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B J Marsden F D Sauer B A Blackwell J K Kramer 《Biochemical and biophysical research communications》1989,159(3):1404-1410
The methylcoenzyme M methylreductase reaction has an absolute requirement for 7-mercaptoheptanoylthreonine phosphate or component B, which is the active component of the intact molecule previously referred to as cytoplasmic cofactor. A hydrolytic fragment of cytoplasmic cofactor has been purified and identified as uridine 5'-(O-2-acetamido-2-deoxy-beta-manno-pyranuronosyl acid (1----4)-2-acetamido-2-deoxy-alpha-glucopyranosyl diphosphate) by high resolution NMR and fast atom bombardment mass spectro-metry. It is postulated that UDP-disaccharide may function to anchor 7-mercaptoheptanoyl threonine phosphate at the active site of the methyl-reductase enzyme complex. 相似文献
4.
During the past 18 months, 60 tissue expanders were utilized in the reconstruction of 42 children with burn alopecia of the scalp not amenable to a single excision and primary closure at the Shriners Burns Institute in Galveston, Texas. The children were grouped according to the degree of alopecia. All patients with defects of 15 percent or less of the total hair-bearing scalp were able to obtain complete closure of their defects with two operations, i.e., one to place the expander and the second to remove the expander and advance the flaps. Some patients with defects up to 40 percent were closed with serial expansion. Patients with even larger defects had a significant reduction in the percentage of alopecia and benefited from re-creation of anterior hairlines. We have encountered a postoperative complication rate of 10 percent. When compared to previous methods of treating burn alopecia, tissue expansion allows a more rapid closure, fewer operations and coincident anesthetics, and decreased total length of hospitalization. 相似文献
5.
Transmission and scanning EM-immunogold labeling of Leishmania major lipophosphoglycan in the sandfly Phlebotomus papatasi 总被引:1,自引:0,他引:1
T Lang A Warburg D L Sacks S L Croft R P Lane J M Blackwell 《European journal of cell biology》1991,55(2):362-372
Previous studies using immunostaining and light microscopy demonstrated expression of Leishmania major lipophosphoglycan (LPG) on parasites developing in the sandfly gut from 2 days post infection. By days 4 to 7 post infection, there appeared to be large amounts of parasite-free LPG deposited on/in the microvilli and epithelial cells lining the thoracic midgut, while forward migration of parasites and the morphological changes which accompany metacyclogenesis were associated with developmental modification of the LPG molecules. Studies presented here examine this process with much greater precision using electron microscopy and immunogold labeling techniques to study the different developmental forms (nectomonads, haptomonads, paramastigotes, and metacyclics) of promastigotes in the sandfly gut. Results obtained using LPG-specific monoclonal antibodies (WIC79.3, 45D3 and the metacyclic-specific 3F12) show (1) gold labeling over the cell surface, within the flagellar pocket, and extending along the entire length of the flagellum of electron-dense nectomonads observed in the abdominal and thoracic midgut regions on days 4 and 7 post infection, and of electron-lucid haptomonads in the foregut, (2) dense labeling around the flagellar tips, by which nectomonad forms bind to the midgut microvilli, but not on the microvilli themselves or within the epithelial cells lining the midgut, (3) significant metacyclic-specific (3F12) labeling on nectomonad forms in the lumen of the midgut and attached to the microvilli, and (4) dense labeling on the cell surface of electron-lucid paramastigotes in the esophagus and in the filamentous matrix surrounding paramastigote and metacyclic forms in the esophagus and pharynx. These results are discussed in the light of the proposed roles for LPG in parasite attachment to, and survival in, the sandfly gut. 相似文献
6.
Ronald S. Kaplan June A. Mayor Renee Blackwell Glenn L. Wilson Stephen W. Schaffer 《Molecular and cellular biochemistry》1991,107(1):79-86
The effect of non-insulin-dependent diabetes mellitus (i.e., NIDDM; type 2 diabetes) on the levels of functional mitochondrial anion transport proteins has been determined utilizing
a chemically-induced neonatal model of NIDDM. We hypothesized that moderate insulin deficiency exacerbated by the insulin
resistance, which is characteristic of NIDDM, would cause changes in mitochondrial anion transporter function that were similar
to those we have previously shown to occur in insulin-dependent diabetes mellitus (i.e., IDDM; type 1 diabetes) (Arch. Biochem. Biophys. 280: 181–191, 1990). Our experimental approach consisted of the extraction
of the pyruvate, dicarboxylate and citrate transport proteins from the mitochondrial inner membrane with Triton X-114 using
rat liver mitoplasts (prepared from diabetic and control animals) as the starting material, followed by the functional reconstitution
of each transporter in a proteoliposomal system. This strategy permitted the quantification of the functional levels of these
three transporters in the absence of the complications that arise when such measurements are carried out with intact mitochondria
(or mitoplasts). We found that experimental NIDDM did not cause significant changes in the extractable and reconstitutable
specific (and total) transport activities of the pyruvate, dicarboxylate, and citrate transporters. These results are in marked
contrast to our previous findings obtained using rats with IDDM and negated our hypothesis. The present results, in combination
with our earlier findings, allow us to conclude that insulin plays an important role in the regulation of mitochondrial anion
transporter function. Accordingly, in this model of NIDDM, where the level of insulin is not profoundly deficient, transporter
function is unaltered, whereas in IDDM, where a profound insulinopenia exists, transporter function is altered. Furthermore,
the present studies suggest that in the neonatal model of NIDDM the three mitochondrial transporters investigated are neither
affected by, nor are they the sites of the well documented hepatic post-receptor insulin resistance which is characteristic
of this disease. 相似文献
7.
Alison Blackwell 《Entomologia Experimentalis et Applicata》1988,48(2):149-156
Larvae of the large cabbage white butterfly, Pieris brassicae L. are important pests of cruciferous crops. Third and fifth instars were treated topically with sublethal doses of the formamidine pesticide chlordimeform. A number of excitable actions were induced but they did not persist beyond 24 hours. Following the initial period, however, subsequent development was delayed and mortality increased, particularly when third instars were treated. Dosing fifth-instar larvae caused few further deaths. A link is suggested between these results and the nutritional status of the insects, and they are discussed in terms of how they might contribute towards control.
Résumé Les chenilles de troisième et cinquième stades de P. brassicae L. ont reçu une application superficielle de chlordiméforme, insecticide à la formamidine. Les doses inférieures à 335 g/g ont été sublétales, provoquant plusieurs formes d'excitation. Bien que leur comportement soit redevenu normal en 24 heures, les troisièmes stades traités ont eu leur développement retardé et une mortalité accrue. Le traitement des chenilles plus âgées a eu moins d'effets. Une relation est suggérée entre ces observations et le régime alimentaire de cet insecte; une réduction de l'alimentation, plus importante chez les chenilles de troisième que de cinquième stade de P. brassicae, accompagne le début des altérations du comportement provoquées par le chlordiméforme. La discussion porte sur le mécanisme de contrôle sublétal du chlordiméforme, impliquant des effects immédiats et retardés.相似文献
8.
Stimulation and inhibition of secretion by phorbol myristate acetate in different cell types 总被引:1,自引:0,他引:1
G J Blackwell R W Bonser J Dawson L G Garland 《Biochemical and biophysical research communications》1985,127(3):950-955
In washed human platelets and in HL60 granulocytes phorbol myristate acetate (PMA, 1-2000nM) synergised with threshold concentrations of secretogogues to induce a sustained maximum secretory response. Likewise, superoxide production from HL60 cells maintained a maximal response at PMA concentrations between 30-300nM. At concentrations up to 10nM PMA also augmented calcium ionophore, A23187, stimulated histamine release from rat peritoneal mast cells. However, in the mast cell PMA concentrations above 10nM reduced maximum histamine release in a dose-dependent manner. 相似文献
9.
Interactions of an intact proteoglycan and its fragments with basic homopolypeptides in dilute aqueous solution
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The interactions between a proteoglycan and cationic polypeptides have been investigated by the use of circular-dichroism spectroscopy. The interaction produces an induced conformational change for poly(l-arginine) and poly(l-lysine), similar to the effects previously reported for mucopolysaccharide-polypeptide mixtures. For bovine nasal septum proteoglycan, the interactions are similar to those for chondroitin 4-sulphate, which comprises approximately 63% of the total polysaccharide. The results also suggest that the interactions produce a conformational change in the protein core. Similar studies for the Smith-degradation product show that the protein core can adopt a substantial alpha-helical content and is capable of interactions with poly-(l-arginine). The interactions for chondroitin sulphate ;doublets' are significantly different from those for the separated chains, indicating that the arrangement of the polysaccharide side chains in pairs (and larger groups) along the protein backbone contributes to the interaction properties of the intact proteoglycan. 相似文献