Investigation of Janus Kinase (JAK) Inhibitors for Lung Delivery and the Importance of Aldehyde Oxidase Metabolism

The Janus family of tyrosine kinases (JAK1, JAK2, JAK3, and TYK2) play an essential role in the receptor signaling of cytokines that have been implicated in the pathogenesis of severe asthma, and there is emerging interest in the development of small-molecule-inhaled JAK inhibitors as treatments. Here, we describe the optimization of a quinazoline series of JAK inhibitors and the results of mouse lung pharmacokinetic (PK) studies where only low concentrations of parent compound were observed. Subsequent investigations revealed that the low exposure was due to metabolism by aldehyde oxidase (AO), so we sought to identify quinazolines that were not metabolized by AO. We found that specific substituents at the quinazoline 2-position prevented AO metabolism and this was rationalized through computational docking studies in the AO binding site, but they compromised kinome selectivity. Results presented here highlight that AO metabolism is a potential issue in the lung.

Targeting the Regulatory Site of ER Aminopeptidase 1 Leads to the Discovery of a Natural Product Modulator of Antigen Presentation

ER aminopeptidase 1 (ERAP1) is an intracellular enzyme that generates antigenic peptides and is an emerging target for cancer immunotherapy and the control of autoimmunity. ERAP1 inhibitors described previously target the active site and are limited in selectivity, minimizing their clinical potential. To address this, we targeted the regulatory site of ERAP1 using a high-throughput screen and discovered a small molecule hit that is highly selective for ERAP1. (4aR,5S,6R,8S,8aR)-5-(2-(Furan-3-yl)ethyl)-8-hydroxy-5,6,8a-trimethyl-3,4,4a,5,6,7,8,8a-octahydronaphthalene-1-carboxylic acid is a natural product found in Dodonaea viscosa that constitutes a submicromolar, highly selective, and cell-active modulator of ERAP1. Although the compound activates hydrolysis of small model substrates, it is a competitive inhibitor for physiologically relevant longer peptides. Crystallographic analysis confirmed that the compound targets the regulatory site of the enzyme that normally binds the C-terminus of the peptide substrate. Our findings constitute a novel starting point for the development of selective ERAP1 modulators that have potential for further clinical development.

High-Resolution Crystal Structure of Endoplasmic Reticulum Aminopeptidase 1 with Bound Phosphinic Transition-State Analogue Inhibitor

Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an intracellular enzyme that helps generate peptides presented by Major Histocompatibility Complex Class I (MHC class I) molecules and is an emerging target for immunotherapy applications. Despite almost two decades of research on ERAP1, lack of high-resolution crystal structures has hampered drug-development efforts. By optimizing the protein construct, we obtained a high-resolution (1.60 Å) crystal structure of the closed-conformation of ERAP1 with a potent phosphinic pseudopeptide inhibitor bound in its active site. The structure provides key insight on the mechanism of inhibition as well as selectivity toward homologous enzymes and allows detailed mapping of the internal cavity of the enzyme that accommodates peptide-substrates. Bis-tris propane and malic acid molecules, found bound in pockets in the internal cavity, reveal potential druggable secondary binding sites. The ability to obtain high-resolution crystal structures of ERAP1 removes a major bottleneck in the development of compounds that regulate its activity and will greatly accelerate drug-discovery efforts.

Discovery of potent and selective Spleen Tyrosine Kinase inhibitors for the topical treatment of inflammatory skin disease

The discovery and lead optimisation of a novel series of SYK inhibitors is described. These were optimised for SYK potency and selectivity against Aurora B. Compounds were profiled in a human skin penetration study to identify a suitable candidate molecule for pre-clinical development. Compound 44 (GSK2646264) was selected for progression and is currently in Phase I clinical trials.

Identification of KasA as the cellular target of an anti-tubercular scaffold

Phenotypic screens for bactericidal compounds are starting to yield promising hits against tuberculosis. In this regard, whole-genome sequencing of spontaneous resistant mutants generated against an indazole sulfonamide (GSK3011724A) identifies several specific single-nucleotide polymorphisms in the essential Mycobacterium tuberculosis β-ketoacyl synthase (kas) A gene. Here, this genomic-based target assignment is confirmed by biochemical assays, chemical proteomics and structural resolution of a KasA-GSK3011724A complex by X-ray crystallography. Finally, M. tuberculosis GSK3011724A-resistant mutants increase the in vitro minimum inhibitory concentration and the in vivo 99% effective dose in mice, establishing in vitro and in vivo target engagement. Surprisingly, the lack of target engagement of the related β-ketoacyl synthases (FabH and KasB) suggests a different mode of inhibition when compared with other Kas inhibitors of fatty acid biosynthesis in bacteria. These results clearly identify KasA as the biological target of GSK3011724A and validate this enzyme for further drug discovery efforts against tuberculosis.

Screens for bactericidal compounds have resulted in promising anti-tubercular hits. Here, the authors analyse in detail the target of an indazole sulfonamide (GSK3011724A), and find that it has a different mode of inhibition compared to other Kas inhibitors of fatty acid biosynthesis in bacteria.

New direct inhibitors of InhA with antimycobacterial activity based on a tetrahydropyran scaffold

Tetrahydropyran derivative 1 was discovered in a high-throughput screening campaign to find new inhibitors of mycobacterial InhA. Following initial in-vitro profiling, a structure-activity relationship study was initiated and a focused library of analogs was synthesized and evaluated. This yielded compound 42 with improved antimycobacterial activity and low cytotoxicity. Additionally, the crystal structure of InhA in complex with inhibitor 1 was resolved, to reveal the binding mode and provide hints for further optimization.

Novel Interaction Mechanism of a Domain Antibody-based Inhibitor of Human Vascular Endothelial Growth Factor with Greater Potency than Ranibizumab and Bevacizumab and Improved Capacity over Aflibercept

A potent VEGF inhibitor with novel antibody architecture and antigen binding mode has been developed. The molecule, hereafter referred to as VEGF dual dAb (domain antibody), was evaluated in vitro for binding to VEGF and for potency in VEGF-driven models and compared with other anti-VEGF biologics that have been used in ocular anti-angiogenic therapeutic regimes. VEGF dual dAb is more potent than bevacizumab and ranibizumab for VEGF binding, inhibition of VEGF receptor binding assays (RBAs), and VEGF-driven in vitro models of angiogenesis and displays comparable inhibition to aflibercept (Eylea). VEGF dual dAb is dimeric, and each monomer contains two distinct anti-VEGF domain antibodies attached via linkers to a human IgG1 Fc domain. Mechanistically, the enhanced in vitro potency of VEGF dual dAb, in comparison to other anti-VEGF biologics, can be explained by increased binding stoichiometry. A consistent model of the target engagement has been built based on the x-ray complexes of each of the two isolated domain antibodies with the VEGF antigen.

Encoded library technology as a source of hits for the discovery and lead optimization of a potent and selective class of bactericidal direct inhibitors of Mycobacterium tuberculosis InhA

Tuberculosis (TB) is one of the world's oldest and deadliest diseases, killing a person every 20 s. InhA, the enoyl-ACP reductase from Mycobacterium tuberculosis, is the target of the frontline antitubercular drug isoniazid (INH). Compounds that directly target InhA and do not require activation by mycobacterial catalase peroxidase KatG are promising candidates for treating infections caused by INH resistant strains. The application of the encoded library technology (ELT) to the discovery of direct InhA inhibitors yielded compound 7 endowed with good enzymatic potency but with low antitubercular potency. This work reports the hit identification, the selected strategy for potency optimization, the structure-activity relationships of a hundred analogues synthesized, and the results of the in vivo efficacy studies performed with the lead compound 65.

Discovery of GSK143, a highly potent, selective and orally efficacious spleen tyrosine kinase inhibitor

The lead optimisation of the diaminopyrimidine carboxamide series of spleen tyrosine kinase inhibitors is described. The medicinal chemistry strategy was focused on optimising the human whole blood activity whilst achieving a sufficient margin over liability kinases and hERG activity. GSK143 is a potent and highly selective SYK inhibitor showing good efficacy in the rat Arthus model.

Pyrazolopyridines as potent PDE4B inhibitors: 5-heterocycle SAR

Following the discovery of 4-(substituted amino)-1-alkyl-pyrazolo[3,4-b]pyridine-5-carboxamides as potent and selective phosphodiesterase 4B inhibitors, [Hamblin, J. N.; Angell, T.; Ballentine, S., et al. Bioorg. Med. Chem. Lett.2008, 18, 4237] the SAR of the 5-position was investigated further. A range of substituted heterocycles showed good potencies against PDE4. Optimisation using X-ray crystallography and computational modelling led to the discovery of 16, with sub-nM inhibition of LPS-induced TNF-α production from isolated human peripheral blood mononuclear cells.

Identification of PDE4B Over 4D subtype-selective inhibitors revealing an unprecedented binding mode

A PDE4B over 4D-selective inhibitor programme was initiated to capitalise on the recently discovered predominance of the PDE4B subtype in inflammatory cell regulation. The SAR of a tetrahydrobenzothiophene (THBT) series did not agree with either of two proposed docking modes in the 4B binding site. A subsequent X-ray co-crystal structure determination revealed that the THBT ligand displaces the Gln-443 residue, invariably ligand-anchoring in previous PDE4 co-crystal structures, and even shifts helix-15 by 1-2A. For the first time, several residues of the C-terminus previously proposed to be involved in subtype selectivity are resolved and three of them extend into the ligand binding site potentially allowing for selective drug design.

N-(3-Cyano-4,5,6,7-tetrahydro-1-benzothien-2-yl)amides as potent, selective, inhibitors of JNK2 and JNK3

The identification and exploration of a novel, potent and selective series of N-(3-cyano-4,5,6,7-tetrahydro-1-benzothien-2-yl)amide inhibitors of JNK2 and JNK3 kinases is described. Compounds 5a and 11a were identified as potent inhibitors of JNK3 (pIC50 6.7 and 6.6, respectively), with essentially equal potency against JNK2 (pIC50 6.5). Selectivity within the mitogen-activated protein kinase (MAPK) family, against JNK1, p38alpha and ERK2, was observed for the series. X-ray crystallography of 5e and 8a in JNK3 revealed a unique binding mode, with the 3-cyano substituent forming an H-bond acceptor interaction with the hinge region of the ATP-binding site.

Nano-carriers for DNA delivery to the lung based upon a TAT-derived peptide covalently coupled to PEG-PEI

Gene therapy aimed at the respiratory epithelium holds therapeutic potential for diseases such as cystic fibrosis and lung cancer. Polyethylenimine (PEI) has been utilized for gene delivery to the airways. In this study, we describe a new modification of PEI, in which an oligopeptide related to the protein transduction domain of HIV-1 TAT was covalently coupled to 25 kDa PEI (PEI) through a heterobifunctional polyethylenglycol (PEG) spacer resulting in a TAT-PEG-PEI conjugate. Improved DNA reporter gene complexation and protection was observed for small (approximately 90 nm) polyplexes as well as significantly improved stability against polyanions, Alveofact, bronchial alveolar lining fluid and DNase. To determine polyplex toxicity in vitro, MTT assays were performed and, for in vivo testing, the mice bronchial alveolar lavage was investigated for total cell counts, quantity of neutrophils, total protein and TNF-alpha concentration. All parameters suggest significantly lower toxicity for TAT-PEG-PEI. Transfection efficiencies of both PEI and TAT-PEG-PEI polyplexes with DNA were studied under in vitro conditions (A549) and in mice after intratracheal instillation. While luciferase expression in A549 cells was much lower for TAT-PEG-PEI (0.2 ng/mg protein) than for PEI (2 ng/mg), significantly higher transfection efficiencies for TAT-PEG-PEI were detected in mice. Reporter gene expression was distributed through bronchial and alveolar tissue. Thus, TAT-PEG-PEI represents a new approach to non-viral gene carriers for lung therapy, comprising protection for plasmid DNA, low toxicity and significantly enhanced transfection efficiency under in vivo conditions.

The mechanism of iron uptake by transferrins: the structure of an 18 kDa NII-domain fragment from duck ovotransferrin at 2.3 A resolution

The molecular structure of an iron-containing 18 kDa fragment of duck ovotransferrin, obtained by proteolysis of the intact protein, has been elucidated by protein crystallographic techniques at 2.3 A resolution. This structure supports a mechanism of iron uptake in the intact protein whereby the binding of the synergistic (bi)carbonate anion is followed by binding of the metal with the lobe in the open configuration. These stages are then followed by domain closure in which the aspartic acid residue plays a further key role, by forming an interdomain hydrogen-bond interaction in addition to serving as a ligand to the iron. This essential dual role is highlighted by model building studies on the C-terminal lobe of a known human variant. In this variant a mutation of a glycine by an arginine residue enables the aspartic acid to form an ion pair and reduce its effectiveness for both metal binding and domain closure. The X-ray structure of the 18 kDa fragment strongly suggests that the histidine residue present at the iron binding site of the intact protein and arising from the second interdomain connecting strand has been removed during the preparative proteolysis.

Unusual craniocerebral injury caused by a pneumatic nail gun

A man was found unconscious near a ladder in a house. After resuscitation he was brought to a hospital and X-rays of the skull showed that two 12-cm long nails had completely penetrated the cranial cavity. The nails were operatively removed and after treatment for 5 weeks, the patient was transferred to a rehabilitation centre with a decreasing hemiparesis on the left side and general deterioration and then, after an attempted suicide to a psychiatric hospital. The perforating cranio-cerebral injury from a pneumatic nail gun known to reach only low muzzle velocities is a very unusual finding.

The mechanism of iron uptake by transferrins: the X-ray structures of the 18 kDa NII domain fragment of duck ovotransferrin and its nitrilotriacetate complex

In a previous paper [Lindley et al. (1993), Acta Cryst. D49, 292-304], the X-ray structure analysis of the 18 kDa fragment of duck ovotransferrin, corresponding to the NII domain of the intact protein, was reported at a resolution of 2.3 A. In this structure, the Fe(III) cation binds to two tyrosine residues and the synergistic carbonate anion in an identical manner to that found in the intact protein. However, the aspartate and histidine residues, normally involved in iron binding in transferrins, are absent in the fragment and it was not possible to unequivocally define what had replaced them. The electron density was tentatively assigned to be a mixture of peptides, presumably resulting from the proteolytic preparation of the fragment, binding to the iron through their amino and carboxylate termini. A more recent X-ray analysis of the fragment, from a different preparation, has resulted in a structure at 1.95 A, in which glycine appears to be the predominant residue bound to the cation. In an alternative attempt to clarify the binding of iron to the 18 kDa fragment, the metal was removed by dialysis and replaced in the form of ferric nitrilotriacetate. Crystallization of this complex has resulted in an X-ray structure at 1.90 A in which the Fe(III) is bound to the synergistic carbonate anion and only one tyrosine residue in a manner almost identical to the intact protein. The carboxylate groups and the tertiary amino group of the nitrilotriacetate occupy the remaining coordination sites. The second tyrosine residue, Tyr95, is not bound directly to the iron. The implication of these structures with respect to the mechanism of iron binding by the transferrins is addressed.

The crystal and molecular structures of diferric porcine and rabbit serum transferrins at resolutions of 2.15 and 2.60 A, respectively

The serum transferrins are monomeric proteins with a molecular mass of around 80 kDa and are responsible for the transport of iron in vertebrates. The three-dimensional structures of diferric porcine and rabbit serum transferrin have been refined against X-ray diffraction data extending to 2.15 and 2.60 A, respectively. Data for both proteins were collected using synchrotron radiation at temperatures of 277 K. The porcine protein crystallizes in the space group C2, with unit-cell parameters a = 223.8, b = 44.9, c = 78.9 A, beta = 105.4 degrees with one molecule in the asymmetric unit. The structure was solved by molecular-replacement methods using rabbit serum transferrin as the search model. The structure was refined using REFMAC, with a final residual of 13.8% (R(free) = 18.2% for a 5% data sample) for all data to 2.15 A. The final model comprises 5254 protein atoms, two Fe(3+) cations and two CO(3)(2-) anions, one N-acetyl glucosamine moiety and 494 water molecules. The rabbit protein crystallizes in space group P4(3)2(1)2, with unit-cell parameters a = 127.2, c = 144.9 A and one molecule per asymmetric unit. The structure was solved using the method of multiple isomorphous replacement and refined using REFMAC to give a final residual of 18.6% (R(free) = 22.2% for a 5% data sample) for all data to 2.60 A. The final model comprises 5216 protein atoms, two Fe(3+) cations and two CO(3)(2-) anions, a Cl(-) anion and 206 solvent molecules; there is no clear indication of the carbohydrate moiety attached to Asn490 (rabbit serum numbering). Both molecules adopt a bilobal structure typical for members of the transferrin family. Each of the structurally homologous lobes contains two dissimilar domains with a single iron-binding site buried within the interdomain cleft. The porcine serum protein lacks an interdomain disulfide bridge close to the connecting peptide between the lobes, but this seems to have little effect on the overall orientation of the lobes. The N-lobes of both proteins possess lysine residues, one from each of the two domains, that lie in close proximity to one another to form the so-called dilysine trigger. The more acid-labile release of iron from serum transferrins than from lactoferrins is discussed.

Vasoactive treatment for hearing preservation in acoustic neuroma surgery

OBJECT

Delayed hearing loss following surgery for acoustic neuroma indicates anatomical and functional preservation of the cochlear nerve and implies that a pathophysiological mechanism is initiated during surgery and continues thereafter. Intraoperative brainstem auditory evoked potentials (BAEPs) typically demonstrate gradual reversible loss of components in these patients.

METHODS

Based on this BAEP pattern, a consecutive series of 41 patients with unilateral acoustic neuromas was recruited into a prospective randomized study to investigate hearing outcomes following the natural postoperative course and recuperation after vasoactive medication. Both groups were comparable in patient age, tumor size, and preoperative hearing level. Twenty patients did not receive postoperative medical treatment. In 70% of these patients anacusis was documented and in 30% hearing was preserved. Twenty-one patients were treated with hydroxyethyl starch and nimodipine for an average of 9 days. In 66.6% of these patients hearing was preserved and in 33.3% anacusis occurred.

CONCLUSIONS

These results are statistically significant (p < 0.05, chi2 = 5.51) and provide evidence that these surgically treated patients suffer from a disturbed microcirculation that causes delayed hearing loss following removal of acoustic neuromas.

Generalizability and clinical utility of a practice-based infant pain assessment instrument

The purpose of this study was to determine the clinical usefulness and generalizability of an infant pain assessment instrument. Earlier work showed that this instrument--an algorithm derived from a model of infant pain assessment-possessed excellent content validity, criterion-like validity, and 3-month stability (test-retest reliability). In this study, generalizability was determined by comparing the percentage agreement between inexperienced pediatric nurses and one author, both using the tool to assess pain of infants in various clinical settings, and by comparing the percentage agreement between one author who used the tool to assess pain and the infant's pediatric nurse caretaker who used his or her clinical expertise, not the tool, to assess pain across various clinical settings. The results show excellent generalizability.

Clinical and neurophysiological observations after superior petrosal vein obstruction during surgery of the cerebellopontine angle: case report

IMPORTANCE

Preservation of venous drainage during surgery of the cerebellopontine angle has received little attention.

CLINICAL PRESENTATION

We describe changes in brainstem auditory evoked potentials after temporary obstruction of the superior petrosal vein during surgical resection of a small meningioma at the petrous apex via a standard suboccipital-lateral approach. Temporary clipping of the petrosal vein resulted in deterioration of the brainstem auditory evoked potentials. The tumor was removed with preservation of the superior petrosal vein.

CONCLUSION

A transient postoperative cochlear nerve deficit emphasizes the importance of venous drainage and its preservation during surgery for small lesions of the cerebellopontine angle that do not distort normal anatomic structures.

The impact of two transfer techniques used during skin-to-skin care on the physiologic and behavioral responses of preterm infants

BACKGROUND

Conservation of energy assumes an important role in the care of infants requiring assisted ventilation, yet little research has been conducted on this group of infants in terms of thermoregulation, oxygenation, heart rate, or sleep states during skin-to-skin care.

OBJECTIVES

To compare the impact of two different transfer techniques used in skin-to-skin care (nurse transfer and parent transfer) on physiologic stability and other descriptive measures of physiologic stability related to energy conservation in ventilated preterm infants during and after skin-to-skin care.

METHOD

Fifteen ventilated preterm infants weighing a mean of 1,094 g were randomly assigned to receive either parent or nurse-to-parent transfer on the first of 2 consecutive days and the alternate method the following day. Temperature was taken before and after skin-to-skin care. Oxygen saturation and heart rate were recorded minute by minute, and the Assessment of Behavioral Systems Observation (ABSO) scale scores was used to measure physiologic organization, motor organization, self-regulation, and need for caregiver facilitation during transfer to and from the parent and during pre, post, and skin-to-skin periods.

RESULTS

Temperature remained stable. Oxygen saturation decreased and heart rate increased when the infant was transferred to and from the parent, but returned to baseline levels during and after skin-to-skin care regardless of the transfer method. Infants showed more physiologic and motor disorganization, less self-regulation, and more need for caregiver facilitation during transfers to and from the parent than during the pre, post, and skin-to-skin care periods.

CONCLUSIONS

Both transfer methods resulted in physiologic disorganization. However, during and after skin-to-skin care, infants exhibited no signs of energy depletion.

Validity and reliability of a practice-based infant pain assessment instrument

The purpose of this study was to determine the validity and reliability of an infantpain assessment instrument. This instrument is an algorithm derived from a model of infant pain assessment that emerged from interviews with pediatric nurses and includes methods for evaluating clinical data that suggest the Iikelihood of pain. Unlike other instruments, this instrument is not restricted to use in clinical situations where the likelihood of pain is evident. This instrument determines the three levels of pain that guide subsequent nursing interventions: no pain, mild pain (discomfort), and severe pain. Content validity was determined by obtaining and incorporating feedback from a focus group of practicing pediatric nurses on various developmental stages of the instrument. Criterion-like validity was excellent: Mean Pearson correlations between the pain ratings of 18 videotaped infants by 24 nursing students using the instrument with ratings performed by a panel of 5 expert nurses not using any instrument was 0.96. Test-retest reliability, as measured by Pearson correlations between pain ratings 3 months apart, was also excellent (r = 0.91).

X-ray crystal structure of human dopamine sulfotransferase, SULT1A3. Molecular modeling and quantitative structure-activity relationship analysis demonstrate a molecular basis for sulfotransferase substrate specificity

Humans are one of the few species that produce large amounts of catecholamine sulfates, and they have evolved a specific sulfotransferase, SULT1A3 (M-PST), to catalyze the formation of these conjugates. An orthologous protein has yet to be found in other species. To further our understanding of the molecular basis for the unique substrate selectivity of this enzyme, we have solved the crystal structure of human SULT1A3, complexed with 3'-phosphoadenosine 5'-phosphate (PAP), at 2.5 A resolution and carried out quantitative structure-activity relationship (QSAR) analysis with a series of phenols and catechols. SULT1A3 adopts a similar fold to mouse estrogen sulfotransferase, with a central five-stranded beta-sheet surrounded by alpha-helices. SULT1A3 is a dimer in solution but crystallized with a monomer in the asymmetric unit of the cell, although dimer interfaces were formed by interaction across crystallographic 2-fold axes. QSAR analysis revealed that the enzyme is highly selective for catechols, and catecholamines in particular, and that hydrogen bonding groups and lipophilicity (cLogD) strongly influenced K(m). We also investigated further the role of Glu(146) in SULT1A3 using site-directed mutagenesis and showed that it plays a key role not only in defining selectivity for dopamine but also in preventing many phenolic xenobiotics from binding to the enzyme.

The prognostic value of intraoperative BAEP patterns in acoustic neurinoma surgery

Based on a consecutive series of 70 hearing patients with unilateral acoustic neurinomas and intraoperative monitoring of brain-stem auditory evoked potentials (BAEP), 4 dynamic BAEP patterns could be characterized. These patterns correspond with early and late postoperative hearing outcome. All patients with stable wave V (pattern 1) showed definite hearing preservation, all patients with irreversible abrupt loss of BAEP (pattern 2) lost their hearing, despite early hearing preservation in two cases. All patients with irreversible progressive loss of either wave I or wave V (pattern 3) eventually suffered from definite postoperative hearing loss, despite early hearing preservation in two cases. Those cases with intraoperative reversible loss of BAEP (pattern 4) showed variable short and long term hearing outcome. In 34% hearing was preserved, 44% suffered from postoperative hearing loss, the remaining 22% showed postoperative hearing fluctuation, either as a delayed hearing loss or as reversible hearing loss. Postoperative hearing fluctuation indicates anatomical and functional preservation of the cochlear nerve during surgery and is suggestive of a pathophysiological mechanism initiated during the surgical procedure and continuing thereafter. Patients at risk for delayed hearing loss can be identified during surgery by a characteristic BAEP pattern and may benefit from vasoactive treatment.

The influence of background clinical data on infant pain assessments

The purpose of this study was to determine the importance of knowledge of clinical background data on nursing assessments of infant pain. In a quasi-experimental design, the infant pain assessments of two groups of pediatric nurses were compared. Both groups assessed the levels of pain of the same videotaped infants. One group also read clinical background data about each infant; the other group did not. The group who read clinical background data evidenced higher mean levels of assessed pain per videotaped infant than did the group who only viewed the videotapes. Findings underscore the importance of clinical data and clinical context in the process of assessing infant pain and the risk of underestimating pain when all factors are not considered.

Parents' perception of skin-to-skin care with their preterm infants requiring assisted ventilation

OBJECTIVE

To explore parents' perception of skin-to-skin care with their preterm infant who is on assisted ventilation, and to elucidate factors influencing the decision to continue or discontinue skin-to-skin care.

DESIGN

Naturalistic inquiry, using open-ended, transcribed and audiotaped face-to-face and telephone interviews.

SETTING

Tertiary neonatal care setting and homes of parents.

PARTICIPANTS

Eight mothers and one father who participated in skin-to-skin care.

INTERVENTIONS

Two 60-minute skin-to-skin care sessions.

RESULTS

Three themes emerged: (a) ambivalence of parents toward skin-to-skin care, including subthemes of yearning to hold the infant and apprehension to do so; (b) need of a supportive environment; and (c) special quality of the parent-infant interaction, including subthemes of intense connectedness and active parenting. Perceptions of apprehension, need for a supportive environment, and active parenting differed between parents who continued skin-to-skin care during their infants' hospitalization and parents who did not. Three of the four parents who discontinued skin-to-skin care in the hospital resumed when their infants were home.

CONCLUSIONS

Differences in narratives of parents highlighted the importance of individualizing the skin-to-skin experience to the needs of parent and infant. Parents who resumed skin-to-skin care at home valued the experience while their infant was hospitalized but needed intervention to alleviate their apprehension, enhance their feeling of autonomy, and modify the environment.

Testing a model of the nursing assessment of infant pain

The purpose of this study was to test whether elements of an infant pain assessment model interacted as postulated by the model. The elements are the infant's response to comfort measures and the principle of consolability. Four different scenarios for each of 16 videotaped infants were prepared. Each scenario represented one of four different combinations of likelihood of pain and consolability and consisted of a videotape plus written clinical information. Forty-eight volunteer pediatric nurses assessed infant pain of 16 scenarios, each depicting one of the 16 infants. Mean level of assessed pain was highest for the "high likelihood of pain and difficult to console" group, second highest for the "high likelihood of pain and easily consoled" group, third highest for the "low likelihood of pain and difficult to console" group and least for the "low likelihood of pain and easily consoled" group. Findings supported the infant pain assessment model.

Preservation of hearing in large acoustic neurinomas following removal via suboccipito-lateral approach

A consecutive series of 61 patients with pre-operative hearing underwent surgical removal of a large acoustic neurinoma via the lateral suboccipital approach between 1984 and 1996. Brain-stem auditory evoked potentials (BAEP) were present in all cases before surgery and all patients underwent intra-operative monitoring of BAEP. The average tumour size including the portion within the meatus acusticus internus was 30, 5 mm (range 20 mm-49 mm). Complete tumour removal was achieved in all but three cases. In 43.1% of patients with complete tumour removal hearing was preserved initially after surgery. Delayed postoperative hearing loss was observed in 11 patients and hearing recovery in 2 patients leading to 27.5% definite hearing preservation. Hearing preservation was achieved in 37% of cases with tumour size between 20 mm-29 mm and in 23.5% of case with tumour size larger than 30 mm. These results indicate that even in large neurinoms hearing preservation should be attempted in all patients with documented pre-operative hearing and BAEP.

The nature of ligand-induced conformational change in transferrin in solution. An investigation using X-ray scattering, XAFS and site-directed mutants

Ligand-induced conformational change in transferrins has been studied by site-directed mutagenesis of human serum half molecule (N-lobe), X-ray absorption fine structure (XAFS) spectroscopy and X-ray solution scattering. Use of recent advances in data analysis has been made for extracting model-independent molecular shapes from X-ray solution scattering data for the intact, the half molecule and its mutants. Clear evidence is provided that the transferrin molecule (intact as well as N-lobe), in its apo and holo forms, exists for the majority of the time in well-defined specific conformations representing the "fully opened" and "closed" states of the molecule, respectively. Evidence is also provided for the existence of an additional conformation, referred to here as the "intermediate" conformation for simplicity, which is trapped in the case of some of the mutants in the iron-bound form. We suggest that domain closure in the transferrin molecule is a two-step process, with the intermediate conformation representing the first stage of domain closure (approximately 20 degrees hinge-twist of domain II). Our data are not inconsistent with the ligand-free molecule sampling the closed states occasionally (< or = 10%) but are not in support of a continuous conformational search between the fully opened and closed states in the absence of iron.

Infant physiologic and behavioral organization during swaddled versus unswaddled weighing

OBJECTIVE

The objective of this study was to evaluate the use of blanket swaddling during weighing on the physiologic and behavioral responses of preterm infants.

STUDY DESIGN

A repeated-measures crossover design was used in a children's hospital intensive care nursery setting. Fourteen preterm infants with a mean gestational age of 32 weeks and mean weight of 1427 gm were weighed on two consecutive nights. A random start approach was used to determine initial order of swaddled or unswaddled weights. Effects of swaddled and unswaddled weighing were examined with use of the Assessment of Behavioral Systems Organization scales. Repeated-measures analysis of variance was used for analysis.

RESULTS

Contrasts done on significant treatment-period interactions indicated that when swaddled, infants showed less physiologic distress (p < 0.002), better motor organization (p < 0.001), and more effective self-regulatory ability (p < 0.037) than when unswaddled during weighing.

CONCLUSIONS

Swaddled weighing may decrease physiologic and behavioral distress in preterm infants.

Rab7: crystallization of intact and C-terminal truncated constructs complexed with GDP and GppNHp

The GTP/GDP conformational switch of members of the rab family of ras-related GTP-ases control specific intracellular vesicle transport pathways. We report the crystallization of the late-endosomal rab protein rab7, in both GTP and GDP conformations. X-ray data from crystals of rab7(1-207) GppNHp (i.e., intact rab7, without C-terminal bound lipid, complexed with a non-hydrolysable GTP analog), rab7(1-197)GppNHp and rab7(1-197)GDP were collected to 1.9A (0 degree C), 1.76A (100 degrees K) and 1.75A (100 degrees K) respectively. Rab7-GDP crystals diffract to at least 1.35A.

Rab7: NMR and kinetics analysis of intact and C-terminal truncated constructs

Rab proteins are a family of approximately 25kD ras-related GTPases which are associated with distinct intracellular membranes where they control vesicle traffic between intracellular compartments. The late-endosomal rab protein rab7(1-207), (lacking only the C-terminal lipids of the native molecule) and three C-terminal truncated constructs rab7(1-202), rab7(1-197) and rab7(1-182) were purified using an E. coli expression system. The C-terminal tail region of rab proteins is of special interest because it is thought to target rab proteins to particular intracellular membranes. A comparison of TOCSY-NMR spectra from intact rab7(1-207) and the tail-less construct rab7(1-182) suggested that much of the C-terminal tail is flexible in solution. The GTP hydrolysis, and GDP association and dissociation rates for all the truncated and intact constructs were similar, showing that the tail region of rab7(1-207) has little influence on the hydrolysis and exchange rates of the nucleotide.

Quick Fluorescence-EXAFS: an Improved Method for Collection of Conventional XAFS Data, an Improved Method for Collection of Conventional XAFS Data and for Studying Reaction Intermediates in Dilute Systems

The quick EXAFS (QuEXAFS) technique provides an alternative way of recording X-ray absorption fine-structure (XAFS) data where the scan time is reduced by moving the monochromator at a constant angular speed and recording the data ;on the fly'. Results are presented to show that the use of fluorescence detection with QuEXAFS is eminently suitable for studying reactions in dilute systems such as metalloproteins at a sub-minute time scale. In addition, we show that the fluorescence-QuEXAFS technique can reduce the overall time for normal data collection by some 50% compared with conventional step-by-step scanning EXAFS using the same optical system, thus reducing the total X-ray exposures of the samples. The use of X-rays for studying in situ redox reactions is demonstrated.

Characterization and structural analysis of a functional human serum transferrin variant and implications for receptor recognition

The nucleotide and amino acid substitutions leading to the only known functional variant of human serum transferrin have been characterized by sequencing of a peptide produced by cyanogen bromide digestion and genomic PCR coupled with cycle sequencing, respectively. There is an amino acid substitution at position 394 (Gly-->Arg) resulting from a mutational transition, G-->A, in the first nucleotide of the codon GGG. The Zn(2+)-, Al(3+)-, and Cu(2+)-binding properties of the variant, ascertained by UV difference spectra and, in the case of copper, protein fluorescence quenching, confirm that these metals binds to only one of the two sites. Solution X-ray scattering measurements indicate that the lobe (the C-lobe) containing the mutation remains "open" in the iron-bound state, and modeling studies suggest that this is a consequence of the formation of a salt bridge between Arg394 in the variant protein and Asp392, one of the iron-binding ligands in the C-lobe. This rationalizes for the first time the observed reduction in receptor affinity of the diferric variant protein for PHA-stimulated lymphocytes [Young, S.P., et al. (1984) Br. J. Haematol. 56, 581-587] and here repeated with K562 cells. These data lend support to the hypothesis that the closed conformation for both lobes contributes to receptor recognition.

X-ray scattering using synchrotron radiation shows nitrite reductase from Achromobacter xylosoxidans to be a trimer in solution

We demonstrate here the applicability of X-ray scattering for studying molecular conformation of multimeric proteins in solution by using synchrotron radiation to extend the range of data collection to include medium angles (ca. 3-4 degrees). We have been able to define the solution structure of the dissimilatory nitrite reductase of Achromobacter xylosoxidans (AxNiR), an enzyme for which there are conflicting reports as to the nature of its multimeric structure. Quantitative interpretation of the X-ray scattering profile, based on a modeling study using the high-resolution crystal structure data for the nitrite reductase from the related organism Achromobacter cycloclastes (AcNiR), provides a detailed model for the trimeric structure of AxNiR in solution. Sedimentation equilibrium centrifugation gave an M(r) of 103,000, consistent with such a trimeric structure.

Asp ligand provides the trigger for closure of transferrin molecules. Direct evidence from X-ray scattering studies of site-specific mutants of the N-terminal half-molecule of human transferrin

Recent X-ray crystallographic and solution X-ray scattering studies have shown that transferrins (serum transferrin, lactoferrin and ovotransferrin) undergo a major conformational change when iron is incorporated into the molecule. Apo-proteins show a structure with open interdomain clefts which close when iron is bound. The closed conformation has been suggested as an important step in the receptor recognition. Here, we report X-ray solution scattering experiments of the mutated N-terminal fragment of human serum transferrin with Asp63-->Ser (Cys). The data provide the first direct experimental evidence for the existence of a trigger mechanism for the closure of the interdomain cleft and that this trigger mechanism is disrupted by mutation of Asp63, the only ligand of iron from domain I.

Metal-induced conformational changes in transferrins

Recent studies on iron-loaded transferrins have revealed a conformational change upon binding iron due to a domain closure. It has been suggested that the domain closure may be the key for the receptor recognition of the metal loaded transferrin (Grossmann et al., 1992). Small angle X-ray scattering has been used to provide direct structural information on the conformational changes that may take place upon the binding and release of different metals to the transferrins in solution. The data show that In3+ and Cu2+ induce the same domain closure as Fe3+; Al3+ causes a conformational change of somewhat smaller magnitude while Hf4+ does not induce any conformational change. The results are discussed in terms of the molecular recognition of metal loaded transferrin by the receptor.

X-ray solution scattering reveals conformational changes upon iron uptake in lactoferrin, serum and ovo-transferrins

X-ray solution scattering has been used for studying the structural changes that take place upon uptake and release of iron from serum and chicken ovo-transferrin and human lactoferrin. In the case of chicken ovo-transferrin, data have been obtained for both the intact protein and the isolated N and C-lobes with and without iron. These studies reveal that both lobes undergo a change that is consistent with an opening of the inter-domain cleft when iron is removed from the protein. We suggest that the conformational change of the protein increases the specificity of receptor binding and that the closed configuration of the iron-loaded protein is one, or perhaps the, decisive step in the mechanism for receptor-mediated endocytosis.