Effect of age on the gastrointestinal absorption of acyclovir in rats

Drug elimination from the body after intravenous administration of acyclovir (20 mg kg-1) was delayed in 1-week-old rats but the pharmacokinetic data for 2.5-week-old rats were the same as those for 8-week-old rats. The areas under the plasma concentration-time curves at 0-infinity h (AUC) after oral administration of acyclovir (20 mg kg-1) decreased with increasing age. The absolute bioavailabilities for 1-, 2.5-, 3- and 8-week-old rats were 77.59, 51.52, 14.61 and 7.30%, respectively. The gastrointestinal absorption of poorly absorbed acyclovir was good for rats younger than 2.5 weeks but dropped abruptly between 2.5 and 3 weeks of age. The intestinal membrane permeability of acyclovir was studied using the everted sac method. The rate of transfer of an initial concentration of 10 microM acyclovir from the mucosal to the serosal side was constant until 60 min in rats of different ages while the rate in 2.5-week-old rats was significantly greater than that in 3-, 4- and 8-week-old rats. Abrupt in-vivo and in-vitro changes were observed in the experimental results between 2.5- and 3-week-old rats; this period coincided with the weaning period of the rat. The membrane transport mechanism of acyclovir in 2.5- and 8-week-old rats was also studied. Cumulative transferred amounts of acyclovir were linear (r = 0.99) over the range 5 microM-1 mM and dose-independent. The influence of metabolic inhibitors (sodium azide, 2,4-dinitrophenol, ouabain), purine and pyrimidine analogues (2-deoxyguanosine, guanine, adenine, uridine) and temperature on the permeation of acyclovir was studied. The permeation of acyclovir was inhibited only by 2-deoxyguanosine and guanine in 2.5-week-old rats. These results suggest that throughout the maturation period, the gastrointestinal absorption mechanism of acyclovir is predominantly via passive diffusion with little or no active or facilitated transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcoronary chemical ablation of atrioventricular node for the treatment of paroxysmal supraventricular tachycardia--a case report

We applied transcoronary chemical ablation of the atrioventricular (AV) node to a patient with uncontrollable paroxysmal supraventricular tachycardia (PSVT). Through an angioplasty dilatation catheter. 99% ethanol at a dose of 1.0 ml was selectively infused into the AV nodal artery. Complete AV block with junctional escape rhythm occurred. Two weeks later, the treadmill exercise test was performed according to a modified Bruce protocol. The patient tolerated for 12 min, and the heart rate increased to 85 beats/min. His bundle electrocardiogram showed that the AV block resulted from atrio-Hisian block. Neither atrial nor ventricular extrastimulus could induce the tachycardia. It appeared that chemical ablation was a good method for controlling medically resistant PSVT. Elevation of serum creatine kinase was observed when ethanol overflowed during the ablation procedure. Occlusion of branches of the AV artery and mild hypokinesis in the inferobasal wall of the left ventricle were seen.

Clinical significance of urinary enzymes in diabetic nephropathy

Urinary enzyme activities (N-acetyl-beta-D-glucosaminidase [NAG], alkaline phosphatase [ALP], leucine aminopeptidase [LAP], gamma-glutamyl transpeptidase [gamma-GTP]) were investigated to determine their clinical significance in diabetic nephropathy. There were correlations among ALP, LAP, and gamma-GTP, though no correlation existed between NAG and the other three enzymes. Activities of NAG isozymes (both A and B) were higher than in normal controls. It has been reported that NAG isozyme A might be associated with glomerular diseases, and isozyme B might be associated with proximal tubular damage. The results of our study suggest that NAG reflects lysosomal dysfunction of both glomerular and proximal tubular epithelial cells, which may be caused by poor glycemic control, and that ALP, LAP, and gamma-GTP reflect brush border damage of proximal tubules, which may be caused by diabetic nephropathy.

Production of 15-hydroxyeicosatetraenoic acid by purified human eosinophils and neutrophils

In the presence of high concentrations of exogenous arachidonic acid (greater than or equal to 10 microM), eosinophils produced 15-hydroxyeicosatetraenoic acid (15-HETE) in the absence of stimuli. The calcium ionophore A23187, as well as the chemotaxins used in this study--complement split product C5a, platelet-activating factor (PAF), and N-formyl-methionyl-leucyl-phenylalanine (FMLP)--failed to increase 15-HETE production, indicating that eosinophil 15-lipoxygenase is already active. Production of 15-HETE from eosinophils increased with increasing concentrations of arachidonic acid, exogenously added. Maximal 15-HETE production was observed to be 1111 +/- 380 ng per 10(6) eosinophils at the concentration of 100 microM of arachidonic acid. With low concentrations of exogenous arachidonic acid (below 2 microM), eosinophils were considered to incorporate exogenous arachidonic acid into their cell membrane, and did not produce 15-HETE. In contrast, 15-HETE formation in highly purified neutrophils (eosinophils less than 1%) was negligible compared with that in eosinophils (300-fold less), suggesting that 15-HETE-forming activity in granulocytes is derived from the eosinophil 15-lipoxygenase pathway and that neutrophils may lack 15-lipoxygenase activity.

Identification of a novel and highly potent eosinophil chemotactic lipid in human eosinophils treated with arachidonic acid

Purified human eosinophils generate eosinophil chemotactic lipids (ECL), when incubated with arachidonic acid without any stimulus. Reversed phase HPLC of incubation supernatants revealed major lipid-like eosinophil chemotactic activity eluting in a peak containing 5(S), 15(S)dihydroxy-6,13-trans-8,11-cis-eicosatetraenoic acid (5,15-DiHETE) as well as a 8,15-dihydroxyeicosatetraenoic acid. For further characterization of the ECL, some authentic dihydroxyeicosatetraenoic acids were tested for eosinophil chemotactic activity. Only 5,15-DiHETE as well as 8(S), 15(S)-dihydroxy-5,11-cis-9,13-trans-eicosatetraenoic acid were found to be chemotaxins for human eosinophils, however, with an ED50 near 0.3 microM and 1.5 microM, respectively. The presence of high titer eosinophil chemotactic activity in ECL preparations let us look for a contaminating ECL with higher specific activity. By using a different reversed phase HPLC-system 5,15-DiHETE as well as 8(R), 15(S)-dihydroxy-5,11-cis-9,13-trans-eicosatetraenoic acid could be separated from a highly potent ECL. Final purification of this ECL by the use of straight phase HPLC resulted in a single at 260 nm absorbing peak giving an UV spectrum different from that known for eosinophil chemotactic factors indicating a novel type of eosinophil chemotactic lipid. Eosinophil chemotactic activity of purified ECL has been found to be similar to that seen for platelet-activating factor, the most potent chemotaxin so far known, either in the number of migrating cells or the ED50. Cross-desensitization experiments with ECL, leukotriene B4, and platelet-activating factor revealed the existence of a separate ECL receptor on eosinophils. The production of potent ECL by the responder cells themselves supports the idea that there exists a self-sustaining mechanism of eosinophil accumulation.

Identification of a novel and highly potent eosinophil chemotactic lipid in human eosinophils treated with arachidonic acid

Purified human eosinophils generate eosinophil chemotactic lipids (ECL), when incubated with arachidonic acid without any stimulus. Reversed phase HPLC of incubation supernatants revealed major lipid-like eosinophil chemotactic activity eluting in a peak containing 5(S), 15(S)dihydroxy-6,13-trans-8,11-cis-eicosatetraenoic acid (5,15-DiHETE) as well as a 8,15-dihydroxyeicosatetraenoic acid. For further characterization of the ECL, some authentic dihydroxyeicosatetraenoic acids were tested for eosinophil chemotactic activity. Only 5,15-DiHETE as well as 8(S), 15(S)-dihydroxy-5,11-cis-9,13-trans-eicosatetraenoic acid were found to be chemotaxins for human eosinophils, however, with an ED50 near 0.3 microM and 1.5 microM, respectively. The presence of high titer eosinophil chemotactic activity in ECL preparations let us look for a contaminating ECL with higher specific activity. By using a different reversed phase HPLC-system 5,15-DiHETE as well as 8(R), 15(S)-dihydroxy-5,11-cis-9,13-trans-eicosatetraenoic acid could be separated from a highly potent ECL. Final purification of this ECL by the use of straight phase HPLC resulted in a single at 260 nm absorbing peak giving an UV spectrum different from that known for eosinophil chemotactic factors indicating a novel type of eosinophil chemotactic lipid. Eosinophil chemotactic activity of purified ECL has been found to be similar to that seen for platelet-activating factor, the most potent chemotaxin so far known, either in the number of migrating cells or the ED50. Cross-desensitization experiments with ECL, leukotriene B4, and platelet-activating factor revealed the existence of a separate ECL receptor on eosinophils. The production of potent ECL by the responder cells themselves supports the idea that there exists a self-sustaining mechanism of eosinophil accumulation.

Chemotactic responsiveness of eosinophils isolated from patients with inflammatory skin diseases

We determined the chemotactic responsiveness of peripheral eosinophilic granulocytes (eosinophils) isolated from patients with inflammatory dermatoses and healthy volunteers. Ten patients with atopic dermatitis, five patients with drug reactions, ten patients with psoriasis, and fourteen healthy volunteers were studied. Well characterized chemotaxins, the complement split product C5a, leukotriene B4 (LTB4), platelet activating factor (PAF), and N-formyl-methionyl-leucyl-phenylalanine (FMLP), were used as chemoattractants. Eosinophils from healthy volunteers showed strong migratory responses towards C5a and PAF but responded poorly to LTB4 and FMLP. When patients were grouped by disease severity, eosinophil chemotactic responses to PAF were significantly enhanced in severely affected patients (p less than 0.05); this was not true with C5a, LTB4 or FMLP. This enhanced eosinophil chemotaxis to PAF was not related to a specific disease. No correlation between eosinophil chemotactic activity and peripheral blood eosinophil count was observed. The increased responsiveness of circulating eosinophils towards PAF may be related to altered receptor expression during cutaneous inflammation.

[Establishment of a human skin squamous cell carcinoma cell line (SCC-1CB) in vitro and its characteristics]

A human skin tumor cell line SCC-1CB has been established in vitro. A specimen from a surgically excised tumor with moderately differentiated squamous cell carcinoma of skin from a Japanese male, aged 62, was transplanted subcutaneously into nude mice. After growth, a part of the tumor was passaged with a transplantation needle. At the fourth passage, part of the tumor was explanted into culture dishes. Cell cultures were maintained in Eagle's minimal essential medium supplemented with 10% fetal calf serum. A SCC cell line (SCC-1CB) was cloned and then established. Chromosome analysis revealed the human type with a mode number of 56. The cell line is tumorigenic in nude mice. Immunohistochemical staining revealed that keratin, cytokeratin and vimentin were positive and desmin was negative. It can be cryopreserved in liquid nitrogen. It has successfully maintained proliferation in continuous cell culture for over 2.5 years. The cells retain their original morphological appearance as determined by light and electron microscopy.

Differential sensitivities of purified human eosinophils and neutrophils to defined chemotaxins

Functions of eosinophils and neutrophils isolated from normal human blood were determined by measuring chemotactic migration and release of beta-glucuronidase. Four well-characterized chemotaxins, the complement fragment C5a, formyl-methionyl-leucyl-phenylalanine (FMLP), platelet-activating factor (PAF), and leukotriene B4 (LTB4) were used as stimuli. Neutrophils showed remarkable chemotactic responses to all four chemotaxins. In contrast, eosinophils showed a significant chemotactic response to C5a and PAF, but only weak responses to FMLP and LTB4. Using these chemotaxins we found the following order of chemotactic potency (maximal number of migrated cells): C5a = LTB4 greater than FMLP greater than PAF for neutrophils and PAF = C5a greater than LTB4 = FMLP for eosinophils. Neutrophils elicited a significant beta-glucuronidase release when stimulated by C5a and FMLP, whereas only small amounts were released with PAF and LTB4. On the other hand, an amount of beta-glucuronidase released from eosinophils comparable to that from neutrophils was elicited only with C5a. FMLP, LTB4, and PAF caused the release of small percentages of beta-glucuronidase. The important cellular functions of eosinophils and neutrophils, chemotaxis and enzyme release, are thought to be controlled by differential responsiveness to stimuli.

Intestinal absorption of pyridoxal 5'-phosphate at physiological levels in rats

The intestinal absorption of pyridoxal 5'-phosphate (PLP) at physiological levels (10(-7) -10(-6) M) was studied in comparison with that of pyridoxal (PL) in rat, using in vitro everted sac and an intestinal preparation that permitted continuous in situ collection of mesenteric venous blood. After PLP administration (10(-6) -10(-3) M) in situ, larger amounts of PLP were found in the mesenteric venous plasma than after PL administration at the same dose. The amount of PLP found in the mesenteric venous plasma was dependent on its dose at lower concentrations up to 10(-4) M but became independent at higher concentrations. After PL administration at various doses, the amount of PL found in the mesenteric venous blood increased linearly with the dose. When various concentrations of PLP were added to the mucosal side, under the in vitro condition with protection from alkaline phosphate hydrolysis, PLP was detected in the serosal side and the extent of PLP transport was dependent on the initial concentration of PLP in the mucosal side. When various concentrations of PL were added to the mucosal side, the extent of PL transport was independent of the initial concentration of PL in the mucosal side. In rat pretreated with actinomycin D, PLP transport in vitro was inhibited but not that of PL. N2-induced anoxia and pyridoxamine 5'-phosphate and anion transport inhibitor (4,4'-diisothiocyanostilben-2,2'-disulfonic acid disodium salt) showed no effect on PLP transport. These results suggest that PLP can be absorbed in the phosphorylated form and imply the presence of a saturable process for direct absorption of PLP itself and a diffusive process for PL absorption. In addition, the result of the in vivo neonatal experiment suggests that the neonatal intestine also can transport PLP in phosphorylated form.

Purification and partial biochemical characterization of a human monocyte-derived, neutrophil-activating peptide that lacks interleukin 1 activity

A novel monocyte-derived neutrophil-activating peptide (MONAP) produced by lipopolysaccharide- and phorbol myristate acetate-stimulated human peripheral blood monocytes was purified by sequential ion exchange-high performance liquid chromatography (HPLC), size exclusion HPLC, and reversed phase HPLC. Biologic activities of the purified cytokine were monitored by either an enzyme release assay or a chemotaxis assay, using peripheral human neutrophils. Purified MONAP was found to be homogeneous, giving a single peak on size-exclusion HPLC, reversed-phase HPLC, as well as a single 10-kDa band on silver-stained polyacrylamide gels. Purified MONAP stimulate human neutrophil chemotaxis at an estimated molarity of 5 x 10(-11) M. Half-maximal enzyme release of cytochalasin B pretreated neutrophils occurred at 2 to 3 x 10(-10) M, whereas superoxide anion production elicited by various concentrations of MONAP was found to be low. Isolated human peripheral monocytes, as well as human eosinophils, showed no chemotactic response to MONAP, indicating neutrophil specificity. MONAP activity was separated from thymocyte-stimulating activity by reversed-phase HPLC, indicating nonidentity with interleukin (IL)-1. This was further supported by heat resistance of MONAP, which is in contrast to the heat sensitivity of IL-1. In addition, IL-1 obtained as a by-product during isolation of MONAP did not stimulate human neutrophil chemotaxis.

Purification and partial biochemical characterization of a human monocyte-derived, neutrophil-activating peptide that lacks interleukin 1 activity

A novel monocyte-derived neutrophil-activating peptide (MONAP) produced by lipopolysaccharide- and phorbol myristate acetate-stimulated human peripheral blood monocytes was purified by sequential ion exchange-high performance liquid chromatography (HPLC), size exclusion HPLC, and reversed phase HPLC. Biologic activities of the purified cytokine were monitored by either an enzyme release assay or a chemotaxis assay, using peripheral human neutrophils. Purified MONAP was found to be homogeneous, giving a single peak on size-exclusion HPLC, reversed-phase HPLC, as well as a single 10-kDa band on silver-stained polyacrylamide gels. Purified MONAP stimulate human neutrophil chemotaxis at an estimated molarity of 5 x 10(-11) M. Half-maximal enzyme release of cytochalasin B pretreated neutrophils occurred at 2 to 3 x 10(-10) M, whereas superoxide anion production elicited by various concentrations of MONAP was found to be low. Isolated human peripheral monocytes, as well as human eosinophils, showed no chemotactic response to MONAP, indicating neutrophil specificity. MONAP activity was separated from thymocyte-stimulating activity by reversed-phase HPLC, indicating nonidentity with interleukin (IL)-1. This was further supported by heat resistance of MONAP, which is in contrast to the heat sensitivity of IL-1. In addition, IL-1 obtained as a by-product during isolation of MONAP did not stimulate human neutrophil chemotaxis.

Gastrointestinal absorption of sulfaguanidine in neonatal and adult rats

The pharmacokinetics of sulfaguanidine in rats was studied after its intravenous or oral administration. In adult rats, its elimination from plasma, after intravenous administration of 2.5 or 25 mg/kg doses, could be described by a two-compartment open model, while its plasma concentration after oral administration of 25 mg/kg doses, agreed with the one- or two-compartment open model. Neonatal rats displayed a lower elimination of sulfaguanidine than adult rats. Comparison of the drug's gastrointestinal absorption showed that the maximum plasma concentration after oral administration was significantly higher for neonatal than for adult rats. However, there was no significant difference between the times required to reach maximum plasma concentrations. The area under the plasma concentration-time curve at 0-infinity h was significantly higher for neonatal than for adult rats. The absolute bioavailability (57.86%) in neonatal rats was approximately five times that (12.76%) in adult rats. Thus, sulfaguanidine was poorly absorbed by adult rats, but was efficiently absorbed by immature gastrointestines of neonatal rats.

Gastrointestinal absorption of sulpiride in rat

A two-compartment model could be used to describe the elimination of sulpiride from plasma after intravenous administration of 25 and 50 mg/kg doses to rat. The absolute bioavailability after oral administration was only about 15% which was also the level after intraduodenal administration. Higher bioavailabilities were found after mesenteric venous and intravenous administration (sham-operated rat) due to a decrease in the beta-value (elimination rate constant). The low bioavailability of sulpiride following oral administration was concluded to result, not from metabolism in the liver, but from reduced absorption by the gastrointestinal tract.

Cloning of Drosophila choline acetyltransferase cDNA

Choline acetyltransferase (EC 2.3.1.6) is the biosynthetic enzyme for the neurotransmitter acetylcholine. To isolate choline acetyltransferase cDNA clones, a cDNA library was constructed from poly(A)+ RNA of Drosophila melanogaster heads, these being one of the richest known sources of the enzyme. By screening the cDNA library with a mixture of three different monoclonal antibodies to Drosophila choline acetyltransferase, we isolated 14 positive clones. Only 1 of these clones was identified to be a Drosophila choline acetyltransferase cDNA clone based on the following evidence. (i) The amino acid sequence deduced from the nucleotide sequence of the cDNA insert completely corresponded to that of several tryptic peptides from choline acetyltransferase. (ii) The cDNA insert hybridized specifically to only the region on Drosophila polytene chromosomes that had been identified as the site of the choline acetyltransferase (Cha) gene by cytogenetic analysis. The cDNA insert consisted of a coding region 2190 nucleotides long, a 3'-noncoding region 284 nucleotides long, and EcoRI linkers. RNA analysis of Drosophila head poly(A)+ RNA with the cDNA insert as a probe showed the choline acetyltransferase mRNA to be approximately equal to 4700 nucleotides long.

Vulcanization Chemistry

Prevulcanization inhibitors based on triazines can be prepared. In each case the triazine ring is amino-substituted such that one or two of the amino hydrogen atoms per amino-group are alkylthio- or arylthio-substituted. The new triazine-derived prevulcanization inhibitors are extremely active in accelerated sulfur vulcanization of diene rubbers (e.g., NR or SBR). Differing accelerators or accelerator systems may require different triazine-derived prevulcanization inhibitors for best results. Provided that the reactivity of the inhibitor is sufficiently near the ideal, its weight-basis activity is greatest when its equivalent weight per S—N bond is least. Overall, hexakis(cyclohexylthio)melamine and especially hexakis(isopropylthio)melamine are the most effective premature vulcanization inhibitors tested, on an equal-weight basis.

Correlation Analysis of Curing Agents

The linear correlation of the pKa to the σ* constants of the substituted phenylthio group indicates the validity of the σ* being equal to the sum of the Hammett's constant of these substituent groups and the σ* of the phenyl group (0.6). The inhibitory activity of the compound LSR depends on the reactivity of BtSSR with BtSH and the general stability of the mixed disulfides which form during the curing process. For BtSSR as accelerators, the Hammett's rule applies to scorch delay time versus σ* constant as the variable with negative slope in the LFER. In benzothiazole-2-sulfenamides, the 13C NMR chemical shift of the carbon at the 2-position of the benzothiazolyl group (C8) is consistently greater than the chemical shift at the carbon adjacent to the amino nitrogen (CN) in the same molecule. It indicates that the electronic distribution at the S-N bond is consistently more positive at the S atom and more negative at the amino nitrogen. The 13C NMR chemical shift at C8 is inversely proportional to the σ* constant of the amino substituents. A wider range of amino substituents is applicable for the correlation analysis with 13C chemical shifts than σ* constants as the variable. When benzothiazole-2-sulfenamides are used as accelerators, two linear relationships with slopes of opposite signs are obtained for the N-substituted phenyl and the N-alkyl sulfenamides, respectively, in the relationship of the scorch delay to the 13C8 chemical shift or the σ* constant. Longer scorch delay was obtained with the pertinent electron-withdrawing phenyl or the sterically hindered alkyl substituents. The more basic amino derivatives give a faster acceleration rate and a higher crosslink efficiency. A significant linear correlation was obtained for scorch delay versus Hammett's σ constant of the phenyl substituents of the N,N′-dithiobisformanilides as vulcanizing agents.

Linear Free Energy Relationship Involving the Properties of Prevulcanization Inhibitors

The utilization of σ* constants for substituted phenyl groups converted from the known Hammett σ constants of the phenyl substituents is useful in assessing the linear free energy relationship (LFER) of the properties of various inhibitors. The inhibitors include thioketals, sulfenamides and N,N′thiobis(substituted formanilides). In the LFER of the rate of reaction between thioketals with 2-mercaptobenzothiazole, the rate is fastest when the thio group of the thioketal is attached to a substituted phenyl with the highest positive σ constant. The σ constant of alkyl groups is negative, and an alkylthio group gives a thioketal with a slower reaction rate. The LFER applies to the 13C NMR shift of the quaternary carbon of the thioketals with alkylthio groups. The slope of the linear relation is positive. However, changes in the 13C NMR shift of the arylthio derivatives are relatively small in spite of a wide variation in σ* constant. The LFER applies to the scorch delaying activities of all structural types of inhibitors in stocks accelerated by various benzothiazoles. In the linear relationship of scorch delay versus σ* constant in each type of inhibitor, the slope is negative. Variables with negative σ* constants give longer delay and those with more positive σ* constants give shorter delay. An exception is in the very fast curing MSSM/DPG stock where the thioketals from acetoacetanilide with arylthio groups give longer delay than the alkylthio compounds. In the TBBS-accelerated stock, the slopes of the linear relation of the carbamate sulfenamides, N,N′-thiobisformanilides and thioketals of cyanoacetanilides are about equal. However, the level of scorch delay obtained with the sulfenamides is significantly higher than the other two, which are equal in inhibition level. The inhibition action of N,N′-thiobisformanilides without alkylthio or arylthio groups is probably due to the formation of labile formanilide polysulfide intermediates.

[Antitumor effects of aromatic retinoids (Ro 10-1670, Ro 10-9359) on the chemically-induced epithelial tumors]

Pathological and histochemical studies were made to clarify the response to an aromatic retinoids (Ro 10-1670, Ro 10-9359) of the papilloma and carcinoma in hamster cheek pouch and mouse dorsal skin. The sizes of papilloma and carcinoma were remarkably reduced or completely regressed following systemic and topical administration of the aromatic retinoids. The antitumor effects increased in proportion to the frequency of administration than doses and were showed no side effects. Tumor tissues responded remarkably to the aromatic retinoids indicated an irregular keratinization including loss of hornified cells, nuclear vacuolization and inflammatory infiltrates which located in the border layer between stromas and neoplastic epithelia. Histochemically, tumor tissues which intensely affected by drugs were characterized by the presence of abundant acid phosphatase active cells. Those acid phosphatase active cells may be consisted of tumor cells, histiocytes and fibroblasts. In the electrocytochemical study acid phosphatase (a lysosomal marker enzyme) activity was found in epithelial tumor cells and fibroblasts. These results were indicated that epithelial tumor regression by aromatic retinoids the might be due to the accelerated lysosomal activity in the tumor cells and fibroblasts.

Thioketals as Prevulcanization Inhibitors

Thioketals prepared from active methylene compounds are introduced as a new class of nonthioimide prevulcanization inhibitors and compared to other inhibitors in various accelerator systems. The chemical nature of the inhibition by these thioketals has been examined from the interrelations of chemical structure of the thioketals, 13C chemical shift of the quaternary carbon, rate of reaction with 2-mercaptobenzothiazole, and scorch delay.

Pituitary response to luteinizing hormone-releasing hormone during haloperidol-induced hyperprolactinemia

The effects of a 6-hour infusion with haloperidol on serum prolactin and luteinizing hormone (LH) levels was studied in a group of male subjects. Five hours after starting the infusions, a study of the pituitary responses to LH-releasing hormone (LH-RH) was carried out. Control patients received infusions of 0.9% NaCl solution. During the course of haloperidol infusions, significant hyperprolactinemia was found, together with an abolished pituitary response to LH-RH, as compared with responses of control subjects.

Effect of dyes on the photodecomposition of pyridoxine and pyridoxamine

Erythrosine, eosine Y, rose bengal, mercurochrome, methylene blue, azure A and azure B accelerated the photodecomposition of pyridoxine and pyridoxamine at pH 5-9, but fluorescein and acid red did not. The photodecomposition of pyridoxine in the presence of erythrosine was greatest at pH 9.0. The singlet oxygen generated by light-excited dyes played a role as a mediator in the decomposition of pyridoxine and pyridoxamine in the presence of dyes was depressed by aminopyrine, sulpyrine and tryptophan. Pyridoxine 3,4'-dioctanoate was stable in the presence of erythrosine.

Stability, bactericidal activity, vitamin B6 activity and gastrointestinal absorption of benzoic acid esters of pyridoxine

alpha 4-O-Benzoyl-pyridoxine (PN-4'MB) and alpha 5-O-benzoyl-pyridoxine (PN-5'MB) were hydrolyzed in 10% aqueous solution of acetone at pH 1-4. They were hydrolyzed obeying apparent first-order kinetics. In the pH range of 1-7, PN-4'MB was hydrolyzed 10 times faster than PN-5'-MB. At pH 7-12, an interconversion between the two derivatives was observed. They were bactericidal against Escherichia coli and Bacillus subtilis and prevented severe convulsions induced in mouse by 4'-methoxypyridoxine, a potent antagonist of vitamin B6. PN-4'MB was hydrolyzed with the homogenate of rat liver more easily than PN-5'MB. The metabolite of PN-MBs in man was identified as 4'-pyridoxic acid, i.e., a principal metabolite of PN, using high-performance liquid chromatography. The amount of urinary excretion of 4'-pyridoxic acid in 10 hr after oral administration of PN-4'MB or PN-5'MB was as large as that of PN.

Reactions of Resin Formers in Dry Bonding Rubber Systems

An unusual two step viscosity change was observed during the Mooney scorch test of some dry bonding stocks of a NR/SBR blend. This behavior was found to involve the resin formation and resin crosslinking of rubber. The effects of the resin formers, hexamethylenetetramine as the methylene donor and resorcinol, m-aminophenol or m-phenylenediamine as the acceptor, were analyzed by the application of a prevulcanization inhibitor. The merits of m-phenylenediamine as an adhesion promoter are described.

S-N Compounds as Delayed Action Chemicals in Vulcanization

Since the discovery by Goodyear in 1839 that the physical properties of rubber may be improved with sulfur, it has been the most commonly used crosslinking agent. The rubber industry is concerned with the production of homogeneous products with appropriate physical properties, by compounding rubber with ingredients, including crosslinking agents, followed by processing, molding, and introduction of chemical bonds. Economically, it is advantageous to apply high temperature which reduces processing and curing time. However, application of high temperatures frequently causes premature cure. Compounding adjustments are often required in the plants to prevent scorch, especially by the use of compounds with S—N bonds as accelerators, vulcanizing agents, and also as prevulcanization inhibitors or retarders which delay the crosslinking reaction of sulfur and rubber. There are several reviews relating to accelerators, retarders, and vulcanization, which discuss S—N compounds as delayed action curing agents. This review covers the development of S—N compounds as delayed action chemicals for vulcanizing rubber, the various structural types, properties, applications, and the mechanism of their function during vulcanization.

Competitive inhibition between 4'-substituted pyridoxine analogues and pyridoxal for pyridoxal kinase from mouse brain

4'-Substituted pyridoxine analogues (4'-PN analogues), which were potent antagonists of vitamin B6, induced severe convulsions in mouse which could be prevented by vitamin B6. To elucidate the mechanism of the convulsive action, the effect of 4'-PN analogues on partially purified pyridoxal kinase (PL-kinase) from mouse brain was studied. 4'-Methoxypyridoxine (4'-MPN), 4'-ethoxypyridoxine (4'-EPN), 4'-propoxypyridoxine (4'-PPN) and 4'-isopropoxypyridoxine (4'-isoPPN) were found to powerful inhibitors of PL-kinase and competed with pyridoxal (PL). There was a good relationship between mouse convulsions and inhibitory activities of PL-kinase. We also studied whether 4'-MPN, 4'-EPN, 4'-PPN and 4'-isoPPN were used as substrates of PL-kinase. High-performance liquid chromatography was used to separate 4'-PN 5'-phosphate analogues and ADP which were formed in the enzyme reaction, and to measure them quantitatively. The results showed that 4'-MPN, 4'-EPN, 4'-PPN and 4'-isoPPN were also phosphorylated by PL-kinase like 4'-deoxypyridoxine.

Chronic self-stimulation of the dentate nucleus for the relief of spasticity

It has been assumed but not yet proved that cerebellar cortical stimulation activates the Purkinje cells, with subsequent inhibition of the deep cerebellar nuclei. However, the relatively crude, widespread excitation induced by several surface electrode arrays and the parameters of stimulation currently used, may produce other effects than selective activation of only one specific cellular type which, furthermore, seems to be rarely present in these particular patients, as demonstrated by biopsy studies prior to electrode placement. The dentate nucleus was chronically implanted with a stimulating system in a patient with spasticity due to cerebral palsy. Chronic self-stimulation induced a significant improvement in motor function, with relief of spasticity and improvement in speech, posture, balance and gait. Electrophysiological studies demonstrated a decrease in the amplitude of V1 and V2 responses and in the H/M and T/M ratios, an increase in the silent period, and marked effects in the H reflex recovery curve, as well as diminished contralateral cortical somato-sensory evoked potentials. This result seems to indicate that the clinical effects of cerebellar cortical stimulation are not due to prosthetically induced inhibition of the dentate nucleus.

Prevulcanization Inhibitors

Conversion of raw rubber to a usable product is basically a three-step process. Crosslinking ingredients, fillers, and other components are added, the compounded green stock is shaped into the desired form, and the form is heated (cured) to introduce crosslinks (covalent bonds) between the rubber polymer chains and produce a three-dimensional network with vastly improved properties. The crosslinked product no longer flows and thus cannot be reprocessed. The curing system is activated by heat, heat is required for and generated by processing, and faster processing is desirable for economic reasons. Thus, a basic conflict exists between the processing and curing stages. The balance is delicate because the compounder, again for best economics, wants the product to cure rapidly after it is processed. Modern curing systems provide a scorch delay time, during which heating produces no crosslinks, followed by a period of rapid crosslink formation. The compounder then adjusts process conditions to provide enough heat history to eliminate most of the scorch delay so that the cure time will be minimized. Since the compounder is balancing processing against cure, subtle and sometimes uncontrollable changes in factory equipment or operating parameters can produce unprocessable (scorched) rubber stocks. Such changes can be compensated for by making adjustments in the curing system or in the processing conditions. However, relationships between curing system and properties are complex, and considerable effort is generally required to develop a new formulation. Thus, the need exists for an additive which increases only the scorch delay time with minimal effects on other cure parameters and vulcanizate properties. Such compounds, called prevulcanization inhibitors, scorch inhibitors, or retarders, are in commercial use. A number of papers and patents describing the chemistry and use of these compounds have been published and are reviewed here.

The Reaction of N,4-Dinitroso-N-Methylaniline and Polymers

Both nitroso groups participate in the reaction of N,4-dinitroso-N-methyl-aniline (DNMA) with various polymers, and the pathways of the reaction are influenced by the reaction conditions. In dilute solution the rate of the reaction is proportional to the amount of unsaturation present and is pseudo-first order with respect to DNMA at elevated temperature with or without polymers present. The iV-nitroso group undergoes thermal fission liberating nitroxyl and N-methyl-p-nitrosoaniline free radicals. The presence of hydrocarbons with labile hydrogen accelerates the hydrogen abstraction by the amine free radical to form N-methyl-p-nitrosoaniline and a hydrocarbon free radical, which may combine with another amine free radical to form a hydrocarbon with pendent N-substituted-N-methyl-p-nitrosoanilme group. The 4-nitroso group of DNMA adds to the double bond, leading to the formation of an adduct with N-methyl-N-nitroso-p-phenylenediamine pendent group. Depending on the reaction conditions, the 4-nitroso groups may form azoxy compounds or may be oxidized to nitro groups. The bifunctionality of DNMA leads to the formation of crosslinked polymers or to chemical promotion of carbon black reinforcement with N, N′-disubstituted-N-methyl-p-phenylenediamine type crosslinks.

Rubber Chemicals from Cyclic Amines. VII. Cycloalkylthioamines as Accelerators and Prevulcanization Inhibitors

Cycloalkylthioamines per se are moderately active accelerators. When used in conjunction with the benzothiazole accelerators, these thioamines act as prevulcanization inhibitors with cure activating properties, and generally, increase the crosslink density of the vulcanizates. The inhibition action of the cycloalkylthioamine may be due to its activity as a BtSH scavenger and also to its ability to reduce the number of the labile sulfur atoms, thereby the reactivity, of the more active polythiobenzothiazole intermediates. In addition to these capabilities the inhibition action of PVI in a benzothiazole sulfenamide-accelerated stock may be due to its ability to react with the free amine liberated during vulcanization. The relation of the curing properties of the cyclohexylthioamines to the structure of the amine moiety is analogous to the cases of dithiodiamines and 2-(imino)dithiobenzothiazoles as vulcanizing agents, or N-substituted-2-benzothiazole sulfenamides as accelerators. The relative curing properties either as accelerators or prevulcanization inhibitors can be attributed to the relative stability of the S-N bond based on the steric and electronic nature of the amine moiety. The cyclohexylthioamines derived from pyrrolidine and hexamethyleneimine are the most active as accelerators. The cyclohexylthioamine derived from the equally basic piperidine is slightly less active and gives significantly longer scorch delay. As a prevulcanization inhibitor the less basic morpholino and 2,6-dimethyimorpholino derivatives give much longer delayed action. The piperazine derivative is the most effective as a prevulcanization inhibitor.

Electron Impact-Induced Fragmentations of 2-Benzothiazole Sulfenamides and Related Compounds. Correlation with Rubber Vulcanization Activity

A correlation has been made between the activity of commercial rubber accelerators and vulcanizing agents and their mass spectral fragmentation patterns.

Rubber Chemicals from Cyclic Amines. IV. Thiocarbamyl Amine Disulfide Curing Agents

The cure properties of thiocarbamyl amine disulfide (I) as vulcanizing agents are influenced by the ionic and steric nature of both R and R′. The relative effects of various R and R′ are analogous to those of R and R′ in thiuram disulfides and dithioamines, respectively. However, the cure properties of I are dominated by the type of R rather than R′. Among the types of R investigated relatively longer scorch delay, slower cure rate and lower crosslink density are obtained, when R is morpholino or 3-azabicyclo(3.2.2)non-3-yl.

Rubber Chemicals from Cyclic Amines. VI. 2-(4-Morpholinodithio)Benzothiazole and Related Compounds as Curing Agents

Unlike the case of the thiazolesulfenamides, the electronic effect of substitution in the thiazole moiety on the curing properties of these compounds is not consistent. The unsubstituted 2-(4-morpholinodithio)benzothiazole 1 is superior to the 6-ethoxy, 5-chloro, or 6-nitro substituted derivatives in curing properties. The 5-ethoxycarbonyl-2-(morpholinodithio)-4-methylthiazole is comparable to 1 in scorch delay and curing activities. It is superior to the 5-acetyl and the unsubstituted 4-methyl thiazole derivatives. Both the benzoxazole and benzimidazole derivatives are inferior to the benzothiazole and 4-methyl thiazole analogs.