Growth and muscle protein turnover in the chick

The growth rates of young chicks were varied from 0 to 10% per day by manipulation of the adequacy of the amino acid and energy supply. The rates of protein synthesis in the white breast (pectoralis thoracica) muscle and the dark leg (gastrocnemius and peronaeus longus) muscles were estimated by feeding l-[U-¹⁴C]tyrosine in amino acid/agar-gel diets (`dietary infusion'). This treatment rapidly and consistently produced an isotopic equilibrium in the expired CO₂ and in the free tyrosine of plasma and the muscles. Wholebody protein synthesis in 2-week-old chicks was estimated from the tyrosine flux and was 6.4g/day per 100g body wt. In 1-week-old chicks the rate of protein synthesis was more rapid in the breast muscles than in the leg muscles, but decreased until the rates were similar in 2-week-old birds. Synthesis was also more rapid in fast-growing Rock Cornish broilers than in medium-slow-growing New Hampshire×Single Comb White Leghorn chicks. No or barely significant decrease in the high rates of protein synthesis, in the protein/RNA ratio and in the activity of RNA for protein synthesis occurred in non- or slow-growing chicks fed on diets deficient in lysine, total nitrogen or energy. Thus the machinery of protein synthesis in the young chick seems to be relatively insensitive to dietary manipulation. In the leg muscles, there was a small but significant correlation between the fractional rate of growth and protein synthesis. A decrease in the fractional rate of degradation, however, appeared to account for much of the accumulation of muscle protein in rapidly growing birds. In addition, the rapid accumulation of breast-muscle protein in rapidly growing chicks appeared to be achieved almost entirely by a marked decrease in the fractional rate of degradation.     

Changes in the surface morphology of the rabbit endometrium related to the estrous and progestational stages of the reproductive cycle

Summary Changes occurring on the surface of the uterine luminal epithelium of the rabbit during the estrous and progestational stages of the reproductive cycle were examined by scanning and transmission electron microscopy. The findings demonstrate that the uterine epithelium, or endometrium, contains two cell types: ciliated cells and nonciliated, microvillous cells. In estrous animals, ciliated cells, although not very numerous, were usually observed in small groups. However, at increasing intervals of time following mating, ciliated cells progressively disappeared from the endometrium until approximately eight to ten days post coitum, when they became scare. From several hours to four to five days following mating, extensive changes occurred on the surfaces of microvillous cells. When observed by TEM, these elements contained organelles typical of cells involved in the synthesis and secretion of glycoproteins. Furthermore, microvillous cells during this period displayed numerous apical protrusions of different sizes and shapes and containing material of varying electron density. Parallel SEM examinations of the same material confirmed the presence of these protrusions. Some of the protrusions appeared as spheroidal masses attached to the cytoplasm by means of a cytoplasmic strand. Other surface masses were clearly unattached to the cell surface and were distributed (1) on the surface of microvillous cells, (2) on the cilia of adjacent ciliated cells, and (3) on the surface of spermatozoa.Changes occurring on the luminal surface during the early postcoital period are interpreted as an expression of morphodynamic processes likely involving coupled secretion (exocytosis) and resorption (endocytosis) of luminal material. The observations presented here also demonstrate that between six and ten days post coitum, the rabbit endometrium contained increasing numbers of enlarged, nonciliated cells that probably arose by the fusion of smaller, microvillous elements.The work reported here was supported by C.N.R. contracts No. CT 760128809 and CT 77014239 (to P.M.) and NIH. Grant HD-04274 (to J.V.B.)     

Changes in cell surface charges during differentiation of isolated micromeres and mesomeres from sea urchin embryos

Changes in the negative surface charge were observed by cell electrophoresis during the differentiation of micromeres and mesomeres isolated from 16-cell-stage sea urchin embryos. Micromeres and mesomeres were separated by a sucrose density gradient column and were cultured in normal seawater. An isolated micromere developed to a cell aggregate, and, at the mesenchyme-blastula stage of control, the aggregate began to scatter into single cells. These processes are quite similar to those of the primary mesenchyme cells in situ. An isolated mesomere, on the other hand, developed into an ectodermal vesicle. At desired stages of development, the cell aggregates which derived from single blastomeres were dissociated into single cells, and their electrophoretic mobilities were measured. It was found that the electrophoretic mobility of the micromere- and mesomere-derived cells concomitantly increased from the early blastula stage up to the early mesenchyme stage. In contrast with the mesomere-derived cells, however, the micromere-derived cells showed another increase in electrophoretic mobility when the cells began to migrate as primary mesenchyme cells. These results show that a correlation exists between the increase in cell surface negative charge and the migration of the primary mesenchyme cells.     

Mammalian collagenase increases in early alcoholic liver disease and decreases with cirrhosis

To determine if alterations in collagen degradation may contribute to the pathogenesis of fibrosis and cirrhosis, we studied the hepatic collagenase activity of 20 baboons given alcohol containing diets or control diets under carefully controlled experimental conditions. We also studied 28 patients whose livers were biopsied for diagnostic purposes. Hepatic collagenase activity was significantly increased in baboons with fatty liver compared to levels in normal, control fed animals [(1.98 +/- 0.19 vs 1.20 +/- 0.08 units (microgram collagen digested/hour/mg liver protein) +/- S.E.M., p less than 0.001)]. The increase in hepatic collagenase activity persisted at the stage of fibrosis when compared to the activity in control baboons (2.16 +/- 0.07 vs 1.20 +/- 0.08 units +/- S.E.M., p less than 0.001). A single cirrhotic baboon available for study had an hepatic collagenase activity of 1.58 units. Patients with hepatic fibrosis had significantly higher hepatic collagenase activity than those with fatty livers [(9.12 +/- 0.94 (n =14) vs 4.52 +/- 0.54 (n = 7) units +/- S.E.M., p less than 0.001)]. However, in the group with cirrhosis, hepatic collagenase was lower [(3.92 +/- 0.61 (n = 7) units +/- S.E.M., p less than 0.001)] than in the group with fibrosis. Our findings suggest that the development of cirrhosis is coincident with, or favored by a failure of hepatic collagen degradative enzymes to keep pace with hepatic collagen synthesis.     

Photochemical reaction of 9-cis-retro-γ-rhodopsin at low temperatures

9-cis-Retro-γ;rhodopsin (λ_max = 420 nm) was prepared from 9-cis-retro-γ-retinal and cattle opsin. After cooling to liquid nitrogen temperature (77 K), the pigment was irradiated with light at 380 nm. The spectrum shifted to the longer wavelengths, owing to formation of a batho product. This fact indicates that the conjugated double bond system from C-5 to C-8 of the chromophoric retinal in rhodopsin was not necessary for formation of bathorhodopsin. Reirradiation of the batho product with light at wavelengths longer than 520 nm yielded a mixture composed of presumably 9- or 11-cis forms of retro-γ-rhodopsin. These three isomers are interconvertible by light at liquid nitrogen temperature. Thus the retro-γ-rhodopsin system is similar in photochemical reaction at 77 K to cattle rhodopsin system. Each system has its own batho product. Based on these results, it was infered that the formation of bathorhodopsin is due to photoisomerization of the chromophoric retinal of rhodopsin and is not due to translocation of a proton on the ring or on the side chain from C-6 to C-8 of the chromophoric retinal to the Schiff-base nitrogen.     

Ultrastructure of intracytoplasmic membranes of Methanomonas margaritae cells grown under different conditions

The development of intracytoplasmic membranes of Methanomonas margaritae cells grown under different culture conditions was studied. Growth on methane was strongly accelerated by the addition of copper ions. Acceleration by copper, however, was not observed in the case of growth on methanol. Cells grown on methane with copper possessed intracytoplasmic membranes along the cell periphery. When the organism was grown in a medium lacking copper, intracytoplasmic membranes appeared as large vesicles surrounded by a unit membrane at the periphery of the cell. The vesicles originated from paired membranes due to the absence of copper in the medium. Cells grown on methanol with or without copper possessed a number of vesicles of different sizes arranged in a chain along the cell periphery. The possible relationship between membrane arrangement and methane oxidation is discussed.     

New fluorogenic substrates for horseradish peroxidase: Rapid and sensitive assays for hydrogen peroxide and the peroxidase

p-Hydroxyphenyl compounds [3-(p-hydroxyphenyl)propionic acid, p-hydroxyphenethyl alcohol, hordenine, p-ethylphenol, 3-(p-hydroxyphenyl)-1-propanol, p-n-propylphenol, and p-hydroxyphenyllactic acid] were recently found to be excellent fluorogenic substrates for the horseradish peroxidase-mediated reaction with hydrogen peroxide. A very rapid and sensitive method for the fluorometric assays of hydrogen peroxide and the peroxidase was established by using 3-(p-hydroxyphenyl)propionic acid as the best of these substrates; hydrogen peroxide can be assayed precisely in amounts as small as 0.1 nmol, with peroxidase activity as low as 7.8 μU.     

Assignment of proximal histidyl imidazole exchangeable proton NMR resonances to individual subunits in hemoglobins A,Boston, Iwate and Milwaukee

The proton nmr spectra of the synthetic valency hybrids, α₂(β⁺CN)₂, (α⁺CN)₂β₂ of hemoglobin A and the natural valency hybrids of the mutant hemoglobins Boston, Iwate and Milwaukee have led to the unambiguous assignment of the two proximal histidyl imidazole exchangeable proton signals at 64 and 76 ppm to individual α and β subunits, respectively. New single non-exchangeable proton resonances detected in the extreme downfield region of the spectra of Hbs Boston and Iwate are tentatively assigned to the coordinated tyrosine of the mutated α chains.     

Ionic currents across pancreatic acinar cell membranes and their role in fluid secretion

Fluid and enzyme secretion from a number of mammalian exocrine glands is controlled by the action of neurotransmitters and hormones on acinar cell membranes. Sustained stimulation evoking sustained fluid and enzyme secretion also evokes sustained membrane depolarization and increase in conductance. Mouse and rat pancreatic fluid and enzyme secretion, as well as membrane depolarization and conductance increase evoked by sustained stimulation with acetylcholine or cholecystokinin-gastrin peptides, are acutely dependent on extracellular calcium. However, the initial stimulant-evoked conductance increase and secretion appear to be triggered by calcium released from inside the cells. Direct measurement of membrane current during sustained stimulation in voltage-clamp experiments with resolution of the total current into its Na, Cl and K components has allowed calculations of stimulant-evoked Na and Cl uptake into the acinar cells. The NaCl uptake is quantitatively sufficient to account for the stimulant-evoked fluid secretion. The role of the stimulant-evoked transmembrane ionic current appears to be the supply of salt for the fluid secretion. Calcium derived from intracellular sources in the initial phase of secretion, and from the extracellular fluid in the sustained phase, couples fluid and enzyme secretion to hormone-receptor interaction.