Mosaic trisomy 16 ascertained through amniocentesis: evaluation of 11 new cases

Trisomy 16, once thought to result uniformly in early pregnancy loss, has been detected in chorionic villus samples (CVS) from on-going pregnancies and was initially ascribed to a second, nonviable pregnancy. Prenatally detected trisomy 16 in CVS and its resolution to disomy has led to the reexamination of the viability of trisomy 16. This study evaluates 11 cases of mosaic trisomy 16 detected through second trimester amniocentesis. In 9 of the 11 cases, amniocenteses were performed in women under the age of 35 because of abnormal levels of maternal serum alpha-fetoprotein (MSAFP) or maternal serum human chorionic gonadotropin (MShCG). The other two amniocenteses were performed for advanced maternal age. Five of the 11 pregnancies resulted in liveborn infants, and six pregnancies were electively terminated. The liveborn infants all had some combination of intrauterine growth retardation (IUGR), congenital heart defects (CHD), or minor anomalies. Two of them died neonatally because of complications of severe congenital heart defects. The three surviving children have variable growth retardation, developmental delay, congenital anomalies, and/or minor anomalies. In the terminated pregnancies, the four fetuses evaluated by ultrasound or autopsy demonstrated various congenital anomalies and/or IUGR. Cytogenetic and fluorescent in situ hybridization studies identified true mosaicism in 5 of 10 cases examined, although the abnormal cell line was never seen in more than 1% of cultured lymphocytes. Placental mosaicism was seen in all placentas examined and was associated with IUGR in four of seven cases. Maternal uniparental disomy was identified in three cases. Mosaic trisomy 16 detected through amniocentesis is not a benign finding but associated with a high risk of abnormal outcome, most commonly IUGR, CHD, developmental delay, and minor anomalies. The various outcomes may reflect the diversity of mechanisms involved in the resolution of this abnormality. As 80% of these patients were ascertained because of the presence of abnormal levels of MSAFP or MShCG, the increased use of maternal serum screening should bring more such cases to clinical attention.

Centromeric DNA break in a 10;16 reciprocal translocation associated with trisomy 16 confined placental mosaicism and maternal uniparental disomy for chromosome 16

Stable centromeric breakage in non-acrocentric chromosomes and balanced reciprocal translocation mosaicism are both rare events. We studied a family in which the mother had mosaicism for a balanced reciprocal translocation between chromosomes 10 and 16 which was associated with a break in chromosome 16 centromere alpha-satellite DNA ¿146,XX,t(10;16)(q11.2;q11.1) [29]/46,XX[25]¿. The derivative chromosome 16 contained only a very small amount of 16 alpha-satellite DNA while the derivative 10 contained all of the 10 alpha-satellite DNA as well as a large amount of the 16 alpha-satellite DNA. The same translocation was present in all cells in her son who was found prenatally to have trisomy 16 mosaicism ¿46,XY,t(10;16) (q11.2;q11.1)mat[22]/47,idem,+16[4]¿. Trisomy 16 cells were subsequently determined to be confined to the placenta. DNA polymorphism analyses in the family demonstrated maternal uniparental disomy for chromosome 16 in the diploid child. The child, at age 7 months, had minor facial anomalies similar to a previously reported case of maternal uniparental disomy for chromosome 16. In addition to illustrating several rare events, this family further demonstrated that substantial deletion of the centromeric alpha-satellite DNA does not impair centromere function and both mitotic and meiotic stability are retained in such cases.

Dural tears secondary to operations on the lumbar spine. Management and results after a two-year-minimum follow-up of eighty-eight patients

We reviewed the results of acute management of patients who had sustained a dural tear during an operation on the lumbar spine, and we attempted to determine the long-term sequelae of this complication. In the five years from July 1989 to July 1994, 641 consecutive patients had a decompression of the lumbar spine, performed by the senior one of us; of these patients, eighty-eight (14 percent) sustained a dural tear, which was repaired during the operation. The duration of follow-up ranged from two to eight years (average, 4.3 years). Postoperative management consisted of closed suction wound drainage for an average of 2.1 days and bed rest for an average of 2.9 days. Of the eighty-eight procedures that resulted in a dural tear, forty-five were revisions; these revisions were performed after an average of 2.2 previous operations on the lumbar spine, all of which resulted in a scar adherent to the dura. Only eight patients had headaches related to the spinal procedure and photophobia in the postoperative period; these symptoms resolved in all but two patients, both of whom had had a revision operation. Each of the two patients had symptoms of a persistent leak of spinal fluid and needed a reoperation for repair. Overall, seventy-six patients had a good or excellent result and twelve had a poor or satisfactory result with some residual back pain. One patient had arachnoiditis, and another had symptoms of viral meningitis one month postoperatively. A dural tear that occurs during an operation on the lumbar spine can be treated successfully with primary repair followed by bed rest. Such a tear does not appear to have any long-term deleterious effects or to increase the risk of postoperative infection, neural damage, or arachnoiditis. Closed suction wound drainage does not seem to aggravate the leak and can be used safely in the presence of a dural repair.

Reconstitution of DNA topoisomerase VI of the thermophilic archaeon Sulfolobus shibatae from subunits separately overexpressed in Escherichia coli

DNA topoisomerase VI from the hyperthermophilic archaeon Sulfolobus shibatae is the prototype of a novel family of type II DNA topoisomerases that share little sequence similarity with other type II enzymes, including bacterial and eukaryal type II DNA topoisomerases and archaeal DNA gyrases. DNA topoisomerase VI relaxes both negatively and positively supercoiled DNA in the presence of ATP and has no DNA supercoiling activity. The native enzyme is a heterotetramer composed of two subunits, A and B, with apparent molecular masses of 47 and 60 kDa, respectively. Here wereport the overexpression in Escherichia coli and the purification of each subunit. The A subunit exhibits clusters of arginines encoded by rare codons in E.coli . The expression of this protein thus requires the co-expression of the minor E.coli arginyl tRNA which reads AGG and AGA codons. The A subunit expressed in E.coli was obtained from inclusion bodies after denaturation and renaturation. The B subunit was overexpressed in E.coli and purified in soluble form. When purified B subunit was added to the renatured A subunit, ATP-dependent relaxation and decatenation activities of the hyperthermophilic DNA topoisomerase were reconstituted. The reconstituted recombinant enzyme exhibits a specific activity similar to the enzyme purified from S.shibatae . It catalyzes transient double-strand cleavage of DNA and becomes covalently attached to the ends of the cleaved DNA. This cleavage is detected only in the presence of both subunits and in the presence of ATP or its non-hydrolyzable analog AMPPNP.

A biomechanical evaluation of graft loading characteristics for anterior cervical discectomy and fusion. A comparison of traditional and reverse grafting techniques

STUDY DESIGN

A biomechanical study of graft loading characteristics for anterior cervical discectomy and fusion comparing the amount and location of transmitted forces.

OBJECTIVES

To evaluate the difference between traditional iliac grafting and reverse iliac grafting used for anterior cervical discectomy and fusion in the amount and location of forces applied to the grafts.

SUMMARY OF BACKGROUND DATA

Traditional fusion after anterior cervical discectomy involves placing a tricortical iliac crest strut into the disc space with the cortical portion facing anteriorly and the cancellous portion posteriorly. Recently, reverse iliac grafting has been introduced in which the cortical portion is placed in the posterior disc space and the cancellous portion in the anterior disc space. There is no biomechanical or clinical study showing an advantage of using one technique over the other. This study is the first to produce data supporting one technique as biomechanically superior.

METHODS

Five fresh cadaveric cervical spines were tested using pressure-sensitive film placed between the bone graft and the vertebral endplate after an anterior discectomy was performed. A 10-pound load was applied to the cervical spine at predetermined sagittal positions. Recordings were made at neutral, 10 degrees of flexion, and 10 degrees and 20 degrees of extension after traditional and reverse iliac grafting.

RESULTS

Graft forces were identical in both traditional and reverse grafting in the location and amount of force applied. Total force increased to the maximum in flexion and gradually decreased in more extended positions. The location of the forces was completely anterior with flexion, moving to the posterior portion of the graft with positions of extension. With 10 degrees of flexion, the load applied to the grafts was 20.4 N. In the neutral position, the load was 12 N. The loads decreased further with extension with forces of 11 N in 10 degrees extension, and 4 N in 20 degrees of extension.

CONCLUSIONS

The optimal position of the tricortical iliac graft for an anterior cervical fusion is with the stronger cortical portion placed in the anterior disc space and the weaker cancellous portion placed in the posterior disc space. In this traditional position, the graft will best resist the loads applied to the cervical spine, preventing graft collapse.

Differences among geriatricians, general internists, and cardiologists in the care of patients with heart failure: a cautionary tale of quality assessment

OBJECTIVES

To describe differences in the characteristics, processes of care, and resource utilization of patients with heart failure cared for by geriatricians, general internists, cardiologists, and combinations of physicians.

DESIGN

A retrospective cohort study.

SETTING

An urban academic medical center.

PARTICIPANTS

A total of 439 outpatients with a billing diagnosis of heart failure or cardiomyopathy who were treated by geriatricians, general internists, cardiologists, and combinations of physicians.

MEASUREMENTS

Demographic and clinical characteristics, medication use, diagnostic testing, hospitalizations, and inpatient and outpatient costs were measured.

RESULTS

Compared with patients of cardiologists, patients cared for by geriatricians were older, more likely to have hypertension, diastolic dysfunction, and high comorbidity, and less likely to undergo echocardiography, cardiac catheterization, and electrocardiography. Use of angiotensin-converting enzyme inhibitors was similar among patients with reduced systolic function. Patients cared for by geriatricians had the same costs, rates of hospitalization, and likelihood of being symptomatic as patients of cardiologists.

CONCLUSIONS

The processes of care for patients with heart failure seen solely by geriatricians differ from those for patients seen by other physicians, but the case-mix also varies. Assessment of left ventricular function by geriatricians probably needs to be increased. However, although they were older and had more comorbidity, patients of geriatricians had total costs and symptomatology similar to those of patients of cardiologists. Future work is needed to identify those patients most likely to benefit from treatment by geriatricians and to determine how care can be optimally coordinated among different types of physicians and health providers.

Structural requirements of the glucocorticoid and retinoic acid response units in the phosphoenolpyruvate carboxykinase gene promoter

The phosphoenolpyruvate carboxykinase (PEPCK) gene promoter contains a glucocorticoid response unit (GRU) that includes three accessory factor-binding sites (AF1, AF2, and AF3), two glucocorticoid receptor-binding sites (GR1 and GR2), and a cAMP response element. All of these elements, and the proteins that bind to them, are required for a complete glucocorticoid response. The PEPCK promoter also contains a retinoic acid response unit (RARU) that consists of two retinoic acid response elements (RARE1 and RARE2) that bind retinoic acid receptor/9-cis-retinoic acid receptor heterodimers. The sequences of RARE1 and RARE2 coincide with those for AF1 and AF3, respectively. Thus, the PEPCK promoter can mediate different hormone responses through hormone response units that utilize common elements, but that bind different sets of proteins. We reasoned that each response might require a unique structural assembly and therefore tested how various arrangements of the PEPCK promoter affect the actions of either glucocorticoids or retinoic acid. The activation of the PEPCK gene in response to glucocorticoids requires a specific set of cis-acting elements that must be precisely positioned within the GRU. The distance between AF2 and GR1 is critical for the glucocorticoid response, and since the AF2 factor, HNF3, interacts with GR in vitro, this protein-protein interaction may be important for the glucocorticoid response. By contrast, the distance and orientation requirements of AF1 and AF3 with respect to GR1 are more flexible. In the case of the RARU, although the relative positions of RARE1 and RARE2 are important for the retinoic acid response, more tolerance for distance and stereospecific alignment between RARE1 and RARE2 is allowed. In addition, we show that the GRU and the RARU can act as a module, within a restricted region, in the context of the PEPCK promoter and in limited contexts of a heterologous promoter. These observations suggest that the structural requirements of the GRU and the RARU are different, and this may have important implications for how multiple hormonal signals are integrated through this promoter.

Use of Fourier transform infrared (FTIR) spectroscopy to follow the adsorption of heptane and 1,4-dioxane vapors on a zinc oxide surface

Vapor adsorption isotherms of two nonpolar model compounds, heptane and 1,4-dioxane, were determined for a very small particle size zinc oxide (ZnO) powder (median particle size approximately 23 nm) in the lower relative vapor pressure (P/Po) region. The ZnO samples for all adsorption measurements were dried at 400 degrees C for 4 h. A new method, which employed an FTIR spectrometer with a long path gas cell (IR path length of 3.0 m), was developed for the organic vapor adsorption measurements. The amount adsorbed was determined by mass balance. This method allows accurate quantification of organic vapors and is sensitive to very low P/Po values. The heptane and 1, 4-dioxane vapor adsorption isotherms appeared to exhibit the expected Type II behavior. The surface areas obtained for ZnO from BET analyses of the heptane and 1,4-dioxane vapor adsorption isotherms (36.9 and 30.3 m2/g) compared reasonably well to the surface area obtained from BET analysis of the nitrogen vapor adsorption isotherm (32.6 m2/g). The amount of vapor adsorbed by ZnO at P/Po equal to 0.1, in terms of number of moles, was observed to decrease in the order: water10 >> 1,4-dioxane > heptane. It was inferred that, while heptane was only adsorbed via a dipole-induced dipole interaction, 1,4-dioxane was physically adsorbed via an interaction dominated by the oxygen lone-pair orbital. Presumably, this interaction was more comparable to a weak dipole-dipole interaction. These results are consistent with the expected strengths of interaction.

Identification of active site residues in the "GyrA" half of yeast DNA topoisomerase II

Site-directed mutagenesis was carried out at 10 highly conserved polar residues within the C-terminal half of yeast DNA topoisomerase II, which corresponds to the A subunit of bacterial DNA gyrase, to identify amino acid side chains that augment the active site tyrosine Tyr-782 in the breakage and rejoining of DNA strands. Complementation tests show that alanine substitution at Arg-690, Asp-697, Lys-700, Arg-704, or Arg-781, but not at His-735, His-736, Glu-738, Gln-750, or Asn-828, inactivates the enzyme in vivo. Measurements of DNA relaxation and cleavage by purified mutant enzymes show that these activities are abolished in the R690A mutant and are much reduced in the mutants D697A, K700A, R704A, and R781A. When a Y782F polypeptide with a phenylalanine substituting for the active site tyrosine was expressed in cells that also express the R690A polypeptide, the resulting heterodimeric yeast DNA topoisomerase II was found to nick plasmid DNA. Thus in a dimeric wild-type enzyme, Tyr-782 in one protomer and Arg-690 in the other cooperate in trans in the catalysis of DNA cleavage. For the residues D697A, K700A, R704A, and R781A, their locations in the crystal structures of type II DNA topoisomerase fragments suggest that Arg-781 and Lys-700 might be involved in anchoring the 5' and 3' sides of the broken DNA, respectively, and the roles of Asp-697 and Arg-704 are probably less direct.

A comparison of magnetic resonance and computed tomographic image quality after the implantation of tantalum and titanium spinal instrumentation

STUDY DESIGN

Tantalum- and titanium-based lumbar interbody fusion devices were implanted into two fresh human cadavers, and magnetic resonance and computed tomographic imaging were performed to evaluate adjacent spinal structures and the amount of metallic artifact.

OBJECTIVE

The objective of this study was to prospectively compare the preliminary results of magnetic resonance imaging and computed tomography scanning image quality after the implantation of both titanium and tantalum spinal implants.

SUMMARY OF BACKGROUND DATA

The availability of tantalum and titanium spinal implants brings theoretical magnetic resonance imaging compatibility along with several other desirable characteristics. The magnetic resonance imaging and computed tomographic imaging of tantalum spinal instrumentation has never been studied previously or compared with titanium instrumentation.

METHODS

Titanium and tantalum spinal implants produced for anterior spinal fusion were each placed at two levels in the lumbar spine of two fresh cadaver specimens. Sequential spin echo T1-weighted and T2-weighted magnetic resonance imaging studies and computed tomographic scans were obtained. The resulting images were then graded to describe and compare the behavior of tantalum metal in magnetic resonance imaging and computed tomographic studies.

RESULTS

Good T1 and T2 images were obtained that allowed visualization of the neural structures with minimal artifact. The optimal T1 images for tantalum metal were similar in quality to the optimal T1 parameters for titanium metal. T2 images for both tantalum and titanium metal were obtained with similar results for both metals. Gradient echo magnetic resonance imaging scans of both were poorly imaged with a large amount of artifact. Computed tomographic studies of tantalum implants produced a large amount of metal artifact when compared with computed tomographic studies of titanium implants.

CONCLUSIONS

High-quality magnetic resonance imaging studies can be obtained after the implantation of both titanium and tantalum spinal instrumentation. Both of the metals produce similar images on magnetic resonance imaging studies with comparable amounts of metallic artifact. High-quality computed tomographic scans of titanium implants can be obtained with minimal distortion secondary to artifact. However, computed tomographic scanning is not the imaging modality of choice for the tantalum spinal implants because of the large amounts of artifact.

Structure, tumorigenicity, microsomal metabolism, and DNA binding of 7-Nitrodibenz[a,h]anthracene

It has been previously proposed that a nitropolycyclic aromatic hydrocarbon (nitro-PAH) with its nitro functional group perpendicular or nearly perpendicular to the aromatic moiety exhibits lower tumorigenicity than the corresponding parent aromatic hydrocarbon. We also hypothesized that reduction of the nitro group is not involved, or contributed less significantly in the metabolic activation of this class of nitro-PAHs. To verify this hypothesis, we selected 7-nitrodibenz[a,h]anthracene (7-NDB[a,h]A) for study. The X-ray crystallographic structure of 7-NDB[a,h]A was determined and indicated that the dihedral angle between the nitro functional group and the aromatic dibenz[a,h]anthracenyl moiety was 80.6 degrees, indicating the nitro group preferentially adopts a nearly perpendicular orientation. The tumorigenicity of 7-NDB[a,h]A and dibenz[a,h]anthracene (DB[a,h]A) was determined in the male B6C3F1 neonatal mouse. Mice were administered ip injections of 1/7, 2/7, and 4/7 of the total dose of 7-NDB[a,h]A (400 nmol in 35 microL of DMSO per mouse) within 24 h of birth and at 8 and 15 days of age, respectively, and sacrificed at 12 months of age. DB[a,h]A induced 78 and 96% hepatocellular adenomas and carcinomas, respectively. However, 7-NDB[a,h]A induced only 50 and 8% hepatocellular adenomas and carcinomas compared with the 8 and 4% hepatocellular adenomas and carcinomas induced by the solvent vehicle, DMSO. Aerobic metabolism of 7-NDB[a,h]A by liver microsomes of 15-day old male B6C3F1 neonatal mice resulted in trans-3,4-dihydroxy-3, 4-dihydro-7-nitrodibenz[a,h]anthracene (7-NDB[a,h]A trans-3, 4-dihydrodiol) and trans-10,11-dihydroxy-10, 11-dihydro-7-nitrodibenz[a,h]anthracene (7-NDB[a,h]A trans-10, 11-dihydrodiol) as predominant metabolites. Under anaerobic conditions, 7-NDB[a,h]A was not metabolized (nitroreduced). The DNA adduct levels in liver and lung tissues of male B6C3F1 mice treated with 7-NDB[a,h]A and sacrificed 24 h and 6 days after final dosing were determined by 32P-postlabeling/TLC. In all cases, the DNA adducts derived from 7-NDB[a,h]A trans-3,4-dihydrodiol and 7-NDB[a, h]A trans-10,11-dihydrodiol were formed. These results suggest that both of the metabolites, 7-NDB[a,h]A trans-3,4-dihydrodiol and 7-NDB[a,h]A trans-10,11-dihydrodiol, are involved in the metabolic activation of 7-NDB[a,h]A, leading to tumor induction in the neonatal mouse. Thus, our results described in this paper support our hypotheses that a nitro-PAH with a perpendicular nitro orientation exhibits lower tumorigenicity than the corresponding parent PAH and that nitroreduction contributes less significantly in the metabolic activation.

Structural similarities between topoisomerases that cleave one or both DNA strands

Type IA and type II DNA topoisomerases are distinguished by their ability to cleave one or two strands, respectively, of a DNA duplex. Both types have been proposed to use an "enzyme-bridging" mechanism, in which a break is formed in a DNA strand and a gap is opened between the broken pieces to allow passage of a second DNA strand or duplex segment. Although the type IA and type II topoisomerase structures appear overall quite different from one another, unexpected similarities between several structural elements suggest that members of the two subfamilies may use comparable mechanisms to bind and cleave DNA.

Performances of mesophilic anaerobic digestion systems treating poultry mortalities

A closed-loop anaerobic digestion system consisting of a leachbed (LB) and an upflow anaerobic sludge blanket (UASB) was tested as an alternative for the disposal of poultry mortalities. This paper compares the performances of three LB-UASB treatment systems with different initial moisture contents in the LBs. Each LB was loaded with one chicken and 5, 10 or 18 liters of water. The LBs initially carried out he hydrolysis/acidification phase while the UASBs the methanogenesis phase. Due to repeated inoculation by the UASBs, the LBs with 10 and 18 liters of water started producing methane on day 5, while the one with 5 liters of water on day 19. However, methane production rates were low before day 40 for the LB with 10 liters of water and day 60 for the other LBs. Methane production gradually improved as the LBs continued to receive ungranulated sludge from the UASBs. The LBs eventually became balanced methane reactors. Continued balanced fermentation in the LBs resulted in leachates with very low substrate concentrations that could no longer support high-rate methanogenesis in the UASBs. Consequently, methane production rates from the UASBs decreased quickly while that from the LBs reached peak levels. Cumulative methane production from each LB eventually exceeded that from its connecting UASB. After 118 days of digestion, 414, 437 and 470 liters of methane were produced from the three systems, respectively. Cumulative methane production from the LBs with 5 and 18 liters of water accounted for 63% of the total methane produced from their respective systems. The LB with 10 liters of water produced 75% of the total methane from that system. Methane yields ranged from 0.485 to 0.554 m3 (Kg TS)-1. About 86% of the initial dry weight was biodegraded. All three systems performed very well with little operational problems. Overall, the systems that started with 10 liters of water in the LB performed the best. Strategy for enhancing system performances and implementing farm applications are discussed.

N-RAS oncogene mutations in patients with agnogenic myeloid metaplasia in leukemic transformation

From 5% to 20% of patients with agnogenic myeloid metaplasia (AMM) will evolve into a terminal leukemic phase; N-RAS gene mutations are the most common gene abnormalities detected in patients with leukemia. The present study was designed to see if N-RAS gene mutations are associated with the leukemic transformation in AMM. Over a 9 year period, in a single institution, 43 patients with AMM were studied. Of these, ten patients were found to be in leukemic phase. The results showed that none of the patients in chronic phase (40 patients) had N-RAS gene mutations, while two patients in leukemic phase showed this gene mutation. One patient was found to have a codon 12 mutation with arginine substituting for glycine (GGT-->CGT); the other was a codon 12 mutation with glutamine substituting for glycine (GGT-->GAT). The present study suggests that N-RAS mutations are rare events in the chronic phase of AMM, and are only occasionally found when patients have evolved into leukemic transformation. Further studies to search for other gene abnormalities in AMM may be warranted.

Self-association of G-rich oligodeoxyribonucleotides under conditions promoting purine-motif triplex formation

Efficient purine-motif triple-helix formation with guanosine/thymidine-rich oligodeoxyribonucleotides requires the presence of divalent cations (e.g., Mg2+) or polyamines at physiologic concentrations. However, under such conditions, we found that G-rich oligonucleotides were capable of self-association. Mixing experiments indicated a stoichiometry of two G-rich oligonucleotide strands in each complex. Dimerization was proportional to the oligonucleotide length, facilitated by increasing concentrations of multivalent cations, and inhibited by monovalent cations that promote G-quartet formation (e.g., K+, Rb+ NH4+). Although dimer formation was relatively slow (t(1/2) approximately 20 minutes), these species were quite stable, with dissociation rates on the order of days. Methylation protection experiments indicated that these dimers exhibited protected N7 position on most all guanines consistent with Hoogsteen base pairing, although this pattern differed from that observed under conditions favoring intramolecular quadruplex formation. Most important, G-rich oligonucleotide dimers were less capable of purine-motif triplex formation than were their denatured counterparts. Thus, these data indicated that G-rich oligodeoxyribonucleotides can form alternate self-associated structures under conditions that do not favor standard quadruplex formation and that these species can have altered properties with regard to their recognition of biologic targets.

Lyme disease spirochetes in ticks from northeastern China

During May 1996, field surveys on Lyme disease spirochetes were conducted in Beijing, Shenyang, Fushun, and Inner Mongolia in northeastern China. The ticks collected consisted of 3 genera and 12 species. Of these, Ixodes persulcatus was dominant in sun-exposed vegetation in forests in Inner Mongolia; 57 Borrelia strains (55/123 unfed adults and 2/5 immature stages fed on a rodent) were obtained from this tick by BSK culture. Additionally, 2/2 Apodemus peninsulae were positive. Ixodes nipponensis, Ixodes pavlovskyi, Haemaphysalis douglasi, and Haemaphysalis megaspinosa, newly recorded in China, and other Haemaphysalis spp. were all negative for Borrelia. Based on a polymerase chain reaction restriction fragment length polymorphism analysis of the 45 strains successfully subcultured, these were classified as 29 Borrelia garinii and 16 Borrelia afelii. These strains seemed to be more closely related to Japanese strains in genetic features than to those from Europe. The result of sodium dodecyl sulfate-polyacrylamide gel electrophoresis suggested more diversity in both genospecies, but Borrelia burgdorferi sensu stricto was not found.

Moving one DNA double helix through another by a type II DNA topoisomerase: the story of a simple molecular machine

The discovery of the double helix structure of DNA led immediately to questions on the mechanics of unravelling its intertwined strands during replication. If a parental DNA is to be duplicated into two progeny molecules by separating its two strands and copying each, then the strands must untwine rapidly during replication (Watson & Crick, 1953).

That DNA indeed replicates in such a semiconservative fashion was soon demonstrated by the Meselson–Stahl experiment (1958). At first, it appeared that the unravelling of the intertwined strands should not pose an insurmountable mechanical problem. The two strands at one end of a linear DNA, for example, can be pulled apart with concomitant rotation of the double-stranded portion of the molecule around its helical axis. If the strands of a DNA double helix are to separate at an estimated replication rate of 100000 base pairs (bp) per minute, then the speed of this rotation would be 10000 revolutions per minute from the 10 bp per turn helical geometry of the double helix. This speed, though impressive, seemed reasonable: owing to the slender rod-like shape of the double helix, the estimated viscous drag for this rotational motion is actually rather modest (Meselson, 1972).

Blood thrombopoietin levels in clonal thrombocytosis and reactive thrombocytosis

BACKGROUND

Although the distinction between clonal and reactive thrombocytosis is clinically relevant because clonal thrombocytosis has more thrombohemorragic complications, the differential diagnosis of these two entities can be difficult. Methods such as the detection of unstimulated erythroid or megakaryocyte colony growth are not readily available. Therefore, we measured blood thrombopoietin levels to determine whether these levels can be used to distinguish the two conditions.

PATIENTS AND METHODS

Thrombopoietin levels were measured in 73 patients with thrombocytosis (platelet count > 500,000/microL), including 39 patients with clonal thrombocytosis (20 patients with essential thrombocythemia, 15 with agnogenic myeloid metaplasia, 1 patient with polycythemia vera, and 3 with undefined myeloproliferative disorders) and 34 patients with reactive thrombocytosis (17 with malignant tumors, 11 with inflammatory diseases, 4 with sickle cell disease, and 2 with iron deficiency anemia). Seventeen normal volunteers were used as controls.

RESULTS

Thrombopoietin levels were significantly higher (P < 0.05) in patients with clonal thrombocytosis (mean +/- SD of 555 +/- 585 pg/mL), including the subgroup with essential thrombocythemia (505 +/- 459 pg/mL), than in patients with reactive thrombocytosis (290 +/- 133 pg/mL) who had similar levels as controls (201 +/- 112 pg/mL). Thrombopoietin levels in patients with clonal thrombocytosis, including essential thrombocythemia, were not correlated with platelet counts.

CONCLUSIONS

Thrombopoietin levels may be helpful in distinguishing between clonal thrombocytosis and reactive thrombocytosis. Thrombopoietin is probably responsible for the elevated platelet counts in clonal thrombocytosis including essential thrombocythemia, but not in reactive thrombocytosis. High thrombopoietin levels in patients with clonal thrombocytosis cannot be explained solely by platelet megakaryocyte mass.

Plasmids for the in vitro analysis of RNA polymerase II-dependent transcription based on a G-free template

Described are a series of plasmids containing combinations of adenovirus-2 major late promoter elements, including consensus TATA box and initiator, upstream of G-free transcription cassettes of various lengths. These provide an assortment of tools for investigating both basal and regulated transcription mechanisms by in vitro transcription methods.

Purification and characterization of the Sgs1 DNA helicase activity of Saccharomyces cerevisiae

The yeast Saccharomyces cerevisiae Sgs1 protein is a member of a family of DNA helicases that include the Escherichia coli RecQ protein and the products of human Bloom's syndrome and Werner's syndrome genes. To study the enzymatic characteristics of the protein, a recombinant Sgs1 fragment (amino acids 400-1268 of the 1447-amino acid full-length protein) was overexpressed in yeast and purified to near homogeneity. The purified protein exhibits an ATPase activity in the presence of single- or double-stranded DNA. In the presence of ATP or dATP, unwinding of duplex DNA or a DNA-RNA heteroduplex by the recombinant Sgs1 fragment was readily observed. Similar to the E. coli RecQ helicase, displacement of the DNA strand occurs in the 3' to 5' direction with respect to the single-stranded DNA flanking the duplex. The efficiency of unwinding was found to correlate inversely with the length of the duplex region and was enhanced by the presence of E. coli single-stranded DNA-binding protein. In addition, the recombinant Sgs1 fragment was found to bind more tightly to a forked DNA substrate than to either single- or double-stranded DNA.

Analysis of FHIT transcripts in cervical and endometrial cancers

Carcinoma of the uterine cervix is a common malignancy, and many affected women, have been found to exhibit loss of heterozygosity (LOH) in the chromosome 3p region. Recent studies have localized the FHIT (fragile histidine triad) gene in this region and also demonstrated a high frequency of abnormalities of this gene in various cancers. To determine the role of the FHIT gene in cervical and uterine carcinomas, 16 cases of cervical carcinoma and 7 cases of endometrial carcinoma, as well as nearby non-cancerous tissues in these patients, were analyzed by reverse transcription of the FHIT mRNA followed by polymerase chain reaction amplification and sequencing of the products. In this study, 13 of 16 cervical cancers and 4 of 7 endometrial cancers displayed abnormal FHIT transcripts, including a lack of 2 or more exons of the FHIT gene, the insertion of several bases in the deletion junctions, and a 282 bp deletion from cDNA 171 to 452, resulting in a frameshift. Moreover, 5 of 16 matched non-cancerous tissues from the cervical cancer patients and 4 of 7 non-cancerous tissues from endometrial cancer patients also showed the presence of abnormal transcripts lacking 3 or more exons of the FHIT gene. Only 1 of 23 paired samples exhibited LOH. Our results suggest that the abnormal transcript of the FHIT gene is common in both normal and tumor tissues of the uterus and cervix. We also checked for HPV infection in these samples and found no definite relationship between the abnormal transcript and human papillomavirus infection.

Further characterization of the glucocorticoid response unit in the phosphoenolpyruvate carboxykinase gene. The role of the glucocorticoid receptor-binding sites

Phosphoenolpyruvate carboxykinase (PEPCK) catalyzes the rate-limiting step of gluconeogenesis. The activity of this enzyme is controlled by several hormones, including glucocorticoids, glucagon, retinoic acid, and insulin, that principally affect the rate of transcription of the PEPCK gene. Glucocorticoids induce PEPCK gene transcription through a complex glucocorticoid response unit that consists of, from 5' to 3', accessory factor elements AF1 and AF2; two noncanonical glucocorticoid receptor-binding sites, GR1 and GR2; a third accessory factor element, AF3; and a cAMP-response element, CRE. A complete glucocorticoid response is dependent on the presence of both GR-binding sites, all three accessory elements, and the CRE. In this study we assess the relative roles of GR1 and GR2 in the context of the glucocorticoid response unit and use a combination of binding and function assays to compare GR1 and GR2 to glucocorticoid response elements (GREs) that conform closely to the consensus sequence. The relative binding affinity of GR follows the order: consensus GRE >> GR1 > GR2. Mutations that disrupt the binding of GR to GR1 result in a major reduction of the glucocorticoid response, whereas similar mutations of GR2 have a much smaller effect. Unlike the simple consensus GRE, neither GR1 nor GR2 mediate a glucocorticoid response through a heterologous promoter. The accessory elements appear to have different functional roles. AF2 is still needed for a maximal glucocorticoid response when GR1 is converted to a high-affinity GR-binding element, but AF1 and AF3 are not required.

Porphyromonas gingivalis, Prevotella intermedia and Bacteroides forsythus in plaque subjacent to bridge pontics

This study examined the distribution of P. gingivalis, P. intermedia and B. forsythus in plaque on metallic and porcelain pontics adjacent to healthy and inflamed mucosa. Subpontic plaque was collected from 33 inflamed and 31 healthy sites. Plaque suspension was incubated with specific rabbit antisera to P. gingivalis (FDC 381), P. intermedia (ATCC 25261) and B. forsythus (FDC 335), and the labelled cells disclosed with fluorescein-labelled goat-anti-rabbit IgG by indirect immunofluorescence microscopy. Mean proportions of P. gingivalis, P. intermedia, and B. forsythus at inflamed sites were 0.60+/-0.75, 2.48+/-2.28, and 0.44+/-0.64% respectively, and at healthy sites 0.21+/-0.43, 1.27+/-1.05, and 0.15+/-0.18% respectively. These differences were statistically significant. Almost all sites were positive for P. intermedia, whereas only 12/31 healthy and 21/33 inflamed sites were positive for P. gingivalis. 18/31 healthy and 28/33 inflamed sites were positive for B. forsythus. P. intermedia was recovered in higher proportions from metallic pontics adjacent to inflamed sites (MI) than healthy sites (MH) or porcelain pontics next to inflamed (PI) or healthy sites (PH). P. gingivalis is was recovered in higher proportions from MI than PH. We conclude that both the nature of the pontic material and the health status of the mucosa affect the composition of the associated microbiota.