MATRESHCA: Microtesla Apparatus for Transfer of Resonance Enhancement of Spin Hyperpolarization via Chemical Exchange and Addition

We present an integrated, open-source device for parahydrogen-based hyperpolarization processes in the microtesla field regime with a cost of components of less than $7000. The device is designed to produce a batch of 13C and 15N hyperpolarized (HP) compounds via hydrogenative or non-hydrogenative parahydrogen-induced polarization methods that employ microtesla magnetic fields for efficient polarization transfer of parahydrogen-derived spin order to X-nuclei (e.g., 13C and 15N). The apparatus employs a layered structure (reminiscent of a Russian doll "Matryoshka") that includes a nonmagnetic variable-temperature sample chamber, a microtesla magnetic field coil (operating in the range of 0.02-75 microtesla), a three-layered mu-metal shield (to attenuate the ambient magnetic field), and a magnetic shield degaussing coil placed in the overall device enclosure. The gas-handling manifold allows for parahydrogen-gas flow and pressure control (up to 9.2 bar of total parahydrogen pressure). The sample temperature can be varied either using a water bath or a PID-controlled heat exchanger in the range from -12 to 80 °C. This benchtop device measures 62 cm (length) × 47 cm (width) × 47 cm (height), weighs 30 kg, and requires only connections to a high-pressure parahydrogen gas supply and a single 110/220 VAC power source. The utility of the device has been demonstrated using an example of parahydrogen pairwise addition to form HP ethyl [1-13C]acetate (P13C = 7%, [c] = 1 M). Moreover, the Signal Amplification By Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei (SABRE-SHEATH) technique was employed to demonstrate efficient hyperpolarization of 13C and 15N spins in a wide range of biologically relevant molecules, including [1-13C]pyruvate (P13C = 14%, [c] = 27 mM), [1-13C]-α-ketoglutarate (P13C = 17%), [1-13C]ketoisocaproate (P13C = 18%), [15N3]metronidazole (P15N = 13%, [c] = 20 mM), and others. While the vast majority of the utility studies have been performed in standard 5 mm NMR tubes, the sample chamber of the device can accommodate a wide range of sample container sizes and geometries of up to 1 L sample volume. The device establishes an integrated, simple, inexpensive, and versatile equipment gateway needed to facilitate parahydrogen-based hyperpolarization experiments ranging from basic science to preclinical applications; indeed, detailed technical drawings and a bill of materials are provided to support the ready translation of this design to other laboratories.

Synthesis and PET Imaging Biodistribution Studies of Radiolabeled Iododiflunisal, a Transthyretin Tetramer Stabilizer, Candidate Drug for Alzheimer's Disease

The small-molecule iododiflunisal (IDIF) is a transthyretin (TTR) tetramer stabilizer and acts as a chaperone of the TTR-Amyloid beta interaction. Oral administration of IDIF improves Alzheimer's Disease (AD)-like pathology in mice, although the mechanism of action and pharmacokinetics remain unknown. Radiolabeling IDIF with positron or gamma emitters may aid in the in vivo evaluation of IDIF using non-invasive nuclear imaging techniques. In this work, we report an isotopic exchange reaction to obtain IDIF radiolabeled with 18F. [19F/18F]exchange reaction over IDIF in dimethyl sulfoxide at 160 °C resulted in the formation of [18F]IDIF in 7 ± 3% radiochemical yield in a 20 min reaction time, with a final radiochemical purity of >99%. Biodistribution studies after intravenous administration of [18F]IDIF in wild-type mice using positron emission tomography (PET) imaging showed capacity to cross the blood-brain barrier (ca. 1% of injected dose per gram of tissue in the brain at t > 10 min post administration), rapid accumulation in the liver, long circulation time, and progressive elimination via urine. Our results open opportunities for future studies in larger animal species or human subjects.

Development of Dissolution Dynamic Nuclear Polarization of [15 N3 ]Metronidazole: A Clinically Approved Antibiotic

We report dissolution Dynamic Nuclear Polarization (d-DNP) of [15 N3 ]metronidazole ([15 N3 ]MNZ) for the first time. Metronidazole is a clinically approved antibiotic, which can be potentially employed as a hypoxia-sensing molecular probe using 15 N hyperpolarized (HP) nucleus. The DNP process is very efficient for [15 N3 ]MNZ with an exponential build-up constant of 13.8 min using trityl radical. After dissolution and sample transfer to a nearby 4.7 T Magnetic Resonance Imaging scanner, HP [15 N3 ]MNZ lasted remarkably long with T1 values up to 343 s and 15 N polarizations up to 6.4 %. A time series of HP [15 N3 ]MNZ images was acquired in vitro using a steady state free precession sequence on the 15 NO2 peak. The signal lasted over 13 min with notably long T2 of 20.5 s. HP [15 N3 ]MNZ was injected in the tail vein of a healthy rat, and dynamic spectroscopy was performed over the rat brain. The in vivo HP 15 N signals persisted over 70 s, demonstrating an unprecedented opportunity for in vivo studies.

Nitrogen-15 and Fluorine-19 Relaxation Dynamics and Spin-Relayed SABRE-SHEATH Hyperpolarization of Fluoro-[15N3]metronidazole

Efficient ¹⁵N-hyperpolarization of [¹⁵N₃]metronidazole was reported previously using the Signal Amplification By Reversible Exchange in SHield Enabled Alignment Transfer (SABRE-SHEATH) technique. This hyperpolarized FDA-approved antibiotic is a potential contrast agent because it can be administered in a large dose and because previous studies revealed long-lasting HP states with exponential decay constant T₁ values of up to 10 min. Possible hypoxia-sensing applications have been proposed using hyperpolarized [¹⁵N₃]metronidazole. In this work, we report on the functionalization of [¹⁵N₃]metronidazole with a fluorine-19 moiety via a one-step reaction to substitute the -OH group. SABRE-SHEATH hyperpolarization studies of fluoro-[¹⁵N₃]metronidazole revealed efficient hyperpolarization of all three ¹⁵N sites with maximum %P_15N values ranging from 4.2 to 6.2%, indicating efficient spin-relayed polarization transfer in microtesla fields via the network formed by ²J_15N-15N. The corresponding ¹⁵N to ¹⁹F spin-relayed polarization transfer was found to be far less efficient with %P_19F of 0.16%, i.e., more than an order of magnitude lower than that of ¹⁵N. Relaxation dynamics studies in microtesla fields support a spin-relayed polarization transfer mechanism because all ¹⁵N and ¹⁹F spins share the same T₁ value of ca. 16-20 s and the same magnetic field profile for the SABRE-SHEATH polarization process. We envision the use of fluoro-[¹⁵N₃]metronidazole as a potential hypoxia sensor. It is anticipated that under hypoxic conditions, the nitro group of fluoro-[¹⁵N₃]metronidazole undergoes electronic stepwise reduction to an amino derivative. Ab initio calculations of ¹⁵N and ¹⁹F chemical shifts of fluoro-[¹⁵N₃]metronidazole and its putative hypoxia-induced metabolites clearly indicate that the chemical shift dispersions of all three ¹⁵N sites and the ¹⁹F site are large enough to enable the envisioned hypoxia-sensing approaches.

Rapid 13C Hyperpolarization of the TCA Cycle Intermediate α-Ketoglutarate via SABRE-SHEATH

α-Ketoglutarate is a key biomolecule involved in a number of metabolic pathways─most notably the TCA cycle. Abnormal α-ketoglutarate metabolism has also been linked with cancer. Here, isotopic labeling was employed to synthesize [1-13C,5-12C,D4]α-ketoglutarate with the future goal of utilizing its [1-13C]-hyperpolarized state for real-time metabolic imaging of α-ketoglutarate analytes and its downstream metabolites in vivo. The signal amplification by reversible exchange in shield enables alignment transfer to heteronuclei (SABRE-SHEATH) hyperpolarization technique was used to create 9.7% [1-13C] polarization in 1 minute in this isotopologue. The efficient 13C hyperpolarization, which utilizes parahydrogen as the source of nuclear spin order, is also supported by favorable relaxation dynamics at 0.4 μT field (the optimal polarization transfer field): the exponential 13C polarization buildup constant Tb is 11.0 ± 0.4 s whereas the 13C polarization decay constant T1 is 18.5 ± 0.7 s. An even higher 13C polarization value of 17.3% was achieved using natural-abundance α-ketoglutarate disodium salt, with overall similar relaxation dynamics at 0.4 μT field, indicating that substrate deuteration leads only to a slight increase (∼1.2-fold) in the relaxation rates for 13C nuclei separated by three chemical bonds. Instead, the gain in polarization (natural abundance versus [1-13C]-labeled) is rationalized through the smaller heat capacity of the "spin bath" comprising available 13C spins that must be hyperpolarized by the same number of parahydrogen present in each sample, in line with previous 15N SABRE-SHEATH studies. Remarkably, the C-2 carbon was not hyperpolarized in both α-ketoglutarate isotopologues studied; this observation is in sharp contrast with previously reported SABRE-SHEATH pyruvate studies, indicating that the catalyst-binding dynamics of C-2 in α-ketoglutarate differ from that in pyruvate. We also demonstrate that 13C spectroscopic characterization of α-ketoglutarate and pyruvate analytes can be performed at natural 13C abundance with an estimated detection limit of 80 micromolar concentration × *%P13C. All in all, the fundamental studies reported here enable a wide range of research communities with a new hyperpolarized contrast agent potentially useful for metabolic imaging of brain function, cancer, and other metabolically challenging diseases.

Synthetic Approaches for 15 N-Labeled Hyperpolarized Heterocyclic Molecular Imaging Agents for 15 N NMR Signal Amplification by Reversible Exchange in Microtesla Magnetic Fields

NMR hyperpolarization techniques enhance nuclear spin polarization by several orders of magnitude resulting in corresponding sensitivity gains. This enormous sensitivity gain enables new applications ranging from studies of small molecules by using high-resolution NMR spectroscopy to real-time metabolic imaging in vivo. Several hyperpolarization techniques exist for hyperpolarization of a large repertoire of nuclear spins, although the 13 C and 15 N sites of biocompatible agents are the key targets due to their widespread use in biochemical pathways. Moreover, their long T1 allows hyperpolarized states to be retained for up to tens of minutes. Signal amplification by reversible exchange (SABRE) is a low-cost and ultrafast hyperpolarization technique that has been shown to be versatile for the hyperpolarization of 15 N nuclei. Although large sensitivity gains are enabled by hyperpolarization, 15 N natural abundance is only ∼0.4 %, so isotopic labeling of the molecules to be hyperpolarized is required in order to take full advantage of the hyperpolarized state. Herein, we describe selected advances in the preparation of 15 N-labeled compounds with the primary emphasis on using these compounds for SABRE polarization in microtesla magnetic fields through spontaneous polarization transfer from parahydrogen. Also, these principles can certainly be applied for hyperpolarization of these emerging contrast agents using dynamic nuclear polarization and other techniques.

The microwave-assisted synthesis of 5-substituted 1H-tetrazoles via [3+2] cycloaddition over a heterogeneous Cu-based catalyst: application to the preparation of 13N-labelled tetrazoles

The [3+2] cycloaddition between various nitriles and sodium azide proceeds smoothly in the presence of a new Cu^II catalyst in N-methyl-2-pyrrolidone (NMP) to give the corresponding 5-substituted 1H-tetrazoles.

Cord IGF-I concentrations in Indian newborns: associations with neonatal body composition and maternal determinants

BACKGROUND

Indian newborns have been described as 'thin-fat' compared with European babies, but little is known about how this phenotype relates to the foetal growth factor IGF-I (insulin-like growth factor I) or its binding protein IGFBP-3.

OBJECTIVE

To assess cord IGF-I and IGFBP-3 concentrations in a sample of Indian newborns and evaluate their associations with neonatal adiposity and maternal factors.

METHODS

A prospective cohort study of 146 pregnant mothers with dietary, anthropometric and biochemical measurements at 28 and 34 weeks gestation. Neonatal weight, length, skin-folds, circumferences, and cord blood IGF-I and IGFBP-3 concentrations were measured at birth.

RESULTS

Average cord IGF-I and IGFBP-3 concentrations were 46.6 (2.2) and 1269.4 (41) ng mL(-1) , respectively. Girls had higher mean IGF-I than boys (51.4 ng mL(-1) vs. 42.9 ng mL(-1) ; P < 0.03), but IGFBP-3 did not differ. Cord IGF-I was positively correlated with all birth size measures except length, and most strongly with neonatal sum-of-skin-folds (r = 0.50, P < 0.001). IGFBP-3 was positively correlated with ponderal index, sum-of-skin-folds and placenta weight (r = 0.21, 0.19, 0.16, respectively; P < 0.05). Of maternal demographic and anthropometric characteristics, only parity was correlated with cord IGF-I (r = 0.27, P < 0.001). Among dietary behaviours, maternal daily milk intake at 34 weeks gestation predicted higher cord IGF-I compared to no-milk intake (51.8 ng mL(-1) vs. 36.5 ng mL(-1) , P < 0.01) after controlling for maternal characteristics, placental weight, and newborn gestational age, sex, weight and sum-of-skin-folds. Sum-of-skin-folds were positively associated with cord IGF-I in this multivariate model (57.3 ng mL(-1) vs. 35.1 ng mL(-1) for highest and lowest sum-of skin-fold quartile, P < 0.001). IGFBP-3 did not show significant relationships with these covariates.

CONCLUSION

In this Indian study, cord IGF-I concentration was associated with greater adiposity among newborns. Maternal milk intake may play a role in this relationship.

Synthesis of radiolabelled aryl azides from diazonium salts: experimental and computational results permit the identification of the preferred mechanism

Experimental and computational studies on the formation of aryl azides from the corresponding diazonium salts support a stepwise mechanism via acyclic zwitterionic intermediates. The low energy barriers associated with both transition structures are compatible with very fast and efficient processes, thus making this method suitable for the chemical synthesis of radiolabelled aryl azides.

Isolated bilateral oculomotor nerve palsy in pituitary apoplexy: case report and review

Pituitary tumours usually present with visual field defects; extraocular palsy is usually a sign of cavernous sinus extension and is a sign of advanced disease. We report a case of a pituitary adenoma presenting with complete, bilateral oculomotor nerve palsies, but minimal loss of visual fields, and intact abducens and trochlear nerves.

Efficacy of 99mTc-DTPA lung clearance test in the diagnosis of PCP in HIV-positive patients

The study aims to evaluate the efficacy of technetium-99m diethylenetriaminepentaacetic acid ((99m)Tc-DTPA) lung clearance test in the diagnosis of pneumocystis carinii pneumonia (PCP) in HIV-positive paediatric patients. Twenty HIV-negative patients with no chest symptoms constituted Group A, 25 HIV antibody positive asymptomatic children formed Group B, while 45 HIV antibody positive children with respiratory infections comprised Group C. Group C was subdivided into C(1) (n = 20, documented PCP on microbiology), C(2) (n = 10, tuberculosis) and C(3) (n = 15, bacterial pneumonias). The mean age group of patients in Group A, Group B and Group C was 4.7 +/- 1.9, 4.2 +/- 1.5 and 4.8 +/- 1.7 years, respectively. All patients were subjected to complete blood count, blood culture, chest radiographs, microscopic staining of sputum (PCP stains, Ziehl-Nielsen staining, Gram staining), ABG and Mantoux test. All these patients underwent dynamic lung scans using (99m)Tc-DTPA aerosols and lung clearance was calculated in terms of half-time transfer value (T(1/2)) value. T(1/2) was compared between different groups and lung scan findings were correlated with radiological and microbiological results. Patients with PCP had T(1/2) in the range of 9.02 +/- 1.35, TB 28.2 +/- 3.03 min and other bacterial pneumonias in the range of 20.5 +/- 3.1 min (range for normal individuals was 49.8 +/- 6.13 min). T(1/2) in patients with PCP was found to be significantly lower when compared with T(1/2) in other groups. Patients with PCP had characteristic biphasic curves while the rest had monophasic curves. Some patients with PCP had low T(1/2) values even when chest radiographs and arterial blood gases were normal. (99m)Tc-DTPA lung clearance test is a sensitive, safe and non-invasive diagnostic tool for the early detection of PCP in HIV-positive paediatric patients.

Analysis of wind-driven ambient noise in a shallow water environment with a sandy seabed

On the New Jersey continental shelf ambient sound levels were recorded during tropical storm Ernesto that produced wind speeds up to 40 knots in early September 2006. The seabed at the position of the acoustic measurements can be approximately described as coarse sand. Differences between the ambient noise levels for the New Jersey shelf measurements and deep water reference measurements are modeled using both normal mode and ray methods. The analysis is consistent with a nonlinear frequency dependent seabed attenuation for the New Jersey site.

A case of familial third ventricular colloid cyst

Colloid cyst of the third ventricle is a rare benign intracranial lesion, and familial cases are rarer still. They may be asymptomatic or present with symptoms of raised intracranial pressure, including sudden death. Surgical excision is curative. We report a 24 year old pregnant woman with familial colloid cyst, who presented with headaches and suffered a cardiorespiratory arrest. Early computed tomography scan of the brain is advised in patients with a family history of third ventricular colloid cyst presenting to the accident and emergency department with headache.

Spinal epidural abscess: a diagnostic challenge

The objective of the study was to highlight the diagnostic challenge of this elusive rare disease. A retrospective study of non-tuberculous spinal epidural abscesses (SEA) was carried out in Southern General Hospital, Glasgow, University Hospital of Wales, Cardiff, and Morriston Hospital, Swansea, from 1990 to 2000. Thirty-nine patients, consisting of 20 females and 19 males, with an age range from 20 to 85 years (mean: 61.1) were identified. Thirty-eight had localized back/neck pain. Eighteen were apyrexial. Twenty-nine demonstrated neurological deficit. All patients had raised inflammatory markers and gadolinium-enhanced magnetic resonance imaging (MRI) was diagnostic in 34. The most commonly identified organism was Staphylococcus aureus. All underwent surgical decompression, of which 13 required stabilization. Three died, seven lacked sphincter control and nine had motor deficit at the end of 1 year. It was concluded that fever is not mandatory for the diagnosis of SEA. Patients with localized back/neck pain and raised inflammatory markers need urgent MRI.

Evaluation of the polished surface characteristic of cobalt-chrome castings subsequent to various finishing and polishing techniques

Finishing and Polishing constitutes an essential requisite after the fabrication of removable partial dentures. Improper finishing and polishing of cast framework will adversely affect the quality of functional units of partial dentures due to reduced dimensions. In this study the polished surface characteristic and loss of weight of the casting were evaluated and compared following different finishing and polishing techniques. A total number of thirty test specimens were cast and each surface finishing and polishing technique was carried out with a high speed polishing motor and an electropolishing unit under standardised conditions. Surface roughness was evaluated by means of a surface roughness analyzing instrument, Perthometer. The loss of weight due to the metal lost was observed on a sensitive electronic balance. The results of polishing technique employed with G3 group revealed better surface characteristic. It may be understood that sandblasting causes initial roughness and the sequence of coarse cylindrical abrasive, Black hard rubber polisher (coarse grit-Dentauram), Grey hard rubber polisher (Med-grit-Dentauram), Green hard rubber polisher (Fine-grit-Dentauram), Grey flexible rubber polisher (Fine grit-Renfert), felt buff with pumice slurry and felt buff with green polishing compound (Degussa) produced improved surface in this case. The loss of weight due to metal lost show concern with technique groups G4, G5, G6. It can be avoided by judicious sandblasting and application of proper grit of abrasive agents.

Characterization of Rous sarcoma virus Gag particles assembled in vitro

Purified retrovirus Gag proteins or Gag protein fragments are able to assemble into virus-like particles (VLPs) in vitro in the presence of RNA. We have examined the role of nucleic acid and of the NC domain in assembly of VLPs from a Rous sarcoma virus (RSV) Gag protein and have characterized these VLPs using transmission electron microscopy (TEM), scanning TEM (STEM), and cryoelectron microscopy (cryo-EM). RNAs of diverse sizes, single-stranded DNA oligonucleotides as small as 22 nucleotides, double-stranded DNA, and heparin all promoted efficient assembly. The percentages of nucleic acid by mass, in the VLPs varied from 5 to 8%. The mean mass of VLPs, as determined by STEM, was 6.5 x 10(7) Da for both RNA-containing and DNA oligonucleotide-containing particles, corresponding to a stoichiometry of about 1,200 protein molecules per VLP, slightly lower than the 1,500 Gag molecules estimated previously for infectious RSV. By cryo-EM, the VLPs showed the characteristic morphology of immature retroviruses, with discernible regions of high density corresponding to the two domains of the CA protein. In spherically averaged density distributions, the mean radial distance to the density corresponding to the C-terminal domain of CA was 33 nm, considerably smaller than that of equivalent human immunodeficiency virus type 1 particles. Deletions of the distal portion of NC, including the second Zn-binding motif, had little effect on assembly, but deletions including the charged residues between the two Zn-binding motifs abrogated assembly. Mutation of the cysteine and histidine residues in the first Zn-binding motif to alanine did not affect assembly, but mutation of the basic residues between the two Zn-binding motifs, or of the basic residues in the N-terminal portion of NC, abrogated assembly. Together, these findings establish VLPs as a good model for immature virions and establish a foundation for dissection of the interactions that lead to assembly.

Role of the Rous sarcoma virus p10 domain in shape determination of gag virus-like particles assembled in vitro and within Escherichia coli

Purified retrovirus Gag proteins can assemble in vitro into virus-like particles (VLPs) in the presence of RNA. It was shown previously that a Rous sarcoma virus Gag protein missing only the protease domain forms spherical particles resembling immature virions lacking a membrane but that a similar protein missing the p10 domain forms tubular particles. Thus, p10 plays a role in spherical particle formation. To further study this shape-determining function, we dissected the p10 domain by mutagenesis and examined VLPs assembled within Escherichia coli or assembled in vitro from purified proteins. The results identified a minimal contiguous segment of 25 amino acid residues at the C terminus of p10 that is sufficient to restore efficient spherical assembly to a p10 deletion mutant. Random and site-directed mutations were introduced into this segment of polypeptide, and the shapes of particles formed in E. coli were examined in crude extracts by electron microscopy. Three phenotypes were observed: tubular morphology, spherical morphology, or no regular structure. While the particle morphology visualized in crude extracts generally was the same as that visualized for purified proteins, some tubular mutants scored as spherical when tested as purified proteins, suggesting that a cellular factor may also play a role in shape determination. We also examined the assembly properties of smaller Gag proteins consisting of the capsid protein-nucleocapsid protein (CA-NC) domains with short N-terminal extensions or deletions. Addition of one or three residues allowed CA-NC to form spheres instead of tubes in vitro, but the efficiency of assembly was extremely low. Deletion of the N-terminal residue(s) abrogated assembly. Taken together, these results imply that the N terminus of CA and the adjacent upstream 25 residues play an important role in the polymerization of the Gag protein.

The management of brain abscess in a developing country: are the results any different?

A retrospective study of 57 surgically-managed brain abscesses at the Neurosurgical Unit, Bir Hospital during a 6-year period from October 1990 is presented. Detailed hospital case notes could be traced in only 37 cases, consisting of 25 males and 12 females with age range from 5 months to 60 years. Cryptogenic abscess was the commonest category followed by abscess caused by chronic ear infection. The diagnosis was made with enhanced computed tomography (CT) in all the cases. Positive bacteriology was found in only nine cases. The treatment consisted of 6 weeks of intensive intravenous antibiotics and emergency surgical drainage of the abscess. Five out of the total cases died (13.5%). These patients were all in an extremely poor condition at the time of presentation. All the survivors made a good recovery. With timely CT diagnosis, surgical drainage and antibiotics, good results can be achieved even in a developing country.

Ex vivo treatment of bone marrow with phosphorothioate oligonucleotide OL(1)p53 for autologous transplantation in acute myelogenous leukemia and myelodysplastic syndrome

Effective ex vivo purging techniques can decrease the likelihood of infusing bone marrow contaminated with leukemic cells during autologous transplantation. In preliminary studies, OL(1)p53, a 20-mer phosphorothioate oligonucleotide directed against p53 mRNA, decreased the number of acute myelogenous leukemia (AML) cells in vitro, suggesting a possible role for OL(1)p53 in purging bone marrow harvests of leukemia cells. To demonstrate that OL(1)p53 was nontoxic to hematopoietic progenitor cells, normal bone marrow cells were incubated with 10 microM OL(1)p53 for 36 h, and hematopoietic progenitor cell survival was determined by in vitro colony assays. OL(1)p53 had no toxic effect on the growth of either myeloid (CFU-GM) or erythroid (BFU-E) progenitor cells. OL(1)p53 was then used to ex vivo purge bone marrow harvests from nine patients with either AML or myelodysplastic syndrome (MDS). Bone marrow cells were incubated with 10 microM OL(1)p53 for 36 h before transplantation. The median times posttransplantation for the patient to recover an absolute neutrophil count greater than 0.5 x 10(9)/L and a platelet transfusion independence were 30 days and 56 days, respectively. Incubation of bone marrow cells with OL(1)p53 had no detrimental effect on the growth of hematopoietic progenitor cells, and transplantation of autologous bone marrow cells treated with the phosphorothioate oligonucleotide, OL(1)p53, resulted in successful recovery of circulating neutrophils following high-dose therapy in patients with AML or MDS. The data show that OL(1)p53 can be used safely to purge autologous bone marrow harvests from patients with leukemia.

Experience with brain abscesses

Brain abscesses were studied in 47 patients. Thirty-four (72%) of them were between 5-15 years and 9 were infants. Otogenic source (34%) was the commonest predisposing factor, followed by scalp and face infection (21.3%) and congenital cyanotic heart disease (12.8%). Twenty (42%) patients had multiple abscesses. Supratentorial abscesses were commonest (75.9%). Predominant clinical features were fever (87.2%), raised intracranial tension (78.7%) and altered sensorium (53.2%). A total of 38.3% presented with focal neurological deficit and 34% were admitted in Grade III or IV coma. Diagnosis of abscess and monitoring of its evolution was done principally by CT scanning. Causative organisms were isolated in 54.8% of cases and Staphylococci, Proteus and Pseudomonas were the common pathogens. Therapy was most often a combination of surgical aspiration with or without excision in addition to antimicrobial therapy. The overall mortality in our series was 44.7%. Bad prognostic factors were Grade III/IV of coma at admission, age below 2 years and multiple abscesses.

Molecular properties of Drosophila acetylcholinesterase

Two distinct classes of acetylcholinesterase (AChE) from the fruit fly Drosophila melanogaster are reported: a soluble species that shows heterogeneity of forms and a particulate species. The subunit composition of the particulate enzyme was studied using the active site label [3H]diisopropylfluorophosphate. Comparison of the electrophoretic patterns on nondenaturing gels using the activity stain and the active site label shows that the label is specific to AChE. The smallest active site-containing subunit of the enzyme is a monomer of approximately 60,000 daltons MW. Two such units are linked by disulphide bonds to produce a dimer of about 110,000 daltons. Another monomeric form of MW approximately 64,000 daltons, although present, does not participate in the dimerisation. The particulate enzyme when solubilised exists as a 9-10S species as determined by sucrose gradient centrifugation. This species has a MW greater than 200,000, as shown by its behaviour on a coarse-bead Sephadex-G200 column. Electrophoretic analysis suggests a MW of nearly 250,000 daltons for this form. Thus, this species is likely to be a tetramer. One possibility is that this tetramer is made up of two units of 64,000 daltons each and a dimer of 110,000 daltons. Preliminary data on mutant enzymes that support such a possibility are also presented.