Neurotensin Analogues Containing Cyclic Surrogates of Tyrosine at Position 11 Improve NTS2 Selectivity Leading to Analgesia without Hypotension and Hypothermia

Neurotensin (NT) exerts its analgesic effects through activation of the G protein-coupled receptors NTS1 and NTS2. This opioid-independent antinociception represents a potential alternative for pain management. While activation of NTS1 also induces a drop in blood pressure and body temperature, NTS2 appears to be an analgesic target free of these adverse effects. Here, we report modifications of NT at Tyr¹¹ to increase selectivity toward NTS2, complemented by modifications at the N-terminus to impair proteolytic degradation of the biologically active NT(8-13) sequence. Replacement of Tyr¹¹ by either 6-OH-Tic or 7-OH-Tic resulted in a significant loss of binding affinity to NTS1 and subsequent NTS2 selectivity. Incorporation of the unnatural amino acid β³hLys at position 8 increased the half-life to over 24 h in plasma. Simultaneous integration of both β³hLys⁸ and 6-OH-Tic¹¹ into NT(8-13) produced a potent and NTS2-selective analogue with strong analgesic action after intrathecal delivery in the rat formalin-induced pain model with an ED₅₀ of 1.4 nmol. Additionally, intravenous administration of this NT analogue did not produce persistent hypotension or hypothermia. These results demonstrate that NT analogues harboring unnatural amino acids at positions 8 and 11 can enhance crucial pharmacokinetic and pharmacodynamic features for NT(8-13) analogues, i.e., proteolytic stability, NTS2 selectivity, and improved analgesic/adverse effect ratio.

Site-Specific Radioactive Labeling of Nanobodies

Single-domain antibody fragments, also called nanobodies (Nbs), are increasingly being used as targeting molecular tools for imaging and/or targeted radionuclide therapy. To translate these tools to the clinic, it is preferred to obtain a homogeneous, well-defined, and well-characterized product. It has been shown that Sortase A, a transpeptidase found in Staphylococcus aureus, catalyzes the site-specific conjugation between a recognition oligopeptide (LPXTG, known as sortag) and an oligoglycine functionalized probe. This versatile technique manages to couple various molecular reagents, such as biotin, fluorophores, bifunctional chelators, etc., to the target protein containing the sortag. This chapter focuses on the site-specific coupling of a bifunctional chelator (e.g., CHX-A"-DTPA) to a Nb equipped with a C-terminal sortag. The chelator conjugated to the Nb can be radiolabeled with ¹¹¹In or ¹⁷⁷Lu for SPECT imaging or targeted radionuclide therapy, respectively.

Binding-Site Compatible Fragment Growing Applied to the Design of β2-Adrenergic Receptor Ligands

Fragment-based drug discovery is intimately linked to fragment extension approaches that can be accelerated using software for de novo design. Although computers allow for the facile generation of millions of suggestions, synthetic feasibility is however often neglected. In this study we computationally extended, chemically synthesized, and experimentally assayed new ligands for the β₂-adrenergic receptor (β₂AR) by growing fragment-sized ligands. In order to address the synthetic tractability issue, our in silico workflow aims at derivatized products based on robust organic reactions. The study started from the predicted binding modes of five fragments. We suggested a total of eight diverse extensions that were easily synthesized, and further assays showed that four products had an improved affinity (up to 40-fold) compared to their respective initial fragment. The described workflow, which we call "growing via merging" and for which the key tools are available online, can improve early fragment-based drug discovery projects, making it a useful creative tool for medicinal chemists during structure-activity relationship (SAR) studies.

Antimicrobial peptides in frog poisons constitute a molecular toxin delivery system against predators

Animals using toxic peptides and proteins for predation or defense typically depend on specialized morphological structures, like fangs, spines, or a stinger, for effective intoxication. Here we show that amphibian poisons instead incorporate their own molecular system for toxin delivery to attacking predators. Skin-secreted peptides, generally considered part of the amphibian immune system, permeabilize oral epithelial tissue and enable fast access of cosecreted toxins to the predator's bloodstream and organs. This absorption-enhancing system exists in at least three distantly related frog lineages and is likely to be a widespread adaptation, determining the outcome of predator-prey encounters in hundreds of species.

χ-Space Screening of Dermorphin-Based Tetrapeptides through Use of Constrained Arylazepinone and Quinolinone Scaffolds

Herein, the synthesis of novel conformationally constrained amino acids, 4-amino-8-bromo-2-benzazepin-3-one (8-Br-Aba), 3-amino-3,4-dihydroquinolin-2-one, and regioisomeric 4-amino-naphthoazepinones (1- and 2-Ana), is described. Introduction of these constricted scaffolds into the N-terminal tetrapeptide of dermorphin (i.e., H-Tyr-d-Ala-Phe-Gly-NH₂) induced significant shifts in binding affinity, selectivity, and in vitro activity at the μ- and δ-opioid receptors (MOP and DOP, respectively). A reported constrained μ-/δ-opioid lead tetrapeptide H-Dmt-d-Arg-Aba-Gly-NH₂ was modified through application of various constrained building blocks to identify optimal spatial orientations in view of activity at the opioid receptors. Interestingly, when the aromatic moieties were turned toward the C-terminus of the peptide sequences, (partial) (ant)agonism at MOP and weak (ant)agonism at DOP were noticed, whereas the incorporation of the 1-Ana residue led toward balanced low nanomolar MOP/DOP binding and in vitro agonism.

Rational Design of Nanobody80 Loop Peptidomimetics: Towards Biased β2 Adrenergic Receptor Ligands

G protein-coupled receptors (GPCRs) play an important role in many cellular responses; as such, their mechanism of action is of utmost interest. To gain insight into the active conformation of GPCRs, the X-ray crystal structures of nanobody (Nb)-stabilized β₂ -adrenergic receptor (β₂ AR) have been reported. Nb80, in particular, is able to bind the intracellular G protein binding site of β₂ AR and stabilize the receptor in an active conformation. Within Nb80, the complementarity-determining region 3 (CDR3) is responsible for most of the binding interactions. Hence, we hypothesized that peptidomimetics of the CDR3 loop might be sufficient for binding to the receptor, inhibiting the interaction of β₂ AR with intracellular GPCR interacting proteins (e.g., G proteins). Based on previous crystallographic data, a set of peptidomimetics were synthesized that, similar to the Nb80 CDR3 loop, adopt a β-hairpin conformation. Syntheses, conformational analysis, binding and functional in vitro assays, as well as internalization experiments, were performed. We demonstrate that peptidomimetics can structurally mimic the CDR3 loop of a nanobody and its function by inhibiting G protein coupling as measured by partial inhibition of cAMP production.

Ethylene and auxin interaction in the control of adventitious rooting in Arabidopsis thaliana

Adventitious roots (ARs) are post-embryonic roots essential for plant survival and propagation. Indole-3-acetic acid (IAA) is the auxin that controls AR formation; however, its precursor indole-3-butyric acid (IBA) is known to enhance it. Ethylene affects many auxin-dependent processes by affecting IAA synthesis, transport and/or signaling, but its role in AR formation has not been elucidated. This research investigated the role of ethylene in AR formation in dark-grown Arabidopsis thaliana seedlings, and its interaction with IAA/IBA. A number of mutants/transgenic lines were exposed to various treatments, and mRNA in situ hybridizations were carried out and hormones were quantified In the wild-type, the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) at 0.1 μM enhanced AR formation when combined with IBA (10 μM), but reduced it when applied alone; this effect did not occur in the ein3eil1 ethylene-insensitive mutant. ACC inhibited the expression of the IAA-biosynthetic genes WEI2, WEI7, and YUC6, but enhanced IBA-to-IAA conversion, as shown by the response of the ech2ibr10 mutant and an increase in the endogenous levels of IAA. The ethylene effect was independent of auxin-signaling by TIR1-AFB2 and IBA-efflux by ABCG carriers, but it was dependent on IAA-influx by AUX1/LAX3.Taken together, the results demonstrate that a crosstalk involving ethylene signaling, IAA-influx, and IBA-to-IAA conversion exists between ethylene and IAA in the control of AR formation.

Sortase A-mediated site-specific labeling of camelid single-domain antibody-fragments: a versatile strategy for multiple molecular imaging modalities

A generic site-specific conjugation method that generates a homogeneous product is of utmost importance in tracer development for molecular imaging and therapy. We explored the protein-ligation capacity of the enzyme Sortase A to label camelid single-domain antibody-fragments, also known as nanobodies. The versatility of the approach was demonstrated by conjugating independently three different imaging probes: the chelating agents CHX-A"-DTPA and NOTA for single-photon emission computed tomography (SPECT) with indium-111 and positron emission tomography (PET) with gallium-68, respectively, and the fluorescent dye Cy5 for fluorescence reflectance imaging (FRI). After a straightforward purification process, homogeneous single-conjugated tracer populations were obtained in high yield (30-50%). The enzymatic conjugation did not affect the affinity of the tracers, nor the radiolabeling efficiency or spectral characteristics. In vivo, the tracers enabled the visualization of human epidermal growth factor receptor 2 (HER2) expressing BT474M1-tumors with high contrast and specificity as soon as 1 h post injection in all three imaging modalities. These data demonstrate Sortase A-mediated conjugation as a valuable strategy for the development of site-specifically labeled camelid single-domain antibody-fragments for use in multiple molecular imaging modalities. Copyright © 2016 John Wiley & Sons, Ltd.

Dual Alleviation of Acute and Neuropathic Pain by Fused Opioid Agonist-Neurokinin 1 Antagonist Peptidomimetics

Herein, the synthesis and biological evaluation of dual opioid agonists-neurokinin 1 receptor (NK1R) antagonists is described. In these multitarget ligands, the two pharmacophores do not overlap, and this allowed maintaining high NK1R affinity and antagonist potency in compounds 12 and 13. Although the fusion of the two ligands resulted in slightly diminished opioid agonism at the μ- and δ-opioid receptors (MOR and DOR, respectively), as compared to the opioid parent peptide, balanced MOR/DOR activities were obtained. Compared to morphine, compounds 12 and 13 produced more potent antinociceptive effects in both acute (tail-flick) and neuropathic pain models (von Frey and cold plate). Similarly to morphine, analgesic tolerance developed after repetitive administration of these compounds. To our delight, compound 12 did not produce cross-tolerance with morphine and high antihyperalgesic and antiallodynic effects could be reinstated after chronic administration of each of the two compounds.

Structural basis for bifunctional peptide recognition at human δ-opioid receptor

Bi-functional μ- and δ- opioid receptor (OR) ligands are potential therapeutic alternatives to alkaloid opiate analgesics with diminished side effects. We solved the structure of human δ-OR bound to the bi-functional δ-OR antagonist and μ-OR agonist tetrapeptide H-Dmt(1)-Tic(2)-Phe(3)-Phe(4)-NH₂ (DIPP-NH₂) by serial femtosecond crystallography, revealing a cis-peptide bond between H-Dmt(1) and Tic(2). The observed receptor-peptide interactions are critical to understand the pharmacological profiles of opioid peptides, and to develop improved analgesics.

One-pot isomerization-cross metathesis-reduction (ICMR) synthesis of lipophilic tetrapeptides

An efficient, versatile and rapid method toward homologue series of lipophilic tetrapeptide derivatives (herein, the opioid peptides H-TIPP-OH and H-DIPP-OH) is reported. High atom economy and a minimal number of synthetic steps resulted from a one-pot tandem isomerization-cross metathesis-reduction sequence (ICMR), applicable both in solution and solid phase methodology. The broadly applicable synthesis proceeds with short reaction times and simple work-up, as illustrated in this work for alkylated opioid tetrapeptides.

In Vitro Membrane Permeation Studies and in Vivo Antinociception of Glycosylated Dmt1-DALDA Analogues

In this study the μ opioid receptor (MOR) ligands DALDA (Tyr-d-Arg-Phe-Lys-NH₂) and Dmt¹-DALDA (Dmt-d-Arg-Phe-Lys-NH₂, Dmt = 2',6'-dimethyltyrosine) were glycosylated at the N- or C-terminus. Subsequently, the modified peptides were subjected to in vitro and in vivo evaluation. In contrast to the N-terminally modified peptide (3), all peptide analogues derivatized at the C-terminus (4-7) proved to possess high affinity and agonist potency at both MOR and DOR (δ opioid receptor). Results of the Caco-2 monolayer permeation, as well as in vitro blood-brain barrier model experiments, showed that, in the case of compound 4, the glycosylation only slightly diminished the lumen-to-blood and blood-to-lumen transport. Altogether, these experiments were indicative of transcellular transport but not active transport. In vivo assays demonstrated that the peptides were capable of (i) crossing the blood-brain barrier (BBB) and (ii) activating both the spinal ascending as well as the descending opioid pathways, as determined by the tail-flick and hot-plate assays, respectively. In contrast to the highly selective MOR agonist Dmt¹-DALDA 1, compounds 4-7 are mixed MOR/DOR agonists, expected to produce reduced opioid-related side effects.

Variation of the net charge, lipophilicity, and side chain flexibility in Dmt(1)-DALDA: Effect on Opioid Activity and Biodistribution

The influence of the side chain charges of the second and fourth amino acid residues in the peptidic μ opioid lead agonist Dmt-d-Arg-Phe-Lys-NH(2) ([Dmt(1)]-DALDA) was examined. Additionally, to increase the overall lipophilicity of [Dmt(1)]-DALDA and to investigate the Phe(3) side chain flexibility, the final amide bond was N-methylated and Phe(3) was replaced by a constrained aminobenzazepine analogue. The in vitro receptor binding and activity of the peptides, as well as their in vivo transport (brain in- and efflux and tissue biodistribution) and antinociceptive properties after peripheral administration (ip and sc) in mice were determined. The structural modifications result in significant shifts of receptor binding, activity, and transport properties. Strikingly, while [Dmt(1)]-DALDA and its N-methyl analogue, Dmt-d-Arg-Phe-NMeLys-NH(2), showed a long-lasting antinociceptive effect (>7 h), the peptides with d-Cit(2) generate potent antinociception more rapidly (maximal effect at 1h postinjection) but also lose their analgesic activity faster when compared to [Dmt(1)]-DALDA and [Dmt(1),NMeLys(4)]-DALDA.

Characterizing Ionic Liquids as Reaction Media through a Chemical Probe

The triplet N,N-dimethylaminophenyl cation, a highly reactive but chemospecific electrophile, has been used as a probe for characterizing the properties of reaction media for a series of imidazolium ILs. With the N-hexyl-N-methyl imidazolium derivatives (not with the N-butyl analogues), hydrogen transfer leading to the aniline was the main process. Trapping by iodide occurred with an inverse dependence on viscosity. Trapping by pi nucleophiles exhibited a more complex behavior. This was explained by the effect of both the bulk viscosity and the structure of the IL cation on both steps of the reaction, namely, initial electrophilic attack and ensuing cation elimination or nucleophile addition. However, with an excellent nucleophile, such as thiophene, or when the latter step was intramolecular, as with 4-pentenol, the difference was obliterated and trapping became uniform. Incorporation of the probe into the IL cation (through insertion into the C--H bond alpha to the imidazolium ring) was demonstrated, while no addition to the anion tested (including bis(trifluoromethanesulfonimide)) took place.

Evaluation of DNA damage in leukocytes of ex-smokers by single cell gel electrophoresis

Single cell gel electrophoresis (SCGE), or comet assay, appears to be a promising tool to estimate DNA damage at the single cell level and it provides information on the presence of damage among individual cells. A follow-up study of 90 smokers who ceased smoking was undertaken to determine the possible decrease of DNA damage in their leukocytes. Before beginning the trial, volunteers smoked on average 26.1 +/- 8.4 cigarettes/day. Comet length did not correlate with the number of cigarettes/day or with the condensate tar content. At the end of the study, 28 volunteers had abandoned the trial, 40 volunteers relapsed into smoking at different times, but with a reduced number of cigarettes/day, whereas 22 fully succeeded in smoking cessation. Throughout the 5 sampling times, a great variability of comet length at individual level was found. However, after 1 year of follow-up, comet length means were found to be significantly shorter (p < 0.0001) in those volunteers who completely quit smoking compared to those who relapsed into smoking (27.2 +/- 1.6 vs. 31.9 +/- 5.1 microns, respectively), irrespective of the amount of cigarettes previously smoked. No effect of age or sex was found. Six months later, these results were confirmed by a further study carried out on a reduced sample of volunteers. The present data strongly suggest that, in spite of the great variability observed, 1 year of smoking cessation is associated with a significant reduction of DNA damage in circulating leukocytes.

Upper gastrointestinal motor abnormalities in children with active celiac disease

Although from the clinical point of view a GI motor disorder can be suspected in celiac disease, objective evidence for this is still lacking. We therefore conducted a study on children with active celiac disease to detect possible GI motor abnormalities in this disease. Fourteen children (age range, 1-13 years) were studied; they underwent fasting and fed manometric recordings in the gastroduodenojejunal area. Four patients were restudied after a 6-month gluten-free diet. Data were compared with those obtained in eight control children. As compared with controls, celiac disease patients showed a shorter duration of activity fronts (p < 0.01) and a significant (p < 0.01) reduction of the postprandial antral motility index; furthermore, > 90% of the patients displayed marked fasting and/or fed motor abnormalities, suggesting a neuropathic disorder. Interestingly, gut dysmotilities disappeared in the four subjects reassessed after the gluten-free diet. It is concluded that celiac disease frequently affects the motor behavior of the gut and that its effects may be reversed by appropriate diet.

Comparative studies by comet test and SCE analysis in human lymphocytes from 200 healthy subjects

The comet test (single cell gel electrophoresis, SCGE) appears to be a promising tool to estimate DNA damage at the single cell level and it provides information on the presence of damage among individual cells. Previously, we analyzed the degree of DNA damage in peripheral human lymphocytes from 100 healthy subjects living in Pisa (Italy) taking into account age, gender and smoking habit, and we also reported some results aiming at the assessment of the comet test (Betti el al., 1994). In addition, SCE analysis was carried out in order to compare the two endpoints. Because of the interesting results obtained, the present study was extended to 200 individuals, and data analyzed included information concerning number of cigarettes smoked a day, tar/cigarette and job. Data obtained confirmed that the SCGE is more sensitive than SCE in revealing smoking habit effects but comet induction did not seem to be related to the amount of cigarette tar inhaled. Moreover, sampling time was found to play a greater role in the comet assay as compared to SCE. Job position did not significantly influence SCE mean/subject or comet length mean/subject.

Micronucleus test and metaphase analyses in mice exposed to known and suspected spindle poisons

Micronucleus (Mn) and metaphase chromosome analyses were performed in mouse bone marrow cells with two known and eight suspected mitotic spindle poisons. Polychromatic (PCEs) and normochromatic (NCEs) erythrocytes were scored for presence of Mn, while structural (CAs) and numerical chromosome aberrations (NCAs), i.e. hyperploid cells, were evaluated by metaphase analysis. CAs were scored in first, and NCAs in the second metaphases, identified by BrdUrd differential staining. Hydroquinone induced Mn, NCAs and CAs; colchicine, vinblastine and, to a lesser extent, chloral hydrate, diazepam and econazole induced both Mn and NCAs; cadmium chloride and thimerosal induced Mn and CAs, while pyrimethamine and thiabendazole induced Mn only. The proposed stepwise protocol allowed satisfactory statistical evaluation of the effects induced with a reduction in the number of animals killed. An acceptable agreement was found between induction of Mn and NCAs, suggesting a possible use of the Mn test for revealing compounds with aneugenic properties.

Effect of erythromycin administration on upper gastrointestinal motility in scleroderma patients

BACKGROUND

Gastrointestinal involvement is frequent in patients with scleroderma. Erythromycin, a macrolide antibiotic, has been shown to accelerate gastric emptying in normal subjects and diabetic patients. The present study investigated the effects of acute erythromycin administration on gastric and gallbladder motility in patients with scleroderma and gastrointestinal involvement.

METHODS

Twelve scleroderma patients and 14 healthy subjects were investigated. Each subject was investigated on 4 different days. Gastric and gallbladder emptying and gastric motility were determined by sonography and manometry, and the effect of 2 mg/kg/h erythromycin in fasted patients or after semisolid meal evaluated.

RESULTS

The half-time of gastric emptying in response to semisolid meal was 121.3 +/- 14.0 min (SE) in scleroderma patients and 45.7 +/- 10.4 min in healthy subjects (P < 0.01). The peak of gallbladder emptying occurred later in scleroderma patients (95.0 +/- 5.0 min) than in healthy subjects (45.0 +/- 8.0 min) (P < 0.01). Erythromycin stimulated gastric and gallbladder motility in fasted subjects, as shown by manometry and sonography, and accelerated gastric and gallbladder emptying when administered immediately before the meal (P < 0.01).

CONCLUSIONS

Erythromycin accelerates gastric and gallbladder emptying in scleroderma patients and might be helpful in the treatment of gastrointestinal motor abnormalities in these patients.

Abnormal gastrointestinal motility in patients with celiac sprue

No study to date has objectively investigated whether the motor behavior of the small bowel is abnormal in celiac sprue. The purpose of this study was to systematically address this topic by means of intraluminal pressure recordings in a series of such patients. Sixteen subjects (nine adults, seven children, age range 2-69 years) with celiac sprue were recruited and studied while untreated. Manometric examination was carried out for 6 hr during fasting and 3 hr after a meal. Adult celiac patients displayed a significantly (mean +/- SEM) greater frequency of migrating motor complexes in comparison to controls during fasting (4.44 +/- 1.6 vs 2.45 +/- 0.20, P < 0.01), whereas no differences were found in the pediatric group with respect to this variable. Fasting motor abnormalities, chiefly represented by discrete clustered contractions, giant jejunal contractions, and bursts of nonpropagated contractions, were discovered in a high percentage in both groups of celiac subjects (89% in adults and 44% in children, respectively). Similar abnormalities were observed in the postprandial period, especially in adults. In conclusion, patients with celiac sprue frequently display discrete gastrointestinal motor abnormalities, which though perhaps nonspecific may account for several symptoms complained of by such patients.

Anorectal manometric abnormalities and colonic propulsive impairment in patients with severe chronic idiopathic constipation

Idiopathic chronic constipation is a frequent and disabling symptom, but its pathophysiological grounds are still poorly understood. In particular, there is little knowledge about the relationships between distal (anorectal area) and proximal (colonic area) motor abnormalities in this condition, especially concerning high-amplitude propagated colonic activity. For this purpose, we studied 25 patients complaining of severe idiopathic constipation and categorized them as normal- or slow-transit constipation according to colonic transit time. Twenty-five age-matched controls were also studied. Investigations included standard anorectal motility testing and prolonged (24-hr) colonic motility studies. Analysis of results showed that both groups of constipated patients displayed significantly different (P < 0.05) minimum relaxation volumes of the internal anal sphincter, defecatory sensation thresholds, and maximum rectal tolerable volumes with respect to controls. Patients with normal-transit constipation also showed lower internal anal sphincter pressure with respect to slow-transit constipation and controls (P < 0.001 and P < 0.02, respectively). The daily number of high-amplitude propagated contractions (mass movements) as well as their amplitude and duration, was significantly reduced in both subgroups of constipated patients (P < 0.02 vs controls). We conclude that (1) in normal-transit constipation, motor abnormalities are not limited to the anorectal area; (2) patients with slow-transit constipation probably have a severe neuropathic rectal defect; (3) prolonged colonic motility studies may highlight further the functional abnormalities in constipated subjects; and (4) an approach taking into account proximal and distal colon motor abnormalities might be useful to understand pathophysiological grounds of chronic constipation and lead to better therapeutic approaches.

Microgel electrophoresis assay (comet test) and SCE analysis in human lymphocytes from 100 normal subjects

Microscopic examination of individual human lymphocytes embedded in agarose, subjected to electrophoresis and stained with a fluorescent DNA-binding dye, provides a novel way of measuring DNA damage as extent of migration of DNA fragments, mainly single-strand breaks. With this relatively simple method, DNA damage arising as a consequence of smoking, age and other factors was examined in peripheral human lymphocytes from 100 healthy individuals living in Pisa (Italy). The extent of DNA migration was found to be significantly increased by smoking. It is noteworthy that the effect of smoking was more significant in men than in women and that DNA migration was similar in the young and in the older people. SCE analysis did not reveal any significant effect of smoking, sex or age in the same population, suggesting a higher responsiveness of the comet test to DNA-damaging agents.

Impaired colonic motor response to cholinergic stimulation in patients with severe chronic idiopathic (slow transit type) constipation

Chronic idiopathic constipation, especially the slow transit type, is a troubling problem often afflicting young women. The pathophysiological basis for this entity is unknown, although a defective cholinergic innervation has been postulated. We tested the hypothesis that cholinergic colonic innervation is deranged in this condition by studying colonic motor activity after strong cholinergic stimulation with edrophonium chloride in 14 women complaining of slow transit constipation. Unlike healthy subjects, constipated patients showed minimal or no response to edrophonium injection. It is concluded that in slow transit constipation there is an important alteration of colonic cholinergic activity and that edrophonium chloride may represent a useful test drug for colonic pathophysiological investigations.

Liquid holding effects on methylmercury genotoxicity in human lymphocytes

Methylmercury chloride (MMC) treatment of resting (G0) human lymphocytes resulted in the formation of chromosome and chromatid aberrations. This treatment also induced aneuploidy in second metaphases, suggesting that MMC produces stable damage involved in chromosome segregation errors. The storage of treated cells (liquid holding for 48 h before cell proliferation) did not result in an important recovery from induced cell toxicity or chromosome damage. Therefore, MMC seems to be an X-ray-like agent, able to produce long-lasting damages giving rise to both structural and numerical chromosome abnormalities.

Comparative studies on cytotoxic and genotoxic effects of two organic mercury compounds in lymphocytes and gastric mucosa cells of Sprague-Dawley rats

Human lymphocytes (HL) as well as lymphocytes (RL), hepatocytes (RH), and gastric mucosa cells (GM) of Sprague-Dawley rats were treated in vitro for 1 h with methylmercury chloride (MMC, 0.5-4 micrograms/ml) and dimethylmercury (DMM, 5-40 micrograms/ml). The cytotoxicity of the two organic mercury compounds was assessed by dye exclusion, and the extent of induced DNA fragmentation was measured with a single-cell microgel electrophoresis assay. Both MMC and DMM induced DNA damage and cytotoxicity in a dose-related manner in HL, RL, and GM. MMC was more effective in causing a significant increase in median DNA migration than DMM at doses yielding approximately the same degree of cytotoxicity. In rat hepatocytes the MMC-induced DNA damage was, however, lower than in the other cells. An analysis of repair kinetics following exposure to 2 micrograms/ml MMC was carried out in human lymphocytes obtained from an adult male donor. The bulk of DNA repair occurred 90 min after in vitro exposure, and it was about complete by 120 min following cessation of exposure. Finally, in order to have a basis for extrapolating to the human situation, in vivo studies were performed with Sprague-Dawley rats, also assessing the DNA damage and cytotoxicity in the lymphocytes and gastric mucosa cells. These in vivo results after oral exposure may be directly compared to the in vitro data obtained in the same cells.

Genotoxic activity of methyl mercury chloride and dimethyl mercury in human lymphocytes

The genotoxicity of methyl mercury chloride (MMC, 0-25 x 10(-6) M) and dimethyl mercury (DMM, 0-434 x 10(-6) M) was evaluated by chromosome metaphase analysis in human lymphocytes treated in vitro for 24 h. Structural (CA) and numerical (AN) chromosomal aberrations were scored for the assessment of induced genotoxic effects, while the variation in mitotic index (MI) was considered a monitor for induced cellular toxicity. MMC induced CA and AN in a dose-related manner at doses exceeding 0.6 x 10(-6) M, and the proportion of cells with CA was constantly and significantly higher than that of cells with AN. DMM was able to induce both effects as well, although to a lesser extent than MMC, CA and AN being induced at doses exceeding 43.4 x 10(-6) M and 1.73 x 10(-6) M, respectively. MMC was 6-fold more effective in inducing CA than DMM at equivalent toxic doses. On the other hand, no significant difference was observed between the two compounds in inducing AN. Therefore MMC was much more clastogenic than DMM, whereas mitotic spindle disturbances appeared to be almost equally induced by both compounds.

Impaired colonic motor response to eating in patients with slow-transit constipation

Because little is known about the pathophysiological mechanisms responsible for chronic idiopathic constipation, we studied colon motor response to eating, one of the most physiological and reproducible stimuli, in a clinically homogeneous group of severely constipated subjects. Fifteen patients (14 women, one man) with slow transit constipation (average duration of symptoms 18 +/- 2 yr) entered the study. After colonoscopic positioning of a manometric probe, 2-h basal and 3-h postprandial (1000 kcal standard mixed meal) recordings were obtained. Comparison of tracings with those of 29 healthy volunteers showed that motor response to eating was decreased in constipated subjects. Patients' response was characterized by a shorter duration of contractile activity in all three colon segments studied, after ingestion of the meal, and significantly less high-amplitude propagated contractions (7% vs. 45%). We conclude that several mechanisms are involved in the pathophysiology of colon contractile motor function of patients with chronic idiopathic constipation.

Extensive investigation on colonic motility with pharmacological testing is useful for selecting surgical options in patients with inertia colica

Three women with idiopathic severe chronic constipation and inertia colica, who failed to respond to medical treatment, were extensively investigated for gut motor function, especially that of the colon. Twenty-four-hour manometric recordings disclosed that motility was severely reduced throughout the entire colon and response to eating was minimal. One of the patients also was tested for esophageal, gastric, and small bowel motor activity, which gave normal results. Edrophonium chloride stimulation (10 mg iv) provoked no increase in colonic contractile activity in any patient. On these grounds, the patients were submitted to surgical intervention (total colectomy with ileorectal anastomosis two, and left hemicolectomy the other) with fairly good results at follow-up. These results indicate the wisdom of carrying out extensive functional investigations in severely constipated patients before surgery is contemplated.

Prolonged manometric investigation of the colon in research on chronic constipation

We studied the whole colonic motility for 24 hours in controls and in constipated patients. In the patient group we found a significant reduction in the colonic mass movements (6.1 +/- 0.9 vs 2.6 +/- 0.7 controls vs patients, respectively). The constipated patients showed a reduction of the colonic motor activity after the ingestion of a standard meal. Moreover, they showed, compared with controls, a significant reduction of postprandial mass movements. On the other hand we were not able to find the so-called rectal motor complex described by others. In conclusion, we believe that prolonged colonic manometry would become an important step when evaluating the pathophysiology of constipated patients, particularly of those not responding to standard treatment.

Effects of parenteral diclofenac sodium on upper gastrointestinal motility after food in man

In experimental animal models nonsteroidal anti-inflammatory drugs may influence gastrointestinal motility, but as evidence is lacking in man. The effect of diclofenac sodium 75 mg i.m. on the motor response of the upper gastrointestinal tract to food has been studied by manometry in 9 healthy volunteers. Diclofenac had no effect on the motor activity of the stomach, duodenum, or jejunum after a 605 kcal meal.

Edrophonium chloride for testing colonic contractile activity in man

The effects of cholinergic stimulation on the entire human colon are at present relatively unknown. For this reason, we evaluated the influence of a short-lived anticholinesterase agent, edrophonium chloride, on proximal and distal colonic contractile activity in man. Eight healthy volunteers of both sexes were studied with a multi-lumen manometric probe positioned with the aid of a colonoscope. Recordings were then obtained 30 minutes pre- and post-drug administration. Edrophonium chloride (10 mg intravenous) significantly stimulated both proximal and distal colonic contractile activity, and the maximum increase was observed within 10 minutes following injection, although some differences were observed between colonic segments in response to the drug. No important side effects were complained of after edrophonium. Due to the potent stimulatory property on colonic smooth muscle, to its short duration of action, and to the paucity of side effects, it is concluded that edrophonium chloride may be useful as a stimulating substance during manometric investigations of the human colon.

Prolonged (24-hour) manometric recording of rectal contractile activity in patients with slow transient constipation

A periodic motor activity, named the rectal motor complex, has been recently described in the healthy human rectum. We studied the rectal contractile activity for 24 h by a low compliance manometric system in a group of 10 women with slow transit constipation. Analysis of the 24-hour manometric recordings showed that these subjects: (1) had overall scarce rectal motility; (2) display few rectal motor complexes (average, 3.3 +/- 1.3/subject/24 h) which are irregularly distributed over time, and (3) respond weakly to ingestion of a standard meal (average duration of the motor response 19 +/- 6 min). The observations suggest that an underlying neuropathic process may be involved in the pathogenesis of the impaired rectal motility in patients with slow transit constipation.

Manometric evaluation of jejunal limb after total gastrectomy and Roux-Orr anastomosis for gastric cancer

Total gastrectomy with Roux-Orr anastomosis is frequently performed for gastric cancer. Since intestinal motility of the Roux limb has never been evaluated after this operation, pressure activity was investigated in the Roux limb of ten patients (aged 51-77 years) who had undergone total gastrectomy and Roux-Orr reconstruction. Investigations were carried out during a 6-h fast and 3 h after a 605 kcal mixed meal. During fasting only two patients had activity fronts and these were abnormal. All ten patients displayed non-propagating bursts of contractions and three had discrete clustered contractions and high amplitude jejunal contractions. The fed state was characterized by a severely reduced motor activity pattern and other abnormalities. Total gastrectomy with Roux-Orr anastomoses provokes a relatively severe disturbance in intestinal activity.

[Changes in upper gastrointestinal motility during scleroderma]

Scleroderma (progressive systemic sclerosis) is a systemic collagen disease in which the upper gut is frequently involved. In particular, most patient show altered esophageal motility, which frequently result in severe esophagitis, often resistant to therapeutic measures. The small bowel is also frequently involved by the disease, especially in the late stage of scleroderma. Small bowel alterations are sometimes clinically silent, but can also be the origin of malabsorption syndrome, small intestine perforation, pneumatosis cystoides or chronic intestinal pseudo-obstruction. The occurrence of an altered gastrointestinal motility in scleroderma can be detected by means of manometric techniques; their use in the wide area of collagenopathies may help understanding the pathophysiology of the altered gastrointestinal function frequently existing in these diseases.

Genotoxicity of two metabolites of benzene: phenol and hydroquinone show strong synergistic effects in vivo

Possible interactions between hydroquinone (HQ) and phenol (PHE), 2 known benzene metabolites, in inducing micronuclei in mouse bone marrow cells were investigated. HQ and PHE administered alone gave weak and negative results, respectively, at the doses tested. However, simultaneous administration of both compounds caused a considerable increase in the induction of micronuclei as well as an increase in bone marrow toxicity. Using 3 different statistical methods, it was shown that the observed joint effect was significantly higher than additive interaction, and was close to multiplicative interaction. These findings bring further support to the hypothesis that the toxic and genotoxic effects of benzene are produced by several metabolites acting synergistically.

Colonic motor response to eating: a manometric investigation in proximal and distal portions of the viscus in man

The motor response of the human colon to a meal is still poorly characterized. Such data as are available were obtained chiefly for the distal colonic portions with myoelectrical techniques. For these reasons, we investigated proximal and distal colonic motor responses to food ingestion in a rather large group of healthy subjects. Twenty-nine healthy volunteers were studied with a colonoscopically positioned multilumen manometric probe and low-compliance infusion system. Recordings were obtained for 2 h during fasting and for 3 h after the subjects had eaten a 1000-kcal standard mixed meal. During fasting, motility was quite low, and no significant differences between proximal and distal portions were seen. After eating, each portion significantly increased its motor activity throughout the subsequent recording period, but there were differences in the time course in the response to eating for different colonic segments. Proximal portions (especially the transverse colon) had first a sudden maximal increase and then a decrease, whereas the distal ones had a slower and more sustained increase in activity. These findings are of interest, especially for comparison with those of patients with suspected motor dysfunction of the large bowel.

Manometric evaluation of cimetropium bromide activity in patients with the nutcracker oesophagus

There are at present few therapeutic alternatives to calcium channel blockers for the medical treatment of patients with nutcracker oesophagus. For this reason, we evaluated by means of a low-compliance manometric system the effect of a new anticholinergic compound, cimetropium bromide (10 mg intravenously), on oesophageal variables of eight patients with nutcracker oesophagus, in a single-blind study. Eight age-matched healthy volunteers served as controls. In both patients and controls, cimetropium bromide significantly decreased lower oesophageal sphincter pressure and the distal and proximal mean contraction amplitude of the oesophageal body. Apart from an increase in pulse rate, no noteworthy side effects were observed. It is concluded that cimetropium bromide may be an effective therapeutic option in patients with nutcracker oesophagus.