Electron transfer reactions of cytochrome c confined within erythrocyte ghosts

We have prepared and characterized resealed erythrocyte ghosts in which the only discernible pigment is cytochrome c. The resealed ghosts have the normal orientation and are free of 'leaky' species; they are stable and can be maintained at 4 degrees C for many days without lysis. The internal cytochrome c participates in redox reactions with both soluble and insolubilized cytochrome c present externally, and with external cytochrome b5. No reaction was observed with plastocyanin, cytochrome c oxidase or NADPH-cytochrome c reductase. A study has been made of the reaction of the internal cytochrome c with the low molecular weight reductants, ascorbate and glutathione. Complex kinetics are observed with both reagents: with ascorbate the results are best explained by assuming the existence, in the membrane, of a redox-active species able to undergo dedimerization. A protein bound disulfide bond would satisfy the requirement.     

Measurement of the rates of protein synthesis in rabbits. A method for the estimation of rates of change in the specific radioactivities of free amino acids during continuous infusions.

1. A method is described by which, from analysis of terminal samples, the rate constants that define the changes in specific radioactivity of free amino acids during continuous infusions can be estimated. The method involves the infusion of 3H-labelled and 14C-labelled forms of an amino acid for different, but overlapping, periods. 2. The procedure was developed for infusions of proline and tyrosine into New Zealand White rabbits and the rate constants were determined for blood and muscle. 3. The rate constant for equilibrium of radioactive free proline was much lower in muscle than in blood, and indicated that a plateau condition may not be attained in muscle by the end of a 6 h infusion. 4. Comparison of the ratio of areas under the curves of estimated specific radioactivity plotted versus time with the 3H/14C ratio of bound amino acid in muscle protein suggested that radioactive proline and tyrosine may be incorporated preferentially from an extracellular rather than an intracellular source.     

The genetic structure of the kuwaiti population II: The distribution of Q-band chromosomal heteromorphisms

Summary The distribution of Q-band heteromorphisms in three Kuwaiti communities is reported. Of particular significance is the finding of large-Y segregating at a very high frequency (61.9%) in the Ajman tribesmen; and the absence of small-Y in the two tribal communities. The large variation in size of the Y-chromosome may reflect a unique cytogenetic feature of the inhabitants of the Arabian peninsula.     

Primary cultures of fetal hepatocytes from the genetically obese Zucker rat: Protein synthesis

Summary Primary fetal hepatocytes derived from Zucker rats with expectedfa gene frequencies of 0.0 and 0.75 have been established and can be used to detect early effects of thefa gene on hepatocellular metabolism. Paired incubation experiments demonstrate that protein synthesis in 0.75fa gene cultures is significantly less than in 0.0fa gene cultures under basal conditions. Insulin stimulates protein synthesis in 0.0fa gene cultures but has no effect on 0.75fa gene cultures. Cycloheximide inhibits protein synthesis in both types of culture. NH₄Cl inhibits protein synthesis in 0.0 but not in 0.75fa gene cultures. These data suggest that fetal hepatocytes bearing thefa gene have in vitro a generally sluggish anabolic capacity and a blunted capacity to respond to insulin compared to fetal hepatocytes without thefa gene. These diminished capacities may be expressions of a genetic error in lysosomal function. A portion of this work was presented in preliminary form at the 1980 meeting of the Tissue Culture Association. This work was supported in part by National Institutes of Health Grants AM19382 and AM06197.     

A putative pathway of glyconeogenesis in skeletal muscle

Evidence is presented in support of a pathway in skeletal muscle of glyconeogenesis (glycogen biosynthesis de novo) from L-glutamate and related amino acids involving the enzyme phosphoenolpyruvate carboxykinase (PEP CK). In the rat hemidiaphragm in vitro, not only did L-[U-¹⁴C]glutamate exert a glycogen-sparing action, but¹⁴C-label was incorporated into glycogen. The incorporation is thought not to be simply via label randomization and was decreased by factors that increased glycolysis or pyruvate oxidation. 3-Mercaptopicolinate and amino-oxyacetate, specific inhibitors of PEP CK and aminotransferase-type enzymes, respectively, decreased¹⁴C-incorporation from L-[U-¹⁴C]glutamate into glycogen. No quantitative determination of apparent glyconeogenic flux was made, and it remains to be established whether glyconeogenesis via PEP CK and/or via PEP CK coupled with 'malic' enzyme (or pyruvate carboxylase) is functionally important in skeletal muscle.     

Failure of X inactivation in the autosomal segment of an X/A translocation.

A newborn with an X/A translocation (46,X,der X,t(X;17)(17pter leads to 17p13::Xp22 leads to Xqter) demonstrated multiple anomalies. X-replication studies in leukocytes of the patient with RBG (R Bands by BrdU using Giemsa stain) showed the abnormal X,t(X;17), to be late replicating except for the translocated segment. Clinical findings and replication studies suggest failure of inactivation of the translocated segment.     

Electrical activity in sympathetic fibres to hind limb muscles of the cat produced by hypothalamic stimulation

Electrical stimulation of the "Defence Area" of the hypothalamus in anaesthetized cats was accomplished by stereotaxic placement of bipolar stainless steel electrodes; the spinal cord was sectioned at L4. The muscle blood flow in one hind limb was recorded with an electromagnetic flowmeter. Increases of between 100% and 300% were observed during hypothalamic stimulation. Electroneurographic recordings from small nerve filaments supplying tibialis anterior muscle revealed two populations of neurones whose activity was abolished by lumbar sympathectomy. It appears that the increased blood flow in skeletal muscle during stimulation of the hypothalamic "Defence Area" is brought about by a simultaneous inhibition of vasoconstrictor activity and increase in cholinergic vasodilator discharge.