Utility of pharmacodynamic measures for assessing the oral bioavailability of peptides. 1. Administration of recombinant salmon calcitonin in rats

Salmon calcitonin (sCT) is a therapeutic peptide used in the treatment of Paget's Disease, postmenopausal osteoporosis, and hypercalcemia due to malignancy. In this study, recombinant sCT (rsCT) was administered intravenously (iv), subcutaneously (sc), and intraduodenally (id.) in rats to evaluate pharmacodynamic (PD) response as a measure of rsCT bioavailability (F) and to test the feasibility of delivering rsCT orally. rsCT pharmacokinetics were linear throughout the range of iv and sc doses studied. Following sc administration, F ranged from 11.2% to 23.1% and was linear. The absorption of rsCT after id. administration was low (0.022%); however, a significant lowering of serum calcium concentrations was observed. Serum calcium lowering was nonlinear and saturable after sc administration with the minimum dose required for maximum calcium lowering (Dmin/max) equal to 10.2 ng and a maximal response of 426.8 mg min/dL. Using Dmin/max as the reference dose, absolute Fs were recalculated using PD response after id. administration of 1 and 2 mg of rsCT and were 0.040% and 0.029%, respectively. Substantial overestimates of F were obtained when the reference dose was not properly selected. While the absorption of rsCT was low, the significant lowering of serum calcium levels suggests that oral delivery of sCT is feasible. The results of these studies also suggest that PD response is useful in assessing the oral bioavailability of peptides; however, when PD response is saturable, as is the case for rsCT, the reference dose should be carefully selected in order to avoid overestimates of F.

A DNA sequencing strategy that requires only five bases of known terminal sequence for priming

We have previously reported an enhanced version of sequencing by hybridization (SBH), termed positional SBH (PSBH). PSBH uses partially duplex probes containing single-stranded 3' overhangs, instead of simple single-stranded probes. Stacking interactions between the duplex probe and a single-stranded target allow us to reduce the probe sizes required to 5-base single-stranded overhangs. Here we demonstrate the use of PSBH to capture relatively long single-stranded DNA targets and perform standard solid-state Sanger sequencing on these primer-template complexes without ligation. Our results indicate that only 5 bases of known terminal sequence are required for priming. In addition, the partially duplex probes have the ability to capture their specific target from a mixture of five single-stranded targets with different 3'-terminal sequences. This indicates the potential utility of the PSBH approach to sequence mixtures of DNA targets without prior purification.

Endogenous endonuclease hypersensitive sites in Schizosaccharomyces pombe chromosomes

A novel method was used to characterize the long range susceptibility of Schizosaccharomyces pombe chromosomal DNA to endogenous endonuclease cleavage. Analyses of pulsed field gel experiments revealed two periodicities in the distribution of endogenous endonuclease hypersensitive sites. Endonuclease cleavage sites occurred, roughly at 30-509 kilobase pairs (kb) intervals under physiological conditions (25 mM KCl). At higher salt concentrations (250 mM KCl or 0.2 M and 0.9 M NaCl), endonuclease hypersensitive sites occurred at 200-300 kb intervals. Endonuclease hypersensitive sites in different chromosomal regions were monitored during different stages of the cell cycle. DNA sequencing around the endonuclease hypersensitive sites revealed the presence of clusters of A+T-rich motifs, autonomously replicating sequences (ARSs) in sequences (a characteristic of the scaffold-associated regions (SARs) and the presence of a CTG trinucleotide at most sites.

Protein translation components are colocalized in granules in oligodendrocytes

The intracellular distribution of various components of the protein translational machinery was visualized in mouse oligodendrocytes in culture using high resolution fluorescence in situ hybridization and immunofluorescence in conjunction with dual channel confocal laser scanning microscopy. Arginyl-tRNA synthetase, elongation factor 1a, ribosomal RNA, and myelin basic protein mRNA were all co-localized in granules in the processes, veins and membrane sheets of the cell. Colocalization was evaluated by dual channel cross correlation analysis to determine the correlation index (% colocalization) and correlation distance (granule radius), and by single granule ratiometric analysis to determine the distribution of the different components in individual granules. Most granules contained synthetase, elongation factor, ribosomal RNA and myelin basic protein mRNA. These results indicate that several different components of the protein synthetic machinery, including aminoacyl-tRNA synthetases, elongation factors, ribosomes and mRNAs, are colocalized in granules in oligodendrocytes. We propose that these granules are supramolecular complexes containing all of the necessary macromolecular components for protein translation and that they represent a heretofore undescribed subcellular organization of the protein synthetic machinery. This spatial organization may increase the efficiency of protein synthesis and may also provide a vehicle for transport and localization of specific mRNAs within the cell.

Development of a biologically active fluorescent-labeled calcitriol and its use to study hormone binding to the vitamin D receptor

To gain better insight into the mechanism of steroid receptor activation and calcitriol action, we have developed the first pharmacologically relevant fluorescent-labeled ligand for the vitamin D receptor (VDR). Purity and structure of three BODIPY-labeled calcitriol derivatives were characterized by TLC, HPLC, and 1H-NMR spectroscopy. 3 beta-BODIPY-calcitriol was the most potent derivative to induce 25-hydroxyvitamin D3 24-hydroxylase activity and to inhibit cell proliferation. It was taken up rapidly and specifically and was not cleaved by endogenous esterases. 3 beta-BODIPY-calcitriol also retained high-affinity binding to the VDR. Hormone binding to the receptor was measured by spectrofluorometry in high-salt extracts from cultured cells with wild-type VDR, from cells virally over-expressing the human VDR, and in intact cells with and without VDR. Results from fluorescent binding studies agreed with results from radioligand assays. The most useful feature of this reagent is that its fluorescence emission increases severalfold upon binding to VDR. This allows direct monitoring by microscopy of ligand receptor interactions in living cells. Fluorescent-labeled calcitriol can be a valuable diagnostic tool for cancer research and is essential for exploring the subcellular localization of VDRs.

Characterization of the human glucocorticoid receptor promoter

To elucidate the functional elements that are involved in the regulation of the human glucocorticoid receptor (hGR) gene, transient expression, DNase I footprinting, and gel mobility shift analyses were conducted. We found that the hGR promoter region between -700 and +38 bp contained 11 footprinted sites. Deletion of the -374 to -183 bp region, which is highly conserved between human and mouse (93%), induced a 5-24-fold reduction in promoter activity in HeLa, NIH3T3, CV1, and HepG2 cells. Three footprints, FP5, FP6, and FP7, were shown to map to this region. In particular, the FP7 site was found to be within the -374 to -347 bp region. Deletion of this region triggered a significant decline in promoter activity in HeLa and NIH3T3 cells but not in HepG2 cells. AP2 was found to bind FP7. In HepG2 cells AP2 elicited transactivation of the hGR promoter activity. Transfection data revealed that the upstream GC box-rich fragment between -700 and -375 bp induced a 4-7-fold activation of the heterologous tk promoter in an orientation-independent manner. Our studies demonstrate that several transcription factors are involved in regulating GR expression and that AP2 could function as an important positive regulator of GR promoter activity.

Nucleoprotein structure influences the response of the mouse mammary tumor virus promoter to activation of the cyclic AMP signalling pathway

Recent studies have provided evidence of crosstalk between steroid receptors and cyclic AMP (cAMP) signalling pathways in the regulation of gene expression. A synergism between intracellular phosphorylation inducers and either glucocorticoids or progestins has been shown to occur during activation of the mouse mammary tumor virus (MMTV) promoter. We have investigated the effect of 8-Br-cAMP and okadaic acid, modulators of cellular kinases and phosphatases, on the hormone-induced activation of the MMTV promoter in two forms: a transiently transfected template with a disorganized, accessible nucleoprotein structure and a stably replicating template with an ordered, inaccessible nucleoprotein structure. Both okadaic acid and 8-Br-cAMP synergize significantly with either glucocorticoids or progestins in activating the transiently transfected MMTV template. In contrast, 8-Br-cAMP, but not okadaic acid, is antagonistic to hormone-induced activation of the stably replicating MMTV template. Nuclear run-on experiments demonstrate that this inhibition is a transcriptional effect on both hormone-induced transcription and basal transcription. Surprisingly, 8-Br-cAMP does not inhibit glucocorticoid-induced changes in restriction enzyme access and nuclear factor 1 binding. However, association of a complex with the TATA box region is inhibited in the presence of 8-Br-cAMP. Thus, cAMP treatment interferes with the initiation process but does not inhibit interaction of the receptor with the template. Since the replicated, ordered MMTV templates and the transfected, disorganized templates show opposite responses to 8-Br-cAMP treatment, we conclude that chromatin structure can influence the response of a promoter to activation of the cAMP signalling pathway.

A set of inter-Alu PCR markers for chromosome 21 generated from pulsed-field gel-fractionated NotI restriction fragments

Genomic probes can be efficiently obtained for specific chromosomal regions by PCR amplification of gel slices containing fractionated restriction enzyme-cleaved DNA. Here, single-copy, human-specific DNA sequences were amplified using inter-Alu PCR on gel slices containing a NotI digest of DNA from hybrid cell line WAV17. Rodent cell line WAV17 contains human chromosome 21. About 75% of the 0.15- to 3-kb inter-Alu PCR products could be regionally assigned, en masse, by hybridization experiments using inter-Alu PCR probes generated from cell lines containing portions of chromosome 21. This work produced 10 new chromosome 21 markers that came from regions of 21q containing few useful markers. These markers were needed to finish a NotI restriction map for 21q (Wang and Smith (1994) Genomics 20: 441). This approach provides markers needed to close map gaps and for top-down mapping approaches.

The development of single molecule environmental sensors

The participants at the meeting reflected the broad range of expertise that is required to realize improved methods for extremely high sensitivity or single molecule detection. It is quite clear that the answers lie at the interface of biology, chemistry, engineering and molecular design.

Recombinant metallothionein-conjugated streptavidin labeled with 188Re and 99mTc

Consideration is now being given to the use of avidin (or streptavidin) and biotin for radiotherapy of tumor. Accordingly, the goal of this study was to radiolabel a mouse metallothionein-streptavidin fusion protein with 188Re and to compare its properties to those of the same fusion protein radiolabeled with 99mTc. A recombinant metallothionein-streptavidin fusion protein was radiolabeled by transchelation with 99mTc- and 188Re-glucoheptonate. Labeling efficiency, which was not optimized for either radionuclide, was approximately 60% for 99mTc and 20% for 188Re. Radiochemical purity was demonstrated by size exclusion HPLC both by nearly quantitative shifts of the 188Re label to higher molecular weight upon the addition of biotinylated antibody and by the absence of a shift with biotinsaturated 188Re-metallothionein-streptavidin. Stability of the labels in 37 degrees C serum was evaluated by comparing the HPLC radiochromatograms of serum samples both before and after the addition of biotinylated antibody. The 188Re label behaved like 99mTc in that the same peaks were evident, including one prominent peak due to labeled cysteine. Recoveries during HPLC analysis of serum samples showed that oxidation rates to perrhenate and pertechnetate were identical. However, instability to cysteine challenge was greater for 188Re; for example, the loss of label to cysteine after 24 h under one set of conditions was 41% for 188Re and 22% with 99mTc. Analysis by HPLC of liver and kidney homogenates from mice administered the labeled antibodies were qualitatively and, in large measure, quantitatively independent of label. Biodistributions at 5 h in normal mice were statistically identical between the two labels in blood and in most tissues. In conclusion, streptavidin may be radiolabeled with radiorhenium using recombinant mouse metallothionein as a bifunctional chelator, and under one set of labeling conditions at least, 188Re showed similar in vitro and in vivo behavior to that of 99mTc labeled to the same fusion protein.

Oligonucleotide-directed self-assembly of proteins: semisynthetic DNA--streptavidin hybrid molecules as connectors for the generation of macroscopic arrays and the construction of supramolecular bioconjugates

Modified biomolecules were used for the non-covalent assembly of novel bioconjugates. Hybrid molecules were synthesized from short single-stranded DNA and streptavidin by chemical methods using a heterobispecific crosslinker. The covalent attachment of an oligonucleotide moiety to streptavidin provides a specific recognition domain for a complementary nucleic acid sequence, in addition to the four native biotin-binding sites. These bispecific binding capabilities allow the hybrid molecules to serve as versatile connectors in a variety of applications. Bifunctional constructs have been prepared from two complementary hybrid molecules, each previously conjugated to biotinylated immunoglobulin G or alkaline phosphatase. The use of nucleic acid sequences as a template for the formation of an array of proteins is further demonstrated on two size scales. A macroscopic DNA array on a microtiter plate has been transformed into a comparable protein chip. A nano-scale array was made by hybridizing DNA-tagged proteins to specific positions along a RNA or DNA sequence. The generation of supramolecular bioconjugates was shown by quantitative measurements and gel-retardation assays.

Analysis of regulatory regions in the COL1A1 gene responsible for 1,25-dihydroxyvitamin D3-mediated transcriptional repression in osteoblastic cells

The synthesis of type I collagen in bone cells is inhibited by the calcium-regulating hormone 1,25-dihydroxyvitamin D3. Earlier work from our laboratories has indicated that vitamin D regulation is at the level of transcription, based on results from both nuclear run-off assays and functional promoter analysis of a hybrid gene consisting of a 3.6 kb COL1A1 promoter fragment fused to the chloramphenicol acetyltransferase reporter gene. In the present study, we investigated the molecular basis for vitamin D-mediated transcriptional repression of the COL1A1 gene and report the identification of a region within the COL1A1 upstream promoter (the HindIII-Pstl restriction fragment between nucleotides -2295 and -1670) which is necessary for 1,25-dihydroxyvitamin D3 responsiveness in osteoblastic cells. This hormone-mediated inhibitory effect on the marker gene parallels the inhibition of the endogenous collagen gene. A 41 bp fragment from this region (between nucleotides -2256 and -2216) contains a sequence which is very similar to vitamin D-responsive elements identified in the osteocalcin gene. Extracts from cultured cells which express a high level of vitamin D receptor contain a hormone:receptor complex that binds specifically to this 41 bp fragment, as demonstrated by bandshift analysis. However, deletion of this vitamin D receptor binding region from either a -3.5 kb or a -2.3 kb promoter fragment did not abolish vitamin D responsiveness. These results indicate that a vitamin D response element similar to that described for other vitamin D responsive genes (osteocalcin and osteopontin) does not alone mediate the repression of COL1A1 by 1,25-dihydroxyvitamin D3.

The initiation of neurite outgrowth by sympathetic neurons grown in vitro does not depend on assembly of microtubules

Neurite formation by dissociated chick sympathetic neurons in vitro begins when one of the many filopodia that emanate from the cell body of a neuron is invaded by cytoplasm containing microtubules and other components of axoplasm (Smith, 1994). This study was undertaken to determine whether this process depends on assembly of microtubules. To inhibit microtubule assembly, neurons were grown in medium containing nocodazole or colchicine. In one series of experiments, neurons first were exposed to the microtubule-stabilizing drug, taxol, so that existing microtubules would remain intact while assembly of new microtubules was inhibited. The ability of neurons to form neurites was assessed by time-lapse video microscopy. Neurons subsequently were stained with antibodies against the tyrosinated and acetylated forms of alpha-tubulin and examined by laser confocal microscopy to visualize microtubules. Neurons were able to form short processes despite inhibition of microtubule assembly and they did so in a way that closely resembled process formation in control medium. Processes formed by neurons that had not been pretreated with taxol were devoid of microtubules. However, microtubules were present in processes of taxol-pretreated neurons. These microtubules contained acetylated alpha-tubulin, as is typical of stable microtubules, but not tyrosinated alpha-tubulin, the form present in recently assembled microtubules. These findings show that the initial steps in neurite formation do not depend on microtubule assembly and suggest that microtubules assembled in the cell body can be translocated into developing neurites as they emerge. The results are compatible with models of neurite formation which postulate that cytoplasm from the cell body is transported into filopodia by actomyosin-based motility mechanisms.

Comparison of serum calcium levels between junior high school children with high-normal and low-normal blood pressure. The child and adolescent blood pressure program

The objective of this study was to compare serum calcium levels, dietary calcium intake, and urinary calcium excretion between junior high students with high-normal and low-normal blood pressure. The study was conducted in 11- to 14-year-old children recruited after blood pressure screening of 5th to 8th grade Minneapolis and St. Paul Public School students. Comparisons were made between a group of 243 children selected from the upper 15 percentiles of the blood pressure distribution (high-normal group) and 40 children randomly selected from the lowest 10% of the blood pressure distribution (low-normal group). Blood samples were obtained from the participants at clinic visits conducted after school. Calcium measurements were based on the principle that serum calcium is found in three forms: 1) an ionized fraction; 2) a fraction complexed with organic anions such as citrate, phosphate, and lactate; and 3) a protein-bound fraction. Dietary calcium intake was determined from food diaries, and urinary electrolytes were determined in 24-h urine collections. Serum total calcium levels were not significantly different between groups. However, serum ultrafilterable, true ionized, ionized normalized for pH, and complexed calcium levels were significantly greater in the low-normal group. There was no significant difference in 24-h intake of calcium or other nutrients between the groups. The low-normal group excreted significantly more calcium than the high-normal group, but there were no significant differences in sodium, potassium, or chloride excretion. This report of the relation between calcium and blood pressure represents the first study in children or adolescents to include serum, dietary, and urine data.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum distribution of two contraceptive progestins: 3-ketodesogestrel and gestodene

A cross-over study of two oral contraceptive formulations, containing 30 micrograms ethinylestradiol in combination with 150 micrograms desogestrel (Marvelon) or 75 micrograms gestodene (Femovan), has been performed to compare the serum distribution and pharmacokinetics of gestodene and the active metabolite of desogestrel, namely 3-ketodesogestrel. Serum concentrations of both sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) were also measured and were increased more than 3-fold and 2-fold, respectively, on day 21 of the treatment cycle, with no statistically significant difference between treatment groups. In addition, 35 days after ingestion of either oral contraceptive had ceased, the serum SHBG and CBG concentrations were similar to the pretreatment values. During treatment cycles, increased serum SHBG levels were associated with a redistribution of 3-ketodesogestrel and gestodene such that the non-protein-bound (NPB) and albumin-bound fractions were reduced in concert with an increase in the relative proportions bound to SHBG. The proportion of gestodene bound to SHBG was consistently higher than that observed for 3-ketodesogestrel, and this undoubtedly reflects the higher affinity of SHBG for gestodene (Kd = 1.2 nM at 37 degrees C) when compared to 3-ketodesogestrel (Kd = 4.7 nM at 37 degrees C). It also probably accounts, in part, for the much higher total serum levels of gestodene (8.58 nmol/L) when compared to 3-ketodesogestrel (2.37 nmol/L) during the treatment cycles. Consequently, the absolute amounts of NPB, non-SHBG-bound, and SHBG-bound gestodene are significantly higher than those measured for 3-ketodesogestrel. It is concluded that ethinylestradiol-induced increases in serum SHBG levels during treatment with Marvelon or Femovan, influenced the distribution and total amount of 3-ketodesogestrel and gestodene in serum, respectively, and that this, combined with the higher affinity of SHBG for gestodene, results in a greater amount of bioavailable gestodene compared to 3-ketodesogestrel, despite the smaller dose of gestodene administered.

Clinical and medicoeconomic impact of the cyclosporine-diltiazem interaction in renal transplant recipients

The effect of the diltiazem-cyclosporine interaction on cyclosporine pharmacokinetics, pharmacodynamics, and pharmacoeconomics was studied in 10 recipients of renal allografts. Each subject was studied while receiving diltiazem 60 mg twice/day and while not taking the drug. After achieving steady-state conditions, cyclosporine and metabolite concentrations were determined in whole blood from samples drawn after the morning cyclosporine dose. After pharmacokinetic analysis, all patients were followed for 6 months during treatment with cyclosporine plus diltiazem or cyclosporine alone. Cyclosporine blood clearance decreased significantly after treatment with diltiazem (18.0-11.0 ml/min.kg; p = 0.008). The apparent volume of cyclosporine distribution also decreased significantly (4.26-2.62 L/kg; p < 0.05). After 6 months, diltiazem had no effect on renal function indexes, and no apparent effect on immunosuppression. Alterations in cyclosporine clearance and apparent volume of distribution secondary to diltiazem result in dosage reduction and potential cost savings in transplant pharmacotherapy. The mean decrease in cyclosporine dosage requirements would produce a cost saving of $1520 or 28% per patient per year.

Pioglitazone promotes insulin-induced activation of phosphoinositide 3-kinase in 3T3-L1 adipocytes by inhibiting a negative control mechanism

Activation of phosphoinositide 3-kinase (PI 3-kinase) is an early event in insulin signal transduction that is blocked completely in adipocytes from insulin-resistant KKAy mice. Treatment of KKAy mice with pioglitazone, an anti-diabetic thiazolidinedione, partially restores insulin-dependent changes in PI 3-kinase. The mechanism of this effect of pioglitazone was investigated using murine 3T3-L1 cells as an experimental model. Insulin and insulin-like growth factor I (IGF-I) each elicited rapid (within 2 min) and large (2-5-fold) increases in PI 3-kinase activity that could be immunoprecipitated using anti-phosphotyrosine (pY) antibodies. Maximal insulin-induced activity of PI 3-kinase in pY-immunoprecipitates was similar in 3T3-L1 adipocytes and mouse adipocytes, but the kinetics of activation differed. Insulin- and IGF-I-induced changes in PI 3-kinase were each half-maximal at 3-5 nM of hormone and were not additive. Increases in both insulin-induced and IGF-I-induced pY-immunoprecipitable PI 3-kinase activity were observed when 3T3-L1 fibroblasts became confluent and when they adopted the adipocyte phenotype. Pioglitazone (10 microM), administered either acutely or chronically to either 3T3-L1 adipocytes or 3T3-L1 fibroblasts, did not greatly alter the kinetics, magnitude or sensitivity of changes in PI 3-kinase elicited by either insulin or IGF-I. In contrast, the attenuation by isoproterenol of insulin-induced changes in PI 3-kinase was prevented in cells pretreated with pioglitazone. This effect of pioglitazone did not involve inhibition of isoproterenol-elicited accumulation of cyclic AMP. Pioglitazone also prevented attenuation of insulin induced changes in PI 3-kinase by cell penetrating analogs of cyclic AMP. Pioglitazone, therefore, has no direct effect on insulin-stimulated PI 3-kinase activity, but interferes with a cyclic AMP-dependent mechanism that normally antagonizes this action of insulin. These data support the proposition that the facilitation of insulin action by pioglitazone involves, at least in part, an inhibition of a negative control mechanism.

Pioglitazone promotes insulin-induced activation of phosphoinositide 3-kinase in 3T3-L1 adipocytes by inhibiting a negative control mechanism

Activation of phosphoinositide 3-kinase (PI 3-kinase) is an early event in insulin signal transduction that is blocked completely in adipocytes from insulin-resistant KKAy mice. Treatment of KKAy mice with pioglitazone, an anti-diabetic thiazolidinedione, partially restores insulin-dependent changes in PI 3-kinase. The mechanism of this effect of pioglitazone was investigated, using murine 3T3-L1 cells as an experimental model. Insulin and insulin-like growth factor I (IGF-I) each elicited rapid (within 2 min) and large (2- to 5-fold) increases in PI 3-kinase activity that could be immunoprecipitated using anti-phosphotyrosine (pY) antibodies. Maximal insulin-induced activity of PI 3-kinase in pY-immunoprecipitates was similar in 3T3-L1 adipocytes and mouse adipocytes, but the kinetics of activation differed. Insulin- and IGF-I-induced changes in PI 3-kinase were each half-maximal at 3-5 nM of hormone and were not additive. Increases in both insulin-induced and IGF-I-induced pY-immunoprecipitable PI 3-kinase activity were observed when 3T3-L1 fibroblasts became confluent and when they adopted the adipocyte phenotype. Pioglitazone (10 microM), administered either acutely or chronically to either 3T3-L1 adipocytes or 3T3-L1 fibroblasts, did not alter greatly the kinetics, magnitude or sensitivity of changes in PI 3-kinase elicited by either insulin or IGF-I. In contrast, the attenuation by isoproterenol of insulin-induced changes in PI 3-kinase was prevented in cells pretreated with pioglitazone. This effect of pioglitazone did not involve inhibition of isoproterenol-elicited accumulation of cyclic AMP. Pioglitazone also prevented attenuation of insulin induced changes in PI 3-kinase by cell penetrating analogs of cyclic AMP. Pioglitazone, therefore, has no direct effect on insulin-stimulated PI 3-kinase activity, but interferes with a cyclic AMP-dependent mechanism that normally antagonizes this action of insulin. These data support the proposition that the facilitation of insulin action by pioglitazone involves, at least in part, an inhibition of a negative control mechanism.

Anti-neutrophil cytoplasmic antibodies (ANCA) in myelodysplasia and other haematological disorders

BACKGROUND

Anti-neutrophil cytoplasmic antibodies (ANCA) are typically associated with small vessel vasculitides. They are also found in situations where other autoantibodies are common, sometimes after infections and possibly in individuals who have received multiple blood transfusions.

AIMS

The aim of this study was to determine the incidence of ANCA in a variety of haematological disorders, where these predisposing factors may be at work.

METHODS

Sera from patients with myelodysplasia (n = 26), acute myeloid leukaemia (AML) (n = 3), and myeloproliferative (n = 25) or lymphoproliferative syndromes (n = 16) were screened for ANCA using a crude neutrophil cytoplasmic extract ELISA and indirect immunofluorescent examination of normal peripheral blood neutrophils. Positive results were confirmed by ELISAs for anti-proteinase 3, anti-myeloperoxidase or anti-elastase antibodies.

RESULTS

ANCA were demonstrated in two patients with myelodysplasia, both with chronic myelomonocytic leukaemia and greater than 5% blasts in the bone marrow. Both of these individuals were infected at the time that ANCA were demonstrated and other autoantibodies were present. One of these individuals had never had evidence of any vasculitis; the other probably developed myelodysplasia after treatment with cyclophosphamide for Wegener's granulomatosis. ANCA were demonstrated in one individual with AML secondary to myelodysplasia. ANCA were also found in a patient with lymphoma in whom autoantibodies against red cells and platelets were already noted. ANCA were demonstrated in one further individual with lymphomatoid granulomatosis, a condition that resembles Wegener's granulomatosis clinically and histologically, but which is treated as a lymphoma. No ANCA were present in any of the patients with myeloproliferative syndromes.

DISCUSSION

ANCA probably occur secondary to immune dysregulation in myelodysplasia and the lymphoproliferative conditions and they are not necessarily associated with the presence of a vasculitis.

Top-down construction of an ordered Schizosaccharomyces pombe cosmid library

A very rapid and efficient method for sorting and ordering large numbers of clones is presented. This top-down mapping approach divides the entire ordering problem into many smaller tasks and analyzes in parallel a gridded membrane array of clones by hybridization with probe pools. The strategy was tested on a 15-fold-coverage Schizosaccharomyces pombe cosmid library. About 1600 clones were assigned to chromosomes and to regions defined by the Not I and Sfi I restriction maps. Then, the clones were ordered into 20 contigs, which is consistent with statistical expectations for the degree of genome coverage used. The parallel ordering of clones and the computer-based analysis of digitized images make this approach very efficient; it is about 8-fold faster than existing methods. Only 61 hybridizations were needed to order 1600 clones.

Enhanced DNA sequencing by hybridization

An enhanced version of DNA sequencing by hybridization (SBH), termed positional SBH (PSBH), has been developed. PSBH uses duplex probes containing single-stranded 3' overhangs, instead of simple single-stranded probes. Stacking interactions between the duplex probe and a single-stranded target should provide enhanced stringency in distinguishing perfectly matched 3' sequences. A second enhancement is the use of enzyme-catalyzed steps, instead of pure physical hybridization. The feasibility of this scheme has been investigated using biotinylated duplex probes containing single-stranded 5-base 3' overhangs, immobilized on streptavidin-coated magnetic beads. Ligation of a single-stranded target, hybridized to the single-stranded region of the duplex probes, provided enhanced discrimination of perfectly matched targets from those containing mismatches. In distinction to the serious complications caused by base composition effects in ordinary SBH, there was little effect of base composition in PSBH. The hardest mismatch to discriminate was the one furthest from the phosphodiester bond formed by ligation. However, mismatches in this position were efficiently discriminated by 3' extension of the duplex probe using a template-dependent DNA polymerase. These results demonstrate that PSBH offers considerable promise to facilitate actual implementations of SBH.

Ventralizing signal determined by protease activation in Drosophila embryogenesis

Specification of dorsal-ventral cell fate during Drosophila embryogenesis is mediated by a signal transduction pathway. Asymmetry of cell fates arises through the spatially restricted production of a ligand in an extracellular compartment called the perivitelline space. The snake and easter genes are required for the production of the ligand and they encode the proenzyme form of secreted extracellular serine proteases. We have examined the effect of producing a preactivated form of the snake protease on the generation of dorsal-ventral polarity. SP6 RNA microinjection experiments reveal that different cell fates acquired at cellular blastoderm can be specified by the amount and spatial distribution of activated snake protein. Our results support a protease cascade model in which localized activation of uniformly distributed protease proenzymes leads to the spatially restricted production of ligand in the perivitelline space on the ventral side of the embryo.

Large-scale structure conservation along the entire long arm of human chromosome 21

Complete, contiguous NotI restriction maps were constructed for the long arm of human chromosome 21 contained in nine different cell lines. These maps span about 43 Mb and consist of about 60 distinct NotI fragments, about 80 markers, and 11 chromosomal breakpoints. Although some differences among the maps were noted, the overall large-scale structure of the chromosomes is remarkably similar, which strongly validates the use of cell lines for mapping studies. Remarkably few serious discrepancies were found between the order of markers on this NotI restriction map and various genetic and physical maps. However, when compared with the NotI physical map, both the genetic map and the radiation hybrid map of chromosome 21 appear to expanded near the centromere and especially near the telomere.

Squirrel monkey corticosteroid-binding globulin: primary structure and comparison with the human protein

Squirrel monkey (Saimiri sciureus) corticosteroid-binding globulin (CBG) is the product of a 1.6-kilobase mRNA in the liver. Analyses of two overlapping cDNAs revealed that the squirrel monkey CBG precursor comprises 406 amino acids, the first 22 residues of which exhibit 91% identity with the human CBG leader sequence. The mature form of squirrel monkey CBG, therefore, very likely comprises 384 amino acids and has a polypeptide mol wt of 42,854. Compared to human CBG, the squirrel monkey protein contains an additional residue (threonine) at position 144, and the two proteins exhibit 86% sequence identity if this is taken into account. Squirrel monkey CBG contains five consensus sites for N-glycosylation, four of which are located in analogous positions in human CBG, and has two cysteine residues in the same relative positions as the cysteines in human CBG. Unlike CBG in most other species, squirrel monkey CBG appears to circulate as a dimer, and its affinity for glucocorticoids is remarkably low. We, therefore, expressed cDNAs for human and squirrel monkey CBGs in Chinese hamster ovary (CHO) cells and compared the physico-chemical properties of the products with those of the corresponding serum proteins. Squirrel monkey CBG is produced by CHO cells as a dimer, and its subunit size heterogeneity is similar to that associated with CBG in serum. In addition, the cortisol-binding affinity of squirrel monkey CBG produced by CHO cells is similar to that of the natural protein and is 5- to 8-fold lower than that of natural or recombinant human CBG. Mutants in which a threonine at position 144 was either added to human CBG or subtracted from squirrel monkey CBG were also expressed in CHO cells. This demonstrated that this additional amino acid in the squirrel monkey CBG sequence may actively contribute to its propensity for spontaneous dimerization, but does not account for its relatively low steroid-binding affinity.

Reproduction in llamas and alpacas: A review

In this review we attempt to compile and summarize the diverse and often contradictory material presented on the reproduction of llamas and alpacas (hereafter referred to as lamoids). Lamoids have recently gained international popularity, and theriogenologists are often asked to intervene in clinical management of reproductive problems of these animals. We therefore present a discussion of the reproductive anatomy, physiology, and behavior of llamas as well as the follicular dynamics as observed with ultrasonography. The nonsurgical embryo transfer procedure and the nutrient requirements of llamas are also discussed.