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Biomedical subjects

E M Keough

Publications and source records attributed to E M Keough.

At least 19 recordsLinked to original sources
PubMed1987

Intracisternal granules in the somatotrophs in the anterior pituitary of the mouse.

A detailed study of the anterior pituitaries of pregnant and lactating mice revealed changes occurring in the ultrastructure of the somatotrophs. The rough endoplasmic reticulum cisternae become greatly dilated forming channels that are continuous with the perivascular space. This occurrence expands the membrane surface available for the release of hormone. Individual granules and cytoplasmic islands containing numerous granules appear in these channels. This suggests an alternative mechanism for granule release which would facilitate a rapid response to increased hormone requirement.

Animals↗
PubMed1986

Endothelial cell seeding of small-caliber synthetic grafts in the baboon.

Endothelial cell (EC) seeding has been proposed as a method to improve the performance of small-caliber synthetic vascular prostheses. Seeding experiments to date have all been carried out in the dog. This study investigates EC seeding of small-caliber Dacron carotid interposition grafts compared with contralateral control grafts in the baboon. Surface thrombogenicity was assessed at 24 hours, 2 weeks, and 4 weeks after implantation with indium 111-labeled autologous platelets. Morphologic and immunohistochemical techniques were used to assess the identity and homogeneity of the EC inoculum before seeding and to identify cell types on the harvested grafts. There was no significant difference in patency rates between seeded and control grafts at 5 weeks. Platelet accumulation on seeded grafts was significantly less (p less than 0.05) than on paired controls at 2 and 4 weeks after implantation. The luminal lining of seeded grafts had more cellular ingrowth, less adherent thrombus, and more surface cells with the morphologic and histochemical characteristics of EC than did the lining of controls. EC seeding reduces the platelet reactivity and accelerates EC coverage of small-caliber grafts in the baboon.

Animals↗
PubMed1985

The isolation and characterization of Ca++-accumulating subcellular membrane fractions from cerebral arteries.

A study was undertaken using differential centrifugation methods to isolate from rabbit cerebral arteries the subcellular microsomal protein fractions capable of actively sequestering Ca++. One isolated protein fraction displayed a relatively large adenosine triphosphate (ATP)-dependent Ca++-accumulating capacity that was completely inhibited by NaN3, and was therefore designated the "mitochondrial fraction." Electron microscopy confirmed that this fraction consisted of numerous mitochondrial elements. Another isolated membrane fraction possessed a Ca++-accumulating capacity dependent on ATP and oxalate and only partially sensitive to NaN3. In the presence of mersalyl acid or the Ca++ ionophore, A23187, Ca++ uptake by this fraction was inhibited 98.0% and 87.4%, respectively. Electron microscopy revealed that this fraction consisted of numerous membrane vesicles, and measurements of Na+-K+-ATPase (adenosine triphosphatase) activity indicated minimal plasma membrane contamination. It was concluded that this microsomal fraction consisted primarily of sarcoplasmic reticulum. At physiological free [Ca++] levels, Ca++ uptake by this fraction was inhibited by norepinephrine through a process sensitive to tolazoline but not propranolol. The effects on Ca++ uptake of added cyclic adenosine monophosphate (cAMP) alone or with rabbit or bovine protein kinase were inconclusive. The organic Ca++ channel blockers, nifedipine and verapamil, significantly inhibited Ca++ uptake by sarcoplasmic reticulum.

Adenosine Triphosphate↗
PubMed1984

Healing pattern of small caliber dacron grafts in the baboon: an animal model for the study of vascular prostheses.

Although dogs have been used widely to study the healing of large caliber synthetic grafts, hypercoagulability probably makes the dog a poor model for studies of small caliber vascular prostheses. The baboon's coagulation system is similar to man's, but large caliber baboon grafts were reported to endothelialize rapidly. In this study the healing pattern of 4 mm internal diameter Dacron carotid interposition grafts in baboons was determined using specimens harvested at time points between 2 weeks and 18 months post-implantation and examined with light and scanning electron microscopy. The luminal surface of baboon grafts in the acute healing phase (less than 1 month) was comparable to that reported in the literature for dogs. Baboon grafts did not completely endothelialize until 10-12 weeks post-implantation. For work with small caliber vascular prostheses, the dog appears to have no advantage over the baboon as an animal model on the basis of graft healing.

Animals↗
PubMed1984

A baboon flow-regulated shunt for the study of small caliber vascular grafts.

Synthetic vascular grafts often occlude when used in low-flow high-resistance reconstructions. In order to study the pathophysiology of graft failure a flow-regulated ex vivo shunt was designed for insertion into the baboon femoral artery and vein. Synthetic graft materials (4 mm i.d.) can be placed into the shunt circuit and studied at known rates of flow for uptake of 111In-labeled platelets. Segments of the grafts can be removed from the shunt circuit at specified time intervals for morphologic study with scanning electron microscopy (SEM). In this paper the shunt model is described in detail and early experiments with it are reported. Labeled platelet uptake and SEM studies suggest that flow rate and graft composition influence the deposition of platelets and other blood components on graft surfaces. At high-flow knitted Dacron attracts large numbers of platelets, and becomes covered with a nearly confluent platelet-protein carpet within 1 hr. At low flow platelet uptake and development of the platelet-protein carpet is slower. Polytetrafluoroethylene (PTFE) attracts few platelets at high-flow rates, but at lower-flow rates begins to develop a platelet-protein carpet similar to that seen on knitted Dacron. Flow-related factors influencing platelet deposition are discussed and further experiments to be carried out with this model are described.

Animals↗
PubMed1984

Aspirin decreases platelet uptake on Dacron vascular grafts in baboons.

The influence of a single dose of aspirin (5.4-7.4 mg/kg) on platelet uptake on 4-mm Dacron interposition grafts was studied in a baboon model using gamma camera scanning for 111-Indium labeled platelets. In vitro assessment of platelet function after aspirin administration revealed that in the baboon, as in the human, aspirin abolished arachidonic acid-induced platelet aggregation, prolonged the lag time between exposure to collagen and aggregation, and decreased plasma thromboxane B2 levels. Aspirin also prolonged the template bleeding time. Scans for 111-Indium labeled platelets revealed that pretreatment with a single dose of aspirin decreased platelet uptake on 4-mm Dacron carotid interposition grafts. This decrease in platelet uptake was associated with a significant improvement in 2-hour graft patency and with a trend toward improved 2-week patency.

Animals↗
PubMed1983

Primate ocular blood flow following contiguous recti tenotomy.

Tenotomy of the medial and superior recti resulted in decreased blood flow to only the superior quadrant of the unit iris, ciliary body with processes (ICBCP). Blood flow to the medial, lateral, and inferior quadrants of the ICBCP was maintained. These data support the contention that tenotomy initiates a compensatory increase in medial quadrant blood flow, probably via the medial long posterior ciliary artery. The superior quadrant appears to be the least protected from ischemia immediately following recti tenotomy.

Animals↗
PubMed1981

Comparative extraocular muscle blood flow.

This study was designed to quantitatively determined blood flow to the extraocular muscles (EOM) of animals showing a wide range of ocular motility Blood-flow values (ml/minute/gm) for EOM in primates (0.25 +/- 0.03), dogs (0.33 +/- 0.06), sheep (0.12 +/- 0.01), and geese (0.12 +/- 0.04) were determined using the Reference Sample Method with 15 +/- 3 micrometer 103Ru microspheres and complete cardiovascular monitoring. Mammalian EOM blood flow was significantly higher than that determined for other skeletal muscle; however, EOM blood-flow values for sheep were significantly lower than those for primates and dogs. No significant blood-flow differences were found between avian EOM and other skeletal muscle, reflecting the unique avian ocular anatomy. These data indicate that high blood flow is not a general property of EOM and suggest a relationship between functional ocular motility and blood flow.

Animals↗
PubMed1981

Heparin and small caliber polytetrafluoroethylene grafts in the carotid arteries of rats.

Polytetrafluoroethylene (PTFE) grafts having an internal diameter of 1 mm were implanted in the common carotid arteries of rats with or without the simultaneous application of various heparin regiments. Graft patency was determined from postoperative angiograms, and grafts were patent 40 days after surgery were harvested for light microscopic examination. The level of anticoagulation produced by the various heparin regimens was measured in separate groups of rats and found to be clinically therapeutic. All of the grafts from rats that did not receive heparin were occluded at 24 hours. In the two groups of rats that received high doses of heparin, 5 of 10 and 4 of 11 grafts were patent 40 days postoperatively. There were no patent grafts three days postoperatively in the group receiving low doses of heparin. The grafts that were patent 40 days postoperatively had lumens that were completely lined with presumptive endothelial cells. Further laboratory experimentation is needed before PTFE small caliber grafts can be recommended for use in humans.

Animals↗
PubMed1980

The effect of complete tenotomy on blood flow to the anterior segment of the canine eye.

The relative importance of the anterior ciliary arteries to blood flow to the anterior segment and the quadrant distribution of blood to the iris, ciliary body, and ciliary processes were determined in canines with the use of 15 +/- 3 mum 103Ru microspheres with the reference blood flow method. Recti muscles were isolated in both eyes. Then with one eye serving as a sham-operated control, anterior ciliary artery blood flow was disrupted by recti tenotomy immediately prior to microsphere injection. Tenotomy resulted in a significant decrease in blood flow to the anterior segment (0.14 +/- 0.03 ml/min/gm vs. 0.26 +/- 0.05 in the untenotomized control) and to the unit iris, ciliary body and ciliary processes (I, CB, CP) (0.92 +/- 0.16 ml/min/gm vs. 1.44 +/- 0.22 in the untenotomized control). Blood flow values for the anterior segment and the unit I, CB, CP in the tenotomized eye were 50% to 60% of those of the control eyes, indicating that the majority of blood flow to the canine anterior segment is not disrupted by complete tenotomy. In the control eye, blood flow values for the medial quadrant of the unit I, CB, CP were significantly higher (p < 0.05) than those of the inferior or superior quadrants. Blood flow values for all quadrants in tenotomized eyes were 55% to 70% of those for control eyes. Therefore the anterior ciliary arteries do not contribute the majority of blood flow to the canine anterior segment.

Animals↗
PubMed1979

Mammary gland development during pregnancy in the dwarf mouse mutant, little.

Little (lit) is a single gene dwarf mutation described in the C57Bl/6J strain of laboratory mouse. This study was designed to determine the effect of the mutation little on mammary gland development during pregnancy and post-partum periods. Failure of mutant females to lactate at first parturition appears to be due to the endocrine environment of the gland rather than any intrinsic defect of the mammary epithelium. Treatment of primiparous lit/lit females with exogenous growth hormone or prolactin resulted in lactogenesis. Treatment with hydrocortisone resulted in increased amounts of organized rough endoplasmic reticulum but lactation did not occur.

Animals↗
PubMed1978

The effects of adrenalectomy and cortisol treatment on cell types, other than corticotrophs, in the anterior pituitary of the mouse.

This investigation was designed to characterize changes due to adrenalectomy and cortisol treatment in cell types, other than corticotrophs, in the anterior pituitary of the mouse. Cortisol injections resulted in a reduced number of mammotrophs and an increased number of somatotrophs. By 5 days post-adrenalectomy an increase in the number of mammotrophs and a decrease in the number of somatotrophs was observed. No changes were noted in the number of gonadotrophs or thyrotrophs due to either adrenalectomy or cortisol treatment.

Adrenal Glands↗
PubMed1976

Ionophore A23187 induces acrosome reactions in sea urchin and guinea pig spermatozoa.

Ionophore A23187, in the presence of extracellular Ca+2, induces a morphologically normal acrosome reaction in sperm of the sea urchin and precocious acrosome reaction and activation of guinea pig sperm. Increased membrane permeability to Ca+2 is responsible for initiating the acrosome reaction in both sea urchin and guinea pig sperm. In sea urchin sperm, the permeability change is brought about by egg jelly, whereas in the guinea pig sperm it accompanies capacitation.

Acrosome↗
PubMed1976

The role of calcium in the acrosome reaction: an analysis using ionophore A23187.

The role of Ca+2 in the acrosome reaction of echinoid and mammalian sperm was investigated using the Ca+2 transporting ionophore A23187. The ionophore induced morphologically normal acrosome reactions in both types of sperm (as assessed by electron microscopic observation of echinoid sperm and phase contrast microscopic observation of mammalian sperm). In echinoids, these reactions were immediate. In the guinea pig and hamster, ionophore significantly decreased the capacitation interval; early reactions were accompanied by activation of motility. Ionophore induced reactions were affected by sperm, ionophore and Ca+2 concentrations. Since both ionophore induced and natural reactions require extracellular Ca+2, it is suggested that an influx of Ca+2 represents the initial step of the acrosome reaction. Under natural conditions, the permeability change which results in Ca+2 influx may be induced in echinoid sperm by egg jelly and may occur in mammalian sperm during capacitation. Ionophore A23187 should prove an experimentally useful drug for further study of the acrosome reaction since its effect on cells is understood, it induces synchronous reactions in a high percentage of sperm, and it conveniently reduces the capacitation interval in mammalian sperm.

Acrosome↗