Biomedical subjects
Publications and source records attributed to A Johns.
An inexpensive filtration manifold for radioligand binding studies is described. The manifold can be for any number of filter units, is inexpensive to produce, and is easy to use. The filter units are produced from Swinnex 25-mm syringe filter units. The radioligand binding curve for [3H] QNB to guinea pig ventricle membrane fraction shows that the unit produces consistent results.
The affinities of a number of alpha- and beta-adrenergic binding sites and muscarinic cholinergic binding sites in rabbit urethra and bladder have been determined, using specific radioligand receptor binding assays. There was a greater density of beta-binding sites than alpha-binding sites in the bladder, while, in the urethra, there was a greater density of alpha-binding sites than beta-binding sites. The number of alpha-binding sites was fourfold greater in the urethra, whereas there were fewer beta-binding sites in the urethra. There were fewer muscarinic binding sites in the urethra than in the bladder. The dissociation constant for [3H]dihydroalprenolol at the beta-binding site was 6.4 nM, for [3H]dihydroergocryptine at the alpha-binding site was 2.11 nM, and for 3H-labelled l-quinuclidinyl benzilate at the muscarinic binding site was 0.22 nM.
The furosemide-sensitive uptake of thallium represents approximately equal to 50% of the total uptake of thallium by rabbit uterus and requires Cl- and Na+. The furosemide-sensitive uptake of thallium is stimulated by other ions at low concentrations with the rank order Li+ greater than Tl+ greater than K+ = Rb+ greater than Cs+ and is inhibited by these ions at high concentrations with the rank order Tl+ greater than K+ = Rb+ greater than Cs+ greater than Li+, suggesting multiple cation binding sites on the carrier. Uptake of 36Cl- is inhibited by furosemide in the presence of ouabain. Thallium efflux and 36Cl efflux in the presence of ouabain is inhibited by furosemide. The chloride concentration regulates the proportion of thallium uptake that is ouabain sensitive and furosemide sensitive without altering the total uptake. It is suggested that the furosemide-sensitive uptake of thallium reflects a Na+-Cl- -K+ exchange system that could be classified as a cotransport or countertransport of any two of these ions and also could be the smooth muscle chloride pump.
Hamster vas deferens responds to nerve stimulation with a biphasic contraction which is completely blocked by guanethidine and tetrodotoxin. The second component of the contraction is inhibited by phentolamine, whereas the initial component is slightly potentiated by phentolamine. When hamsters are subjected to short photoperiods or castration, the vas deferens becomes supersensitive to nerve stimulation and shows spontaneous mechanical activity. The supersensitivity is not due to increased postsynaptic adrenergic supersensitivity, decreased neuronal uptake of catecholamine, decreased presynaptic feedback by prostaglandin or adrenergic agonist. The supersensitivity is still demonstrable in the presence of 4-aminopyridine, suggesting that the release of transmitter is also not different in animals kept in short photoperiods. The activity of the Na+/K+ pump is increased in vasa deferentia from hamsters kept in short photoperiods and the postsynaptic response to the ATP receptor agonist, diadenosine pentaphosphate, is also enhanced. It is suggested that the supersensitivity induced in the hamster vas deferens by short photoperiod is caused by testosterone withdrawal and is due to increased responsiveness to ATP, which could be acting as a cotransmitter in this tissue.
A simple method of preparing single cell suspensions for radioligand binding studies is described. The method involves incubating tissues in the presence of collagenase and elastase for 90 min in physiological solution with 1 mM calcium chloride and the mechanical disruption of the tissue by pipetting. The tissues examined were atria, ventricle, bladder, uterus, and taenia coli removed from mature guinea pigs. Viability of the cells by trypan blue exclusion showed 60-88% viable cells and receptor binding studies using (3H]-1-quinuclidinyl benzilate (QNB) yield KD values of approximately equal to 0.1 nM. The receptor numbers for each tissue were (receptors/cell): atria, 5700; ventricle, 11,000; uterus, 31,000; bladder, 44,000; taenia coli, 68,000.
The water content, extracellular space, intracellular water, potassium, sodium and chloride content of oviduct and uterus removed from rabbits in estrus and 24 and 72 h following hCG injection have been determined. Following ovulation, there was an increase in water content of the region of the oviduct corresponding to the ampullary -isthmic junction which, at 24 h, is probably due to increased intracellular water. In the ampullary-isthmic junction, ovulation decreases the potassium content and, at 24 h in the isthmic region of the oviduct, chloride is reduced. The water and ionic content of mucosa and smooth muscle cells has been calculated and mucosa cells have greater intracellular water and chloride and sodium content and less potassium and extracellular space than the smooth muscle cells of the oviduct. The significance of the changes in ionic and water content is discussed.
The contraction and electrical conduction velocity of the longitudinal and circular muscle of the oviduct from rabbits in estrus, 24 or 72 h following administration of human chorionic gonadotropin (hCG) or 14 days following castration have been compared. Two populations of conduction and contraction velocities were identified, with the faster velocity being associated with the longitudinal muscle. There was a large overlap between longitudinal and circular contraction, suggesting complex relationships between longitudinal and circular muscle. From the results it appears that during ovum transport the circular velocities increased, with the slowest rates at estrus. The values obtained 72 h following hCG injection most closely resembled those in the castrate group of animals. In the longitudinal orientation, however, the velocities were greater 24 h following hCG injection than at estrus or 72 h following hCG injection, suggesting a complex relationship between both longitudinal and circular muscle of the oviduct following ovulation.
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The effect of longitudinal and circular stretch on the amounts of Prostaglandin F (PGF) and Prostaglandin E (PGE) found in the fluid bathing rabbit oviductal isthmus has been investigated. It was found that the amounts of PGE and PGF measured in the bathing fluid of longitudinally or circularly stretched tissues were negatively correlated to the maturity of the animal. Prostaglandin E increased with time in the tissues under longitudinal and circular tension. Prostaglandin F also increased with time under longitudinal tension but remained fairly constant under circular tension. Increasing the load from 0.5 to 2.0 g had no significant effect on PGE found under longitudinal or circular tension or on PGF found under longitudinal tension. Under circular tension, PGF found increased. Transmural stimulation at 20 Hz increased PGE 8-fold over control values while PGF increased only 1 to 3-fold. It is suggested that distension of the rabbit oviductal isthmus results in increased PGF production, which could be important in ovum transport.
A simple and accurate method for determining total calcium in small tissue samples using aequorin is described. The method involves measuring the calcium-induced luminescence of aequorin with the tritium channel of a liquid scintillation counter. The sensitivity of the method and specificity of the method for calcium have been determined and, theoretically, this method could determine calcium in tissue samples weighing 3 mg or as little as 2 nmol of calcium could be measured.
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The acute effects of cocaine and/or delta 9-tetrahydrocannabinol (THC) were studied in ovariectomized female rats. Intermediate doses of cocaine (10 or 20 mg/kg) caused an increase in serum luteinizing hormone (LH) and a decrease in serum prolactin levels, whereas a higher dose (40 mg/kg) caused a decrease in serum LH. THC (10 mg/kg) attenuated serum LH and prolactin levels. The THC effect on LH was blocked by cocaine. Neither drug alone or in combination affected serum follicle-stimulating hormone levels. The cocaine-induced changes in LH levels were closely paralleled by changes in hypothalamic norepinephrine content, suggesting a neurochemical basis for cocaine's action on LH release.
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1. Rabbit myometrium accumulates Tl in a time-dependent fashion and the majority of the uptake of Tl is ouabain-sensitive. 2. In normal chloride-containing media, the uptake of Tl, though ouabain-sensitive, is less than in chloride-free media and this difference is due to a greater ouabain-insensitive uptake. 3. The ouabain-insensitive uptake in normal chloride-containing media is reduced by furosemide and furosemide also reduces total uptake in this solution. In chloride-free media, however, furosemide is without effect on total or ouabain-sensitive uptake. 4. In chloride-free media, the uptake of Tl against Tl concentration is sigmoidal, suggesting that more than one Tl ion is being transported at a time. 5. Tl was capable of substituting for K in electrogenic Na pumping; it was approximately twice as effective as K and the inhibitory effect of Tl was blocked by ouabain. 6. Tl efflux can be explained by a simple two-compartment model in both normal and chloride-free solutions. 7. The uptake of Tl was inhibited by alkali cations with the order of potency being Tl+ > K+ > Rb+ > Cs+ at 10 mM and Tl+ > K4 = Rb+ > Cs+ at 5 mM ion concentrations. 8. It is concluded that Tl enters the smooth muscle of rabbit uterus by diffusion, active ouabain-sensitive transport and active chloride- and furosemide-sensitive transport.
A case is presented in which pregnancy occurred after jejunoileal bypass for treatment of obesity. The pregnancy was complicated by coagulation defects apparently on the basis of liver damage secondary to the bypass. Pertinent literature is reviewed, and the conclusion is reached that although the majority of patients becoming pregnant after jejunoileal bypass tolerated pregnancy well, hepatic disease may occur as it does in nonpregnant individuals.
The effect of vasoactive intestinal polypeptide (VIP) on the contractile activity of the urinary bladder and taenia coli of the guinea pig has been investigated. In the urinary bladder VIP caused a weak contraction and a small potentiation of the nerve-induced contraction. In the taenia coli VIP caused a small relaxation and had no effect on the nerve-induced relaxation of the preparation. The present experiments provide no evidence that VIP fulfills a role as a neurotransmitter in the urinary bladder or taenia coli, but it could be a modulator of transmitter action in the urinary bladder.