Search Results - (Author, Cooperation:L. Golub)

2018-04-20

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Geosciences

Computer Science

Medicine

Natural Sciences in General

Physics

Genetics, Medicine, Diseases

2013-01-25

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

2014-10-18

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2014-10-18

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2014-10-18

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2014-10-18

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2014-10-18

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1089-7674

AIP Digital Archive

Physics

The TRACE Observatory is the first solar-observing satellite in the National Aeronautics and Space Administration's (NASA) Small Explorer series. Launched April 2, 1998, it is providing views of the solar transition region and low corona with unprecedented spatial and temporal resolution. The corona is now seen to be highly filamented, and filled with flows and other dynamic processes. Structure is seen down to the resolution limit of the instrument, while variability and motions are observed at all spatial locations in the solar atmosphere, and on very short time scales. Flares and shock waves are observed, and the formation of long-lived coronal structures, with consequent implications for coronal heating models, has been seen. This overview describes the instrument and presents some preliminary results from the first six months of operation. © 1999 American Institute of Physics.

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1089-7623

AIP Digital Archive

Physics

Electrical Engineering, Measurement and Control Technology

We present a new instrument for space-based observational solar physics, recently flown successfully on a sounding rocket, designed to provide high spatial resolution, time-resolved images of the solar corona at specific wavelengths in the extreme ultraviolet (XUV). The primary instrument employs multilayer x-ray mirrors in a novel geometry that affords quasi-monochromatic imaging at wavelengths tunable continuously over the spectral range from 17.1 to 21.1 nm. The secondary instrument also uses multilayer x-ray mirrors to provide high-resolution imaging at three fixed XUV wavelength bands. Both instruments use charge coupled device detectors and thin A1 filters for rejection of unwanted wavelengths. We describe the design, construction, and performance of the instrument and discuss prospects for the future. © 2002 American Institute of Physics.

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The present study has demonstrated that urea is present in gingival crevicular fluid and its concentration is usually several times higher than that of blood serum or saliva. This supports the hypothesis that the high pH seen in gingival crevices arises from urea. The concentration of crevicular urea was inversely related to the severity of gingival inflammation and increased markedly following periodontal surgery. It was concluded that clinically healthy or slightly inflamed gingivae have a mechanism for concentrating urea in crevicular fluid and that this mechanism is destroyed during inflammation but reconstituted following periodontal surgery.

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The addition of ascorbic acid to tissue culture media was found to increase the collagen and mineral content of bones grown in vitro both effects resulting apparently from an increased rate of collagen synthesis. Ascorbic acid also increased the solubility of the bone collagen, possibly by increasing the accumulation of newly synthesized, soluble, collagen in the bone at a rate faster than the formation of crosslinkages between the collagen molecules. Pretreating bone in vitro with fluoride increased the weight of cultured bone primarily by increasing the mineral content. The effect was greatest in the presence of a low rate of collagen synthesis. When collagen synthesis was accelerated by ascorbic acid, fluoride pretreatment caused a lesser increase in bone mass and actually depressed collagen synthesis. It would appear, therefore, that the effect of fluoride pretreatment on bone growth is dependent in part on the rate of collagen synthesis by bone cells. Fluoride pretreatrnent decreased the solubility of the collagen matrix of bone indicating an affect on intermolecular crosslinking. The increased degree of crosslinking due to the fluoride pretreatment may account, in part, for the inhibition of bone resorption in tissue culture.

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Calvaria were exposed to collagenase in vitro before and after demineralization to determine the effect of the mineral phase on the availability of the collagen matrix to collagenolytic degradation. Other calvaria were cultured, in the presence or absence of parathyroid hormone, in a system that supports active bone resorption but not bone formation. The residual calvaria were then treated with collagenase as described above to study the availability and susceptibility of the remaining bone collagen to enzymatic attack. The mineral phase of the calvaria was found to protect collagen in bone from degradation by collagenase. Removal of the mineral from these bones rendered the remaining pool of collagen available to collagenolytic attack. Both unmineralized and mineralized pools of collagen in the calvaria were degraded during bone resorption in culture and this process was stimulated by parathyroid hormone. Since the demineralized cultured calvaria were degraded by collagenase in vitro to a greater extent than the demineralized uncultured calvaria, it would appear that the collagen matrix, in addition to being made available to collagenolytic attack through the loss of mineral, was altered structurally during bone resorption such that it became more susceptible to enzymatic degradation.

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

The effects of tetracyclines on periodontal epithelial cells were investigated by culturing cells from porcine rests of Malassez in the presence of oxytetracycline, doxycycline or one of two analogues of tetracycline bearing no antimicrobial activity. Matrix metalloproteinase activity produced by the epithelial cells was assayed by quantitation of radioactive gelatin degradation and by gelatin enzymography. The results show that all tested tetracyclines exerted a direct dose-dependent inhibitory effect on epithelial cell gelatinases. Furthermore, epithelial cells cultured with doxycycline, oxytetracycline and de-dimethylaminot-etracycline in concentrations ranging from 1 to 50 μg/ml showed a marked reduction in secreted gelatinase activity when grown in alpha minimum essential medium in the absence of fetal calf serum. Viability of cells following this treatment, measured as lactate dehydrogenase activity released to the cell media, was not affected by the presence of any of these drugs at the concentrations used. Scanning electron microscopy revealed striking morphologic changes of the cells following treatment with tetracyclines in the absence of serum which include rounding, decreased intercellular contacts and increased intercellular spaces. No such effects were seen in cells cultured in the presence of serum. These results provide evidence that periodontal epithelial cells produce matrix metalloproteinases whose activities are inhibited by tetracyclines and their non-antimicrobial analogues at concentrations present in gingival crevicular fluid following tetracycline therapy. When used as adjuncts in periodontal therapy, tetracyclines may therefore inhibit epithelial cell mediated degradation of basement membrane and subepithelial connective tissue.

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Tetracyclines are now recognized to have non-antimicrobial properties with therapeutic potential - for example, these agents can inhibit pathologic collagenolysis by blocking mammalian collagenases and other matrix-degrading metal-loproteinases. In the current study, adult human subjects with moderate chronic periodontitis were administered specially formulated capsules of doxycycline, containing lower-than-usual amounts of this semisynthetic tetracycline, on a daily basis for 2 weeks prior to a full-thickness flap procedure; control subjects were administered placebo capsules. The gingiva excised during this surgical procedure were extracted, the extracts partially purified and analyzed for collagenase activity using [3H-methyl] collagen as substrate and the techniques of SDS-PAGE/fluorography or liquid scintillation spectrometry. In the absence of any drug pre-treatment, or after a 2-wk regimen of placebo capsules, the gingival extracts exhibited pathologically-excessive mammalian collagenase activity. The 2-wk regimen of low-dose doxycycline capsules reduced this activity by approximately 60–80% (p 〈 0.05 and 〈 0.01, respectively); in vitro exposure of the gingival extract to doxycycline also inhibited its collagenase activity. Collagenase activity in the crevicular fluid of periodontal pockets of an additional group of subjects was also significantly reduced, as was the severity of inflammation at the same gingival sites. The results suggest that a regimen of low-dose doxycycline capsules may provide a safe (other studies indicate that this regimen may not induce tetracycline resistance in the subgingival plaque) and effective adjunct to instrumentation therapy in the management of pathologic collagenolysis in the periodontal patient. However, further studies are necessary to confirm this hypothesis.

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

A new approach (pool-expansion) has been applied for quantifying the in vivo fractional rate of gingival collagen production. This approach obviates a major shortcoming inherent in a lraditional tracer approach; decreasing specific radioactivity S. R., DPM/μg proline of tissue free-Phlproline oocurring throughout the interval during stuch production is meausured, Poolexparision, involving the injection of excess unlaheled proline concomitant with a tracer amount of nidiotabeled proline, has been judged successful for incisor gingiva of non-diabetic control rats by the following enteria. (I) the S. R. of gingival tree-PHlproline remained constant from 0.5 to 2 h after Phlproline anjection and (2) during this interval, radiolabeled collagen Phlhydroxyprobne S. R. inereised linearly in contrasl pool-expansion in gingiva of diabetic rats was less successful 0.5 h after injection, the S. R. of gingival free S. R. of gingival freep-Phlproline was less than that after 2 h. indicating incomplete pool-expansion at 0.5 h.For meisor gingiva of non-diabetic control rats, the fractronal rate of collagen production 1–1% a day is slouer than that in rat skin, For incisor gingiva of diaberic rats, the fractronat rate in reduced by 65%

Electronic Resource

1600-0765

Blackwell Publishing Journal Backfiles 1879-2005

Medicine

Recently, a new mechanism was proposed to explain the therapeutic efficacy of tetracyclines in periodontal disease— that specifically these antibiotics directly inhibit the activity of collagenase (and possibly other collagenolytic enzymes) produced by the host tissues resulting in a reduced rate of collagen breakdown (Golub et al. 1983). In the current studies, the effect of tetracyclines (minocycline, doxycycline, tetracycline) on collagenolytic enzyme activity was examined in human periodontal pockets and in several animal systems. In the clinical studies, gingival crevicular fluid (GCF) was collected on filter paper strips from individual periodontal pockets, the volume measured with the Periotron 6000, and the Gingival Index and pocket depth scored immediately thereafter at the same sites. The strips were incubated with [3H-methyi] collagen maintained in solution (or with 14C-glycine labeled collagen Fibrils), and the radiolabeled collagen degradation products measured in a liquid scintillation spectrometer, Using the techniques of SDS-PAGE and fluorography, the GCF was observed to generate collagen degradation products characteristic of those produced by mammalian collagenase, a finding consistent with previous studies. Both minocycline and tetracycline therapy reduced GCF collagenolytic activity about 70% during the initial weeks of treatment; the clinical parameters also showed improvements at the same time periods. This reduction in collagenolytic activity had largely regressed by 5 weeks after terminating tetracycline therapy and by 19 weeks after minocycline therapy, in the absence of other forms of periodontal treatment. In a preliminary study, 50 days of doxycycline treatment also reduced GCF collagenase activity, an effect which persisted for at least 2 months (but less than 1 year) after terminating its administration. In several studies involving experimental animals, the tetracyclines (1) in vivo, were found to reduce the pathologically excessive collagenase activity in gingiva and skin of diabetic rats; and (2) in vitro, directly inhibited the activity of collagenases from rat PMNL's and rabbit chondrocytes. The data in the current and our previous studies (Golub et al. 1983, Gomes, Golub & Ramamurthy 1984) continue to support the hypothesis that tetracyclines, by directly inhibiting collagenolytic enzyme(s) activity, may be therapeutically useful in treating diseases, such as periodontitis, characterized by excessive collagen breakdown.

Electronic Resource