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PubMed1976

Transactions of an international conference. Worldwide concern: better dental care for more people. An international collaborative study. How oral surveys were conducted.

A special form and field manuals defining examination criteria were prepared for recording the following: 1. Number of teeth present both primary and permanent 2. Periodontal disease (a) Oral hygiene using the simplified oral hygiene index. (b) Periodontal condition using a modified P.I. index. (c) Periodontal treatment requirements. 3. Dental caries The DMF index was used with separate coding for filled or crowned teeth having additional primary or secondary decay. 4. Dento facial anomalies Both treatment need and treatment status were recorded. 5. Prosthetic status Possession and requirements for partial or full dentures and bridges were recorded for the age groups 13-14 and 35-44. 6. Oral pathology Pathological conditions of the gingiva and oral mucosa. 7. Need for immediate attention Conditions causing or likely to cause pain or danger to general health unless immediate treatment was given. The recording was carried out using fibre optic illumination, disposable mirrors and sickle probes. X-rays were not utilized. Two roving epidemiologists first established reproducible criteria and then calibrated the local examiners. Re-calibration took place at intervals and repeat examinations of a small sample population ensured reproducibility of recordings. The completed charts were sent to the WHO Oral Health Unit where they were edited and the data transferred to computer tape for analysis. For the present reports three variables--number of carious teeth, caries treatment/need ratio and number of teeth with gingivitis were selected for special study.

Adolescent↗
PubMed1993

[Long-term follow-up of Mobin-Uddin umbrella filter implantation for prevention of pulmonary embolism].

A follow-up of 40 cases of Mobin-Uddin-umbrella implants for prophylaxis of secondary pulmonary embolism is presented. The all-over lethality was 35% (14 patients) including one embolic recurrence. 25 patients could be re-examined 0.2-11.1 years after the implantation, using the patient's history, clinical examination, native X-ray of the umbrella, B-scan of the inferior vena cava, phlebodynamometry of the legs, spirometry, ergometry, manometry of the pulmonary artery pressure. Possible or probable recurrences of embolism were recorded in 15% (5 patients). The umbrella was totally occluded in 48% and partially occluded in 23%. Umbrella-related complications due to faulty insertion were not observed. Patients without additional cardiopulmonary diseases did not show pulmonary hypertension or ventilatory disorders at rest. 86% of the patients suffered from a symptomatical chronic venous insufficiency of one or both legs. Today the Mobin-Uddin-umbrella has been replaced by other percutaneously applicable cava filters. However, their application may also be followed by complications. Therefore the decision to use cava filters of any type should be based on severe selection criteria.

Adolescent↗
PubMedDate not supplied

Dedifferentiated chordoma arising in irradiated sacral chordoma.

A patient who received radiation therapy for a sacral lesion 10 years ago and eventually developed dedifferentiated chordoma at the primary site is reported. Initially, the patient received 54 Gy with Co-60 to the sacral tumor, and 6 years later an additional 50 Gy with 10 MV X-rays to the local recurrence. Four years later, an evident sacral tumor was noticed. When readmitted for re-confirmation of histology, a large rapidly growing lung metastasis was observed. The patient eventually died of progressive disease with incidental aspiration pneumonia. At autopsy, 10 years after the initial treatment, the recurrent sacral tumor proved to be dedifferentiated chordoma accompanied by typical chordoma. Although this case suggests the possible malignant transformation of chordoma rather than collision, the factors inducing this change remain unknown.

Chordoma↗
PubMed1999

Interphase chromosome domain re-organization following irradiation.

PURPOSE: To investigate chromosome domain movements during interphase in stationary cell nuclei. MATERIALS AND METHODS: Contact-inhibited primary human fibroblasts were irradiated with 4.0 Gy X-rays, BrdU was added, and air-dried cell preparations made at intervals up to 48 h. Chromosome 4 domain signals (1, 2 and >2) in BrdU negative nuclei (almost exclusively G0/G1) were counted using FISH. A similar experiment was performed using unstimulated human lymphocytes. RESULTS: A very significant rise in nuclei with >2 signals was found within 1 h after radiation. The frequencies observed were in very good agreement with those expected for simple and complex interchanges involving chromosome 4, scored at metaphase in these materials. CONCLUSIONS: The observations constitute evidence for significant domain movement and re-organization within a short time of radiation exposure in G0/G1 interphase nuclei, presumably induced by the formation of inter-domain exchanges. Such re-organization must be a very complicated and delicate topological problem for relaxed chromatin, and must have an important bearing on the interpretation of mechanistic premature chromosome condensation experiments performed whilst it is in operation.

Cell Line↗
PubMedDate not supplied

Steps toward high specific activity labeling of biomolecules for therapeutic application: preparation of precursor [(188)Re(H(2)O)(3)(CO)(3)](+) and synthesis of tailor-made bifunctional ligand systems.

Two kit preparations of the organometallic precursor [(188)Re(H(2)O)(3)(CO)(3)](+) in aqueous media are presented. Method A uses gaseous carbon monoxide and amine borane (BH(3).NH(3)) as the reducing agent. In method B CO(g) is replaced by K(2)[H(3)BCO(2)] that releases carbon monoxide during hydrolysis. Both procedures afford the desired precursor in yields >85% after 10 min at 60 degrees C. HPLC and TLC analyses revealed 7 +/- 3% of unreacted (188)ReO(4)(-) and <5% of colloidal (188)ReO(2). Solutions of up to 14 GBq/mL Re-188 have been successfully carbonylated with these two methods. The syntheses of two tailor-made bifunctional ligand systems for the precursor [(188)Re(H(2)O)(3)(CO)(3)](+) are presented. The tridentate chelates consist of a bis[imidazol-2-yl]methylamine or an iminodiacetic acid moiety, respectively. Both types of ligand systems have been prepared with alkyl spacers of different length and a pendent primary amino or carboxylic acid functionality, enabling the amidic linkage to biomolecules. The tridentate coordination of the ligands to the rhenium-tricarbonyl core could be elucidated on the macroscopic level by X-ray structure analyses and 1D and 2D NMR experiments of two representative model complexes. On the nca level, the ligands allow labeling yields >95% with [(188)Re(H(2)O)(3)(CO)(3)](+) under mild reaction conditions (PBS buffer, 60 degrees C, 60 min) at ligand concentrations between 5 x 10(-4) M and 5 x 10(-5) M. Thus, specific activities of 22-220 GBq pe micromol of ligand could be achieved. Incubation of the corresponding Re-188 complexes in human serum at 37 degrees C revealed stabilities between 80 +/- 4% and 45 +/- 10% at 24 h, respectively, and 63 +/- 3% and 34 +/- 3% at 48 h postincubation in human serum depending on the chelating system. Decomposition product was mainly (188)ReO(4)(-). The routine kit-preparation of the precursor [(188)Re(H(2)O)(3)(CO)(3)](+) in combination with tailor-made ligand systems enables the organometallic labeling of biomolecules with unprecedented high specific activities.

Cross-Linking Reagents↗
PubMed2005

[Our experience with repair of the scapholunate ligament using the MITEK bone anchor].

PURPOSE OF THE STUDY: A complete rupture of the scapholunate (SL) interosseal ligament results in palmar flexion of the scaphoid and dorsiflexion of the lunate that leads to disintegration of the carpal circle and the development of scapholunate dissociation with dorsal intercalary segment instability. If the injury is not treated properly or early, the abnormal position of the scaphoid and lunate results in degenerative changes of the wrist shown by X-ray and referred to as scapholunate advanced collapse (SLAC). The aim of this study was to evaluate the results of our method used for reconstruction of the SL ligament by means of MITEK bone anchors in acute injury. MATERIAL AND METHODS: The group included 17 patients, 12 male and 5 female, aged 18 to 49 years, with complete SL ligament ruptures. The dominant hand was affected in 10 patients. After the diagnosis had been confirmed, we performed reconstructive surgery involving re-attachment of the SL ligament to the scaphoid by means of the MITEK Mini G2 anchor. The patients were examined by X-rays at 3, 6, 12 and 24 months after the operation to assess the SL angle, capitolunate (CL) angle, SL distance and signs of SLAC. Hand function and pain were evaluated on the basis of the Wrightington Hospital Wrist Scoring (WHWS) system. RESULTS: The average preoperative value of the SL angle was 79 degrees and was corrected to 38 degrees by surgery. By subsequent physical therapy for 12 months, an SL angle of 51 degrees was achieved and increased to 52 degrees during the following year. The CL angle, showing a preoperative average value of 34 degrees, was corrected by surgery to 6 degrees, further increased to 9 degrees by exercising and then remained unchanged. The average SL distance of 5.25 mm preoperatively was reduced to 2.75 mm by surgery with no further change. At 24 months of follow-up, the results of pain evaluation were excellent, good and satisfactory in 41 %, 47 % and 12 % of the patients, respectively, with no poor outcome indicating restriction of the patient's daily activities. Functioning of the hand was excellent in 47 %, good also in 47 % and satisfactory in 6 % of the patients. The range of motion was excellent, good and satisfactory in 24 %, 64 % and 12 % of the patients, respectively. No stiff wrist was recorded after reconstruction of the SL ligament by our method. The hand grip was evaluated as excellent in 47 %, good in 35 % and satisfactory in 18 % of the patients. DISCUSSION: The results show that by reconstruction of the SL ligament with the use of MITEK anchors, radiographic values of the SL and CL angles and SL distance can reach the normal levels within 24 months of the operation. As assessed by the WHWS system, excellent and good results were achieved in 88 % of the wrists treated. Similarly, at 24 months of followup, excellent or good functional outcomes were reported by 94 % of the patients, and excellent or good results in relation to the range of motion and hand grip were experienced by 88 % and 82 % of the patients, respectively. CONCLUSIONS: When treating complete SL ligament ruptures within 4 weeks of injury, stabilization with Kirschner's wires, re-attachment of the SL ligament and suture of the articular capsule are adequate procedures leading to the best results. The ligament reconstruction with MITEK anchors, as presented here, is a relatively simple method giving good results. For treatment of chronic instability it is necessary to use other surgical procedures that, however, will reduce wrist mobility to a greater extent.

Adolescent↗
PubMed1979

The ability of ionizing radiations of different LET to induce chromosomal deletions in Aspergillus nidulans.

Conidia, derived from a strain of Aspergillus nidulans known to carry a specific chromosomal duplication, were irradiated. The duplicated segment had genetic markers, which, when eliminated from the genome, allowed the easy detection of deletion mutants. Survival curves derived following 15 MeV electron and gamma-ray irradiation were characterised by the presence of an appreciable shoulder, whilst 50 kvp X-rays gave a much smaller shoulder. Irradiation with beta-particles and alpha-particles gave rise to exponential survival curves. The RBE values for these radiations, based on the D37 value were for gamma-rays, 1.0, 15 MeV electrons 1.0, 50 kvp X-rays 1.9, beta-particles 2.1 and alpha-particles 3.4. With the exception of gamma-rays the radiations described were compared with respect to their ability to induce chromosomal deletions. When the number of deletants amongst survivors was plotted against dose, a linear relationship was found for electrons, X-rays and beta-particles. The response recorded for alpha-particles was essentially linear but with a biphasic component. The RBE values for the radiations, based on a value of unity for 15 MeV electrons were as follows: X-rays 1.3, beta-particles 0.8, alpha-particles above 7.5 krad 2.3 and below 7.5 krad 3.5. When these same data were re-plotted with number of deletants amongst survivors against log survival, electrons appeared the most efficient radiation at producing deletants amongst survivors, with an "m value" of 283 X 10(-5). Tritiated water was least efficient, the corresponding value being 182 X 10(-5). The number of deletants per 10(4) conidia plated, when plotted against dose yielded a curve which increased to a peak and then decreased linearly for all radiations. The peaks for electrons, X-rays and alpha-particles each had a value of about 14 deletants per 10(4) conidia plated and the peaks roughly corresponded with the point at which the survival curve became exponential and was clearly indicative of the accumulation of sub-lethal damage. However, for beta-particles the peak had a value of 7 deletants per 10(4) conidia plated. A non-DNA target has been implicated for cellular death following beta-particle irradiation.

Americium↗
PubMed1987

[Use of re-infusions of isolated irradiated auto-blood for the correction of hematopoietic disorders].

The effectiveness of re-infusions of auto-blood after isolated irradiation used for the correction of hemocytopenia developing during cancer chemotherapy was studied in 77 patients. 200 ml of the patient's blood was taken into a flask with a preservative and irradiated at an absorbed dose of 220 Gy on the RUM-17 x-ray apparatus. After irradiation the blood was reinfused to a patient. Posttransfusion reactions in the patients were absent. The efficacy and technical simplicity of the method of re-infusions of auto-blood after isolated irradiation make it applicable in clinical practice for the correction of hemopoietic disorders in cancer patients.

Antineoplastic Agents↗
PubMed1988

Crystallographic refinement by simulated annealing. Application to a 2.8 A resolution structure of aspartate aminotransferase.

Crystallographic refinement by simulated annealing with molecular dynamics has been applied to a 2.8 A (1 A = 0.1 nm) resolution X-ray structure of aspartate aminotransferase. Comparison of the refined structure and a structure obtained by combined restrained least-squares refinement and manual re-fitting shows a similar R factor, stereochemistry, and mean difference from the isomorphous replacement phase centroids. Crystallographic refinement by simulated annealing accomplished structural changes and improvements of the electron density maps that were not possible by using restrained least-squares refinement without manual re-fitting. Crystallographic refinement by simulated annealing can generate an ensemble of structures, each of which agrees with the diffraction information. Regions of large variations of the ensemble indicate either erroneously fitted or disordered segments of the macromolecule.

Aspartate Aminotransferases↗
PubMed2005

Dithiolate complexes of manganese and rhenium: X-ray structure and properties of an unusual mixed valence cluster Mn3(CO)6(mu-eta2-SCH2CH2CH2S)3.

Treatment of Mn(2)(CO)(10) with 3,4-toluenedithiol and 1,2-ethanedithiol in the presence of Me(3)NO.2H(2)O in CH(2)Cl(2) at room temperature afforded the dinuclear complexes Mn(2)(CO)(6)(mu-eta(4)-SC(6)H(3)(CH(3))S-SC(6)H(3)(CH(3))S) (1), and Mn(2)(CO)(6)(mu-eta(4)-SCH(2)CH(2)S-SCH(2)CH(2)S) (2), respectively. Similar reactions of Re(2)(CO)(10) with 3,4-toluenedithiol, 1,2-benzenedithiol, and 1,2-ethanedithiol yielded the dirhenium complexes Re(2)(CO)(6)(mu-eta(4)-SC(6)H(3)(CH(3))S-SC(6)H(3)(CH(3))S) (3), Re(2)(CO)(6)(mu-eta(4)-SC(6)H(4)S-SC(6)H(4)S) (4), and Re(2)(CO)(6)(SCH(2)CH(2)S-SCH(2)CH(2)S) (5), respectively. In contrast, treatment of Mn(2)(CO)(10) with 1,3-propanedithiol afforded the trimanganese compound Mn(3)(CO)(6)(mu-eta(2)-SCH(2)CH(2)CH(2)S)(3) (6), whereas Re(2)(CO)(10) gave only intractable materials. The molecular structures of 1, 3, and 6 have been determined by single-crystal X-ray diffraction studies. The dimanganese and dirhenium carbonyl compounds 1-5contain a binucleating disulfide ligand, formed by interligand disulfide bond formation between two dithiolate ligands identical in structure to that of the previously reported dimanganese complex Mn(2)(CO)(6)(mu-eta(4)-SC(6)H(4)S-SC(6)H(4)S). Complex 6, on the other hand, forms a unique example of a mixed-valence trimangenese carbonyl compound containing three bridging 1,3-propanedithiolate ligands. The solution properties of 6 have been investigated by UV-vis and EPR spectroscopies as well as electrochemical techniques.

Journal Article↗
PubMed1998

X-ray crystallographic determination of a collagen-like peptide with the repeating sequence (Pro-Pro-Gly).

The crystal structure of the triple-helical peptide (Pro-Pro-Gly)10 has been re-determined to obtain a more accurate description for this widely studied collagen model and to provide a comparison with the recent high-resolution crystal structure of a collagen-like peptide containing Pro-Hyp-Gly regions. This structure demonstrated that hydroxyproline participates extensively in a repetitive hydrogen-bonded assembly between the peptide and the solvent molecules. Two separate structural studies of the peptide (Pro-Pro-Gly)10 were performed with different crystallization conditions, data collection temperatures, and X-ray sources. The polymer-like structure of one triple-helical repeat of Pro-Pro-Gly has been determined to 2.0 A resolution in one case and 1.7 A resolution in the other. The solvent structures of the two peptides were independently determined specifically for validation purposes. The two structures display a reverse chain trace compared with the original structure determination. In comparison with the Hyp-containing peptide, the two Pro-Pro-Gly structures demonstrate very similar molecular conformation and analogous hydration patterns involving carbonyl groups, but have different crystal packing. This difference in crystal packing indicates that the involvement of hydroxyproline in an extended hydration network is critical for the lateral assembly and supermolecular structure of collagen.

Collagen↗
PubMed2003

Toward novel DNA binding metal complexes: structure and basic kinetic data of [M(9MeG)2(CH3OH)(CO)3]+(M = 99Tc, Re).

To study the interaction of the fac-[M(CO)(3)](+) moiety (M = (99m)Tc, (188)Re) with DNA bases, we reacted [M(OH(2))(3)(CO)(3)](+) with 9-methylguanine (9-MeG), guanosine (G), and 2-deoxyguanosine (2dG). Two bases bind to the metal center via the N7 atoms. X-ray structure analysis of [(99)Tc(CH(3)OH)(9-MeG)(2)(CO)(3)](+) (4) (monoclinic, I2/a, a = 28.7533(14) A, b = 8.0631(4) A, c = 32.3600(15) A, beta = 91.543(6) degrees, V = 7499.6(6) A(3), Z = 8) and [Re(OH(2))(9-MeG)(2)(CO)(3)](+) (7) (monoclinic, P2(1)/n, a = 12.2873(11) A, b = 16.0707(13) A, c = 14.1809(16) A, beta = 103.361(12) degrees, V = 2724.4(5) A(3), Z = 4) reveals that the two bases are in a head-to-tail (HT) orientation. Kinetic studies show that the rates of substitution of the purine bases are comparable to that of one of the active forms of cisplatin. The bis-substituted complexes are generally less stable than the platinum adducts, and metalation of the bases is reversible.

Crystallography, X-Ray↗
PubMed1985

The selected use of ultrasound mammography to improve diagnostic accuracy in carcinoma of the breast.

Our initial experience with diagnostic ultrasound mammography (UM) showed it to be of high diagnostic accuracy and improved specificity when compared with x-ray mammography (XRM) in certain categories of patients. To evaluate this modality further, we reviewed our experience with 600 consecutive patients who underwent ultrasound mammography as part of their initial evaluation for breast disease. Five categories of patients were reviewed: I: age 35 or less--129; II: DY or P-2 pattern on XRM--174; III: negative XRM but symptoms requiring additional evaluation--81; IV: high risk remaining breast in patients previously having mastectomy--48; V: refusal of repeat XRM because of pregnancy, lactation, or fear of radiation exposure--168. Fifty-five solid lesions were diagnosed, including 36 carcinomas. Seventeen of these were not diagnosed on x-ray mammography, giving an improved pick-up of carcinoma in this overall group of 2.83%. Of particular interest was that, of the 27 carcinomas that were found in the group having XRM, 8 or 29.6% were missed on that modality alone. Five of these (62.5%) were patients having a DY pattern. All patients have been followed carefully and re-examined at 3-month intervals, with no evidence of a false negative examination. Overall, we feel diagnostic ultrasound mammography is a valuable adjunct to x-ray mammography and recommend its continued use in selected groups of patients where it has a superior diagnostic accuracy over x-ray mammography alone.

Adolescent↗
PubMed2006

A computational and conceptual density functional theory study of the properties of Re and Tc tricarbonyl complexes.

A computational and conceptual density functional study has been performed on metal tricarbonyl complexes (MTC) of both Re(I) and Tc(I). The fully optimized complexes of fac-[Tc(OH(2))(CO(3))](+) and mer-[Tc(OH(2))(CO(3))](+) show geometries that compare favorably with the X-ray data. These structures were used as a starting point to investigate the relative stability of MTC complexes with various ligands containing combinations of N, O, and S as chelating atoms and to evaluate the stabilizing/destabilizing influence of these ligands. Both for Tc and for Re complexes the nitrogen content turns out to be decisive in the stability of the metaltricarbonyl complexes, the finer details being determined by the hardness sequence N > O > S. As the core of the complexes, [(M(CO)(3)(+)], is hard, the main ordering parameter is changed as compared to our previous studies on Tc(V) [3+1] complexes where the number of sulfur atoms was decisive in accordance with the much softer character of the MOCl core. All results are successfully interpreted in terms of the hard and soft acids and bases principle (HSAB) at the local level.

Carbonates↗
PubMed1996

Preparation, Structure, and Properties of Bis(&mgr;-oxo)dirhenium(III,IV) and -dirhenium(IV) Complexes of Tris(2-pyridylmethyl)amine and Its (6-Methyl-2-pyridyl)methyl Derivatives.

A series of bis(&mgr;-oxo)dirhenium complexes, [Re(2)(&mgr;-O)(2)(L)(2)](PF(6))(n)() (L = tris(2-pyridylmethyl)amine (tpa), n = 3 (1), n = 4 (1a); L = ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Metpa), n = 3 (2), n = 4 (2a); bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me(2)tpa), n = 3 (3), n = 4 (3a)), have been prepared and characterized by several physical methods. X-ray crystallographic studies for 2, 2a.2CH(3)CN.2H(2)O (2a'), and 3a' (ReO(4)(-) salt), include the first structural determinations of (i) the bis(&mgr;-oxo)-Re(III)Re(IV) complex (2) and (ii) the pair of Re(III)Re(IV) and Re(IV)(2) complexes (2 and 2a'). All the complexes have a centrosymmetric structure, suggesting that the mixed-valence state 2 is of structurally delocalized type. The Re-Re distances for 2, 2a.2CH(3)CN.2H(2)O, and 3a' are 2.426(1), 2.368(1), and 2.383(1) Å, respectively, being consistent with the bond order of 2.5 (sigma(2)pi(2)delta(2)delta) for 2 and 3 (sigma(2)pi(2)delta(2)) for the others. Methyl substitution on the pyridyl moiety of the ligands has no significant influence to the overall structure. Cyclic voltammetry of 1 shows two reversible redox waves at -0.77 ((III,III)/(III,IV)) and 0.09 V ((III,IV)/(IV,IV)) vs Ag/AgCl in acetonitrile. The potentials are slightly more positive for 2 (-0.66 and 0.14 V) and 3(-0.64 and 0.20 V). No proton-coupled redox behavior was observed on addition of p-toluenesulfonic acid. Complexes, 1a, 2a, and 3a show a strong visible absorption band at 477 nm (epsilon, 9200 dm(3) mol(-)(1) cm(-)(1)), 482 (11200), and 485 (8700), respectively, which is assigned to the pi-pi transition within the Re(2)(&mgr;-O)(2) core. For the mixed-valence complexes 1, 2, and 3, a strong band is observed in the longer wavelength region (556-572 nm). Crystal data: 2, monoclinic, space group C2/c (No.15), a = 11.799(2) Å, b = 19.457(3) Å, c = 21.742(4) Å, beta = 98.97(1) degrees, Z = 4; 2a', triclinic, space group P&onemacr; (No. 2), a = 13.151(3) Å, b = 13.535(2) Å, c = 10.243(3) Å, alpha = 104.37(2) degrees, beta = 109.02(2) degrees, gamma = 106.87(1) degrees, Z = 1; 3a', monoclinic, space group P2(1)/n (No. 14), a = 13.384(3) Å, b = 14.243(2) Å, c = 13.215(6) Å, beta = 106.88(2) degrees, Z = 2.

Journal Article↗
PubMed2006

On the formation of amelogenin microribbons.

We recently reported the remarkable spontaneous self-assembly and hierarchical organization of amelogenin 'microribbons' and their ability to facilitate oriented growth of apatite crystals in vitro. In a letter of correction we communicated the finding that the X-ray diffraction pattern reported in our original report was that of cellulose contaminant and not amelogenin microribbon. We have re-evaluated our data and confirmed the protein nature of the microribbons using Fourier transform infrared and Raman microspectroscopy. Some microribbons were remarkably similar in their morphology to that of cellulose fibers. The size distribution of amelogenin microribbons was wider, particularly in width and length, and generally smaller than those originally reported. Here we present additional detailed information on the formation of a series of intermediate hierarchical structures of amelogenin assemblies prior to the formation of microribbon. The most significant finding was that full-length amelogenin nanospheres had a tendency to assemble into collinear arrays whose function is assumed to be critical at the initial stage of enamel mineral deposition. The present data gives an insight into the step-by-step assembly process of amelogenin from nanometer scale molecules to micrometer scale organized structures that can be used as templates for controlled and oriented growth of apatite mineralization in vitro.

Amelogenesis↗
PubMed1990

From HeLa cell division to infectious diarrhoea.

Hela S3 cells were grown in suspension both randomly and, synchronously using hydroxyurea which blocks cells at the G1/S interface. Cryosections were prepared, freeze-dried and analyzed by X-ray microanalysis. As cells moved into S and through M phases [Na] and [Cl] increased; both returned to normal levels upon re-entering G1 phase. The Na/K ratio was 1:1 in G1 phase. Infection of HeLa S3 cells in G1 phase with vaccinia virus resulted in no change in intracellular [Na]. Infection of neonatal mice with murine rotavirus was localized to villus tip enterocytes and gave rise to diarrhoea which was maximal at 72h post-infection (p.i.). Diarrhoea was preceded by ischemia of villi (18-42h p.i.) and villus shortening (maximal at 42h p.i.), and was also coincident with a dramatic regrowth of villi. At 48h p.i. a proliferative zone of electron lucent cells was observed in villus base regions. Cryosections of infected gut, taken before, during, and after infection, together with corresponding age-matched controls, were freeze-dried and analysed by X-ray microanalysis. At 48h p.i. electron lucent villus base cells were shown to be more hydrated, and, to contain higher levels of both Na and Cl and lower levels of P, S, K and Mg than corresponding control cells. These studies (we argue) increase confidence in the use of X-ray microanalysis in studying biological systems, provide some insight into the process of cell division, and constitute the basis of a new concept of diarrhoeal secretion.

Animals↗
PubMed2003

Synthesis and characterization of novel rhenium(V) tetradentate N2O2 Schiff base monomer and dimer complexes.

Several rhenium(V) oxo complexes with tetradentate N(2)O(2) Schiff base ligands were synthesized and characterized. The general synthetic procedure involved reaction of [NBu(4)][ReOCl(4)] with a tetradentate Schiff base ligand (L(1) = N,N'-ethylenebis(acetylacetoneimine), (acac(2)en) or L(2) = N,N'-propylenebis(acetylacetoneimine) (acac(2)pn)) in ethanol solution to generate complexes of the form trans-ReOX(L) where X = Cl(-), MeO(-), ReO(4)(-), or H(2)O. The product isolated from the reaction was found to be dependent on the reaction conditions, in particular the presence or absence of water and/or base. The mu-oxo-Re(2)O(3)(L)(2) dimers were synthesized and characterized for chemical and structural comparison to the related monomers. Conversion of the monomer to its dimer analogue was followed qualitatively by spectrophotometry. The complexes were characterized by (1)H and (13)C NMR, UV-vis, and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The crystallographic data reported for the structures are as follows: trans-[ReO(OH(2))(acac(2)en)]Cl (H(20)C(12)ClN(2)O(4)Re) 1, triclinic (Ponemacr;), a = 7.2888(6) A, b = 9.8299(8) A, c = 10.8195(9) A, alpha = 81.7670(10) degrees, beta = 77.1510(10) degrees, gamma = 87.6200(10) degrees, V = 747.96(11) A(3), Z = 2; trans-[ReO(OReO(3))(acac(2)en)] (H(18)C(12)N(2)O(7)Re(2)) 2, monoclinic (P2(1)/c), a = 7.5547(4) A, b = 8.7409(5) A, c= 25.7794(13) A, beta = 92.7780(10) degrees, V = 1700.34(16) A(3), Z = 4; trans-[ReOCl(acac(2)pn)] (H(20)C(13)N(2)O(3)ClRe) 3, monoclinic (P2(1)/c), a = 8.1628(5) A, b = 13.0699(8) A, c = 28.3902(17) A, beta = 97.5630(10) degrees, V = 3002.5(3) A(3), Z = 8; trans-[ReO(OMe)(acac(2)pn)] (H(23)C(14)N(2)O(4)Re) 4, monoclinic (P2(1)/c), a = 6.7104(8) A, b = 27.844(3) A, c = 8.2292(9) A, beta = 92.197(2) degrees, V = 1536.4(3) A(3), Z = 4; trans-[mu-oxo-Re(2)O(3)(acac(2)en)(2)] (H(36)C(24)N(4)O(7)Re(2)) 5, monoclinic (P2(1)/n), a = 9.0064(5) A, b = 12.2612(7) A, c = 12.3695(7) A, beta = 90.2853(10) degrees, V = 1365.94(13) A(3), Z = 2; and trans-[mu-oxo Re(2)O(3)(acac(2)pn)(2)] (H(40)C(26)N(4)O(7)Re(2)) 6, monoclinic (P2(1)/n), a = 9.1190(5) A, b = 12.2452(7) A, c = 12.8863(8) A, beta = 92.0510(10) degrees, V = 1438.01(14) A(3), Z = 2.

Journal Article↗