Sympathetic nerve discharge is coupled to muscle cell pH during exercise in humans.

We used phosphorus nuclear magnetic resonance spectroscopy (31P-NMR) to probe the cellular events in contracting muscle that initiate the reflex stimulation of sympathetic outflow during exercise. In conscious humans, we performed 31P-NMR on exercising forearm muscle and simultaneously recorded muscle sympathetic nerve activity (MSNA) with microelectrodes in the peroneal nerve to determine if the activation of MSNA is coupled to muscle pH, an index of glycolysis, or to the concentrations (II) of inorganic phosphate (Pi) and adenosine diphosphate (ADP) which are modulators of mitochondrial respiration. During both static and rhythmic handgrip, the onset of sympathetic activation in resting muscle coincided with the development of cellular acidification in active muscle. Furthermore, increases in MSNA were correlated closely with decreases in intracellular pH but dissociated from changes in phosphocreatine [( PCr]), [Pi], and [ADP]. The principal new conclusion is that activation of muscle sympathetic outflow during exercise in humans is coupled to the cellular accumulation of protons in contracting muscle.

Metabolic changes in a conidia-induced Claviceps paspali strain during submerged fermentation.

Chemical changes in the mycelium of the conidial Claviceps paspali mutant strain, isolated after gamma irradiation, were followed during the course of submerged fermentation and compared with the mycelial parent strain; both strains are capable of producing simple lysergic acid derivatives. The syntheses of lipids, carbohydrates, phosphates, nucleic acids, proteins, and alkaloids, as well as nutrient uptake, were determined. It was found that conidiation induced by mutagenic treatment was accompanied by a set of changes in the metabolic pattern. In the conidial mutant, the primary and secondary metabolic activities were repressed and the protein to nonprotein compound ratio of the cells was changed in favour of protein compounds.

Mechanisms of adenosine 5'-monophosphate catabolism in human erythrocytes.

Uncertainties regarding the role of pyrimidine nucleotidase (PyrNase) in AMP catabolism were resolved by studies of erythrocytes from normal controls, controls with young mean cell ages, and patients with hereditary hemolytic anemia due to severe deficiency of PyrNase. Hemolysates from the latter exhibited undiminished capacity to dephosphorylate AMP over a broad range of pH, indicating that PyrNase was not directly involved. In each subject group, the rates of AMP dephosphorylation between pH 5.1 and 8.3 were indistinguishable from those of IMP, suggesting a potential role for AMP-deaminase, an erythrocyte enzyme that was stimulated by coformycin at pH 7.2. Quantitative analysis of catabolites in incubated hemolysates confirmed that AMP degradation preferentially occurred via deamination to IMP with subsequent dephosphorylation by another erythrocyte nucleotidase isozyme, deoxyribonucleotidase. Both AMP-deaminase and deoxyribonucleotidase have acidic pH optima with minimal activities at physiologic pH, suggesting that this pathway of AMP catabolism could accelerate depletion of the adenine nucleotide pool and thereby mediate the demise of senescent erythrocytes sequestered in the spleen.

Events in degenerating cat peripheral nerve: induction of Schwann cell S phase and its relation to nerve fibre degeneration.

Severance of a peripheral nerve leads to a characteristic series of events in the distal stump, including the dissolution of axons and myelin and the proliferation of Schwann cells within their basal lamina. This study examines the relationship between the spatial-temporal pattern of the induction of the Schwann cell S phase, loss of the structural and functional properties of axolemma, and the clearance of myelin debris in the cat tibial nerve. Nerve transection stimulated a monophasic increase in [3H]thymidine incorporation that peaked at 4 days post-transection throughout an 80-mm length of distal stump. Light microscope autoradiography revealed prominent incorporation into Schwann cells of myelinated fibres. Treatment of distal stumps with mitomycin C at the time of nerve transection greatly retarded thymidine incorporation and clearance of myelin debris, but not the time course of axonal degeneration, decline in the synthesis of the major myelin glycoprotein, P0, or the onset of ovoid formation. Nerve transection also greatly reduced the specific uptake of [3H]saxitoxin (STX), a ligand which binds to voltage-sensitive sodium channels. Binding in the distal stump fell precipitously to 20% of the normal at 4 days post-transection, concurrent with the peak of thymidine incorporation. This low level of binding was maintained for periods of up to 70 days, demonstrating that some STX binds to structures other than axons in denervated distal stumps. Prior treatment with mitomycin C delayed the loss of specific STX binding. In conclusion, these studies suggest that: Schwann cell DNA replication and/or mitosis regulates other events during Wallerian degeneration, including myelin degeneration, catabolism of P0 and the clearance of sodium channels from nodal axolemma; the decline in P0 synthesis and/or shift to synthesis of less extensively processed P0 is independent of the induction of Schwann cell S phase; and Schwann cells enveloping myelinated axons enter S phase within a 24-h period throughout the entire 80-mm length of distal stump.

[The role of lipids in the regulation of ATP and PPi synthesis in mitochondria]. / Rol' lipidov v reguliatsii sinteza ATP i PPi v mitokhondriiakh.

It was demonstrated previously that mitochondria of higher and lower eukaryotes can synthesize, in the course of oxidative phosphorylation, not only ATP but also inorganic pyrophosphate (PPi). Two PPases were isolated from bovine heart mitochondria (soluble--PPase I and membrane--PPase II). Coupling PPase II, in contrast to PPase I, contains phosphatidyl choline, but PPase I is lipidized readily in the presence of different phospholipids. Reconstitution experiments of the PPi synthesis system have shown that after lipidization PPase I is able to incorporate into submitochondrial particles (SMP) and becomes a coupling factor for oxidation and PPi synthesis. It seems that phospholipid is indispensible for incorporation into the membrane and the manifestation of the coupling activity of the enzyme. The effect of lipids on the activity of soluble and membrane-bound pyrophosphatase was studied. It is shown that PPase II phospholipid is involved in the regulation of the hydrolase activity of the isolated enzyme. However, hydrolysis of PPi by SMP and its synthesis by mitochondria are affected by cooperative rearrangements of the entire lipid component of the membrane rather than by changes in the phase state of phosphatidyl choline contained in PPase II. An opposite response of ATP and PPi synthesis to changes in viscosity makes it likely that the viscosity of the mitochondrial inner membrane may control the levelling of these two processes in mitochondria.

The epididymal microenvironment: a site of attack for a male contraceptive?

During their development, spermatozoa are continually bathed in fluid provided by epithelial secretions of the seminiferous tubule and the epididymal duct. This fluid or microenvironment is probably very important for spermatozoal maturation and survival. Micropuncture and microanalytic studies have revealed the occurrence of several biochemical changes of this specialized microenvironment along the epididymal duct; these changes seem to be linked to sperm maturation. The interactions between maturing spermatozoa and their microenvironment must be understood before interference in sperm maturation through intervention of the formation of the microenvironment is possible. Several compounds have been shown to interfere in spermatozoal maturation in the epididymis although their use as male contraceptives requires further investigation.

PIP: This study reviews some of the functions of the epididymis, and suggests possible sites of attack for a male contraceptive. Microanalytic studies, conducted thanks to the new technique of micropuncture, on the male reproductive tract of animals, have revealed the occurrence of several biochemical changes of the microenvironment along the epididymal tract; this fluid microenvironment continually bathes spermatozoa, and it is fundamental for their maturation and survival. Intervention in this microenvironment could drastically interfere with sperm maturation. Several compounds have been studied or this purpose, but their use as a male contraceptive requires further investigation. Realistically, the probability that a male contraceptive will be marketed within the next decade is slim.

An investigation into the apparent inhibition by arginine phosphate of the activity of Carcinus maenas type-M pyruvate kinase.

An enzymic synthesis utilising arginine kinase for preparing arginine phosphate in a high state of purity is described. The dissociation constant of magnesium arginine phosphate, determined by gel filtration, was 30.0 +/- 0.9 mM. That for potassium arginine phosphate was calculated to be 63.0 +/- 4.0 mM measured by the effect of potassium on the apparent magnesium dissociation constant. The effect of KCl on the reaction catalysed by the type-M pyruvate kinase from Carcinus maenas (the common shore crab) pincer and leg muscle was investigated. No effect was seen on the C. maenas pyruvate kinase activity, apart from that due to alteration of the K+ concentration, on adding up to 70 mM potassium arginine phosphate to the reaction medium. The less pure form of arginine phosphate was found to give an apparent noncompetitive inhibition of the enzyme when phosphoenolpyruvate was the varied substrate. This apparent inhibition can be accounted for by the removal of ADP from the assay medium in a side reaction involving arginine kinase and arginine phosphate. These results are discussed in terms of the possible physiological control of the type-M pyruvate kinase from C. maenas.

Leigh's disease in an adult with evidence of "inhibitor factor" in family members.

A 21-year-old man with a longstanding history of impaired visual acuity, strabismus, broad-based gait, and below-average intellectual capacity developed respiratory difficulties and intermittent generalized weakness at age 19. He subsequently showed signs of massive brainstem dysfunction and died. Postmortem examination demonstrated changes compatible with subacute necrotizing encephalomyelopathy of Leigh involving portions of the diencephalon, midbrain, pons, and medulla as well as portions of the spinal cord and optic nerves. Evaluation of family members for presence of the urinary inhibitor factor for thiamine diphosphate phosphoryl transferase revealed abnormal levels in a brother, a maternal uncle, and the maternal grandfather of the patient.

[Some pathways of biosynthesis and degradation of polyphosphates from green algae Acetabularia mediterranea]. / Nekotorye puti biosinteza i raspada polifosfatov u zelenoi vodorosli Acetabularia mediterranea.

The activity of ATP: polyphosphate phosphotransferase was detected in free-cellular extracts of Acetabularia mediterranea. The enzyme activity in cells originally deficient in phosphorus and subsequently transferred into the phosphate-containing medium increases 5-10-fold as compared to normal. Polyphosphate degradation in A. mediterranea is probably produced by polyphosphatase, which was also detected in the free-cellular extract. It was shown that the polyphosphatase activity has two pH optima, i.e. 4.5 and 7.5, and is considerably increased when the cells are transferred into the phosphate-free medium. It is assumed that high-molecular polyphosphates involved in A. Mediterranea metabolism are responsible for regulation of orthophosphate and ATP level in the cells by ATP: polyphosphate phosphotransferase and polyphosphatase.

[Effect of the light on the biosynthesis of inorganic polyphosphates and some phosphoorganic compounds in Chlorella pyrenoidosa Chick]. / Vliianie sveta na soderzhanie neorganicheskikh polifosfatov i nekotorykh fosfororganicheskikh soedinenii u Chlorella pyrenoidosa Chick

The illumination of Chlorella cells is found to affect the biosynthesis of different inorganic polyphosphates (IPP) and phosphoorganic compounds. The synthesis of IPP fractions, extracted with TCA at 0 degrees C and perchloric acid at 100 degrees C, is carried out with the cooperation of photochemical reactions, while the formation of other IPP fractions is light-independent. Ohosphorus incorporation into nucleic acids and phosphoproteins is due to the effect of the light, and phosphorylation of carbohydrates and phospholipids is a dark process.

Magnesium metabolism: a brief review.

The important role played by the magnesium ion in the body is not generally recognized. The action of numerous enzyme systems critical to cellular metabolism is regulated by it and it contributes importantly to macromolecular structure. Magnesium defiency occurs more often than is generally suspected; magnesium excess, though uncommon, is of special interest to the anaesthetist because it produces a curare-like effect on neuromuscular transmission. It is hoped that this brief review of magnesium metabolism will draw attention to its importance and relevance in everyday practice.

[Polyphosphate biosynthesis in Rhodospirillum rubrum chromatophores]. / O biosinteze polifosfatov v khromatoforakh Rhodospirillum rubrum

The chromatophores of Rhodospirillum rubrum were found to synthesize in the light not only ATP and pyrophosphate but also high molecular weight polyphosphates. Biosynthesis of all studied compounds was inhibited by antimycin A, an inhibitor of the electron-transport photosynthetic chain. Synthesis of high molecular weight polyphosphates is stimulated, while that of pyrophosphate is inhibited, in the conditions providing intensive synthesis of ATP (in the presence of ADP and in the absence of oligomycin). The results obtained suggest that biosynthesis of high molecular weight polyphosphates is related to photosynthetic phosphorylation, via ATP but not pyrophosphate.

Aerobic recovery metabolism following a single isometric tetanus in frog sartorius muscle at 0 degrees C.

1. Basal and recovery O2 consumption, delatO2, in frog sartorius muscles at 0 degrees C were measured with a polarographic electrode. Reproducible observations were made with the same muscle over many hours. 2. The experimental records had an exponential form except for the early phases of recovery following a single isometric tetanus. Diffusion of O2 within the muscle was adequate to account for this deviation from an exponential time course of recovery. The time constant of the recovery O2 consumption increased with the duration of tetanic stimulation from 5 to 20 sec. 3. Lactate synthesis was measureable in unstimulated aerobic muscles and increased in proportion to total O2 consumption as long as the muscle did not lack O2. The contribution of glycolysis to the total chemical energy production during recovery was 6-9%; for hypoxic muscles it was greater. 4. The resynthesis of phosphorylcreatine and the decrease in inorganic phosphate and free creatine following a tetanus showed an exponential time course similar to recovery O2. Initial concentrations were re-attained within 60 min following a 20 sec tetanus. 5. We conclude that recovery O2 consumpation is a useful and accurate measure of the net chemical energy utilization for a single contraction.

Energy metabolism of experimental wounds at various oxygen environments.

Energy metabolism of healing tissue was studied in experimental wounds of rats chronically breathing 11% O2, air or 55% O2. Increasing oxygen supply elevated both PO2 and PCO2 in the wound tissue. At the early phases of healing hypoxic wounds contained less DNA than normoxic or hyperoxic tissues. In hypoxia the accumulation of wound collagen was clearly retarded. Furthermore, tissue taken from wounds healing in hypoxic environments and tested ex vivo in air showed decreased capacity for glucose utilization, lactate production and oxygen consumption. Concentrations of AMP, ADP and ATP in repair tissue increased as healing progressed. The more oxygen available the higher the amounts of ADP and ATP. The AMP content was not affected by changes in local oxygen tension. These results support the earlier concept that the supply of oxygen in healing tissue may be rate-limitimg. Reduction of available oxygen either by systemic hypoxia or by increased diffusion distance impedes healing.

[Possible physiological role of the "high molecular weight polyphosphate-polyphosphate phosphohydrolase" system in Neurospora crassa]. / O vozmozhnoi fiziologicheskoi roli sistemy "vysokomolekuliarnye polifosfaty-polifosfatfosforgidrolaza" u Neurospora crassa

The biosynthesis of polyphosphatase and the system of active transport of glucose is repressed in the cells of Neurospora crassa by glucose at a high concentration. There is a strict correlation between the activity of polyphosphatase and the initial rate of glucose active transport. Both systems are repressed during the growth of the mycelium on a glucose medium and are repaired on a medium without glucose. The latter process is inhibited by cycloheximide. Under various conditions of cultivation, the ratio between the activity of polyphosphatase and the initial rate of active transport of glucose remains close to unity. The experiments with 8-azaadenine have shown that the system of active transport of glucose does not require ATP. A possible physiological role of polyphosphatase in N. crassa is discussed.