Individual and combined impacts of carbon dioxide enrichment, heatwaves, flow velocity variability, and fine sediment deposition on stream invertebrate communities.

Climate change and land-use change are widely altering freshwater ecosystem functioning and there is an urgent need to understand how these broad stressor categories may interact in future. While much research has focused on mean temperature increases, climate change also involves increasing variability of both water temperature and flow regimes and increasing concentrations of atmospheric CO2, all with potential to alter stream invertebrate communities. Deposited fine sediment is a pervasive land-use stressor with widespread impacts on stream invertebrates. Sedimentation may be managed at the catchment scale; thus, uncovering interactions with these three key climate stressors may assist mitigation of future threats. This is the first experiment to investigate the individual and combined effects of enriched CO2, heatwaves, flow velocity variability, and fine sediment on realistic stream invertebrate communities. Using 128 mesocosms simulating small stony-bottomed streams in a 7-week experiment, we manipulated dissolved CO2 (ambient; enriched), fine sediment (no sediment; 300 g dry sediment), temperature (ambient; two 7-day heatwaves), and flow velocity (constant; variable). All treatments changed community composition. CO2 enrichment reduced abundances of Orthocladiinae and Chironominae and increased Copepoda abundance. Variable flow velocity had only positive effects on invertebrate abundances (7 of 13 common taxa and total abundance), in contrast to previous experiments showing negative impacts of reduced velocity. CO2 was implicated in most stressor interactions found, with CO2 × sediment interactions being most common. Communities forming under enriched CO2 conditions in sediment-impacted mesocosms had ~20% fewer total invertebrates than those with either treatment alone. Copepoda abundances doubled in CO2-enriched mesocosms without sediment, whereas no CO2 effect occurred in mesocosms with sediment. Our findings provide new insights into potential future impacts of climate change and land use in running freshwaters, in particular highlighting the potential for elevated CO2 to interact with fine sediment deposition in unpredictable ways.

Measurement of functional residual capacity by modified multiple breath nitrogen washout for spontaneously breathing and mechanically ventilated patients.

BACKGROUND: There is a need for a bedside functional residual capacity (FRC) measurement method that performs well in intensive care patients during many modes of ventilation including controlled, assisted, spontaneous, and mixed. We developed a modified multiple breath nitrogen washout method for FRC measurement that relies on end-tidal gas fractions and alveolar tidal volume measurements as inputs but does not require the traditional measurements of volume of nitrogen or oxygen. Using end-tidal measurements, not volume, reduces errors from signal synchronization. This study was designed to assess the accuracy, precision, and repeatability of the proposed FRC system in subjects with variable ventilation patterns including some spontaneous effort. METHODS: The accuracy and precision of measurements were assessed by comparing the novel N2 washout FRC values to the gold standard, body plethysmography, in 20 spontaneously breathing volunteers. Repeatability was assessed by comparing subsequent measurements in 20 intensive care patients whose lungs were under controlled and assisted mechanical ventilation. RESULTS: Compared with body plethysmography, the accuracy (mean bias) of the novel method was -0.004 litre and precision [1 standard deviation (sd)] was 0.209 litre [mean (sd)] [-0.1 (5.9)% of body plethysmography]. The difference between repeated measurements was 0.009 (0.15) litre [mean (sd)] [0.4 (6.4)%]. The coefficient of repeatability was 0.31 litre (12.7%). CONCLUSIONS: The modified multiple breath nitrogen washout method for FRC measurement provides improved precision and equivalent accuracy and repeatability compared with existing methods during ventilation with variable ventilation patterns. Further study of the novel N2 washout method is needed.

Inhibition of thromboxane A2-induced arrhythmias and intracellular calcium changes in cardiac myocytes by blockade of the inositol trisphosphate pathway.

We have recently reported that left atrial injections of the thromboxane A(2) (TXA(2)) mimetic, (5Z)-7-[(1R,4S,5S,6R)-6-[(1E,3S)-3-hydroxy-1-octenyl]-2 -oxabicyclo[2.2.1]hept-5-yl]-5-heptenoic acid (U46619), induced ventricular arrhythmias in the anesthetized rabbit. Data from this study led us to hypothesize that TXA(2) may be inducing direct actions on the myocardium to induce these arrhythmias. The aim of this study was to further elucidate the mechanism responsible for these arrhythmias. We report that TXA(2)R is expressed at both the gene and protein levels in atrial and ventricular samples of adult rabbits. In addition, TXA(2)R mRNA was identified in single, isolated ventricular cardiac myocytes. Furthermore, treatment of isolated cardiac myocytes with U46619 increased intracellular calcium in a dose-dependent manner and these increases were blocked by the specific TXA(2)R antagonist, 7-(3-((2-((phenylamino)carbonyl)hydrazino)methyl)-7-oxabicyclo(2.2.1)hept-2-yl)-5-heptenoic acid (SQ29548). Pretreatment of myocytes with an inhibitor of inositol trisphosphate (IP(3)) formation, gentamicin, or with an inhibitor of IP(3) receptors, 2-aminoethoxydiphenylborate (2-APB), blocked the increase in intracellular calcium. In vivo pretreatment of anesthetized rabbits with either gentamicin or 2-APB subsequently inhibited the formation of ventricular arrhythmias elicited by U46619. These data support the hypothesis that TXA(2) can induce arrhythmias via a direct action on cardiac myocytes. Furthermore, these arrhythmogenic actions were blocked by inhibitors of the IP(3) pathway. In summary, this study provides novel evidence for direct TXA(2)-induced cardiac arrhythmias and provides a rationale for IP(3) as a potential target for the treatment of TXA(2)-mediated arrhythmias.

Cerebrovascular response to acute decreases in arterial PO2.

The purpose of these studies was to examine the time course of the cerebrovascular response to acute hypoxia in unanesthetized ponies. An electromagnetic flow transducer chronically placed on the internal carotid artery of the pony allowed continuous recording of internal carotid artery blood flow (ICBF) which has been shown to be representative of cerebral blood flow (CBF). The ponies were subjected to three levels of acute isocapnic hypoxia (PaO2 = 62, 44, and 39 mm Hg for hypoxia level I, II, and III, respectively), and the temporal and steady-state cerebrovascular response was examined. ICBF increased significantly at all three hypoxia levels (8, 25, and 40% at hypoxia I, II, and III, respectively). This increase was rapid in the two most severe levels of hypoxia, beginning within 45 s, and was complete within 90 s. The increase lagged behind the reduction in PaO2 by 24-28 s. During the very mild level of hypoxia (I), no such rapid increase in flow was observed; rather, the increase occurred only after 5 min of hypoxia. Microsphere (15 microns diameter) measurements from six ponies during the most severe level of hypoxia (III) demonstrated that CBF increased 38%. Noncerebral tissues known to be vascularly connected to the circle of Willis, and thus capable of receiving blood flow via the internal carotid artery, either did not change or increased so slightly during hypoxia that their effect on ICBF was minimal.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term results of local excision and radiotherapy in pleomorphic adenoma of the parotid.

Three hundred and eleven patients with primary pleomorphic salivary adenoma of the parotid gland seen between 1950 and 1971 are reviewed. All were managed by a combination of surgery, usually local excision, and irradiation. The minimum follow-up is 10 years. Recurrence rates at 0-5 years and 5-10 years were 1 and 1.5%, respectively, and all recurrences in this period were histologically or clinically benign. This recurrence rate is similar to those reported after superficial parotidectomy. After 10 years, however, the recurrence rate rose, becoming maximal at 15-20 years (4%) and yielding a cumulative risk of recurrence of 8.0% at 20 years. The late recurrences were predominantly malignant tumors. One tumor was probably radiation-induced; the remainder were compatible with spontaneous malignant transformation of benign pleomorphic adenoma, although radiation may have increased the incidence. In the absence of a comparable purely surgical series, this cannot be determined. The recommendation is made that the management of these tumors should be primarily surgical with irradiation reserved for patients presenting surgical difficulties. In addition, prolonged follow-up is necessary since there is a significant incidence of late recurrence and such recurrence may be more likely to be malignant regardless of the primary form of management.

An evaluation of fast neutron irradiation in the treatment of squamous cell carcinoma in cervical lymph nodes.

Analyses have been made of the response of metastatic cervical lymph nodes following neutron therapy, either as part of a randomized trial or in patients treated electively. In the trial patients, the overall regression and local control rates were similar after photons and neutrons. Mobile nodes, less than 3.0 cm, appeared to respond better to neutron therapy, and node masses greater than 3.0 cm had better control after photon therapy. The differences observed however were not statistically significant. There was a highly significant association between the control of the primary tumor and control of nodal disease. No survival advantage for neutrons was observed in association with apparently better control rates in cervical nodes.

Fast neutron therapy for squamous cell carcinoma in the head and neck region: results of a randomized trial.

A randomized trial of fast neuron therapy compared with 4MV photons for patients with head and neck cancer is reported. One hundred and sixty-eight patients were recruited between 1977 and 1984. The minimum follow-up is 2 years. Three patients were withdrawn before treatment began. Eighty-five were allocated to neutron therapy and 80 to receive photon therapy. All patients had squamous cell cancers in one of four primary sites: oral cavity, oropharynx, larynx, and hypopharynx. Local tumor control was similar in both groups: 44.7% after neutrons and 45.0% after photons. Salvage surgery was performed on 18 patients in each treatment group for residual or recurrent cancer. Acute radiation reactions of the mucous membranes were significantly more severe after photons. The number of patients with serious late reactions was greater after neutron therapy but the difference was not statistically significant. There were six deaths related to late morbidity after neutron therapy but none after photon therapy. Survival was better after photon therapy but the difference compared with the neutron group failed to reach statistical significance. When intercurrent deaths are excluded, the difference is less marked. Photon therapy was clearly better in terms of disease-free survival giving a 2-year local disease-free rate of 41.3% (s.e. 5.5%) compared with 29.4% (s.e. 4.9%) after neutrons.

Neutron therapy for malignant tumours of the salivary glands. A report of the Edinburgh experience.

A group of 28 patients with malignant tumours of the salivary glands have been treated by d(15) + Be neutron irradiation. Nineteen patients had inoperable cancers. Three had gross recurrent cancer and three had measurable residual cancer after surgery. Three patients were treated post-operatively for microscopic residual disease. Seven different histological types of tumour were included. Six out of 8 patients with adenoid cystic carcinomas have lasting local tumour control. 54.5% of the gross tumours were locally controlled. All three of those classified as microscopic residual disease have no evidence of local recurrence. 11/14 cancers given 16.0 Gy or more in 20 fractions in 4 weeks were controlled compared with only 1/8 given a lower dose. 12/19 cancers less than 10.0 cm maximum diameter were controlled. The radiation-related morbidity was similar to that observed after photon therapy.

Fast neutrons in the treatment of head and neck cancers: the results of a multi-centre randomly controlled trial.

The results are presented of a multi-centre randomly controlled trial of fast neutron irradiation and mega-voltage X-rays in the treatment of patients with locally advanced squamous cell carcinoma of the head and neck region. No significant difference was observed in local tumour control rates. Salvage surgery was performed in a similar number of patients in the two groups. Late morbidity was also similar in the two treatment groups. Patients in a subgroup with cancer of the larynx treated by photons had a significantly better survival than those in the neutron treated group.

A prototype gas exchange monitor for exercise stress testing aboard NASA Space Station.

A monitor was developed to track weightlessness deconditioning aboard the National Aeronautics and Space Administration (NASA) Space Station by measuring the O2 uptake (VO2) and CO2 production (VCO2) and calculating maximum VO2 and anaerobic threshold during an exercise stress test. The system uses two flowmeters in series to achieve a completely automatic flow calibration, and it uses breath-by-breath compensation for sample line transport delay. The accuracy of the system was measured over the range of VO2 and VCO2 from 100 to 800 ml/min by means of simulation. Accuracy was 0.54% for VO2 and 2.9% for VCO2. The system was further evaluated using two laboratory methods, the first method being comparison with a breath-by-breath system. As volunteers performed a maximum effort on a cycle ergometer, the mean difference in readings between the two systems was 17 ml/min for VO2 and 8.0 ml/min for VCO2. The correlation coefficient squared was greater than 0.96 for both. The second laboratory test was to use the system for 2 mo in a Human Performance Laboratory. Readings of maximum VO2 (VO2max) and anaerobic threshold were repeatable and consistent with the individual's activity level. The accuracy and convenience of operation will make this a valuable instrument aboard the Space Station.

Failure of pulmonary acidosis to increase respiratory drive.

Experiments were performed to determine whether increases in acidity isolated to the pulmonary circulation would stimulate hypothesized pulmonary chemoreceptors and increase respiratory drive in the anesthetized paralyzed mechanically ventilated cat (n = 9). Respiratory drive was assessed by measuring the frequency and amplitude of the integrated phrenic neurogram. To create an isolated pulmonary acidosis, blood returning to the lung was acidified by infusion of 0.3 M lactic acid (1.91 ml/min) into the inferior vena cava, while systemic arterial pH was restored to near normal levels by simultaneous infusion of base (0.3 M NaOH) into the left atrium. Six minutes after the start of this dual infusion of acid and base, right ventricular (pulmonary) pH decreased from 7.286 to 7.179 and PCO2 increased 7 Torr. Systemic arterial pH and PCO2 were unchanged from measurements immediately before the infusion. This level of pulmonary acidosis failed to increase respiratory drive as assessed by phrenic activity. To test the sensitivity of the preparation to known systemic arterial chemical stimuli, a combined pulmonary and systemic acidosis was elicited by infusion of 0.3 M lactic acid into the inferior vena cava and 0.3 M NaCl into the left atrium. This infusion significantly lowered both systemic arterial and pulmonary arterial pH (7.343 to 7.155 for systemic arterial pH and 7.286 to 7.067 for pulmonary pH) and increased phrenic efferent activity 45%. We conclude that phrenic efferent activity is unaffected by moderate reductions in the pH of the pulmonary circulation in the absence of a significant systemic arterial acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboxane A2 mimetic U-46619 induces systemic and pulmonary hypertension and delayed tachypnea in the goat.

Cardiorespiratory variables were measured continuously in five conscious goats before and after the infusion of U-46619 at a dose of either 2, 4, or 6 micrograms.kg-1.5 min-1. Infusion of U-46619 led to immediate increases in pulmonary arterial blood pressure (ABP) that were sustained for up to 15 min after the end of the infusion. Systemic ABP also increased, but the relative increase from control was less than the pulmonary pressor response. At the highest dose, U-46619 elicited a delayed tachypneic response that was greatest several minutes after the infusion was stopped. U-46619 was also infused simultaneously with sodium nitroprusside to clamp ABP pressure at baseline levels to determine whether stimulation of baroreceptors might contribute to the latency of the tachypneic response. Although sodium nitroprusside infusion prevented the increase in ABP, the increase in breathing frequency was still delayed 3-4 min from the start of the infusion. We conclude that U-46619 elicits pulmonary and systemic arterial hypertension in the conscious goat. At the higher dose U-46619 also elicits a delayed tachypnea that remains delayed even if ABP is normal.

Cardiorespiratory responses to HCl vs. lactic acid infusion.

Previous reports indicate that intravenous infusion of HCl can alter breathing and blood pressure even if reductions in systemic arterial pH are prevented. To extend these findings, as well as to determine whether other acids elicit comparable results, this report compares the cardiopulmonary response between right atrial infusion of lactic acid and HCl in awake ponies. Lactic acid, infused at a dose of 1.5 mmol/kg over 18 min, lowered systemic and pulmonary arterial pH 0.062 and 0.092 U, respectively, and increased pulmonary arterial pressure (delta Ppa, 4 mmHg), heart rate (HR, 4/min), and tidal volume (delta VT, 190 ml/m2). HCl, infused at a reduced dose of 0.5 mmol/kg over 18 min, lowered systemic and pulmonary arterial pH 0.024 and 0.047 U, respectively, but produced increases in Ppa (delta 23 mmHg), HR (delta 42/min), and VT (delta 321 ml/m2) that were significantly greater than from the larger dose of lactic acid. These results indicate that cardiopulmonary responses to infusion acidosis differ between the type of acid infused. It is suggested that, in the unanesthetized pony, HCl-induced infusion acidosis has a unique cardiopulmonary-stimulating action unrelated to the pH changes imparted to the circulating arterial blood and that this response is absent during the infusion of lactic acid.

Cardiorespiratory changes during HCl infusion unrelated to decreases in circulating blood pH.

To test the hypothesis that infusion of HCl changes blood pressure and respiration independent of decreases in circulating blood pH, an extracorporeal arteriovenous shunt (20 ml/min) between the femoral artery and vein was installed in anesthetized cats. Into this loop, acid (0.25 M HCl) and, approximately 10 cm downstream, base (0.25 M NaOH) could be infused simultaneously. Likewise, either acid or base could be infused individually. Right ventricular (Prv) and arterial (Pa) blood pressure, tidal volume (VT), and respiratory frequency (fresp) were recorded as well as blood gases and pH in arterial, right ventricular, and shunt loop blood at the reentrance into the animal. When HCl and NaOH were infused simultaneously and at equimolar rates (0.2 mmol/min for 10 min), there was a large increase in Prv, with little change or decrease in Pa. Respiratory frequency was increased, but total ventilation was not elevated because of a concomitant fall in VT. The rise in Prv and increase in fresp were transient in that they could only be evoked during the first HCl-NaOH infusion in a given animal. Repetitive infusions of HCl-NaOH into the same animal failed to elicit the response. Similar transient acid effects were evoked when HCl was infused without NaOH but not when NaOH was infused without HCl. During the second and third infusion of HCl, ventilatory responses were elicited that were explainable by stimulation of known chemoreceptors. The transient rise in Prv and fresp evoked by acid infusion might be explained by release of an agent from blood elements at the tip of the HCl infusion catheter, which in turn would constrict pulmonary vessels and influence breathing.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravenous acid infusion without lowering arterial pH stimulates breathing.

The aim of this study was to determine whether increases in ventilation would occur during intravenous acid infusion even if systemic arterial pH was held constant. In six awake ponies, HCl (500 ml, approximately 0.312 M) was infused into the right atrium at a total dose of 1.0 meq/kg over 18 min while an equivalent dose of NaOH was infused into the left heart to restore systemic arterial pH to normal. Total ventilation increased at the onset of the infusion and remained elevated although systemic arterial pH was normal to slightly alkaline. The increase in ventilation during the initial 2 min of the infusion coincided with an increase in pulmonary arterial PCO2 and decrease in pulmonary arterial pH. As the infusion progressed, however, pulmonary arterial pH and PCO2 returned to near control values due to the recirculation of systemic arterial blood with an acid-base status that had been altered consequent to the hyperventilation. Pulmonary arterial blood pressure was increased significantly during the entire infusion. Infusion of equivalent doses of hypertonic saline led to only minor alterations in the variables that were measured. These experiments demonstrate that this dose of intravenous HCl can increase ventilation independent of reductions in systemic arterial pH. Because increases in ventilation and pulmonary arterial H+ were not well correlated throughout the entire infusion, and pulmonary arterial blood pressure was increased, it is not clear if the mechanism for this ventilatory response is due to stimulation of pulmonary chemoreceptors, pulmonary vascular mechanoreceptors, or some other mechanism unrelated to increases in systemic arterial H+ concentration.

Stimulation of group III and IV afferent nerves from the hindlimb by thromboxane A2.

These experiments were designed to test the hypothesis that the TxA2 mimetic, U46,619, would stimulate group III and IV afferent nerve endings from the hindlimb of the anesthetized cat. Nerve impulses were recorded from the dorsal rootlets of the L7-S1 segments of the spinal cord, and afferent units identified by measurement of conduction velocities, mechanical probing of hindlimb muscles, and local injection of chemical stimulants (capsaicin and bradykinin). Five of the 15 group III fibers were stimulated by U46,619 (2-10 micrograms injected into the abdominal aorta; mean baseline impulse frequency increasing from 7.3 (+/- 3.2) impulses/s to 16.0 (+/- 3.1)), while 7 of the 12 group IV fibers responded to U46,619 (impulse frequency increasing from 4.3 (+/- 3.2) to 8.8 (+/- 3.6)). The average latency for the response (20-30 s) did not differ between the two groups of afferent fibers. We conclude that group III and IV afferent fibers originating from the skeletal muscle of the hindlimb are stimulated by TxA2 and that the release of TxA2 in skeletal muscle could evoke cardiorespiratory reflexes known to be activated by stimulation of these afferent nerves.

Applications of tensor theory to object recognition and orientation determination.

A method is developed by which images resulting from orthogonal projection of rigid planar-patch objects arbitrarily oriented in three-dimensional (3-D) space may be used to form systems of linear equations which are solved for the affine transform relating the images. The technique is applicable to complete images and to unlabeled feature sets derived from images, and with small modification may be used to transform images of unknown objects such that they represent images of those objects from a known orientation, for use in object identification. No knowledge of point correspondence between images is required. Theoretical development of the method and experimental results are presented. The method is shown to be computationally efficient, requiring O(N) multiplications and additions where, depending on the computation algorithm, N may equal the number of object or edge picture elements.

Cardiopulmonary effects of the combination of neuroleptic azaperone and hypnotic metomidate in swine.

Cardiopulmonary measurements were made at given intervals up to 120 minutes on 6 awake, unanesthetized pigs given azaperone and metomidate. Decreases from control values occurred in arterial blood pressure (deltaBPart = 30 mm of Hg), heart rate (deltaHR = 30 to 35 beats/minute), and cardiac index (deltaCI = 1.5 L/minute/m2). Blood gas and pH measurements indicated no severe impairment of pulmonary function or arterial acidosis. Although the drugs led to decreases in the various functions, cardiopulmonary function remained stable and uncompromised.

Cardiopulmonary effects of mechanical distension of the rumen in nonanesthetized sheep.

The cardiopulmonary effects of mechanical distension of the rumen were studied in nonanesthetized sheep. Results in group I ewes indicated that simply increasing intraruminal pressure by compressed air insufflation did not seriously affect cardiopulmonary hemodynamics. Changes were more serious in group II ewes when water injection was followed by ruminal insufflation with compressed air. Heart rate, total peripheral resistance, and total pulmonary resistance increased, with a concommitant increase in arterial and pulmonary blood pressure and decrease in stroke volume. Infusion of water alone increased heart rate and cardiac output. The blood gas data indicated a definite arterial hypoxemia and hypercapnia, suggesting impaired ventilation during ruminal distension. The increase in total pulmonary resistance was thought to be due to alveolar hypoxia caused by a significant decrease in ventilation.

Hypoxic pulmonary hypertension in the pony.

Hemodynamic measurements were made in 6 ponies at low altitude (Madison, WI, altitude, 250 m) and after 1, 2, 4, and 6 weeks at high altitude (Climax, CO, altitude, 3,400 m). The salient findings were that ponies maintain an increased heart rate and cardiac output and develop significant pulmonary hypertension at high altitude. The average control resting mean pulmonary artery pressure (BPpul) was 25.1 mm of Hg at 250 m; this value increased to 56.3 mm of Hg after 6 weeks at 3,400 m. An additional finding was that the pulmonary vascular response to acute hypoxia seemed to increase with time at high altitude.