Effect of low ambient temperature on protein turnover and heat production in chicks

1. Effect of low ambient temperature on protein turnover in the liver and whole body was investigated in chicks together with the contribution of protein synthesis to the total heat production. 2. Both protein synthesis and degradation in the whole body were increased, the latter to a larger extent, at low ambient temperature (LT, 22 degrees C) compared with adequate temperature (AT, 30 degrees C). Liver protein synthesis was not significantly altered by the temperature treatment. 3. The total heat production of LT group was as high as 160% of the AT group. 4. The increased heat production due to enhanced whole-body protein synthesis accounted for only 1.4% of the heat increment in thermogenesis at low ambient temperature, suggesting that protein synthesis would contribute little, if any, to cold-induced thermogenesis in chicks.     

Isolation of fungi from bats of the Amazon basin

A total of 2,886 bats captured in the Amazon Basin of Brazil were processed for the isolation of fungi. From the livers, spleens, and lungs of 155 bats (5.4%), 186 fungal isolates of the genera Candida (123 isolates), Trichosporon (26 isolates), Torulopsis (25 isolates), Kluyveromyces (11 isolates), and Geotrichum (1 isolate) were recovered. Seven known pathogenic species were present: Candida parapsilosis, C. guilliermondii, C. albicans, C. stellatoidea, C. pseudotropicalis, Trichosporon beigelii, and Torulopsis glabrata. Twenty-three culture-positive bats showed identical fungal colonization in multiple organs or mixed colonization in a single organ. The fungal isolation rates for individual bat species varied from 1 fungus per 87 bats to 3 fungi per 13 bats, and the mycoflora diversity for members of an individual fungus-bearing bat species varied from 16 fungi per 40 bats to 7 fungi per 6 bats. Of the 38 fungal species isolated, 36 had not been previously described as in vivo bat isolates. Of the 27 culture-positive bat species, 21 had not been previously described as mammalian hosts for medically or nonmedically important fungi.     

Optically detected magnetic resonance studies of porcine pancreatic phospholipase A2 binding to a negatively charged substrate analogue

The direct binding of porcine pancreatic phospholipase A2 and its zymogen to 1,2-bis(heptanylcarbamoyl)-rac-glycerol 3-sulfate was studied by optical detection of triplet-state magnetic resonance spectroscopy in zero applied magnetic field. The zero-field splittings of the single Trp3 residue undergo significant changes upon binding of phospholipase A2 to lipid. Shifts in zero-field splittings, characterized mainly by a reduction of the E parameter from 1.215 to 1.144 GHz, point to large changes in the Trp3 local environment which accompany the complexing of phospholipase A2 with lipid. This may be attributed to Stark effects caused by the binding of a charged group near Trp3 in the enzyme-lipid complex. The cofactor, Ca2+, which is strongly bound to the enzyme active site, has an influence on the bonding, as reflected by smaller zero-field splitting shifts. A relatively small change in the Trp environment was observed for the interaction of the zymogen with lipid.     

Structural analysis of covalently labeled estrogen receptors by limited proteolysis and monoclonal antibody reactivity

We have used limited proteolysis of affinity-labeled estrogen receptors (ER), coupled with antireceptor antibody immunoreactivity, to assess structural features of ER and the relatedness of ER from MCF-7 human breast cancer and rat uterine cells. MCF-7 ER preparations covalently labeled with [3H]tamoxifen aziridine [( 3H]TAZ) were treated with trypsin (T), alpha-chymotrypsin (C), or Staphylococcus aureus V8 protease prior to electrophoresis on sodium dodecyl sulfate gels. Fluorography revealed a distinctive ladder of ER fragments containing TAZ for each protease generated from the Mr 66,000 ER: for T, fragments of 50K, 38K, 36K, 31K, 29K, and 28K that with longer exposure generated a 6K fragment; for C, fragments of 50K, 38K, 35K, 33K, 31K, 19K, and 18K that with longer exposure generated 14K and 6K fragments; and for V8, ca. 10 fragments between 62K and 28K. Two-dimensional gels revealed charge heterogeneity (two to three spots between pI 5.5 and 6.2) of the 66K ER and the T-generated 28K meroreceptor form. Immunoblot detection with the primate-specific antibody D75P3 gamma revealed that all immunoreactive fragments corresponded to TAZ-labeled fragments but that some small TAZ-labeled fragments (V8-generated forms less than 47K and T-generated forms less than 31K) were no longer immunoreactive. In contrast, use of the antibody H222Sp gamma revealed a correspondence between TAZ-labeled and immunoreactive fragments down to the smallest fragments generated, ca. 6K for T and C and 28K for V8. MCF-7 nuclear and cytosol ER showed very similar digest patterns, and there was a remarkable similarity in the TAZ-labeled and H222-immunoreactive fragments generated by proteolysis of both MCF-7 and rat uterine ER. These findings reveal great structural similarities between the human (breast cancer) and rat (uterine) ER and between nuclear and cytosol ER, indicate charge heterogeneity of ER, and allow a comparison of the immunoreactive and hormone attachment site domains of the ER. The observation that T and C generate a ca. 6K TAZ-labeled fragment that is also detectable with the H222 antibody should be of interest in studies determining the hormone binding domain of the ER and in amino acid sequencing of this region.     

Chemical taxonomy of the hinge-ligament proteins of bivalves according to their amino acid compositions.

The proteins in the hinge ligaments of molluscan bivalves were subjected to chemotaxonomic studies according to their amino acid compositions. The hinge-ligament protein is a new class of structure proteins, and this is the first attempt to introduce chemical taxonomy into the systematics of bivalves. The hinge-ligament proteins from morphologically close species, namely mactra (superfamily Mactracea) or scallop (family Pectinidae) species, showed high intraspecific homology in their compositions. On the other hand, inconsistent results were obtained with two types of ligament proteins in pearl oyster species (genus Pinctada). The results of our chemotaxonomic analyses were sometimes in good agreement with the morphological classifications and sometimes inconsistent, implying a complicated phylogenetic relationship among the species.     

Biological and structural properties of MIP-1 alpha expressed in yeast.

The murine macrophage inflammatory proteins-1 alpha (MIP-1 alpha) and MIP-1 beta are distinct but closely related cytokines. Partially purified mixtures of the two proteins affect neutrophil function and cause local inflammation and fever. The particular properties of MIP-1 alpha have not been well studied, although it has been identified as being identical to an inhibitor of haemopoietic stem cell growth. We have expressed MIP-1 alpha in yeast cells and purified it to sequence homogeneity. Structural analysis of this biologically active material by circular dichroism and fluorescence spectroscopy confirms that MIP-1 alpha has a very similar secondary and tertiary structure to platelet factor 4 and interleukin 8 with which it shares limited sequence homology. The in-vitro stem cell inhibitory properties have been confirmed using a range of murine progenitor cells including purified bone marrow progenitor cells (FACS-1), the FDCP-mix A4 cell line, and spleen colony forming unit (CFU-S) populations. Plateau levels of inhibition of stem cell growth were achieved using concentrations of 0.15 micrograms/ml MIP-1 alpha. We have also demonstrated that MIP-1 alpha is active in vivo: 5 micrograms of MIP-1 alpha per mouse given as a bolus injection, protects stem cells from subsequent in-vitro killing by tritiated thymidine. MIP-1 alpha was also shown to enhance the proliferation of more committed progenitor granulocyte macrophage-colony forming cells (GM-CFC) in response to granulocyte macrophage-colony stimulating factor (GM-CSF).     

An apparatus to measure in vivo biomechanical behavior of dorsi- and plantarflexors of mouse ankle.

We developed an apparatus to quantify the biomechanical behavior of the dorsi- and plantarflexor muscles of the ankle of an anesthetized mouse. When the dorsi- or plantarflexor muscle group is activated by electrical stimulation of either the peroneal or tibial nerve, the apparatus measures the moment developed about the ankle during isometric, isovelocity shortening, or isovelocity lengthening contractions. Displacements may be performed over the full 105 degrees range of ankle motion with an angular resolution of 0.09 degrees. Bidirectional isovelocity ramps in ankle angle up to 1,100 degrees/s are possible and are equivalent to maximum velocities of 2.3 fiber lengths/s (Lf/s) for the fibers in tibialis anterior muscle and 11.9 Lf/s for those in gastrocnemius muscle. During single contractions of the dorsi- and plantarflexor muscle groups at 37 degrees C and with both knee and ankle joint at 90 degrees neutral position, the isometric tetanic force developed was 1.4 and 3.3 N, power output at 2.2 Lf/s was 3.1 and 5.9 mW, and power absorption at 0.5 Lf/s was 4.9 and 9.0 mW, respectively. These values are in reasonable agreement with data from the same muscle groups tested in situ. We conclude that the apparatus provides valid measurements of force and power of the dorsi- and plantarflexor muscle groups.     

Insulin release independent of a rise in cytosolic free Ca2+ by forskolin and phorbol ester

The role of cytosolic free Ca2+ in insulin release was evaluated using isolated rat pancreatic islets permeabilized with digitonin and incubated in Ca-EGTA buffers to fix free Ca2+ concentration at arbitrary levels. Ca2+ induced insulin release in a concentration-dependent manner with the threshold being between 0.1 and 1 microM. The hormone release was increased by forskolin and 12-O-tetradecanoyl phorbol-13-acetate (TPA), a potent activator of adenylate cyclase and that of protein kinase C, respectively. The findings suggest that activation of both protein kinase A and protein kinase C modulate insulin release without a concomitant increase in cytosolic free Ca2+.