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At least 181 records · Page 10Linked to original sources
PubMed1983

A scanning electron microscope study of dentinal tubules from un-erupted human teeth.

Twelve fully-formed human third molars were obtained immediately after extraction, the roots removed, the crowns split into buccal and lingual portions fixed in Karnovsky solution and either left in the mineralized state or demineralized in a formic/citric acid solution. Specimens were dehydrated, critical point dried and examined by SEM. Demineralization of the teeth resulted in the loss of peritubular dentine and the appearance within each tubule of a sheet-like structure which extended from the predentine-dentine junction to the dentine-enamel junction. This sheet-like structure, here termed the lamina limitans, may play a role in the control of peritubular dentine formation.

Adult↗
PubMed1969

Mise en evidence de la formation d'un complexe ternaire entre trypsine, alpha(2)-macroglobuline et inhibiteur basique de pancreas.

The complex formed between trypsin and alpha(2)-macroglobulin retains the whole hydrolytic activity for benzoylarginine-p-nitroanilide (DL BAPNA). We have observed that the inhibition of this activity is dependent on the inhibitor used. While soya bean inhibitor (MW = 20 000) is ineffective, the basic pancreatic inhibitor (MW = 6 500) progressively inhibits the complex. In this latter case, we have observed the formation of a very weakly active ternary compound by two methods: kinetic and fluorescence polarization.Such differences suggest either that the contact site of trypsin for binding is not the same for each inhibitor or that the steric hindrance by macroglobulin prevents large inhibitors from reaching the active site. The pancreatic inhibitor can reach this site but its affinity is lower for the complex than for free trypsin.

Journal Article↗
PubMed1969

Mise en evidence d'une conformation stable d'un peptidolipide.

The Peptidolipide J (CH(3)-(CH(2))(n)-CO-D Phe-L Ile-L Ile-L Phe-L Ala-O-CH(3)) is obtained also in acidic form by a chromatographic artefact. In chloroformic solutions the ester and the acid behave in a very different way: the acid has a stable conformation, as shown by the infra-red spectra and the optical rotary dispersion; this conformation is stabilized by hydrogen bonding between two peptide chains associated as a carboxylic dimer.

Journal Article↗
PubMed1970

Un nouveau colorant fluorescent pour la mesure du temps de relaxation brownienne des proteines.

Several authors have described the NBD-chloride (7-chloro-4-nitrobenzo-2-oxa-1,3-diazole) as a fluorogenic reagent of the amino groups and the sulfhydryl groups. It reacts rapidly with the trypsin to produce a stable and highly fluorescent conjugate. The determination of the labelled residues was made with thin layer chromatographies; the lysin residues were preferentially labelled.Fluorescence depolarization measurements of the conjugate were used to determine the brownian relaxation of the enzyme. The temperature dependence of the life-time is very strong and the corrected Perrin's plot demonstrates that the relaxation time of the enzyme decreases rapidly with the temperature.The conclusion is that the NBD-chloride can be used, like the DNS-chloride but is more reactive and stable and its fixation, on trypsin can be followed by measuring the absorbance of the dye at 470 nm.

Journal Article↗
PubMed1971

Utilisation de la centrifugation analytique pour la mesure, au sein d'un extrait brut d'E. coli, du coefficient de sédimentation du complexe de décarboxylation oxidative du pyruvate.

We have applied successfully the active enzyme analytical centrifugation method (A.E.C.) to the study of the well known pyruvate dehydrogenase complex (P.D.C.) in crude extracts from E. coli. It is not possible to study the complex in a spectrophotometer (through its dehydrogenase activity) due to NADH oxidase activities. The A.E.C. method, which overcomes this difficulty, can also be viewed as a refined spectrophotometric method.

Journal Article↗
PubMed1992

Polyamine spider toxins are potent un-competitive antagonists of rat cortex excitatory amino acid receptors.

We examined the effect of argiopine and argiopinine 3, low molecular weight polyamine venom components of the spider Argiope lobata, on rat cortical excitatory amino acid (EAA) receptors expressed in Xenopus oocytes. Responses to 100 microM N-methyl-D-aspartate (NMDA) with 10 microM glycine were blocked by both of the polyamine toxins in a dose-dependent manner. Both compounds had similar potencies against 100 microM kainate or 50 microM (S)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (L-AMPA). Oscillatory responses to 2 microM quisqualate were unaffected by either polyamine toxin. Increasing concentrations of either NMDA, kainate or AMPA were unable to overcome the antagonism by either spider toxin. We were able to demonstrate a use-dependent phenomenon similar to that of phencyclidine; neither polyamine toxin affected the NMDA, kainate or AMPA response without the presence of the respective agonist.

Animals↗
PubMed2004

Genetic background, nature of event, and time of exposure to event direct the phenotypic expression of a particular genotype. A study with apomorphine-(un)susceptible Wistar rats.

The aim of this study was to investigate the differential long-term after-effects on the apomorphine-susceptibility in the apomorphine-susceptible (APO-SUS) and apomorphine-unsusceptible (APO-UNSUS) rats of either a saline injection (a mild stressor) or a clonidine-injection (a moderate stressor) applied around the onset of the stress-hypo-responsive-period (SHRP) on postnatal day (PND) 2, 4, 6 or 9. The present study shows that an injection of saline on PND 2 decreases the apomorphine-induced gnawing score in adult APO-SUS rats, but increases this score in adult APO-UNSUS rats; clonidine given on this day has no effect. An injection of saline on PND 4 decreases the apomorphine score in adult APO-SUS rats, but has no effect in adult APO-UNSUS rats. An injection of clonidine on PND 4 counteracts the long-term after-effects of a saline injection on this PND in adult APO-SUS rats, but has no effect in adult APO-UNSUS rats. Finally, an injection of clonidine on PND 9 has no effect on the apomorphine score in adult APO-SUS rats, but increases this score in adult APO-UNSUS rats; saline given on this day has no effect. It is concluded that the long-term after-effects of early postnatal stressors depend on the interrelationship between, rather than the separate impact of, the genetic background of the rat, the nature of the event, and time of exposure to the event, thereby implying that these factors direct the phenotypic expression of a particular genotype at adult age.

Adrenergic alpha-Agonists↗
PubMed2004

UN stalls on human cloning.

The United Nations postponed again a controversial vote on the issue of therapeutic cloning of human stem cells, hampering the widely supported opposition to reproductive cloning but many countries are developing their own legislation.

Cloning, Organism↗
PubMed2006

Antihelminthic activity of some newly synthesized 5(6)-(un)substituted-1H-benzimidazol-2-ylthioacetylpiperazine derivatives.

Piperazine derivatives of 5(6)-substituted-(1H-benzimidazol-2-ylthio)acetic acids were synthesized by using two methods and studied for antihelminthic activity. The antiparasitic screening showed that compounds 18-24 exhibited higher activity against Trichinella spiralis in vitro in comparison to methyl 5-(propylthio)-1H-benzimidazol-2-yl-carbamate (albendazole). Most active were compounds 2-({2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}thio)-1H-benzimidazole 21 and 2-{[2-oxo-2-(4-benzhydrylpiperazin-1-yl)ethyl]thio}-5(6)-methyl-1(H)-benzimidazole 19 as well as 2-({2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}thio)-5(6)-methyl-1(H)-benzimidazole 23 with efficacy of 96.0%, 98.4% and 100%, respectively. The tested derivatives 15-19 and 20-23 were less active against Syphacia obvelata in vivo than albendazole and exhibited the same efficacy as piperazine, but in twice lower concentration.Compounds 2-({2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}thio)-1H-benzimidazole 21, 1,4-bis[(5(6)-methyl-1(H)-benzimidazol-2-ylthio)acetyl]piperazine 17 and 2-({2-[4-(4-chlorophenyl)piperazin-1-yl]-2-oxoethyl}thio)-5(6)-methyl-1(H)-benzimidazole 23 had higher efficacies of 73%, 76%, and 77%, respectively.

Animals↗