Glutamine-containing dipeptides as infusion substrates in the septic state.

Recently a relationship has been postulated between lowered intracellular glutamine concentrations in the skeletal muscle and the rate of protein synthesis. We investigated the effect of 48 hours of parenteral nutrition supplemented with a solution containing glutamine in free or dipeptide form (alanylglutamine or glycylglutamine) on the intracellular glutamine pool in skeletal muscle and on the hind limb exchange of glutamine in dogs with sepsis after surgery. Before surgery, dogs were fasted for 48 hours. We used glutamine dipeptides as sources because they remain stable in an aqueous solution. Nutrition solutions were isocaloric (17.8 kcal/kg body weight/day on day 1 and 35.6 kcal/kg on day 2) and isonitrogenous (0.33 gm nitrogen/kg body weight/day), providing 2.6 mmol/kg body weight/day as glutamine source. During starvation, muscular free glutamine levels decreased by 41% to 10.4 mmol/L (p less than 0.001). On the second postoperative day the dogs had lowered plasma protein levels, a sharp drop in platelet count, an increase in the leukocyte count, and positive blood cultures. None of the solutions investigated in this study was effective in repleting the glutamine pool during 2 days of postoperative nutrition (11 +/- 2.0 mmol/L without glutamine, 10.3 +/- 2.2 mmol/L with glutamine plus alanine, 9.9 +/- 1.6 mmol/L with alanylglutamine, 7.5 +/- 1.1 mmol/L with glutamine plus glycine, and 7.2 +/- 1.2 mmol/L with glycylglutamine, respectively). The release of glutamine from the hindquarter was 631 +/- 38 nmol/kg body weight/min in the control group and decreased significantly in dogs receiving alanylglutamine (13.5 +/- 45 nmol/kg body weight/min; p less than 0.001) or the constituent amino acids (265 +/- 66 nmol/kg body weight/min; p less than 0.01) but was unchanged in dogs receiving glycylglutamine or glutamine plus glycine. We conclude that the duration and dosage of glutamine administration (equivalent to 26 gm glutamine per day in a patient weighing 70 kg) used in this study are not sufficient to restore glutamine deficiency of the skeletal muscle in the depleted state.

Anabolic effects of insulin in growing lambs.

Romney cross-bred wether lambs (aged 16-56 weeks and weighing 16-36 kg) were fed a concentrate diet ad lib. and surgically prepared with catheters in the left and right external iliac arteries and veins, inserted via the ipsilateral medial saphenous artery and vein. Sterile saline was continuously infused through all catheters and after appetite had fully recovered, bovine insulin was infused into one arterial catheter at rates of 5, 10 or 20 mU min-1 for periods of 15, 30 or 45 days in different lambs. At the end of the infusion the lambs were slaughtered to measure the composition of each hindquarter by tissue dissection and chemical analysis. As a result of the insulin infusions, plasma insulin concentrations were increased in venous blood sampled downstream from the infusion site and the arteriovenous concentration differences of glucose were greater across the treated than the contralateral limb. At the 10 and 20 mU min-1 infusion rates, systemic plasma insulin concentrations were increased and glucose concentrations decreased. Pooling results from all the treated lambs showed that intra-arterial insulin infusion increased weight of the hindquarter by 7%, weight of muscle by 5%, weight of dissected fat by 12% and weight of chemical fat by 11% when compared with the contralateral limb. No significant differences were detected among infusion rates or times of infusion. Much of the variation in response between lambs was negatively correlated to their age and/or liveweight when they entered the study. The results demonstrate that tissues in the hindlimb respond to local concentrations of a circulating hormone, provide strong evidence that insulin is an anabolic hormone in the growing postnatal lamb and suggest that such responses diminish with age.

Muscle collagen content in diabetic rats.

Collagen content (mg/dl of dry weight) was measured biochemically in the extensor digitorum longus and the soleus muscle in rats. Comparison of muscles from diabetic (induced by intraperitoneal streptozotocin injection /60 mg/kg body weight/) and non diabetic controls showed an increase in the collagen content of the extensor digitorum longus, and little change in the soleus. The differences did not attain statistical significance indicating that the accelerated collagen ageing attributed to diabetes may not necessarily be true in all tissues.

[Changes in corticosterone and aldosterone concentrations in various tissues of Xenopus laevis tadpoles during the metamorphosis]. / Variations des concentrations en corticostérone et en aldostérone dans divers tissus du têtard de Xenopus laevis pendant la métamorphose.

During the metamorphosis of Xenopus laevis tadpoles, tissue concentrations of corticosterone and aldosterone did not change significantly in forelegs and hindlegs; they increased in tail, liver, skin and intestine. The rise of corticosteroid concentrations appeared in tissues which were deeply transformed during the first part of the climax, when plasma levels of corticosteroids also increased. Highest tissue levels, attained at the mid-climax, were maintained at least until the end of metamorphosis although plasma concentrations of two steroids were then abruptly fallen. Tissues able to retain corticosteroids reacted as Vertebrate "target tissues" and transformations which took place in them could be dependent, at least partially, on corticosteroids.

Subunit composition of rodent isomyosins and their distribution in hindlimb skeletal muscles.

Three adult skeletal muscle sarcomeric myosin heavy chain (MHC) genes have been identified in the rat, suggesting that the expressed native myosin isoforms can be differentiated, in part, on the basis of their MHC composition. This study was undertaken to ascertain whether the five major native isomyosins [3 fast (Fm1, Fm2, Fm3), 1 slow (Sm), and 1 intermediate (Im)], typically expressed in the spectrum of adult rat skeletal muscles comprising the hindlimb, could be further differentiated on the basis of their MHC profiles in addition to their light chain composition. Results show that in muscles comprised exclusively of fast-twitch glycolytic (FG) fibers and consisting of Fm1, Fm2, and Fm3, such as the tensor fasciae latae, only one MHC, designated as fast type IIb, could be resolved. In soleus muscle, comprised of both slow-twitch oxidative and fast-twitch oxidative-glycolytic fibers and expressing Sm and Im, two MHC bands were resolved and designated as slow/cardiac beta-MHC and fast type IIa MHC. In muscles expressing a mixture of all three fiber types and a full complement of isomyosins, as seen in the plantaris, the MHC could be resolved into three bands. Light chain profiles were characterized for each muscle type, as well as for the purified isomyosins. These data suggest that Im (IIa) consists of a mixture of fast and slow light chains, whereas Fm (IIb) and Sm (beta) isoforms consist solely of fast- and slow-type light chains, respectively. Polypeptide mapping of denatured myosin extracted from muscles expressing contrasting isoform phenotypes suggests differences in the MHC primary structure between slow, intermediate, and fast myosin isotypes. These findings demonstrate that 1) Fm, Im, and Sm isoforms are differentiated on the bases of both their heavy and light chain components and 2) each isomyosin is distributed in a characteristic fashion among rat hindlimb skeletal muscles. Furthermore, these data suggest that the ratio of isomyosins in a given muscle or muscle region is of physiological importance to the function of that muscle during muscular activity.

The effects of diltiazem in dystrophic hamsters.

Calcium accumulates in muscles of dystrophic hamsters (DH) and patients with Duchenne muscular dystrophy. Various Ca antagonists were beneficial to the cardiomyopathy of DH, but had only minor effects on skeletal muscle. We administered a new Ca antagonist, diltiazem, 25 mg/kg/day orally to normal and dystrophic hamsters from ages 37 to 92 days. We observed a marked reduction in muscle Ca in DH treated with diltiazem: 73% in the heart, 61% in the diaphragm, and 48% in the rectus femoris. Plasma CK was significantly lower (by 37%) in treated DH, while the elevated rate of noncollagen protein synthesis in the diaphragm was not diminished. Histologically, the most important change was a reduction in Ca deposits in the heart. Diltiazem was well-tolerated by all animals and did not modify Ca content in normal hamsters. This study suggests that diltiazem may have therapeutic value in those conditions that are accompanied by excessive accumulation of Ca in tissues, such as muscular dystrophy.

Requirement for vasoactive amines for production of delayed-type hypersensitvity skin reactions.

The skin sites of the mouse where delayed-type hypersensitivity (DTH) reactions are most easily elicited (foot pads and ears) are particularly rich in 5-hydroxytryptamine (5-HT)-containing mast cells. Since mice are deficient in circulating basophils, which play a role in at least some DTH reactions, we investigated the possibility that the mast cells were playing an important role in the evolution of the skin reactions of DTH in mice. We found that reserpine, a drug which depletes mast cells of 5-HT, abolished the ability of the mouse to make DTH reactions in the skin. The suppressive effect of reserpine could be partially blocked by monoamine oxidase inhibitors which prevent the degradation of 5-HT in the cytosol of the mast cell. Spleen cells of immune, reserpine-treated mice transferred DTH reactions to nonimmune mice normally, indicating that the reserpine treatment did not affect immune T cells. DTH reactions could not be transferred into reserpine-treated mice. We suggest that T cells are continually emigrating from the blood, through postcapillary venule endothelium, by a mechanism which does not depend on vasoactive amines. If they are appropriately immune and meet the homologous antigen in the tissue, they induce mast cells to release vasoactive amines which cause postcapillary venule endothelial cells to separate, allowing the egress from the blood of cells which ordinarily do not recirculate. The secondarily arriving vasoactive amine-dependent cells are responsible for the micro- and macroscopic lesions of DTH reactions. Chemotactic factors may also be involved in bringing cells to the DTH reaction sites but we propose that T-cell regulation of vasoactive amine-containing cells allows the effector cells to pass through the endothelial gates after they are called.

Slow fibers in the frog cruralis muscle.

Extrafusal slow fibers have been identified by electron microscopy in a muscle fiber bundle isolated from the anterior head (m. cruralis) of the triceps femoris of Rana pipiens. Light microscopic examination of this muscle revealed two equally numerous fiber types, one Fibrillenstruktur-like (twitch) and the other structureless (slow). A comparison of force developed by tetanic stimulation and by K+ depolarization also suggested approximately equal numbers of twitch and slow fibers.