Comparative biochemistry and physiology最新文献

• 1.

  1. The rates of in vivo conversion of variously labelled glucose, acetate and gluconate to ¹⁴CO₂ by the cockroach (Periplaneta americana) milkweed bug (Oncopeltus fasciatus) and grasshopper (Melanoplus bivittatus) suggest the occurrence of an active pentose cycle and glycolytic-critic acid cycle in these insects.

• 2.

  2. The activitiy of the pentose cycle in the male and female cockroach was quantitated by two independent methods; one based on ¹⁴CO₂ yields from the variously labelled glucose and the other based on the degree of randomization of ¹⁴C between C-1 and C-3 of glucose residues of glycogen when the pentose cycle was challenged with glucose-2-¹⁴C. The results were consistent in that in the male cockroach about 21 per cent and in the female about 3 per cent of the glucose was metabolized by the pentose cycle.

• 3.

  3. About 50 per cent of the glucose in the male cockroach was metabolized by nontriose pathways.

• 4.

  4. The contribution of the pentose cycle was about 18 per cent in the milkweed bug and 38 per cent with the grasshopper.

• 5.

  5. The labelling pattern of the glucose carbon atoms suggests (a) complete equilibrium between glucose-6-P and fructose-6-P in the male but only patial equilibration in the female and (b) that attempts to quantitate the pentose cycle activity through application of equations derived for mammalian tissue suffer interference from the transketolase reaction and from reversal of non-oxidative portions of the pentose cycle.

• 1.

  1. Union ventricle tissue loses potassium and gains sodium in the absence of external potassium. The muscle regions K⁺ and extrudes Na⁺ when returned to potassium-containing medium. Ouabain and 2,4-dinitrophenol, when placed in the pottasium containing medium, inhibit the net movements of both Na⁺ and K⁺.

• 2.

  2. These results suggest that sodium, and possibly potassium, are actively transported. The stoichiometry of potassium and sodium fluxes suggests coupled transport.

• 3.

  3. The rate of unidirectional sodium efflux was reduced by the removal of external potassium, which is consistent with coupled transport of K⁺ and Na⁺.

• 1.

  1. Ammonia production from l-aspartate was studied in liver homogenates from four species of teleosts: Myoxocephalus scorpius, M octodecimspinosus, Pseudopleuronectes americanus and Anguilla rostrata. Liver homogenates from two species of elasmobranchs, Squalus acanthias and Raja erinacea, failed to liberate ammonia from l-aspartate.

• 2.

  2. No ammonia was liberated from l-aspartate in liver homogenates from M. scorpius in the presence of transaminase inhibitors: 4 × 10⁻³ M semicarbizide, 5 × 10⁻³ M isonicotinoyl hydrazide and 4 × 10⁻³ M hydroxylamine.

• 3.

  3. Single subcellular fractions, nuclear, mitochondrial and cytoplasmic, failed to produce ammonia from l-aspartate. However, when mitochondrial and cytoplasmic fractions were combined, ammonia was produced from l-aspartate.

• 4.

  4. The results indicated a transamination reaction is involved in the liberation of ammonia from l-aspartate in teleost liver.

Analyses of the ovalbumins of chicken, turkey and duck show that

• 1.

  1. All three have similar molecular weights and phosphorus contents.

• 2.

  2. The electrophoretic patterns from chicken and turkey are similar and can be related to their phosphorus content.

• 3.

  3. The types of sugars that comprise their oligosaccharides are similar but vary in quantity.

• 4.

  4. Turkey ovalbumin has the most carbohydrate, with substantial amounts of galactose.

• 5.

  5. The amino acid composition of the ovalbumin from chicken more closely resembles that of turkey than that of duck.

• 1.

  1. By means of zone-electrophoresis on cellulose acetate, the haemolymph proteins of Carcinus maenas have been separated into three major components: haemocyanin (fraction-D) a glycoprotein (fraction-I), and a glycolipoprotein (fraction-P). No apohaemocyanin was found.

• 2.

  2. Moulting causes a four- to five-fold decrease in haemocyanin concentration. Premoult levels are progressively restored during the intermoult period. At ecdysis fraction-I disappears completely, and reappears about 10 days later.

• 3.

  3. Bleeding causes a marked increase of the ratio, concentration of fraction-I/concentration of haemocyanin.

• 4.

  4. The concentration of fraction-I is highly dependent on the nutritional status. Starvation causes the complete disappearance of the glycoprotein. During a period of excessive feeding fraction-I accumulates in the blood.

• 1.

  1. Blood pH, pO₂ and pCO₂ values of the unanaesthetized tammar wallaby (Macropus eugenii) were determined at rest, and during moderate and severe heat stress. Values from anaesthetized animals were also obtained.

• 2.

  2. Similarities between the resting values and normal eutherian values are discussed in relation to the lower metabolic rates of marsupials.

• 3.

  3. The respiratory response of the tammar to heat was found to be similar to that of many eutherians. Exposure to moderate heat resulted in the respiratory rate increasing gradually until it stabilised at about 350 breaths/min. During severe heat stress the respiratory rate increased to higher values, and then decreased. The decrease in rate was similar to second-phase breathing as observed in some eutherians.

• 4.

  4. No major changes were observed in the acid-base status of the blood, when the tammar was panting during moderate heat. However during second-phase breathing a respiratory alkalosis occurred, apparently due to the excessive alveolar ventilation.

• 1.

  1. The reflectivity of the furs of two species of desert kangaroo to solar radiation was measured and the effect of season, site on body, and wind speed on their fur insulation was determined.

• 2.

  2. The red kangaroo Megaleia rufa which lives on the exposed open plain has fur which gives greater protection from solar radiation in summer and from heat loss in winter than does that of the euro or hill kangaroo Macropus robustus, which shelters in caves and under rock ledges.

• 3.

  3. The fur insulation of both the kangaroos is similar to that of tropical and temperate zone eutherian mammals, even though they have a much lower basal heat production than eutherians.

• 1.

  1. The amount of urine produced by the crayfish Astacus leptodactylus in fresh water amounts to 4·6 per cent of its fresh weight/24 hr.

• 2.

  2. The amount of water taken in by the gills in the same medium is 4·0 per cent.

• 3.

  3. About 10 per cent of the water taken in penetrates through a surface other than the gills.

• 4.

  4. The area of the fully developed gills is 5·5 cm²/g fresh wt. and the surface of the gill processes amounts to 5·1 cm²/g fresh wt.

• 5.

  5. Water permeability constant calculated for the gill processes amounts to 0·12 μ/sec.

• 1.

  1. The metabolism of (U-¹⁴C) glucose has been studied in isolated muscle from the reptile Uromastix hardwickii.

• 2.

  2. The metabolism of glucose was shown to be qualitatively similar to that found in isolated rat diaphragm muscle but the rate of metabolism was significantly reduced.

• 3.

  3. The influence of lowering the temperature of incubation manifested itself both in the mammalian and reptilian muscle in lowering the rate of glucose catabolism, whereas the effect on glucose incorporation into glycogen and oligosaccharides was not reduced.

• 4.

  4. The reptile muscle showed that there was an increase in the relative concentration of ¹⁴C-maltose accumulating at lower temperature and possible interpretations of this data are discussed.