The cloning and nucleotide sequence of cDNA for an amplified glutamine synthetase gene from the Chinese hamster

The nucleotide sequence for a glutamine synthetase (GS) mRNA from gene-amplified Chinese hamster (CHO) cells was determined from recombinant cDNA clones obtained from both pBR322 and lambda gt10 libraries and by primer extension. The sequence obtained contains about 1400 bp corresponding to a minor species of mRNA terminated by a poly A sequence. The mRNA contains 146 nucleotides of 5'-noncoding region, 1119 bp of coding sequence, and 108 bp of 3'-noncoding sequence with a 32 bp poly(A) tail. The polyadenylation site used shows little homology with efficient polyadenylation sites, but has considerable complementarity with U4 RNA. The predicted amino acid sequence, starting from an initiation codon with the preferred sequence surrounding it, indicates that Chinese hamster GS has high homology with published bovine brain GS peptides and enabled an ordering of these peptides. There is homology between the mammalian GS enzymes and glutamine synthetases obtained from plants and cyanobacteria but no obvious homology between the CHO cell GS sequence and that of other ATP hydrolysing enzymes.

Hydrolysis of leucine enkephalin in the nasal cavity of the rat--a possible factor in the low bioavailability of nasally administered peptides

In order to investigate the utility of intranasal administration of peptides for systemic medication, the nasal absorption of the model peptide, leucine enkephalin (Tyr-Gly-Gly-Phe-Leu), was studied in the rat. At a concentration of 60 micrograms/ml in Ringer's buffer the pentapeptide was found to undergo, extensive hydrolysis in the nasal cavity. The hydrolysis rather than the polarity of the pentapeptide appears responsible for limiting the nasal absorption of this model compound. In the presence of dipeptides, the hydrolysis of leucine enkephalin was significantly inhibited. These results suggest that the nasal administration of peptides may become an important route for drug administration provided that the peptidases in the nasal mucosa can be transiently inhibited via coadministration of pharmacologically inactive peptidase substrates.

Mechanism of nasal absorption of drugs. II: Absorption of L-tyrosine and the effect of structural modification on its absorption

The nasal absorption of L-tyrosine and the effect of structural modification on that absorption have been studied using an in-situ experimental technique. The extent of nasal absorption of the amino acid was found to be the same at pH values of 4.0 and 7.4 but dependent on concentration in the range of 2.8 X 10(-4)-2.2 X 10(-3) M. O-Acyl-L-tyrosine esters, although possessing higher octanol-water (pH 7.4) partition coefficients, have the same rate of nasal absorption as the parent amino acid. N-Acetyl-L-tyrosine, on the other hand, was found to have both partition coefficient and nasal absorption rate similar to those of L-tyrosine. Esterification of the carboxyl moiety of L-tyrosine results in derivatives that hydrolyze in the in-situ perfusion medium generating the original amino acid. The rate of nasal absorption of these derivatives was, therefore, determined from an overall disappearance rate which accounted for the rate of hydrolysis to L-tyrosine. These carboxylic esters were absorbed 4 to 10 times faster than L-tyrosine. Although the carboxylic esters of L-tyrosine possess higher octanol-water partition coefficients than the parent amino acid, the differences in the rates of nasal absorption could not be attributed solely to partition coefficient. The enhancement in the rate of absorption observed for these esters was attributed instead to the absence of the negative charge on the carboxylate moiety. It is a result of this negative charge that the rates of nasal absorption of L-tyrosine, O-acyl-L-tyrosine esters and N-acetyl-L-tyrosine are similar, despite significant differences in their partition coefficients.

Mechanism of nasal absorption of drugs I: Physicochemical parameters influencing the rate of in situ nasal absorption of drugs in rats

The effect of rate of perfusion, volume, pH of the perfusate, and partition coefficient of the drug on the rate of in situ nasal absorption in rats was examined. The studies showed that the rate constant for the nasal absorption of phenobarbital was independent of the rate of perfusion above a value of 2 mL/min. The nasal absorption of benzoic acid was found to depend on the pH of the perfusate with the benzoate anion being absorbed at a rate one-fourth of that of benzoic acid. The effect of lipid solubility on the extent of nasal absorption was studied using a series of barbiturates. The rate and extent of absorption was found to be dependent on the chloroform-water partition coefficient of the barbiturate. The effect of the volume of the perfusate on the absorption rate constant of phenobarbital, phenol red, tyrosine, and propranolol was studied. The data obtained showed that a linear relationship existed between the rate constants of absorption and the reciprocal of the volume of the perfusate. Using this in situ relationship it was possible to predict in vivo absorption rate constants for propranolol and L-tyrosine when volumes of 0.1 mL were administered. The calculated values for these compounds were found to be close to those determined in in vivo experiments. This indicates that the in situ technique can be used to predict in vivo absorption rate constants.

Review on correlation between pharmacologic response and drug disposition

It is generally accepted that there is some type of correlation between the amount of drug in the body, or the concentration at the target site, and the pharmacologic or clinical response. This assumption becomes even more important with the increasing use of blood level measurement in monitoring of drug therapy. Whereas much information is available on the pharmacokinetics of drugs, few studies are concerned with the establishment of a correlation between disposition and response. The purpose of this review is to summarize the attempts made in this regard. Only those drugs for which a pharmacokinetic-pharmacodynamic relationship can be demonstrated are candidates for optimization of drug therapy through drug level monitoring and pharmacokinetic dosage regimen design.

Antibody and complement-mediated cytotoxicity for bovine parainfluenza-3 virus-infected cells

An antibody-complement-mediated cytotoxicity assay was employed to determine whether susceptible host cells infected with bovine parainfluenza-3 virus could be destroyed by the humoral immune mechanism. The cytotoxicity assay yielded 21.5% to 76.9% specific release of 51Cr with sera collected from calves 28 days after inoculation with the virus. A multiplicity of infection of 5, a postinfection period of 2 days, an antibody dilution of 1:10, and an incubation period of 12 hours with antibody and complement were found to be optimal for this assay.

Is there a urodynamic equivalence to anterior urethra in the male?

To evaluate the role of the anterior urethra in the male in micturition dynamics, 9 patients with urethral strictures who were undergoing a two-stage Turner-Warwick urethroplasty were evaluated with flow and pressure flow measurements, pre- and post-second-stage urethroplasty. Any decrease in flow or increase in resistance after closure would suggest an anterior "urethral effect." None was found, indicating that the anterior urethra in the male functions as an inert conduit.

Solubility behavior of phenolic compounds in hexane-ethyl acetate, hexane-ethyl myristate, and hexane-ethyl pivalate cosolvent systems

Interactions of phenolic compounds 4-hexylresorcinol and 3,4-dimethylphenol with esters were studied using hexane-ester cosolvent systems by both phase solubility and partitioning methods. The data obtained by the phase solubility method were variable and could not be analyzed by any mathematical model. The data obtained by the partitioning method, however, strongly suggest that 4-hexylresorcinol forms 1:1 and 1:2 complexes with the esters in hexane, while 3,4-dimethylphenol forms only 1:1 complexes with the same esters.

Effect of complex formation between 4-hexylresorcinol and ethyl myristate on release rate of 4-hexylresorcinol from petrolatum base

The effect of ethyl myristate on the release rate of 4-hexylresorcinol from petrolatum base was studied at pH 7.4 and 37 degrees. 4-Hexylresorcinol was analyzed spectrophotometrically at 278 nm. The release rate of hexylresorcinol from the ointments was directly proportional to the square root of time and depended on the percentage of ethyl myristate in the ointment base. For 0, 0.5, 1, 3, and 5% of ethyl myristate, the release rates were 29.6, 35.4, 38.3, 55.7, and 70.0 micrograms/hr1/2/cm2, respectively. The solubility of hexylresorcinol in the petrolatum base was determined as a function of ethyl myristate using partitioning techniques. The enhancement in hexylresorcinol solubility was rationalized on the basis of 1:1 and 1:2 complexes between hexylresorcinol and ethyl myristate. The complexation constants of these complexes were estimated to be 10 M-1 and 206.1 M-2, respectively. The diffusion coefficient of hexylresorcinol in the petrolatum base was estimated to be 1.31 x 10(-8) cm2/sec.

Blastogenic response of swine lymphocytes in whole blood, purified blood, spleen cell, and lymph node cell cultures with concanavalin A and phytohemagglutinin

Microcultures of swine whole blood, purified blood lymphocytes (PBL), spleen cells, and lymph node (LN) cells were tested for stimulation by concanavalin A (conA) and phytohemagglutinin (PHA). A cell concentration of 2 x 10(6)/ml and a 1:20 dilution of whole blood were needed for optimal stimulation of conA and PHA. Optimal stimulation of whole blood lymphocytes (WBL) and LN cells was obtained by 20 micrograms of conA/ml, but 10 micrograms/ml of this mitogen was adequate for spleen cells. The PBL and LN cells were optimally stimulated by 20 microliters of PHA/ml, but 80 microliters and 40 microliters/ml of this mitogen were required for stimulating the whole blood and spleen cells, respectively. Four days' incubation was needed for maximal blastogenesis of WBL with conA. This could be achieved after 3 days' incubation with PBL and spleen and LN cells. Whole blood and spleen cells were stimulated by PHA after 3 days' incubation, but PBL and LN cells required 4 days' incubation. Reproducibility, sensitivity, and comparison of various cultures were discussed.

First-pass metabolism of ethinyl estradiol in dogs and rats

The contraceptive steroid ethinyl estradiol was extensively metabolized when given orally in solution to dogs. It was thought at first that metabolism occurred exclusively in the liver. However, use of standard equations to predict the oral bioavailability of drugs known to be metabolized by hepatic first pass resulted in significantly higher values than those obtained experimentally. To rationalize the data and to determine whether ethinyl estradiol also is metabolized in the gut wall during absorption, metabolism in rats was studied. The drug was administered in solution intraduodenally, intraportally, and intravenously as a bolus by first-order infusion. The results indicate that, in rats, 40% of the drug is metabolized by the gut wall and 79% of the drug in the portal blood is metabolized by the liver intraduodenal administration.

Nasal absorption of propranolol from different dosage forms by rats and dogs

The blood levels of propranolol in rats and dogs were compared after the administration of nasal, intravenous, and oral solutions. The results indicate that the blood drug levels after nasal and intravenous administration were identical, but the oral administration resulted in considerably lower blood levels. Sustained-release formulations of the drug also were administered nasally and resulted in low initial but prolonged blood levels. The bioavailability of the sustained-release formulation was identical to that of the intravenous administration.

Sensitive method for determination of ethinyl estradiol in presence of norethindrone

A sensitive spectrophotofluorometric procedure for the determination of microamounts of ethinyl estradiol is described. The method is useful for the determination of ethinyl estradiol in the presence of norethindrome and common tablet excipients, especially in dissolution media.

New spectrophotometric determination of inorganic bromide and chloride salts in aqueous solutions

A new method for the determination of inorganic salts of chloride and bromide is described. The method is based on the facts that iodine forms complexes with the anions and that these complexes absorb strongly in the UV region. The molar absorptivities of I2Br- at 265 nm and I2Cl- at 245 nm were calculated to be 3.27 X 10(4) and 2.3 X 10(4) M-1 cm-1, respectively.

Kinetics and mechanism of hydrolysis of 1-(2'-acetoxybenzoyl)-2-deoxy-alpha-D-glucopyranose, a novel aspirin prodrug

The formation rate of aspirin from the prodrug was determined as a function of the pH, temperature, and dielectric constant of the solvent spectrophotometrically and was confirmed by high-pressure liquid chromatography. Aspirin formation was first order with respect to the prodrug and zero order with respect to the hydroxide-ion concentrations. The hydrolysis rate was independent of buffer concentration but very sensitive to the dielectric constant of the solvents. The half-life for the formation of aspirin at 37 degrees was 7 min. The activation energy for the hydrolysis was 23.7 kcal/mole. The results suggest that the hydrolysis of the prodrug to aspirin proceeds by an SN1-type mechanism.

Cell mediated immunity to bovine rhinovirus type 1 in calves

Calves experimentally infected with bovine rhinovirus type 1 developed a mild respiratory disease and exhibited a cell mediated immune (CMI) response, as determined by leukocyte migration inhibition (LMI) and lymphocyte blastogenesis tests. The CMI response to the virus was detected by day 3 post-inoculation using direct and indirect LMI tests. It persisted through day 28, with maximal responses occurring between days 4 and 14. Measurement of cellular immunity by blast transformation, however, was not evidenced until day 12. The humoral antibody response was minimal with serum neutralizing titers ranging from 1:4 to 1:16 and this response was not evident until 3 weeks after inoculation.

Effect of hydroxyl group substituents on pyran ring on hydrolysis rate of benzoates: 2-tetrahydropyranyl benzoate

The hydrolysis of 2-tetrahydropyranyl benzoate was followed spectrophotometrically at 240 nm and was first order with respect to the compound, independent of pH, and very sensitivie to solvent polarity and had an isotope effect (kD2O/kH2O) near unity. The pH-independent hydrolysis rate was about 1 X 10(6) times faster than that of the corresponding glucosly benzoate. The results suggest that the presence of hydroxyl groups on the pyran ring has tremendous effect on the hydrolysis rate of these compounds.

Prodrug approaches to enhancement of physicochemical properties of drugs IX: acetaminophen prodrug

The synthesis, hydrolysis rate, and bioavailability of 1-(p-acetaminophenoxy)-1-ethoxyethane, an acetaminophen prodrug, are described. The prodrug is less soluble than acetaminophen and stable at neutral pH. However, in an acidic environment, the compound cleaves rapidly, generating acetaminophen. When both the prodrug and acetaminophen were administered to dogs in equivalent amounts, the blood acetaminophen levels were comparable.

Precautionary note for use of bisulfite in pharmaceutical formulations

The effect of sodium bisulfite on aspirin hydrolysis was studied at 40 degrees in the pH range of 6.5-7.5. Significant catalytic activity by the sulfite ion was observed. Second-order rate constants were calculated for this catalysis and compared to other buffer species. The sulfite ion was a much more efficient catalyst than acetate, phosphate, or carbonate.

Prodrug approaches to enhancement of physicochemical properties of drugs IV: novel epinephrine prodrug

The synthesis and characterization of a prodrug that appears to overcome the problem of inefficient absorption of epinephrine through the lipoidal membranes of the eye are described. The enzymatic rate of regeneration of epinephrine from the prodrug was determined using a rabbit eye homogenate, rabbit plasma, and human plasma. The prodrug had no activity of its own when tested against a guinea pig smooth muscle preparation. Upon enzymatic regeneration of epinephrine from the prodrug, however, the reaction mixture exhibited alpha-adrenergic activity equivalent to that of epinephrine when tested in the same preparation.

Sugar, organic acid, phenolic acid and plant growth regulator content of extracts of honeydew of the aphid Myzus persicae and of its host plant, Raphanus sativus

The honeydew of Myzus persicae feeding on radish seedlings contains glucose, fructose, trehalose, melezitose and sucrose, of which glucose and fructose are present in radish seedlings. In addition, the honeydew contains eight organic acids, of which seven are present in uninfested seedlings and six are present in infested radish seedlings: of the eighteen phenolic acids in the honeydew, five are present in uninfested radish seedlings. Auxins, gibberellins, growth inhibitors and cytokinins are present in the honeydew. The presence of carbonate and bicarbonate previously recorded in honeydew of M. persicae could not be confirmed, but ammonia is present in fresh honeydew and accounts for its high pH.