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Biomedical subjects

D G Baker

Publications and source records attributed to D G Baker.

At least 73 records · Page 4Linked to original sources
PubMed1993

Inverse relationship between IgE and worm burdens in cattle infected with Ostertagia ostertagi.

Changes in serum total and Ostertagia-specific IgE levels, and pepsinogen concentrations were evaluated in 28 Holstein calves naturally or experimentally infected with Ostertagia ostertagi. In addition, IgE and pepsinogen concentrations were determined in abomasal lymph. Results showed that (1) lymph IgE responses were inversely correlated with worm burdens, and (2) serum IgE levels were unreliable for predicting worm burdens.

Animals↗
PubMed1993

N-type, omega-conotoxin-sensitive Ca2+ channels mediate electrically evoked release of ACh in guinea pig trachea.

To determine whether N- or L-type Ca2+ channels mediate acetylcholine (ACh) release from airway parasympathetic nerve endings, we compared the effects of omega-conotoxin (N-type inhibitor) and nifedipine (L-type inhibitor) on electrically evoked release of ACh in guinea pig trachea. Reconnected segments of guinea pig trachea were mounted in organ baths containing Krebs-Henseleit buffer, indomethacin (10 microM) to inhibit cyclooxygenase, neostigmine (1 microM) to inhibit acetylcholinesterase, and atropine (0.3 microM) to inhibit muscarinic autoreceptors, as well as phentolamine and propranolol to inhibit adrenergic receptors. After electrical field stimulation (EFS), aliquots of buffer were removed, and ACh was measured directly by high-performance liquid chromatography with electrochemical detection. Tracheas were stimulated for 10-min periods at a frequency of 5 Hz, and ACh release was measured for five separate periods (S1-S5) after treatment with increasing concentrations of omega-conotoxin or vehicle alone (acetic acid). Thirty minutes was allowed between stimulation periods. We found that EFS-evoked release of ACh was inhibited by omega-conotoxin in a concentration-dependent manner [mean effective concentration (EC50) approximately 8 nM] but was unaffected by vehicle treatment. In other experiments, ACh release was measured for two separate periods (S1 and S2), and between periods tracheas were treated with omega-conotoxin (1 microM), nifedipine (10-100 microM), tetrodotoxin (TTX), or buffer containing low (0.8 mM) Ca2+. ACh release was 12 +/- 2 (mean +/- SE) and 3 +/- 0.3 pmol.mg protein-1.min-1 before and during omega-conotoxin (n = 5, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1993

Abomasal interstitial fluid-to-blood concentration gradient of pepsinogen in calves with type-1 and type-2 ostertagiosis.

Pepsinogen and protein concentrations were determined in blood samples, collected from the left gastroepiploic artery and vein, and in abomasal lymph from 15 steers naturally infected with Ostertagia ostertagi and 4 uninfected steers. In steers with type-1 ostertagiosis, the concentration gradient between the mucosal interstitium and the blood alone could account for higher than normal serum pepsinogen concentrations. High interstitial pepsinogen concentrations may have resulted from increased epithelial permeability or increased pepsinogen production and secretion. However, in steers with type-2 ostertagiosis, the concentration gradient could not entirely account for the high serum pepsinogen concentrations, suggesting that capillary permeability or surface area may have been altered. Lymphatic uptake contributed pepsinogen to the blood in all infected steers.

Abomasum↗
PubMed1993

Competency assessment in the elderly.

Although brain changes and functional capacity impairment occur in both normal and abnormal aging, it is the extent of change which determines competency status. Dementia to some degree afflicts 10 percent to 15 percent of 30 million Americans over age 65. History, age-normed neuropsychological testing, and laboratory investigations are essential to competency assessment since physical and personality dysfunctions may masquerade as dementia. Since competency decisions profoundly impact the lives of the elderly, our fastest growing segment of national population, psychiatrists, psychologists, family physicians, and lawyers will become increasingly involved in competency issues.

Aged↗
PubMed1992

Distribution of catecholamine-containing nerves on blood vessels of the rat trachea.

This study was performed to determine the distribution of catecholamine-containing sympathetic nerves on blood vessels of the rat trachea. The glyoxylic acid method was used to visualize catecholamine-containing axons in tracheal whole mounts, and silicone vascular casts were used to elucidate the architecture of the vasculature. We also examined the relationship of these axons to the trachea's plexus of cholinergic nerves and ganglia, using tracheal whole mounts stained for acetylcholinesterase activity. We found that most catecholamine-containing axons were associated with arterioles located between cartilaginous rings or in the posterior membrane. In both regions, catecholamine-containing nerves were most abundant at the origin of terminal arterioles, which supplied the airway mucosa and smooth muscle. At the origin of these vessels, the fluorescent axons changed their orientation from longitudinal to circumferential. Few fluorescent axons were present beyond this region of the terminal arterioles, and none was found on capillaries or venules or on smooth muscle cells of the posterior membrane. Fluorescent axons were present in some tracheal ganglia but non enveloped neuronal cell bodies or had varicosities, and no ganglion cells had glyoxylic acid-induced fluorescence. Catecholamine-fluorescence was also present in clusters of small intensely fluorescent (SIF) cells, which were located in the adventitia of the posterior membrane and in the longitudinal nerve trunks which ran the length of the trachea. Pargyline pretreatment increased the fluorescence of axons and SIF cells but did not reveal a different distribution of these structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1992

Liver lipid profiles of adults taking therapeutic doses of aspirin.

The distributions of lipids of hepatic specimens obtained at autopsy from 7 adult patients who had been taking large amounts of aspirin for arthritis were compared to 7 control samples obtained from livers of autopsied adults without prior liver disease. The total neutral lipid levels of control livers were approximately one-third lower than those observed for livers of patients on aspirin. In addition, the phospholipid content of control specimens was significantly greater than that of livers from adult patients that had been on a high dose of aspirin for a long time. Examination of individual lipid classes showed that the concentrations of free fatty acids, triacylglycerols, and mono- and diacylglycerols were highest in livers of patients with aspirin exposure, and that all phospholipids were diminished. Phosphatidylcholines and phosphatidylethanolamines showed the greatest decrease. These results suggest that the livers of patients taking large amounts of aspirin may accumulate fatty acids and neutral lipids due to an impairment in the oxidation of fatty acids by hepatocytes. The data obtained also suggest that needle biopsy of the liver with measurement of distribution of hepatic lipids, perhaps together with histopathologic examination, may provide useful diagnostic information.

Aspirin↗
PubMed1992

Seasonal patterns of total and Ostertagia-specific IgE in grazing cattle.

Serum samples, collected monthly from January through December 1988 from 10 cows, their calves, and 10 yearling heifers, were used to determine total and Ostertagia-specific IgE levels. In addition, serum pepsinogen concentration, fecal egg counts, and body weights were measured. The following observations were made. (1) Total and Ostertagia-specific IgE levels followed similar seasonal patterns, being generally highest in the spring. (2) Breed and/or sire effects on total IgE levels were observed, with cattle from Angus-cross lines having higher levels than cattle of the other breeds tested. (3) Based on fecal egg counts, adult populations of Ostertagia ostertagi paralleled circulating IgE levels in the calves.

Animals↗
PubMed1992

Lung tumor incidence after intrabronchial administration of the nonionic contrast agent metrizamide.

RATIONALE AND OBJECTIVES: Metrizamide has been used for examination of the gastrointestinal tract and tracheobronchial tree of infants. Contrast agents may enter the lungs during such examinations. The current study was undertaken to determine whether there would be any later pulmonary effects when metrizamide was administered to the lungs of weanling mice. METHODS: One hundred fifty mice (18-21 days old), divided into groups, received either 75 microL of metrizamide, using the manufacturer's diluent (190 mg iodine [I]/mL), or saline solution administered to the lungs by injection into the trachea. The mice were observed for the duration of their lives. Moribund animals were killed. At death, all animals underwent necropsy. The lungs were fixed in formalin, and histologic sections were examined for pathologic changes. RESULTS: The incidence of lung tumors was increased (P less than .05) in the lungs of mice receiving metrizamide compared with those receiving saline. Eighteen percent of the lung tumors in the metrizamide-treated mice were lymphomas, a histologic type not found in the saline-treated controls. CONCLUSIONS: A hypothesis proposing that metrizamide may be an initiator of carcinogenic transformation rather than a carcinogen was developed.

Adenocarcinoma↗
PubMed1992

Direct measurement of acetylcholine release in guinea pig trachea.

In this study, we applied high-performance liquid chromatography with electrochemical detection (HPLC-EC) to the measurement of acetylcholine (ACh) release from nerve endings in guinea pig tracheal smooth muscle. We also tested for muscarinic inhibitory regulation of ACh release in this species, which is widely used for studies of airway neural control. Clip-connected segments of the posterior membrane of the guinea pig trachea were mounted in organ baths between stimulating electrodes and incubated in Krebs-Henseleit buffer containing (in microM) 10 indomethacin, 1 neostigmine, 1 phentolamine, and 1 propranolol. To measure ACh, the bath was emptied and aliquots of buffer were injected directly into the HPLC-EC; the lower limit of detection was 1 pmol/200 microliters sample. Electrical field stimulation (EFS) at 5 Hz for 10 or 30 min increased ACh release from 1.8 +/- 1.4 (SE) to 6.2 +/- 1.3 pmol.mg protein-1.min-1 (n = 15). The effect of atropine was examined by comparing amounts of ACh released by EFS before and after exposure to either atropine (0.3 microM) or vehicle. Before atropine treatment, EFS-evoked ACh release was 4.9 +/- 0.6 pmol.mg protein-1.min-1; after atropine exposure, EFS-evoked release of ACh increased significantly to 15.0 +/- 2.2 pmol.mg protein-1.min-1 (n = 11; P less than 0.05). Corresponding values before and during exposure to vehicle were 9.3 +/- 4.4 and 10.7 +/- 4.7 pmol.mg protein-1.min-1, respectively. The ratios of the changes in EFS-evoked ACh release were 3.1 +/- 0.3 and 1.3 +/- 0.1 in atropine-treated and vehicle-treated groups, respectively (P less than 0.05). We conclude that HPLC-EC is a reliable and sensitive technique for the detection of EFS-evoked release of ACh from clip-connected segments of guinea pig tracheal smooth muscle.

Acetylcholine↗
PubMed1992

Comparison of the acute inflammation induced by calcium pyrophosphate dihydrate, apatite and mixed crystals in the rat air pouch model of a synovial space.

Pure monoclinic or triclinic calcium pyrophosphate dihydrate (CPPD) crystals, apatite crystals or mixtures of these crystals were injected into the synovial-like space created by the rat air pouch to compare the acute inflammation induced by these crystals. Fluids were withdrawn 6 h after injection and examined for leukocyte counts, protease, prostaglandin E2 (PGE2) and tumor necrosis factor (TNF) levels. CPPD crystals (especially monoclinic CPPD) induced higher numbers of leukocytes, and more protease, PGE2 and TNF than apatite. CPPD seemed to play a predominant role in the acute inflammation induced by mixed crystals.

Animals↗
PubMed1992

Estimated synovial fluid leukocyte numbers on wet drop preparations as a potential substitute for actual leukocyte counts.

Leukocyte counts on synovial fluid are widely used in classification of joint disease as inflammatory or "noninflammatory." We have evaluated estimates of leukocytes (WBC) per high power field (HPF) on wet drop preparations to see if they might be suitable substitutes in some situations. If there was a mean WBC of 0-2/field on 10 HPF, all leukocyte counts were less than 1,300/mm3. Thus, in such fluids expense might be reduced by eliminating the actual leukocyte count. Estimates also roughly correlated with WBC counts at higher counts but were less consistent.

Arthritis↗
PubMed1991

Predicting length of children's psychiatric hospitalizations: an "ecologic" approach.

This article describes the development and validation of a simple and modestly successful model for predicting inpatient length of stay (LOS) at a state-funded facility providing acute to long term care for children and adolescents in Ohio. Six variables--diagnostic group, legal status at time of admission, attending physician, age, sex, and county of residence--explained 30% of the variation in log10LOS in the subgroup used to create the model, and 26% of log10LOS variation in the cross-validation subgroup. The model also identified LOS outliers with moderate accuracy (ROC area = .68-0.76). The authors attribute the model's success to inclusion of variables that are correlated to idiosyncratic "ecologic" factors as well as variables related to severity of illness. Future attempts to construct LOS models may adopt similar approaches.

Adolescent↗
PubMed1991

Potential HIV exposure in psychiatrically hospitalized adolescent girls.

The authors surveyed 23 psychiatrically hospitalized adolescent girls regarding behavior that involves high risk of HIV infection. Over half (57%) of the girls reported high-risk sexual activities; these girls were more likely to have sexually transmitted diseases, substantial drug abuse histories, and diagnoses of conduct disorder.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Celiac trunk cannulation for obtaining abomasal lymph from cattle.

Cannulation of the celiac trunk was surgically performed in 26 Holstein steers. The procedure was successful in 23 (88.5%) of the steers. Twenty-two of the steers were infected either naturally or experimentally with the abomasal nematode, Ostertagia ostertagi and/or other gastrointestinal parasites. The remaining 4 steers were not infected. Lymph obtained after surgery was used in various immunologic and biochemical assays. Daily lymph flow rate and total and differential WBC counts were determined after surgery in 4 of the infected and 3 of the noninfected steers. Steers were euthanatized for tissue specimen collection 7 days after surgery. At the time of euthanasia, lymph was still flowing from the cannula of 13 (56.5%) of the steers in which surgery was successful. This surgical procedure represents a valuable technique for studying at the local level, immunologic and physiologic responses of cattle to infection with O ostertagi.

Animals↗
PubMed1990

Monosodium urate crystals stimulate phospholipase A2 enzyme activities and the synthesis of a phospholipase A2-activating protein.

Eicosanoids are important mediators of the inflammatory response to monosodium urate crystals (MSUC) that results in gout. Phospholipase enzymes cleave fatty acids from membrane phospholipids, and this is thought to be the rate-limiting step in eicosanoid production. To understand better the mechanism of eicosanoid production in this disease, we stimulated human peripheral blood neutrophils and monocytes with MSUC and measured phospholipase enzyme activities. MSUC stimulated both intracellular and secretory phospholipase A2 enzyme activities in a time and concentration-dependent manner. Specificity was observed, as phospholipase C activities were not affected. Pretreatment with colchicine, but not aspirin, indomethacin, allopurinol, or islet activating protein, abrogated the enhanced phospholipase A2 activities. We have recently isolated and characterized a phospholipase A2 activating protein termed PLAP from synovial fluid from patients with rheumatoid arthritis, and from murine and bovine cell lines. PLAP was detected in gouty synovial fluid by immunodot blotting and ELISA assays and expressed the same characteristics as PLAP identified from other sources. To examine the role of PLAP in MSUC-induced phospholipase A2 stimulation, we treated cells with MSUC and observed an increase in immunoreactive PLAP. This response also could be blunted by colchicine, but not other drugs. Both phospholipase A2 and PLAP induced production by human monocytes of PGE2 and leukotriene B4 by neutrophils. These findings suggest that phospholipase A2 activation in response to MSUC requires an intact microtubule structure, and that phospholipase A2 and PLAP may be important modulators of at least a portion of the gouty inflammatory response.

Cell Survival↗
PubMed1990

Cardiovascular and neuromuscular effects of three steroidal neuromuscular blocking drugs in dogs (ORG 9616, ORG 9426, ORG 9991).

Developmental research has been directed toward creating nondepolarizing muscle relaxants with an onset time and duration of actions shorter than that of vecuronium or atracurium. We determined the cardiovascular and neuromuscular effects of three new and promising nondepolarizing muscle relaxants in six dogs anesthetized with halothane. Each dog was anesthetized four times (each time separated from the others by at least 1 wk); one muscle relaxant was studied each time. Three doses (one, three, and five times the ED90) were given as intravenous bolus injections. ORG 9616 and ORG 9991 had shorter durations of action than ORG 9426. The duration of action of the doses that were five times the ED90 was 18 +/- 5.88 and 15.8 +/- 4.41 min (mean +/- SD) with ORG 9616 and ORG 9991, respectively, as compared with 39.7 +/- 17.15 min with ORG 9426 (P less than 0.05). ORG 9426 was virtually free of cardiovascular effects. The ED90 doses of ORG 9616 and ORG 9991 did not cause cardiovascular effects; the doses of three and five times the ED90 caused small decreases in mean arterial blood pressure and increases in heart rate. Mean arterial blood pressure decreased from 99 +/- 10.2 to 88 +/- 13.1 mm Hg and from 98 +/- 11.7 to 77 +/- 8.1 mm Hg with five times the ED90 dose of ORG 9616 and ORG 9991, respectively. The authors conclude that ORG 9426 has a duration of neuromuscular blockade that is probably similar to vecuronium, and one that is free of cardiovascular effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Androstanols↗
PubMed1990

[Immunoglobulin G coating of ceramic powders enhances superoxide production].

Crystals and a group of ceramics used in joint replacement surgery were incubated with polymorphonuclear cells with and without adsorbed immunoglobulin G to study their ability to generate superoxide anion. All eight particles tested had the capacity to induce superoxide anion to at least some extent. Alumina ceramic and some of the ceramics adsorbed small amounts of immunoglobulin G onto their surfaces and the increment of superoxide production was also small. Both the augmentation of superoxide anion and the adsorption of immunoglobulin G to tricalcium phosphate ceramic and the remaining ceramics were intermediate. Synthetic monosodium urate crystals adsorbed immunoglobulin G most efficiently with large increments of superoxide anion. The increase in superoxide production by the adsorption of immunoglobulin G depended on the amount of immunoglobulin G bound onto crystals or ceramics. The greater phlogistic potential of some ceramics need to be taken into consideration in their clinical use.

Adsorption↗