Processing of the initiation methionine from proteins: properties of the Escherichia coli methionine aminopeptidase and its gene structure

Methionine aminopeptidase (MAP) catalyzes the removal of amino-terminal methionine from proteins. The Escherichia coli map gene encoding this enzyme was cloned; it consists of 264 codons and encodes a monomeric enzyme of 29,333 daltons. In vitro analyses with purified enzyme indicated that MAP is a metallo-oligopeptidase with absolute specificity for the amino-terminal methionine. The methionine residues from the amino-terminal end of the recombinant proteins interleukin-2 (Met-Ala-Pro-IL-2) and ricin A (Met-Ile-Phe-ricin A) could be removed either in vitro with purified MAP enzyme or in vivo in MAP-hyperproducing strains of E. coli. In vitro analyses of the substrate preference of the E. coli MAP indicated that the residues adjacent to the initiation methionine could significantly influence the methionine cleavage process. This conclusion is consistent, in general, with the deduced specificity of the enzyme based on the analysis of known amino-terminal sequences of intracellular proteins (S. Tsunasawa, J. W. Stewart, and F. Sherman, J. Biol. Chem. 260:5382-5391, 1985).

Identification of a new class of molecules, the arachidonyl amino acids, and characterization of one member that inhibits pain

In mammals, specific lipids and amino acids serve as crucial signaling molecules. In bacteria, conjugates of lipids and amino acids (referred to as lipoamino acids) have been identified and found to possess biological activity. Here, we report that mammals also produce lipoamino acids, specifically the arachidonyl amino acids. We show that the conjugate of arachidonic acid and glycine (N-arachidonylglycine (NAGly)) is present in bovine and rat brain as well as other tissues and that it suppresses tonic inflammatory pain. The biosynthesis of NAGly and its degradation by the enzyme fatty acid amide hydrolase can be observed in rat brain tissue. In addition to NAGly, bovine brain produces at least two other arachidonyl amino acids: N-arachidonyl gamma-aminobutyric acid (NAGABA) and N-arachidonylalanine. Like NAGly, NAGABA inhibits pain. These findings open the door to the identification of other members of this new class of biomolecules, which may be integral to pain regulation and a variety of functions in mammals.

Simultaneous bilateral laser therapy accelerates recovery after noise-induced hearing loss in a rat model

Noise-induced hearing loss is a common type of hearing loss. The effects of laser therapy have been investigated from various perspectives, including in wound healing, inflammation reduction, and nerve regeneration, as well as in hearing research. A promising feature of the laser is its capability to penetrate soft tissue; depending on the wavelength, laser energy can penetrate into the deepest part of the body without damaging non-target soft tissues. Based on this idea, we developed bilateral transtympanic laser therapy, which uses simultaneous laser irradiation in both ears, and evaluated the effects of bilateral laser therapy on cochlear damage caused by noise overexposure. Thus, the purpose of this research was to assess the benefits of simultaneous bilateral laser therapy compared with unilateral laser therapy and a control. Eighteen Sprague-Dawley rats were exposed to narrow-band noise at 115 dB SPL for 6 h. Multiple auditory brainstem responses were measured after each laser irradiation, and cochlear hair cells were counted after the 15th such irradiation. The penetration depth of the 808 nm laser was also measured after sacrifice. Approximately 5% of the laser energy reached the contralateral cochlea. Both bilateral and unilateral laser therapy decreased the hearing threshold after noise overstimulation in the rat model. The bilateral laser therapy group showed faster functional recovery at all tested frequencies compared with the unilateral laser therapy group. However, there was no difference in the endpoint ABR results or final hair cell survival, which was analyzed histologically.

Founding mutations and Alu-mediated recombination in hereditary colon cancer

By screening members of Finnish families displaying hereditary nonpolyposis colorectal cancer (HNPCC) for predisposing germline mutations in MSH2 and MLH1, we show that two mutations in MLH1 together account for 63% (19/30) of kindreds meeting international diagnostic criteria. Mutation 1, originally detected as a 165-base pair deletion in MLH1 cDNA comprising exon 16, was shown to consist of a 3.5-kilobase genomic deletion most likely resulting from Alu-mediated recombination. Mutation 2 destroys the splice acceptor site of exon 6. A simple diagnostic test based on polymerase chain reaction was designed for both mutations. Our results show that these two ancestral founding mutations account for a majority of Finnish HNPCC kindreds and represent the first report of Alu-mediated recombination causing a prevalent, dominantly inherited predisposition to cancer.

Methionine aminopeptidase gene of Escherichia coli is essential for cell growth

We localized the methionine aminopeptidase (map) gene on the Escherichia coli chromosome next to the rpsB gene at min 4. Genetically modified strains with the chromosomal map gene under lac promoter control grew only in the presence of the lac operon inducer isopropyl-beta-thiogalactoside. Thus, methionine aminopeptidase is essential for cell growth.

An internal control for routine diagnostic PCR: design, properties, and effect on clinical performance

We constructed internal controls (ICs) to provide assurance that clinical specimens are successfully amplified and detected. The IC nucleic acids contain primer binding regions identical to those of the target sequence and contain a unique probe binding region that differentiates the IC from amplified target nucleic acid. Because only 20 copies of the IC are introduced into each test sample, a positive IC signal indicates that amplification was sufficient to generate a positive signal from targets present at the limit of test sensitivity. The COBAS AMPLICOR Chlamydia trachomatis, Neisseria gonorrhoeae, Mycobacterium tuberculosis, and human hepatitis C virus tests exhibited inhibition rates ranging from 5 to 9%. Approximately 64% of these inhibitory specimens were not inhibitory when a second aliquot was tested. Because repeatedly inhibitory specimens were not reported as false negative and because additional infected specimens were detected during retesting, test sensitivities were 1 to 6% greater than they would have been if the IC had not been used.

Fast three dimensional sodium imaging

An efficient scheme for fast three dimensional acquisition of sodium MR images is described. This scheme relies on the use of three dimensional k-space trajectories with constant sample density to achieve significant (60-70%) reductions in total data acquisition time over conventional projection imaging schemes. The performance of this data acquisition scheme is demonstrated with acquisition of sodium data sets on phantoms and normal human volunteers at 1.5 and 3.0 Tesla. The experimental results demonstrate that high quality three dimensional sodium images (0.2 cc voxel size, 10:1 signal-to-noise ratio) can be acquired at clinical field strengths (1.5 Tesla) in under 10 min.

High-level expression, purification, and enzymatic characterization of full-length Thermus aquaticus DNA polymerase and a truncated form deficient in 5' to 3' exonuclease activity

The Thermus aquaticus DNA polymerase I (Taq Pol I) gene was cloned into a plasmid expression vector that utilizes the strong bacteriophage lambda PL promoter. A truncated form of Taq Pol I was also constructed. The two constructs made it possible to compare the full-length 832-amino-acid Taq Pol I and a deletion derivative encoding a 544-amino-acid translation product, the Stoffel fragment. Upon heat induction, the 832-amino-acid construct produced 1-2% of total protein as Taq Pol I. The induced 544-amino-acid construct produced 3% of total protein as Stoffel fragment. Enzyme purification included cell lysis, heat treatment followed by Polymin P precipitation of nucleic acids, phenyl sepharose column chromatography, and heparin-Sepharose column chromatography. For full-length 94-kD Taq Pol I, yield was 3.26 x 10(7) units of activity from 165 grams wet weight cell paste. For the 61-kD Taq Pol I Stoffel fragment, the yield was 1.03 x 10(6) units of activity from 15.6 grams wet weight cell paste. The two enzymes have maximal activity at 75 degrees C to 80 degrees C, 2-4 mM MgCl2 and 10-55 mM KCl. The nature of the substrate determines the precise conditions for maximal enzyme activity. For both proteins, MgCl2 is the preferred cofactor compared to MnCl2, CoCl2, and NiCl2. The full-length Taq Pol I has an activity half-life of 9 min at 97.5 degrees C. The Stoffel fragment has a half-life of 21 min at 97.5 degrees C. Taq Pol I contains a polymerization-dependent 5' to 3' exonuclease activity whereas the Stoffel fragment, deleted for the 5' to 3' exonuclease domain, does not possess that activity. A comparison is made among thermostable DNA polymerases that have been characterized; specific activities of 292,000 units/mg for Taq Pol I and 369,000 units/mg for the Stoffel fragment are the highest reported.

Transcript imaging of the development of human T helper cells using oligonucleotide arrays

Many pathological processes, including those causing allergies and autoimmune diseases, are associated with the presence of specialized subsets of T helper cells at the site of inflammation. Understanding the genetic program that controls the functional properties of T helper type 1 (Th1) versus T helper type 2 (Th2) cells may provide insight into the pathophysiology of inflammatory diseases. We compared the gene-expression profiles of human Th1 and Th2 cells using high-density oligonucleotide arrays with the capacity to display transcript levels of 6,000 human genes. Here we analyse the data sets derived from five independent experiments using statistical algorithms. This approach resulted in the identification of 215 differentially expressed genes, encoding proteins involved in transcriptional regulation, apoptosis, proteolysis, and cell adhesion and migration. A subset of these genes was further upregulated by exposure of differentiated Th1 cells to interleukin-12 (IL-12), as confirmed by kinetic PCR analysis, indicating that IL-12 modulates the effector functions of Th1 cells in the absence of antigenic stimulation. Functional assays and in vivo expression of selected genes have validated the biological relevance of our study. Our results provide new insight into the transcriptional program controlling the functional diversity of subsets of T helper cells.

Human immunodeficiency virus type 1 subtype C molecular phylogeny: consensus sequence for an AIDS vaccine design?

An evolving dominance of human immunodeficiency virus type 1 subtype C (HIV-1C) in the AIDS epidemic has been associated with a high prevalence of HIV-1C infection in the southern African countries and with an expanding epidemic in India and China. Understanding the molecular phylogeny and genetic diversity of HIV-1C viruses may be important for the design and evaluation of an HIV vaccine for ultimate use in the developing world. In this study we analyzed the phylogenetic relationships (i) between 73 non-recombinant HIV-1C near-full-length genome sequences, including 51 isolates from Botswana; (ii) between HIV-1C consensus sequences that represent different geographic subsets; and (iii) between specific isolates and consensus sequences. Based on the phylogenetic analyses of 73 near-full-length genomes, 16 "lineages" (a term that is used hereafter for discussion purposes and does not imply taxonomic standing) were identified within HIV-1C. The lineages were supported by high bootstrap values in maximum-parsimony and neighbor-joining analyses and were confirmed by the maximum-likelihood method. The nucleotide diversity between the 73 HIV-1C isolates (mean value of 8.93%; range, 2.9 to 11.7%) was significantly higher than the diversity of the samples to the consensus sequence (mean value of 4.86%; range, 3.3 to 7.2%, P < 0.0001). The translated amino acid distances to the consensus sequence were significantly lower than distances between samples within all HIV-1C proteins. The consensus sequences of HIV-1C proteins accompanied by amino acid frequencies were presented (that of Gag is presented in this work; those of Pol, Vif, Vpr, Tat, Rev, Vpu, Env, and Nef are presented elsewhere [http://www.aids.harvard.edu/lab_research/concensus_sequence.htm]). Additionally, in the promoter region three NF-kappa B sites (GGGRNNYYCC) were identified within the consensus sequences of the entire set or any subset of HIV-1C isolates. This study suggests that the consensus sequence approach could overcome the high genetic diversity of HIV-1C and facilitate an AIDS vaccine design, particularly if the assumption that an HIV-1C antigen with a more extensive match to the circulating viruses is likely to be more efficacious is proven in efficacy trials.

Lack of infection in HIV-exposed individuals is associated with a strong CD8(+) cell noncytotoxic anti-HIV response

Individuals repeatedly exposed to HIV, but who remain uninfected, form a population enriched for persons likely to have either natural or acquired resistance to the virus. We have studied four such exposed uninfected cohorts, representing 60 individuals, for evidence of protective immunity. This population included participants exposed to HIV through anal or vaginal receptive intercourse on multiple occasions over many years. We observed CD8(+)-cell noncytotoxic inhibition of HIV replication in acutely infected CD4(+) cells in the vast majority of individuals most recently exposed to the virus (within 1 year). The levels of this CD8(+)-cell response were sufficient to inhibit the in vitro infection of the exposed subjects' peripheral blood mononuclear cells. We found no evidence of a significant role for CCR5 Delta32 mutation in this population, nor did CD4(+) cell susceptibility to infection or HIV-specific cytotoxic T-lymphocytes correlate with resistance to infection in the individuals tested. Therefore, the observed strong noncytotoxic CD8(+)-cell anti-HIV responses may be an antiviral immune activity contributing to the apparent protection from infection in these exposed uninfected individuals.

Transcriptional analysis of multiple sclerosis brain lesions reveals a complex pattern of cytokine expression

Multiple sclerosis (MS) is a common and severe neurological disorder associated with an autoimmune response directed against myelin components within the CNS. Lymphocyte activation, extravasation, and recruitment, as well as effector function, involves the turning on and off of a number of genes, thus triggering specific transcriptional pathways. The characterization of the transcriptome in MS lesions should provide a better understanding of the mechanisms that generate and sustain the pathogenic immune response in this disease. Here we performed transcriptional profiling of 56 relevant genes in brain specimens from eight MS patients and eight normal controls by kinetic RT-PCR. Results showed a high transcriptional activity for the gene coding for myelin basic protein (MBP); however, it was not differentially expressed in MS samples, suggesting that remyelination is an active process also in the noninflammatory brain. CD4 and HLA-DRalpha transcripts were dramatically increased in MS as compared with controls. This reveals a robust MHC class II up-regulation and suggests that Ag is being presented locally to activated T cells. Although analysis of cytokine and cytokine receptor genes expression showed predominantly increased levels of several Th1 molecules (TGF-ss, RANTES, and macrophage-inflammatory protein (MIP)-1alpha) in MS samples, some Th2 genes (IL-3, IL-5, and IL-6/IL-6R) were found to be up-regulated as well. Similarly, both proinflammatory type (CCR1, CCR5) and immunomodulatory type (CCR4, CCR8) chemokine receptors were differentially expressed in the MS brain. Overall, our data suggest a complex regulation of the inflammatory response in human autoimmune demyelination.

The urinary excretion of nucleosides of ribonucleic acid by patients with advanced cancer

By means of a sensitive and specific method utilizing gas-liquid chromatography, the excretion levels for three nucleosides, degradation minor base products of ribonucleic acid, primarily transfer ribonucleic acid, were determined in 24-hour urine specimens from over 200 patients with solid tumor malignancies. These nucleosides were N2,N2-dimethylguanosine, l-methylinosine, and pseudouridine. When compared to normal control values, elevated levels of these compounds were found for patients in each of several tumor types studied. Increases in pseudouridine excretion suggest increased tumor transfer ribonucleic acid turnover; in addition, for the methylated nucleosides, higher than normal values may reflect enhanced transfer ribonucleic acid methylase activity of the neoplastic cells.

Identification of human immunodeficiency virus type 1 subtype C Gag-, Tat-, Rev-, and Nef-specific elispot-based cytotoxic T-lymphocyte responses for AIDS vaccine design

The most severe human immunodeficiency virus type 1 (HIV-1) epidemic is occurring in southern Africa. It is caused by HIV-1 subtype C (HIV-1C). In this study we present the identification and analysis of cumulative cytotoxic T-lymphocyte (CTL) responses in the southern African country of Botswana. CTLs were shown to be an important component of the immune response to control HIV-1 infection. The definition of optimal and dominant epitopes across the HIV-1C genome that are targeted by CTL is critical for vaccine design. The characteristics of the predominant virus that causes the HIV-1 epidemic in a certain geographic area and also the genetic background of the population, through the distribution of common HLA class I alleles, might impact dominant CTL responses in the vaccinee and in the general population. The enzyme-linked immunospot (Elispot) gamma interferon assay has recently been shown to be a reliable tool to map optimal CTL epitopes, correlating well with other methods, such as intracellular staining, tetramer staining, and the classical chromium release assay. Using Elispot with overlapping synthetic peptides across Gag, Tat, Rev, and Nef, we analyzed HIV-1C-specific CTL responses of HIV-1-infected blood donors. Profiles of cumulative Elispot-based CTL responses combined with diversity and sequence consensus data provide an additional characterization of immunodominant regions across the HIV-1C genome. Results of the study suggest that the construction of a poly-epitope subtype-specific HIV-1 vaccine that includes multiple copies of immunodominant CTL epitopes across the viral genome, derived from predominant HIV-1 viruses, might be a logical approach to the design of a vaccine against AIDS.

alpha-Amylase gene of Streptomyces limosus: nucleotide sequence, expression motifs, and amino acid sequence homology to mammalian and invertebrate alpha-amylases

The nucleotide sequence of the coding and regulatory regions of the alpha-amylase gene (aml) of Streptomyces limosus was determined. High-resolution S1 mapping was used to locate the 5' end of the transcript and demonstrated that the gene is transcribed from a unique promoter. The predicted amino acid sequence has considerable identity to mammalian and invertebrate alpha-amylases, but not to those of plant, fungal, or eubacterial origin. Consistent with this is the susceptibility of the enzyme to an inhibitor of mammalian alpha-amylases. The amino-terminal sequence of the extracellular enzyme was determined, revealing the presence of a typical signal peptide preceding the mature form of the alpha-amylase.

Nucleotide sequence of the Escherichia coli prolipoprotein signal peptidase (lsp) gene

The nucleotide sequence of the prolipoprotein signal peptidase (lsp) gene has been determined. The lsp gene was found to be adjacent to the isoleucyl-tRNA synthetase ( ileS ) gene, such that the termination codon of the ileS gene overlaps with the initiation codon of lsp. These two genes are transcribed in the same direction and the major promotor for the lsp gene appears to be upstream of ileS . Identification of the lsp gene was established by amplification of prolipoprotein signal peptidase activity in strains carrying a subcloned 1.1-kilobase Stu I-Acc I fragment and was further confirmed by introducing mutational alterations in the COOH terminus of the protein that caused a decrease in prolipoprotein signal peptidase activity. The deduced amino acid sequence indicates that prolipoprotein signal peptidase contains 164 residues. Unlike most exported proteins, there is no apparent signal peptide sequence for the lsp protein. Computer-assisted secondary structure analysis of the deduced amino acid sequence identified four hydrophobic regions that share features common to transmembrane segments in integral membrane proteins.

Oral melphalan kinetics

The systemic availability of melphalan after oral administration is not well known. Most patients are put on a fixed oral dosage regimen. We have studied the disposition of melphalan in 14 patients after single oral doses. Five were also studied after receiving the same dose intravenously. Oral melphalan had a mean plasma terminal phase half-life (t1/2) of 90 +/- 17 min. The mean area under the plasma concentration:time curve (CXT) was 53 +/- 33 micrograms . min/ml. Urinary excretion of oral melphalan averaged 10.9 +/- 4.9% during the first 24 hr. The CXT ratio (oral:intravenous) for the 5 patients studied after both oral and intravenous melphalal (0.6 mg/kg) ranged between 0.25 and 0.89 and averaged 0.56. After oral dosing in 14 fasting patients, the time at which melphalan first appeared in the plasma varied between 15 min and 6 hr. In a myeloma patient who took oral melphalan, no melphalan was found in plasma or urine up to 24 hr. Some instances of failure of tumor response to oral melphalan may be due to inadequate bioavailability rather than inherent tumor resistance.

Efficacy of methotrexate treatment in viable and nonviable cervical pregnancies

OBJECTIVES

This retrospective study examined the overall efficacy of methotrexate chemotherapy in the treatment of cervical pregnancy and attempted to determine whether differences in the response to methotrexate therapy exist between patients with viable and nonviable cervical pregnancies.

STUDY DESIGN

A MEDLINE database search and a bibliographic review of the relevant literature were conducted to find reported cases of cervical pregnancy treated with methotrexate administration during the period from 1983 to 1997. Clinical and demographic characteristics, methotrexate regimen, concomitant invasive procedures, complications, and outcomes in viable and nonviable pregnancy groups were analyzed and compared.

RESULTS

A total of 62 reported cases of cervical pregnancy were assessed. There were no statistically significant differences in demographic data, transfusion rate, and human chorionic gonadotropin remission time between viable and nonviable cervical pregnancy groups. Among the 35 cases of viable pregnancy 63% of women received systemic injection alone or a combination of systemic and local (intra-amniotic or intracervical) injection with methotrexate or potassium chloride and 37% had local injection of methotrexate (with or without potassium chloride) alone. Among the 23 cases of nonviable cervical pregnancy 96% of women received systemic methotrexate injection only. The need for >/=1 concomitant surgical procedure (such as simple curettage, dilation and curettage, cervical blocking, or uterine artery embolization) in conjunction with methotrexate therapy was significantly higher (P =.021) in the viable pregnancy group (43%) than in the nonviable pregnancy group (13%). The 94% success rate of preservation of the uterus in the viable pregnancy group was not significantly different from the 91% preservation rate in the nonviable pregnancy group. All patients who had successful uterine preservation returned to normal menstrual patterns.

CONCLUSION

This retrospective study found that conservative treatment with methotrexate chemotherapy of patients with either viable or nonviable cervical pregnancies at <12 weeks' gestation carries a 91% success rate for preservation of the uterus. The structure of the cervix was restored and menstruation returned for all patients in whom the uterus was preserved after treatment. There was no evidence to suggest that the reproductive performance of these patients was affected by the treatment.

Enhancing effect of polyoxyethylene alkyl ethers on the skin permeation of ibuprofen

The influence of polyethoxylated non-ionic surfactants on the transport of ibuprofen across rat skin was investigated. The skin permeation of ibuprofen from a series of 17 polyoxyethylene (POE) alkyl ethers containing 5% ibuprofen was determined using Franz diffusion cells fitted with excised rat skins. Differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR) were performed for the physicochemical characterization of ibuprofen-surfactant interaction. In vitro transdermal flux through excised rat skin was found in the decreasing order of POE(5)cetyl/oleyl ether (110.24 microg/cm(2)/h)>POE(2)lauryl ether (99.91 microg/cm(2)/h)>POE(2)oleyl ether (67.46 microg/cm(2)/h)>POE(10)stearyl ether (66.19 microg/cm(2)/h). POE(2)oleyl ether showed the longest lag time (2.47 h). The enhancers containing the EO chain length of 2-5, HLB value of 7-9 and an alkyl chain length of C16-C18 were effective promoters of ibuprofen flux. FT-IR and DSC studies to probe the nature of the interaction between the ibuprofen and surfactant indicated that the hydrogen bonding state of ibuprofen was changed from the dimeric form to the carbonyl-hydroxyl (C=O-HO) hydrogen bond form in the presence of excess POE alkyl ether. These results indicated that this new system may be used in developing a transdermal formulation with improved skin permeation of ibuprofen.

Kinetics of intravenous melphalan

We have studied the disposition and elimination of melphalan after intravenous administration in 9 patients with cancer. High-pressure liquid chromatography and 14C-melphalan were used to assay drug concentration in plasma and urine. Composite plasma t1/2alpha was 7.7 +/- 3.3 and t1/2beta was 108 +/- 20.8 min for 8 of the patients. The mean 24-hr urinary excretion of melphalan was 13.0 +/- 5.4% of the administered dose. In 2 patients, 80% to 100% of the measured 14C counts in plasma and urine samples at each study interval, up to 24 hr after drug administration, could be accounted for by the sum of parent compound, monohydroxy and dihydroxy products, and methanol nonextractable radioactivity (i.e., protein-bound activity). These data and evidence of rapid disappearance from plasma at 37 degrees in vitro suggest that spontaneous degradation, and not enzymatic metabolism, is the major determinant of the t1/2 of melphalan in vivo.

Long-term outcome and prognostic indicators in the hemolytic-uremic syndrome

We examined 61 patients an average of 9.6 years (range 5 to 18 years) after an episode of childhood hemolytic-uremic syndrome. Twenty-four (39%) had one or more abnormalities. Seven (11%) had proteinuria and six (10%) had low creatinine clearance as solitary abnormalities. Eight (13%) had both proteinuria and reduced creatinine clearance; three (5%) had a combination of hypertension, proteinuria, and low creatinine clearance. Abnormalities sometimes appeared after an interval of apparent recovery. Logistic regression analysis showed that duration of anuria was the best predictor of disease at follow-up. No patients who had anuria lasting longer than 8 days or oliguria exceeding 15 days escaped chronic disease. However, 45% of those with disease had no anuria, and a third had no oliguria. Physicians should therefore be cautious in assuming recovery from HUS on the basis of a single evaluation and should periodically evaluate patients for an extended period.

Hydrolysis and protein binding of melphalan

Melphalan (30 microgram/ml) is completely hydrolyzed in water at 37 degrees after 8 hr. At lower temperatures, hydrolysis proceeds at slower rates. The presence of bovine serum albumin retards hydrolysis of melphalan (30 microgram/ml) in water. The melphalan hydrolysis rate is directely releated to the bovine serum albumin concentration. At 37 degrees, 8 g of bovine serum albumin/100 ml of water gives a recovery rate of melphalan similar to that of human plasma. In vitro alkylation of melphalan at 37 degrees with human plasma containing 30 microgram/ml, calculated by equilibrium dialysis, methanol extraction, and high-pressure liquid chromatographic analysis, is 30% after 8 hr.

Spectrally weighted twisted projection imaging: reducing T2 signal attenuation effects in fast three-dimensional sodium imaging

A scheme for the reduction of T2 signal attenuation effects in three-dimensional twisted projection imaging is presented. By purposely reducing the sample density at the high spatial frequencies, a considerable reduction in readout time is achieved. The reduction in readout time leads to decreased T2 signal attenuation which translates into improved signal-to-noise ratio (SNR). The SNR improvement is achieved without decreasing the image's resolution since the point spread function depends on the sample weighting as well as the T2 attenuation. The results indicate that SNR improvements of up to 40% can be achieved using the proposed scheme.