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70 records · Page 4Linked to original sources
PubMed2003

Influence of angiotensin II receptor subtypes of the paraventricular nucleus on the physiological responses induced by angiotensin II injection into the medial septal area.

OBJECTIVE: We determined the effects of losartan and PD 123319 (antagonists of the AT1 and AT2 angiotensin receptors, respectively), and [Sar1, Ala8] ANG II (a relatively peptide antagonist of angiotensin receptors) injected into the paraventricular nucleus (PVN) on water and 3% NaCl intake, and the diuretic, natriuretic, and pressor effects induced by administration of angiotensin II (ANG II) into the medial septal area (MSA) of conscious rats. METHODS: Holtzman rats were used. Animals were anesthetized with tribromoethanol (20 mg) per 100 grams of body weight, ip. A stainless steel guide cannula was implanted into the MSA and PVN. All drugs were injected in 0.5-microl volumes for 10-15 seconds. Seven days after brain surgery, water and 3% NaCl intake, urine and sodium excretion, and arterial blood pressure were measured. RESULTS: Losartan (40 nmol) and [Sar1, Ala8] ANG II (40 nmol) completely eliminated whereas PD 123319 (40 nmol) partially blocked the increase in water and sodium intake and the increase in arterial blood pressure induced by ANG II (10 nmol) injected into the MSA. The PVN administration of PD 123319 and [Sar1, Ala8] ANG II blocked whereas losartan attenuated the diuresis and natriuresis induced by MSA administration of ANG II. CONCLUSION: MSA involvement with PVN on water and sodium homeostasis and arterial pressure modulation utilizing ANGII receptors is suggested.

Angiotensin II↗
PubMed2001

Reliable measurement of mouse intraocular pressure by a servo-null micropipette system.

PURPOSE: To develop a reliable technique for measuring intraocular pressure (IOP) in the mouse. METHODS: An electrophysiologic approach-the servo-null micropipette system (SNMS)-for measuring hydrostatic pressure was adapted for the mouse eye. Fine-tipped (5 microm in diameter) micropipettes were advanced across the cornea with a piezoelectric micromanipulator, and the IOP was continuously monitored for up to 46 minutes. RESULTS: The micropipette tip was visualized in the anterior chamber. With the SNMS, the IOP of black Swiss outbred mice under ketamine anesthesia was 17.8 +/- 0.4 mm Hg, higher than values previously estimated in inbred mouse strains by a larger bore microneedle manometric technique. After withdrawal of the micropipette, a second penetration led to a similar level of IOP. Hypotonic solutions increased and hypertonic solutions decreased IOP. Drugs that decrease inflow (acetazolamide, timolol) or increase outflow facility (pilocarpine, latanoprost) in primates and humans lowered steady state IOP in the mouse. The transient initial increase in IOP produced by pilocarpine reported in other animals was also observed in the mouse. Xylazine-ketamine anesthesia lowered IOP substantially in comparison with systemic anesthesia with either ketamine or tribromoethanol alone. CONCLUSIONS: The SNMS is the first reliable, reproducible method for measuring mouse IOP. The mouse IOP is sensitive not only to drugs known to reduce aqueous humor inflow but also to drugs that increase aqueous humor outflow facility in the eyes of primates and humans. The development of the SNMS is an enabling step in the use of the mouse for glaucoma research, including molecular genetics, molecular pharmacology, and the search for novel antiglaucoma drugs.

Acetazolamide↗
PubMed1990

Zinc-activated alcohols in ternary complexes of liver alcohol dehydrogenase.

Activation parameters for each reaction step in the kinetic mechanism of liver alcohol dehydrogenase have been measured for the oxidation of ethanol and the reduction of acetaldehyde. In the oxidation process, the highest enthalpy of activation, 9.7 kcal/mol, occurs for the turnover of the liver alcohol dehydrogenase-NAD(+)-ethanol ternary complex. To investigate if this enthalpy requirement represents a change in the ionization state of ethanol bound in the ternary complex, inhibition of ethanol oxidation was determined using the following series of small, electronegative alcohols with pKa values ranging from 12.37 to 15.5: 2,2,2-trifluoroethanol, 2,2,2-trichloroethanol, 2,2,2-tribromoethanol, 2,2-dichloroethanol, 2,2-difluoroethanol, propargyl alcohol, 3-hydroxypropionitrile, 2-chloroethanol, 2-iodoethanol, 2-methoxyethanol, ethylene glycol, and methanol. The observed inhibition patterns were analyzed according to several kinetic inhibition models; in each case, the best fit model was used to determine the substrate competitive inhibition constant. A plot of the logarithm of these inhibition constants is shown to be dependent on the pKa values of the inhibiting alcohols with a slope approaching -1, indicating that inhibition is controlled by a proton loss from the alcohol. The observed competitive inhibition behavior, coupled with crystallographic studies depicting a direct ligation of an alcohol oxygen to the catalytic zinc ion, indicates that inhibition is controlled by the formation of a zinc-bound alkoxide. Because the inhibiting alcohols are structurally homologous to ethanol, a relationship between the inhibition constant and the inhibiting alcohol's pKa can be derived to show that the pKa of an alcohol bound in a ternary complex is also dependent on its pKa as a free alcohol. Ternary complex pKa values have been determined for ethanol and the inhibiting alcohols.

Alcohol Dehydrogenase↗
PubMed1964

THE EVALUATION AND MODIFICATION OF A TECHNIQUE FOR COMPARING THE EFFICIENCY OF ANTISEPTICS AGAINST SUBCUTANEOUSLY DEPOSITED BACTERIA IN MICE.

An attempt has been made to study the action of antiseptics on artificial streptococcal ;wounds' in mice by a published technique (Martin, 1959). The results were not in agreement with those of Martin and the possible reasons for this are discussed. Suggestions are made for modifying the original method to increase its scope and precision. The production and treatment of Ps. pyocyanea and Kl. aerogenes ;wounds' in mice is described and discussed.

Ammonium Compounds↗