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Biomedical subjects

D Bartlett

Publications and source records attributed to D Bartlett.

At least 55 records · Page 3Linked to original sources
PubMed1996

Complete resection of the caudate lobe of the liver: technique and results.

The caudate lobe of the liver is a frequent site of involvement by metastatic or primary liver tumours. This study describes the surgical anatomy and analyses the operative technique, results and postoperative morbidity of complete caudate lobectomy. The data represent a retrospective review of 21 consecutive complete caudate lobe resections performed over a 30-month period. The most common diagnosis was metastatic colorectal cancer (nine patients) and the most common procedure was extended left hepatic lobectomy with en bloc caudate lobectomy. Four patients underwent isolated complete caudate lobe resection. The median operating time was 5 h and the median blood loss was 1160 ml. The major complication rate was 38 per cent (nine major complications in eight patients) with 10 per cent mortality rate (two deaths). The median hospital stay was 11 days. This series demonstrates the feasibility of routine complete caudate lobe resection for tumours with general principles of liver resection. Isolated caudate lobectomy can be performed safely and the addition of caudate lobectomy to major liver resection does not add significantly to the morbidity or mortality of the procedure.

Adult↗
PubMed1996

Respiratory motor nerve activities during experimental seizures in cats.

We evaluated respiratory motor nerve activities during experimental seizures induced with subcortical penicillin. The activities of the phrenic (PH), nasolabial (NL), and hypoglossal (HG) nerves and the recurrent laryngeal motor branches to the thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles were analyzed in 13 anesthetized, vagotomized, paralyzed, and ventilated cats. During ictal and interictal phases of seizures, nerve activities became irregular and peak integrated nerve activities increased, particularly in the case of the PH nerve. The ictal phase of seizures was associated with increased tonic activity and decreased phasic respiratory discharges, particularly in the cases of the HG, NL, and PCA nerves. During some prolonged ictal discharges, entrainment of nerve activities by cortical spiking was associated with irregular uncoordinated activation, particularly in the TA nerve. These studies help explain respiratory impairment during seizures by providing evidence of impaired coordination between activation of muscles that regulate upper airway patency and activation of the diaphragm.

Animals↗
PubMed1996

Clinical investigations of gastro-oesophageal reflux: Part 1.

Most people have at some time experienced the symptoms of heartburn associated with gastro-oesophageal reflux. Fortunately, these symptoms are usually short-lived and require no treatment, but in some patients severe and prolonged reflux of gastric juice into the mouth can cause dental erosion. This paper, the first in a two-part series, describes the aetiology of gastro-oesophageal reflux and associated problems that may be encountered.

Esophagogastric Junction↗
PubMed1995

The kinetics of the oxidation of L-ascorbic acid by peroxynitrite.

Peroxynitrite [O = NOO-, oxoperoxonitrate(1-)bd is a strong oxidant that may be formed in vivo by the reaction of O2.- and NO(.). Oxoperoxonitrate(1-) reacts with molecules in aqueous acidic solutions via pathways that involve the highly reactive hydrogen oxoperonitrate either as an intermediate in a first-order reaction or as a reactive agent in a simple second-order reaction. ESR experiments show that hydrogen oxoperoxonitrate oxidizes monohydrogen L-ascorbate by one electron: when mixed at pH ca. 5 and passed through a flow cell within 0.1 s, the two-line ESR signal of the ascorbyl radical anion (aH = 0.18 T, g = 2.005) is observed. The overall stoichiometry of the reaction was 1 mol of ascorbate oxidized per mol of oxoperoxonitrate(1-) added. The kinetics of the reaction were studied over the pH range 4.0-7.5 by stopped-flow spectrometry. Hydrogen oxoperoxonitrate, observed between 300 and 350 nm, and the oxoperoxonitrate(1-) anion, at 302 nm, disappear faster than predicted for the first-order isomerization to NO3-. The rate increases from pH 4 to 5.8, and then decreases with increasing pH. The rate variation suggests a bimolecular reaction either between the oxoperoxonitrate(1-) anion and ascorbic acid or between hydrogen oxoperoxonitrate and the monohydrogen ascorbate anion. Although the two pathways are kinetically indistinguishable, the pKa values of ascorbic acid and hydrogen oxoperoxonitrate strongly suggest that the reacting species are hydrogen oxoperoxonitrate and monohydrogen ascorbate. The second-order rate constant for this reaction is 235 +/- 4 M-1s-1 at 25 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Ascorbic Acid↗
PubMed1994

Genetic characterization of ompH mutants in the deep-sea bacterium Photobacterium sp. strain SS9.

OmpH is an outer membrane protein produced by the deep-sea bacterium Photobacterium species strain SS9 in response to elevated hydrostatic pressure. In order to facilitate studies of the function of this protein, a series of OmpH+ and OmpH- strains were obtained from SS9 by Tn5 gene replacement mutagenesis. A previously isolated ompH::lacZ strain and a derivative of this strain harboring a plasmid expressing the wild-type ompH gene were also utilized. The acridine mutagen ICR 191 preferentially inhibited the growth of OmpH+ over OmpH- cells. Indeed, OmpH+ cultures treated with the mutagen rapidly accumulated mutants producing reduced levels of OmpH. In addition, OmpH+ cells took up the peptide Met-Leu-Phe approximately 15 times more rapidly than OmpH- cells. The results are consistent with the hypothesis that OmpH functions as a relatively large, nonspecific diffusion channel.

Aminacrine↗
PubMed1994

Influence of hypoxia on ventilatory responses to intralaryngeal CO2 in cats.

In decerebrate, vagotomized cats, introduction of CO2 into the isolated laryngeal airway while systemic PCO2 is held constant evokes dose-related reflex changes in ventilatory activity. Because systemic hypoxia is known to exaggerate ventilatory responses to other types of laryngeal chemostimulation in neonates, we have compared the responses of phrenic and hypoglossal nerve activities to ventilation of the larynx with 10% CO2 during systemic hyperoxia (FIO2 = 1.00) to those during hypoxia (FIO2 = 0.12). Compared with the hyperoxic baseline condition, hypoxia stimulated phrenic activity but attenuated the reduction in phrenic activity evoked by intralaryngeal CO2. Hypoglossal activity was increased by intralaryngeal CO2 and this response appeared to be reduced by hypoxia, but neither of these findings was statistically significant. The response of phrenic activity to intralaryngeal CO2 during systemic hypercapnia was similar to that during hypoxia. The increase of phrenic activity in response to hypoxia was prevented by carotid body resection. Similarly, the hypoxic attenuation of the phrenic response to intralaryngeal CO2 appeared to be absent after carotid body resection, although this finding was not established statistically. These results differ from previous reports of exaggerated laryngeal chemoreflex responses during hypoxia. The difference may reflect differences in the receptors and synaptic mechanisms of the reflexes, the severity and time course of hypoxia or the presence or depth of general anesthesia or sleep.

Animals↗
PubMed1994

Respiratory motor nerve activities during spontaneous bladder contractions.

We monitored spontaneous bladder contractions (SBCs) in decerebrate vagotomized paralyzed ventilated cats while recording respiratory motor nerve activities and intravesical pressure under isovolumetric conditions. Phrenic nerve discharge diminished during SBCs, as did the activities of the hypoglossal nerve, the nasolabial branch of the facial nerve, and inspiratory (posterior cricoarytenoid) and expiratory (thyroarytenoid) branches of the recurrent laryngeal nerve. Hypoglossal activity was most strikingly reduced during SBCs, disappearing completely in some animals. The triangularis sterni nerve exhibited an initial decrease, followed by an increase in activity during SBCs, whereas the cranial iliohypogastric nerve showed increased activity. The changes in nerve activities during SBCs could also be elicited by passive distension of the bladder and were abolished by bilateral section of the pelvic nerves. These findings extend the understanding of reflexes originating from the urinary bladder to include a coordinated respiratory response and suggest that these reflexes may compromise upper airway patency under some conditions.

Animals↗
PubMed1994

What scares patients about the hospital.

Hospitalization usually disrupts a person's privacy, autonomy, life style, roles, and finances. This article discusses the anxieties a patient can experience related to future uncertainties, insufficient information, fear of personal incompetence, being exposed to hospital rumors, and anticipated pain. Interventions to reduce patient anxiety are suggested.

Anxiety↗
PubMed1992

Anti-neoplastic effects of interleukin-4.

Interleukin-4 (IL-4) is a cytokine, with potential anti-neoplastic effects. This study examined the effects of IL-4 on host anti-tumor responses in a murine model. C57/B16 mice (n = 40) were randomized to receive Lewis lung carcinoma (10(6) cells: right flank; sc) or saline, and sacrificed 10 days postinoculation for assessment of peritoneal macrophage (PMO) anti-tumor mechanisms [superoxide anion generation (O2-), tumor necrosis factor (TNF), and TNF-independent (P815) cytotoxicity], splenocyte mixed lymphocyte response (MLR) (Balb/c stimulator), and cytotoxic lymphocyte generation (CTL against P815). Cells were cultured +/- IL-4 (100 U/ml). In a second study, 20 mice received Lewis lung implants (sc) and were randomized on Day 21 to receive daily IL-4 (1000 U/mouse; ip) or saline. Tumor volumes and median survival were assessed. Tumor necrosis factor-independent cytotoxicity (O2-, MLR and CTL) was impaired in the tumor-bearing (TB) study group. Interleukin-4 administered to cultured cells from TB mice enhanced O2-, as well as MLR and CTL (P less than 0.01), and decreased TNF release but did not alter PM phi TNF-independent anti-tumor responses (P815). In vivo administration of IL-4 significantly decreased tumor growth (P less than 0.05) after 10 days of treatment and significantly prolonged median host survival (P less than 0.05). These findings indicate the therapeutic potential of IL-4 in the TB host which may function through downregulation of TNF production while potentiating certain T cell-dependent and independent anti-tumor immune mechanisms.

Animals↗
PubMed1992

Activity of abdominal muscle motoneurons during hypercapnia.

Our purpose was to examine the influence of hypercapnia on the activity of motoneurons innervating the transversus abdominis and internal oblique abdominal muscles, and of integrated phrenic and abdominal motor nerve activities. Studies were done in nine adult cats that were decerebrated, vagotomized, thoracotomized, paralyzed and ventilated mechanically. Of 42 motoneurons examined, 24 showed strong respiratory modulation (RM neurons), with the discharge confined primarily to the central expiratory period. The remaining 18 motoneurons discharged tonically, and failed to show respiratory modulation even at increased levels of central respiratory drive. Hyperoxic hypercapnia augmented the activities of the phrenic and abdominal nerves and increased the early expiratory discharge frequency of the RM neurons. The hypercapnia-induced increase in firing frequency during early expiration was accompanied by a corresponding decline in late expiration, and a virtual abolition of the inspiratory activity in the few neurons that discharged in this phase under normocapnic conditions. Finally, hypercapnia induced an increase in the number of spikes generated during each expiratory period in about half of the RM neurons, whereas the remaining cells showed a decrease. Thus, the increased peak activity of the integrated whole abdominal nerve burst with hypercapnia was brought about by a shift in the temporal pattern of motoneuron firing, or by an increase in the number of spikes generated during the expiratory period. The steep rate of rise and the pronounced early expiratory peak observed in the integrated abdominal nerve burst during hypercapnia in this preparation are consistent with the increase in motoneuron firing frequency during the early stages of the expiratory phase.

Abdominal Muscles↗
PubMed1992

Phrenic and hypoglossal neural responses to cold airflow in the upper airway.

Cold air flowing through the larynx is known to alter the activities of laryngeal receptors with afferents in the superior laryngeal nerves (SLNs) and to induce reflex apnea in neonatal mammals. To examine the ventilatory response in adult animals and to explore associated upper airway motor responses, we recorded phrenic and hypoglossal neural responses to cooling the isolated larynx with cold air in decerebrate, vagotomized, paralyzed, ventilated cats. The most consistent response was phrenic inhibition, which occurred in all animals tested. Either excitation or inhibition of hypoglossal activity was seen consistently in individual cats, with the result that the group response was not statistically significant. All responses to laryngeal cooling were abolished by section of the SLNs. The findings confirm that directing cold air through the larynx causes reflex inhibition of ventilatory (phrenic) activity, but raise new questions as to how the two, directionally opposite hypoglossal responses are mediated.

Animals↗
PubMed1992

Influence of laryngeal CO2 on respiratory activities of motor nerves to accessory muscles.

Intralaryngeal CO2 in decerebrate, vagotomized cats decreases phrenic nerve activity and increases the respiratory activity of the hypoglossal (HG) nerve. These responses are mediated by afferents in the superior laryngeal nerves. To explore the responses of other respiratory motor nerves to this stimulus, we have recorded the activities of the nasolabial (NL) branch of the facial nerve, the posterior cricoarytenoid (PCA) and thyroarytenoid (TA) branches of the recurrent laryngeal nerve and the nerve to triangularis sterni (TS) muscle. In response to 5 and 10% CO2 in the surgically isolated upper airway, we found dose-related decreases in phrenic activity, increases in HG and NL activity and characteristic, but intermittent, exaggeration of early expiratory bursts of TA activity. The activities of the PCA and TS nerves showed no consistent responses. These results broaden the definition of the reflex response to intralaryngeal CO2, revealing components that reflect ventilatory inhibition, upper airway dilation and laryngeal protection.

Animals↗
PubMed1992

Alteration of ventilatory activity by intralaryngeal CO2 in the cat.

1. We investigated the responses of phrenic and hypoglossal nerve activities to the addition of 3, 5 and 10% CO2 to a constant flow of warm, humidified air through the isolated upper airway in decerebrate, paralysed, artificially ventilated cats. 2. In bilaterally vagotomized animals, intralaryngeal CO2 caused a dose-related decrease in peak integrated phrenic activity. This response became attenuated with time, but was still discernible after 3 min of continuous intralaryngeal CO2. In the same experiments, intralaryngeal CO2 caused a gradual increase in peak integrated hypoglossal nerve activity. 3. Intermittent pulsing of intralaryngeal CO2 during neural inspiration or expiration resulted in similar, but smaller decreases in the phrenic activity of some animals. Hypoglossal activity was not influenced appreciably by this procedure. 4. Systemic hypercapnia attenuated the phrenic responses to intralaryngeal CO2. The hypoglossal responses were greatly reduced or abolished. 5. In vagally intact cats, ventilated by a servo-respirator in accordance with phrenic nerve activity, intralaryngeal CO2 resulted in only a trace of reduction in phrenic discharge. After bilateral vagotomy, the same animals showed typical responses, as described above. 6. All responses to intralaryngeal CO2 were abolished after bilateral section of the superior laryngeal nerves (SLNs). 7. We conclude that intralaryngeal CO2 acts by way of receptors with afferents in the SLNs to decrease phrenic and increase hypoglossal nerve activities. The responses are not importantly gated during neural inspiration or expiration. The responses to intralaryngeal CO2 are most clearly demonstrable after bilateral vagotomy, suggesting that vagal mechanisms serve to stabilize respiratory motor neural activity in intact animals.

Animals↗
PubMed1992

Responses of laryngeal receptors to intralaryngeal CO2 in the cat.

1. We recorded afferent activities of single fibres in the superior laryngeal nerves of decerebrate or anaesthetized, paralysed cats while 3, 5 and 10% CO2 was added to a constant flow of warm, humidified air through the isolated upper airway. 2. Fifty-three receptors with discharge frequencies modulated by intralaryngeal CO2 were studied. Of these, forty-eight showed CO2-induced attenuation of their firing rates. Pulses of 3, 5 or 10% CO2, alternating with air at intervals ranging from 1.5 to 60 s, also diminished the discharge frequencies. This diminution was greater with higher CO2 concentrations and longer pulse durations. 3. Five of the fifty-three receptors were stimulated by intralaryngeal CO2. The discharge frequencies of these units increased slowly and by only a few impulses per second during CO2 exposure. 4. Thirty-four of the CO2-sensitive receptors were tested with other stimuli, including water, saline, positive and negative intralaryngeal pressures and cold air. The responses to these stimuli varied among receptors, but many of the units that reduced their frequencies with intralaryngeal CO2 were consistently stimulated by positive and/or negative intralaryngeal pressures. 5. Thirty-six of the receptors were anatomically located by probing the upper airway. Twenty-six were in the larynx, and ten were in the rostral trachea, within 5 mm of the cricoid cartilage. 6. The results, which are directly applicable to the investigation of reflex responses reported in the preceding paper, indicate that the predominant initial response to intralaryngeal CO2 under the conditions of these studies is attenuation of laryngeal receptor activity.

Animals↗
PubMed1992

Dependence of pharyngeal resistance on genioglossal EMG activity, nasal resistance, and airflow.

We investigated the quantitative relationships among pharyngeal resistance (Rph), genioglossal electromyographic (EMGge) activity, nasal resistance (Rna), and airflow in 11 normal men aged 19-50 while they were awake. We made measurements with subjects seated with the head erect, seated with the head flexed forward approximately 40 degrees, and supine. Each subject wore a face mask connected to a pneumotachograph to measure airflow. After topical anesthesia of the nose, two catheters for measuring nasal and pharyngeal airway pressures were passed through one nostril: the nasal pressure catheter was positioned at the nasal choanae, and the pharyngeal pressure catheter was positioned just above the epiglottis. We measured EMGge activity with an intraoral surface electrode. The subjects breathed exclusively through the nose while inhaling room air or rebreathing CO2. We measured Rph, Rna, airflow, and EMGge activity at approximately 90-ms intervals throughout each inspiration. Rph was invariant as head position was changed. At any given head position, EMGge activity rose as airflow increased, and Rph remained constant. In contrast, Rna increased as airflow increased. Because Rph was constant, EMGge activity was not correlated with Rph, but EMGge was positively correlated with Rna and airflow. On the basis of the stability of Rph in the face of marked changes in collapsing forces, we conclude that the dynamic interplay of posture, head and jaw position, and upper airway muscle activity quite effectively maintains pharyngeal patency, and interactions among these factors are subtle and complex.

Adult↗