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Biomedical subjects

S Greenberg

Publications and source records attributed to S Greenberg.

At least 199 records · Page 11Linked to original sources
PubMed1976

Postulated developmental forms in the life cycle of the lymphocystis virus.

Electron micrographs of lymphocystis sk8n lesions obtained from the walleye pike, Stizostedion vitreum, show viral particles of differing sizes and morphologies. Earlier studies have described only particles ranging in size from 200-250 mmu in diameter. We show, in addition, new forms (65-100 mmu in diameter) intermingled among the large particles and also contained within the latter. Both forms are associated with a single inclusion body. The possible role of the small particle in the life cycle of the virus is discussed.

Animals↗
PubMed1976

Comparison of the effects of prostaglandins A, E, F, and B on the canine pulmonary vascular bed.

The present data show that prostaglandins of the A, E, F, and B series have a wide spectrum of effects on the canine pulmonary vascular bed. PGF2alpha and PGB2 were very potent pulmonary pressor substances. Both of these agents increased pressure in the lobar artery and small vein. Since blood flow was constant and left atrial pressure did not rise, the increase in lobar arterial pressure reflects an increase in resistance to flow in the lung. The rise in venous pressure and the increase in pressure gradient between lobar artery and vein indicate that these substances increase pulmonary vascular resistance by constricting lobar veins and upstream vessels presumed to be small arteries. PGE1 and PGA1 both dilated the pulmonary vascular bed and the decrease in resistance was due to dilation of veins and upstream vessels. In the dog, both PGE2 and PGA2 were found to be modest pulmonary pressor substances. The increase in resistance with both agents was similar in blood and dextran-perfused lung lobes, hence interaction with formed elements contribute little, if anything, to these responses.

Animals↗
PubMed1975

Polyglycolic acid suture in strabismus surgery.

Polyglycolic acid, synthetic, absorbable braided suture was compared to gut with respect to handling, strength, and tissue reaction in 70 strabismus procedures. This new suture material produced less tissue reaction than gut and had handling characteristics that were similar to silk. It can be used in smaller sizes than gut because of its greater strength and firm knot. Polyglycolic acid suture appears to be a useful addition to ophthalmic suture materials.

Absorption↗
PubMed1975

Effects of indomethacin on venoconstrictor responses to bradykinin and norepinephrine.

In order to determine whether the venoconstrictor response to BK was dependent on prostaglandin (PG) synthesis, effects of indomethacin (INDO) on responses to bradykinin (BK) and norepinephrine (NE) were studied in canine lateral saphenous vein. Cumlative dose-response curves (10-9-10-6M BK or NE) were done in the presence and absence of INDO (10-6M). In the presence of INDO, responses to BK were markedly enhanced while responses to NE were unchanged. After prolonged periods in the bath, responses to BK were enhanced in control strips while responses of strips which had been treated with INDO were depressed. These results suggest that BK does not normally cause venoconstriction by stimulating synthesis of a venoconstrictor PG and that the increase in response to BK after prolonged periods in the bath may be related to changes in PG synthesis.

Animals↗
PubMed1975

Venous smooth muscle in hypertension. Enhanced contractility of portal veins from spontaneously hypertensive rats.

In isolated bath studies smooth muscle from the rat portal vein was evaluated for its reactivity and contractility, and the whole vessel wall was evaluated for its extensibility. Smooth muscle from the spontaneously hypertensive rat (SHR) had the following characteristics when compared with that from normotensive controls: (1) Spontaneous phasic contractions were more frequent and developed more tension; (2) threshold concentrations for responses to prostaglandins A-2 and B-2 were lower, but those for responses to epinephrine, norepinephrine, KCl, BaCl-2, and SrCl-2 were similar; (3) high concentrations of calcium had a less depressant action on the responses to the prostaglandins but not on the responses to the other agonists; (4) maximal contractile tensions to all agonists were greater; and (5) passive extensibility was less. These differences, because they are in the venous system, cannot be secondary to the increase in wall stress of arterial hypertension. The decreased passive extensibility in this vein in SHR creates a stiffer framework on which the active contractile process is able to develop greater tension. If this increase in active tension is generalized to all veins, it could be responsible for a decrease in venous capacity which increases the rate of venous return and, hence, increases cardiac output.

Animals↗
PubMed1975

Enhancement of neural and thermal vasoconstriction by prostaglandin B1.

The vascular effects of prostaglandin B1 (PGB1) were studied during constant-flow perfusion of the canine hindpaw. The effects of PGB1 (50-200 ng/kg/min ia) on systemic and hindpaw perfusion pressures and on responses to local cooling (4 degrees C for 90 sec) and local heating (45 degrees C for 60 sec) were measured in 15 dogs. PGB1 (50-100 ng/kg/min) decreased perfusion pressure without any significant effect on systemic arterial pressure. Higher concentrations of PGB1 (200 ng/kg/min) elevated perfusion pressure to control values. The pressor responses to local cooling were increased from 11 to 32 mmHg while the dilator responses to local heating and nitroglycerin were reduced during infusions of PGB1. PGB1 also enhanced the pressor responses to norepinephrine or tyramine. These findings support the conclusions that (1) low concentrations of prostaglandin B1 enhance neurotransmitter release with minimal effects on vascular smooth muscle cells and (2) these effects are not secondary to increased perfusion pressures or vascular wall stresses since infusions of PGB1 resulted in vasodilation.

Animals↗
PubMed1975

Interaction of prostaglandin A2 and prostaglandin B2 on vascular smooth muscle tone, vascular reactivity and electrolyte transport.

The effects of prostaglandin A2 (PGA2) and prostaglandin B2 (PGB2) on vascular smooth muscle tone, electrolyte movements and responses to vasoactive stimuli were evaluated with superfused canine tibial arteries. PGA2 and PGB2 constricted superfused tibial arteries. PGB2 was 10.7 (8.3-14.1) times more potent as a constrictor than PGA2. PGA2 and PGB2-induced vasoconstriction was associated with a decrease in 22Na efflux and a tendency toward an increase in cellular sodium (expressed as micromoles per gram of wet weight). These prostaglandins also decreased the total potassium content of tibial arteries. 45Ca exchange was enhanced by PGA2 and PGB2. The time course of PG-induced increases in 45Ca efflux was similar to the temporal increase in force produced by PGA2 and PGB2. The duration of the contractile response to barium chloride was greatly prolonged during superfusion with both PGA2 and PGB2. These effects were probably not mediated by PG-induced alterations in the resting membrane potential of tibial arteries since presumed depolarization by both high potassium and zero-potassium physiologic saline solutions did not mimic the effects of these prostaglandins on vascular smooth muscle tone or responses to barium chloride. These data suggest that PGA2 and PGB2 may increase tone of vascular smooth muscle by inhibition of those processes involved in sequestration of calcium ion, i.e., the relaxation process, rather than acting on the contractile process.

Animals↗
PubMed1975

Effects of prostaglandins B2 and B1 on the pulmonary circulation in the intact dog.

The effects of prostaglandins (PG) B2 and B1 on the pulmonary circulation were studied in the intact spontaneously breathing dog under conditions of controlled blood flow using right heart and transseptal catheterization techniques to isolate and perfuse the left lower lung lobe. Infusion of PGB2 and PGB1 into the left lower lung lobe increased lobar arterial and lobar venous pressure but had no significant effect on left atrial pressure. PGB2 and PGB1 increased pressure gradients between the lobar artery and lobar small vein and between the lobar small vein and the left atrium. PGB2 and PGB1 increased isometric tension in isolated helical segments of lobar vein (3-5 mm diameter) but had little or no effect on lobar arterial segments of the same size. These results indicate that in the intact dog prostaglandins of the B series increase pulmonary vascular resistance by constricting lobar veins and to a lesser extent vessels upstream to lobar small veins, presumably small lobar arteries. PGB2 and PGB1 both produced large increases in pulmonary vascular resistance in the dog with PGB2 being about 10 times as potent as PGB1. It is concluded that PGB2 is one of the most potent pressor substances in the canine pulmonary vascular bed.

Animals↗