Structural transitions of satellite tobacco mosaic virus particles

Satellite tobacco mosaic virus (STMV) can undergo at least two physical transitions that significantly alter its mechanical and structural characteristics. At high pH the 17-nm STMV particles expand radially by about 5 A to yield particles having diameters of about 18 nm. This pH-induced transition is further promoted by aging of the virions and degradation of the RNA, so that swollen particles ultimately appear even at neutral pH. While the native 17-nm particles crystallize as orthorhombic or monoclinic crystals which diffract to high resolution (1.8 A), the enlarged 18-nm particles crystallize in a cubic form which diffracts to no better than 5 A. In the transition, not only do the capsid protein subunits move radially outward, but the helical RNA segments with which they interact do as well. This is noteworthy because it demonstrates that the RNA and the protein shell are capable of coordinated movement, and that neither structure is rigidly defined or independent of the other. Using atomic force microscopy, it can be shown that STMV particles, upon drying, lose their mechanical rigidity and undergo deformation. Virions initially 17 nm in diameter shrink to more uniform final sizes than do 18 nm, initially swollen particles. This transition appears to be irreversible, as the particles do not reassume their former size nor structural rigidity upon rehydration. Evidence is also presented that preparations of native virus and their crystals are naturally somewhat heterogeneous and contain a variety of particles of anomalous size.

Bacterial DNA ligases

DNA ligases join breaks in the phosphodiester backbone of DNA molecules and are used in many essential reactions within the cell. All DNA ligases follow the same reaction mechanism, but they may use either ATP or NAD+ as a cofactor. All Bacteria (eubacteria) contain NAD+-dependent DNA ligases, and the uniqueness of these enzymes to Bacteria makes them an attractive target for novel antibiotics. In addition to their NAD+-dependent enzymes, some Bacteria contain genes for putative ATP-dependent DNA ligases. The requirement for these different isozymes in Bacteria is unknown, but may be related to their utilization in different aspects of DNA metabolism. The putative ATP-dependent DNA ligases found in Bacteria are most closely related to proteins from Archaea and viruses. Phylogenetic analysis suggests that all NAD+-dependent DNA ligases are closely related, but the ATP-dependent enzymes have been acquired by Bacterial genomes on a number of separate occasions.

X-ray diffraction and atomic force microscopy analysis of twinned crystals: rhombohedral canavalin

The structure of canavalin, the vicilin-class storage protein from jack bean, was refined to 1.7 A resolution in a highly twinned rhombohedral crystal of space group R3 and unit-cell parameters a = b = c = 83.0 A, alpha = beta = gamma = 111.1 degrees. The resulting R and R(free) were 0.176 and 0.245, respectively. The orthorhombic crystal structure (space group C222(1), unit-cell parameters a = 136.5, b = 150.3, c = 133.4 A) was also refined with threefold non-crystallographic symmetry restraints. R and R(free) were 0.181 and 0.226, respectively, for 2.6 A resolution data. No significant difference in the protein structure was seen between these two crystal forms, nor between these two and the hexagonal and cubic crystal forms reported elsewhere [Ko et al. (1993), Acta Cryst. D49, 478-489; Ko et al. (1993), Plant Physiol. 101, 729-744]. A phosphate ion was identified in the lumen of the C-terminal beta-barrel. Lattice interactions showed that the trimeric molecule could be well accommodated in both 'top-up' and 'bottom-up' orientations in a rhombohedral unit cell of the R3 crystal and explained the presence of a high twin fraction. The large inter-trimer stacking interface of the C222(1) crystal may account for its relative stability. Atomic force microscopy (AFM) investigations of the growth of three crystal forms of canavalin indicate the rhombohedral form to be unique. Unlike the other two crystal forms, it contains at least an order of magnitude more screw dislocations and stacking faults than any other macromolecular crystal yet studied, and it alone grows principally by generation of steps from the screw dislocations. The unusually high occurrence of the screw dislocations and stacking faults is attributed to mechanical stress produced by the alternate molecular orientations in the rhombohedral crystals and their organization into discrete domains or blocks. At boundaries of alternate domains, lattice strain is relieved by the formation of the screw dislocations.

E-mail: a new management parameter

E-mail is an increasingly common way to share information within business communities and the general population. This technology can significantly affect the process of and expectations for communications between the clinician and the patient. The unique characteristics and attributes of computer-based communications can ultimately enhance outcomes for patient well-being if the clinician is informed, proactive, and avoids certain potential pitfalls related to the technology and its inclusion within the pattern of care. In this article the author considers the impact of E-mail on personal and professional life and includes ideas the reader may find of value in managing and orchestrating this new dimension for communications.

Biophysical studies on the RNA cores of satellite tobacco mosaic virus

Satellite tobacco mosaic virus (STMV) was probed using a variety of proteases. Consequences of the degradation were analyzed using gel electrophoresis, quasi-elastic light scattering (QELS), and atomic force microscopy (AFM). Proteolysis rates of 30 minutes for complete degradation of the protein capsid, up to many hours, were investigated. With each protease, degradation of virions 17 nm in diameter was shown by QELS to result in particles of 10 nm diameter, which is that of the RNA core observed in the virion by x-ray diffraction analysis. This was verified by direct visualization with atomic force microscopy. Using QELS, it was further shown that freshly prepared RNA cores remain as individual, stable, 10-nm condensed particles for 12 to 24 h. Clusters of particles then formed, followed by very large aggregates of 500 to 1000 nm diameter. AFM showed that the aggregates were composed of groups of the condensed RNA cores and were not due to unfolding of the nucleic acid. No unfolding of the core particles into extended conformation was seen by AFM until the samples were heated well beyond 90 degrees C. Mass spectrometry of RNA core particles revealed the presence of a major polypeptide whose amino acid sequence corresponded to residues 2 through 25 of the coat protein. Amino acids 13 through 25 were previously observed to be in direct contact with the RNA and are presumably protected from protease digestion. Low resolution difference Fourier analyses indicated the courses of the remainders of the amino terminal strands (amino acids 2-12) in intact virions. Any individual strand appears to have several choices of path, which accounts for the observed disorder at high resolution. These positively charged strands, serving as virtual polyamines, engage the helical segments of RNA. The intimate association of amino acid residues 2 through 25 with RNA likely contributes to the stability of the condensed conformation of the nucleic acid cores.

Privacy and personal health data in cyberspace

In this series of articles, the author discusses the potential risks, benefits, and liabilities associated with using electronic communications and computer-based records to manage a patient's medical information. This second article in the series considers the role and responsibility of the healthcare professional in collecting and sharing a patient's private personal and medical data in online environments. Current practices and the potential pitfalls of Electronic Data Interchange (EDI) are reviewed.

Evidence on the efficacy of insert earphone and sound field VRA with young infants

Visual reinforcement audiometry (VRA) with insert-earphone stimulus delivery provides a means of obtaining early ear-specific information on the auditory status of infants. The aim of this study was to investigate the efficacy of VRA in young infants, and to compare the use of sound field and insert-earphone stimulus presentation. VRA was performed on 41 normally developing infants aged between 20 and 42 weeks. Infants were tested in the sound field (n=22) and with insert earphones (n=19). Results showed significantly more minimum response levels (MRLs) obtained with sound field testing, and with older children. Nevertheless, in the insert-earphone group, 36% of those aged 32 weeks or more gave two or more MRLs, and 25% of the infants aged 25 weeks or less gave one or more MRLs. This study provides data from developmentally normal infants which confirms the efficacy of insert-earphones as well as sound field VRA with 32-42-week-olds, with reasonable expectation of success. The data in this study also suggest that VRA could be usefully employed for younger infants aged approximately 20-26 weeks where information, although less easily obtained, may be of particular value to early diagnosis and habilitation.

Cyberinfo: privacy and personal health data in cyberspace

In this series of articles, the author discusses the potential risks, benefits, and liabilities in using electronic communications and computer-based record keeping for patients' medical data. Article #1 in this series reviews the foundations of privacy for personal information and the current practices of collecting disaggregated private personal and medical data made possible on the Internet by software and hardware configurations.

Refined structure of desmodium yellow mottle tymovirus at 2.7 A resolution

Desmodium yellow mottle virus is a 28 nm diameter, T=3 icosahedral plant virus of the tymovirus group. Its structure has been solved to a resolution of 2.7 A using X-ray diffraction analysis based on molecular replacement and phase extension methods. The final R value was 0.151 (R(free)=0.159) for 134,454 independent reflections. The folding of the polypeptide backbone is nearly identical with that of turnip yellow mosaic virus, as is the arrangement of subunits in the virus capsid. However, a major difference in the disposition of the amino-terminal ends of the subunits was observed. In turnip yellow mosaic virus, those from the B and C subunits comprising the hexameric capsomeres formed an annulus about the interior of the capsomere, while the corresponding N termini of the pentameric capsomere A subunits were not visible at all in electron density maps. In Desmodium yellow mottle tymovirus, amino termini from the A and B subunits combine to form the annuli, thereby resulting in a much strengthened association between the two types of capsomeres and an, apparently, more stable capsid. The first 13 residues of the C subunit were invisible in electron density maps. Two ordered fragments of single-stranded RNA, seven and two nucleotides in length, were observed. The ordered water structure of the virus particle was delineated and required 95 solvent molecules per protein subunit.

Chimeric human-simian anti-CD4 antibodies form crystalline high symmetry particles

A chimeric human-simian IgG, antigen specific for CD4, when exposed to 0.5 M SO(=)(4) containing 0.4% polyethylene glycol or Jeffamine, self-assembles into discreet, roughly spherical particles 23 nm in diameter. Increasing SO(=)(4) to 1.55 M induces the IgG particles to crystallize in either a hexagonal or a monoclinic form. From X-ray diffraction, the former crystal is of space group P622, with one IgG particle in the unit cell; thus the particle itself must have 622 point group symmetry. Both crystal forms have been imaged using atomic force microscopy. Detailed features of the duodecamer were evident, including the symmetry and a large solvent channel along the sixfold axis. The particles in some ways resemble the hexameric IgG aggregates believed to activate compliment upon antigen binding and, therefore, may have physiological relevance. Investigation of seven other IgGs of diverse origins and subclasses indicates that many, if not most, IgGs form similar particles. To our knowledge, this is the first observation of the assembly of IgG into high symmetry aggregates in the absence of antigen or their crystallization.

Immune responses to a recombinant human immunodeficiency virus type 1 (HIV-1) gpl60 vaccine among adults with advanced HIV infection. Massachusetts gp160 Working Group

OBJECTIVE

To assess immunogenicity of recombinant human immunodeficiency virus type 1 (HIV-1) envelope vaccine (rgp160) in late HIV infection.

STUDY DESIGN/METHODS

HIV-infected volunteers (n = 142), with CD4+ T lymphocyte counts of <400/mm3, were enrolled in a dose-comparison, open-label trial with stratification by CD4+ cell count, randomization to a primary series at two dose levels, and a sub-group receiving interferon-gamma (IFN-gamma) as an adjuvant. Subjects received booster doses of vaccine over a follow-up period of 18-28 months.

RESULTS

At 6 and 12 months, 36% and 38% of participants, respectively, had new or augmented antibody titers (> or =4-fold increase) against one or more gpl60 epitopes (C1, V3, C41, 448C). Delayed-type hypersensitivity (DTH) to intradermal gpl60, initially not present in any participant, developed after immunization in 41%, with higher prevalence in participants receiving the lower dose of vaccine. Both antibody and skin test responses occurred in 20-25% of vaccine recipients. Virtually all antibody and skin test responses occurred in participants with initial CD4+ cell counts of >100 cells/mm3. IFN-gamma had no significant effect on immune response. Immunization was well tolerated. Trends in CD4+ cell count, clinical events, and laboratory findings correlated with baseline CD4+ T lymphocyte count stratum and not with immunization regimen. Opportunistic conditions occurred at expected rates. Viral load trends (p24 antigen in all participants and viral RNA by reverse transcription-polymerase chain reaction in a subset of 26 participants) did not correlate with immunization regimen.

CONCLUSION

Immunization of patients with advanced HIV infection with rgpl60 resulted in new and augmented humoral and DTH responses, without unexpected significant adverse events or evident clinical benefits attributable to immunization.

The refined structure of canavalin from jack bean in two crystal forms at 2.1 and 2.0 A resolution

The structure of canavalin was refined to 2.1 and 2.0 A resolution in cubic and hexagonal crystals of space group P2(1)3 and P6(3), respectively. The threefold molecular symmetry is expressed in the symmetry of both crystals, where each identical subunit is an asymmetric unit. The canavalin subunit consists of two very similar domains, each comprised of a core subdomain having Swiss-roll topology with a loop subdomain that contains helices. The refined canavalin models resolved the discrepancy in amino-acid registers of the secondary-structural elements compared with phaseolin. The presence of strand Z in both domains of canavalin was confirmed and a new helix in the loop between strands A and B of each domain was observed. The models were analyzed in terms of the duplicated vicilin domains. Three strictly conserved residues, two glycines and a proline, were identified. The similarity between entire vicilin molecules is greater than that between separate domains of canavalin and phaseolin. Homology modeling of the sucrose-binding protein (SBP) from soybean showed a plausible trimeric assembly of subunits similar to that of vicilins.

Universal DNA microarray method for multiplex detection of low abundance point mutations

Cancers arise from the accumulation of multiple mutations in genes regulating cellular growth and differentiation. Identification of such mutations in numerous genes represents a significant challenge in genetic analysis, particularly when the majority of DNA in a tumor sample is from wild-type stroma. To overcome these difficulties, we have developed a new type of DNA microchip that combines polymerase chain reaction/ligase detection reaction (PCR/LDR) with "zip-code" hybridization. Suitably designed allele-specific LDR primers become covalently ligated to adjacent fluorescently labeled primers if and only if a mutation is present. The allele-specific LDR primers contain on their 5'-ends "zip-code complements" that are used to direct LDR products to specific zip-code addresses attached covalently to a three-dimensional gel-matrix array. Since zip-codes have no homology to either the target sequence or to other sequences in the genome, false signals due to mismatch hybridizations are not detected. The zip-code sequences remain constant and their complements can be appended to any set of LDR primers, making our zip-code arrays universal. Using the K- ras gene as a model system, multiplex PCR/LDR followed by hybridization to prototype 3x3 zip-code arrays correctly identified all mutations in tumor and cell line DNA. Mutations present at less than one per cent of the wild-type DNA level could be distinguished. Universal arrays may be used to rapidly detect low abundance mutations in any gene of interest.

Structure of orthorhombic crystals of beef liver catalase

The growth mechanisms and physical properties of the orthorhombic crystal form of beef liver catalase were investigated using in situ atomic force microscopy (AFM). It was observed that the crystals grow in the <001> direction by an unusual progression of sequential two-dimensional nuclei of half unit-cell layers corresponding to the 'bottoms' and 'tops' of unit cells. These were easily discriminated by their alternating asymmetric shapes and their strong growth-rate anisotropy. This pattern has not previously been observed with other macromolecular crystals. Orthorhombic beef liver catalase crystals exhibit an extremely high defect density and incorporate great numbers of misoriented microcrystals, revealed intact by etching experiments, which may explain their marginal diffraction properties. To facilitate interpretation of AFM results in terms of intermolecular interactions, the structure of the orthorhombic crystals, having an entire tetramer of the enzyme as the asymmetric unit, was solved by molecular replacement using a model derived from a trigonal crystal form. It was subsequently refined by conventional techniques. Although the packing of molecules in the two unit cells was substantially different, with very few exceptions no significant differences in the molecular structures were observed. In addition, no statistically significant deviation from ideal 222 molecular symmetry appeared within the tetramer. The packing of molecules in the crystal revealed by X-ray analysis explained in a satisfying way the process of crystal growth revealed by AFM.

Conditions in rural Nepal for which depot-medroxyprogesterone acetate initiation is not recommended: implications for community-based service delivery

The presence of medical conditions that might affect the use of depot-medroxyprogesterone acetate (DMPA) as a contraceptive method was assessed in a rural district in Nepal. A general health survey was conducted in nonpregnant and noncontracepting women aged 15-44 years to determine the presence of any health problems. The survey included a general assessment interview by nonphysicians, followed by formal medical histories and physical exams by female gynecologists. Possible pregnancy (nine cases) and abnormal uterine bleeding (one case) were the only conditions identified in which DMPA should not be used, based on the World Health Organization (WHO) Medical Eligibility Criteria for Contraceptive Use. Five additional cases of cardiovascular problems, in which DMPA initiation is not usually recommended, were also detected. Recently developed checklists based on the WHO criteria for DMPA use would have identified all of these health conditions. This checklist would allow the safe delivery of DMPA at the community health worker level, and increase the availability and accessibility of DMPA in rural Nepal.

Pros and cons of the use of antihistamines in managing allergic rhinitis

Histamine H1 -receptor antagonists are generally considered first-line therapy for the management of allergic rhinitis. Other than histamine antagonism, several of the second-generation antihistamines have also shown inhibitory effects on chemical mediators of inflammation such as leukotrienes, prostaglandins, and kinins. This article reviews the pharmacology, clinical use, and side effect profiles of the commonly used H1 -receptor antagonists.

Multiplex PCR/LDR for detection of K-ras mutations in primary colon tumors

Point mutations in codons 12, 13, and 61 of the K-ras gene occur early in the development of colorectal cancer and are preserved throughout the course of tumor progression. These mutations can serve as biomarkers for shed or circulating tumor cells and may be useful for diagnosis of early, curable tumors and for staging of advanced cancers. We have developed a multiplex polymerase chain reaction/ligase detection reaction (PCR/LDR) method which identifies all 19 possible single-base mutations in K-ras codons 12, 13, and 61, with a sensitivity of 1 in 500 wild-type sequences. In a blinded study, 144 paraffin-embedded archival colon carcinomas were microdissected and K-ras mutations determined by both dideoxy-sequencing and multiplex PCR/LDR. Results were concordant for 134 samples. The ten discordant samples were re-evaluated using higher sensitivity uniplex PCR/LDR, and the original multiplex PCR/LDR result was confirmed in nine of these ten cases. Multiplex PCR/LDR was able to identify mutations in solid tumors or paraffin-embedded tissues containing a majority of wild-type stromal cells, with or without microdissection. The technique is well suited for large scale studies and for analysis of clinical samples containing a minority population of mutated cells.

The neurosteroid pregnenolone sulfate infused into the nucleus basalis increases both acetylcholine release in the frontal cortex or amygdala and spatial memory

The effects of an infusion (5 ng) of the neurosteroid pregnenolone sulfate into the nucleus basalis magnocellularis on acetylcholine release in the frontoparietal cortex and basolateral amygdala were evaluated during the 130 min post-injection in male Sprague-Dawley rats using in vivo microdialysis coupled "on line" with high performance liquid chromatography detection. One week later, the same animals were tested for spatial memory after another infusion of pregnenolone sulfate (5 ng) into the nucleus basalis. Results show that pregnenolone sulfate enhanced acetylcholine release by more than 50% of baseline concentrations in the two structures relative to a control injection. The duration of this effect was longer in cortex (130 min) than in amygdala (30 min). Furthermore, pregnenolone sulfate improved memory performance in a task based upon spatial recognition of a familiar environment. A significant positive correlation (r=0.49) was found between the recognition score in the spatial memory test and the levels of acetylcholine release in the frontoparietal cortex but not in the basolateral amygdala. Therefore, our results suggest that the nucleus basalis magnocellularis-cortical pathway could be in part responsible for the promnesic effect of pregnenolone sulfate. This neurosteroid acts as a negative modulator of the GABA(A) receptor complex and positively modulates the N-methyl-D-aspartate receptor, possibly resulting in a global stimulatory effect on central cholinergic neurotransmission.

Comparison of the efficacy of budesonide and fluticasone propionate aqueous nasal spray for once daily treatment of perennial allergic rhinitis

BACKGROUND

Intranasal corticosteroids, such as budesonide and fluticasone propionate, are widely prescribed in the treatment of perennial allergic rhinitis. Once daily budesonide dry powder and fluticasone propionate aqueous suspension have been found to provide similar efficacy in controlling symptoms of perennial allergic rhinitis.

OBJECTIVE

The purpose of this study was to assess the efficacy and safety of treatment with once daily budesonide aqueous nasal spray.

METHODS

This study involved a multicenter, blinded, randomized, parallel-group, placebo-controlled trial of adults with perrenial allergic rhinitis. Patients (n = 273) recorded daily nasal symptoms for 8 to 14 days (baseline) and 6 weeks (treatment).

RESULTS

Budesonide decreased combined symptoms to a significantly greater extent than did fluticasone (P =.03); both treatments significantly decreased mean combined nasal symptoms scores compared with placebo. Of the 3 nasal symptoms assessed (ie, nasal blockage, runny nose, and sneezing), nasal blockage was significantly (P =. 009) more decreased with budesonide compared with fluticasone. Both treatments also significantly improved runny nose and sneezing compared with placebo. Improvement in combined nasal symptom scores of the budesonide-treated group reached statistical significance within 36 hours compared with placebo (P =.01); in those patients treated with fluticasone, significant improvement compared with placebo was first observed within 60 hours. Adverse events were mild and transient.

CONCLUSIONS

Once daily budesonide aqueous nasal spray, 256 microgram, was significantly better in controlling the symptoms of perrenial allergic rhinitis than once daily fluticasone propionate, 200 microgram, especially nasal blockage. Both treatments were superior to placebo. Budesonide may have a faster onset of action than fluticasone.

Efficacy of a sonic toothbrush for plaque removal by caregivers in a special needs population

Oral hygiene and oral health are a major concern for long-term-care facility residents who are unable to care for themselves. In this six-week study, the efficacy of a sonic toothbrush (Sonicare) was compared with traditional manual brushing in a setting where hygiene care was provided by caregivers. Evaluations of plaque levels were made at baseline and at 2, 4, and 6 weeks according to the Silness and Löe index. The sonic brush was found to be significantly superior to the manual brush over the trial period (MANCOVA; p = 0.026). Plaque reduction at 6 weeks was found to be 38% with the sonic brush and 6% with the manual brush. The results indicate that the sonic brush may be an effective way to provide improved oral health to nursing home subjects when oral care is caregiver-provided.

Effects of nicotine on methadone self-administration in humans

The effects of nicotine abstinence, ad libitum smoking, and 0, 2, and 4 mg nicotine gum on methadone self-administration were investigated. Five methadone-maintained patients with a history of smoking (18-30 cigarettes/day) were recruited as subjects. Upon arrival expired carbon monoxide levels were measured to confirm self-reported abstinence of 10-12 h. At 30 min prior to the methadone self-administration session, two response options were concurrently available. When a 64-button press requirement (FR64) was completed, 10 ml of 0.054 mg/ml methadone solution, or vehicle, was delivered. Immediately following, and 30, 60, 90, and 120 min after the self-administration session, expired carbon monoxide levels and typical symptoms of nicotine withdrawal were assessed. Relative to abstinence, subjects consumed more methadone following the 4-mg nicotine gum and ad libitum smoking conditions. Ratings of cigarette craving were significantly less following ad libitum smoking or administration of 4-mg nicotine gum, than following abstinence. Implications for understanding opioid and nicotine interactions are discussed.

Refined structure of satellite tobacco mosaic virus at 1.8 A resolution

The molecular structure of satellite tobacco mosaic virus (STMV) has been refined to 1.8 A resolution using X-ray diffraction data collected from crystals grown in microgravity. The final R value was 0.179 and Rfree was 0.184 for 219,086 independent reflections. The final model of the asymmetric unit contained amino acid residues 13 to 159 of a coat protein monomer, 21 nucleotides, a sulfate ion, and 168 water molecules. The nucleotides were visualized as 30 helical segments of nine base-pairs with an additional base stacked at each 3' end, plus a "free" nucleotide, not belonging to the helical segments, but firmly bound by the protein. Sulfate ions are located exactly on 5-fold axes and each is coordinated by ten asparagine side-chains. Of the 10,080 structural waters, 168 per asymmetric unit, about 20% serve to bridge the macromolecular components at protein-protein and protein-nucleic acid interfaces. Binding of RNA to the protein involves some salt linkages, particularly to the phosphate of the free nucleotide, but the major contribution is from an intricate network of hydrogen bonds. There are numerous water molecules in the RNA-protein interface, many serving as intermediate hydrogen bond bridges. The sugar-phosphate backbone contributes most of the donors and acceptors for the RNA. The helical RNA conformation is nearest that of A form DNA. The central region of a helical segment is most extensively involved in contacts with protein, and exhibits low thermal parameters which increase dramatically toward the ends. The visible RNA represents approximately 59% of the total nucleic acid in the virion and is derived from the single-stranded genome, which has folded upon itself to form helical segments. Linking of the helices and the free nucleotides in a contiguous and efficient manner severely restricts the disposition of the remaining, unseen nucleic acid. Using the remaining nucleotides it is possible to fold the RNA according to motifs that provide a periodic distribution of RNA structural elements compatible with the icosahedrally symmetrical arrangement seen in the crystallographic structure. The intimate relationship between protein and nucleic acid in STMV suggests an assembly pathway based on the cooperative and coordinated co-condensation of RNA with capsid protein dimers.

Comparative analysis of thaumatin crystals grown on earth and in microgravity

The protein thaumatin was studied as a model macro-molecule for crystallization in microgravity-environment experiments conducted on two US Space Shuttle missions (USML-2 and LMS). In this investigation, we have evaluated and compared the quality of space- and earth-grown thaumatin crystals using X-ray diffraction analyses, and characterized them according to crystal size, diffraction resolution limit and mosaicity. Two different approaches for growing thaumatin crystals in the microgravity environment, dialysis and liquid-liquid diffusion, were employed as a joint experiment by our two investigative teams. Thaumatin crystals grown in a microgravity environment were generally larger in volume and the total number of crystals was less, relative to crystals grown on earth. They diffracted to significantly higher resolution and with improved diffraction properties, as judged by relative plots of I/sigma versus resolution. The mosaicity of space-grown crystals was significantly less than that of crystals grown on earth. Increased concentrations of protein in the crystallization chambers in microgravity led to larger crystals. The data presented here lend further support to the idea that protein crystals of improved quality can be obtained in a microgravity environment.

Serum free prostate-specific antigen in the diagnosis of prostate cancer

OBJECTIVE

To determine the value of the ratio of free prostate-specific antigen (fPSA) to total PSA (tPSA) in the diagnosis of benign prostatic hyperplasia (BPH) and prostate cancer in a cohort of patients undergoing prostatic transrectal ultrasonography (TRUS).

PATIENTS AND METHODS

The study comprised 153 patients (99 with BPH and 54 with prostate cancer) undergoing diagnostic TRUS of the prostate. Patients with a tPSA of > 30 ng/mL were excluded from analysis. Free PSA was assayed using an immunoassay specific for unbound PSA (CanAg Diagnostics, Sweden). Total PSA was measured using the HybriTech Tandem-R PSA immunoradiometric assay in routine clinical use and this estimate was validated using the CanAg tPSA assay.

RESULTS

The measurements of tPSA from both assay systems correlated closely. The f/tPSA ratios in patients with prostate cancer were significantly lower than in those with BPH (median values 0.152 and 0.2, respectively, P<0.01). In patients with prostate cancer, the median f/t PSA levels apparently declined with increasing tPSA levels but in those with BPH, the levels of tPSA were not significantly associated with the f/tPSA ratio; the ratios did not vary significantly with age in either group. A f/tPSA ratio at a threshold of 0.16 had positive and negative predictive values of 44% and 74%, respectively; the corresponding values for a tPSA of > 4 ng/mL were 30% and 52%.

CONCLUSION

The f/tPSA ratio differs significantly between patients with BPH and cancer but because there is a considerable overlap of f/tPSA ratios between the groups, f/tPSA values alone were not sufficiently specific to be used as a single diagnostic test.

The crystallographic structure of the subtilisin protease from Penicillium cyclopium

The major extracellular protease from the fungus Pencillium cyclopium was crystallized in the presence of p-phenylmethanesulfonyl fluoride (PMSF) and investigated by X-ray diffraction analysis. It was subsequently cloned and the amino acid sequence deduced from its cDNA. Although the sequence is only 49% identical to that of proteinase K of Tritirachium album, the three-dimensional structures of the two proteases are virtually identical. The model for P. cyclopium protease was refined by simulated annealing to an R of 18% at 1.7 A resolution. The greatest variation from the proteinase K polypeptide is in loop 114-134 and is due to the absence of a disulfide bridge in the P. cyclopium protease that is present in proteinase K. A difference was also observed in the orientation of the histidine in the catalytic triad, though this could be due to the presence of PMSF at the active site. The coordination geometry of the strongly bound calcium in the P. cyclopium protease is octahedral and uses some different protein ligands than does proteinase K. In the protease from P. cyclopium there is no cysteine near the active site, nor is there a second calcium binding site as is found in proteinase K, suggesting that neither is important to catalytic activity.

Crystallization of Xylanase fromErwinia chrysanthemi: Influence of Heat and Polymeric Substrate

Xylanase from the bacterial plant pathogen Erwinia chrysanthemi (E.C. 3.2.1.8), expressed in E. coli, has been crystallized for X-ray diffraction analysis both in the presence and the absence of its polymeric substrate 4-O-methyl glucuronoxylan. In all cases it was found that the quality, time of appearance, and reproducibility of both the native and complex crystals were significantly enhanced by heating of the protein to 323 K prior to dispensing the crystallization trials. Crystals of the native protein are ideal for X-ray diffraction analysis, producing Bragg reflections beyond 1.5 A resolution with virtually no degradation with time. The native crystals are in space group P2(1), with a = 39.33, b = 49.46, c = 90.85 A and beta = 101.58 degrees. Other polymorphs have also been obtained and their cell parameters determined. Crystallization of the enzyme in the presence of polymeric substrate yields two distinctly different crystals at different concentrations of the xylan. These are thought to be complexes of the protein with stable products of the enzymatic reaction. A similar result had been obtained previously with pancreatic alpha-amylase and its substrate glycogen.

Population genetics of the D4S139, D10S28, D17S74 and D17S79 VNTR loci among Asian, black, Caucasian, Hispanic and Native American populations from Seattle

We studied four variable number of tandem repeat (VNTR) loci (D4S139, D10S28, D17S74, and D17S79) in five ethnic populations from the Seattle metropolitan area. DNA samples purified from randomly chosen individuals were digested with Hae III or Hinf I and probed with pH30, for D4S139; TBQ7 for D10S28; pCMM86 for D17S74 and pAC256 for D17S79. The allele frequencies, expected Hardy-Weinberg values, observed heterozygosities and genetic distances among the populations were obtained for all these loci. D4S139 restriction fragment lengths (RFLs) varied in size from 1.4 to 22 kilobase pairs (kbp). The observed heterozygosities (H) varied from 84% in Native American populations to 94% among Blacks. D10S28 RFLs varied in size from 650 base pairs (bp) to 10.1 kbp. H varied from 90% in Native Americans to 96% in Caucasians and Hispanics. D17S74 RFLs varied in size from 782 bp to 9.3 kbp. H varied from 87% in Asians to 92% among Blacks. D17S79 RFLs varied in size from 400 bp to 3 kbp. H varied from 87% in Hispanics to 95% in the Black population. The frequencies of genotypes of the loci conformed to Hardy-Weinberg equilibrium with the exception of the D17S79 in Hispanics and Native Americans. The genetic distances between the populations were also determined.

The open conformation of a Pseudomonas lipase

BACKGROUND

. The interfacial activation of lipases results primarily from conformational changes in the enzymes which expose the active site and provide a hydrophobic surface for interaction with the lipid substrate. Comparison of the crystallization conditions used and the structures observed for a variety of lipases suggests that the enzyme conformation is dependent on solution conditions. Pseudomonas cepacia lipase (PCL) was crystallized in conditions from which the open, active conformation of the enzyme was expected. Its three-dimensional structure was determined independently in three different laboratories and was compared with the previously reported closed conformations of the closely related lipases from Pseudomonas glumae (PGL) and Chromobacterium viscosum (CVL). These structures provide new insights into the function of this commercially important family of lipases.

RESULTS

. The three independent structures of PCL superimpose with only small differences in the mainchain conformations. As expected, the observed conformation reveals a catalytic site exposed to the solvent. Superposition of PCL with the PGL and CVL structures indicates that the rearrangement from the closed to the open conformation involves three loops. The largest movement involves a 40 residue stretch, within which a helical segment moves to afford access to the catalytic site. A hydrophobic cleft that is presumed to be the lipid binding site is formed around the active site.

CONCLUSIONS

. The interfacial activation of Pseudomonas lipases involves conformational rearrangements of surface loops and appears to conform to models of activation deduced from the structures of fungal and mammalian lipases. Factors controlling the conformational rearrangement are not understood, but a comparison of crystallization conditions and observed conformation suggests that the conformation of the protein is determined by the solution conditions, perhaps by the dielectric constant.

Clinical, biochemical, and molecular investigations of a genetic isolate of growth hormone insensitivity (Laron's syndrome)

We have characterized the GH receptor mutation that is responsible for extreme short stature and GH insensitivity in a Bahamian genetic isolate. Heights of affected individuals ranged from -4.0 to -6.3 SD. Like others with Laron's syndrome, they had normal to high serum GH concentrations and low serum insulin-like growth factor I concentrations. Circulating levels of GH-binding protein activity were below limits of detection. Amplification of exons 2-7 and screening with single strand conformational polymorphism analysis located an abnormality in exon 7. Sequencing identified homozygosity for a C to T transition in the third position of codon 236. Reverse transcription and PCR amplification of complementary DNA from lymphocytes showed that this same sense mutation generated a new splice donor site 63 bp 5' to the normal exon 7 splice site. This novel site was used to the exclusion of the normal site in homozygotes. Both normal and variant messenger ribonucleic acid species were detected in heterozygotes. The predicted protein lacks 21 amino acids, including those defining the WS-like motif of the GH receptor extracellular domain. The high frequency of Laron's syndrome in this isolated island population probably reflects the introduction of the G236 splice mutation by a settler early in the 300-yr history of English settlement.

An audit of pain management in acute sickle cell crisis

People undergoing sickle cell crisis can experience extreme pain that is not always managed effectively. This article describes an audit of pain management in sickle cell disease that was used to generate practice guidelines. A subsequent audit of pain management for this client group demonstrated improvements in the quality of care delivered.

Budesonide aqueous nasal spray and pressurized metered dose inhaler in the treatment of adult patients with seasonal allergic rhinitis

Budesonide, a topical corticosteroid used in the treatment of seasonal allergic rhinitis, can be administered to the nose as an aerosol via a pressurized metered dose inhaler (pMDI) or as a metered nasal pump spray. Studies have shown that about 64% (256 micrograms) of a nominal dose of 400 micrograms budesonide pMDI preparation is delivered to the patient compared with 100% of the nominal dose of the pump spray. The present study was undertaken to assess the efficacy and safety of budesonide delivered via a nasal pMDI twice daily (Rhinocort pMDI, at 400 micrograms/day) with an aqueous suspension of budesonide delivered via a metered nasal pump spray once daily (Rhinocort Aqua, at 256 micrograms/day or 400 micrograms/day). The multicenter, double-blind, randomized, placebo-controlled, parallel-group study was conducted in 318 patients (154 men, 164 women; aged 12-67 years) with ragweed-induced seasonal allergic rhinitis. A 1-week baseline period was followed by a 3-week treatment. Nasal symptoms were recorded by the patients, adverse events were noted, an overall evaluation of treatment efficacy was made, and urine cortisol and creatinine levels were measured. Substantial or total control of symptoms was achieved in 83.8% of patients treated with 256 micrograms of aqueous budesonide, 76.3% with 400 micrograms of aqueous budesonide, and 80.8% with 400 micrograms of budesonide pMDI; these were all significantly different (p < 0.001) compared with placebo (23.4% of patients). There were no significant differences in the 24-hour urine cortisol levels between the groups and there were few, infrequent adverse events, similar between the groups and resolved completely on discontinuation of treatment. It was concluded that budesonide, given once daily as 256 micrograms or 400 micrograms in an aqueous suspension or twice daily as 400 micrograms in a pMDI provides good alleviation of the symptoms of seasonal allergic rhinitis with no significant risk of suppression of urine cortisol.

Early and later adoptions have different long-term effects on male rat offspring

Both prenatal and postnatal environmental factors exert complex influences on the development of an organism. Previous studies have demonstrated that intervening events during the prenatal period can have different and even opposite effects than similar intervening events occurring in the postnatal period. We have reported previously that early postnatal adoption prevents prenatal stress-induced long-term impairments in glucocorticoid feedback. To characterize further the effects of adoptions during the postnatal period, adoptions have been performed at different times, and the effect on the postnatal ontogeny of the hypothalamo-pituitary-adrenal axis has been investigated. Adoptions were performed during the first hour after birth (A1) and on the fifth (A5) and twelfth (A12) days after birth. At each of these times, other litters (S1, S5, S12) underwent a "separation" controlling for the 1 min maternal separation necessary for the adoptions. Locomotor behavior, cognition, and stress-induced corticosterone secretion in the adult male offspring have been examined, along with maternal behavior. Early adoption (A1) was found to prevent the prolonged stress-induced secretion of corticosterone evident in early separated (S1) offspring. Similarly, A1 rats demonstrated lower novelty-induced locomotion and improved recognition performance in a Y-maze compared to S1 offspring. However, later adoption (A5, A12) prolonged stress-induced corticosterone secretion, increased the locomotor response to novelty, and disrupted cognitive performance in the offspring. Only the early adoption increased maternal licking behavior, a factor that may have a protective effect on the pups. Taken together, these results suggest that the same postnatal manipulation realized at different times can induce different, or even opposite, effects on the behavioral and neuroendocrine characteristics of the adult offspring.

Improving the management of children's pain in A&E

This paper describes a project that sought to improve the management of children's pain in an A&E department. Pain management is not always seen as a priority in A&E departments. The problems are highlighted through two case studies, and guidelines to improve practice were developed in collaboration with a specialist multidisciplinary team.

Lack of effect of cimetidine on lymphocyte subsets in patients infected with human immunodeficiency virus type 1

Cimetidine, widely used for peptic ulcer disease, blocks type 2 histamine receptors present on immune cells, including T cells, B cells, and monocytes. As an earlier published study showed evidence of increases in CD4 cell counts due to this drug, we conducted a randomized, placebo-controlled, 8-week trial of oral cimetidine (400 mg p.o. t.i.d.) in a study involving 182 patients infected with human immunodeficiency virus (HIV). Overall, cimetidine-treated patients had a decline in CD4+ cell counts that was no different from the decline for placebo-treated persons, neither during the first 8 weeks of the trial (mean drop, 7.1% [standard error, 12.1-1.8] vs. 6.7% [standard error, 11.6-1.5]) nor during the subsequent 8 weeks of open-label administration of cimetidine. No differences were evident between the treatment groups in terms of the percentage reactive to p24 antigen at baseline, and p24 antigen concentrations did not change from baseline to the end of week 8. In summary, cimetidine is well tolerated by HIV-infected individuals but alters neither CD4+ cell counts nor at least one quantitative measure of viral load, HIV p24 antigen levels.

Crystal structure of turnip yellow mosaic virus

The structure of turnip yellow mosaic virus (TYMV) has been solved to 3.2 A resolution and an R-value of 18.7%. The structure is consistent with models based on low resolution X-ray and electron microscopy studies, with pentameric and hexameric protein aggregates protruding from the surface and forming deep valleys at the quasi three-fold axes. The N-terminal 26 residues of the A-subunit are disordered, while those of the B- and C-subunits are seen to interact around the interior of the quasi six-fold cluster where they form an annulus. The three histidine residues of each protein subunit are located in the interior and accessible for interaction with the RNA genome. The appearance of the interior surface of the virus capsid, along with buried surface area calculations, suggest that a pentameric unit is lost during decapsidation.

Crystal structure of an anti-anti-idiotype shows it to be self-complementary

The structure of the Fab fragment of the mouse anti-anti-idiotypic monoclonal antibody (mAb) GH1002 was solved by X-ray crystallography. mAb GH1002 was elicited with the syngeneic anti-idiotype mAb MK2-23 which mimics the determinant defined by anti-human high molecular weight-melanoma associated antigen (HMW-MAA) mAb 763.74. The Fab fragments of mAb GH1002 exist in the crystal as dimers related by crystallographic 2-fold axes. The interface between dyad-related Fab fragments is formed primarily by interaction of the hypervariable loops of one with the other. The self-interaction of Fab fragments of anti-anti-idiotypic mAb GH1002 through their combining sites is extremely tight and intricate, closely resembling that observed in structures of id-anti-id complexes, and comparable in terms of total contact area, charge complementarity, and number of hydrogen bonds. The self-complementarity of the antibody observed here could be coincidental and thus reflect some non-specific binding capability. It might, on the other hand, be immunologically relevant and exemplify a certain degree of evolved self complementarity characteristic of antibodies participating in idiotypic cascades.

Implications of the UNNDERPIN study at St George's Hospital, Morpeth, Northumberland

UNNDERPIN (University of Northumbria at Newcastle DEvelopment of and Research into the Provision of Information to Nurses and nurse educators) was an 8-month research project at St George's Hospital, Morpeth, Northumberland. The general aim of the project has been to undertake an examination of library and information services in a climate of change where user information needs are changing and demanding changed services to be provided to meet those needs in order to support patient care and clinical developments. The paper gives an overview of the project describing its background and presenting a summary of the research findings, conclusions and wider implications of the work.

Serotonergic regulation of acetylcholine release in rat frontal cortex

The extent to which serotonin regulates the activity of cortically projecting cholinergic neurons was studied using in vivo microdialysis to monitor interstitial concentrations of acetylcholine in the frontal cortex of freely moving rats. Systemic administration of the serotonin release-inducing agent fenfluramine (3 or 10 mg/kg, i.p.) increased acetylcholine release by 110-130%. The fenfluramine-induced increase in acetylcholine release was significantly attenuated by pretreatment with the selective serotonin uptake inhibitor fluoxetine (10 mg/kg, i.p.). Pretreatment with the selective dopamine D1 receptor antagonist SCH-23390 (0.3 mg/kg, s.c.) failed to prevent the fenfluramine-induced increase in acetylcholine release. In contrast, the serotonin 5-HT2A receptor antagonist ketanserin (5 mg/kg, i.p.) blocked fenfluramine-induced increases in acetylcholine release. In contrast to previous studies that have concluded that serotonin has inhibitory actions on cortical acetylcholine release, the present results indicate that fenfluramine increases cortical acetylcholine release in vivo by its ability to enhance serotonin transmission and that serotonin produces these effects at least in part via actions at serotonin 5-HT2A receptors.