An investigation into the structure and bioavailability of alpha-tocopherol dispersions in Gelucire 44/14

In this investigation we describe the preparation, physical characterisation and in vivo behaviour of solid dispersions of a liquid nutraceutical, alpha-tocopherol, in Gelucire 44/14 with a view to establishing whether dispersion in this matrix may provide a means of formulating a liquid drug in a solid dosage form while also improving the oral bioavailability. Using Vitamin E Preparation USP as the source of alpha-tocopherol, dispersions were prepared using a melt-fusion method with active loadings up to 50% (w/w) and characterised using differential scanning calorimetry and optical microscopy. Capsules containing 300 IU alpha-tocopherol were manufactured and the absorption profiles compared to a commercial soft gelatin capsule preparation in healthy human volunteers. Confocal laser scanning microscopy (CLSM) studies were performed in order to elucidate the mechanism by which drug release may be occurring. Differential scanning calorimetry studies indicated that the presence of the active had a negligible effect on the melting profile of the carrier, indicating limited miscibility between the two components, a conclusion supported by the microscopy studies. Similarly, the dispersions were shown to exhibit a glass transition corresponding to the incorporated drug, indicating molecular cooperativity and hence phase separation from the lipid base. Despite the phase separation, it was noted that capsules stored for 18 months under ambient conditions showed no evidence of leakage. Bioavailability studies in six healthy male volunteers indicated that the Gelucire 44/14 formulation showed an approximately two-fold increase in total alpha-tocopherol absorption compared to the commercial preparation. Confocal laser scanning microscopy studies indicated that, on contact with water, the dispersions formed two interfacial layers, from which the Gelucire 44/14 disperses in the liquid medium as small particles. Furthermore, evidence was obtained for the dispersed material becoming incorporated into the hydrated lipid. In conclusion, the dispersion of the liquid drug in Gelucire 44/14 appears to allow the dual advantages of the preparation of a solid formulation and improved bioavailability of this material.

Characterization of the role of the divalent metal ion-dependent transcriptional repressor MntR in the virulence of Staphylococcus aureus

DtxR-type metal ion-dependent repressors, present in many bacterial pathogens, may regulate expression of virulence genes such as that encoding diphtheria toxin. SirR, a DtxR homologue initially identified in Staphylococcus epidermidis, governs the expression of the adjacent sitABC operon encoding a putative metal ion ABC transporter system. We identified a sirR homologue, mntR, in Staphylococcus aureus and demonstrated by gel shift assay that the corynebacterial repressor DtxR binds to the S. aureus mntABC operator in the presence of Fe(2+) or Mn(2+). Since a mutant DtxR, DtxR(E175K), functions as an iron-independent hyperrepressor in certain settings, we constructed a heterodiploid S. aureus strain expressing dtxR(E175K) from the native mntR promoter. Transcription of the S. aureus mntABC operon was repressed in the presence of Fe(2+) or Mn(2+) in wild-type and heterodiploid S. aureus strains. Under metal ion-limiting conditions, mntABC transcription was reduced but not abolished in S. aureus isolates expressing dtxR(E175K) compared with an isogenic control, suggesting that DtxR(E175K) binds the S. aureus MntR box in vivo. Under all conditions tested, mntABC transcription in the dtxR(E175K)-expressing strain was reduced relative to the isogenic control, indicating that DtxR(E175K) function was constitutively active. In the mouse skin abscess model, dtxR(E175K)-expressing S. aureus recombinants showed significantly reduced CFU levels compared with the isogenic wild-type control. We conclude that the S. aureus MntR box is recognized by corynebacterial DtxR proteins and thus belongs to the DtxR family of metal-dependent operator sites. Moreover, constitutive repression by DtxR(E175K) reduces the virulence of S. aureus in the mouse skin abscess model.

Metal stoichiometry and functional studies of the diphtheria toxin repressor

Diphtheria toxin repressor (DtxR) is a transition metal ion-activated repressor in Corynebacterium diphtheriae. DtxR is an iron sensor; metal-bound DtxR represses transcription of genes downstream of the tox operator. Wild-type DtxR [DtxR(wt)] and several mutant forms were overexpressed and purified from Escherichia coli. DtxR was isolated without bound metal. Metal reconstitution gave a binding stoichiometry of 2 per monomer for DtxR(wt) and 1 per monomer for DtxR(H79A) and DtxR(M10A). DNA binding of DtxR(H79A) and DtxR(M10A) indicates that metal site 2 is essential for activity. Metal binding lowers the dimerization K(d) of DtxR from low micromolar to 33 nM. Gel electrophoretic mobility-shift assays show that Fe(2+) and not Fe(3+) activates DtxR for DNA binding. This finding suggests that gene regulation by DtxR may be sensitive not only to iron levels but also to redox state of the iron. Mutations in the tox operator sequence indicate that DtxR dimers binding to DNA may be highly cooperative.

The src homology 3-like domain of the diphtheria toxin repressor (DtxR) modulates repressor activation through interaction with the ancillary metal ion-binding site

The diphtheria toxin repressor (DtxR) is a transition metal ion-activated repressor that acts as a global regulatory element in the control of iron-sensitive genes in Corynebacterium diphtheriae. We recently described (L. Sun, J. C. vanderSpek, and J. R. Murphy, Proc. Natl. Acad. Sci. USA 95:14985-14990, 1998) the isolation and in vivo characterization of a hyperactive mutant of DtxR, DtxR(E175K), that appeared to be constitutively active. We demonstrate here that while DtxR(E175K) remains active in vivo in the presence of 300 micro M 2,2'dipyridyl, the purified repressor is, in fact, dependent upon low levels of transition metal ion to transit from the inactive apo form to the active metal ion-bound form of the repressor. Binding studies using 8-anilino-1-naphthalenesulfonic acid suggest that the E175K mutation stabilizes an intermediate of the molten-globule form of the repressor, increasing exposure of hydrophobic residues to solvent. We demonstrate that the hyperactive DtxR(E175K) phenotype is dependent upon an intact ancillary metal ion-binding site (site 1) of the repressor. These observations support the hypothesis that metal ion binding in the ancillary site facilitates the conversion of the inactive apo-repressor to its active, operator-binding conformation. Furthermore, these results support the hypothesis that the C-terminal src homology 3-like domain of DtxR plays an active role in the modulation of repressor activity.

The cytosolic entry of diphtheria toxin catalytic domain requires a host cell cytosolic translocation factor complex

In vitro delivery of the diphtheria toxin catalytic (C) domain from the lumen of purified early endosomes to the external milieu requires the addition of both ATP and a cytosolic translocation factor (CTF) complex. Using the translocation of C-domain ADP-ribosyltransferase activity across the endosomal membrane as an assay, the CTF complex activity was 650-800-fold purified from human T cell and yeast extracts, respectively. The chaperonin heat shock protein (Hsp) 90 and thioredoxin reductase were identified by mass spectrometry sequencing in CTF complexes purified from both human T cell and yeast. Further analysis of the role played by these two proteins with specific inhibitors, both in the in vitro translocation assay and in intact cell toxicity assays, has demonstrated their essential role in the productive delivery of the C-domain from the lumen of early endosomes to the external milieu. These results confirm and extend earlier observations of diphtheria toxin C-domain unfolding and refolding that must occur before and after vesicle membrane translocation. In addition, results presented here demonstrate that thioredoxin reductase activity plays an essential role in the cytosolic release of the C-domain. Because analogous CTF complexes have been partially purified from mammalian and yeast cell extracts, results presented here suggest a common and fundamental mechanism for C-domain translocation across early endosomal membranes.

Characterization of the thermal properties of powder particles using microthermal analysis

PURPOSE

Microthermal analysis is a recently introduced thermoanalytical technique whereby discrete regions of complex samples may be scrutinized at micron or submicron resolution. In this investigation, the novel use of the technique to study individual powder particles is described.

METHODS

A TA Instruments microthermal analyzer was used in local thermal analysis mode using a heating rate of 10 degrees C/s. Powder samples of crystalline ibuprofen, spray-dried salbutamol sulphate, spray-dried and crystalline trehalose, and two polymorphic forms of indometacin were studied using differential scanning calorimetry as a supportive technique as appropriate.

RESULTS

The ibuprofen showed a probe position discontinuity corresponding to the melting point of the material. Spray-dried salbutamol sulphate showed a discontinuity corresponding to decomposition but not to the glass transition, whereas both crystalline and amorphous trehalose showed a single discontinuity corresponding to physical collapse of the material. Studies using the alpha and gamma forms of indometacin showed that the technique was able to distinguish between the two polymorphic forms.

CONCLUSION

The study suggests that micro-TA may be used to assess interparticulate composition and homogeneity.

Design and development of a novel genetic probe for the analysis of repressor-operator interactions

While the native diphtheria tox promoter/operator (toxPO)-lacZ transcriptional fusion has allowed initial isolation and characterization of the diphtheria toxin repressor (DtxR), the low level of reporter gene expression has limited the detection and analysis of mutations affecting subtle changes in repressor-operator binding. In order to overcome this difficulty, we have constructed a novel hybrid promoter/operator-lacZ transcriptional fusion in which the "-35" and spacing of the tac promoter was fused to the "-10" and interrupted palindromic sequence of toxO. We show that the hybrid tacPtoxO is regulated by the transition metal ion-dependent DtxR and that lacZ expression is increased approximately 70-fold in the reporter strain Escherichia coli DH5alpha/lambdaRS45-tacPtoxO-lacZ relative to DH5alpha/lambdaRS45-toxPO-lacZ. In addition, we have constructed a transcriptional fusion between tacPtoxO and luc, pJL1. We have used pJL1 to program S30 extracts of E. coli in order to direct in vitro the coupled transcription and translation of luciferase. We demonstrate the utility of this in vitro system in providing a direct functional link between in vivo and in vitro observations with DtxR and mutants of DtxR, which display subtle changes in activity in a manner not previously possible.

The gonococcal fur regulon: identification of additional genes involved in major catabolic, recombination, and secretory pathways

In this study, we have characterized the in vitro binding of Neisseria gonorrhoeae Fur to several well-defined iron transport genes, as well as to additional genes involved in major catabolic, secretory, and recombination pathways of gonococci. The gonococcal Fur protein was recombinantly expressed in Escherichia coli HBMV119. Fur was isolated from inclusion bodies and partially purified by ion-exchange chromatography. Gonococcal Fur was found to bind to the promoter/operator region of a gene encoding the previously identified Fur-regulated periplasmic binding protein (FbpA) in a metal ion-dependent fashion, demonstrating that purified Fur is functional. In silico analysis of the partially completed gonococcal genome (FA1090) identified Fur boxes in the promoters of several genes, including tonB, fur, recN, secY, sodB, hemO, hmbR, fumC, a hypothetical gene (Fe-S homolog), and the opa family of genes. By using purified gonococcal Fur, we demonstrate binding to the operator regions of tonB, fur, recN, secY, sodB, hemO, hmbR, fumC, the Fe-S homolog gene, and the opa gene family as determined by an electrophoretic mobility shift assay. While gonococcal Fur was demonstrated to bind to the promoter regions of all 11 opa genes (opaA through -K), we did not detect binding of purified E. coli Fur with 8 of the 11 opa members, indicating that target DNA sequence specificities between these two closely related proteins exist. Furthermore, we observed differences in the relative strengths of binding of gonococcal Fur for these different genes, which most likely reflect a difference in affinity between gonococcal Fur and its DNA targets. This is the first report that definitively demonstrates the binding of gonococcal Fur to its own promoter/operator region, as well as to the opa family of genes that encode surface proteins. Our results demonstrate that the gonococcal Fur protein binds to the regulatory regions of a broad array of genes and indicates that the gonococcal Fur regulon is larger than originally proposed.

Structure function analysis of interleukin 7: requirement for an aromatic ring at position 143 of helix D

The residues located at the carboxyl terminus of helix D in interleukin-7 (IL-7) have previously been targeted as important for recruitment and binding to the gamma chain component of the IL-7 receptor (IL-7R). In this study, Trp 143 of helix D was mutated to His, Phe, Tyr and Pro and these mutants, along with a W143A mutant previously described, were studied to determine the effects on activation of DNA synthesis and binding affinity to IL-7R positive 2E8 cells. The W143F and W143Y mutants were similar to wild type IL-7 in their binding properties and retained 85% and 74% of their activating properties, respectively. In contrast, the W143H mutant possessed a lower binding affinity and a corresponding decrease in activation, the W143A mutant possessed an over 100-fold decreased binding affinity and some residual activation activity and the W143P mutant possessed a greatly decreased binding affinity and did not activate. These results strongly suggest an aromatic residue is required at position 143 for IL-7R binding and subsequent signal transduction.

Various levels of cross-resistance to Bacillus sphaericus strains in Culex pipiens (Diptera: Culicidae) colonies resistant to B. sphaericus strain 2362

We studied the cross-resistance to three highly toxic Bacillus sphaericus strains, IAB-59 (serotype H6), IAB-881 (serotype H3), and IAB-872 (serotype H48), of four colonies of the Culex pipiens complex resistant to B. sphaericus 2362 and 1593, both of which are serotype H5a5b strains. Two field-selected highly resistant colonies originating from India (KOCHI, 17,000-fold resistance) and France (SPHAE, 23,000-fold resistance) and a highly resistant laboratory-selected colony from California (GeoR, 36,000-fold resistance) showed strong cross-resistance to strains IAB-881 and IAB-872 but significantly weaker cross-resistance to IAB-59 (3- to 43-fold resistance). In contrast, a laboratory-selected California colony with low-level resistance (JRMM-R, 5-fold resistance) displayed similar levels of resistance (5- to 10-fold) to all of the B. sphaericus strains tested. Thus, among the mosquitocidal strains of B. sphaericus we identified a strain, IAB-59, which was toxic to several Culex colonies that were highly resistant to commercial strains 2362 and 1593. Our analysis also indicated that strain IAB-59 may possess other larvicidal factors. These results could have important implications for the development of resistance management strategies for area-wide mosquito control programs based on the use of B. sphaericus preparations.

How significant are primary sleep disorders and sleepiness in the chronic fatigue syndrome?

In order to study both the prevalence of Primary Sleep Disorders (PSD) and sleepiness, and their association to the Chronic Fatigue Syndrome (CFS), 46 unselected outpatients (34 women, mean age 36.5) were examined clinically and underwent two nights of all-night polysomnography and multiple sleep latency tests (MSLT). Forty-six percent presented with a Sleep Apnea/Hypopnea Syndrome Index (AHI>=5), 5% with a Periodic Limb Movements syndrome. No subject received a diagnosis of Narcolepsy or Idiopathic Hypersomnia. Thirty percent showed the presence of objective sleepiness as measured by MSLT<10 minutes. Objective and subjective measures of sleepiness were not associated with CFS, nor with the double diagnosis of CFS and a PSD. The presence of PSD or sleepiness was not associated with any of the clinical scales that were used to measure anxiety, depression, somatisation, physical or mental fatigue, or functional status impairment. Fifty-four percent of CFS patients had no PSD, and 69% no sleepiness. These patients could not be distinguished clinically from patients having a PSD or from those with sleepiness. Therefore, it is unlikely that CFS is simply a somatic expression of any PSD observed in our sample or of sleepiness per se.

Quantitative assessment of motor fatigue in amyotrophic lateral sclerosis

Motor fatigue is a common complaint in patients with amyotrophic lateral sclerosis (ALS), but is often excluded, unlike weakness, from the clinical assessment of these patients. This could be due to the complexity and often painful assessment techniques of this motor deficit. This study examines the feasibility of quantitative assessment of motor fatigue by modifying presently available force measurements. The relationship between weakness and fatigue in ALS patients was also examined. Fifty-four ALS patients and 39 normal control subjects performed 30 s of sustained maximal voluntary isometric contraction (MVIC) of elbow flexors (EF), knee extensors (NE), and ankle dorsiflexors (DF), using a computerized force measurement system and standardized testing procedures. Fatigue index (FI) was digitally calculated, from the force-time curve, as the percentage of MVIC unable to be sustained over the 30-s period. Fatigue was greater in ALS patients than in normal control (mean=23% vs. 15%) in all muscles including muscles that were not clearly weak. Weakness and fatigue were poorly correlated in ALS patients and may be independent measures of the pathogeneses of ALS.

Fluorescence versus white-light bronchoscopy for detection of preneoplastic lesions: a randomized study

BACKGROUND

There are no currently approved methods for the screening and early detection of lung cancer. We compared the ability of conventional white-light bronchoscopy (WLB) and laser-induced fluorescence endoscopy (LIFE) to detect preneoplastic lung lesions in a randomized trial in which both the order of the procedures and the bronchoscopists were randomly assigned.

METHODS

The study included high-risk subjects enrolled because of a cigarette smoking history of at least 30 pack-years, an air-flow obstruction, and either an abnormal sputum cytology (n = 48) or a previous or suspected lung cancer (n = 7). LIFE and WLB were performed on all patients. Biopsy specimens were assessed for histologic abnormalities, including the presence of angiogenic squamous dysplasia. All statistical tests were two-sided.

RESULTS

A total of 391 biopsy specimens were taken from the 55 patients. Thirty-two patients (58%; 95% confidence interval [CI] = 44% to 71%) had at least one biopsy with moderate or severe dysplasia, and 19 (59%; 95% CI = 41% to 76%) of these patients could be diagnosed based solely on the results of LIFE. LIFE was statistically significantly more sensitive than WLB for detecting moderate dysplasia or worse (68.8% versus 21.9%, respectively) (difference = 46.9%; 95% CI = 25% to 68%; P< .001). The relative sensitivities (WLB = 1.0) were 3.1 (95% CI = 1.6 to 6.3) for LIFE and 3.7 (95% CI = 1.9 to 7.3) for LIFE and WLB combined. LIFE was less specific than WLB (69.6% versus 78.3%, respectively; P = .45), but the difference was not statistically significant. The relative specificities (WLB = 1.0) were 0.9 for LIFE (95% CI = 0.6 to 1.3) and 0.6 (95% CI = 0.4 to 1.0) for LIFE and WLB combined. The results were similar regardless of the order of the procedures or the order of the bronchoscopists. Also, LIFE was better at identifying angiogenic squamous dysplasia lesions than WLB (detection ratio [DR], which indicates the relative likelihood of getting a positive result in a sample with dysplasia compared with one without, for LIFE = 1.39 [95% CI = 1.17 to 1.65] versus DR for WLB = 0.67 [95% CI = 0.38 to 1.21]).

CONCLUSION

LIFE was more sensitive than WLB in detecting preneoplastic bronchial changes in high-risk subjects. The prognostic implication of this finding is not yet clear.

Campylobacter jejuni enteritis

We report the development of Campylobacter jejuni enteritis in a patient with preexisting humoral and cellular immune recognition of C. jejuni antigens. This is one of few studies in which the immunologic status of a person with regard to C. jejuni before and after C. jejuni infection is directly compared, and it is the only study of which we are aware that includes measurements of cellular immunity. The findings may be important to Campylobacter vaccine development efforts.

The first-night effect may last more than one night

The first-night effect in sleep polysomnographic studies is usually considered to last for one night. However, a few observations have indicated that variables associated to rapid eye movement sleep take longer to stabilize. Notwithstanding, current opinion holds that second nights of recording can be used without restriction for research and clinical purposes. The goal of this study was to describe the dynamics of habituation to polysomnography in optimal conditions. Twenty-six young, carefully screened, healthy subjects were recorded in their home for four consecutive full polysomnographies. Repeated measures ANOVA were applied. Between the two first nights, while there were no differences in sleep duration in non-rapid eye movement sleep, marked modifications in corresponding spectral power were observed. The dynamics of adaptation of rapid eye movement sleep appeared to be a process extending up to the fourth night. Similar dynamics in NREMS and REMS homeostasis have been observed in sleep deprivation studies, and it appears that the same mechanisms may be responsible for the FNE. The longer habituation process of REMS in particular has important implications for sleep research in psychiatry.

Structured use of the median in the analytical measurement process

In the pharmaceutical industry, the process of measuring a product's attributes can be very complicated and the potential for an analytical mistake can be quite high. Often, an unexpected result leads to an investigation to assess the possibility that a mistake was made in the laboratory. Traditionally, the data generated in these investigations has been used, along with various outlier tests, to attempt to negate the original data. Sometimes, historical estimates of the S.D. of the analytical method are not available for use in outlier testing and the power of the outlier tests to detect true mistakes without such historical estimates is often very low due to the small amount of data available. This leads to a great deal of inconsistency in the amount of data that is further generated and how the data is ultimately handled in making a decision. Recently, FDA demands for consistent and objective laboratory investigations have raised concerns about these practices. An alternative approach, involving a systematic investigation strategy and data handling via the structured use of the median, is proposed in this paper. The operating characteristics of the traditional and proposed approaches are compared to show their similarity and the advantages of the proposed approach. It is strongly believed by the authors that the structured use of the median will lead to more consistent investigations and data handling, which will benefit industry, the FDA and ultimately, the consumer, by allowing more accurate decisions to be made more efficiently.

Methyl groups of thymine bases are important for nucleic acid recognition by DtxR

The expression of diphtheria toxin is controlled by the diphtheria toxin repressor (DtxR). Under conditions of high iron concentration, DtxR binds the tox operator to inhibit transcription. To study how DNA binding specificity is achieved by this repressor, we solved the crystal structure of the nickel(II) activated DtxR(C102D) mutant complexed with a 43mer DNA duplex containing the DtxR consensus binding sequence. Structural analysis of this complex and comparison with a previously determined DtxR(C102D)-Ni(II)-tox operator ternary complex revealed unusual van der Waals interactions between Ser37/Pro39 of the repressor helix-turn-helix (HTH) motif and the methyl groups of specific thymine bases in the consensus binding sequence. Gel mobility shift assays utilizing deoxyuridine modified duplex DNA probes proved the importance of these interactions: the four methyl groups shown to interact with Ser37/Pro39 in the crystal structure contribute a total of 3.4 kcal/mol to binding energy. Thus, in addition to making base-specific hydrogen-bonding interactions to the DNA through its Gln43 residue, DtxR also recognizes methyl groups at certain positions in the DNA sequence with its Ser37 and Pro39 side chains, to achieve binding specificity toward its cognate operator sequences.

Prostate cancer and other xenografts from cells in peripheral blood of patients

Good models for the investigation of human prostate cancer are few. Cells from approximately 9.2-21 ml of peripheral blood from patients with metastatic prostate cancer or metastatic colon cancer were injected s.c. into nude mice. Prostate cancer from 2 of 11 patients and colon cancer from 1 of 3 patients were found to be growing as metastases in the lungs of the nude mice. To our knowledge, this is the first report of the formation of xenografts from carcinoma cells taken directly from the peripheral blood of patients. Expanding circulating cancer cells with this approach may have important translational applications including: (a) development of models of human cancers; and (b) sampling of cancers from specific patients for novel molecular and therapeutic approaches.

Enhancement of diphtheria toxin potency by replacement of the receptor binding domain with tetanus toxin C-fragment: a potential vector for delivering heterologous proteins to neurons

This study describes the expression, purification, and characterization of a recombinant fusion toxin, DAB(389)TTC, composed of the catalytic and membrane translocation domains of diphtheria toxin (DAB(389)) linked to the receptor binding fragment of tetanus toxin (C-fragment). As determined by its ability to inhibit cellular protein synthesis in primary neuron cultures, DAB(389)TTC was approximately 1,000-fold more cytotoxic than native diphtheria toxin or the previously described fusion toxin, DAB(389)MSH. The cytotoxic effect of DAB(389)TTC on cultured cells was specific toward neuronal-type cells and was blocked by coincubation of the chimeric toxin with tetanus antitoxin. The toxicity of DAB(389)TTC, like that of diphtheria toxin, was dependent on passage through an acidic compartment and ADP-ribosyltransferase activity of the DAB(389) catalytic fragment. These results suggest that a catalytically inactive form of DAB(389)TTC may be useful as a nonviral vehicle to deliver exogenous proteins to the cytosolic compartment of neurons.

Comparative model building of interleukin-7 using interleukin-4 as a template: a structural hypothesis that displays atypical surface chemistry in helix D important for receptor activation

Using a combination of theoretical sequence structure recognition predictions and experimental disulfide bond assignments, a three-dimensional (3D) model of human interleukin-7 (hIL-7) was constructed that predicts atypical surface chemistry in helix D that is important for receptor activation. A 3D model of hIL-7 was built using the X-ray crystal structure of interleukin-4 (IL-4) as a template (Walter MR et al., 1992, J Mol Biol. 224:1075-1085; Walter MR et al., 1992, J Biol Chem 267:20371-20376). Core secondary structures were constructed from sequences of hIL-7 predicted to form helices. The model was constructed by superimposing IL-7 helices onto the IL-4 template and connecting them together in an up-up down-down topology. The model was finished by incorporating the disulfide bond assignments (Cys3, Cys142), (Cys35, Cys130), and (Cys48, Cys93), which were determined by MALDI mass spectroscopy and site-directed mutagenesis (Cosenza L, Sweeney E, Murphy JR, 1997, J Biol Chem 272:32995-33000). Quality analysis of the hIL-7 model identified poor structural features in the carboxyl terminus that, when further studied using hydrophobic moment analysis, detected an atypical structural property in helix D, which contains Cys 130 and Cys142. This analysis demonstrated that helix D had a hydrophobic surface exposed to bulk solvent that accounted for the poor quality of the model, but was suggestive of a region in IL-7 that maybe important for protein interactions. Alanine (Ala) substitution scanning mutagenesis was performed to test if the predicted atypical surface chemistry of helix D in the hIL-7 model is important for receptor activation. This analysis resulted in the construction, purification, and characterization of four hIL-7 variants, hIL-7(K121A), hIL-7(L136A), hIL-7(K140A), and hIL-7(W143A), that displayed reduced or abrogated ability to stimulate a murine IL-7 dependent pre-B cell proliferation. The mutant hIL-7(W143A), which is biologically inactive and displaces [125I]-hIL-7, is the first reported IL-7R system antagonist.

PACAP-38 is a chemorepellent and an agonist for the lysozyme receptor in tetrahymena thermophila

Pituitary adenylate cyclase activating peptide (PACAP-38) is a peptide hormone which functions in many mammalian systems, including the nervous and digestive systems. Using in vivo behavioral studies, we have found that this hormone functions as a chemore-pellent in Tetrahymena thermophila with an EC50 of 10 nM. Cells previously adapted to PACAP-38 were found to be adapted to lysozyme and vice versa. Furthermore, the in vivo behavioral activity of PACAP-38 was blocked by addition of the anti-lysozyme receptor antibody, 5545. Chemorepellent activity of PACAP-38 was also inhibited by the addition of neomycin sulfate (inhibition constant Ki = 0.080 micromol x l(-1)), a competitive inhibitor of lysozyme binding to its receptor. PACAP-38 is a more potent and specific agonist for the lysozyme receptor than either intact lysozyme or CB2, a 24-amino acid fragment of lysozyme.