Protein and virus crystal growth on international microgravity laboratory-2

Two T = 1 and one T = 3 plant viruses, along with a protein, were crystallized in microgravity during the International Microgravity Laboratory-2 (IML-2) mission in July of 1994. The method used was liquid-liquid diffusion in the European Space Agency's Advanced Protein Crystallization Facility (APCF). Distinctive alterations in the habits of Turnip Yellow Mosaic Virus (TYMV) crystals and hexagonal canavalin crystals were observed. Crystals of cubic Satellite Tobacco Mosaic Virus (STMV) more than 30 times the volume of crystals grown in the laboratory were produced in microgravity. X-ray diffraction analysis demonstrated that both crystal forms of canavalin and the cubic STMV crystals diffracted to significantly higher resolution and had superior diffraction properties as judged by relative Wilson plots. It is postulated that the establishment of quasi-stable depletion zones around crystals growing in microgravity are responsible for self-regulated and more ordered growth.

Developing an immunisation protocol for the primary health care team

Health visitors based at the Ely Bridge fundholding practice in Cardiff were concerned about the low uptake in child immunisations. The health visitor team describe how they developed a joint immunisation protocol in collaboration with primary health care team colleagues to enable improved uptake in line with the Health of the Nation and GP contract targets.

Preliminary X-ray diffraction analysis of crystals of tomato aspermy virus (TAV)

Tomato aspermy virus (TAV) is a member of the T = 3 cucumovirus group, and the chrysanthemum strain (C-TAV) has been crystallized in a form suitable for X-ray structural analysis. The crystals, which grow in 14-17% ethanol at pH 8.5, are of orthorhombic space group I222 with unit cell dimensions of a = 295.1 A, b = 320.5 A, and c = 383.6 A. There are two T = 3 virus particles in the unit cell, which means that they must be centered at 0,0,0 and 1/2, 1/2, 1/2 with icosahedral 222 symmetry elements coincident with crystallographic symmetry operators. The asymmetric unit of the crystals, therefore, contains one quarter of a virus particle, or 45 capsid subunits. Native diffraction data to 4 A resolution have been collected using synchrotron radiation, though data appear to be present beyond that resolution.

Structure of an anti-idiotypic Fab against feline peritonitis virus-neutralizing antibody and a comparison with the complexed Fab

The crystal structure of anti-idiotopic Fab 409.5.3, made against an E2 specific feline infectious peritonitis virus-neutralizing antibody 730.1.4, has been determined in its free from, at 2.9 A resolution by molecular replacement. This antibody, used as an immmunogen, elicits the production of anti-anti-idiotypic antibodies that in turn neutralize the virus. The structure of the uncomplexed Fab was refined using constrained-restrained least squares minimization and simulated annealing in combination with conjugate gradient techniques to a crystallographic R of 0.22 based on 16,482 unique reflections between 20.0 and 2.9 A. The free antiidiotypic Fab shows, when compared to its complexed form, a 5 degrees rotation of its variable light with respect to its variable heavy domain and rearrangement of complementarity determining region loops, which permits optimization of the stereocomplementarity between interacting molecules. This finding supports the induced fit hypothesis for antibody antigen interaction.

Preliminary X-ray diffraction analysis of crystals of turnip yellow mosaic virus (TYMV)

Turnip yellow mosaic virus (TYMV) was purified from Chinese cabbage and crystallized in a form that permits high resolution structural analysis using X-ray diffraction. The crystals have a hexagonal bipyramidal morphology and often achieve dimensions of 1.0 x 1.0 x 0.5 mm. The crystals appear to be of hexagonal space group P6(2)22 with a=b=525 A, c=315 A, but we cannot strictly rule out the possibility that the space group is P622. They appear different than any crystals of TYMV previously reported. There are three T = 3 virus particles in the unit cell, which implies that one quarter of the particle, or 45 protein subunits, comprises the asymmetric unit of the crystal. Native data have been collected using synchrotron radiation to a resolution of 3.2 A.

Effects of breathing a normoxic helium mixture on exercise tolerance of patients with cystic fibrosis

Breathing helium-oxygen (He-O2) mixtures of 20.9% O2/79.1% He has been shown to increase exercise ventilation and peak oxygen uptake in healthy subjects. The improved exercise performance is thought to be due to the reduced density of He-O2 compared to air and the resulting increases in ventilation. Patients with cystic fibrosis (CF) frequently have abnormal pulmonary function test results, low exercise ventilations and diminished exercise tolerance. This led to the hypothesis that in CF the exercise tolerance of patients might improve when breathing He-O2. To test this hypothesis, 11 patients with CF or mild to severe airway obstruction performed spirometry and progressive maximal exercise tests while breathing air or He-O2. The He-O2 mixture significantly increased (P < 0.05) forced expiratory volume in 1 sec (FEV1) by 8.2%, peak expired flow by 39%, and maximal voluntary ventilation (MVV) by 17.9% compared to air, while forced vital capacity (FVC) and forced mid-expiratory flow rate (FEF25-75%) were unchanged by breathing He-O2. Ventilation and oxygen uptake at matched submaximal power outputs were not increased while breathing He-O2, nor were peak exercise ventilation (VEpeak) or peak exercise oxygen uptake (VO2peak). Estimated hemoglobin saturation and total exercise time were also unchanged during He-O2 breathing. However, there was a trend for the subjects with the better FEV1 to increase VO2peak. Increases in VO2peak when breathing He-O2 and air were correlated (r = 0.67, P < 0.05) with the percent of predicted FEV1 values. Still, in the 11 patients as a group, breathing He-O2 did not significantly improve VO2peak, VEpeak, or exercise tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)

State-dependent release of acetylcholine in rat thalamus measured by in vivo microdialysis

Mesopontine cholinergic neurons have long been thought to play a key role in behavioral state control. In particular, they have been implicated in the process of EEG desynchrony and in the generation of rapid eye movement (REM) sleep. However, the behavioral profile of identified mesopontine cholinergic neurons has not been unequivocally demonstrated. In an attempt to address this issue, in vivo microdialysis was used to monitor acetylcholine (ACh) release across behavioral state in the rat thalamus, a major projection site of mesopontine cholinergic neurons. Because REM periods in rats are of short duration, a method was developed to collect and accumulate sufficiently large samples from each of the individual states of wake, slow-wave sleep, and REM sleep to permit off-line analysis via (HPLC-ECD). Probe placement and the source of cholinergic innervation to the vicinity of the microdialysis probe were verified using retrograde tracing combined with ChAT immunohistochemistry. Finally, the sodium and calcium dependence of ACh measured in the thalamus were tested using TTX and calcium-free dialysates. The results showed that (1) extracellular ACh concentrations in the thalamus are high during both wake and REM sleep and significantly lower during slow-wave sleep, (2) the majority of cholinergic projections to the vicinity of the dialysis probes originate in the mesopontine tegmentum, and (3) ACh release in the thalamus is due to sodium- and calcium-dependent mechanisms. In contrast to predictions of some previous hypotheses, these results demonstrate that mesopontine cholinergic neurons are active during both wake and REM sleep.

Giant infectious intracavernous carotid artery aneurysm presenting as intractable epistaxis

Infectious intracavernous carotid artery aneurysms usually present with ophthalmoplegia and/or signs of cavernous sinus thrombosis. We report an unusual case in which a patient with AIDS presented with intractable epistaxis secondary to rupture of a giant infectious intracavernous carotid artery aneurysm. Culture of the aneurysm grew mycobacterium avium intracellulare (MAI). The patient was treated successfully by excision of the aneurysm and reconstruction of the internal carotid artery with a saphenous vein interposition graft.

Characterization of crystals of satellite panicum mosaic virus

Satellite panicum mosaic virus (SPMV) has been purified from pearl millet and obtained in a variety of different crystal forms, at least two of which appear suitable for high resolution X-ray diffraction analysis. The first is of cubic space group P4(2)32 with a = b = c = 183.1 A and two virus particles in the unit cell. The second is of a primitive orthorhombic space group with a = 166.1 A, b = 266.7 A and c = 269.1 A, with four virus particles in the unit cell. While the cubic crystal has as its asymmetric unit one twelfth of the icosahedron, or five capsid protein subunits, the asymmetric unit of the orthorhombic crystals is an entire particle. The cubic crystals diffract to at least 2.8 A resolution. We have also succeeded in crystallizing, but not yet characterizing the master virus, PMV.

Screening for non-insulin-dependent diabetes mellitus (NIDDM): how often should it be performed?

OBJECTIVES

To examine whether a screening programme for diabetes repeated after an interval of 30 months is worthwhile both in terms of yield of new cases and continued high response rate.

METHODS

Self testing for postprandial glycosuria was used as it has been shown to have a good response rate, a good yield of cases of diabetes, and a sensitivity and specificity which compares favourably with more expensive and invasive screening methods. A total of 3231 subjects aged 45-70 years in one practice were screened on two occasions 30 months apart. Eighty seven subjects known to have diabetes were excluded. This number included five new patients who had presented since the initial screen; two of whom had moved into the practice, one who screened positive at the initial screen but failed to attend for the oral glucose tolerance test (OGTT), and two subjects who had screened negative, the first presenting 24 months after screening.

RESULTS

At repeat screening the return rate was lower than at the first screening (72.5% v 79.2%, P < 0.0001). Glycosuria was detected in 52 subjects (2.3%), at the repeat screening, similar to that at the initial screen. Attendance for the OGTT after a positive screening test was 93.2%. Only six subjects of the 24 with glycosuria but normal glucose tolerance at initial screen were found to have glycosuria again; repeat OGTTs were all normal. Of the remaining 46 subjects, 10 had non-insulin-dependent diabetes mellitus (NIDDM) and five impaired glucose tolerance (IGT). The number of subjects with diabetes was not significantly different from that at the initial screening (0.44% v 0.72%, P = 0.2).

CONCLUSIONS

Repeat screening after 30 months has a high response rate, similar rate of detection of glycosuria, and a further yield of 0.44% of newly diagnosed cases of diabetes. A screening programme detecting postprandial glycosuria identifies additional diabetic subjects 30 months after a previous screening programme.

Crystal structure of an idiotype-anti-idiotype Fab complex

Anti-idiotypic monoclonal antibody 409.5.3 is raised against an antibody that neutralizes feline infectious peritonitis virus. This antibody, used as an immunogen, elicits the production of anti-anti-idiotypic antibodies that in turn neutralize the virus. The crystal structure of the complex between anti-idiotypic Fab 409.5.3 and idiotypic Fab fragment of virus-neutralizing antibody has been solved by molecular replacement using real-space Patterson search and filtering by Patterson correlation-coefficient refinement. The structure has been refined to an R value of 0.21 based on 21,310 unique reflections between 40.0 and 2.9 A. The three-dimensional structure reveals extensive, specific interactions that involve 118 van der Waals contacts and at least 9 probable hydrogen bonds. The two Fabs are rotated 61 degrees with respect to each other around the approximate long axis of the complex and are within 26 degrees being aligned along their major axes.

Refined molecular structure of pig pancreatic alpha-amylase at 2.1 A resolution

The structure of pig pancreatic alpha-amylase has been determined by X-ray diffraction analysis using multiple isomorphous replacement in a crystal of space group P2(1)2(1)2(1) (a = 70.6 A, b = 114.8 A, c = 118.8 A) containing nearly 75% solvent. The structure was refined by simulated annealing and Powell minimization, as monitored by 2Fo-Fc difference Fourier syntheses, to a conventional R of 0.168 at 2.1 A resolution. The final model consists of all 496 amino acid residues, a chloride and a calcium ion, 145 water molecules and an endogenous disaccharide molecule that contiguously links protein molecules related by the 2(1) crystallographic operator along x. The protein is composed of a large domain (amino acid residues 1 to 403) featuring a central alpha ta-barrel of eight parallel strands and connecting helices with a prominent excursion between strand beta 3 and helix alpha 3 (amino acid residues 100 to 168). The final 93 amino acid residues at the carboxyl terminus form a second small domain consisting of a compact Greek key beta-barrel. The domains are tightly associated through hydrophobic interfaces. The beta 3/alpha 3 excursion and portions of the central alpha/beta-barrel provide four protein ligands to the tightly bound Ca ion; three water molecules complete the coordination. The Cl- ion is bound within one end of the alpha/beta-barrel by two arginine residues in a manner suggesting a plausible mechanism for its allosteric activation of the enzyme. A crystalline complex of the pancreatic alpha-amylase with alpha-cyclodextrin, a cyclic substrate analog of six glucose residues, reveals, in difference Fourier maps, three unique binding sites. One of the alpha-cyclodextrin sites is near the center of the long polysaccharide binding cleft that traverses one end of the alpha/beta-barrel, another is at the extreme of this cleft. By symmetry this can also be considered as two half sites located at the extremes of the active site cleft. This latter alpha-cyclodextrin displaces the endogenous disaccharide when it binds and, along with the first sugar ring, delineates the extended starch binding site. The third alpha-cyclodextrin binds at an "accessory site" near the edge of the protein and is quite distant from the polysaccharide binding cleft. Its presence explains the multivalency of alpha-amylase binding to dextrins in solution. The extended active site cleft is formed by large, sweeping, connecting loops at one end of the alpha/beta-barrel. These include three sequence segments that are highly conserved among alpha-amylases.(ABSTRACT TRUNCATED AT 400 WORDS)

Preliminary crystallographic study of a complex between an Fab of a monoclonal feline peritonitis virus neutralizing antibody and its anti-idiotypic Fab

A complex between an Fab fragment of an E2 specific feline infectious peritonitis virus neutralizing antibody 730.1.4 and Fab fragment from anti-idiotypic monoclonal antibody 409.5.3, was crystallized from ammonium sulfate using vapor diffusion methods. The complex crystals diffract to about 2.9 A resolution and are of orthorhombic space group P2(1)22(1) with a = 75.2 A, b = 80.6 A and c = 187.6 A. There are two Fab molecules, or one idiotype-anti-idiotype complex, comprising the asymmetric unit. The long 187.6 A c axis suggests that the long axis of the complex might lie along this direction. Although small and radiation-sensitive, crystals are suitable for three-dimensional structural analysis.

Evaluation of fluticasone propionate (500 micrograms day-1) administered either as dry powder via a Diskhaler inhaler or pressurized inhaler and compared with beclomethasone dipropionate (1000 micrograms day-1) administered by pressurized inhaler

Five hundred and eighty-five patients with moderate asthma, currently receiving 400-1000 micrograms day-1 of an inhaled corticosteroid, were treated for 6 weeks in a double-blind, randomized, parallel group study with either 500 micrograms day-1 fluticasone propionate as a dry powder via a Diskhaler inhaler, 500 micrograms day-1 fluticasone propionate via a pressurized inhaler or 1000 micrograms day-1 beclomethasone dipropionate via a pressurized inhaler. For all three treatment groups, mean morning and evening peak expiratory flow rates (PEFRs) increased within 1 week of the start of treatment. There were also improvements in clinic lung function, daytime and night-time asthma symptoms and a reduction in daytime and night-time rescue bronchodilator medication in all three groups. There were no statistically significant differences between the two formulations of fluticasone propionate in any of the efficacy parameters. Fluticasone propionate via the Diskhaler was significantly more effective than beclomethasone dipropionate over the 6 week study period in reducing diurnal variation (mean difference--4 l min-1, 95% CI--8 to 0 l min-1: P = 0.03). Fluticasone propionate via the Diskhaler produced a statistically significant improvement in night-time symptoms when compared to beclomethasone dipropionate whereas, beclomethasone dipropionate 1000 micrograms day-1 was statistically significantly more effective than both formulations of fluticasone propionate in improving daytime symptoms (P < 0.05). However, these statistical differences must be viewed together with the fact that very few patients recorded a score of 2 or more for both daytime or night-time symptoms. There was a similarly low incidence of adverse events with all three treatments with no evidence of hypothalamic pituitary adrenal (HPA)-axis suppression. The results of the 6-week comparative study showed that 500 micrograms day-1 fluticasone propionate whether administered via pressurized inhaler or Diskhaler is as effective and as safe as 1000 micrograms day-1 beclomethasone dipropionate administered via a pressurized inhaler in the treatment of moderate asthma. Over 12 months fluticasone propionate 500 micrograms day-1 via a pressurized inhaler was at least as effective and as well tolerated as beclomethasone dipropionate 1000 micrograms day-1.

Determination of three crystal structures of canavalin by molecular replacement

Canavalin, the major reserve protein of the jack bean, was obtained in four different crystal forms. From the structure determined by multiple isomorphous replacement in a hexagonal unit cell, the structures of three other crystals were determined by molecular replacement. In two cases, the rhombohedral and cubic crystals, placement was facilitated by coincidence of threefold molecular symmetry with crystallographic operators. In the orthorhombic crystal the canavalin trimer was the asymmetric unit. The rhombohedral, orthorhombic and cubic crystal structures were subsequently refined using a combination of several approaches with resulting R factors of 0.194, 0.185 and 0.211 at resolutions of 2.6, 2.6 and 2.3 A, respectively. Variation in the conformation of the molecule from crystal to crystal was small with an r.m.s. deviation in Calpha positions of 0.89 A. Packing is quite different among crystal forms but lattice interactions appear to play little role in the conformation of the molecule. Greatest variations in mean position are for those residues that also exhibit the greatest thermal motion. Crystal contacts in all crystals are mediated almost exclusively by hydrophilic side chains, and three to six intermolecular salt bridges per protein subunit are present in each case.

Dopaminergic regulation of cortical acetylcholine release: effects of dopamine receptor agonists

The regulation of the basal forebrain cholinergic system by D1 and D2 dopamine receptors was assessed in the rat using in vivo microdialysis of cortical acetylcholine. The D1 agonist CY 208-243 significantly increased cortical acetylcholine release; in contrast, the D2 agonists quinpirole and (+)-4-propyl-9-hydroxynaphthoxazine were without significant effects. Moreover, when administered in combination with CY 208-243, quinpirole failed to potentiate the D1 agonist-induced increases in cortical acetylcholine release. The non-selective dopamine receptor agonist apomorphine also increased cortical acetylcholine release, and this was completely blocked by the selective D1 receptor antagonist SCH 23390 and slightly, but not significantly attenuated by the D2 antagonist raclopride. The present results indicate that stimulation of D1 receptors activates cortically-projecting cholinergic neurons; however, a minor contribution of D2 receptors cannot be excluded.

Three-dimensional structure of satellite tobacco mosaic virus at 2.9 A resolution

The crystal structure of satellite tobacco mosaic virus (STMV) has been solved by a combination of multiple isomorphous replacement and molecular replacement methods and refined at 2.9 A resolution to a conventional R-factor of 0.215. STMV, a T = 1 icosahedral virus, is the smallest whose structure has been determined. The coat protein is an eight-stranded "Swiss roll" beta-barrel with an amino-terminal strand that extends away from the beta-barrel by more than 60 A. This strand is primarily responsible for quaternary interactions within the capsid. The most arresting feature of the virus structure is the intimate association of each capsid protein dimer with a Watson-Crick base-paired segment of RNA double helix on the interior of the virion. The icosahedral 2-fold axis of each dimer pair is coincident with that of the central base-pair of each helical RNA segment whose helical axis is along the edge of the icosahedron. The helical RNA segments are seven base-pairs in length with a stacked base at each 3' end so that a total of 16 nucleotides is clearly visible. The character of the RNA helix is somewhat different than any of the canonical forms. Assuming full occupancy, then approximately 45% of the total RNA genome is present in the electron density map. The close association of capsid with highly structured nucleic acid suggests that assembly of STMV is likely to be a highly co-operative process involving both protein and RNA. The nucleic acid is distributed within the virion with a high degree of order. The capsid protein is a true double helical RNA binding protein and a number of prominent interactions between protein and RNA can be clearly seen.

Double-helical RNA in satellite tobacco mosaic virus

Satellite tobacco mosaic virus (STMV) is the spherical satellite to an obligatory rod-shaped helper tobacco mosaic virus (TMV), which is required for replication. STMV has 60 protein subunits of M(r) 17,500 on a T = 1 icosahedral capsid containing a single-stranded RNA genome of 1,059 bases. STMV appears similar to another virus, STNV, but is approximately 20 per cent smaller. It shows no amino-acid homology or immunological cross-reactivity with either STNV or its host TMV. Here we report the X-ray crystal structure of STMV, which shows that the coat protein of STMV contains a 'Swiss roll' beta-barrel. An amino-terminal strand extends more than 60A and is primarily responsible for quaternary interactions. Each capsid dimer is associated with a segment of genomic RNA double helix comprising seven base pairs. The dyad of each protein dimer is coincident with that of the central base pair of the associated RNA segment whose helix axis is directed along an icosahedral edge. Protein-nucleic acid interactions are extensive. The RNA helices, which have additional stacked bases at their 3' termini, differ significantly from canonical nucleic acid helical forms.

Dopaminergic regulation of cortical acetylcholine release

The extent to which the activity of basal forebrain cholinergic neurons is influenced by dopamine (DA) was investigated using in vivo microdialysis of cortical acetylcholine (ACh). Systemic administration of the DA receptor agonist apomorphine significantly increased dialysate concentrations of ACh. Systemic, but not local, administration of d-amphetamine produced similar effects. Both D1 (SCH 23390) and D2 (haloperidol, raclopride) DA receptor antagonists attenuated the amphetamine-induced increase in cortical ACh release; however, only the D1 antagonist significantly reduced basal output of cortical ACh. These findings suggest that the activity of cortically projecting cholinergic neurons in the nucleus basalis is regulated in an excitatory manner by central dopaminergic neurons and that both D1 and D2 receptors are involved.

The three-dimensional structure of an intact monoclonal antibody for canine lymphoma

Crystal structures of Fab antibody fragments determined by X-ray diffraction characteristically feature four-domain, beta-barrel arrangements. A human antibody Fc fragment has also been found to have four beta-barrel domains. The structures of a few intact antibodies have been solved: in two myeloma proteins, the flexible hinge regions that connect the Fc to the Fab segments were deleted so the molecules were non-functional, structurally restrained, T-shaped antibodies; a third antibody, Kol, had no hinge residues missing but the Fc region was sufficiently disordered that it was not possible to relate its disposition accurately with respect to the Fab components. Here we report the structure at 3.5 A resolution of an IgG2a antitumour monoclonal antibody which contains an intact hinge region and was solved in a triclinic crystal by molecular replacement using known Fc and Fab fragments. The antibody is asymmetric, reflecting its dynamic character. There are two local, apparently independent, dyads in the molecule. One relates the heavy chains in the Fc, the other relates the constant domains of the Fabs. The variable domains are not related by this 2-fold axis because of the different Fab elbow angles of 159 degrees and 143 degrees. The Fc has assumed an asymmetric, oblique orientation with respect to loosely tethered yet almost collinear Fabs. Our study enables the two antigen-binding segments as well as the Fc portion of a functional molecule to be visualized and illustrates the flexibility of these immune response proteins.

Regional brain blood flow during prolonged submaximal exercise in ponies

Experiments were carried out on 8 healthy ponies to examine the effects of prolonged submaximal exercise on regional distribution of brain blood flow. Brain blood flow was ascertained by use of 15-microns-diameter radionuclide-labeled microspheres injected into the left ventricle. The reference blood was withdrawn from the thoracic aorta at a constant rate of 21.0 ml/min. Hemodynamic data were obtained with the ponies at rest (control), and at 5, 15, and 26 minutes of exercise performed at a speed setting of 13 mph on a treadmill with a fixed incline of 7%. Exercise lasted for 30 minutes and was carried out at an ambient temperature of 20 C. Heart rate, mean arterial pressure, and core temperature increased significantly with exercise. With the ponies at rest, a marked heterogeneity of perfusion was observed within the brain; the cerebral, as well as cerebellar gray matter, had greater blood flow than in the respective white matter, and a gradually decreasing gradient of blood flow existed from thalamus-hypothalamus to medulla. This pattern of perfusion heterogeneity was preserved during exercise. Regional brain blood flow at 5 and 15 minutes of exercise remained similar to resting values. However, at 26 minutes of exercise, vasoconstriction resulted in a significant reduction in blood flow to all cerebral and brain-stem regions. In the cerebellum, the gray matter blood flow and vascular resistance remained near control values even at 26 minutes of exercise. Vasoconstriction in various regions of the cerebrum and brainstem at 26 minutes of exertion may have occurred in response to exercise-induced hypocapnia, arterial hypertension, and/or sympathetic neural activation.

Macromolecular crystal growth experiments on International Microgravity Laboratory--1

Macromolecular crystal growth experiments, using satellite tobacco mosaic virus (STMV) and canavalin from jack beans as samples, were conducted on a US Space Shuttle mission designated International Microgravity Laboratory--1 (IML-1), flown January 22-29, 1992. Parallel experiments using identical samples were carried out in both a vapor diffusion-based device (PCG) and a liquid-liquid diffusion-based instrument (CRYOSTAT). The experiments in each device were run at 20-22 degrees C and at colder temperatures. Crystals were grown in virtually every trial, but the characteristics of the crystals were highly dependent on the crystallization technique employed and the temperature experience of the sample. In general, very good results, based on visual inspection of the crystals, were obtained in both PCG and CRYOSTAT. Unusually impressive results were, however, achieved for STMV in the CRYOSTAT instrument. STMV crystals grown in microgravity by liquid-liquid diffusion were more than 10-fold greater in total volume than any STMV crystals previously grown in the laboratory. X-ray diffraction data collected from eight STMV crystals grown in CRYOSTAT demonstrated a substantial improvement in diffraction quality over the entire resolution range when compared to data from crystals grown on Earth. In addition, the extent of the diffraction pattern for the STMV crystals grown in space extended to 1.8 A resolution, whereas the best crystals that were ever grown under conditions of Earth's gravity produced data limited to 2.3 A resolution. Other observations indicate that the growth of macromolecular crystals is indeed influenced by the presence or absence of gravity. These observations further suggest, consistent with earlier results, that the elimination of gravity provides a more favorable environment for such processes.

Spo0A activates and represses its own synthesis by binding at its dual promoters

The Spo0A protein of Bacillus subtilis controls the onset of sporulation by regulating transcription of various genes in both positive and negative manners depending on the promoters affected. The expression of the spo0A gene occurs from two promoters (Pv,Ps), separated by 148 bp, and transcription switches from Pv to Ps early in the sporulation program. DNase I footprint analysis of the spo0A promoter region revealed three distinct sites of Spo0A binding: -4 to +19 relative to Pv, -17 to +1 relative to Ps, and a region between Pv and Ps. The Pv region and the region between the two promoters was sufficient for repression of Pv. Induction of Ps also required these regions which are upstream of -52 relative to Ps. Mutant Spo0A proteins containing asp----asn mutations at asp10 and asp56 were inactive in repression of the abrB promoter in vivo yet still retained DNA-binding activity. The results presented are consistent with a model in which the phosphorylated form of Spo0A acts directly at its promoters to achieve induction of Ps and repression of Pv. These effects at the spo0A promoter were independent of the presence of the major kinase, KinA.

Bronchial circulation during prolonged exercise in ponies

Tracheal, bronchial, and renal flow were studied in 8 healthy ponies at rest and during exercise performed on a treadmill at a speed setting of 20.8 km/h and 7% grade (incline) for 30 minutes. Blood flow was determined with 15-microns-diameter radionuclide-labeled microspheres that were injected into the left ventricle when the ponies were at rest, and at 5, 15, and 26 minutes of exertion. Heart rate and mean aortic pressure increased from resting values (40 +/- 2 beats/min and 124 +/- 3 mm of Hg, respectively) to 152 +/- 8 beats/min and 133 +/- 4 mm of Hg at 5 minutes of exercise, to 169 +/- 6 beats/min and 143 +/- 5 mm of Hg at 15 minutes of exercise, and to 186 +/- 8 beats/min, and 150 +/- 5 mm of Hg at 26 minutes of exercise. Tracheal blood flow at rest and during exercise remained significantly (P less than 0.05) less than bronchial blood flow. Tracheal blood flow increased only slightly with exercise. Vasodilation caused bronchial blood flow to increase throughout exercise. Pulmonary arterial blood temperature of ponies also increased significantly (P less than 0.05) with exercise and a significant (P less than 0.005) correlation was found between bronchial blood flow and pulmonary arterial blood temperature during exertion. At 5 minutes of exercise, renal blood flow was unchanged from the resting value; however, renal vasoconstriction was observed at 15 and 26 minutes of exercise. We concluded that bronchial circulation of ponies increased with exercise in close association with a rise in pulmonary arterial blood temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Respiratory muscle perfusion in ponies during prolonged submaximal exercise in thermoneutral environment

Distribution of blood flow among various respiratory muscles was examined in 8 healthy ponies during submaximal exercise lasting 30 minutes, using radionuclide labeled 15-microns diameter microspheres injected into the left ventricle. From the resting values (40 +/- 2 beats/min; 37.3 +/- 0.2 C), heart rate and pulmonary arterial blood temperature increased significantly at 5 (152 +/- 8 beats/min; 38.6 +/- 0.2 C), 15 (169 +/- 6 beats/min; 39.8 +/- 0.2 C), and 26 (186 +/- 8 beats/min; 40.8 +/- 0.2 C) minutes of exertion, and the ponies sweated profusely. Mean aortic pressure also increased progressively as exercise duration increased. Blood flow increased significantly with exercise in all respiratory muscles. Among inspiratory muscles, perfusion was greatest in the diaphragm and ventral serratus, compared with external intercostal, dorsal serratus, and scalenus muscles. Among expiratory muscles, blood flow in the internal abdominal oblique muscle was greatest, followed by that in internal intercostal and transverse thoracic muscles, in which the flow values remained similar. The remaining 3 abdominal muscles had similar blood flow, but these values were less than that in the internal intercostal, transverse thoracic, and internal abdominal oblique muscles. Blood flow values for all inspiratory and expiratory muscles remained similar for the 5 and 15 minutes of exertion. However, at 26 minutes, blood flow had increased further in the diaphragm, external intercostal, internal intercostal, transverse thoracic, and the external abdominal oblique muscle as vascular resistance decreased. On the basis of our findings, all respiratory muscles were activated during submaximal exercise and their perfusion had marked heterogeneity.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystallization and preliminary X-ray analysis of human endothelin

Endothelin, a potent regulator of vasoconstriction and hypertension, is a naturally produced peptide of 21 amino acids containing two disulfide bonds. We have crystallized endothelin from humans using the vapor-diffusion technique, characterized the crystals by X-ray diffraction analysis, and have collected the X-ray intensities to a resolution of 1.8 A. The crystals, which demonstrate physical properties similar to most protein crystals and have a comparable solvent content, are hexagonal prisms that frequently grow to lengths of 400 microns and widths of 150 microns. The space group of the crystals is P6(1)22 (or P6(5)22), with a = 27.4, c = 79.6 A. There is one molecule of endothelin in the asymmetric unit of the crystals.

Preliminary crystallographic study of peanut peroxidase

The cationic isozyme of peroxidase isolated from suspension cultures of peanut cells is a heme-containing and calcium-dependent glycoprotein having four covalently attached oligosaccharide chains. Attempts were made to crystallize the glycoprotein for X-ray diffraction analysis, and these have met with some success. Crystals have now been grown that are suitable for a full three-dimensional structural analysis. The crystals are thin plates and we have shown them to be of the orthorhombic space group P2(1)2(1)2(1) with a = 48.1, b = 97.2, c = 146.2 A. The crystals diffract to beyond 2.8 A resolution, appear to be stable to lengthy X-ray exposure, and contain two molecules of 40,000 daltons each in the asymmetric unit.

Characterization of crystals of an Fab fragment of a murine monoclonal antibody

The Fab fragment of an antibody, made against an E2-specific feline infectious peritonitis virus neutralizing antibody, has been crystallized in a form suitable for X-ray diffraction analysis from PEG 4000 using vapor diffusion methods. The Fab fragment crystals diffract to about 2.9 A resolution and are of triclinic space group P1. Unit cell dimensions, by which the reciprocal lattice can be indexed, are a = 57.16 A, b = 70.85 A, c = 75.81 A, alpha = 85.11 degrees, beta = 121.28 degrees and gamma = 116.33 degrees. There are two Fab fragments comprising the asymmetric unit of the crystals. The presence of a pseudo-mirror plane in the diffraction pattern suggests the presence of at least an approximate dyad axis relating the two Fab fragments within the asymmetric unit.

Characterization of two crystal forms of cytochrome c from Valida membranaefaciens

Two different crystal forms of cytochrome c from the yeast Valida membranaefaciens have been grown by vapor diffusion from polyethylene glycol 4000. Both have been characterized by X-ray diffraction. The first crystal form was grown at 277 K but proved unstable and dissolved when the temperature was increased above 288 K. This crystal was of triclinic space group P1 and had unit-cell dimensions of a = 68.4, b = 35.7, c = 33.24 A, alpha = 116.9, beta = 114.9, gamma = 75.0 degrees. Following dissolution of the triclinic crystals, the second crystal form also grew at 277 K but remained stable even at room temperature. It was of orthorhombic space group P2(1)2(1)2(1) with cell dimensions a = 27.95, b = 63.68, and c = 64.28 A. Although rather small in size, both crystal forms diffracted X-rays well and the resolution of the patterns extended beyond 3 A.

Characterization of crystals of an intact monoclonal antibody for canine lymphoma

A monoclonal antibody of the subclass IgG2a specific for canine lymphoma cells has been crystallized by vapor diffusion from polyethylene glycol 8000. the crystals, which occasionally measure nearly a millimeter on edge, have been examined by X-ray diffraction. The crystals are of triclinic space group P1 with unit cell parameters of a = 66.39 A, b = 77.34 A, c = 101.42 A, alpha = 87.60 degrees, beta = 92.55 degrees, gamma = 97.54 degrees and cell volume of V = 4.84 x 10(5) A3. There is one entire antibody molecule as the asymmetric unit of the crystals. Three-dimensional X-ray diffraction data have been collected to 2.8 A resolution and a self rotation function calculation shows a pronounced peak indicating at least an approximate non-crystallographic dyad axis.

Preliminary investigation of crystals of the neutral lipase from Pseudomonas fluorescens

The neutral lipase from the bacteria Pseudomonas fluorescens, marketed under the trade name LpL-200S, has been crystallized in a form suitable for X-ray diffraction analysis from 35% n-propanol at pH 8.5. The crystals are monoclinic prisms and are of space group C2 with a = 91.00 A, b = 47.17 A, c = 35.21 A and beta = 121.43 degrees. There is one molecule of the protein as the asymmetric unit of the crystals. The diffraction pattern extends to at least 1.6 A resolution and the crystals are extremely robust in terms of X-ray exposure.

Self testing for diabetes mellitus

OBJECTIVE

To develop a simple, economically viable, and effective means of population screening for diabetes mellitus.

DESIGN

A postal request system for self testing for glycosuria with foil wrapped dipsticks. Preprandial and postprandial tests were compared with a single postprandial test. The subjects were instructed how to test, and a result card was supplied on which to record and return the result. All those recording a positive test result and 50 people recording a negative result were invited for an oral glucose tolerance test.

SETTING

General practice in east Suffolk, list size 11534.

PATIENTS

All subjects aged 45-70 years registered with the practice were identified by Suffolk Family Health Services Authority (n = 3057). The 73 subjects known to have diabetes from the practice's register were excluded, leaving 2984 subjects, 2363 (79.2%) of whom responded. 1167 subjects completed the single test and 1196 the two tests.

MAIN OUTCOME MEASURES

Response rate and number of patients with glycosuria. Sensitivity, specificity, and positive predictive value of a single postprandial test and preprandial and postprandial tests. Number of new cases of diabetes identified and cost of screening.

RESULTS

Of the patients completing the single postprandial test, 29 had a positive result, an oral glucose tolerance test showed that eight (28%) had diabetes, six (21%) impaired glucose tolerance, and 14 (48%) normal glucose tolerance. 44 of the group who tested before and after eating had a positive result; nine (20%) had diabetes, five (11%) impaired tolerance, and 26 (11%) normal tolerance. Screening cost 59p per subject and 81 pounds per case detected. Of the 17 people with previously undiagnosed diabetes, eight were asymptomatic and 11 had not visited their general practitioner in the past three months.

CONCLUSIONS

A postal request system for self testing for postprandial glycosuria in people aged 45-70 is a simple and effective method of population screening for diabetes mellitus.

Synergy between preactivated photofrin-II and tamoxifen in killing retrofibroma, pseudomyxoma and breast cancer cells

Exposure of photoactive compounds to light prior to their use in biological systems (preactivation) results in the generation of tumour cell specific metastable cytotoxic species that are no longer dependent on the light energy. Thus, preactivation renders the photoactive compounds suitable for systemic use. We have examined the in vitro effect of preactivated photofrin-II and tamoxifen in retroperitoneal fibroma, pseudomyxoma and male breast carcinoma cell lines. These cells were found to be non-responsive to tamoxifen and were negative for oestrogen receptors. Incubation of these cells with 0.5 microgram/ml preactivated photofrin-II and tamoxifen (less than 10(-6) mol/l) resulted in a significantly enhanced (P less than 0.001) inhibition of DNA synthesis compared with either agent alone. This synergistic effect between tamoxifen and preactivated photofrin-II was determined by multiple drug effect analysis. Treatment of cells with preactivated photofrin-II did not cause the increased expression of oestrogen receptors. These observations suggest that a combination of antihormonal drugs with preactivated compounds may be of clinical value.

Update on preparations

While I found your article Blood and Body Fluid Preparations (Nursing Standard March 13) very interesting and informative, I should like to point out I that it contains information which is out of date.

Cholinergic activity in the rat hippocampus, cortex and striatum correlates with locomotor activity: an in vivo microdialysis study

The possible relationship between behavioral arousal and acetylcholine release in the striatum, hippocampus and frontal cortex was investigated in rats. In vivo microdialysate concentrations of acetylcholine and choline from these brain structures, and photocell beam interruptions (as a measure of behavioral arousal), were measured simultaneously under three conditions: after injections of 1) vehicle or 2) scopolamine (0.4 mg/kg), and 3) before and after the beginning of the rats' night cycle. Dialysate concentrations of ACh in all 3 brain structures and locomotor activity were increased after scopolamine and the onset of the lights out condition. Vehicle injections transiently increased ACh in the hippocampus and cortex and caused short-lasting increases in locomotor activity. Under all conditions, the release of ACh from each of the 3 brain structures correlated with the level of locomotor activity.

Structural alterations in the Bacillus subtilis Spo0A regulatory protein which suppress mutations at several spo0 loci

Secondary site mutations that restore sporulation to sporulation-defective spo0F or spo0B deletion mutants were found to reside in the spo0A gene. Sequence analysis of 23 such sof mutants showed that the sof mutations fell into six classes of missense codon changes, primarily in the conserved amino-terminal domain of the response regulator Spo0A protein. Changes were observed in codons 12, 14, 60, 92, and 121. The residues affected were predominantly located in the potential turn regions at one end of the amino-terminal conserved domain on the same topological face as the active site aspartate residues. The ability of sof mutations to suppress deficiencies in the transmitter kinases, KinA and KinB, of two-component regulatory systems was tested. All of the sof mutations suppressed the sporulation deficiency of kinA mutants but only two classes among five tested suppressed kinB mutations. sof mutants segregated Spo- colonies at high frequency. Five of these Spo- mutants were found to result from mutations in the spo0A locus that reversed the effect of the sof mutatation. One of these was sequenced and found to have the original sof mutation and a new mutation, sos, at codon 105. The accumulation of sos mutations in sof strains suggested that the sof mutations have a subtle, yet deleterious, effect on the growth of the cell. The results suggested that the sof mutations increase the avidity for or reactivity with transmitter kinases in an allele-specific manner, although in some cases it is possible that the sof mutations obviate the need for phosphorylation to activate the Spo0A protein. An alternative hypothesis is presented in which the sof mutations play the role of bypass mutations for kinases.

Lack of tolerance to nicotine-induced dopamine release in the nucleus accumbens

The extent to which repeated administration produces tolerance to nicotine-induced increases in dopamine transmission in the nucleus accumbens was investigated in rats. In vivo microdialysis was used to sample extracellular dopamine and metabolites after a nicotine challenge (0.35 mg/kg) in (1) naive rats, (2) acutely pretreated rats (1 prior nicotine injection), and (3) chronically pretreated rats (12-15 prior daily nicotine injections, 0.35 mg/kg per injection). Nicotine increased extracellular DA and its metabolites, and these increases were not significantly altered by either acute or chronic prior exposure to the drug. The failure to find evidence of tolerance is compatible with the hypothesis that the mesolimbic dopaminergic system is a substrate for the reinforcing properties of chronically administered nicotine.

Urinary excretion of albumin, alpha-1-microglobulin, and N-acetyl-B-D-glucosaminidase in relation to smoking habits in diabetic and nondiabetic subjects

Smoking may be a risk factor for the development of diabetic nephropathy. Therefore, the urinary excretion of albumin, alpha-1-microglobulin, and N-acetyl-BD glucosaminidase was studied in 24 young adult diabetic patients who smoked. None of these patients had urine samples positive for albumin as determined by the Albustix method (i.e., a urinary concentration of albumin of less than 0.5 g in 24 hr). Control groups were nonsmoking diabetic patients (matched for age and duration of diabetes) and nondiabetic subjects (smokers and nonsmokers). Expired breath carbon monoxide and the urinary nicotine metabolite cotinine were measured as objective markers of smoking load. No significant differences in concentrations of urinary proteins were found among any of the four groups. Therefore, smoking is not associated with the development of an increased urinary excretion of albumin within the "microalbuminuria" range. However, further studies are required to determine whether smoking is a risk factor for the progression of established microalbuminuria to Albustix positive proteinuria in diabetic patients.