The role of phosphorylation/dephosphorylation of acetyl-CoA carboxylase in the regulation of mammalian fatty acid biosynthesis.
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Biomedical subjects
Publications and source records attributed to R Holland.
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Sixteen male Holstein calves were fed milk replacer (14% solids) containing 23% crude protein from: 100% milk protein; or 66% soybean protein concentrate plus 34% milk protein as the only nutrients at 8, 9, 10, 11, 12, 12, and 12% body weight from 1 to 7 wk of age, respectively. Eight calves were sensitized to soybean by feeding 66% soybean protein concentrate plus 34% milk protein for 21 d and eight were not sensitized by feeding 100% milk protein. Afterward, each calf received one of the diets for 10 d followed by the other diet for an additional 10 d. During the 2nd wk of the initial period each calf was surgically fitted with a duodenal cannula for biopsy of intestinal mucosa. Biopsies were taken at surgery and on the last day of each period. Feeding 66% soybean protein concentrate plus 34% milk protein resulted in lower body weight gain, decreased feed efficiency, higher rectal temperatures, increased diarrhea, and villus atrophy. Diminished villi size supports other studies reporting allergic reaction to soybean protein and was associated with the poor performance observed in calves fed soybean protein.
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In the posttherapeutic bone marrow of a group of 30 children with acute lymphoblastic leukemia (ALL), small numbers of a particular lymphoid cell with a comparatively large size and large dark nucleus were found. This cell was called the "posttherapeutic lymphoid cell." This type of cell is easily distinguishable in the May-Grünwald-Giemsa-stained smears as well as in semi- and ultrathin Epon sections. Immunoelectron-microscopically it proved to be positive for common ALL. It is hypothesized that the cell might be characteristic for ALL. However, it appeared that this cell could equally be found in non-Hodgkin's malignant lymphoma after a treatment comparable to that in ALL. Furthermore, the cell could be detected in the posttherapeutic bone marrow of children with nonlymphoid malignancies as well as the marrow of very young children (under 2 years of age) with nonmalignant diseases. The results showed that the cell in question is not associated with a particular disease but, rather, represents a special type of lymphoid cell in the regenerating or actively proliferating bone marrow.
Ultrastructural investigation of the nuclei of the lymphoid cell population of bone marrow and blood of children with acute lymphoblastic leukemia regularly shows the presence of two types of nuclear pockets and nuclear clefts. The incidences of these nuclear features decrease significantly during cytostatic therapy. The pockets consist of either a cytoplasmic segment enclosed by a nuclear heterochromatin bridge or a nuclear segment enclosed by an intranuclear cleft. One type of nuclear cleft is, for its greater part of whole length, situated just under the nuclear surface. The other type of cleft is oriented more or less perpendicular to the nuclear surface. It is proposed that these four types be designated as nuclear pockets and nuclear clefts "Type 1" and "Type 2."
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Breast cancer multifocality was studied in mastectomy specimens by correlated specimen radiography and histologic techniques. The patients chosen for study were comparable to those eligible for breast-conserving surgical therapy. Two study groups, one with 282 invasive cancers (T1-2) and the other with 32 intraductal cancers, were selected from a group of 399 consecutive cases by omitting patients who were clearly, or very probably, not candidates for breast-conserving surgical therapy according to current trial criteria. Omitted patients included those with clinically and/or radiologically multifocal cancers and patients with tumor extension into the chest wall or skin (7%). Also excluded were the so-called diffuse invasive cancers (8%), the clinically and radiologically occult tumors (3%), and the invasive cancers larger than 5 cm (3%). Of the 282 invasive cancers, 105 (37%) showed no tumor foci in the mastectomy specimen around the reference mass. In 56 (20%) tumor foci were present within 2 cm, and in 121 (43%) tumor was found more than 2 cm from the reference tumor. In 75 (27%) the tumor foci beyond 2 cm were histologically noninvasive cancers, and in 46 cases (16%) they contained invasive cancers as well. A comparison between the group with reference tumors less than 2 cm and the group with reference tumors more than 2 cm in size showed no significant difference between the groups in terms of presence or absence of tumor foci or distance of tumor foci from the reference tumor. If the 264 invasive cancers in this series that were 4 cm or less in diameter had been removed with a margin of 3 to 4 cm, 7% to 9% of the patients would have had invasive cancer left in the remaining breast tissue, and 4% to 9% would have had foci of noninvasive cancer left in the remaining breast tissue. On the basis of the data on the distribution of tumor at different distances from the reference tumor, the current study estimates the expected rates of local recurrences after breast-conserving surgical procedures relative to the extensiveness of the excision. The possible impact of postoperative local radiation therapy on the rates of expected local recurrence is discussed.
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Insulin and EGF cause identical stimulation (congruent to 40%) of fatty acid synthesis in hepatocytes isolated from rats which have been starved and then refed a low-fat diet. In both cases this stimulation is associated with increased phosphorylation of ATP-citrate lyase and of a specific site on acetyl-CoA carboxylase. However, the altered phosphorylation of acetyl-CoA carboxylase is not associated with a change in kinetic parameters which is detectable in the purified enzyme. Whatever the mechanism involved, stimulation of fatty acid synthesis by growth factors may have a role in providing new phospholipid for growth of membranes.
The kinetic parameters and phosphorylation state of acetyl-CoA carboxylase were analysed after purification of the enzyme by avidin--Sepharose chromatography from extracts of isolated adipocytes treated with glucagon or adrenaline. The results provide evidence that the mechanism of inhibition of acetyl-CoA carboxylase in adipocytes treated with glucagon [Zammit & Corstorphine (1982) Biochem. J. 208, 783-788] involves increased phosphorylation of the enzyme. Hormone treatment had effects on the kinetic parameters of the enzyme similar to those of phosphorylation of the enzyme in vitro by cyclic AMP-dependent protein kinase. Glucagon treatment of adipocytes led to increased phosphorylation of acetyl-CoA carboxylase in the same chymotryptic peptide as that containing the major site phosphorylated on the enzyme by purified cyclic AMP-dependent protein kinase in vitro [Munday & Hardie (1984) Eur. J. Biochem. 141, 617-627]. The dose--response curves for inhibition of enzyme activity and increased phosphorylation of the enzyme were very similar, with half-maximal effects occurring at concentrations of glucagon (0.5-1 nM) which are close to the physiological range. In general, the patterns of increased 32P-labelling of chymotryptic peptides induced by glucagon or adrenaline were similar, although there were quantitative differences between the effects of the two hormones on individual peptides. The results are discussed in terms of the possible roles of cyclic AMP-dependent and -independent protein kinases in the regulation of acetyl-CoA carboxylase activity and of lipogenesis in white adipose tissue.
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Specimen radiography is a very useful tool in the pathologic study of breast cancer in various surgical specimens. The application of this technique in the pathologic examination of clinically occult lesions is mandatory. In the pathologic study of segmentectomy specimens, the specimen x-ray provides a great help in assessing both extent and multifocality of the tumor and in evaluating the completeness of the surgical excision.
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