[An electron microscopic study of retinal development and pathogenesis in mutant CBA/J mice with hereditary retinal degeneration]

Electron microscopic study of the neural retina pathogenesis was carried out on mice CBA/J in comparison with corresponding process in substrain CBA/Ki (Caley et al., 1972). A difference in terms of the pathology development was found between substrains CBA/J and CBA/Ki. It was shown that, in CBA/J, the retinal degeneration begins later than in CBA/Ki. As distinct from the latter, CBA/J proceeds to increase the thickness of outer nuclear and plexiform layers as well as the number of membranous discs of rod outer segments (ROS) between P10 and P12. In the retina of mouse CBA/J, pathologic alterations of the outer nuclear layer and the inner segments of photoreceptors precede the ROS destruction. It was found that the pigment epithelium is capable to phagocytize membranous discs of ROS in mouse CBA/J at P10 and P12. In CBA/J, the mitochondria in inner segments of photoreceptors begin to decay at P10; by P12, the amount of such segments reach 40%. At P12, the number of pycnotic nuclei (6%) in the outer nuclear layer coincides with the number of inner segments with dense degenerative cytoplasm. At P15, the state of retina as evaluated by the extent of far advanced degeneration of the outer nuclear layer is equalized in mice of both substrains. From P10 to P15, macrophages which phagocytize membranous discs of ROS are present in the interphotoreceptor space of CBA/J. The administration of PABA solution (7.5 x 10(-3) mg/g) daily from P1 to P9 or from P1 to P11 and with subsequent fixation at P10 and P12 respectively exerted no effect on the rate of retinal pathogenesis in mouse CBA/J. The causes of revealed differences in the development of retinal pathology between CBA/Ki and CBA/J are discussed as well as the causes of the absence of PABA effect on the retina of mutant mouse CBA/J.

Identification of two zinc metalloendopeptidases in alveolar macrophages of rats, guinea pigs, and human beings

Neutral endopeptidases EC 3.4.24.11 and EC 3.4.24.15, widely distributed zinc metalloendopeptidases, degrade a number of biologically active peptides including substance P, bradykinin, neurotensin, and luteinizing hormone-releasing hormone. In this study we measured EC 3.4.24.11 and EC 3.4.24.15 activity in alveolar macrophages, key inflammatory cells in the lung that produce and respond to a large number of bioactive substances including chemotactic peptides, with the substrates glutaryl-ala-ala-phe-2-naphthylamide and tertiary butoxycarbonyl-phe-ala-ala-phe-paraaminobenzoate, respectively. We found that specific activity of EC 3.4.24.15, defined as activity inhibited with N-[(1RS)-carboxy-3-phenylpropyl]-ala-ala-phe-paraaminobenzoate+ ++, was significantly higher (p < 0.001) in cells from Sprague-Dawley rats (485 +/- 123 nmol/mg protein.hr) than in cells from Hartley guinea pigs (138 +/- 94 nmol/mg protein.hr), healthy human male smokers (121 +/- 73 nmol/mg protein.hr) and healthy human male nonsmokers (94 +/- 12). In contrast, activity of EC 3.4.24.11, defined as activity inhibited with N-[(1RS)-carboxy-3-phenylpropyl]-phe-paraaminobenzoate, was significantly higher (p < 0.001) in cells from human smokers (689 +/- 167 nmol/mg protein.hr) and nonsmokers (762 +/- 136 nmol/mg protein.hr) than in cells from rats (52 +/- 12 nmol/mg protein.hr) and guinea pigs (34 +/- 14 nmol/mg protein.hr). An additional activity in alveolar macrophages toward tertiary butorycarbonyl-phe-ala-ala-phe-paraaminobenzoate was inhibited with L-3-carboxy-trans-2,3-epoxypropionyl-leucylamido-(4-guanido) butane, a specific inhibitor of cysteine proteinases, a finding of interest because in general enzymes in this class show little activity at neutral pH.(ABSTRACT TRUNCATED AT 250 WORDS)

The cytotoxicity, DNA crosslinking ability and DNA sequence selectivity of the aniline mustards melphalan, chlorambucil and 4-[bis(2-chloroethyl)amino] benzoic acid

Three aniline derivatives melphalan (L-PAM), chlorambucil (CHL) and 4-[bis(2-chloroethyl)amino] benzoic acid (BAM) have been compared on the basis of their in vitro cytotoxicities, DNA interstrand crosslinking ability and DNA sequence selectivity. Cytotoxicity was assessed in the human colonic adenocarcinoma LS174T and leukaemic K562 cell lines using the sulpho-rhodamine B and tetrazolium dye reduction assays. The order of cytotoxicities was L-PAM greater than CHL greater than BAM in both cell lines with K562 being less sensitive than LS174T. This was different from the order CHL greater than L-PAM greater than BAM which would be predicted from simple chemical reactivity or rate of hydrolysis, parameters which have been used previously as indicators of biological potency for aromatic nitrogen mustards. DNA interstrand crosslinking in cells as determined by alkaline elution showed a correlation with IC50 values. The ranking order of activity was further predicted by the ability of the agents to produce interstrand crosslinks in isolated DNA. The extent of guanine N-7 alkylation, assessed using a modified DNA sequencing technique, mirrored cytotoxicity and crosslinking ability, but at equivalent levels of alkylation there was no significant difference in DNA sequence selectivity. These data demonstrates that simple chemical reactivity or hydrolysis rate is not a good indicator of DNA reactivity or cytotoxicity for a number of aniline mustards, whereas DNA interstrand crosslinking ability either measured directly in cells or in isolated DNA, gives a good indication of biological activity.

A comparison of morphoea and lichen sclerosus et atrophicus in vitro: the effects of para-aminobenzoate on skin fibroblasts

To study the effects of para-aminobenzoate on the dermis, fibroblast cell lines derived from lesions of lichen sclerosus et atrophicus, from morphoea and from normal skin were incubated with Potaba in vitro. Monolayer cultures containing Potaba showed a dose-dependent inhibition of proliferation beginning at 1,000 micrograms/ml with total inhibition at 10,000 micrograms/ml. Mean ID50 values for the three groups were not significantly different. There was a similar dose dependent inhibition of glycosaminoglycan secretion in all 3 groups, except at 10,000 micrograms/ml where secretion by lichen sclerosus et atrophicus and morphoea fibroblasts was significantly more inhibited than normal lines. Inhibition of the glycosaminoglycan secretion at 10-1,000 micrograms/ml was a direct effect of the drug rather than an indirect effect of changes in cell density, and lichen sclerosus et atrophicus fibroblasts produced about 40% more GAG than the morphoea or normal lines growing at similar densities. Collagen synthesis was increased in both lichen sclerosus et atrophicus and morphoea cell lines, with increased non-collagenous protein in morphoea lines. These results confirm that there are differences between lichen sclerosus et atrophicus and morphoea, and suggest glycosaminoglycan secretion as a possible target for the therapeutic action of Potaba.

Inhibition of gramicidin channel activity by local anesthetics

Ondrias et al. ((1986) Stud. Biophys. 115, 17-22) found that dibucaine, butacaine, and tetracaine reduce the conductance of membranes containing multiple (greater than 10(6)) gramicidin channels. Similar experiments with local anesthetics (LA's) added to the bath while gently stirring showed that the inhibition developed slowly over a time course of 5-10 min. We developed a many (10-20) channel membrane technique which demonstrated that when LA's were added to the bath and the membrane was repeatedly broken and reformed, the channel occurrence frequency declined promptly. In standard single-channel membrane experiments at lower gramicidin densities, the mean single channel conductance and lifetime distributions with LA's present in the bath did not differ from the controls. The predominant channel conductance amplitude was lower by 9.1% than those of controls, but channel amplitude distributions were also modified so that the net reduction in overall population channel conductance was only about 2.0%. Channel currents showed no evidence of flicker blocks. The lifetime histograms of control and LA-exposed channel populations were both satisfactorily fit by a single-exponential function with the same mean. Thus, inhibition is due primarily to a reduction in the frequency of occurrence of conducting channels, implying a reduced concentration of active monomers in the membrane.

Inhibition of mutagenesis by p-aminobenzoic acid as a nitrite scavenger

Nitrite treatment enhances the direct-acting mutagenicity of various foodstuffs (e.g., chicken, bloater, the soybean flour 'kinako', and Ban-Ban-Chi sauce) on Salmonella typhimurium TA100. p-Aminobenzoic acid (PABA) and glutathione (GSH) reduced this mutagenicity; on the other hand, thioproline (TPRO) increased it. PABA seemed more effective than TPRO in scavenging nitrite ion. In analysis of the reactions of PABA and sodium nitrite under acidic conditions (pH 3.0), p-hydroxybenzoic acid (PHBA) was identified as a major reaction product. The reaction seems to involve two steps, diazotization and diazonium substitution. PHBA was not mutagenic to four strains (TA97, TA98, TA100 and TA102) of S. typhimurium with or without S9 mix.

Protective effect of two sunscreens against lethal and genotoxic effects of UVB in V79 Chinese hamster cells and Saccharomyces cerevisiae strains XV185-14C and D5

Effects of p-aminobenzoic acid (PABA) and of 4-[(2-oxo-3-bornylidene)methyl]-phenyl trimethylammonium methylsulfate (OMM), two components used in sunscreen formulations, on the mutagenicity of UVB irradiation are compared in three genetic assay systems. A haploid strain of Saccharomyces cerevisiae XV185-14C was used to measure reverse mutations at three loci. The diploid strain D5 of Saccharomyces cerevisiae was used to screen for reciprocal mitotic recombination. The induction of forward mutations was measured in Chinese hamster V79 cells. Our results indicate that UVB irradiation induced HGPRT- mutants in V79 cells, reverse mutations in Saccharomyces cerevisiae strain XV185-14C, and mitotic crossing over and other genetic alterations in Saccharomyces cerevisiae strain D5. V79 Chinese hamster lung cells were the most sensitive to UVB irradiation, followed by Saccharomyces cerevisiae haploid strain XV185-14C and the diploid strain D5. PABA and OMM were both capable of protecting all three types of cells from UVB irradiation regarding both lethality and induction of various types of genetic alterations. At higher concentrations (above 10(-5) M), OMM was more effective in its photoprotective effect toward UVB irradiation than PABA.

Toxoplasma gondii: characterization of a mutant resistant to sulfonamides

Sulfadiazine was a potent inhibitor of the in vitro growth of Toxoplasma gondii, although it had little effect during the first 24 hr of treatment. A mutant parasite (R-SulR-5) with a 300-fold increase in sulfadiazine resistance was selected by a combination of chemical mutagenesis and growth in gradually increased sulfadiazine concentrations. This mutant was completely cross-resistant to several other sulfonamides and to dapsone. The same concentration of p-aminobenzoic acid reversed the sulfadiazine inhibition of both mutant and wild-type parasites even though much higher concentrations of sulfadiazine were used to inhibit the mutant. Dihydropteroate synthase, a sulfonamide-sensitive enzyme in the pathway leading to dihydrofolic acid, had similar activities in wild-type and R-SulR-5 parasites. However, the mutant enzyme was 40-fold more resistant to sulfadiazine and had higher apparent Kms for both substrates, p-aminobenzoic acid and dihydropteridine pyrophosphate. The mutant was slightly less active than the wild type in the uptake of sulfadiazine.

SDZ 205-557, a selective, surmountable antagonist for 5-HT4 receptors in the isolated guinea pig ileum

A selective antagonist for the recently characterized 5-HT4 receptor is lacking. The only surmountable antagonist available, ICS 205-930, is a weak antagonist and is far more potent at 5-HT3-than at 5-HT4 receptors. In this paper, SDZ 205-557 (2-methoxy-4-amino-5-chloro-benzoic acid 2-(diethylamino) ethyl ester) is characterized as the first potent, selective and surmountable antagonist at 5-HT4 receptors in the isolated guinea pig ileum. SDZ 205-557 was investigated in the non-stimulated and in the field-stimulated guinea pig ileum longitudinal muscle preparation for its affinity for 5-HT4-, 5-HT3-, muscarine-, nicotine- and histamine H1 receptors. The affinity for 5-HT1-, 5-HT2-, alpha 1-, alpha 2- and opiate (mu) receptors was determined by binding assays. SDZ 205-557 was devoid of substantial affinity (pKD values below 5.6) for all receptors investigated except for 5-HT3- and 5-HT4 receptors. At these two receptors, SDZ 205-557 acted as an antagonist without measurable intrinsic activity. At the 5-HT4 receptors of the non-stimulated guinea pig ileum, responses to 5-HT and 5-methoxytryptamine were antagonized by SDZ 205-557 with identical pA2 values of 7.4. The effect of renzapride was also blocked with no significant change in the maximum response; Schild analysis, however, revealed that the interaction was not competitive with an "apparent" pA2 value of 7.6. A pA2 of 6.8 was obtained using zacopride as a contractile agent; this value differed significantly from 7.4, the value obtained for 5-HT and 5-methoxytryptamine.(ABSTRACT TRUNCATED AT 250 WORDS)

Diazald, a newly recognized antimicrobial agent and its spectrophotometric determination

Diazald, a chemical intermediate for the synthesis of biologically active compounds, was found to be a potent in vitro antimicrobial agent against yeasts, yeast-like and filamentous fungi as well as Gram-positive and Gram-negative bacterial strains. Its activity is not inhibited by either para-aminobenzoic acid (PABA) or the nitroso group-specific 2-aminothiazole-methoxyimino acetic acid (ATMAA). This suggests that the molecule as such is responsible for the antimicrobial activity. For its quick measurement a sensitive spectrophotometric method has been developed.

Differential protection by two sunscreens from UV radiation-induced immunosuppression

A controversy has arisen concerning the ability of sunscreens to protect mice from the immunosuppressive effects of UV radiation. We have assessed the photoprotection in hairless mice of two sun protection factor (SPF)15 sunscreens containing different UVB (280-320-nm) absorbers, namely, octyl-N-dimethyl-p-aminobenzoate (o-PABA) or 2-ethylhexyl-p-methoxycinnamate (2-EHMC). Following three minimum erythemal exposures to UV radiation, both systemic suppression of contact hypersensitivity to 2,4-dinitrofluorobenzene and induction of susceptibility to transplanted UV radiation-induced tumor cells was established. Topically applied 2-EHMC sunscreen protected totally from both forms of immunosuppression, but the o-PABA sunscreen failed to protect, although both sunscreens were equally effective in protection from UV radiation-induced erythema and edema.

Effects of medium alterations on in vitro development of Brugia malayi larvae in cultured mosquito thoraces

A recent study showed that 1-day-old, intracellularly lodged larvae of Brugia species develop in vitro to the infective third-stage larvae (L3) in excised thoraces of susceptible mosquitoes in the diphasic insect tissue culture medium containing a nutrient agar base overlaid with a 1:1 mixture of Schneider's Drosophila medium and Grace's insect cell culture medium supplemented with 20% fetal bovine serum (FBS) and antimicrobial agents. In the present investigation, the diphasic culture medium was used to evaluate the effects of medium alterations on the development of 1-day-old, intracellularly lodged larvae of subperiodic Brugia malayi in excised thoraces of Aedes aegypti to the L3. One-day-old larvae developed to the L3 in medium without nutrient agar base, at pH 7.0 and pH 7.5, in Hanks' balanced salt solution (HBSS) and in HBSS supplemented with bovine albumin fraction-V (BAF-V). These larvae also developed in the absence of FBS in the overlay medium, in overlay medium containing 5-20% FBS, in medium components obtained from different sources, in serum free Sf-900 (GIBCO) medium, and when FBS is replaced by BAF-V in the overlay medium. The percentage of L3 was not increased substantially in infected excised thoraces of mosquitoes when nutrient supplements, such as folic acid, p-aminobenzoic acid, glucose, lipid concentrate, hemin, or reduced glutathione, were added to the overlay medium containing BAF-V. These results suggested that 1-day-old, intracellularly lodged larvae developed to the L3 in infected excised thoraces of mosquitoes at almost the same rate as in intact mosquito, when excised thoraces were maintained alive under optimal conditions in a culture medium.

[The inhibition of endothelial cell proliferation by esters of 4-aminomethylbenzoic acid (pamba)]

PAMBA-esters are able to decrease the proliferation of in vitro cultivated endothelial cells. PAMBA-hexylester was found to be the most effective one. In comparison to PAMBA-ethylester the ethylesters of EACA, 4-amino-benzoic acid, 4-amidinobenzoic acid and 4-amidino-phenylpyruvic acid were investigated.

Characterization of arylamine acetyltransferase in the rabbit eye

The activity of arylamine acetyltransferase with p-aminobenzoic acid (PABA), sulfamethazine (SMZ), and aminozolamide as substrates was studied in rabbit tissue homogenates of the corneal epithelium, stroma-endothelium, iris-ciliary process, and liver. Rabbits were classified as rapid or slow acetylators with respect to their rate of hepatic acetylation of SMZ. The ocular disposition of aminozolamide in the two phenotypes was compared using a topical ocular infusion method that permitted a constant concentration to remain in contact with the intact cornea. The effect of hepatic-acetylator phenotype on the intraocular pressure (IOP) recovery rate and drug concentrations in tissues after single-dose administration of aminozolamide also was studied. In general, the rank order of arylamine acetyltransferase activity regardless of substrate was liver greater than iris-ciliary process greater than corneal epithelium greater than stroma-endothelium. The specific activity with aminozolamide as substrate was greater than that with SMZ in each tissue homogenate and greater than with PABA as substrate in all tissues except the stroma-endothelium of slow hepatic-acetylator rabbits. Very low enzyme activity ratios for ocular acetylation between rapid and slow hepatic-acetylating rabbits indicated that acetylation in the ocular tissues did not correspond with the acetylation phenotype. At various times during and after topical infusion to the anesthetized rabbit, assay determinations of drug and metabolite in ocular tissues indicated that there were no significant differences between phenotypes in the disposition of either drug or metabolite. These results correlate with the IOP measurements after topical infusion; they also showed no difference in the effect of aminozolamide between hepatic-acetylator phenotypes. These results indicate that the ocular disposition and the decrease in IOP from topical application of aminozolamide is independent of the hepatic-acetylation phenotype in the rabbit. There are significant amounts of acetyltransferase activity in the ocular tissues of the rabbit with these three substrates, indicating that acetylation may be occurring for other arylamine drugs used in the eye.

UV-irradiation potentiates the antimutagenicity of p-aminobenzoic and p-aminosalicylic acids in Salmonella typhimurium

UV-irradiation (254 nm, 10 or 20 J/cm2) of p-aminobenzoic acid (PABA) and p-aminosalicylic acid (NaPAS) potentiated their antimutagenicity towards N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis in Salmonella typhimurium. Their inhibitory action towards the formation of the mutagen N-methyl-N-nitrosourea from the nitrosation mixture of N-methylurea and nitrite was also increased by UV-irradiation. In contrast, UV-irradiated PABA exhibited no inhibitory effects towards the mutagenicity of sodium azide or 3-azidoglycerol. Neither PABA nor NaPAS nor their UV-irradiation products were themselves mutagenic in the Ames assay.

[Mechanism of the antimutagenic effect of interferon in human fibroblasts based on induced protein analysis]

Proteins induced in human fibroblasts after treatment of some antimutagens (interferon, p-aminobenzoic acid, heating and vaccinia virus infection) were identified by means of polyacrylamide gel electrophoresis (10-15%) followed by fluorography of the gel. Influenza virus proteins (A/WSN/33) were used as markers to determine the molecular weights of the new proteins. The results obtained suggest that interferon, p-aminobenzoic acid, heating and vaccinia virus infection induced proteins with mol. weights of 24 and 18 kD except the protein with 76 kD observed only after heating insult.

Effects of four chemicals on N-acetyltransferase activities in human U937 cell line

The effects of p-aminobenzoic acid (PABA), procainamide (PA), anisidine (AN) and isoniazid (INH) on N-acetyltransferase (NAT) activities in cultured human cells were determined. PABA increased the specific activity of PABA NAT in the U937 cells but not in the Hep G2 cells. The enzyme activity in the PABA-treated U937 cells was restored to normal within 4 d after removing PABA from medium. These results imply that the PABA NAT activity in the U937 cells can be induced by PABA and the PABA NAT in the U937 cells is different from that in the Hep G2 cells. INH increased the INH NAT specific activity in the U937 cells but decreased the PABA NAT activity. AN decreased both the AN NAT and the PABA NAT specific activities in the U937 cells. PA did not affect the specific activities of PABA NAT or glucose-6-phosphate dihydrogenase (G-6-P DH) in the U937 cells. PABA also increased the specific activities of AN NAT and G-6-P DH. This implies that the induction effect of PABA on the PABA NAT activity is not specific. In this study the PABA NAT specific activity was increased only by PABA, and the INH NAT activity only by INH. However, the AN NAT activity could be induced by PABA but not by AN. These results indicate that induction of some but not all NAT activities has a limiting specificity.

Influence of vasoactive substances on uremic bleeding in rats

Bleeding time is prolonged following resection of kidney tissue as well as after ureteral occlusion. Bilateral nephrectomy raises bleeding time from 17 to 67 min, and blood loss can be increased from 2 to 12 microliters/min. Plasmatic coagulation factors remain unchanged in uremic rats. There is no influence of various surgical interventions producing uremia on function of thrombocytes. In rats with intact kidney function and following bilateral nephrectomy a diminution of bleeding time is demonstrable after administration of histamine or captopril. Shortening of bleeding time by the antifibrinolytic substance p-aminomethylbenzoic acid seems to indicate an increased fibrinolytic activity in uremic rats.

Improved therapeutic index of cisplatin by procaine hydrochloride

The local anesthetic procaine hydrochloride (P.HCl) had little effect on the sensitivity of P388 leukemic cells to cisplatin (DDP) in vitro, but the simultaneous administration of DDP and P.HCl (40 mg/kg) to BDF1 mice produced 50% lethal dose (LD50) and 90% lethal dose (LD90) values approximately two times higher than those observed with DDP alone. DDP-P.HCl diluted in water and administered intraperitoneally (IP) on day 1 and on days 1 and 5 to BDF1 mice bearing P388 leukemic cells produced 33% and 50% cure rates, respectively, at the maximum tolerated dose (16 mg/kg for the single administration and 10 mg/kg given on days 1 and 5). In contrast, under the same conditions, the cure rates obtained with DDP alone (10 mg/kg for the single administration and 8 mg/kg given on days 1 and 5) were 17% and 9%, respectively. Protection from DDP nephrotoxicity seems to be the explanation for the higher doses of DDP that mice can tolerate when DDP is given simultaneously with P.HCl. In fact, the increased blood urea nitrogen (BUN) levels observed 4-7 days following a single IP administration of DDP (8 or 16 mg/kg), as well as the tubular degenerative changes detected by light microscopy, were not observed when the same doses of DDP were given simultaneously with P.HCl. Since DDP nephrotoxicity is known to be reduced when the drug is diluted in 0.9% NaCl solution, we compared the combinations DDP-P.HCl in water, and DDP and DDP-P.HCl in 0.9% NaCl solution. The antitumor activity of DDP diluted in water and administered with P.HCl was similar to that observed in mice treated with DDP alone diluted in 0.9% NaCl solution. However, further improvement of the therapeutic index was achieved after the administration of DDP-P.HCl diluted in 0.9% NaCl solution; this regimen produced a cure rate of 67% (12 of 18 animals). The clinical relevance of these findings is strengthened by the observation that similar results were obtained when P.HCl was given by the intravenous route.