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M Locke

Publications and source records attributed to M Locke.

83 records · Page 5Linked to original sources
PubMed1968

Protein uptake into multivesicular bodies and storage granules in the fat body of an insect.

The fat body in Calpodes ethlius (Lepidoptera, Hesperiidae) takes up protein from the blood throughout the larval stage before pupation. Depending upon the phase of development, the protein appears in multivesicular bodies, in large storage granules, and in structures of intermediate form. There are three phases in the 8 days of the last larval stage; the first devoted to growth (molting to 66 hr), the second to synthesis for storage or export (M + 66 to M + 156 hr), and the third to preparation for pupation (M + 156 to pupation at M + 192 hr). From M + O to M + 156 and from M + 180 to M + 188 hr, protein is taken up into multivesicular bodies. Larger MVB's form a continuous series with the protein granules formed from M + 162 to M + 180 hr. Blood proteins increase in concentration and amount from M + 66 to M + 156 hr at the same time as the fat body cells have a high rate of incorporation of amino acids and a structure appropriate for protein synthesis. During granule formation, both amino acid incorporation and blood protein concentration decrease. Since foreign proteins injected into the blood appear in the granules, they are probably made mainly from sequestered blood. Protein uptake involves two stages: concentration between the cells, and ingestion in pinocytotic vesicles. The vesicles fuse to become MVB's or storage granules, depending upon their rates of growth and the addition of lytic enzymes. Since MVB's do not accumulate in the fat body and since many of them contain acid phosphatase and appear empty, they are presumed to be concerned in protein turnover.

Acid Phosphatase↗
PubMedDate not supplied

Cardiomyoplasty: comparison of latissimus dorsi muscles of three large mammals with that of human.

Cardiomyoplasty has the potential to become an alternative therapy for congestive heart failure patients and is presently in Phase III clinical trials. In experimental studies, it is necessary to use an animal with muscle characteristics that resemble those of humans. Therefore, the purpose of this study was to compare morphological and biochemical characteristics of the latissimus dorsi muscle (LDM) of three common large mammals with those of human. Of the three mammals studied, the goat had the most overall similarities to the human when comparing mitochondrial capacity, percent fiber types, fiber areas, myofibrillar (MF)-AT-Pase activity, and 72-kDa heat shock protein (HSP) content. The pig was dissimilar to the human in its fiber-type arrangement, glycolytic capacity, percent fiber type, MF-ATPase activity, and HSP-72 content. The dog differed from the human in that it had high-mitochondrial enzyme activity, a fiber-type profile consisting of all high-aerobic fibers, and fiber cross-sectional areas that were nearly half those of humans. These findings show that the LDM of the goat most resembles that of the human.

Animals↗
PubMedDate not supplied

Preservation of the latissimus dorsi muscle during cardiomyoplasty surgery.

BACKGROUND: Cardiomyoplasty surgery has been shown to be associated with damage and degeneration of the assisting skeletal muscle. The purpose of this study was to use ischemic (short-term) and thermal (long-term) preconditioning to protect the muscle during surgery and the subsequent ischemia. METHODS: Three 10-minute cycles of ischemia-reperfusion were accomplished noninvasively on goat latissimus dorsi muscle (LDM) immediately prior to surgery. In another experiment, LDM was noninvasively heat shocked for 20 minutes at 42 degrees C 24 hours prior to surgery. LDM damage was evaluated 5 days postsurgery using enzyme activities (beta-glucuronidase, beta-GLN; citrate synthase), hydroxyproline, morphology, and blood flow. RESULTS: The lysosomal enzyme, beta-GLN, was significantly increased (43%, p < 0.05) by surgical dissection and remained high in the ischemic preconditioned LDM (58%, p < 0.05) and in the heat shocked LDM (57%, p < 0.05). CONCLUSION: These findings show that these two protective protocols do not reduce the muscle damage that occurs during surgical preparation of the LDM for cardiomyoplasty.

Animals↗
PubMedDate not supplied

Are prosome particles formed by the disintegration of proteasomes?

Quail reticulocyte 19S "prosome" fractions isolated on sucrose density gradients contain two kinds of particles: cylindrical proteasomes and ferritin. When samples of this fraction are prepared for electron microscopy using the one-step stain protocol described in this paper, most of the particles have a rectangular image resembling the proteasome. However, when samples are prepared for electron microscopy using the two-step stain protocol described here, there are few rectangular images. Their place is taken by round particles that resemble the prosome. Thus it appears that the round, raspberry-shaped particles called prosomes and the ring-like proteasome particles may be artifacts of specimen preparation for electron microscopy. We propose that proteasome particles may disintegrate when prepared for electron microscopy by methods such as the two-step stain protocol and that prosome particles represent the component parts of the proteasome. Furthermore, based on the enhancement of proteasome images obtained using the one-step main protocol we propose that, instead of consisting of a stack of four rings, the proteasome is constructed of three components, i.e., a spherical central particle flanked by two flat hexagonal end caps.

Animals↗