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Biomedical subjects

D Allen

Publications and source records attributed to D Allen.

At least 73 records · Page 4Linked to original sources
PubMed1990

Effect of endotoxin administration on equine digital hemodynamics and starling forces.

Using a pump-perfused extracorporeal isolated digital preparation, the effects of a 30-minute infusion of either saline solution (control) or endotoxin on equine digital hemodynamics and microvascular function were determined. Digital blood flow and arterial, venous, and capillary pressures were recorded at 15-minute intervals for 150 minutes. From these data, total vascular resistance and pre- and postcapillary resistances were calculated. Isogravimetric capillary filtration coefficient, vascular compliance, and the osmotic reflection coefficient were determined after the last hemodynamic measurements were taken. Changes in hemodynamic values of control equine digits were not observed. During the 120 minutes after infusion of endotoxin, digital blood flow decreased 43%, and total vascular resistance increased 89%. Precapillary resistance increased 122%, but postcapillary resistance did not change significantly. Changes in vascular compliance or the capillary filtration coefficient were not observed in response to either treatment. The osmotic reflection coefficient, an index of permeability, did not differ significantly between digits of the endotoxin-treated and control groups. These data indicate that the increase in vascular resistance during endotoxemia may have been attributable to arterial/arteriolar constriction and that neither the permeability nor the surface area of the exchange vasculature within the digit was significantly affected by endotoxin. Although marked alterations in vascular function are seen after administration of endotoxin, these changes do not parallel those documented in association with experimentally induced laminitis.

Animals↗
PubMed1990

Hemodynamic responses of the equine digit to intravenous and digital arterial infusion of dopamine.

In 6 adult horses anesthetized with pentobarbital, the hemodynamic responses of the equine digit to infusion of dopamine were evaluated by use of an isolated extra corporeal pump perfused digital preparation. Digital blood flow was maintained at a constant rate that was independent of systemic hemodynamic changes. Three sequential experiments were performed on each horse. In the first experiment (n = 6), dopamine was infused IV at rates of 1.0, 2.5, and 5.0 micrograms/kg/min. For the second experiment (n = 5), dopamine (400 micrograms/ml) was infused into the digital artery at the rates of 0.07, 0.7, and 1.2 ml/min. The third experiment (n = 5) consisted of a 5-minute intra-arterial infusion of phentolamine followed by the intra-arterial infusion of dopamine while continuing the infusion of phentolamine. Digital venous, arterial, and capillary pressures, total digital vascular resistance, and precapillary to postcapillary resistance ratios were determined in each experiment. Systemic infusion of dopamine did not induce changes in the hemodynamics of the digital vasculature. Digital arterial infusion of dopamine alone resulted in a dose-dependent increase in arterial pressure, total digital vascular resistance, and an increase in the precapillary to postcapillary resistance ratio. Phentolamine attenuated the vasoconstrictive response elicited by intra-arterial infusion of dopamine.

Animals↗
PubMed1989

The interaction between Cu(I) superoxide dismutase and hydrogen peroxide.

The interaction between superoxide dismutase (SOD) and peroxide, under anaerobic conditions in the presence of an OH radical scavenger, formate, and an indicator, nitro blue tetrazolium, involves five reactions and an equilibrium: (table; see text) Reaction 3 occurs at a rate that is proportional to both peroxide and enzyme with no kinetic evidence for any intermediate peroxide-enzyme complex. Rate studies as a function of pH corroborate previously published work (Fuchs, H. J. R., and Borders, C. L., Jr. (1983) Biochem Biophys. Res. Commun. 116, 1107-1113; Blech, D. M., and Borders, C. L., Jr. (1983) Arch. Biochem. Biophys. 224, 579-586) suggesting that HO2-, and not H2O2, is the active species in this system: k(HO2- + superoxide dismutase-Cu+) = 2.6 x 10(3) M-1 s-1. Evidence is presented which suggests that HO2-, like O2-, reacts at rates that are affected by the electrostatic forces of the enzyme.

Hydrogen Peroxide↗
PubMed1989

Breeding soundness of beef bulls after circumcision: 33 cases (1980-1986).

Case records of 33 beef bulls that had preputial prolapses and underwent circumcisions were reviewed. Data retrieved included age, breed, duration of preoperative medical treatment, complications of surgery, length of time from surgery to first breeding, ability of bull to copulate, duration of active breeding, and complications resulting in breeding unsoundness. The mean age of all bulls was 3.5 years (1 to 7 years). Breeds represented included Santa Gertrudis (n = 13), Beefmaster (n = 8), Brangus (n = 7), Brahman (n = 4), and Angus (n = 1). The mean duration of medical treatment before surgery for all bulls was 16.4 days (2 to 38 days). There was no statistically significant difference between the mean duration of medical treatment before surgery between bulls that became breeding sound (16 days), compared with those that were breeding unsound (19 days). However, bulls requiring more than 14 days of medical treatment before surgery were approximately 3 times (relative risk, 2.8) more likely to develop postoperative complications than those bulls requiring 14 days of treatment or less. Eleven bulls (33%) developed one or more postoperative complications. The complications resolved in 4 bulls, but 7 were never able to breed. Of these 7 bulls, 4 had problems directly related to the circumcision, 2 had extensive fibrosis of the prepuce already present at surgery, and 1 was discharged from the hospital with no apparent complications but was never able to breed. Twenty-five of the 33 bulls (76%) were breeding sound for 1 or more years after surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Outpatient treatment of 'crack' cocaine smoking with flupenthixol decanoate. A preliminary report.

"Crack" cocaine abuse often produces severe cocaine dependence that is refractory to available pharmacological and outpatient psychotherapeutic treatments. We conducted two preliminary investigations evaluating the efficacy of flupenthixol decanoate, a depot xanthene requiring infrequent intramuscular administration, in the treatment of cocaine withdrawal. Ten outpatient crack cocaine smokers with poor prognoses were administered flupenthixol decanoate in an open-label, open-ended trial. Flupenthixol decanoate was well tolerated and appeared to decrease cocaine craving and use markedly and rapidly, producing a 260% increase in the average time retained in treatment among these subjects. These promising but preliminary data, combined with the magnitude of problems presented by crack, warrant rapid, expanded double-blind assessment of flupenthixol decanoate in cocaine-abuse treatment.

Adult↗
PubMed1989

Non-random migration of CD4 and CD8 T cells: changes in the CD4: CD8 ratio and interleukin 2 responsiveness of efferent lymph cells following in vivo antigen challenge.

In this investigation we have examined some of the cellular and molecular changes in efferent lymph that drains from an antigen-stimulated peripheral lymph node. Resting efferent lymph is characterized by a higher percentage of CD4+ cells and consequently, a higher CD4/CD8 ratio than peripheral blood. Following antigen stimulation of a cannulated peripheral lymph node in antigen-primed sheep, the percentage of CD4+ cells in efferent lymph increases above the resting level during days 1, 2 and 3 post antigen stimulation. This is followed on days, 3, 4, and 5 after antigen stimulation by an increase in the percentage of CD8+ cells above the resting level which occurs as the percentage of CD4+ cells returns to the resting level. These changes cause the CD4/CD8 ratio to first increase above the resting value during the CD4 phase and then decrease below the resting value during the CD8 phase. During the CD4 phase a lymphokine activity is present in cell-free lymph fluid. Lymph fluid collected at this time supports the proliferation of activated T cells. Supernatants generated from efferent cells collected at a similar time and cultured in vivo for 24 h without any further stimulation are capable of releasing this material. During the CD8 phase cells expressing functional interleukin(IL)2 receptors appear in lymph fluid. The data suggests a sequential exit of T cell subsets from an antigen-stimulated lymph node and that the appearance of IL2-like activity and IL2-responsive cells in efferent lymph fluid are temporally distinct events.

Animals↗
PubMed1989

Pathophysiology of acute laminitis.

This article reviews research findings relating to the pathophysiology of acute laminitis in horses. The data presently available suggest that the onset of the condition may be due to constriction of the postcapillary vessels in the digit, leading to increased capillary hydrostatic pressure and movement of fluid into the interstitial space.

Acute Disease↗
PubMed1989

111Indium-labeled neutrophil migration into the lungs of bleomycin-treated rabbits assessed noninvasively by external scintigraphy.

Factors controlling neutrophil migration into the lung are poorly understood, but their identification is important for our understanding of the pathogenesis of inflammatory lung diseases. Pulmonary inflammation is difficult to quantify, and neutrophils in tissues and BAL may not accurately represent cell migration. In this study, intravenously delivered pulses of rabbit neutrophils labeled with Indium-111 (111In-neutrophils) were used to monitor neutrophil migration into the lungs. Radioactivity quantified in the lung "region of interest" (ROI) of external gamma camera scintigrams recorded 24 h after intravenous 111In-neutrophil injection accurately reflected the actual neutrophil-associated lung tissue radioactivity. ROI radioactivity at 24 h also correlated closely with the percent of 111In-neutrophils that had migrated into lavageable air spaces, and this parameter therefore provided an index of total lung 111In-neutrophil migration. Using 24-h ROI radioactivity and percent of injected 111In-neutrophils recovered in BAL at 24 h as indices of neutrophil migration into the lung, it was found that intratracheal saline caused only a transient neutrophil migration, whereas 10 U/kg intratracheal bleomycin induced migration that persisted for as long as 3 wk. 111In-neutrophil migration into the lung, assessed by external scintigraphy, correlated with total neutrophils quantified in histologic sections (r = 0.71, p = 0.006). The data suggest that this approach will be valuable in investigating mechanisms controlling neutrophil migration in lung inflammation, and that 111In-neutrophil scintigraphy may provide a noninvasive index of total lung neutrophil load that might be useful in staging inflammation in patchy diseases such as idiopathic pulmonary fibrosis.

Animals↗
PubMed1989

In vitro reactivity of digital arteries and veins to vasoconstrictive mediators in healthy horses and in horses with early laminitis.

The in vitro reactivity of vasoconstrictive mediators that are implicated in acute laminitis was determined in palmar and plantar digital arteries and veins obtained from healthy horses and in palmar digital vessels of horses with early laminitis (Obel grade I). To obtain baseline reactivity data, 3 experiments were conducted, using healthy horses: (1) the reactivity of palmar and plantar digital arteries and veins to angiotensin II, norepinephrine, and 5-hydroxytryptamine (serotonin) were compared; (2) the direct effects of bacterial endotoxin on vascular reactivity were assessed; and (3) the reactivity of palmar digital arteries and veins to angiotensin II, norepinephrine, prostaglandin F2 alpha (PGF2 alpha), serotonin, and a thromboxane-endoperoxide analog (U46619) were determined. The vascular reactivity of these same 5 vasoconstrictors then was determined in horses with early laminitis and was compared with data from healthy (control) horses. Obel grade-I laminitis was experimentally induced in horses, using carbohydrate overload. Dose responses were conducted for each agent at concentrations between 10(-8)M and 10(-4)M. The potency of a drug was defined as the mean effective concentration necessary to induce 50% of maximal contraction (EC50). There were no differences in EC50 concentrations and in maximal contractions between forelimb and hind limb arteries and veins for angiotensin II, norepinephrine, and serotonin. Incubation with endotoxin had no effect on the reactivity of arteries and veins to angiotensin II, norepinephrine, and serotonin.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1989

Clinical studies of a vegetarian food diet mixture.

A vegetarian food mixture when incorporated into a commercially prepared diet can be used as a supplement or in a vegetarian protein-sparing modified fast. A modification of this diet was given to protein-energy deficient malnourished children in Ethiopia, and it reversed their biochemical defects. The soluble or gel-forming fiber in the mixture also gives the product a favorable glycemic index and reduces glycemic excursion as well as fasting blood glucose and insulin levels. This accounts for the improvements seen in glucose tolerance in type II diabetic patients. These results, however, were preceded by a study of the effects of the mixture in improving glucose tolerance in diabetic rats. A clinical study among New Orleans police officers also suggests that this mixture helps people, without much self-motivation, to lose weight.

Adult↗
PubMed1989

Interactions of alcohol with amitriptyline, fluoxetine and placebo in normal subjects.

Amitriptyline (up to 75 mg/day), fluoxetine (up to 40 mg/day) and placebo were administered to 12 normal, healthy subjects for a period of 7 days. Subjects received each drug in random order and a minimum of 28 days was left between drug treatments. A battery of physiological, psychomotor and subjective tests was administered before drugs (day 1) and on days 4 and 8. On day 8 a measured dose of alcohol was given and the tests repeated at 1 and 3 h after alcohol. Tests before alcohol showed little effect on physiological or psychomotor activity either between drugs or between drugs and placebo. Subjective ratings did show some differences between drugs and in general amitriptyline was tolerated less well than fluoxetine. There were few differences between drugs after alcohol but with some measures the interaction with amitriptyline was subjective rather than additive or potentiating. This reflected the already substantial effects of amitriptyline alone.

Amitriptyline↗
PubMed1989

Ileal impaction in the horse: 75 cases.

Records of 75 horses with ileal impactions were examined retrospectively. There was a sex predilection towards mares. Arabians were over-represented compared to the hospital population. The average age was 8.3 years. Abdominal pain was observed in 96% of horses. Nasogastric reflux was present in 56% of horses, small intestinal distention was found on rectal palpation in 96% and an ileal impaction in 25%. Exploratory celiotomy was performed in 69 horses, the mass was reduced by extramural massage in 67 horses, and ingesta was removed via enterotomy in 2. Jejunocecostomies were performed in 47 horses. Twenty-five horses developed postoperative ileus, and 11 developed laminitis. Twenty-seven horses survived. Significant differences (p less than 0.05) between survivors and non-survivors were found for rectal temperature (37.7 and 38.2 degrees C, respectively), plasma protein concentration (7.8 and 8.9 g/dl, respectively) and anion gap (15 and 21.3 mEq/l, respectively). Survival decreased with increasing duration of clinical signs. Enterotomy, enterectomy, and/or jejunocecostomy performed during surgery had a deleterious effect on survival.

Animals↗
PubMed1989

Treatment of patent urachus associated with a congenital imperforate urethra in a calf.

Patent urachus is a common condition in calves which is frequently associated with omphalitis. A membranous urethral diaphragm prevented closure of the urachus in a female calf. The patent urachus was complicated by an ascending infection of the intraabdominal umbilical remnants. Following surgical removal of the urachus and umbilical vessels along with transection of the membranous diaphragm the calf experienced an uncomplicated recovery. This case stresses the importance of assuring urethral patency when managing a case of patent urachus.

Abnormalities, Multiple↗