Genetic and biochemical studies of the adrenal lipid depletion phenotype in mice

Study of F₁ and backcross progenies from crosses between DBA/2 and strains carrying the adrenal lipid depletion (ald) gene indicated that the adrenal lipid depletion character is due to the operation of two or more interacting gene loci. In C57BL/10, DBA/2, and their F₁ hybrids, variation in adrenocortical sudanophilia was highly correlated with both cholesterol ester content and the capacity for the production of corticosterone in vitro. In F₁×DBA/2 backcross progeny, however, the degree of adrenocortical sudanophilia remained correlated only with cholesterol ester content and not with the capacity for corticosterone production. Thus, in these strains, adrenal cholesterol ester concentration is not necessarily the determining factor of corticosterone production in vitro; the two phenotypic characters are controlled by independent genetic mechanisms.This work was supported by MH 10976 and HD 00801 (U.S.P.H.S.). J.G.M.S. is a recipient of a Wellcome Foundation Travel Grant. R.B.C. is a recipient of U.S.P.H.S. Research Scientist Award K5-47, 413 of the National Institutes of Mental Health.     

The effect of catalase on recovery of heat-injured DNA-repair mutants of Escherichia coli

The apparent sensitivity of Escherichia coli K12 to mild heat was increased by recA (def), recB and polA, but not by uvrA, uvrB or recF mutations. However, addition of catalase to the rich plating medium used to assess viability restored counts of heat-injured recA, recB and polA strains to wild-type levels. E. coli p3478 polA was sensitized by heat to a concentration of hydrogen peroxide similar to that measured in autoclaved recovery medium. The apparent heat sensitivity of DNA-repair mutants is thus due to heat-induced sensitivity to the low levels of peroxide present in rich recovery media. It is proposed that DNA damage in heated cells could occur indirectly by an oxidative mechanism. The increased peroxide sensitivity of heat-injured cells was not due to a decrease in total catalase activity but may be related specifically to inactivation of the inducible catalase/peroxidase (HPI).     

A protective effect of insulin on reperfusing the ischaemic rat heart shown using 31P-NMR

(1) The effect on the recovery of mechanical function, ATP, phosphocreatine, P_i and pH of various lengths of total global ischaemia in the insulin-treated, perfused rat heart has been studied using ³¹P-NMR. (2) Insulin-treated hearts recovered stable mechanical function after 18 min ischaemia when their intracellular pH was 6.0 and 70% of the pre-ischaemic ATP remained. Hearts perfused without insulin fail to recover after 18 min ischaemia, having an intracellular pH of 6.3 and 40% of ATP remaining (Bailey, I.A., Seymour, A.-M.L. and Radda, G.K. (1981) Biochim. Biophys. Acta 637, 1–7). Thus, ATP maintenance in ischaemia is more important to recovery on reperfusion than is maintaining intracellular pH. (3) The importance of this observation in devising biochemical strategies for the clinical protection of the myocardium is discussed.     

Routine metabolic rate of southern bluefin tuna (Thunnus maccoyii).

Routine metabolic rate (RMR) was measured in fasting southern bluefin tuna, Thunnus maccoyii, the largest tuna species studied so far (body mass=19.6 kg (+/-1.9 SE)). Mean mass-specific RMR was 460 mg kg(-1) h(-1) (+/-34.9) at a mean water temperature of 19 degrees C. When evaluated southern bluefin tuna standard metabolic rate (SMR) is added to published values of other tuna species, there is a strong allometeric relationship with body mass (423 M(0.86), R(2)=0.97). This demonstrates that tuna interspecific SMR scale with respect to body mass similar to that of other active teleosts, but is approximately 4-fold higher. However, RMR (not SMR) is most appropriate in ram-ventilating species that are physiologically unable to achieve complete rest. Respiration was measured in a large (250,000 l) flexible polypropylene respirometer (mesocosm respirometer) that was deployed within a marine-farm sea cage for 29 days. Fasted fish were maintained within the respirometer up to 42 h while dissolved oxygen dropped by 0.056 (+/-0.004) mg l(-1) h(-1). Fish showed no obvious signs of stress. They swam at 1.1 (+/-0.1) fork lengths per second and several fed within the respirometer immediately after measurements.     

Preparation and characterization of Ca2+-Zn2+-derivatives of lentil and pea lectins and comparison with the native forms

Ca²⁺-Zn²⁺-derivatives of lentil and pea lectins were prepared for the first time by a unique method involving dialysis of the native Ca²⁺-Mn²⁺-lectins against large excesses of metal ions in pH 4.0 buffer. Each derivative contained about 1.5 g atoms of Ca²⁺ and about 1 g atom of Zn²⁺ per monomer. The derivatives were found to be identical to their respective native forms, both in molecular weight and carbohydrate binding activities. Solvent proton relaxation dispersion measurements were used to characterize both the Ca²⁺-Zn²⁺- and Ca²⁺-Mn²⁺-complexes of the lentil lectin.     

Effect of albumin and polyanion on the structure of DNA complexes with polycation containing hydrophilic nonionic block.

Self-assembling systems based on ionic complexes of DNA with block copolymer of N-(2-hydroxypropyl)methacrylamide with 2-(trimethylammonio)ethyl methacrylate were studied as systems suitable for gene delivery. In this study, the influence of albumin and polyanion on parameters of the DNA polyelectrolyte complexes in aqueous solutions was investigated. Static and dynamic light-scattering methods were used as a main tool for characterizing these interactions. It was found that albumin is not able to release free DNA, but it can rather bind to the complexes forming ternary DNA-polycation-albumin complexes with increased hydrodynamic radii of about 10 nm. Polyanion tested, sodium poly(styrenesulfonate), was able to release free DNA in the presence of a low-molecular-weight electrolyte. In the absence of a low-molecular-weight electrolyte, only formation of ternary complexes and no DNA release was observed. The in vivo biodistribution analysis of DNA complexes showed no effect of the presence of hydrophilic nonionic poly(HPMA) on the circulatory time or organ distribution. The interaction of DNA complexes with albumin and other plasma proteins was suggested to be a major reason for the short circulatory times.     

Accumulation of cyclic AMP in neurohypophyses in response to angiotensin

Angiotensin II (10⁻¹⁰ to 10⁻⁸ M) increases cyclic AMP content in isolated rat neurohypophyses but only when incubated in the presence of theophylline (10⁻² M). The stimulatory effect of 10⁻⁹ M angiotensin II is inhibited by 8-Gly-angiotensin II (10⁻⁷ M) a specific inhibitor of the peripheral effects of the natural octapeptide. The angiotensin antagonist alone did not exhibit any intrinsic effect on cyclic AMP accumulation at the dose used.