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PubMed2002

Pharyngeal branch of the glossopharyngeal nerve plays a major role in reflex swallowing from the pharynx.

Mechanical stimulation of the pharyngeal areas readily elicits reflex swallowing. However, it is much more difficult for electrical stimulation of the glossopharyngeal nerve (GPN) to evoke reflex swallowing than it is for stimulation of the superior laryngeal nerve (SLN) to do so. These paradoxical findings remain unexplained; hence, the main purpose of this study was to explain this contradiction by using a urethane-anesthetized rat. Mechanical stimulation easily elicited reflex swallowing from the pharynx. The posterior pillars, posterior pharyngeal wall, and the soft palate of the rat were extremely reflexogenic areas for swallowing. Sectioning the pharyngeal branch of the GPN (GPN-ph), however, eliminated the swallowing reflex from these areas. In contrast, sectioning the lingual branch of the GPN had no effect on the elicitation of swallowing. Electrical stimulation of the GPN-ph and SLN elicited sequentially occurring swallows. The relationship between stimulus frequency and the latency of swallowing for the GPN-ph was approximately the same as that for the SLN. These results indicate that the GPN-ph plays a major role in the initiation of reflex swallowing from the pharynx in rats.

Animals↗
PubMed1992

Concentration thresholds for fetal swallowing and vasopressin secretion.

In adults, plasma osmolality thresholds for hypernatremia-induced arginine vasopressin (AVP) secretion are similar or less than thresholds for stimulation of thirst. In the fetus, the thresholds for swallowing stimulation and AVP secretion have not been defined. Fetal swallowing and AVP secretory responses to hypertonic NaCl and urea were determined in six fetuses (130 +/- 1 1 days) chronically prepared with thyrohyoid, nuchal and thoracic esophagus, and diaphragm electromyograms (EMG), an esophageal flow probe, and vascular catheters. Fetuses received intracarotid injections (0.15 ml/kg) of increasing concentrations of NaCl (0.15, 0.30, 0.45, 0.60, 0.75, and 0.90 M), administered at 2-min intervals. A swallow was defined as a coordinated time-sequence of fetal thyrohyoid, nuchal esophagus, and thoracic esophagus EMG activity. The threshold saline concentration for swallowing was defined as the minimum NaCl dose eliciting swallow responses (within 20 s) after four of five injections at each dose. During a 2-h control period swallowing averaged 25.0 +/- 10.1 ml/h and 39.4 +/- 14.6 swallows/h. The mean NaCl threshold concentration for swallowing stimulation was 0.56 +/- 0.06 M. Fetal plasma AVP (2.6 +/- 0.9 pg/ml) increased significantly at the maximum subthreshold (7.6 +/- 4.0 pg/ml) and the threshold NaCl concentration (8.2 +/- 4.0 pg/ml) that stimulated swallowing. On a subsequent day, equiosmolar urea injections increased plasma AVP (from 2.2 +/- 0.7 to 7.6 +/- 2.6 pg/ml) but had no effect on swallowing activity. Fetal mean arterial blood pressure increased after injections of threshold saline and urea concentrations. Fetal arterial blood osmolality and sodium concentration did not change during any study.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1996

Coordination of breathing and swallowing: effects of bolus consistency and presentation in normal adults.

Respiration and swallowing were recorded simultaneously by inductance plethysmography, submental electromyography, and a throat microphone in 10 normal subjects during eating and drinking tasks that included single boluses of varying volume (5-20 ml) and consistency presented with a syringe and cup, a 200-ml drink taken with and without the use of a straw, and a sandwich meal. Swallows were associated with a brief swallow apnea (SA) lasting approximately 1 s. Swallow effects on the duration or tidal volume of the preswallow, postswallow and swallow-associated breathing cycles varied depending on bolus characteristics and presentation. Expiration before and after the SA was the preferred pattern with all drinking and eating tasks. Inspiration followed SA in < 5% of single-bolus swallows, but this pattern increased significantly with a 200-ml drink administered by cup or by straw and during a sandwich meal (23.8 +/- 5.2, 27.0 +/- 2.6, and 16.3 +/- 2.7%, respectively. Hence, the swallow-associated breathing pattern seen with single-bolus swallows may not reflect that associated with regular eating and drinking behavior. This finding implies that the risk of aspiration may be reduced by teaching patients prone to aspiration to simplify the complex behavior of eating and drinking to a series of single-bolus swallows.

Adult↗
PubMed2006

Swallowing function and upper airway sensation in obstructive sleep apnea.

The objective of this study was to determine whether impaired upper airway (UA) mucosal sensation contributes to altered swallowing function in obstructive sleep apnea (OSA). We determined UA two-point discrimination threshold (2PDT) and vibratory sensation threshold (VST) in 15 men with untreated OSA and 9 nonapneic controls (CL). We then assessed swallowing responses to oropharyngeal fluid boluses delivered via a catheter. The threshold volume required to provoke swallowing and the mean latency to swallowing were determined, as was the phase of the respiratory cycle in which swallowing occurred [expressed as percentage of control cycle duration (%CCD)] and the extent of prolongation of the respiratory cycle after swallowing [inspiratory suppression time (IST)]. 2PDT and VST were significantly impaired in OSA patients compared with CL subjects. 2PDT was positively correlated with swallowing latency and threshold volume in CL subjects, but not in OSA patients. Threshold volume did not differ between the groups [median value = 0.1 ml (95% confidence interval = 0.1-0.2) for OSA and 0.15 ml (95% confidence interval = 0.1-0.16) for CL], whereas swallowing latency was shorter for OSA patients [3.3 (SD 0.7) vs. 3.9 (SD 0.8) s, P = 0.04]. %CCD and IST were similar for OSA patients and CL subjects. However, among OSA patients there was a significant inverse relation between VST and IST. These findings suggest that oropharyngeal sensory impairment in OSA is associated with an attenuation of inhibitory modulating inputs to reflex and central control of UA swallowing function.

Adult↗
PubMed2005

Self-triggered functional electrical stimulation during swallowing.

Hyolaryngeal elevation is essential for airway protection during swallowing and is mainly a reflexive response to oropharyngeal sensory stimulation. Targeted intramuscular electrical stimulation can elevate the resting larynx and, if applied during swallowing, may improve airway protection in dysphagic patients with inadequate hyolaryngeal motion. To be beneficial, patients must synchronize functional electrical stimulation (FES) with their reflexive swallowing and not adapt to FES by reducing the amplitude or duration of their own muscle activity. We evaluated the ability of nine healthy adults to manually synchronize FES with hyolaryngeal muscle activity during discrete swallows, and tested for motor adaptation. Hooked-wire electrodes were placed into the mylo- and thyrohyoid muscles to record electromyographic activity from one side of the neck and deliver monopolar FES for hyolaryngeal elevation to the other side. After performing baseline swallows, volunteers were instructed to trigger FES with a thumb switch in synchrony with their swallows for a series of trials. An experimenter surreptitiously disabled the thumb switch during the final attempt, creating a foil. From the outset, volunteers synchronized FES with the onset of swallow-related thyrohyoid activity (approximately 225 ms after mylohyoid activity onset), preserving the normal sequence of muscle activation. A comparison between average baseline and foil swallows failed to show significant adaptive changes in the amplitude, duration, or relative timing of activity for either muscle, indicating that the central pattern generator for hyolaryngeal elevation is immutable with short term stimulation that augments laryngeal elevation during the reflexive, pharyngeal phase of swallowing.

Adult↗
PubMed1997

Intracellular activity of motoneurons of the rostral nucleus ambiguus during swallowing in sheep.

The nervous mechanisms that generate swallowing are still largely unknown. It has been suggested that a central pattern generator that contains a serial network of linked neurons must produce the successive excitation of motoneurons (Mns) and then the sequential activation of muscle through excitatory connections. Inhibitory connections have also been envisioned but never evidenced at the membrane level of the swallowing neurons. We investigated, by intracellular recordings, the behavior of 96 Mns in the rostral nucleus ambiguus during swallowing induced by application of superior laryngeal nerve stimulation to anesthetized sheep. The Mns were identified by antidromic activation following stimulation of glossopharyngeal, pharyngoesophageal, or cervical vagal nerves. Nine Mns showed a bell-shaped depolarization during the buccal or the early pharyngeal stage of swallowing. They probably projected to muscles of the soft palate (palatopharyngeal) and upper pharynx (stylopharyngeal, hyopharyngeal). Thirty-eight Mns exhibited a chloride-dependent hyperpolarization, indicating that they were under an active inhibition throughout the buccopharyngeal stage of swallowing. These Mns constitute a heterogeneous pool: some of them, producing spontaneous inspiratory discharges, probably innervated laryngeal or pharyngeal muscles; others might also be Mns of the esophagus, whose swallowing pattern was modified because of the anesthesia (suppression of the esophageal peristalsis). Forty-nine Mns showed a chloride-dependent hyperpolarization with a variable duration at the onset of swallowing, followed by a depolarization that could take place during either the buccopharyngeal (HD1-Mns) or the esophageal (HD2- and HD3-Mns) stage of deglutition. HD1-Mns probably projected to the median and inferior constrictors of the pharynx. HD2-Mns produced depolarizations with longer latencies and durations than those of the HD1-Mns. They probably projected to either the superior esophageal sphincter or the cervical esophagus (CE). HD3-Mns showed a buccopharyngeal hyperpolarization that was followed first by a lower-amplitude hyperpolarization accompanying the proximal CE contraction and then by a delayed depolarization. These Mns probably innervated the inferior CE or thoracic esophagus. We conclude that the initial inhibition exerted on the HD-Mns, by delaying the excitation of Mns, may play a role in the nervous mechanisms involved in temporal organization of the swallowing motor sequence. We suggest that swallowing disorders in humans such as dysphagia by failure of cricopharyngeal relaxation, diffuse esophageal spasm, and achalasia might be caused by impaired inhibitory mechanisms.

Animals↗
PubMed2001

Brain stem control of swallowing: neuronal network and cellular mechanisms.

Swallowing movements are produced by a central pattern generator located in the medulla oblongata. It has been established on the basis of microelectrode recordings that the swallowing network includes two main groups of neurons. One group is located within the dorsal medulla and contains the generator neurons involved in triggering, shaping, and timing the sequential or rhythmic swallowing pattern. Interestingly, these generator neurons are situated within a primary sensory relay, that is, the nucleus tractus solitarii. The second group is located in the ventrolateral medulla and contains switching neurons, which distribute the swallowing drive to the various pools of motoneurons involved in swallowing. This review focuses on the brain stem mechanisms underlying the generation of sequential and rhythmic swallowing movements. It analyzes the neuronal circuitry, the cellular properties of neurons, and the neurotransmitters possibly involved, as well as the peripheral and central inputs which shape the output of the network appropriately so that the swallowing movements correspond to the bolus to be swallowed. The mechanisms possibly involved in pattern generation and the possible flexibility of the swallowing central pattern generator are discussed.

Animals↗
PubMed2006

Can pulse oximetry or a bedside swallowing assessment be used to detect aspiration after stroke?

BACKGROUND AND PURPOSE: Desaturation during swallowing may help to identify aspiration in stroke patients. This study investigated pulse oximetry, bedside swallowing assessment (BSA), and videofluoroscopy as tests for detecting aspiration after stroke. METHODS: Swallowing was assessed in 189 stroke patients (mean+/-SD age, 70.9+/-12.3 years) within 5 days of symptom onset with a modified BSA (water replaced by radio-opaque contrast agent, followed by chest radiography to detect aspiration). Simultaneous pulse oximetry recorded the greatest desaturation from baseline for 10 minutes from modified BSA onset. Videofluoroscopy was undertaken in 54 (28%) patients. RESULTS: Modified BSA showed a safe swallow in 98 (51.9%), unsafe swallow in 85 (45.0%), and silent aspiration in 6 (3.2%) patients. During swallowing, desaturation by >2% occurred in 27 (27.6%) and by >5% in 3 (3.1%) of the 98 safe-swallow patients on modified BSA. Of the 85 unsafe-swallow patients, only 28 (32.9%) desaturated by >2% and 6 (7.1%) by >5%. Desaturation did not occur in any of the 6 silent aspirators. With the modified BSA to detect aspiration, sensitivity and specificity, respectively, were 0.31 and 0.72 for desaturation >2% and 0.07 and 0.97 for desaturation >5%. By videofluoroscopy, sensitivity and specificity for detecting aspiration were 0.47 and 0.72 for modified BSA, 0.33 and 0.62 for desaturation >2%, and 0.13 and 0.95 for desaturation >5%. Combining a failed modified BSA with desaturation >2% or >5% did not significantly improve predictive values. CONCLUSIONS: Modified BSA and pulse oximetry during swallowing, whether alone or in combination, showed inadequate sensitivity, specificity, and predictive values for detection of aspiration compared with videofluoroscopy in stroke patients.

Aged↗
PubMed1984

The volume of saliva in the mouth before and after swallowing.

In 20 male and 20 female adult subjects, the volume of saliva in the mouth before (VMAX) and after (RESID) swallowing was determined. RESID could be computed by measuring the potassium and chloride concentrations in unstimulated saliva and in the expectorate after a five-second rinse with 5 ml of water immediately following a swallow. The mean value of RESID after a normal swallow was significantly higher in males (0.87 ml) than in females (0.66 ml). After a forced swallow, RESID was only slightly but significantly reduced, being 0.82 ml and 0.60 ml in males and females, respectively. The volume of saliva normally swallowed was calculated from the unstimulated salivary flow rate and the normal swallowing frequency. The mean value of VMAX (RESID plus volume normally swallowed) in males was 1.19 ml, which was slightly but not significantly higher than that in females (0.96 ml). When water was infused into the mouth at increasing flow rates, there was an increase in VMAX and in both the volume of fluid swallowed and the swallowing frequency.

Adolescent↗
PubMed2001

[Swallowing rehabilitation in two elderly patients with cerebral infarction].

We report two cases of cerebral infarction in which swallowing function improved following swallowing rehabilitation. Patient 1 was an 82-year-old man, who was admitted due to rheumatoid arthritis and multiple cerebral infarction, suffering from aspiration pneumonia. The abnormality of swallowing was assessed by the water swallowing test and videofluorography. It has been reported that videofluorography is useful in the diagnosis of aspiration. Three weeks after the start of swallowing rehabilitation, the serum level of inflammatory markers and the chest X-ray had returned to normal. His score on the water swallowing test had improved. Patient 2 was a 68-year-old [correction of 62] man, who was admitted with severe hemiplegia, dysphagia and dysarthria. One month after the swallowing rehabilitation, videofluorography showed that the magnitude of aspiration into the trachea had decreased and the pooling of barium in the piriform sinus had disappeared. The patient could begin taking a little food by mouth. These results suggest that swallowing rehabilitation will be affect the clinical improvement of swallowing function and help preventing aspiration pneumonia in our hospital.

Activities of Daily Living↗
PubMed2006

[Relationships of swallowing function to changes in motor functions in stroke patients with motor dysphagia].

AIM: To clarify the clinical features of physical therapy for motor dysphagia by identifying changes in indices when swallowing function changes. METHOD: Subjects comprised 59 stroke patients with motor dysphagia. They were subdivided into 3 groups according to changes in swallowing function (Group A: improved, Group B: deteriorated. Group C: unchanged). Measured indices for swallowing movement consisted of 4 items; distance from the genion to the thyroid cartilage (GT), distance from the thyroid cartilage to the sternum (TS), relative thyroid position (GT/(GT + TS)), and strength of the suprahyoid muscles (GS grade). Measured indices for neck-trunk function consisted of the passive neck range of motion in 4 directions (flexion, extension, lateral flexion, and rotation), and neck-trunk-pelvis stage (NTP stage) as described by Yoshio. Measured indices for swallowing function were the repetitive saliva swallowing test, the modified water swallowing test, the food test, and Saitoh's classification of dysphagia. RESULTS: Group A consisted of 30 patients (mean age, 68.1 years), Group B consisted of 6 patients (mean age, 78.7 years), Group C consisted of 23 patients (mean age, 73.0 years). Group A exhibited significant improvements in GS grade, NTP stage, neck extension and rotation. In Group B, only relative thyroid position was affected. In Group C, no changes were evident. CONCLUSION: To obtain improved swallowing function, approaches aimed at both local function of swallowing muscles and neck-trunk function should be used. Preventing deterioration of swallowing function requires attention to thyroid position affected by inappropriate posture.

Aged↗
PubMed1991

[Subclinical swallowing disorder in patients with abnormal sensation in the throat].

Measurement of swallowing pressure was done in 75 patients who complained of abnormal sensation such as obstructive sensation, difficulty in swallowing, etc. in the throat without noticeable cause. Abnormal swallowing pressure curves were observed in 33 patients (44%), and 76% of them showed abnormal elevation of the pressure at the hypopharyngeal or cervical esophageal region. These results indicated that subclinical swallowing disorder, particularly abnormal high swallowing pressure, can be a possible cause of their complaints. The author assumed that abnormal elevation of swallowing pressure is due to hypertonicity of the hypopharyngeal and cervical esophageal muscles. By the animal experiments using dog, a muscle relaxant, eperizone hydrochloride, revealed to change muscle tonus of the hypopharyngoesophageal muscles. Intravenous administration of the drug decreased swallowing pressure and prolonged the relaxation time of the cricopharyngeal muscle. Clinically the muscle relaxant showed to be effective in ameliorating the complaint of the patients with abnormal high swallowing pressure at the hypopharyngeal or cervical esophageal region. Based on the above results, the author proposed that the clinical entity, hypopharyngeal-cervical esophageal hypertonicity, causes a subclinical swallowing disorder leading to the abnormal sensation in the throat.

Adult↗
PubMed1999

[Effects of wearing complete dentures on swallowing in the elderly].

The purpose of this study was to evaluate effects of wearing complete dentures on swallowing in the elderly. Sixteen nondysphagic edentulous volunteers (mean age: 75.0 yrs) were studied in terms of surface electromyography of the anterior belly of digastrics and masseter muscles, tongue pressure toward the hard palate, and the laryngeal movement. The subjects swallowed 2 ml water under four conditions, with upper and lower dentures, without lower denture, without upper denture, and without upper and lower dentures. Dipper-type of swallowing was prescribed. A repeated-measures ANOVA was used for statistical analysis. Total swallowing duration and the latent period until laryngeal elevation were significantly prolonged without upper or lower denture, and without both dentures (p < 0.05). They were significantly shorter without lower denture than those without upper denture, and without both dentures (p < 0.05). Duration of the preparatory stage was significantly prolonged without upper denture, and without both dentures comparing with the others (p < 0.05). Duration of the oral stage was significantly prolonged without upper denture, and without both dentures comparing with the duration with both dentures (p < 0.05). There were no changes in the pharyngeal stage with or without dentures. The prolongation of total swallowing duration was due to the prolongation of the preparatory and oral stages. The prolongation of swallowing would affect the oral-pharyngeal coordination of swallowing, and exacerbate the depression of swallowing functions with aging. These results suggested that wearing complete dentures contributes to maintain physiological procedure of swallowing in the elderly.

Aged↗
PubMed2004

[The relationship between wearing complete dentures and swallowing function in elderly individuals: a videofluorographic study].

The role of complete dentures in masticatory function is well established, but their effect on swallowing has been little examined. This study investigated the effect of complete dentures on swallowing in the elderly. Lateral projection videofluorography (VF) was performed for nine healthy edentulous elderly volunteers (mean age 73.9 +/- 2.9 years) while they swallowed 8 ml of liquid and paste barium with and without complete dentures. A total of 35 VF records were analyzed for temporal and spatial measurements of oropharyngeal motion during swallowing. The tongue tip contacted the inside of the lip between the upper and lower alveolar ridges during swallowing without but not with complete dentures. The hyoid moved further upward (P = 0.002) during swallowing without dentures (liquid: 5.85 +/- 3.99 mm, paste: 6.41 +/- 5.25 mm) than with dentures (liquid: 3.70 +/- 4.57 mm, paste: 3.69 +/- 4.07 mm). The larynx moved further forward (P = 0.044) during swallowing without dentures (liquid: 6.39 +/- 2.58 mm, paste: 6.46 +/- 2.87 mm) than with dentures (liquid: 5.34 +/- 2.04 mm, paste: 5.93 +/- 1.50 mm). The timing of the movements of these structures was not affected by the presence of the dentures or bolus consistency. These results showed that the hyoid and larynx moved more in swallowing without than with complete dentures, perhaps because of tongue tip protrusion when not wearing dentures. These findings suggest that complete dentures have a significant effect on swallowing function as well as masticatory function in elderly individuals.

Aged↗
PubMed2003

Association between sleep bruxism, swallowing-related laryngeal movement, and sleep positions.

STUDY OBJECTIVE: To describe the relationships of sleep bruxism to swallowing and sleep positions. DESIGN: Controlled descriptive study. SETTING: Polysomnography and audio-video recordings were done in a hospital sleep laboratory. PARTICIPANTS: Nine patients with sleep bruxism and 7 normal subjects were matched for age and sex. INTERVENTIONS: n/a. MEASUREMENTS AND RESULTS: During sleep, patients with sleep bruxism showed a higher frequency of rhythmic masticatory muscle activity episodes (6.8 +/- 1.0 [SEM]/h) than did normals (0.5 +/- 0.1/h, p < 0.01). Swallowing-related laryngeal movements occurred more frequently in sleep of patients with sleep bruxism (6.8 +/- 0.8/h) than in normals (3.7 +/- 0.3/h, p < 0.01). In both groups, during sleep, close to 60% of rhythmic masticatory muscle activity episodes were associated with swallowing. In sleep bruxism patients, 68% of swallowing events occurred during rhythmic masticatory muscle activity episodes, while only 10% of swallowing events were associated with rhythmic masticatory muscle activity in normal subjects. Sleep bruxism patients and normals spent 95.5% and 87.3% of sleeping time in the supine and lateral decubitus positions, respectively. In both groups, up to 96% of rhythmic masticatory muscle activity and swallowing were observed in the supine and lateral decubitus position. In sleep bruxism patients, although sleeping time did not differ between the 2 sleeping body positions, 74% of rhythmic masticatory muscle activity and swallowing events were scored in the supine position compared to 23% in the lateral decubitus position. CONCLUSIONS: During sleep, rhythmic masticatory muscle activity is often associated with swallowing. In sleep bruxism patients, most of these oromotor events are observed in the supine position. The physiologic link between rhythmic masticatory muscle activity and swallowing and the clinical relevance of sleep position in sleep bruxism management need to be investigated.

Adult↗
PubMed1987

How many swallows are required to establish reliable esophageal peristaltic parameters in normal subjects? An on-line computer analysis.

Esophageal manometric parameters are often examined using from four to 10 or more swallows to obtain a manometric profile without addressing the question of the reproducibility of these data. We asked the question of "how much is enough?" by statistically comparing five sets of 10 wet swallows (5 ml) each separated by 20 min in eight volunteers using constant infusion manometry. Peristaltic waves were evaluated for amplitude, duration, and velocity using an on-line computer program. Statistical analyses included analysis of variance and the Newman-Keuls test for uniformity among sets of swallows. The sets of 10 swallows showed no evidence of a training effect over time. Less than 5% of all comparisons (Newman-Keuls) showed significant differences. Using 5% variability outside of 1 SD as a cutoff (95% confidence interval) amplitude of normal wet swallows could be adequately defined by more than or equal to five swallows and velocity by more than or equal to seven swallows. Duration shows the greatest overall variability and required more than or equal to eight swallows for accurate assessment. These data suggest that at least five to eight wet swallows should be performed to describe "typical" manometry parameters for normal subjects.

Adult↗
PubMed2006

Trace element concentrations and bioindicator responses in tree swallows from northwestern Minnesota.

Extremely high concentrations of cadmium (3.5 microg/g dry wgt.) and elevated concentrations of chromium (>10 microg/g dry wgt.) and mercury (1.6 microg/g dry wgt.) were reported in waterbird tissues at Agassiz National Wildlife Refuge in northwestern Minnesota in 1994. Tree swallows (Tachycineta bicolor) were studied during 1998-2001 at three drainages into the Refuge, two pools on the Refuge, and at a nearby reference location to document whether high levels of contaminants were still present, and if so to quantify the source and severity of the contamination. Trace elements were measured in tree swallow eggs, livers, and diet. Reproductive success and bioindicator responses were monitored. In 2000, water was drawn down on Agassiz Pool, one of the main pools on the Refuge. This presented an opportunity to evaluate the response of trace element concentrations in the diet and tissues of tree swallows after reflooding. High concentrations of trace elements were not detected in swallow tissues, nor were there differences among locations. Less than 20% of swallow samples had detectable concentrations of cadmium or chromium. Mercury concentrations were low and averaged <0.25 microg/g dry wgt. in swallow tissues. Trace elements, including mercury, did not increase in tree swallows following the 2000 drawdown at Agassiz Pool. Hatching success and survival of nestlings to 12 days-of-age for tree swallows on the Refuge were similar to the national average and consistent with background trace element concentrations. Bioindicator measurements were within the normal ranges as well.

Animals↗
PubMed2004

Accumulation of PCB congeners in nestling tree swallows (Tachycineta bicolor) on the Hudson River, New York.

Tree swallows (Tachycineta bicolor) were used as a sentinel species to monitor the contamination and bioavailability of polychlorinated biphenyls (PCBs) in the Hudson River watershed. Several tree swallow nest box colonies around and downstream from Hudson Falls, NY, were studied. Tree swallow eggs, adults, and 5-, 10-, and 15-day-old nestlings were collected and analyzed for 103 PCB congeners. Emergent insects collected by net (primarily Odonata) or as a food bolus (primarily Diptera) taken from the mouths of adult tree swallows returning to the nest were analyzed in the same manner. Total PCB concentrations (wet weight) in eggs from two contaminated sites ranged from 9000 to 25,000 ng/g and accumulated to 32,000 and 96,000 ng/g in 15-day-old nestling at two contaminated sites. The congener patterns of PCBs in eggs, nestlings, and adults were compared to those found in emergent insects (Odonata and Diptera) using principal components analysis. The PCB patterns of the biota differed from that of Aroclor technical mixtures. PCB patterns in adult tree swallows were similar to those in eggs, while the patterns in dietary insects were similar to nestling tree swallows. Uptake rate constants were determined for tree swallow nestlings and compared between the two contaminated sites. The estimated PCB congener uptake rate constants were 0.008-0.02 d(-1) based on uptake in nestlings until day 15 post-hatch. The rate constants were comparable between the two study areas and may be used to predict nestling contamination at other locations. Our studies confirm the utility of nestling tree swallows to evaluate localized PCB contamination.

Animals↗