Angiotensin-converting enzyme inhibitory and antihypertensive activities of pivalopril (RHC 3659-(S))

Pivalopril (RHC 3659-(S); (S)-N-cyclopentyl-N-(2-methyl-3-pivaloylthiopropionyl) glycine) is a new compound with a hindered sulfur group that has been compared to captopril for oral angiotensin-converting enzyme (ACE) inhibition in rats and dogs and antihypertensive activity in rats. In separate groups of conscious normotensive rats, pivalopril (0.03-1.0 mg/kg, orally [p.o.]) produced a dose-related antagonism of angiotensin I (AngI)-induced pressor effects. The ED50 for pivalopril and captopril was 0.1 mg/kg. In conscious normotensive dogs, pivalopril (incremental doses of 0.01-1.0 mg/kg, p.o.) produced a dose-related antagonism of AngI pressor effects. The ED50 was 0.17 mg/kg for pivalopril and 0.06 mg/kg for captopril. At equieffective doses the two compounds had similar durations of action. In sodium-deficient, conscious spontaneously hypertensive rats (SHR), pivalopril (1-100 mg/kg, p.o.) produced a dose-related reduction in mean arterial pressure. The potency and duration were similar to those of captopril. In the sodium-replete SHR, 5 days of oral dosing with pivalopril, 100 mg/(kg . day), decreased mean arterial pressure more effectively than captopril, 100 mg/(kg . day). No tolerance developed to the antihypertensive effect of either drug. It is concluded that pivalopril is a potent, orally effective ACE inhibitor and antihypertensive agent.     

Detergent solubilization, purification, and separation of specificities of HLA antigens from a cultured human lymphoblastoid line, RPMI 4265.

HLA antigens have been purified to homogeneity after detergent solubilization from RPMI 4265, a human lymphoblastoid line. The inhibition of cytotoxicity assay for HLA antigen was modified, using preincubation with bovine serum albumin of antigen samples containing detergent to prevent lysis of target cells by detergent. Solubilization was tested with many types of detergents. A polyethyleneglycol oleyl ether nonionic detergent mixture, Brij 99:Brij 97 (2:1) was selected for solubilization, since it selectively solubilized HLA antigens, had a low absorbance at 280 nm and was uncharded. HLA antigens were then purified by Lens culinaris lectin affinity chromatography and Bio-Gel A-5m filtration. The antigen specifity HLA-A2 was separated from specificities HLA-B7,12 by isoelectric focusing. Purified HLA antigens contained a subunit of Mr=44,000 with NH2-terminal glycine, and a subunit of Mr=12,000, beta2-microglobulin, with NH2-terminal isoleucine.     

The contractile basis of amoeboid movement: V. The control of gelation, solation, and contraction in extracts from dictyostelium discoideum

Motile extracts have been prepared from Dictyostelium discoideum by homogenization and differential centrifugation at 4 degrees C in a stabilization solution (60). These extracts gelled on warming to 25 degrees Celsius and contracted in response to micromolar Ca++ or a pH in excess of 7.0. Optimal gelation occurred in a solution containing 2.5 mM ethylene glycol-bis (β-aminoethyl ether)N,N,N',N'-tetraacetate (EGTA), 2.5 mM piperazine-N-N'-bis [2-ethane sulfonic acid] (PIPES), 1 mM MgC1(2), 1 mM ATP, and 20 mM KCI at ph 7.0 (relaxation solution), while micromolar levels of Ca++ inhibited gelation. Conditions that solated the gel elicited contraction of extracts containing myosin. This was true regardless of whether chemical (micromolar Ca++, pH >7.0, cytochalasin B, elevated concentrations of KCI, MgC1(2), and sucrose) or physical (pressure, mechanical stress, and cold) means were used to induce solation. Myosin was definitely required for contraction. During Ca++-or pH-elicited contraction: (a) actin, myosin, and a 95,000-dalton polypeptide were concentrated in the contracted extract; (b) the gelation activity was recovered in the material sqeezed out the contracting extract;(c) electron microscopy demonstrated that the number of free, recognizable F-actin filaments increased; (d) the actomyosin MgATPase activity was stimulated by 4- to 10-fold. In the absense of myosin the Dictyostelium extract did not contract, while gelation proceeded normally. During solation of the gel in the absense of myosin: (a) electron microscopy demonstrated that the number of free, recognizable F- actin filaments increased; (b) solation-dependent contraction of the extract and the Ca++-stimulated MgATPase activity were reconstituted by adding puried Dictyostelium myosin. Actin purified from the Dictyostelium extract did not gel (at 2 mg/ml), while low concentrations of actin (0.7-2 mg/ml) that contained several contaminating components underwent rapid Ca++ regulated gelation. These results indicated : (a) gelation in Dictyostelium extracts involves a specific Ca++-sensitive interaction between actin and several other components; (b) myosin is an absolute requirement for contraction of the extract; (c) actin-myosin interactions capable of producing force for movement are prevented in the gel, while solation of the gel by either physical or chemical means results in the release of F-actin capable of interaction with myosin and subsequent contraction. The effectiveness of physical agents in producting contraction suggests that the regulation of contraction by the gel is structural in nature.     

Distribution of alloantigens on human Fc receptor-bearing lymphocytes: the presence of B cell alloantigens on sIg-positive but not sIg-negative lymphocytes.

Human peripheral blood lymphocyte subpopulations were analyzed for the presence of B cell alloantigens with a microcytotoxicity assay. B cell alloantigens were found exclusively on sIg-positive lymphocytes and were not present on sIg-negative, Fc receptor-bearing lymphocytes or sIg-negative, Fc receptor-negative T lymphocytes.     

Increased striatal acetylcholine after 14 months cis-flupenthixol treatment in rats suggests functional supersensitivity of dopamine receptors

Rats received continuous administration of cis-flupenthixol (0.8-1.2 mg/kg/day) or trans-flupenthixol (0.9-1.2 mg/kg/day) in drinking water for 14 months. The administration of cis-flupenthixol, but not trans-flupenthixol, caused apparent cerebral dopamine receptor supersensitivity. Thus, animals receiving cis-flupenthixol, but not trans-flupenthixol, showed enhanced apo-morphine-induced stereotyped behaviour. Dopamine concentration in striatum was not altered by drug treatment but striatal HVA and DOPAC concentrations were reduced in animals receiving cis-flupenthixol, but not trans-flupenthixol. No consistent change in Bmax of KD for specific striatal 3H-spiperone binding was observed after 14 months drug intake. However, in cis-flupenthixol treated animals a 40% increase in Bmax was observed following 2 weeks drug withdrawal. Continuous cis-flupenthixol intake increased striatal acetylcholine concentrations; trans-flupenthixol was without effect. This suggests the apparent increase in cerebral dopamine receptor supersensitivity caused by continuous long-term cis-flupenthixol administration is of functional importance in the intact animal.