From peptides to small molecules: an intriguing but intricated way to new drugs.

A variety of peptides active in biological pathways have been identified e.g. receptor antagonists or inhibitors of protein-protein interactions and several peptide or peptide-derived compounds are on the drug market or in clinical trials. Through the rational design or the combinatorial preparation and High-throughput screening of arrays of compounds, peptides play a pivotal role for the rapid identification of ligands, but, despite these favorable properties, they often present poorer bioavailability and lower metabolic stability respect to traditional drugs. The process of conversion of a peptide in a small molecule provides the reduction of the peptide to the minimum active sequence (MAS) testing truncated peptides from the C- and N- termini alternatively. Then the influence of individual amino acid on the biological activity is determined by systematically replacing each residue in the peptide with specific amino acids. After structure-activity relationship (SAR) of each amino acid in the sequence has been assessed, the bioactive conformational flexibility is reduced by introducing constraints at various positions. These features are used for the design of a pharmacophore model in which functional groups crucial for activity are pre-positioned. Here we propose a panoramic review of the common principles for the conversion of peptides into small organic molecules and the most interesting findings in peptide-based leads of the last decades.

Triiodothyronine administration ameliorates the demyelination/remyelination ratio in a non-human primate model of multiple sclerosis by correcting tissue hypothyroidism.

Remyelination failure is a key landmark in chronic progression of multiple sclerosis (MS), the most diffuse demyelinating disease in human, but the reasons for this are still unknown. It has been shown that thyroid hormone administration in the rodent models of acute and chronic demyelinating diseases improved their clinical course, pathology and remyelination. In the present study, we translated this therapeutic attempt to experimental allergic encephalomyelitis (EAE) in the non-human primate Callithrix Jacchus (marmoset). We report that short protocols of triiodothyronine treatment shifts the demyelination/remyelination balance toward remyelination, as assessed by morphology, immunohistochemistry and molecular biology, and improves the clinical course of the disease. We also found that severely ill animals display hypothyroidism and severe alteration of deiodinase and thyroid hormone receptor mRNAs expression in the spinal cord, which was completely corrected by thyroid hormone treatment. We therefore suggest that thyroid hormone treatment improves myelin sheath morphology in marmoset EAE, by correcting the dysfunction of thyroid hormone cellular effectors.

Synthesis, characterization and hybridization studies of new nucleo-gamma-peptides based on diaminobutyric acid.

In the present work, we report the synthesis and the characterization of a new chiral nucleoaminoacid, in which a diaminobutyric moiety is connected to the DNA nucleobase by an amidic bond, and its oligomerization to give the corresponding nucleo-gamma-peptide. The ability of this synthetic polymer to bind complementary DNA was studied in order to explore its possible use in antigene/antisense or diagnostic applications. Our interest in the presented DNA analogue was also supported by the importance of gamma-aminoacid-containing compounds in natural products of biological activity and by the known stability of gamma-peptides to enzymatic degradation. Furthermore, our work could contribute to the study of the role of nucleopeptides as prebiotic material in a PNA world that could successively lead to the actual DNA/RNA/protein world, as recently assumed.

Endogenous stem and precursor cells for demyelinating diseases: an alternative for transplantation?

Remyelination can be very effective in human. However, this process ultimately fails in multiple sclerosis (MS). In this paper, we discuss the possibility of stimulating endogenous oligodendrocyte precursors to participate in remyelination in experimental models (rat and primate Callithrix jacchus) of MS through thyroid hormone (TH) administration. TH is in fact known to be a key signal in brain development, oligodendrocyte development and myelin protein gene expression regulation.

Behavioural and nociceptive response in male and female spiny mice (Acomyscahirinus) upon exposure to snake odour.

Predator cues (both mammalian odour or avian vocalizations) are known to elicit fear-associated responses in rodents, including analgesia. In previous studies it was reported that spiny mice fail to show fear responses when presented with the calls of an owl. In order to test the hypothesis that this species (living in semiarid and rocky areas) may react to stimuli coming from reptilian predators, 40 sexually mature spiny mice (20 males, 20 females) were individually exposed to a small cylinder containing either fresh sawdust or snake odour. Behavioural changes (5 min before and 15 min after odour exposure) as well as the subsequent performance in a hot-plate test (50±0.5°C) were assessed. Results indicate that exposure to the odour of a sympatric terrestrial predator affected both behavioural and physiological responses of spiny mice. Upon exposure to snake odour both sexes showed significant changes in the patterns of inactivity, sniffing, grooming, sniffing the stimulus object (SO), withdraw reaction and in the frequency of somersaults. However, males increased the frequency of rearing, sniffing the SO, decreasing grooming more than females. No analgesic effect of odour exposure emerged; however, males showed significantly shorter latencies and higher frequencies of hindpaw licking compared to females.

Acetylcholinesterase regeneration in mouse CNS studied by a microphotometric method.

Acetylcholinesterase (AChE) regeneration after single and repeated doses of diisopropylfluorophosphate (DFP) was investigated in neostriatum of central nervous system of Balb mice, by means of a microphotometric method. In the present study, three experimental groups received the following DFP treatments: group I was administered a single dose of 3 mg/kg; group II received weekly doses of 3 mg/kg for 9 weeks, and group III was exposed to 28 weekly treatments of 1 mg/kg, plus a last treatment of 3 mg/kg, for a total of 29 doses. The results of microphotometric analysis for all the experimental groups have shown a distinct reversibility pattern of DFP inhibition, consistent with the process of AChE regeneration. Nevertheless, one week following the last DFP treatment, a persisting difference (approximately 22%) in the AChE concentration between control and the experimental groups was observed. Based on our results and on the correlation reported in the literature between AChE reduction and muscarinic receptor density, the hazardous implications of organophosphate environmental contamination on human and animal health are pointed out.

Primate displacement activities as an ethopharmacological model of anxiety.

Using a within-subject cross-over, vehicle-controlled design, we investigated the acute effects of benzodiazepine receptor ligands with different mechanisms of action on the displacement activities (scratching, self-grooming, and body shake) of seven male macaques living in social groups. Our aim was to test the discriminative validity of displacement activities as an ethopharmacological model of anxiety. Subjects were given i.m. lorazepam (0.10, 0.20, 0.25 mg/ kg) and FG 7142 (0.1, 0.3, 1.0 mg/kg). The frequency of displacement activities was decreased by the anxiolytic lorazepam and increased by the anxiogenic FG 7142 in a dose-dependent manner. Displacement activities were apparently more sensitive to anxiolytic treatment than other behavior patterns indicative of an anxiety state (i.e., visual scanning of the social environment and fear responses directed to dominant males). These results suggest that primate displacement activities are a valid ethopharmacological model of anxiety.

Fetal tissue collection from spontaneous abortions: a report from a single centre.

Due to immunological immaturity, the fetus is the ideal recipient as well as donor of haemopoietic stem cells (HSCs); thus intrauterine therapy may prove to be effective in all major haemopoietic disorders when early prenatal diagnosis is available. In man, "fetus-to-fetus" transplantation has demonstrated the possibility of grafting donor HSCs and reconstituting immunodeficient fetuses. The limitations of fetal tissue use for transplantation derive from the origin of tissues from elective abortions. Early and late live spontaneous abortions may constitute an alternative to elective abortions, but are widely considered as unsuitable for fetal tissue collection because of rapid loss of viability and/or infections. The aim of this retrospective study was to assess the number of live abortions in a population of women who underwent spontaneous abortion in a single centre. In a 19-month period, 9 spontaneous abortions alive at the moment of delivery and 8 with a heart beat at the last ultrasound scan before abortion were recorded. In 1 case, fetal liver (FL) harvesting was easily performed and the tissue was cryopreserved, subsequently thawed and injected into a monkey fetus. This case shows the feasibility of this approach. The majority of cases reviewed consisted of late abortions. These findings clearly show that fetal tissue collection from spontaneous abortions is feasible for research purposes, for postnatal FL transplantation and for intrauterine transplantation, postnatal FL transplantation and for intrauterine transplantation, provided that depletion of more mature cells is performed when FL of later gestational age are used.(ABSTRACT TRUNCATED AT 250 WORDS)

The neuropathology of trimethyltin in the marmoset (Callithrix jacchus) hippocampal formation.

The effects of single and repeated doses of trimethyltin (TMT) treatment on the central nervous system (CNS) of the marmoset were investigated. For the acute-dose experiment adult animals were administered 3 mg/kg of TMT chloride (ip) and were then observed for changes in behavior. Within 24 hr postinjection all animals developed tremors, ataxia, and unresponsiveness. Half of the animals had severe clinical deterioration and died at 2 to 3 days following treatment. Surviving marmosets were sacrificed and the brain was subsequently perfusion-fixed for light microscopic examination. Neuronal degeneration was observed in many cells of the Ammon's horn and fascia dentata of the hippocampus. For the chronic-dose experiment, adult marmosets received (ip) weekly doses of 0.75 mg/kg of TMT chloride for 24 weeks. No evident clinical signs or behavioral changes were observed in any of the treated animals. Histological examination revealed neuropathological changes comparatively similar but less severe than those observed in the acute-treated animals. The differences in toxicity effects between acute and chronic TMT administration are compared and discussed.

Neuropathological and behavioral toxicology of trimethyltin exposure.

The most prominent neuropathological and behavioral changes induced by trimethyltin (TMT) in different mammalian species were reviewed. From the analysis of the reported literature it becomes evident that the neuropathological effects are selectively present in the limbic system structures. In particular, the granular neurons of the fascia dentata and the pyramidal cells of the Ammon's horn are involved, with a different pattern of severity and extension according to the various species studied and to the dosage-schedule used. The neurological damage produced by TMT to several limbic structures is related to overt behavioral changes. TMT acute exposure in adult rats produces a remarkable behavioral syndrome, consisting in tremors, spontaneous seizures, tail mutilation, vocalization, hyper-reactivity and intra-specific aggression. Impairments in learning and memory processes are also induced following acute treatment. Specific behavioral changes in various species reflect the different sensitivity and vulnerability to the chemical compounds. In addition, prenatal and postnatal exposure induce long-term behavioral and neurological effects on developing central nervous system.

The mossy fiber terminals in the hippocampal formation of Callithrix jacchus: comparative and evolutionary considerations.

The distribution of mossy fiber terminals in the regio inferior of the hippocampus of Callithrix jacchus was studied by means of Timm's method. The topographic distribution of Timm-positive zones in the hilus, in the suprapyramidal and intrapyramidal areas of the CA3 subfield is described. A Timm-positive reaction in intragranular strips and supragranular zones, the presence of Timm-negative zones in the infragranular border of the fascia dentata were found in this species. A comparison between mossy fiber distribution in Callithrix jacchus and that in human was carried out in an attempt to identify interspecies differences in the mossy fiber system in the hippocampus of primates. The hypothesis of a possible functional relevance of the supra- and intrapyramidal mossy fiber terminals on the control of hippocampal pyramidal neurons is expressed.

Normal serum biochemical and hematological parameters in Macaca fascicularis.

The effects of age, sex, pregnancy, were analyzed and data from fasted and fed animals were compared in a population of cynomolgus macaques. No significant sex effects were observed for biochemical values and no changes were found in male hematological parameters in relation to age. Most values of females during pregnancy were within normal ranges. Comparison between fed and fasted animals showed that several biochemical parameters (e.g., ALT, glucose, CPK, LDH) and several hematological parameters (e.g., monocytes, eosinophils, basophils, hemoglobin, MCV, MCHC, and MCH) were affected by food intake.

Measuring anxiety in nonhuman primates: effect of lorazepam on macaque scratching.

Lorazepam (0.2 mg/kg IM) was given to group-living female macaques to assess the effect of anxiolytic treatment on scratching, a behavior pattern referred to as a displacement activity in the primate literature. Lorazepam selectively diminished scratching behavior. The drug effect was status-dependent: especially low-ranking animals showed a marked reduction in scratching. Lorazepam exerted a direct effect on scratching, that is the effect was not due to sedation or mediated by the influence of the drug on other behaviors. These results provide pharmacological validation to the ethological finding that scratching may be a manifestation of anxiety in monkeys. In addition, they suggest to use scratching as a behavioral measure in studies investigating nonhuman primate models of anxiety.

Comparison of pharmacokinetics of sodium and lysine cephalexin in calves.

The pharmacokinetics of sodium and lysine cephalexins were investigated after intravenous and intramuscular administration of a single dose rate of 30 mg.kg-1 body weight in calves. The data for the two salts administered intravenously were pooled, the resulting pharmacokinetic disposition of cephalexin indicating a distribution half-time (t1/2 alpha) and an elimination half-time (t1/2 beta) of 9.78 and 62.0 min, respectively. Following intramuscular administration some pharmacokinetic differences were recorded between the cephalexin preparations: lysine cephalexin was more rapidly eliminated (t1/2kel = 55.2 min) than sodium cephalexin (t1/2kel = 89.8 min), although the peak blood level was higher and attained after a longer time with lysine cephalexin.