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PubMed2000

Chronic effects of therapeutic irradiation for localized prostatic carcinoma on anorectal function.

PURPOSE: To evaluate prospectively the prevalence and pathophysiology of anorectal dysfunction following radiation therapy (RTH) for localized carcinoma of the prostate. METHODS AND MATERIALS: The following parameters of anorectal function were evaluated in each of 35 patients (aged 55-82 years) with localized prostatic carcinoma treated with RTH either to a dose of 55 Gy/20 fractions/4 weeks (18 patients) or 64 Gy/32 fractions/6.5 weeks (17 patients), before RTH and 4-6 weeks and at a mean (+/- SD) of 1.4 (+/- 0.2) years after its completion: (1) anorectal symptoms (questionnaire), (2) anorectal pressures at rest and in response to voluntary squeeze and increases in intra-abdominal pressure (multiport anorectal manometry), (3) rectal sensation (balloon distension) and (4) anal sphincteric morphology (endoanal ultrasound). RESULTS: All but 1 patient completed three series of measurements. RTH had no effect on anal sphincteric morphology. The increase in frequency of defecation and fecal urgency and incontinence scores previously reported in the patients 4-6 weeks after RTH were sustained 1 year later (p < 0.001, p < 0.001, and p < 0.05, cf. baseline, respectively). At this time, 56% (19 of 34), 50% (17 of 34) and 26% (9 of 34) of the patients had increased frequency of defecation, fecal urgency, and incontinence, respectively. Decreases in anal sphincteric pressures at rest and in response to voluntary squeeze recorded in the patients 4-6 weeks after RTH were not sustained 1 year later but the volumes of rectal distension associated with perception of the stimulus and desire to defecate were lower compared with baseline volumes (p < 0.01 and p < 0.05, respectively), reflecting heightened rectal sensitivity in the patients. There was no difference in measurements between the two radiation dose regimens. Univariate logistical regression analysis was performed on patients who had experienced increased symptom scores or decreases in recorded motor and sensory manometric parameters at 1 year, cf. baseline. The predictor variables used included individual patient tumor and treatment characteristics as well as individual patient symptom scores and parameters of anorectal motor and sensory function at baseline and 4-6 weeks after RTH. The results of the univariate logistical regression analysis showed that (1) frequency of defecation at 4-6 weeks and (2) rectal volumes at baseline both for (a) perception (p < 0.001) and (b) desire to defecate (p < 0.001), predicted significantly for the patients who had symptoms and signs of anorectal dysfunction at 1 year. Individual patient tumor and treatment-related variables tested, in contrast, had no predictive significance. CONCLUSIONS: Anorectal symptoms following RTH for prostatic carcinoma are common and persist at least until 1 year after its completion and are associated with objective evidence of heightened rectal sensitivity.

Aged↗

PubMed1990

Neural elements in the pineal complex of the frog, Rana esculenta, II: GABA-immunoreactive neurons and FMRFamide-immunoreactive efferent axons.

The photosensory pineal complex of anurans comprises an extracranial part, the frontal organ, and an intracranial part, the pineal organ proper. Although the pineal organ functions mainly as a luminosity detector, the frontal organ may monitor the relative proportions of short and intermediate/long wavelengths in the ambient illumination. The major pathway of information processing in the pineal and frontal organs is the photoreceptor to ganglion cell synapse. It is not known whether interneurons form part of the neural circuitry. In the present study, we demonstrate GABA-immunoreactive (GABA-IR) neurons in the pineal and frontal organs of the frog, Rana esculenta. No GABA-IR axons were observed in the pineal nerve between the frontal and pineal organs, or in the pineal tract that connects the pineal complex with the brain. The GABA-IR neurons differed in morphology from centrally projecting neurons visualized by retrograde labeling with horseradish peroxidase. Thus, we suggest that the GABA-IR neurons in the pineal and frontal organs represent local interneurons. Axons of central origin, immunoreactive with a sensitive antiserum against the tetrapeptide Phe-Met-Phe-Arg-NH2 (FMRFamide), were observed in the intracranial portion of the photosensory pineal organ. The immunoreactive axons enter the caudal pole of the pineal organ via the posterior commissure. The largest density of axons was observed in the caudal part, while fewer axons were detected in the rostral portion. The uneven distribution of the FMRFamide-immunoreactive axons may be related to the distribution of different types of intrapineal neurons. FMRFamide-immunoreactive varicose axons were observed in the extracranial frontal organ. A central innervation of the pineal organ, previously known exclusively from amniotes, is probably not per se linked with the evolutionary transition of the pineal organ from a directly photosensory organ to a neuroendocrine organ. It could rather represent a centrifugal input to a sensory system which has been retained when the directly sensory functions have changed, during phylogeny, to neuroendocrine functions.

Animals↗

PubMed2000

Development of rat chorda tympani sodium responses: evidence for age-dependent changes in global amiloride-sensitive Na(+) channel kinetics.

In rat, chorda tympani nerve taste responses to Na(+) salts increase between roughly 10 and 45 days of age to reach stable, mature magnitudes. Previous evidence from in vitro preparations and from taste nerve responses using Na(+) channel blockers suggests that the physiological basis for this developmental increase in gustatory Na(+) sensitivity is the progressive addition of functional, Na(+) transduction elements (i.e., amiloride-sensitive Na(+) channels) to the apical membranes of fungiform papilla taste receptor cells. To avoid potential confounding effects of pharmacological interventions and to permit quantification of aggregate Na(+) channel behavior using a kinetic model, we obtained chorda tympani nerve responses to NaCl and sodium gluconate (NaGlu) during receptive field voltage clamp in rats aged from 12-14 to 60 days and older (60+ days). Significant, age-dependent increases in chorda tympani responses to these stimuli occurred as expected. Importantly, apical Na(+) channel density, estimated from an apical Na(+) channel kinetic model, increased monotonically with age. The maximum rate of Na(+) response increase occurred between postnatal days 12-14 and 29-31. In addition, estimated Na(+) channel affinity increased between 12-14 and 19-23 days of age, i.e., on a time course distinct from that of the maximum rate of Na(+) response increase. Finally, estimates of the fraction of clamp voltage dropped across taste receptor apical membranes decreased between 19-23 and 29-31 days of age for NaCl but remained stable for NaGlu. The stimulus dependence of this change is consistent with a developmental increase in taste bud tight junctional Cl(-) ion permeability that lags behind the developmental increase in apical Na(+) channel density. A significant, indirect anion influence on apical Na(+) channel properties was present at all ages tested. This influence was evident in the higher apparent apical Na(+) channel affinities obtained for NaCl relative to NaGlu. This stimulus-dependent modulation of apical Na(+) channel apparent affinity relies on differences in the transepithelial potentials between NaCl and NaGlu. These originate from differences in paracellular anion permeability but act also on the driving force for Na(+) through apical Na(+) channels. Detection of such an influence on taste depends fundamentally on the preservation of taste bud polarity and on a direct measure of sensory function, such as the response of primary afferents.

Aging↗

PubMed2006

Qualitative descriptors used by patients following orthognathic surgery to portray altered sensation.

PURPOSE: Following orthognathic surgery, patients use qualitatively different words to describe the altered sensation on their face that results from tissue inflammation and nerve injury. These words indicate normal, hypoesthetic, paresthetic, and dysesthetic sensations, and reflect the intrusiveness of the alteration. Our intent was to study the words chosen by patients from a standardized list to characterize sensory recovery during the first 6 months after surgery and to examine whether patients who underwent different surgical procedures tended to choose different sets of words. PATIENTS AND METHODS: Patients' selections from a list of 27 words that described their assessment of spontaneous and evoked facial sensations were obtained before surgery and at 1 week, 1 month, 3 months, and 6 months after surgery. Data were obtained from 146 patients enrolled in a randomized controlled clinical trial designed to evaluate the potential of sensory retraining in the rehabilitation of patients who experience impairment in sensory function after nerve injury. Mantel Haenszel general correlation and row mean score statistics were used to assess the association between time and word choice and to compare the word choice categories of 4 surgical groups: bilateral sagittal split osteotomy (BSSO) only, with or without genioplasty; BSSO + Le Fort I, with or without genioplasty. RESULTS: In general, the number of words selected to describe the alteration in sensation decreased over time, as did the intrusiveness of the category of words chosen. However, the intrusiveness remained the same or worsened from 1 week to 6 months for 32% of patients. With increased time after surgery, the percentage of patients who reported altered evoked sensations exceeded the percentage who reported spontaneous sensations. For example, at 6 months the altered sensation of 66% of the patients was classified in the paresthesia and dysesthesia categories by the evoked assessment of sensation; whereas, that of only 47% of the patients were classified as such by the spontaneous assessment. The addition of Le Fort I to BSSO did not affect the way patients reported altered sensation on their lower face. Hypoesthesia and paresthesia, but not dysesthesia, were less of a problem on the midface than on the lower face after BSSO + Le Fort I. Patients who had genioplasty more frequently chose descriptors for the lower face that reflected soft tissue trauma and inflammation ("swollen," "tender," and "burning") than patients without genioplasty; however, this difference decreased with time after surgery. CONCLUSION: The current findings indicate that patients' selection of words differentiates individuals who experienced only a simple loss in sensation (ie, present negative symptoms), those who experienced active sensations that are not normally present (ie, present positive symptoms), and those whose active sensations are additionally uncomfortable or painful. It is possible that continued study of the latter group of patients will reveal patterns of word usage that predict poor long-term recovery and disabling sensory disorders.

Adolescent↗

PubMed2002

Large myelinated nerve fiber hypersensitivity in oral malignancy.

OBJECTIVES: The purpose of this study was to assess the sensory function of trigeminal nerve A-beta fibers in suspected soft tissue oral malignancies. STUDY DESIGN: Twenty-three patients referred for the evaluation of an oral lesion suspected of malignancy were included in the study. All lesions were classified as in, near, or out of the nerve territory containing the lesion. Within these subgroups we assessed the sensitivity of A-beta primary afferents to weak electrical currents applied bilaterally to regions innervated by 3 peripheral branches of the trigeminal nerve. The ratio of electrical detection thresholds from the affected and the unaffected side was calculated. Electrical detection threshold ratios were contrasted with the results of physical examination, radiographic imaging, and biopsy. RESULTS: For dermatomes containing the lesions, ratios were lower than 0.8 in 12 patients. Biopsy showed that the lesions in 10 of these 12 patients were malignant. No malignancy was found in the remaining 11 patients. CONCLUSIONS: A-beta primary afferent hypersensitivity is observed to occur in nerves exposed to soft tissue oral malignancy.

Adult↗

PubMed1998

Partial and complete sciatic nerve injuries induce similar increases of neuropeptide Y and vasoactive intestinal peptide immunoreactivities in primary sensory neurons and their central projections.

Partial nerve injury is more likely to cause neuropathic pain than complete nerve injury. We have compared the changes in neuropeptide expression in primary sensory neurons which follow complete and partial injuries to determine if these might be involved. Since more neurons are damaged by complete injury, we expected that complete sciatic nerve injury would simply cause greater increases in neuropeptide Y and vasoactive intestinal peptide than partial injury. We examined neuropeptide Y and vasoactive intestinal peptide immunoreactivities in L4 and L5 dorsal root ganglia, the dorsal horn of L4-L5 spinal cord, and the gracile nuclei of rats killed 14 days after unilateral complete sciatic nerve transection, partial sciatic nerve transection and chronic constriction injury of the sciatic nerves. In all three groups of rats, neuropeptide Y- and vasoactive intestinal peptide-immunoreactive neurons were increased in the ipsilateral L4 and L5 dorsal root ganglion when compared with the contralateral side. Most neuropeptide Y-immunoreactive neurons were of medium and large size, but a few were small. Neuropeptide Y-immunoreactive axonal fibers were increased from laminae I to IV, and vasoactive intestinal peptide-immunoreactive axonal fibers were increased in laminae I and II, of the ipsilateral dorsal horn of L4-L5 spinal cord. The increases of neuropeptide Y and vasoactive intestinal peptide immunoreactivities in the dorsal horn were similar among the three groups. However, only after constriction injury were some vasoactive intestinal peptide-immunoreactive neurons seen in the deeper laminae of the ipsilateral dorsal horn. Robust neuropeptide Y-immunoreactive axonal fibers and some neuropeptide Y-immunoreactive cells were seen in the ipsilateral gracile nuclei of all three groups of animals, but neuropeptide Y-immunoreactive cells were more prominent after constriction injury. Contrary to our expectations, partial and complete sciatic nerve injuries induced similar increases in neuropeptide Y and vasoactive intestinal peptide in lumbar dorsal root ganglion neurons and their central projections in the dorsal horn and the gracile nuclei two weeks after injury. Some neurons whose axons were spared by partial injury may also increase neuropeptide Y or vasoactive intestinal peptide expression. Altered neuropeptide release from these functional sensory neurons may play a role in neuropathic pain.

Animals↗

PubMed1996

Electrically evoked cerebral potentials during esophageal distension at perception and pain threshold.

OBJECTIVE: To investigate esophageal sensory function in normal volunteers. METHODS: The method of evoking cerebral potentials (EPs) after electrical stimulation of the esophagus was applied in eight healthy male volunteers, 20-40 yr old. Electrical stimulation was obtained via bipolar Ag/AgCl electrodes attached to a latex balloon mounted on a catheter. The balloon was inflated stepwise to perception and pain thresholds. At the perception threshold for balloon distension, the intensity of electrical stimulation was increased stepwise to perception threshold for electrical stimulation, and subsequently to 2-fold, 4-fold, and 8-fold perception threshold. EPs were recorded from the vertex (Cz) and forehead (Fz, reference) and compared between the increasing electrical stimulation intensities and between perception and pain thresholds for mechanical stimulation. RESULTS: The results show that amplitudes of EPs significantly increased with increasing electrical stimulation intensities, whereas latencies of EPs were not affected. Latencies and amplitudes of EPs were comparable at perception and pain thresholds for esophageal distension. CONCLUSIONS: The study suggests that repetitive electrical stimulation of the human esophagus is predominantly mediated via vagal A-delta fibers. The unaltered EPs at the perception and pain thresholds suggest that vagal A-delta fibers are not involved in mediation of pain. The findings support the view that painful and nonpainful stimuli are mediated via different visceral afferents between the esophagus and brain in humans.

Adult↗

PubMed2002

Morphological and functional characterization of a rat vaginal smooth muscle sphincter.

The aim of the present study was to gain information about adrenergic-, cholinergic- and non-adrenergic, non-cholinergic (NANC)- transmitter systems/mediators in the rat vagina, and to characterize its smooth muscles functionally. Tissue sections from vagina of Sprague Dawley rats were immunolabelled with antibodies against protein gene product 9.5 (PGP), synaptophysin (Syn), tyrosine hydroxylase (TH), vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP). Circularly cut vaginal smooth muscle preparations from the distal vagina were studied in organ baths. In the paravaginal tissue, a large number of PGP-, NOS-, TH-, VIP-immunoreactive (IR) and few CGRP-IR nerve trunks were observed, giving off branches to the smooth muscle wall. The smooth muscle wall was supplied by a large number of PGP-, Syn-, VAChT-, NPY-, NOS- and TH- IR nerve terminals, whilst only a moderate to few numbers of CGRP-, VIP- and PACAP-IR terminals were identified. Especially the distal part of the vaginal wall, where the circularly running smooth muscle was thickened into a distinct sphincter structure, was very richly innervated, predominantly by PGP- and NOS-IR terminals. Below and within the basal parts of the epithelium in the distal half of the vagina, a large number of PGP- and few NOS- and PACAP-IR varicose terminals were observed. The vaginal arteries were encircled by plexuses of nerve terminals. A large number of these were PGP-, Syn-, VAChT-, NOS-, TH-, NPY- and VIP-IR, and few were CGRP- and PACAP-IR. In isolated preparations of the distal vagina, electrical field stimulation (EFS) caused frequency-dependent contractions, which were reduced by sildenafil, tetrodotoxin (TTX) and phentolamine. In preparations contracted by norepinephrine (NA), EFS produced frequency-dependent relaxations. Pretreatment with the NOS-inhibitor N(G)-nitro-L-arginine, TTX, or the inhibitor of soluble guanylate cyclase, ODQ, abolished the EFS relaxations. In NE precontracted preparations, cumulative addition of sildenafil caused concentration-dependent relaxation. Carbachol contracted the strips concentration-dependently from baseline. It can be concluded that the distal part of the rat vagina forms a distinct smooth muscle sphincter, which is richly innervated by adrenergic, cholinergic and NANC nerves. The present studies suggest that in the rat the L-arginine/NO-system not only plays an important role in the regulation of vaginal smooth muscle tone, but also affects blood flow, and may have sensory functions.

Acetylcholinesterase↗

PubMed2003

Effects of neurotrophins on synaptic protein expression in the visual cortex of dark-reared rats.

Total lack of visual experience [dark rearing (DR)] is known to prolong the critical period and delay development of sensory functions in mammalian visual cortex. Recent results show that neurotrophins (NTs) counteract the effects of DR on functional properties of visual cortical cells and exert a strong control on critical period duration. NTs are known to modulate the development and synaptic efficacy of neurotransmitter systems that are affected by DR. However, it is still unknown whether the actions of NTs in dark-reared animals involve interaction with neurotransmitter systems. We have studied the effects of DR on the expression of key molecules in the glutamatergic and GABAergic systems in control and NT-treated animals. We have found that DR reduced the expression of the NMDA receptor 2A subunit and its associated protein PSD-95 (postsynaptic density-95), of GRIP (AMPA glutamate receptor interacting protein), and of the biosynthetic enzyme GAD (glutamic acid decarboxylase). Returning dark-reared animals to light for 2 hr restored normal expression of the above-mentioned proteins almost completely. NT treatment specifically counteracts DR effects; NGF acts primarily on the NMDA system, whereas BDNF acts primarily on the GABAergic system. Finally, the action of NT4 seems to involve both excitatory and inhibitory systems. These data demonstrate that different NTs counteract DR effects by modulating the expression of key molecules of the excitatory and inhibitory neurotransmitter systems.

Animals↗

PubMed1995

Functional ablation of sensory neurons impairs healing of acute gastric mucosal damage in rats.

Healing of ethanol-injured gastric mucosa was studied in rats treated with a neurotoxic dose of capsaicin to induce functional ablation of sensory nerves. Capsaicin treatment delayed the healing of mucosal damage in the glandular region and promoted the development of deep ulcerations predominantly in the antrum. These lesions occupied 86% of the antral surface and were associated with marked invasion of inflammatory cells and 18-fold elevation of gastric myeloperoxidase activity compared with vehicle-pretreated rats. Inhibition of cyclooxygenase, 5-lipoxygenase, or nitric oxide synthase did not affect the development of antral lesions after ethanol challenge in capsaicin-pretreated rats. In vehicle-pretreated rats, inhibition of nitric oxide synthase did not mimic the effect of functional ablation of sensory neurons. The findings suggest that in the gastric mucosa sensory neurons contribute to repair processes and limit the inflammatory response to injury. These effects do not involve arachidonic acid metabolites or nitric oxide.

Acute Disease↗

PubMed1988

Sensory, psychomotor, and motor functions in men of different ages.

As a part of a larger gerontological research project various sensory, psychomotor, and motor functions were studied in three samples of men aged 31-35, 51-55 and 71-75 years. The samples were randomly drawn from men living in the town of Jyväskylä on January the 1st 1981 and belonging to the actual cohorts. The sensory functions studied included static balance (postural sway during standing), vibrotactile sensitivity on the inner malleolus of the ankle, hearing (pure-tone thresholds at 125-8000 Hz and speech-understanding), and vision (dark adaptation and lens accommodation). The assessments of psychomotor and motor functions included simple and choice reaction and movement times (visual and auditory stimuli), tapping rate over 2.5 s and 5.0 s, and maximal knee extension velocity. Differences between the age groups in these functions were studied. In addition, within the age groups, the associations of sensory, psychomotor, and motor functions with health status, certain living habits, occupational and educational background, and cognitive functions were analyzed. Also their interrelations were analyzed. The results showed that the effect due to age group was evident in nearly all functions. The sensory functions worsened and psychomotor and motor speeds became slower when proceeding from younger to older age groups. When the interrelations of the functions were analyzed the main observation was the independence of the sensory measures of each other in all age groups. The only consistent associations between the indicators of different sensory modalities was observed between the extent of postural sway and vibrotactile sensitivity on the ankle. On the other hand, psychomotor speed showed associations with many of the sensory measures. Finally, in analyzing the clustering of poorer or better performances in many or most of the sensory, psychomotor, and motor functions within the age groups, it was observed that the better performers in these measures tended to have longer education, worked more often in managerial than in manual occupations, reported fewer occupational hazards and had better results in cognitive tests than the poorer performers. The overall status of health as expressed by the number of chronic diseases and self-rated health was associated with performance in these assessments only in the youngest group where those having more diseases had a lower level in these functions. The associations of certain health-related living habits (drinking, smoking, physical activity) with the functions were, as a whole, negligible.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗

PubMed1977

Hyperhydrosis in paraplegia.

A 20-year-old man suffered head, chest, and abdominal trauma in an auto accident resulting in a traumatic dissecting aneurysm of the thoracic aorta. Hypotension developed. The aneurysm was resected and replaced with a prosthetic graft. Postoperatively, the patient was found to be paraplegic below T-9, areflexic and anesthetic to pain and temperature, with preservation of vibration and position senses. In the ensuing nine months, the patient regained considerable sensory function in his lower extremities and had severe constant hyperhydrosis below the T-9 dermatome. The exaggerated sweating was unaffected by temperature change and anxiety. It was diminished by methantheline bromide treatment but never abolished. The spinal cord lesion is postulated to be anterior horn cell loss, with preservation of interneurons and intermediolateral gray columns. Disinhibition of sympthetic circuits or sprouting of axons are proposed mechanisms.

Adult↗

PubMed2000

Sensory changes associated with selective neck dissection.

OBJECTIVE: To evaluate sensory changes in the head and neck region associated with selective neck dissection with or without preservation of cervical root branches. DESIGN: Retrospective cohort study. SETTING: University tertiary referral hospital and a Veterans Affairs hospital. PATIENTS: Fifty-seven patients who had undergone 84 neck dissections with or without preservation of the sensory cervical root branches 3 or more months before evaluation. INTERVENTIONS: Questionnaire combined with head and neck sensory examination. MAIN OUTCOME MEASURES: Neck and facial sensory function. RESULTS: Neck dissections with preservation of the cervical rootlets were most likely to be associated with a small area of anesthesia in the upper neck below the body of the mandible and anterior to the mid-body of the mandible (P=.03). Neck dissections without rootlet-preserving technique increased the area of anesthesia to include all other areas of the neck (P= .02). CONCLUSIONS: Preservation of the cervical root branches resulted in a small, limited, and uniform area of the neck rendered permanently anesthetic. Conversely, sacrifice of the nerve branches led to a pattern of anesthesia involving the entire neck.

Aged↗

PubMed1989

Age-related changes in the internal branch of the rat superior laryngeal nerve.

This investigation was initiated to provide data on the ultrastructural basis for neurologic age-related changes in laryngeal sensory function. In the present study, an animal model (female Wistar rats: age range: young [Y], 3 to 5 months; old [O], 25 months; and very old [VO], 29 to 30 months) was used to examine systematically changes in the internal branch of the superior laryngeal nerve with age using electron microscopic morphometric techniques. Total fiber counts, fiber populations (size categories), and mean fiber size for myelinated and unmyelinated fibers did not change with age. Qualitative changes were consistent with segmental demyelination and axonal degeneration in the older animals. There was also a significant age-related increase in the volume fraction of adaxonal Schwann cell cytoplasm (Y, 0.019; O, 0.041; and VO, 0.042). Ultrastructural correlates of intracellular support and axonal transport showed a significant decrease in the numerical density of neurofilaments (Y, 0.126/micron2; O, 0.073/micron2; and VO, 0.078/micron2) in the older animals, but no change in the numerical density of microtubules. Energy metabolism correlates in the form of mitochondrial volume fraction did not change with age. There was a significant increase in the volume fraction of the intrafascicular extracellular space (Y, 0.224; O, 0.271; and VO, 0.301), indicating a late, age-related change in the extracellular environment. These changes could lead to decreased conduction velocity or complete fiber dysfunction. A number of these changes resembled those of aged human peripheral nerves already examined.

Aging↗

PubMed1998

Visual processing impairment and risk of motor vehicle crash among older adults.

CONTEXT: Motor vehicle crash risk in older drivers has been associated with visual acuity loss, but only weakly so, suggesting other factors contribute. The useful field of view is a measure that reflects decline in visual sensory function, slowed visual processing speed, and impaired visual attention skills. OBJECTIVE: To identify whether measures of visual processing ability, including the useful field of view test, are associated with crash involvement by older drivers. DESIGN: Prospective cohort study with 3 years of follow-up, 1990-1993. SETTING: Ophthalmology clinic assessment of community-based sample. PATIENTS: A total of 294 drivers aged 55 to 87 years at enrollment. MAIN OUTCOME MEASURE: Motor vehicle crash occurrence. RESULTS: Older drivers with a 40% or greater impairment in the useful field of view were 2.2 times (95% confidence interval, 1.2-4.1) more likely to incur a crash during 3 years of follow-up, after adjusting for age, sex, race, chronic medical conditions, mental status, and days driven per week. This association was primarily mediated by difficulty in dividing attention under brief target durations. CONCLUSION: Reduction in the useful field of view increases crash risk in older drivers. Given the relatively high prevalence of visual processing impairment among the elderly, visual dysfunction and eye disease deserve further examination as causes of motor vehicle crashes and injury.

Accidents, Traffic↗

PubMed1996

Immunohistochemical, electrophysiological, and electron microscopical study of rat fungiform taste buds after regeneration of chorda tympani through the non-gustatory lingual nerve.

The sensory innervation of fungiform papillae on the rat dorsal tongue is derived from branches of two cranial nerves: the lingual branch of the trigeminal nerve which provides somatosensory innervation and the chorda tympani (CT) branch of the facial nerve, which provides innervation to the taste buds. Removal of the CT results in degeneration of the taste buds. Removal of both nerves results in reduction in size of fungiform papillae and an altered pattern of keratinization in its epithelium. Regeneration of nerves to the epithelium restores the pre-operative condition. Thus, in addition to their sensory functions, both the CT and lingual seem to exert trophic effects on the phenotypic expression of epithelial cells in the fungiform papillae. We severed both the CT and lingual nerves in rats and sutured the proximal stump of the CT to the distal stump of the lingual to promote regeneration of the CT along the lingual nerve pathway. At the same time, we prevented the proximal stump of the lingual from regenerating into the tongue. Our purpose was to determine whether and how the innervation pattern of the regenerated taste bud might be different from normal under these experimental conditions. We found that reinnervation by the CT through the lingual nerve occurs, that this restores the anatomical and functional integrity of the fungiform taste buds and papillae, and that some papillae, but not all, were richly innervated with subgemmal, extragemmal, and perigemmal neuron-specific enolase, calcitonin gene-related peptide, substance P, and neurokinin A-positive fibers. Moreover, responses to taste stimuli were recorded electrophysiologically from the CT.

Animals↗

PubMed1997

Distribution and role of aspartate in the nervous system of the chaetognath Sagitta.

Cholinergic control of locomotory muscles in chaetognaths is monitored by diffuse transmitter release through layers of collagen fibers that form the connective stratum of the hydroskeleton. Despite the lack of morphologically defined synaptic junctions, the control of locomotor activity in chaetognaths is highly specific and allows complex behavioral patterns. This complexity suggests the existence of neuromediators acting to modulate the effects of the main motor neurotransmitter, acetylcholine, on muscular contraction. Immunocytochemical investigations performed in Sagitta friderici by using antibodies directed against L-aspartate revealed the presence of the amino acid within abundant fiber networks regularly distributed in the head, trunk, and tail and within discrete groups of cell bodies. In addition to known components of the sensory and motor nervous systems, L-aspartate immunoreactivity revealed previously undescribed intraepidermal networks of axonal profiles. With the exception of two giant anterior fibers radiating from the ventral ganglion, L-aspartate-immunoreactive processes were usually thin and varicose, occasionally making an anastomosis. As indicated by electron microscopy, L-aspartate-immunoreactive varicosities apposed to the connective stratum were filled with synaptic-like vesicles but displayed no synaptic differentiation. Physiologic investigations suggested a potent inhibitory effect of L-aspartate on acetylcholine-induced muscle contraction. The wide distribution pattern of immunoreactive profiles suggests an important role of L-aspartate in motor and sensory functions in chaetognaths. Although classified among excitatory amino acids in vertebrates, aspartate may function as an inhibitory modulator of acetylcholine-induced muscle contraction in these enterocoelous gastroneuralians.

Animals↗

PubMed1996

A sticky problem: the Xenopus cement gland as a paradigm for anteroposterior patterning.

The cement gland is a mucus-secreting organ found at the extreme anterior of frog embryos. It attaches the embryo to a solid support before swimming and feeding begin, and also serves a related sensory function that stops the embryo from moving once it is attached. Cement gland is an extremely useful anterior marker, whose study continues to yield fundamental information concerning vertebrate axial patterning. Cement gland arises from the outer layer of the embryonic ectoderm and, in Xenopus, forms a cone of columnar epithelium. It is the first ectodermal organ to differentiate, beginning to do so by late gastrula. A battery of genes expressed in the developing and mature cement gland serve as useful markers. Cement gland development can be influenced by both stimulatory and inhibitory cell interactions. Stimulatory signals arise from the anterior neural plate, head endoderm, and the dorsal mesoderm. Inhibitory signals are present in the posterior dorsal mesoderm and in ventral ectoderm and mesoderm. Further, signalling between the ectodermal layers may restrict cement gland differentiation to the outer ectodermal cells. Several secreted molecules are able to induce or repress cement gland formation: these include noggin, follistatin, hedgehog, chordin, retinoic acid, embryonic fibroblast growth factor (eFGF), Bone Morphogenetic Protein-4 (BMP-4), and Xwnt-8. Several of these factors alter expression of the homeodomain gene Xotx2, which may be a transcriptional activator of cement gland differentiation genes. The significance of the cell interactions and factors described in positioning cement gland at the front of the embryo is explored.

Animals↗