A method for estimating an overlying layer correction in quantitative ultrasound imaging

A new method is tested to compensate for attenuation losses through the intervening layers in quantitative ultrasound imaging. The method subtracts the echo signal power spectrum acquired from a uniform region beneath the overlying layers from the signal power spectrum obtained from a reference phantom using the same instrumentation system settings. Changes in spectral components with frequency are then used to estimate the attenuation of the overlying layers. Several phantoms were used to test the method, among which was a phantom having three windows, one with no overlying layers and the other two with fat and muscle mimicking layers of different degrees of irregularity. Attenuation losses through the windows were compensated for using the technique, producing backscatter estimator images of a simulated tumor inside the phantom. After applying the method, consistent results for the backscatter estimator of the tumor, as well as the backscatter coefficient of the background material, were obtained from the various windows.

Regulation of cyclin E and p27kip during mitosis in BALB/c 3T3 cells

We have examined the level of cyclin E, a G1 cyclin, and p27kip, a cyclin-dependent kinase inhibitor, in BALB/c 3T3 cells. Cell populations stimulated to undergo cell cycle traverse displayed little change in the level of cyclin E, while p27kip was found to be reduced 50-80% in proliferating cells. Analysis of mitotic cells, however, revealed that cyclin E is virtually absent and begins to reaccumulate soon after mitosis is complete, as does p27kip. Immunoprecipitation experiments revealed that p27kip is associated with cyclin E in quiescent but not proliferating cells, indicating that it may function to prevent development of cyclin E activity in the absence of growth factors. Based on our characterization of cyclin E and p27kip in BALB/c 3T3 cells during progression of the cell cycle, we propose a model of growth regulation controlling the G1 phase of growing and quiescent cells involving mitotic degradation of cyclin E and recovery of p27kip inhibitory activity in a late or postmitotic interval.

Mutations in the gene for the granulocyte colony-stimulating-factor receptor in patients with acute myeloid leukemia preceded by severe congenital neutropenia

BACKGROUND

In severe congenital neutropenia the maturation of myeloid progenitor cells is arrested. The myelodysplastic syndrome and acute myeloid leukemia develop in some patients with severe congenital neutropenia. Abnormalities in the signal-transduction pathways for granulocyte colony-stimulating factor (G-CSF) may play a part in the progression to acute myeloid leukemia.

METHODS

We isolated genomic DNA and RNA from hematopoietic cells obtained from two patients with acute myeloid leukemia and histories of severe congenital neutropenia. The nucleotide sequences encoding the cytoplasmic domain of the G-CSF receptor were amplified by means of the polymerase chain reaction and sequenced. Murine myeloid 32D.C10 cells were transfected with complementary DNA encoding the wild-type or mutant G-CSF receptors and tested for their responses to G-CSF.

RESULTS

Point mutations in the gene for the G-CSF receptor were identified in both patients. The mutations, a substitution of thymine for cytosine at the codon for glutamine at position 718 (Gln718) in one patient and at the codon for glutamine at position 731(Gln731) in the other, caused a truncation of the C-terminal cytoplasmic region of the receptor. Both mutant and wild-type genes for the G-CSF receptor were present in leukemic cells from the two patients. In one patient, the mutation was also found in the neutropenic stage, before the progression to acute myeloid leukemia. The 32D.C10 cells expressing mutant receptors had abnormally high proliferative responses but failed to mature when cultured in G-CSF. The mutant G-CSF receptors also interfered with terminal maturation mediated by the wild-type G-CSF receptor in the 32D.C10 cells that coexpressed the wild-type and mutant receptors.

CONCLUSIONS

Mutations in the gene for the G-CSF receptor that interrupt signals required for the maturation of myeloid cells are involved in the pathogenesis of severe congenital neutropenia and associated with the progression to acute myeloid leukemia.

Functional assay of plasma antithrombin using polyethylene glycol (PEG) defibrinated plasma

Polyethylene glycol(PEG) was used to precipitate fibrinogen to prepare defibrinated plasma in the two stage clotting assay of antithrombin activity. Five percent PEG-8000 precipitated fibrinogen from plasma without loss of antithrombin activity in the defibrinated plasma. Fibrin degradation products(FDP) as high as 640 ug/ml did not interfere the two stage clotting assay using PEG defibrinated plasma possibly because part of FDP was precipitated by PEG in the process of plasma defibrination. The two stage clotting assay was very sensitive to the changes of antithrombin activity in the range of 60%-100% of normal level. The assay was reproducible and correlated with chromogenic assay. The decrease of plasma antithrombin activity in a baboon septic shock model was demonstrated with this assay.

[Changes of proteoglycans in lumbar intervertebral disc of bipedal rats with aging]

Using a computer based image analysis system and histological sections stained with Safranin O, we investigated systematically the variation of proteoglycans (PG) contents in the low lumbar discs of bipedal rats. Topographically, the PG concentration increased from the outer annulus to the inner nucleus pulposus region, which possesses the highest PG concentration. The PG content decreased with age, and a significant loss of PG was observed in the lumbar discs of bipedal rats as compared with controls, especially in the nucleus pulposus. These observations support the view that the higher abnormal mechanical stress accelerates disc degeneration.

Hematopoietic growth factor receptors: structure variations and alternatives of receptor complex formation in normal hematopoiesis and in hematopoietic disorders

Receptors of most hematopoietic growth factors are structurally related and grouped in the hematopoietin or cytokine receptor superfamily. In this paper, we will first review the general principles of hematopoietin receptor complex formation and cytoplasmic signaling. Subsequently, the significance of defective hematopoietic growth factor receptors for the development of hematological diseases will be discussed.

The phage T4-coded DNA replication helicase (gp41) forms a hexamer upon activation by nucleoside triphosphate

Sedimentation and high performance liquid chromatography studies show that the functional DNA replication helicase of bacteriophage T4 (gp41) exists primarily as a dimer at physiological protein concentrations, assembling from gp41 monomers with an association constant of approximately 10(6) M-1. Cryoelectron microscopy, analytical ultracentrifugation, and protein-protein cross-linking studies demonstrate that the binding of ATP or GTP drives the assembly of these dimers into monodisperse hexameric complexes, which redissociate following depletion of the purine nucleotide triphosphatase (PuTP) substrates by the DNA-stimulated PuTPase activity of the helicase. The hexameric state of gp41 can be stabilized for detailed study by the addition of the nonhydrolyzable PuTP analogs ATP gamma S and GTP gamma S and is not significantly affected by the presence of ADP, GDP, or single-stranded or forked DNA template constructs, although some structural details of the hexameric complex may be altered by DNA binding. Our results also indicate that the active gp41 helicase exists as a hexagonal trimer of asymmetric dimers, and that the hexamer is probably characterized by D3 symmetry. The assembly pathway of the gp41 helicase has been analyzed, and its structure and properties compared with those of other helicases involved in a variety of cellular processes. Functional implications of such structural organization are also considered.

[An experimental study on the relationship between disc nutrition and disc degeneration]

Micro-angiography, scanning electron microscopy and hydrogen washout technique were used to investigate the disc nutrition condition and the nutritional pathway of endplate in bipedal rats with agting. Compared with the controls, the nutrition condition of bipedal rats underwent deterioration and the number of vascular distribution under the endplate decreased significantly, but no increase in thickness of endplate caused by microfractures of subchondral bone and callus formed during the healing process was observed. The abnormal stress may bring about vertebral body intra-osseous circulation disorder and then consequent decrease of vascular channels which related to the disturbance of disc nutrition. This strongly suggested that nutrition conditions of nucleus pulposus were not deteriorated by impaired diffusion capacity, but by decrease of vasculature that contacts with endplate.

A point mutation in the granulocyte colony-stimulating factor receptor (G-CSF-R) gene in a case of acute myeloid leukemia results in the overexpression of a novel G-CSF-R isoform

A novel human granulocyte colony-stimulating factor (G-CSF) receptor isoform, designated SD, has been identified in which the distal C-terminal cytoplasmic region, previously shown to be essential for maturation signalling, is substituted by an altered C-terminus. The SD receptor has a high affinity for G-CSF and retains the membrane-proximal cytoplasmic region known to be sufficient for proliferative signalling. Nonetheless, the SD isoform lacks the ability to transduce growth signals in murine BAF3 cells and, in contrast to the wild-type G-CSF receptor, is scarcely capable of activating JAK2 kinase. Expression of SD receptor was found to be low in normal granulocytes, but was significantly increased in a patient with acute myeloid leukemia (AML). The leukemic cells of this patient harbour a point mutation in the SD splice donor site of the G-CSF receptor gene. These findings provide the first evidence that mutations in the G-CSF receptor gene can occur in certain cases of clinical de novo AML. The possible contribution of defective G-CSF receptor signalling to leukemogenesis is discussed.

[Comparative study of three different hip function evaluation systems]

Harris's, Charnley's and Beijing's numerical rating systems were used to evaluate the functional results of 42 cases of bipolar type artificial femoral head replacement. The results of assessment of the three methods were compared statistically and proved that the results are comparable. Before the overall evaluation, the patients should be divided into three groups (according to Charnley's method) on the basis of their original capacity of locomotion. The score results of the three groups should not be mixed up. The calculation method of total score of Beijing system may need certain modification. The advantages and disadvantages of the three systems, the significance of capacity assessment of daily activity and radiological evaluation are discussed on the basis of the results of analysis.

Identification of a nonsense mutation in the granulocyte-colony-stimulating factor receptor in severe congenital neutropenia

Severe congenital neutropenia (Kostmann syndrome) is characterized by profound absolute neutropenia and a maturation arrest of marrow progenitor cells at the promyelocyte-myelocyte stage. Marrow cells from such patients frequently display a reduced responsiveness to granulocyte-colony-stimulating factor (G-CSF). G-CSF binds to and activates a specific receptor which transduces signals critical for the proliferation and maturation of granulocytic progenitor cells. Here we report the identification of a somatic point mutation in one allele of the G-CSF receptor gene in a patient with severe congenital neutropenia. The mutation results in a cytoplasmic truncation of the receptor. When expressed in murine myeloid cells, the mutant receptor transduced a strong growth signal but, in contrast to the wild-type G-CSF receptor, was defective in maturation induction. The mutant receptor chain may act in a dominant negative manner to block granulocytic maturation.

Distinct cytoplasmic regions of the human granulocyte colony-stimulating factor receptor involved in induction of proliferation and maturation

The granulocyte colony-stimulating factor receptor (G-CSF-R) transduces signals important for the proliferation and maturation of myeloid progenitor cells. To identify functionally important regions in the cytoplasmic domain of the G-CSF-R, we compared the actions of the wild-type receptor, two mutants, and a natural splice variant in transfectants of the mouse pro-B cell line BAF3 and two myeloid cell lines, 32D and L-GM. A region of 55 amino acids adjacent to the transmembrane domain was found to be sufficient for generating a growth signal. The immediate downstream sequence of 30 amino acids substantially enhanced the growth signaling in the three cell lines. In contrast, the carboxy-terminal part of 98 amino acids strongly inhibited growth signaling in the two myeloid cell lines but not in BAF3 cells. Truncation of this region lead to an inability of the G-CSF-R to transduce maturation signals in L-GM cells. An alternative carboxy tail present in a splice variant of the G-CSF-R also inhibited growth signaling, notably in both the myeloid cells and BAF3 cells, but appeared not to be involved in maturation.

Synthesis, characterization, and antioxidative activity of new vitamin B6 triethanolamine rare earth (III) complexes

A series of new vitamin B6 triethanolamine rare earth (III) complexes Re(PN)3(TEA)(NO3)2Cl (PN = pyridoxol; TEA = triethanolamine; Re = La1, Ce2, Pr3, Nd4, Sm5, Tb6, Dy7, Ho8, Er9, Y10), were synthesized and characterized by elemental analysis, molar conductance, TGA-DTA, UV, IR, and 1H NMR spectroscopic techniques. The suppression ratio of complexes for the hydroxyl radical (OH.) and the superoxide radical (O2-.) were determined, the results show that these complexes possess scavenging effects on OH. and O2(-.). In this paper we also discuss the effect of complex conc. for the suppression ratio on superoxide radical O2(-.).

[The contributions of facet joint to the stiffness of the lumbar spine]

In this paper, the changes in the stiffness of eight lumbar spinal segments, as affected by left unilateral partial or total facetectomy, were investigated by means of an electro-mechanical technique. The results showed that with unilateral facetectomy, the stiffness of lumbar spinal segment was 39% less in axial rotation, 14% less in extension, 13% less in lateral bending and 9% less in flexion. This observation suggests that in general clinical practice, close attention must be paid to the patients with facet injury, because in this situation the ability of lumbar spine in resisting torque may be decreased significantly.

[The biological fixation strength of the bone particle impregnated bone cement]

This article reports the result of the comparative study on the biological fixation strength of two kinds of bone particle impregnated bone cement. Organic and inorganic bone particle impregnated bone cement were implanted into alternative side of the upper femurs of New Zealand rabbits. The cancellous bone and cortical bone segments of the implanted femurs removed at intervals of 1, 2 and 3 months after operation were subjected to push-out test. In cancellous bone segment, shearing strength of cement-bone interface was increased gradually, but no significant difference between these two kinds of cement after 3 months operation. In cortical bone segment, the interface shearing strength was lower than that of the cancellous bone, but it increased rapidly from 1 month, especially for the organic bone particle bone cement, after 3 months operation the interface shearing strength had a significant difference between the two kinds of cement. More prominent biological fixation effect showed in the organic bone particle group.

Role of the histone "tails" in the folding of oligonucleosomes depleted of histone H1

An oligonucleosome 12-mer was reconstituted in the absence of linker histones, onto a DNA template consisting of 12 tandemly arranged 208-base pair fragments of the 5 S rRNA gene from the sea urchin Ly-techinus variegatus (Simpson, R. T., Thoma, F. S., and Burbaker, J. M. (1985) Cell 42, 799-808). The ionic strength-dependent folding of this nucleohistone complex was compared with that of a native oligonucleosome fraction obtained from chicken erythrocyte chromatin, which had been carefully stripped of linker histones and fractionated in sucrose gradients. The DNA of this native fraction exhibited a narrow size distribution centered around the length of the 208-12 DNA template used in the reconstituted complex. These two complexes displayed very similar hydrodynamic behavior as judged by sedimentation velocity analysis. By combining these data with electron microscopy analysis, it was shown that the salt-dependent folding of oligonucleosomes in the absence of linker histones involves the bending of the linker DNA region connecting adjacent nucleosomes. It was also found that selective removal by trypsin of the N-terminal regions ("tails") of the core histones prevents the oligonucleosome chains from folding. Thus, in the absence of these histone domains, the bending of the linker DNA necessary to bring the nucleosomes in contact is completely abolished. In addition to the complete lack of folding, removal of the histone tails results in an unwinding at low salt of a 20-base pair region at each flanking side of the nucleosome core particle. The possible functional relevance of these results is discussed.

Nucleosome positioning is determined by the (H3-H4)2 tetramer

It is demonstrated that the histone (H3-H4)2 tetramer can find specific positions on DNA, even in the absence of other histones. Purified histone (H3-H4)2 tetramers were reconstituted onto 208-base-pair (bp) DNA molecules containing a nucleosome-positioning sequence by using salt-gradient dialysis. The stoichiometry of histone tetramer to DNA was shown to be 1:1. Digestion with micrococcal nuclease led to formation of protected DNA fragments of approximately 73 bp. Cleavage of the 73-bp DNA with restriction enzymes produced a small set of defined bands, demonstrating positioning of the (H3-H4)2 tetramer on DNA. Analysis of the restriction digests shows that the 73-bp DNA corresponds mainly to two fragments, one lying on either side of the pseudo-dyad axis of the major position adopted by complete histone octamers on this DNA. This result means that a single (H3-H4)2 histone tetramer can fold approximately 146 bp of DNA with the same positioning as the complete octamer but that a region near the pseudo-dyad is only weakly protected against micrococcal nuclease attack in the absence of histones H2A and H2B.

Analysis of the changes in the structure and hydration of the nucleosome core particle at moderate ionic strengths

In order to better understand the conformational changes induced in the nucleosome core particle by changes in the ionic strength of the media in the range from 0.1 to 0.6 M NaCl, we have conducted a very detailed structural analysis, combining circular dichroism, DNase I digestion, and sedimentation equilibrium. The results of such analysis indicate that the secondary structure of both DNA and histones exhibits small (approximately 5%) but noticeable changes as the salt increases within this range. In the case of DNA, the data are consistent with a trend toward a more relaxed secondary structure. The DNase I pattern of digestion is also altered by the salt and suggests a DNA relaxation around the flanking ends. From the hydrodynamic measurements, we also observe a significant change in the virial coefficients of the particle as the salt increases, which in turn are in very good agreement with the theoretically expected values. Furthermore, the preferential hydration parameter is also found to increase with the salt. We believe that the self-dependent conformational change of the nucleosome core particle is the result of the conjunction of all these subtle changes. Yet, from the present data, their exact relationship to the tertiary structure of the whole particle at the different ionic strengths cannot be exactly defined.

[Rapid detection of human cytomegalovirus DNA in urine samples by polymerase chain reaction in vitro gene amplification]

In the detection of human cytomegalovirus (HCMV) DNA in the urine by polymerase chain reaction (PCR). We have designed and synthesized two pairs of oligonucleotide primers (patent pending) corresponding to the specific and conserved DNA sequences of HCMV AD 169 strain. The sequences of the primers were checked that they did not have cross reaction with either normal human genomic DNA or with other herpesviruses. As less as 1fg of HCMV DNA (equal to the amount of DNA from four HCMV virions) in urine can be detected by the method A total of 47 urine specimens from infants suspected of HCMV infection was examined by PCR and conventional virus isolation simultaneously 31 samples were positive in both PCR and virus isolation; 12 samples were negative in either; 4 samples were positive in PCR but negative in virus isolation. So the samples were further examined by serology and the data showed that there was HCMV-specific IgM in all the virus isolation negative sera examined. The result suggests that HCMV in the above samples is possibly underdetected by virus isolation. Therefore the method described in the paper is a specific, sensitive, rapid conventional and non radioisotopic one for detection of HCMV in urine samples.

DNA and protein determinants of nucleosome positioning on sea urchin 5S rRNA gene sequences in vitro

DNA and protein determinants of nucleosome positioning have been examined after in vitro reconstitutions of native or modified histone octamers onto tandem repeats of 207- and 172-base-pair DNA sequences containing the Lytechinus variegatus 5S rRNA gene and onto monomeric sequences derived from these by digestion with various restriction endonucleases. In all cases, a major nucleosome position as well as a number of minor positions have been observed, which indicates that the generation of multiple positions is an inherent property of the 5S rRNA gene sequence. Interestingly, all positions observed differ by multiples of 10 base pairs. Data obtained under different reconstitution conditions demonstrate that the observed distributions of nucleosomes on these DNA templates are equilibrium distributions. This study has also examined the positioning of histone octamers from which histone "tails" had been removed by tryptic digestion. Results indicate that the histone tails are not determinants of nucleosome positioning. Although our results suggest that the mechanical properties of the 5S rDNA are the fundamental factors determining nucleosome positioning, they are insufficient to direct all nucleosomes into a single location.