relative to the location of the vibration. In addition, reciprocal Ia inhibition between antagonist ankle muscles increased with tendon vibration and participants with a larger suppression of the later component of the cutaneous reflex had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration attenuates late cutaneous spasm-like reflex activity, likely via reciprocal inhibitory mechanisms, and may represent a method, when properly targeted, for controlling spasms in humans with SCI.
ABSTRACT
The neuronal mechanisms contributing to the generation of involuntary muscle contractions (spasms) in humans with spinal cord injury (SCI) remain poorly understood. To address this question, we examined the effect of Achilles and tibialis anterior tendon vibration at 20, 40, 80 and 120 Hz on the amplitude of the long-polysynaptic (LPR, from reflex onset to 500 ms) and long-lasting (LLR, from 500 ms to reflex offset) cutaneous reflex evoked by medial plantar nerve stimulation in the soleus and tibialis anterior, and reciprocal Ia inhibition between these muscles, in 25 individuals with chronic SCI. We found that Achilles tendon vibration at 40 and 80 Hz, but not other frequencies, reduced the amplitude of the LLR in the tibialis anterior, but not the soleus muscle, without affecting the amplitude of the LPR. Vibratory effects were stronger at 80 than 40 Hz. Similar results were found in the soleus muscle when the tibialis anterior tendon was vibrated. Notably, tendon vibration at 80 Hz increased reciprocal Ia inhibition between antagonistic ankle muscles and vibratory-induced increases in reciprocal Ia inhibition were correlated with decreases in the LLR, suggesting that participants with a larger suppression of later cutaneous reflex activity had stronger reciprocal Ia inhibition from the antagonistic muscle. Our study is the first to provide evidence that tendon vibration suppresses late spasm-like activity in antagonist but not agonist muscles, likely via reciprocal inhibitory mechanisms, in humans with chronic SCI. We argue that targeted vibration of antagonistic tendons might help to control spasms after SCI.
Topics: Electromyography; H-Reflex; Humans; Muscle Contraction; Muscle, Skeletal; Spasm; Spinal Cord Injuries; Vibration
PubMed: 32298483
DOI: 10.1113/JP279478 -
American Journal of Physiology.... Aug 2022The venous distension reflex (VDR) is a pressor response evoked by peripheral venous distension and accompanied by increased muscle sympathetic nerve activity (MSNA)....
The venous distension reflex (VDR) is a pressor response evoked by peripheral venous distension and accompanied by increased muscle sympathetic nerve activity (MSNA). The effects of venous distension on the baroreflex, an important modulator of blood pressure (BP), have not been examined. The purpose of this study was to examine the effect of the VDR on baroreflex sensitivity (BRS). We hypothesized that the VDR will increase the sympathetic BRS (SBRS). Beat-by-beat heart rate (HR), BP, and MSNA were recorded in 16 female and 19 male young healthy subjects. To induce venous distension, normal saline equivalent to 5% of the forearm volume was infused into the veins of the occluded forearm. SBRS was assessed from the relationship between diastolic BP and MSNA during spontaneous BP variations. Cardiovagal BRS (CBRS) was assessed with the sequence technique. Venous distension evoked significant increases in BP and MSNA. Compared with baseline, during the maximal VDR response period, SBRS was significantly increased (-3.1 ± 1.5 to -4.5 ± 1.6 bursts·100 heartbeats·mmHg, < 0.01) and CBRS was significantly decreased (16.6 ± 5.4 to 13.8 ± 6.1 ms·mmHg, < 0.01). No sex differences were observed in the effect of the VDR on SBRS or CBRS. These results indicate that in addition to its pressor effect, the VDR altered both SBRS and CBRS. We speculate that these changes in baroreflex function contribute to the modulation of MSNA and BP during limb venous distension.
Topics: Baroreflex; Blood Pressure; Female; Heart Rate; Humans; Male; Muscle, Skeletal; Reflex; Sympathetic Nervous System; Vascular Diseases
PubMed: 35726869
DOI: 10.1152/ajpregu.00028.2022 -
Journal of Optometry 2020Evaluations of tear functions frequently involve some form of voluntary control over blink behaviour. To the degree that voluntary control of blinking risks departure... (Review)
Review
Evaluations of tear functions frequently involve some form of voluntary control over blink behaviour. To the degree that voluntary control of blinking risks departure from normal-range spontaneous blinking, the tear function findings from such studies may be confounded. Even subject awareness that blinking is being assessed may influence findings if such awareness results in any degree of voluntary control. Ideally, the influence on blink rate and tear functions induced by therapeutic or experimental interventions could be measured against a normal-range baseline spontaneous blink rate in order that any differences found could be validly attributed to those interventions. Sometimes pre-intervention 'rest-related' baseline blink rates have been incorrectly described as 'basal' blink rates without specification of pre-intervention conditions of 'rest' or consideration of any contributions from voluntary control. Also, studies which use only blink rates to measure blink efficiency ignore the critically important contribution of incomplete blinking to blink inefficiency. This review finds that the assessment of normal-range spontaneous blink rates depends on measurement conditions which have frequently been ignored previously. For example, normal-range spontaneous blink rates appear more likely to occur with fixation targets which have a disengaged affect and an associated neutral influence on and from dopamine activity. Ideally, fixation targets should also involve minimal cognitive loading and vision demands. In addition, normal-range (symptom free) spontaneous blink rates are more likely to be assessed in a comfortable ambient environment without subject awareness that blink behaviour is being assessed and when voluntary blinking is not involved.
Topics: Blinking; Dopamine; Dry Eye Syndromes; Humans; Tears
PubMed: 31992536
DOI: 10.1016/j.optom.2019.09.002 -
Neuroscience May 2022The nociceptive withdrawal reflex (NWR) is a behavioral response to protect the body from noxious stimuli. The spatial characteristics of the stimulus modulate the...
The nociceptive withdrawal reflex (NWR) is a behavioral response to protect the body from noxious stimuli. The spatial characteristics of the stimulus modulate the reflex response to prevent damage to the affected tissue. Interneurons in the deep dorsal horn in the spinal cord encode the relationship between stimulus characteristics and the magnitude of the NWR and are also likely integrating spatial information of the nociceptive stimulus. The aim of this study was to use the NWR to investigate whether the spinal spatial integration of a simultaneous stimulus is modulated by shifting the attention of the participant towards (attention) or away from (distraction) the stimulus. We hypothesized that the descending activity shapes the receptive fields of the spinal neurons encoding spatial integration of nociception. Twenty healthy volunteers participated in the study. Single and simultaneous stimuli were delivered through two stimulating electrodes located in the arch and on the lateral side in the sole of the foot. The NWR was quantified by electromyography from the Tibialis Anterior and Biceps Femoris muscles during baseline and active tasks (attention and distraction). During the baseline task, spatial summation of the NWR was evoked during simultaneous stimulation. During the distraction task, the NWR was significantly larger compared to baseline, regardless of the sites being stimulated (single and simultaneous stimuli). In contrast, the NWR recorded during the attention task did not differ from baseline. These results further support that the spinal NWR pathway is under descending control which can be modulated by cognitive processes. The NWRs recorded over both proximal and distal muscles were similarly affected by the tasks, suggesting that the descending control affects the lower leg spinal system, with no discrimination between spinal segments.
Topics: Cognition; Electric Stimulation; Electromyography; Humans; Nociception; Reflex
PubMed: 35381321
DOI: 10.1016/j.neuroscience.2022.03.038 -
Annals of Clinical and Translational... Dec 2023Here we review the clinical value of a video-oculography test for clinical evaluation of vestibular otolith function. This test is known as the video ocular counter roll... (Review)
Review
Here we review the clinical value of a video-oculography test for clinical evaluation of vestibular otolith function. This test is known as the video ocular counter roll (vOCR) and is based on measurement of torsional vestibulo-ocular reflex with a lateral head tilt. The vOCR test consists of a simple maneuver during which the head and torso are tilted en bloc by the examiner. The pattern of vOCR deficit among patients highlights its clinical value in identifying the stage of vestibular loss and recovery. The quick application of vOCR allows examination of otolith-ocular function and assessment of vestibular recovery at the bedside.
Topics: Humans; Otolithic Membrane; Reflex, Vestibulo-Ocular; Face; Vestibule, Labyrinth
PubMed: 37830132
DOI: 10.1002/acn3.51921 -
American Journal of Physiology.... Mar 2022Breath-hold diving evokes a complex cardiovascular response. The degrees of hypertension induced by the diving reflex are substantial and accentuated by the underwater...
Breath-hold diving evokes a complex cardiovascular response. The degrees of hypertension induced by the diving reflex are substantial and accentuated by the underwater swimming. This condition provides a circulatory challenge to properly buffer and cushion cardiac pulsations. We determined hemodynamic changes during the diving maneuver and hypothesized that central artery compliance would be augmented during simulated breath-hold diving. A total of 20 healthy young adults were studied. Hemodynamics were measured during exercise on a cycle ergometer, apnea, face immersion in cold water (trigeminal stimulation), and simulated breath-hold diving. Arterial compliance was measured by recording the carotid artery diameter from images derived from an ultrasound machine at the cephalic portion of the common carotid artery 1-2 cm proximal to the carotid bulb, whereas arterial pressure waveforms were obtained using an arterial tonometry placed on the contralateral carotid artery and recorded on a data acquisition software. The change in diameter was divided by the change in blood pressure to calculate arterial compliance. Arterial compliance increased with simulated diving compared with rest ( = 0.007) and was elevated compared with exercise and apnea alone ( < 0.01). A significant increase in heart rate was observed with exercise, apnea, and facial immersion when compared with rest ( < 0.001). However, simulated diving brought the heart rate down to resting levels. Cardiac output increased with all conditions ( < 0.001), with an attenuated response during simulated diving compared with exercise and facial immersion ( < 0.05). Mean blood pressure was elevated during all conditions ( < 0.001), with a further elevation observed during simulated diving compared with exercise ( < 0.001), apnea ( = 0.016), and facial immersion ( < 0.001). Total peripheral resistance was decreased during exercise and facial immersion compared with rest ( < 0.001) but was increased during simulated diving compared with exercise ( < 0.001), apnea ( = 0.008), and facial immersion ( = 0.003). We concluded that central artery compliance is augmented during simulated breath-hold diving to help buffer cardiac pulsations.
Topics: Adaptation, Physiological; Adult; Arterial Pressure; Breath Holding; Carotid Arteries; Diving; Diving Reflex; Female; Healthy Volunteers; Heart Rate; Hemodynamics; Humans; Male; Vascular Resistance; Vasoconstriction
PubMed: 35018822
DOI: 10.1152/ajpregu.00202.2021 -
Handbook of Clinical Neurology 2022Airway function is under constant neurophysiological control, in order to maximize airflow and gas exchange and to protect the airways from aspiration, damage, and... (Review)
Review
Airway function is under constant neurophysiological control, in order to maximize airflow and gas exchange and to protect the airways from aspiration, damage, and infection. There are multiple sensory nerve subtypes, whose disparate functions provide a wide array of sensory information into the CNS. Activation of these subtypes triggers specific reflexes, including cough and alterations in autonomic efferent control of airway smooth muscle, secretory cells, and vasculature. Importantly, every aspect of these reflex arcs can be impacted and altered by local inflammation caused by chronic lung disease such as asthma, bronchitis, and infections. Excessive and inappropriate activity in sensory and autonomic nerves within the airways is thought to contribute to the morbidity and symptoms associated with lung disease.
Topics: Autonomic Nervous System; Cough; Humans; Lung Diseases; Reflex; Respiratory System
PubMed: 35965034
DOI: 10.1016/B978-0-323-91534-2.00013-8