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Biomedical subjects

S E Curtis

Publications and source records attributed to S E Curtis.

At least 55 records · Page 3Linked to original sources
PubMed1993

Accuracy of three pulse oximeters during exercise and hypoxemia in patients with cystic fibrosis.

To evaluate the reliability of noninvasive oximeters during exercise in patients with cystic fibrosis (CF), we studied 9 patients during exercise tests, using 3 devices (Hewlett-Packard 47201A, Biox-Ohmeda 3700, Nellcor 100), comparing oximetry readings with arterial blood co-oximetry. Fifty samples from preexercise, exercise, and recovery were collected; and paired measurements were analyzed for bias (arterial blood gas SaO2--noninvasive SaO2) and precision (1 SD of the bias). Values were available for the Hewlett-Packard and the Biox-Ohmeda at all 50 collection times. The Nellcor failed to read on four occasions, all during exercise. The accuracy of the Biox-Ohmeda readings was significantly worse during exercise than rest, while the Nellcor and the Hewlett-Packard performance did not differ significantly between exercise and rest. During hypoxemia (SaO2 < 90 percent as determined by co-oximetry on arterial blood), the Biox-Ohmeda and Nellcor consistently overestimated saturation, with mean bias of -6.1 percent and -3.0 percent, respectively. The Hewlett-Packard was more reliable and valid during hypoxemia, with a mean bias of -1.0 percent. The Nellcor read significantly more accurately in the six patients with severe digital clubbing than in the three patients with mild digital clubbing. It is important to be aware of possible limitations of noninvasive oximeters before accepting them as accurate.

Adolescent↗
PubMed1992

Whole body and regional O2 uptake/delivery and lactate flux in endotoxic dogs.

We infused endotoxin into anesthetized dogs while maintaining cardiac output. Whole body O2 uptake and arterial lactate concentration were measured at the same time with regional O2 uptake and lactate fluxes in muscle and gut. Even though whole body O2 uptake increased, so did arterial lactate levels. The different behavior of organ systems was marked by the fact that muscle took up lactate while its O2 uptake didn't change whereas gut produced lactate as it decreased its O2 uptake. Comparison with critical levels of O2 delivery and O2 extraction ratio for whole body and the two regions opened considerable doubt that generalized and significant hypoxia explained the rise in arterial lactate. Addition of mild hypoxic hypoxia also neither caused O2 uptake to fall nor lactate to rise which reinforced our conclusion that there was little or no tissue hypoxia in endotoxin treated animals given adequate resuscitation with red blood cells and colloid solutions.

Animals↗
PubMed1992

Systemic and regional O2 delivery and uptake in bled dogs given hypertonic saline, whole blood, or dextran.

The mechanisms by which small volumes of hypertonic saline in dextran (HSD) resuscitate bled dogs are incompletely understood but may include a pulmonary osmolar reflex. A known negative effect of HSD is hemodilution that reduces O2-carrying capacity. Our goals in this study were to ascertain whether the putative osmotic reflex redistributed blood flow between muscle and gut and whether O2 delivery (DO2) was adequate at systemic and regional levels. Left hindlimb muscle and a segment of ileum were vascularly isolated in three groups (n = 8) of anesthetized dogs that were then bled to mean arterial pressure (MAP) of 40 mmHg for 30 min. At that point, all shed blood (approximately 40 ml/kg) was returned in the blood group (BLD); 20 ml/kg of Dextran 70 was given to the dextran group (DEX); and 5 ml/kg of 7.5% NaCl in dextran was given to the HSD group. MAP and cardiac output were restored to acceptable levels in all but was poorly maintained in HSD. The fall in hematocrit (41 to 25%) in HSD was matched by that in DEX (42 to 22%), so that DO2 only reached approximately 55% of that in BLD. Nevertheless, systemic and regional O2 uptakes were similar; O2 debt and repayment did not differ; and lactate metabolism was alike in all groups. O2 extraction did have to increase to near maximum in HSD, however. Other than a transient increase to muscle, HSD had no special effect on distribution of cardiac output. HSD was efficacious as a short-term resuscitative measure but did encroach markedly on O2 transport reserves.

Animals↗
PubMed1992

Regional and systemic oxygen delivery/uptake relations and lactate flux in hyperdynamic, endotoxin-treated dogs.

Pathologic oxygen supply dependency (PO2SD) may be etiologic in multisystem organ failure (MSOF) and has been related to mortality in sepsis. Although elevated lactate levels are generally assumed to be a marker of anaerobiosis in these patients, endotoxin may increase serum lactate by inactivation of pyruvate dehydrogenase (PDH), unrelated to tissue PO2. We hypothesized that regional lactate flux may correlate poorly with local oxygen delivery in sepsis. This study examined both the whole-body (WB) and regional (isolated hind limb L and gut G) responses to endotoxin infusion in terms of oxygen delivery, oxygen uptake, and lactate flux in 12 pentobarbital-anesthetized dogs. To separate hypoxia-induced lactate production from that related to inactivation of PDH by endotoxin, half the dogs received dichloroacetate (DCA), a PDH activator. After endotoxin and volume resuscitation, each animal had low systemic vascular resistance with normal to high cardiac output. Despite adequate oxygen delivery to WB, L, and G, arterial lactate levels rose significantly. A 30-min hypoxic challenge (12% FIO2) did not increase lactate levels but did increase WB O2 uptake. DCA normalized lactate levels without influencing oxygen delivery and uptake relations. These data show that lactate levels in endotoxic states may be a poor marker of tissue hypoxia and may be more related to PDH activity.

Acidosis, Lactic↗
PubMed1992

Systemic and regional oxygen uptake and lactate flux in endotoxic dogs resuscitated with dextran and dopexamine or dextran alone.

We examined how volume resuscitation with and without dopexamine, a potent beta 2-adrenergic and dopaminergic agonist, would affect O2 uptake (VO2), O2 delivery (DO2), and lactate metabolism in whole body, skeletal muscle, and gut of 18 anesthetized dogs after they were infused for 1 hr with 2 mg/kg endotoxin. Six dogs were then infused with dextran for 2 hr at 0.5 ml/kg/min (DEX); another six were given the same volume with 12 micrograms/kg/min dopexamine (DPX); and a third group received no treatment (NT). After endotoxin, all animals were hypotensive; cardiac output decreased 30%; and DO2 to whole body, skeletal muscle, and gut were at or below critical for VO2. DO2 was raised above critical in whole body and gut of DEX and DPX but not in muscle of DPX, which produced lactate. Whole body DO2 approached preendotoxin level by 2 hr in DEX and DPX but stayed near critical in NT. At that time, gut VO2 was higher in DPX than in DEX or NT, and lactate efflux became less than in DEX. Vascular reactivity was present in the gut at the end of the experiment in six of six DPX studies, in four of six DEX studies, and in none of the NT studies. These results suggest that resuscitation with dopexamine + dextran after induction of endotoxic shock may be more beneficial than dextran alone, particularly for the gut mucosa.

Animals↗
PubMed1991

Cardiac output during liquid (perfluorocarbon) breathing in newborn piglets.

BACKGROUND AND METHODS: Liquid ventilation using perfluorocarbons is a new technique for ventilation of infants with restrictive lung disease. However, this method of ventilation has been shown to impair cardiac output (Qt) in several animal species, casting doubt as to its feasibility. This study tested whether Qt could be maintained during liquid breathing by intravascular volume expansion. Seven piglets were carefully hydrated, instrumented for continuous Qt measurement, and subjected to 2 hr of liquid breathing. PaCO2 was maintained at 40 to 50 torr (5.3 to 6.7 kPa), and PaO2 greater than 80 torr (greater than 10.7 kPa). Additional colloid was given during liquid breathing if Qt decreased to less than 90% of preliquid breathing values. RESULTS: Four piglets maintained Qt throughout the liquid breathing trial with maintenance fluids only. Three piglets each required one 10 mL/kg fluid bolus for Qt 82% to 89% of the baseline value, after which Qt rapidly increased to greater than 90% of baseline. Oxygen consumption and serum lactate levels remained normal throughout liquid breathing. CONCLUSION: Qt is readily maintained during liquid breathing in properly hydrated animals.

Animals↗
PubMed1991

Experimental models of pathologic oxygen supply dependency.

Pathologic oxygen supply dependency is an abnormal situation in which oxygen uptake (Vo2) varies directly with oxygen delivery. Its presence in patients with adult respiratory distress syndrome and/or sepsis has been associated with particularly high mortality rates that may be the result of tissue hypoxia that causes multiple organ failure. The evidence for this association has been indirect because we cannot use invasive methods that would be necessary to verify or disprove the hypothesis. Because further progress will depend on the development of adequate animal models of pathologic oxygen supply dependency, we have attempted to evaluate some of the available information in this area as well as the likelihood that tissue hypoxia will prove to be the precipitating factor. In anesthetized dogs injected or infused with endotoxin, many of the features of pathologic oxygen supply dependency have been successfully produced. These features include defective peripheral oxygen extraction, increased oxygen demand, and increased lactate levels. Regional measurements have shown that gut Vo2 decreases before other areas, particularly skeletal muscle. Lactate measurements alone were shown not to be sufficient proof of tissue hypoxia. More direct measurements of actual energy states and tissue Po2 are indicated for future research efforts.

Animals↗
PubMed1991

Systemic and regional oxygen uptake and delivery and lactate flux in endotoxic dogs infused with dopexamine.

OBJECTIVE: To test whether dopexamine, a dopaminergic and beta 2-adrenergic receptor agonist, would: a) direct a greater share of cardiac output to gut than to muscle when used to increase systemic oxygen delivery (DO2) in endotoxic dogs; and b) enhance the ability of peripheral tissues to extract oxygen. DESIGN: Two groups of eight dogs infused for 1 hr with 2 mg/kg Escherichia coli endotoxin. One group was continually infused with dopexamine (12 micrograms/min.kg) and the other group was not (control group). After 2 hrs, oxygen extracting ability was challenged by changing inspired gas to 12% oxygen for 30 mins. SUBJECTS: Anesthetized, paralyzed, pump-ventilated mongrel dogs. INTERVENTIONS: Donor RBCs and dextran used during endotoxin infusion to maintain cardiac output while preserving hematocrit near 40%. MEASUREMENTS AND MAIN RESULTS: In the dopexamine-treated group, cardiac output, systemic DO2, and oxygen consumption (VO2) were higher than in the control group during the first 90 mins, but were not thereafter. Gut and muscle blood flow did not differ between groups, but the fraction of cardiac output going to each region tended to be less in the dopexamine-treated dogs. Arterial lactate values increased to about 6 mmol/L in all dogs. In both groups, limb muscle first produced lactate but then took up lactate after the first hour. The gut in controls converted from lactate uptake in the first hour to producing about 20 mumol/min.100 g, whereas the gut never produced lactate in the dopexamine-treated group. During hypoxia, systemic DO2 and VO2 decreased only in the dopexamine-treated group, even though oxygen extraction was only slightly above 40%. Oxygen extraction was not demonstrably improved by dopexamine treatment. CONCLUSIONS: Dopexamine temporarily increased systemic DO2 and VO2 in volume-expanded endotoxic dogs during normoxia and may have caused gut mucosa to be preferentially perfused and thus to be kept better oxygenated.

Animals↗
PubMed1991

Characterization of the IS895 family of insertion sequences from the cyanobacterium Anabaena sp. strain PCC 7120.

A family of repetitive elements from the cyanobacterium Anabaena sp. strain PCC 7120 was identified through the proximity of one element to the psbAI gene. Four members of this seven-member family were isolated and shown to have structures characteristic of bacterial insertion sequences. Each element is approximately 1,200 bp in length, is delimited by a 30-bp inverted repeat, and contains two open reading frames in tandem on the same DNA strand. The four copies differ from each other by small insertions or deletions, some of which alter the open reading frames. By using a system designed to trap insertion elements, one of the elements, denoted IS895, was shown to be mobile. The target site was not duplicated upon insertion of the element. Two other filamentous cyanobacterial strains were also found to contain sequences homologous to IS895.

Amino Acid Sequence↗
PubMed1991

Stroma-free hemoglobin: its presence in plasma does not improve oxygen supply to the resting hindlimb vascular bed of hemodiluted dogs.

In hemodilution, red cell spacing in the microcirculation is increased, flow distribution may become more heterogeneous, and, as a result, oxygen supply to tissues may suffer. We tested the hypothesis that oxygen extraction from diluted blood may be enhanced by the presence of hemoglobin in the plasma phase in relatively low concentrations. In anesthetized dogs, the hindlimb vascular bed was isolated and perfused with the animal's own blood by a roller pump. One group of dogs (n = 6) was hemodiluted (hematocrit = 15.0 +/- 1.0%) with a 6% solution of dextran. A second group of dogs (n = 6) was similarly hemodiluted (hematocrit = 16.0 +/- 0.4%) with dextran containing stroma-free hemoglobin solution whereby plasma-phase hemoglobin concentration was raised to 1.1 +/- 0.1 g.dL-1. Systemic hemodynamic observations were made repeatedly over the subsequent 2.5 h, while blood flow to the hindlimb was progressively reduced in stepwise decrements. The hemoglobin-hemodiluted group showed increased systemic arterial blood pressure and total peripheral resistance when compared with the control (dextran diluted) group. The isolated hindlimb also showed evidence of increased vascular resistance in the hemoglobin-treated group. In each individual animal, critical oxygen delivery and extraction were determined by finding the intercept of the supply-independent and supply-dependent portions of the oxygen uptake/oxygen delivery relationship. Neither the critical oxygen delivery rates (5.75 +/- 0.83 vs. 6.41 +/- 0.53 mL.kg-1.min-1) nor critical oxygen extraction ratios (0.75 +/- 0.03 vs. 0.76 +/- 0.04) were found to be significantly different in the two groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The importance of animal cognition in agricultural animal production systems: an overview.

To describe and then fulfill agricultural animals' needs, we must learn more about their fundamental psychological and behavioral processes. How does this animal feel? Is that animal suffering? Will we ever be able to know these things? Scientists specializing in animal cognition say that there are numerous problems but that they can be overcome. Recognition by scientists of the notion of animal awareness has been increasing in recent years, because of the work of Griffin and others. Feeling, thinking, remembering, and imagining are cognitive processes that are factors in the economic and humane production of agricultural animals. It has been observed that the animal welfare debate depends on two controversial questions: Do animals have subjective feelings? If they do, can we find indicators that reveal them? Here, indirect behavioral analysis approaches must be taken. Moreover, the linear additivity of several stressor effects on a variety of animal traits suggests that some single phenomenon is acting as a "clearinghouse" for many or all of the stresses acting on an animal at any given time, and this phenomenon might be psychological stress. Specific situations animals may encounter in agricultural production settings are discussed with respect to the animals' subjective feelings.

Agriculture↗
PubMed1991

Effects on chick performance of ammonia and heat stressors in various combination sequences.

The purpose of the present study was to evaluate the effects of previous experience with a stressor on chicks' subsequent performance when exposed later to the same stressor or to a different stressor. Performance was measured in chicks exposed to aerial ammonia, environmental heat, or both in reciprocal sequences in two consecutive periods. Four (2 x 2 factorial) treatment combinations of ammonia [0 ppm (a) or 125 ppm (A)] and heat [30 C (h) or 36.5 C (H]) stressors were imposed in each of two consecutive 4-day periods, giving a total of 16 treatments. Weight gain (G), feed intake (F), and the gain:feed ratio (G:F) in Periods 1 (Days 9 to 13 posthatch) and 2 (Days 13 to 17 posthatch) were analyzed. Stressors decreased performance in both periods, but the effect was greater in Period 2. Synergism between A and H in Period 2 decreased chicks' G, F, and G:F in Period 2. Stress-depressed productive traits in Period 1 were succeeded in Period 2 not by residual negative effects but by compensatory responses: prior exposure to stressors in Period 1 was not detrimental to the chicks' subsequent G or G:F in Period 2. For example, chicks switched from Treatment ah in Period 1 to AH in Period 2 had lower G in Period 2 than did those going from either Ah, aH, or AH in Period 1 to AH in period 2. It was concluded that exposure to stressors early on enhanced the chicks' ability to cope with the same or with different stressors later and that compensatory responses occurred as the result of short-term exposure to stressors.

Ammonia↗
PubMed1990

Characterization of a four-member psbA gene family from the cyanobacterium Anabaena PCC 7120.

The cyanobacterium Anabaena PCC 7120 contains a multigene family that encodes the D1 polypeptide of Photosystem II. This family consists of four members denoted psbAI-IV that are each unique but highly homologous. psbAII, III and IV are more closely related to each other than to psbAI. These three copies encode identical polypeptides that differ from the psbAI product by 21 amino acids. The transcription initiation site for psbAI has been mapped to 64-65 nucleotides upstream from the coding region. Primer extension assays performed with an oligonucleotide specific for psbAII, III and IV transcripts suggest that one or more of these genes is also expressed. Genomic mapping and chromosome walking experiments demonstrate that none of the four psbA copies is within 20 kbp of another member of the gene family.

Amino Acid Sequence↗
PubMed1990

Behavioral and endocrine responses of sows to prostaglandin F2 alpha and cloprostenol.

Behavioral and endocrine changes in the sow following injection with prostaglandin F2 alpha (PGF2 alpha) or its analogue, cloprostenol (CLO), were monitored to identify endocrine correlates of prepartum activity (nest-building). On Day 112 postcoitum, within 15 min after injection with 10 mg PGF2 alpha, sows offered straw in pens engaged in intense prepartum activity, but few behavioral changes occurred during the first 2 h following administration of 175 micrograms CLO. The temporal pattern of prepartum activity, however, was affected by both prostaglandins. In control sows, most prepartum activity came during Hours 16-0 before delivery of first piglet (delivery). After CLO, sows engaged in nest-building more during Hours 32-17 and less during Hours 16-0. In another experiment, sows in farrowing crates were injected with saline, 175 micrograms CLO, or 10 mg PGF2 alpha on Day 112 and blood was collected 0, 15, 30, 60, and 90 min later. Another sample was collected when spontaneous prepartum activity was first observed. For approximately 90 min after PGF2 alpha treatment, sows rooted, pawed, and bit and rubbed faces on crate bars; after saline and CLO, this behavior was rarely observed. After prostaglandin treatment, plasma progesterone tended to decline, a 10-fold rise in relaxin came within 15 min, but estrone did not change. Plasma prolactin rose 10-fold within 30 min after PGF2 alpha treatment, and rose more gradually after CLO treatment. When sows exhibited spontaneous prepartum activity (approximately 7 h before delivery), endocrine status was characterized by low progesterone, high estrone:progesterone ratio, and high prolactin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Isolation and sequence analysis of a beta-tubulin gene from Aspergillus flavus and its use as a selectable marker.

An altered beta-tubulin gene that confers resistance to benomyl [whose active ingredient is 2-(methoxycarbonylamino)benzimidazole (MBC)] was isolated from a DNA library of Aspergillus flavus and used as a selectable marker for transformation. The beta-tubulin gene was cloned into a plasmid vector containing the pyr-4 gene of Neurospora crassa, and transformants were selected either for uracil prototrophy or MBC resistance. Transformants selected for uracil prototrophy were of three phenotypic classes: sensitive, intermediate, and resistant to MBC. Transforming DNA appeared to integrate at several sites in the genome, with the more resistant phenotypes having more copies of the altered beta-tubulin gene than the sensitive and intermediate phenotypes. Transformants were also selected on medium containing MBC. The average frequency of transformation (1 to 3 transformants per micrograms of transforming DNA) was lower than that obtained by selection for uracil prototrophy, presumably because of failure to select transformants that contained few copies of the altered beta-tubulin gene. The sequence of the beta-tubulin gene was determined and compared with the published sequence of the benA gene of A. nidulans; the beta-tubulin gene was found to be highly conserved between the two Aspergillus species. Notable differences were that the beta-tubulin gene of A. flavus lacks intron 6 present in benA and has an additional leucine at position 148. This is the first gene sequence reported from an aflatoxin-producing fungus and adds to the growing body of knowledge of the beta-tubulin genes and their use as selectable markers for transformation of filamentous fungi.

Amino Acid Sequence↗