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Biomedical subjects

D G Martin

Publications and source records attributed to D G Martin.

At least 19 recordsLinked to original sources
PubMed1992

Methemoglobinemia induced by a benzocaine-based topically administered anesthetic in eight sheep.

Benzocaine-based anesthetic sprays are commonly used in sheep to anesthetize the nasal passages and glottis before intubation. Sprays containing benzocaine have been identified as causing methemoglobinemia in dogs, cats, and human beings. Diagnosis of benzocaine-induced methemoglobinemia was made in 8 Dorset-Finn ewes exposed to a 2-second burst of (approx 56 to 112 mg of benzocaine) anesthetic spray. Venous blood samples taken 10 to 20 minutes after intranasal application of the spray revealed methemoglobinemia of 22.6 +/- 1.8% (mean +/- SD) in 9 samples from 8 ewes. Four other ewes intentionally exposed did not have methemoglobinemia. Topical use of benzocaine-containing anesthetics in sheep is not recommended. The high methemoglobin concentration induced by this product may substantially alter the cardiovascular and pulmonary function, blood gas analyses, and exercise capacity, thereby compromising animal health and/or research results. Although it appears that minimal clinical signs are induced in healthy animals, the risks of compromising a subclinically ill animal do not offset the benefits of this product.

Administration, Topical↗
PubMed1992

Topical anesthetic-induced methemoglobinemia in sheep: a comparison of benzocaine and lidocaine.

Benzocaine induces methemoglobin (MHb) in several species, whereas lidocaine may increase MHb in cats and human. Elevated MHb (greater than 20%) in sheep after benzocaine exposure was recently recognized. MHb decreases blood oxygen-carrying capacity which can complicate interpretation of experimental data. Sheep are used in research which requires tracheal intubation and blood gas analysis. Since benzocaine and lidocaine are used to provide local anesthesia prior to intubation, we compared MHb production by sheep after exposure to these drugs. A dose-response relationship between benzocaine and MHb was investigated. Eight crossbred Dorset ewes were dosed intranasally with benzocaine for 2 sec or with 40 mg of lidocaine in a randomized crossover design. Sheep with elevated MHb after the 2-sec benzocaine dose were later dosed with benzocaine intranasally for 10 sec. MHb levels were measured periodically on a CO-Oximeter. A quantitative MHb response to an indirect MHb former, p-aminopropiophenone (PAPP), by each sheep was determined 15 min after PAPP (0.6 mg/kg iv). MHb levels remained at baseline (1-2%) after lidocaine exposure in all sheep, as well as in four sheep (nonresponders) after the 2-sec benzocaine dose. Four sheep (responders) demonstrated 16.5-26.4% MHb after the 2-sec benzocaine dose. The responders formed 38.2-50.5% MHb after the 10-sec benzocaine dose. All responders developed high MHb after PAPP, while nonresponders developed slightly elevated MHb after PAPP. An N-hydroxy metabolite of benzocaine is the likely active MHb-forming substance. Benzocaine should be replaced by lidocaine when local anesthesia of the nasal or oropharyngeal region in sheep is required.

Administration, Topical↗
PubMed1991

An application of the non-linear bifurcation theory to tumor growth modeling.

The purpose of the work reported in this paper was to understand how a few cancerous cells (either from the primary growth, or as result of breaking away from a tumor and lodging in a different part of the body--metastasis) can grow to form a sizable mass and what decides whether such growth will indeed take place. The intermediate region, lying between the molecular (or micro) level to the fully developed (or macro) level, is not readily accessible to experimental observations. A mathematical model with a firm physiological basis has been proposed to develop a unified field theory that bridges the two regimes. The techniques of non-linear global analysis have been used. The global behavior, (which determines the long-term prognosis), is found to be significantly influenced by the presence or absence of two critical bifurcations. Both of these have practical consequences regarding the inception and the cure of the disease. Several conclusions have been drawn which lead to practical suggestions for experimentation. It is predicted that reducing the food intake immediately after an exposure to carcinogens, would lead to a reduced chance of cancer. A preliminary case has been made to lend support to the idea that an absence of snacking (and even periodic fasting) might work as a preventive measure against cancer.

Animals↗
PubMed1991

Day case laparoscopy: a survey of postoperative pain and an assessment of the value of diclofenac.

A randomised, controlled study was undertaken to assess the postoperative pain and side effects experienced by patients undergoing day case diagnostic laparoscopy and laparoscopic sterilisation, and to evaluate the effectiveness in these patients of peroperative diclofenac. Patients undergoing laparoscopic sterilisation had significantly higher pain scores at one hour postoperatively, and at discharge, than patients undergoing diagnostic laparoscopy (p less than 0.01) but there were no significant differences in pain scores 24 hours after discharge. The incidence of postoperative side effects following discharge from hospital was high, but there were no significant differences between the groups. Diclofenac had no significant effect in either group on the severity of postoperative pain, or the incidence of postoperative side effects.

Acetaminophen↗
PubMed1991

Effects of conditioning and maximal incremental exercise on oxygen consumption in sheep.

To assess the suitability of sheep for exercise studies, the effect of incremental exercise and conditioning on oxygen consumption (VO2) was studied. Six sheep were adapted to a treadmill and subsequently trained 8 weeks. The sheep were then studied, in random order, using 3 incremental exercise protocols (EX-1, EX-2, and EX-3). The protocols were chosen to approximate high (EX-1), moderate (EX-2), and low (EX-3) intensity exercise by varying treadmill speed and incline. The sheep were then conditioned for an additional 12 weeks and retested on the EX-2 protocol. During exercise, VO2, gas exchange ratio (R), and rectal temperatures (Tb) were recorded. All 3 protocols resulted in significant increases in VO2, R, and Tb (P less than 0.05). Maximum VO2 for EX-1, 49.9 +/- 5.0 ml/min/kg of body weight, was significantly greater than maximum VO2 for EX-2 and EX-3, 37.8 +/- 6.5 and 42.3 +/- 6.0 ml/min/kg, respectively (P less than 0.05), whereas maximum R and maximum Tb were similar. After the additional 12-week conditioning, time on the treadmill increased 40% from 9.58 +/- 0.87 to 13.4 +/- 0.44 minutes, and maximum VO2 increased 27% to 48.1 +/- 9.1 ml/min/kg. These data indicated that maximum VO2 varied with intensity of the exercise, 12 weeks of maximal exercise conditioning was sufficient to produce a measurable training effect (ie, increase endurance and maximum oxygen consumption) and sheep are suitable for maximal exercise studies where VO2 measurements are desired.

Animals↗
PubMed1991

Cardiopulmonary effects of a tiletamine-zolazepam combination in sheep.

To assess the effects on heart and lung function, a tiletamine-zolazepam (TZ) anesthetic combination was evaluated in 10 Dorset-type ewes. Ewes were randomly allotted to 2 equal groups. Ewes of groups 1 and 2 were given a single bolus of TZ (12 and 24 mg/kg of body weight, IV, respectively) at time zero. Hemodynamic, pulmonary, and ventilation variables were measured at 15-minute intervals to 120 minutes. Blood gas variables were evaluated at 5-minute intervals for the first 30 minutes, then at 15-minute intervals to 120 minutes. In all sheep, TZ administration induced rapid, smooth induction, with gradual and unremarkable recovery. Anesthesia duration was not significantly different between groups (mean +/- SD, 39 +/- 5 and 40 +/- 14 minutes for groups 1 and 2, respectively). Immediate drug effects included apnea, decreased mean arterial blood pressure, and arterial hypoxemia. Cardiac output was significantly decreased in both groups at all times after drug administration. Significant changes in group-1 ewes included increased pulmonary and systemic vascular resistances and decreased inspired minute ventilation, tidal volume, and respiratory airflow. Significant changes in group-2 ewes included increased systemic vascular resistance and decreased pulmonary arterial pressure, inspired minute ventilation, and respiratory airflow. Both drug dosages induced apneustic breathing patterns and caused significant changes in arterial and venous blood hemoglobin concentrations and PCV. Tiletamine-zolazepam is useful for intermediate-duration anesthesia in sheep.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1989

Resistance to airflow in anaesthetic breathing systems.

We have examined, under reproducible conditions, the resistance to airflow of complete anaesthetic breathing systems (Magill, Coaxial Lack, Parallel Lack and Bain systems) and components of these systems. All systems had resistances within the recommended ranges at all flows likely to be experienced in normal clinical practice. The Magill system had the lowest resistance under all conditions. It is concluded that comparisons should be made only between complete breathing systems.

Airway Resistance↗
PubMed1988

Causes of financial difficulty in Catholic hospitals.

A study was conducted to see which attributes contribute most to financial distress in Catholic hospitals. The 1982 total population of U.S. Catholic hospitals was examined. The reason for financial distress was found to be more related to management attributes than to financial variables.

Bed Occupancy↗
PubMed1987

Factors associated with low birthweight in an inner-city population: the role of financial problems.

A case-control study of low birthweight among residents of high risk areas of Alameda County was conducted in 1983. The relation of 13 variables to low birthweight was assessed using a multiple logistic regression analysis. A six-fold increase in the risk of low birthweight was found in association with financial problems during the current pregnancy, controlling for differences in race, certain poor health habits, complications of pregnancy, and several other factors between cases and controls.

Female↗
PubMed1987

Lateralizing brain damage with the Luria-Nebraska Neuropsychological Battery: diagnostic effectiveness as compared to the Halstead-Reitan Neuropsychological Test Battery.

This investigation examined the ability of the Luria-Nebraska Neuropsychological Battery (LNNB) to lateralize brain damage, since substantial statistical and methodological issues have been raised regarding the initial LNNB lateralization validation study. A comparison was then made of the ability of the LNNB and the Halstead-Reitan Neuropsychological Test Battery to lateralize brain damage. Both neuropsychological batteries were administered to 30 predominantly left- or right-hemisphere-damaged subjects (15 in each group) with discriminant analysis classification procedures demonstrating similar, above chance, accuracy in lateralizing cerebral dysfunction. Cross-validation of objective clinical rules designed to aid in LNNB test interpretation resulted in classification of brain damage and lateralization at levels below reported values from the test developer's laboratory. The limited role such simplistic rules have in assessment is discussed, as is the need to evaluate dimensions of test usefulness other than those related to gross diagnostic decisions (e.g., presence or laterality of brain damage) in determining the instrument of choice for clinical neuropsychological practice. More research is recommended to fully define the limits of the clinical utility of the LNNB.

Brain↗
PubMed1986

Plasma viscosity elevations with simulated weightlessness.

Bed rest studies which simulate weightlessness have demonstrated marked changes in the state of hydration of subjects as well as decrements in aerobic capacity. These two phenomena may be linked through increases in blood viscosity which is altered by a loss of free water and which, in turn, influences blood flow needed for aerobic muscular work. This study examines changes in the rheologic properties of blood which attend changes in plasma volume with bed rest in humans and correlates these changes with alterations in aerobic capacity. Eight healthy human subjects were studied on the 6th day of bed rest during two consecutive 10-d bed rest periods separated by a 14-d recovery interval designed to simulate the flight-layover schedule of shuttle astronauts. Plasma viscosity was measured with a Wells-Brookfield viscometer, plasma volume by dye dilution, and maximal aerobic capacity (VO2max) by recumbent cycle ergometry. Bed rest resulted in significant increases in hematocrit and in total plasma protein concentration and fibrinogen concentration, both of which contribute to an elevation in plasma viscosity. The greater than 20% increase in fibrinogen concentration was much greater than could be explained by hemoconcentration. VO2max decreased significantly in the first but not the second bed rest cycle. In many individuals, a decrease in plasma volume and aerobic capacity was coupled with elevated plasma viscosity and hematocrit; however, significant correlations between these variables were lacking. Although significant rheologic perturbations do occur with bed rest, in this study, blood viscosity elevation failed to directly correlate with the reduction in VO2max.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Blood viscosity responses to maximal exercise in endurance-trained and sedentary female subjects.

To assess whether the rheological properties of blood might be altered by exercise, we measured whole blood viscosity, plasma viscosity, and its components in healthy female subjects before, immediately after, and 1 h after maximal upright exercise using the Bruce graded exercise protocol. Forty-seven female subjects (15 sedentary, 14 who ran 5-15 miles/wk, and 18 who ran greater than 50 miles/wk), ages 18-43 yr, were evaluated. Whole blood viscosity, measured with a cone and plate viscometer, increased an average of 12.6% with exercise. The increase was greater than can be attributed to the observed 8.9% increase in hematocrit alone due to a coincident increase in plasma protein concentration. However, plasma viscosity did not rise to the degree expected, likely due to a disproportionate observed loss of fibrinogen from the protein pool. These changes were independent of conditioning level or aerobic capacity. In this cross-sectional study, there appears to be no adaptive adjustment in females to physical conditioning that results in changes in blood viscosity.

Adult↗
PubMed1985

CC-1065 transformations.

This report defines the transformations that antitumor antibiotic CC-1065 underwent under basic and acidic conditions. The isolation, purification, characterization, and biological properties of a cyclopropapyrroloindole fragment, and an acidic fragment, PDE-I dimer, from a mild alkaline fragmentation and the phenolic product, AAP, resulting from alkylation of acetic acid by the cyclopropyl function are described.

Antibiotics, Antineoplastic↗
PubMed1985

Evaluation of the zetacrit and zeta sedimentation ratio in dogs.

The Wintrobe erythrocyte sedimentation rate (ESR) has been used in animals and persons as a screening test for inflammatory disease and as a monitor for disease progression in individuals. Now, the zetacrit (ZC) and zeta sedimentation ratio (ZSR) are suggested as suitable rapid laboratory tests to replace the ESR in dogs. In 65 dogs, a strong inverse correlation between ESR and ZC was observed (r = -0.961, P less than 0.05). Significant correlations of similar magnitude between ZC and hematocrit (r = 0.587, P less than 0.05) and ESR and Hct (r = 0.569, P less than 0.05) were observed. In addition, influences of various protein fractions, such as fibrinogen, globulin, and albumin, on the ESR and ZC were evaluated and found to be of similar magnitude. These data indicate that ESR and ZC are equivalent methods for determining erythrocyte sedimentation rates in dogs. A strong correlation (r = 0.900, P less than 0.05) between Wintrobe ESR, adjusted for the effect of Hct (ESRHct), and ZSR was observed. The influence of plasma proteins on ESRHct and ZSR was of similar magnitude. However, a weak yet significant correlation between ESRHct and the microhematocrit remained (r = 0.291, P less than 0.05). Data indicate that the latter more effectively factors out the influence of Hct on sedimentation.

Animals↗