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11.
CNBr cleavage of unreduced proenzyme Clr yielded fragment CP2b, isolated by gel filtration and highpressure gel permeation chromatography. This fragment (˜ Mτ 55000) comprised at least 4 disulphidelinked peptides, which were separated by gel filtration after reduction and alkylation. Peptide CP2bRA4, overlapping the A- and B-chain regions in proenzyme Clr was digested by V8 staphylococcal protease, and the digest separated by reversed-phase HPLC. N-terminal sequence analysis of peptide CP2bRA4SP9 established that Clr activation involves the cleavage of a single Arg-Ile bond, located in the sequence: Gln-Arg-Gln-Arg-Ile-Ile-Gly-Gly 相似文献
12.
Evidence from cDNA clones that the rat leukocyte-common antigen (T200) spans the lipid bilayer and contains a cytoplasmic domain of 80,000 Mr 总被引:27,自引:0,他引:27
The leukocyte-common antigen (L-CA or T200) includes a family of lymphoid and myeloid cell surface glycoproteins with apparent molecular weights from 180,000 to 240,000. We report a partial protein sequence for thymocyte L-CA containing 1073 amino acids predicted from cDNA clones isolated using an oligonucleotide probe. Only one segment (residues 347-368) is likely to cross the membrane, and peptide data suggest that sequences N-terminal to this are outside the cell, with residues 369-1073 inside. The cytoplasmic domain includes possible phosphorylation sites and an internal homology between residues 385-671 and 676-986. Analysis of B lymphocyte cDNA clones suggests that B cell and thymocyte mRNAs are identical in 3' sequences, but size differences in Northern blots suggest 5' sequences may differ. 相似文献
13.
Phosphorylation of zymogen granule membrane proteins in intact rat pancreatic acinar cells 总被引:2,自引:0,他引:2
A Peiffer C Gagnon S Heisler 《Biochemical and biophysical research communications》1984,122(1):413-419
The comparative effects of insulin and ethanolamine on 14CO2 production and lipid synthesis from [U-14C]-D-glucose in isolated rat adipocytes were studied. Ethanolamine (10 mM) increased 14CO2 production (glucose oxidation) about 5-fold and lipogenesis about 3-fold as compared to the control. Ethanolamine was more efficient than 25 microU/ml insulin regarding both parameters, but it was less efficient than 200 microU/ml insulin in glucose oxidation, and equally potent in lipogenesis. The combination of ethanolamine and insulin was more active than insulin alone. The mechanisms of ethanolamine action include facilitation of glucose transport and increase of pyruvate dehydrogenase activity. 相似文献
14.
Kenneth R. Miller Jules S. Jacob Ursula Smith Stephen Kolaczkowski Michael K. Bowman 《Archives of microbiology》1986,146(2):111-114
The basic cellular organization of Heliobacterium chlorum is described using the freeze-etching technique. Internal cell membranes have not been observed in most cells, leading to the conclusion that the photosynthetic apparatus of these organisms must be localized in the cell membrane of the bacterium. The two fracture faces of the cell membrane are markedly different. The cytoplasmic (PF) face is covered with densely packed particles averaging 8 nm in diameter, while the exoplasmic (EF) face contains far fewer particles, averaging approximately 10 nm in diameter. Although a few differentiated regions were noted within these fracture faces, the overall appearance of the cell membrane was remarkably uniform. The Heliobacterium chlorum cell wall is a strikingly regular structure, composed of repeating subunits arranged in a rectangular pattern at a spacing of 11 nm in either direction. We have isolated cell wall fragments by brief sonication in distilled water, and visualized the cell wall structure by negative staining as well as deep-etching.Abbreviations PF
protoplasmic fracture face
- EF
exoplasmic fracture face 相似文献
15.
We have studied 11 cases of acute human trichinosis; five of these patients were treated with thiabendazole. We have reviewed the laboratory data for these patients and described their course. This study has failed to show any definite effect of thiabendazole on the course of human trichinosis at the doses used. However, thiabendazole may have decreased the infectivity of the larvae which were embedded in the muscles of our patients. 相似文献
16.
Diabetic neuroarthropathy was observed in four patients; these are the first cases of this nature reported in the Canadian medical literature. The criteria for this diagnosis included: (1) long-standing diabetes; (2) arthropathy, most frequently involving the foot, which shows deformity, shortening and ulceration without evidence of infection or peripheral circulatory failure; (3) abolition or diminution of pain on weight-bearing; (4) diabetic peripheral neuropathy with impaired sense of position or vibration and weak or absent deep tendon reflexes. Radiographic findings were similar to those in patients with Charcot''s arthropathy from any cause.Tabes dorsalis, leprosy, syringomyelia, myelodysplasia and the arthropathies of corticosteroid therapy were ruled out in these cases. In addition to conventional medical therapy the patients were treated by means of walking-casts for several months.Diabetic neuroarthropathy is probably more common than the medical literature would indicate. Diminished sensation in the lower limbs in diabetics of long standing appears to be the major factor contributing to this disorder. 相似文献
17.
18.
Tai C. Chen Norman P. Curthoys Carl F. Lagenaur Jules B. Puschett 《In vitro cellular & developmental biology. Plant》1989,25(8):714-722
Summary Proximal tubules were prepared from rat kidney cortex by collagenase digestion and purified by percoll gradient centrifugation.
Their enrichment was estimated by comparing the specific activities of various cell-specific enzymes in homogenates of renal
cortex and of the isolated tubules. The tubules were cultured in a 50:50 mixture of Dulbecco’s modified Eagle’s and Ham’s
F12 media supplemented with insulin, transferrin, epidermal growth factor, hydrocortisone, and prostaglandin E1. After 2 to 3 d an extensive outgrowth of epithelial cells developed from the attached tubules. After 5 to 7 d near confluent
monolayers were obtained. Hormonal responsiveness, marker enzyme activities, and transport properties were determined to further
characterize the primary cultures. The cultured cells exhibited increased cyclic AMP production in response to parathyroid
hormone but not calcitonin or vasopressin, consistent with the absence of cells derived from distal and collecting tubules.
The cells also retained significant levels of 25-hydroxyvitamin D3-lα-hydroxylase, alkaline phosphatase, and ψ-glytamyltranspeptidase, three enzymes that are primarily associated with the
proximal tubule. The cultured epithelial cells also exhibit a Na+-dependent phosphate and glucose transport systems. Therefore, the cells retain many functional properties that are characteristic
of proximal tubules. Thus, the primary cultures should be suitable for the study of processes that occur specifically within
this segment of the rat nephron.
This work was supported in part by the Veterans Administration (JBP), Washington, DC, by grant DK-37124 (NPC) from the National
Institutes of Health, Bethesda, MD, and by grant BNS-86-17004 (CFL) from the National Science Foundation, Washington, DC. 相似文献
19.
We evaluated the possible contributory role of hypoxia in the development of monocrotaline-induced pulmonary hypertension. Male Sprague-Dawley rats were injected subcutaneously with monocrotaline (60 mg/kg) or saline in controls and were kept in oxygen-enriched (inspired O2 fraction of 0.35) or compressed air chambers. After 21 days, rats were anesthetized while spontaneously breathing room air, hemodynamic parameters and arterial blood gases were measured, and animals were killed. Right ventricular peak systolic pressures (RVPP), right ventricular-to-left ventricular plus septal weight ratios (RV/LV + S), hematocrits, lung dry weight-to-body weight ratios, and medial thickness of pulmonary arteries were significantly reduced in monocrotaline-injected rats exposed to mild hyperoxia compared with air. The air-exposed monocrotaline-injected rats had significantly more arterial hypoxemia than the other groups, and mild hyperoxia had no effect on any of the measured variables in saline-injected rats. To determine whether the effects of mild hyperoxia occurred early or late after monocrotaline injection, we moved separate groups of rats from air to mild hyperoxia and vice versa 10 days after monocrotaline injection. After 21 days, significant reductions in RVPP and RV/LV + S occurred only in rats exposed to mild hyperoxia during the latter 11 days after injection. Our findings suggest that hypoxia contributes to the development of pulmonary hypertension relatively late after monocrotaline injection in rats but that it does not influence the early injury. 相似文献
20.
P Poitras D Gagnon S St-Pierre 《Biochemical and biophysical research communications》1992,183(1):36-40
This study aimed to identify the portion of the 22 amino acid sequence of motilin responsible for the biological activity of the peptide. The contraction of rabbit duodenal muscle in vitro was measured when exposed to synthetic fragments of motilin corresponding to various sequences of the C- or N-terminal portions of the molecule. Fragments 2-22 or 3-22 (where the initial amino acids of the N-terminal ending were removed) were more than 1000 times less potent than the native molecule 1-22. Fragment 1-9 (where the last 13 amino acids located at the C-terminal side of motilin were removed) was devoid of any contractile capacity, while synthetic fragments whose C-terminal structure extended beyond the 1-9 motilin sequence maintained almost complete biological activity. N-terminal amino acid sequence 1-9 is therefore an essential determinant of the contractile activity of motilin. 相似文献