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Biomedical subjects

M D Campbell

Publications and source records attributed to M D Campbell.

At least 19 recordsLinked to original sources
PubMed2000

The fall, recovery, orbit, and composition of the Tagish Lake meteorite: a new type of carbonaceous chondrite.

The preatmospheric mass of the Tagish Lake meteoroid was about 200,000 kilograms. Its calculated orbit indicates affinity to the Apollo asteroids with a semimajor axis in the middle of the asteroid belt, consistent with a linkage to low-albedo C, D, and P type asteroids. The mineralogy, oxygen isotope, and bulk chemical composition of recovered samples of the Tagish Lake meteorite are intermediate between CM and CI meteorites. These data suggest that the Tagish Lake meteorite may be one of the most primitive solar system materials yet studied.

Journal Article↗
PubMed2000

Endocardial ossifying myxoma of the right atrium in a cat.

Primary cardiac neoplasms are rare in humans and animals. In humans, the most common primary cardiac tumor is the myxoma, which is frequently found in the left atrium. Cardiac myxoma has been reported in the dog but not in the cat. We describe the gross, immunohistochemical, and light microscopic examination of a myxoma in the right atrium of a 6-year-old domestic shorthair cat. Histologically, the tumor consisted predominantly of mesenchymal cells with several foci of bone and cartilage present. The tumor was encapsulated and benign.

Animals↗
PubMed1998

Femoral component failure in hybrid total knee arthroplasty.

From 1986 to 1991, 74 consecutive hybrid total knee arthroplasties (in 65 patients) of a single design were performed at the authors' institution. Seven patients (eight knees) died with well functioning replacements during the surveillance period. One patient refused to participate in any followup efforts because of billing disputes. This left 65 total knee arthroplasties (57 patients) for review. There were 35 men and 22 women with an average age of 60 years (range, 27-83 years) at the time of arthroplasty. The underlying diagnosis was osteoarthritis in 46 knees, rheumatoid arthritis in six knees, and other in four knees. The average length of followup was 7.4 years (range, 5-10 years), and no patients were lost to followup. The Knee Society scores improved from an average of 37 preoperatively to 84 at latest followup. The functional score improved from 49 to 69 at latest followup. Ten (13.8%) knees required revision surgery. Eight of the nine knees that were revised had femoral component problems, including a loose component in six and a fractured component in two. One knee was revised for polyethylene wear with secondary osteolysis and one was revised elsewhere in which the operative details are unknown. The implant survival to revision at 5 years was 89% and 85% at final followup. Femoral component fixation in hybrid total knee arthroplasty in unreliable with this component design. In light of the excellent 10- to 15-year results of cemented condylar knee designs it is thought that hybrid fixation should be abandoned.

Adult↗
PubMed1998

Polyarticular blastomycotic arthritis.

Blastomycotic arthritis usually presents as acute monoarticular septic arthritis resembling a bacterial process. Only 2 cases in the literature have subsequently developed arthritis in a second joint. We describe the case of an elderly woman with polyarticular blastomycotic arthritis associated with lung, skin, and bone involvement. The organism was identified in the synovial fluid and skin biopsies. Our patient underwent open drainage and aspiration of the involved joints and received antimycotic therapy.

Aged↗
PubMed1994

Free radical-induced generation of isoprostanes in vivo. Evidence for the formation of D-ring and E-ring isoprostanes.

We recently reported the discovery that a series of novel prostaglandin (PG)F2-like compounds (F2-isoprostanes) are produced in vivo independent of the cyclooxygenase as products of free radical-catalyzed lipid peroxidation. F2-isoprostanes are initially formed in situ from arachidonic acid esterified to phospholipids and then released preformed. We have now investigated whether PGD2/E2-like isoprostanes are also produced by rearrangement of the PGG2-like intermediates involved in isoprostane formation. Using a variety of approaches utilizing mass spectrometry, compelling evidence was obtained for the presence of D2/E2-isoprostane-containing phosphospholipids in the liver (85 +/- 33 ng/g of liver) and free D2/E2-isoprostanes in the circulation (215 +/- 90 pg/ml) of rats treated with CCl4 to induce lipid peroxidation. In untreated rats, levels of D2/E2-isoprostanes esterified in liver phospholipids were much lower (0.90 +/- 0.10 ng/g), and free compounds could not be detected in the circulation (< 5 pg/ml). Interestingly, one of the E2-isoprostanes that would be expected to be formed in abundance, 8-epi-PGE2, was found to be a potent renal vasoconstrictor, and these effects could be abrogated by SQ29548, a thromboxane receptor antagonist. Further understanding of the biological consequences of the formation of these novel compounds and factors that influence their formation may provide valuable insights into the pathophysiology of oxidant injury.

Animals↗
PubMed1990

Cyclic AMP inhibits inositol polyphosphate production and calcium mobilization in neuroblastoma X glioma NG108-15 cells.

In the neuroblastoma X glioma hybrid cell line NG108-15, bradykinin (BK) receptor stimulation induced a rapid and concentration-dependent rise in cytosolic free Ca2+ levels, as measured with the Ca2(+)-sensitive fluorescent dye fura-2. The Ca2+ transient was present in the absence of extracellular Ca2+ and was associated with a concentration-dependent production of inositol phosphates, particularly inositol trisphosphate (InsP3). Pretreatment of intact NG108-15 cells with forskolin or dibutyryl-cAMP plus isobutylmethylxanthine reduced BK-stimulated InsP3 production and the increase in cytosolic free Ca2+. Membranes prepared from forskolin- and [3H]inositol-pretreated NG108-15 cells also showed a diminished production of InsP3 elicited by guanosine 5'-[gamma-thio]triphosphate, NaF, or BK plus GTP. On the other hand, the Ca2+ sensitivity of membrane-associated phosphoinositide-specific phospholipase C (PI-PLC) was unaffected by forskolin pretreatment of intact NG108-15 cells. Collectively, these results suggest that A-kinase may inhibit receptor-mediated and postreceptor stimulation of PI-PLC in neuron-like cells, perhaps by impairing the coupling between a guanine nucleotide-binding protein and PI-PLC.

Adenylyl Cyclases↗
PubMed1989

Reduction of norepinephrine-induced tonic contraction and phosphoinositide turnover in arteries of spontaneously hypertensive rats. A possible role for protein kinase C.

Experiments were conducted to determine whether a difference in receptor-induced phosphatidylinositol hydrolysis occurred in aorta from spontaneously hypertensive rats (SHR) v Wistar-Kyoto (WKY) rats, and whether such a difference was correlated with contractile response. Basal incorporation of 32P into phosphatidylinositol (PI), phosphatidylinositol phosphate (PIP), phosphatidylinositol diphosphate (PIP2) and phosphatidic-acid (PA) was not different between SHR and WKY groups. However, after five minutes of norepinephrine (NE; 10 mumol) exposure, increases in 32P labeling were markedly lower in SHR arteries. The percentage decrease amounted to 45% for PI, 68% for PIP, 100% for PIP2 and 58% for PA. Basal incorporation of 3H-myo-inositol into inositol monophosphate (IP) was similar for SHR and WKY groups. However, after 30 minutes of NE (10 mumol), SHR arteries failed to show an increase in 3H-IP levels, whereas labeling was increased 219% in WKY arteries. The contractile response of SHR arteries to 10 mumol NE showed a marked reduction in the rate of development of the tonic phase that has previously been shown to be supported by activity of protein kinase C. Higher Ca2+ levels failed to augment the SHR response, whereas WKY responses were significantly increased. Contractions in the presence of the phorbol ester tetradecanoylphorbolacetate exhibited a similar reduction in NE-induced tonic phase tension. These results indicate an impairment in SHR arteries at the level of receptor-induced formation of inositol cycle second messengers, possibly due to elevated basal levels of protein kinase C. These differences may be important in explaining altered vascular responses in primary hypertension.

Animals↗
PubMed1986

Differences in phospholipid incorporation of 32P relevant to alpha 1-receptor coupling events in rat and rabbit aorta.

Labelling of membrane phospholipids with 32P was compared in rat and rabbit aorta under basal conditions and during alpha 1-receptor stimulation. Incorporation of 32P proceeded at a significantly higher rate in rat tissue. The ratio of basal labelling following 30 min of incubation for rat/rabbit arteries was 4.8 for phosphatidylinositol diphosphate (PIP2), 6.0 for phosphatidylinositol phosphate (PIP), 9.0 for phosphatidylinositol (PI), 6.0 for phosphatidic acid (PA) and 18.7 for phosphatidylcholine (PC). Addition of 10(-5)M norepinephrine (NE) to labelled tissues resulted in a similar decrease in [32P]-PIP2 in both rat and rabbit tissues. Greater percent increases were seen in rabbit tissue of [32P]-PA (4-6 fold), and [32P]-PI (3-5 fold), when measured over the initial 10 minutes of agonist exposure. While NE caused a gradual increase of 32P incorporation into PC in rabbit aorta, reaching 180% above control after 10 minutes, PC labelling was not increased in rat aorta. Our findings provide evidence for the enhanced labelling of rat vs rabbit aorta phospholipids. This may account for differences in receptor responses and associated Ca+ movements which have been previously recognized to exist between aorta of these two species.

Animals↗
PubMed1985

Phosphoinositide hydrolysis is correlated with agonist-induced calcium flux and contraction in the rabbit aorta.

In the present study changes in the extent of 32P labelling of membrane phospholipids were correlated with the alpha 1-adrenoceptor-induced events of increased 45Ca influx, 45Ca release and contraction in the rabbit aorta. Under basal conditions 32P incorporation into all phospholipids proceeded without saturation through 80 min of labelling. During a 5 min exposure to 10(-5) M norepinephrine (NE) after 25 min of prelabelling the incorporation of 32P into certain phospholipids was substantially increased. Phosphatidic acid (PA) labelling was increased above basal levels by 4.1 fold, phosphatidylinositol (PI) 2.5 fold and phosphatidylcholine (PC) 1.8 fold. Half maximal stimulation of 32P labelling of PA occurred at 2.0 microM, which was similar to the EC50 value for stimulation of 45Ca influx (2.5 microM) and 45Ca release (2.1 microM) but slightly higher than the value for contractile response (0.9 microM). Antagonist sensitivity studies reinforced the alpha 1 receptor subtype character of the rabbit aorta. Prazosin (10(-7) M) reduced agonist-induced events by 63-82% while yohimbine (10(-7) M) was without influence. Phenoxybenzamine (10(-8) M) reduced agonist-induced events by 56-76%. A temporal comparison showed that agonist stimulation of PA labelling was slower than 45Ca release, but similar to the time course of 45Ca influx. Hydrolysis of 32P-labelled phosphatidylinositol diphosphate (PIP2) was more rapid and paralleled 45Ca release. These findings suggest that PIP2 hydrolysis may account for the rapid phase of norepinephrine-induced contraction in rabbit aorta while PA or its immediate precursor diacylglycerol may account for receptor-induced Ca2+ influx.

Animals↗
PubMed1981

Determination of plasma fibrinogen concentration in the horse.

The microhematocrit heat-precipitation methods of Millar et al (1971) and Schalm et al (1975) were compared with the reference clottable protein method of Ratnoff and Menzie (1951) in the measurement of plasma fibrinogen concentration in horses. The millar et al method was more precise and accurate and showed better positive correlation with the reference method than did the Schalm et al method. There was no significant difference in the plasma fibrinogen concentration between healthy Thoroughbreds and healthy horses of other breeds. Horses with bacterial pneumonia and abscesses had significantly greater plasma fibrinogen values than did those with colic, fractures, and nonsuppurative wounds. The Millar et al method was recommended as a simple, relatively accurate procedure for the determination of plasma fibrinogen that might be used as an additional diagnostic and prognostic indicator in the laboratory investigation of diseases in the horse.

Animals↗
PubMed1976

Progesterone synthesis by luteal mitochondria in vitro.

Mitochondria were prepared from bovine corpora lutea by differential centrifugation and were purified by isopycnic zonal centrifugation. A marked increase in specific cytochrome oxidase activity and a marked decrease in specific DNA and RNA content indicate that the procedure resulted in a highly purified preparation of mitochondria. These organelles had a higher rate of conversion of [4-14C] cholesterol to [4-14C] progesterone than did mitochondria separated only by differential centrifugation, suggesting that luteal mitochondria contain the enzyme systems required for progesterone synthesis.

Animals↗
PubMed1975

Behavioral Effects of Reducing the Daily Frequency of Phenothiazine Administration.

After an 11-day base line of behavioral observations, 24 chronic female schizophrenics were assigned to two groups matched for alertness. In the first treatment phase, the administration of phenothiazine medication of one group was switched from a multiple-dose schedule (three to four times per day) to a single daily administration, while the total dosage per day was held constant. The second group continued on a multiple administration schedule for 11 days and then was switched to a single daily dosage. A multivariate analysis of variance showed that there was no overall effect (positive or negative) due to the schedule change; however, preplanned t tests showed transitory decreases in nonfunctional behavior. The results are discussed in terms of implications for the administration of phenothiazines and the experimental analysis of drug effects.

Adult↗