Development of orally active oxytocin antagonists: studies on 1-(1-[4-[1-(2-methyl-1-oxidopyridin-3-ylmethyl)piperidin-4-yloxy]-2- methoxybenzoyl]piperidin-4-yl)-1,4-dihydrobenz[d][1,3]oxazin-2-one (L-372,662) and related pyridines

The previously reported oxytocin antagonist L-371,257 (2) has been modified at its acetylpiperidine terminus to incorporate various pyridine N-oxide groups. This modification has led to the identification of compounds with improved pharmacokinetics and excellent oral bioavailability. The pyridine N-oxide series is exemplified by L-372,662 (30), which possessed good potency in vitro (Ki = 4.1 nM, cloned human oxytocin receptor) and in vivo (intravenous AD50 = 0.71 mg/kg in the rat), excellent oral bioavailability (90% in the rat, 96% in the dog), good aqueous solubility (>8.5 mg/mL at pH 5.2) which should facilitate formulation for iv administration, and excellent selectivity against the human arginine vasopressin receptors. Incorporation of a 5-fluoro substituent on the central benzoyl ring of this class of oxytocin antagonists enhanced in vitro and in vivo potency but was detrimental to the pharmacokinetic profiles of these compounds. Although lipophilic substitution around the pyridine ring of compound 30 gave higher affinity in vitro, such substituents were a metabolic liability and caused shortfalls in vivo. Two approaches to prevent this metabolism, addition of a cyclic constraint and incorporation of trifluoromethyl groups, were examined. The former approach was ineffective because of metabolic hydroxylation on the constrained ring system, whereas the latter showed improvement in plasma pharmacokinetics in some cases.     

Effects of nitric oxide on neuroendocrine function and behavior

Nitric oxide (NO) is an unusual chemical messenger. NO mediates blood vessel relaxation when produced by endothelial cells. When produced by macrophages, NO contributes to the cytotoxic function of these immune cells. NO also functions as a neurotransmitter and neuromodulator in the central and peripheral nervous systems. The effects on blood vessel tone and neuronal function form the basis for an important role of NO on neuroendocrine function and behavior. NO mediates hypothalamic portal blood flow and, thus, affects oxytocin and vasopression secretion; furthermore, NO mediates neuroendocrine function in the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axes. NO influences several motivated behaviors including sexual, aggressive, and ingestive behaviors. Learning and memory are also influenced by NO. Taken together, NO is emerging as an important chemical mediator of neuroendocrine function and behavior.     

Structure and practice of institutional review boards in the United States

OBJECTIVE: The institutional review board (IRB) is a critical element in the protection of patients' and subjects' rights with regard to their participation in research protocols. The purpose of this study was to describe the structure and current practices of IRBs in the United States. METHODS: A self-administered questionnaire was mailed to the IRB chair of each U.S. hospital with a capacity of at least 400 beds (n = 907). The survey contained 21 questions outlining committee size and structure, review of research proposals, and policies concerning scientific misconduct. Chairs also were asked what advice they would offer a young investigator preparing a proposal for submission. RESULTS: A total of 488 surveys (54%) were returned; 447 of the responding institutions had an IRB committee. Committees had an average of 14 members, representing 27 medical specialties. Orthopedics had the least IRB representation (10% of committees), followed by emergency medicine (12%) and ophthalmology (15%). The majority of research proposals go through 5 specific steps once submitted for review. Common reasons for proposal rejection were improperly designed consent form (54%), poor study design (44%), unacceptable risk to subjects (34%), ethical or legal reasons (24%), and scientific merit (14%). When a research proposal is rejected, 86% of the responding IRBs assist the investigator in making appropriate revisions. Although a number of IRBs (17%) have dealt with scientific misconduct allegations, only 58% have a written policy regarding research integrity. CONCLUSION: Despite variations in committee structure and representation, IRBs have similar procedures for governing research. Investigators should be familiar with these procedures and are encouraged to discuss their proposal with an IRB representative prior to formal review.     

Matrilineal inheritance of complex I dysfunction in a multigenerational Parkinson's disease family

Recent data suggesting complex I dysfunction in Parkinson's disease (PD) arises from mitochondrial DNA (mtDNA) mutation does not conclusively answer whether the responsible genetic lesion is inherited (primary) or somatic (secondary). To address this question, we identified a family in which multiple members over three generations are affected with PD through exclusively maternal lines. Cytoplasmic hybrids (cybrids) were created for 15 family members over two generations by transferring each individual's mtDNA to mtDNA-depleted human neuroblastoma cells. Eight of the 15 cybrid lines contained mtDNA obtained from maternally descended family members and seven contained mtDNA from paternally descended family members. After 6 weeks of culture, cybrid cell lines were assayed for complex I activity and oxidative stress, and mitochondrial morphology was analyzed by electron microscopy. Compared with the cybrid lines containing mtDNA from paternal descendants, cybrid lines containing mtDNA from maternal descendants had lower complex I activity, increased reactive oxygen species production, increased radical scavenging enzyme activities, and more abnormal mitochondrial morphologic features. These findings were present in cybrid lines containing mtDNA from maternal descendants with PD as well as in currently asymptomatic young maternal descendants, and support a precedent for inherited mtDNA mutation in some persons with PD.     

Preovulatory overripeness of the oocyte as a cause of ovarian dysfunction in the human female

A variety of gynaecological phenomena such as menstrual disorders, infertility and premature menopause are associated with ovarian dysfunction. In this paper, a factor is considered that may play a role in the aetiology of ovarian dysfunction. Animal research has shown that preovulatory overripeness of the oocyte may cause various developmental and chromosomal anomalies. Among the developmental anomalies observed in amphibia and fish are a number of gonadal aberrations, often occurring in otherwise normal specimens. This may be the consequence of a degeneration of the 'germinal cytoplasm', cytoplasmic structures located in the vegetative pole region of the oocyte, destined to become part of future primordial germ cells. Indirect evidence suggests that preovulatory overripeness of the oocyte also plays a significant role in human reproductive failure. An increased risk of preovulatory overripeness is expected during periods of endocrine irregularities, such as the first postmenarcheal years, the last premenopausal years, the first months after a pregnancy and, possibly, during certain seasons. If the overripeness-induced gonadal maldevelopment observed in animals also occurs in humans, this may explain variations in reproductive function according to month of birth, as observed in women. It is hypothesized that females conceived during periods of maternal endocrine irregularities face an increased risk of ovarian dysfunction through overripeness-induced gonadal maldevelopment.     

Carnosine modulates zinc and copper effects on amino acid receptors and synaptic transmission

Carnosine is a dipeptide which is highly concentrated in mammalian olfactory sensory neurons along with zinc and/or copper, and glutamate. Although carnosine has been proposed as a neurotransmitter or neuromodulator, no specific function for carnosine has been identified. We used whole-cell current- and voltage-clamp recording to examine the direct effects and neuromodulatory actions of carnosine on rat olfactory bulb neurons in primary culture. Carnosine did not evoke a membrane current or affect currents evoked by glutamate, GABA or glycine. Copper and zinc inhibited NMDA and GABA receptor-mediated currents and inhibited synaptic transmission. Carnosine prevented the actions of copper and reduced the effects of zinc. These results suggest that carnosine may indirectly influence neuronal excitability by modulating the effects of zinc and copper.     

Conclusive evidence for distinct transporters for 5-hydroxytryptamine and noradrenaline in pulmonary endothelial cells of the rat

The aims of this study were to obtain conclusive evidence about the roles of a 5-hydroxytryptamine [5-HT] transporter and uptake1 in the dissipation of 5-HT in the lungs of the rat and to compare the properties of the 5-HT transporter in rat lungs with that in other tissues, including brain and platelets. In the first part of the study, the IC50 values of a range of selective inhibitors and substrates of the 5-HT transporter or uptake1 were determined for inhibition of uptake of 5-HT or noradrenaline in intact perfused lungs of rats. Monoamine oxidase was inhibited and, in experiments with noradrenaline, catechol-O-methyltransferase was also inhibited. Initial rates of uptake of 5-HT or noradrenaline were measured in lungs perfused with 2 nmol/l 3H-5-HT or 3H-noradrenaline for 2 min, in the absence or presence of at least three concentrations of paroxetine, citalopram, fluoxetine, 7-methyltryptamine, tryptamine, nisoxetine, imipramine, 5-HT, desipramine, (+)-oxaprotiline, cocaine or tyramine. The results showed that pharmacologically distinct transporters are involved in the uptake of 5-HT and noradrenaline in rat lungs, since there was no significant correlation between the IC50 values for inhibition of 5-HT and noradrenaline uptake in the lungs. However, there were significant correlations between the IC50 values for (a) inhibition of 5-HT uptake in rat lungs and of uptake by the 5-HT transporter in rat brain and (b) inhibition of noradrenaline uptake in rat lungs and of uptake1 in rat phaeochromocytoma PC-12 cells. The results support the conclusion that 5-HT uptake in rat lungs occurs, at least predominantly, by a 5-HT transporter which is very similar to or the same as that in other tissues, such as the brain, and provide further evidence for transport of noradrenaline by uptake1. Further experiments were carried out to determine whether there is any transport of 5-HT by uptake1 or of noradrenaline by the 5-HT transporter in rat lungs. Lungs were perfused with 2 nmol/l 3H-5-HT or 3H-noradrenaline for 2 min in the absence or presence of 1 mumol/l citalopram, desipramine, or citalopram and desipramine. The results showed that there was no evidence of any transport of 5-HT in the lungs by uptake1 or of noradrenaline by the 5-HT transporter, in that desipramine had no effect on 5-HT uptake (in the absence or presence of citalopram) and citalopram had no effect on noradrenaline uptake (in the absence or presence of desipramine). The final series of experiments was carried out to determine whether, at high concentrations of the amine, there is any interaction of 5-HT with uptake1 or of noradrenaline with the 5-HT transporter. Noradrenaline, at a concentration of 10 mumol/l, did not affect 5-HT uptake in lungs perfused with 2 nmol/l 3H-5-HT for 2 min (uptake1 inhibited), but 50 mumol/l 5-HT inhibited noradrenaline uptake by 56% in lungs perfused with 2 nmol/l 3H-noradrenaline for 2 min (5-HT transporter inhibited). These and the above results show that the 5-HT transporter appears to be exclusively responsible for 5-HT uptake in rat lungs, despite the possible interaction of 5-HT at high concentrations with the uptake1 transporter in the cells. On the other hand, noradrenaline is transported exclusively by uptake1 in the lungs, and there is no evidence that it interacts with the 5-HT transporter, even at high concentrations.     

Insulin-like growth factor-binding protein (IGFBP)-3 and IGFBP-5 share a common nuclear transport pathway in T47D human breast carcinoma cells

Insulin-like growth factor-binding proteins (IGFBPs) play an integral role in modifying insulin-like growth factor actions in a wide variety of cell types. Recent evidence suggests that IGFBP-3 and IGFBP-5 also have effects on cell growth that are insulin-like growth factor-independent. In investigating possible mechanisms for this effect, the intracellular trafficking of IGFBP-3 and IGFBP-5, both of which contain sequences with the potential for nuclear localization, was studied in T47D cells. Nuclear uptake of fluorescently labeled IGFBP-3 and IGFBP-5 was observed in a proportion of T47D cells that appeared to be rapidly dividing. IGFBP-1 and IGFBP-2, which do not possess the putative domain for nuclear translocation, were not transported to the nuclei of T47D cells. When T47D cells were preincubated with excess unlabeled IGFBP-3, nuclear localization of labeled IGFBP-3 or IGFBP-5 was not detected, indicating that their nuclear translocation involves a common pathway. Inhibition of receptor-mediated endocytosis did not affect nuclear uptake of IGFBP-3, suggesting that it uses an alternative non-classical import pathway for transport across the plasma membrane. In addition, a variant form of IGFBP-3 with a mutation in the putative nuclear localization sequence was unable to translocate to the nuclei of T47D cells, suggesting that nuclear translocation of IGFBP-3 was dependent on these carboxyl-terminal basic residues.