Electron paramagnetic resonance studies of membrane proteins in hepatic microsomes

Hepatic microsomal membranes, prepared under various conditions that yield either ‘intact’ or ‘disrupted’ microsomal vesicles, have been labeled via the sulfhydryl groups of intrinsic membrane proteins using nitroxide analogs of $\text{N-}\text{ethylmaleimide}$. Electron paramagnetic resonance spectra revealed the presence of two dominant classes of bound label corresponding to differing degrees of immobilization, the ratio of which were quantitated using a parameter designated the ‘$\text{W/S}$’ ratio. For latent microsomes, the value of this parameter was determined to be $\text{0.65 ± 0.02}$ and was influenced by factors such as label/protein ratio, incubation period, nitroxide structure, temperature and pH. The $\text{W/S}$ ratio was also sensitive to the degree of membrane integrity as revealed by the latency of mannose 6-phosphate activity of glucose-6-phosphohydrolase. In addition, membrane disruption resulted in a corresponding decrease in the order parameter for nitroxide-labeled fatty acids intercalated within the lipid bilayer. The $\text{W/S}$ ratio was observed to be dependent upon the method of microsome preparation yielding values of $\text{1.02 ± 0.02}$ for ‘hypertonically disrupted’ vesicles and $\text{1.28 ± 0.02}$ for ‘mechanically disrupted’ vesicles. Microsomal marker enzymes such as cytochrome $\text{P-450}$ and FAD-containing monooxygenase retained significant levels of functionally following nitroxide incorporation.     

Permeability of bilayer lipid membranes for superoxide (O2) radicals

Egg yolk phosphatidylcholine monolamellar liposomes (1000 Å in diameter) loaded with cytochrome c were placed into an external solution, in which superoxide radicals, O₂⁻, were generated by a xanthine-xanthine oxidase system. The penetration of the superoxide radicals across the liposomal membrane was detected by cytochrome c reduction in the inner liposome compartment. The effects of modifiers and temperature on this process were studied. The permeability of liposomal membrane for O₂⁻(P′_O2⁻ = (7.6 ± 0.3) · 10^-8 cm/s), or HO₂^• (P′_HO2⁻ = 4.9 · 10^-4 cm/s) were determined. The effect of the transmembrane electric potential (K⁺ concentration gradient, valinomycin) on the permeability of liposomal membranes for O₂⁻ were investigated. It was found that O₂⁻ can penetrate across liposomal membrane in an uncharged form. The feasibility of penetration of superoxide radicals through liposomal membrane, predominantly via anionic channels, was demonstrated by the use of an intramolecular cholesterol-amphotericin B complex.     

The binding of selenium to the lipids of two unicellular marine algae

Axenic cultures of the green algae $\text{Dunaliella}\text{primolecta}$ and red algae $\text{Porphyridium}\text{cruentum}$ were grown in the presence of sublethal quantities of selenite. All purified lipids from both algae were found to contain bound selenium, except for saturated hydrocarbons. Of the lipids which contain selenium, carotenoid pigments contain the greatest concentrations. Lipid-associated selenium is not metabolically incorporated. The selenium is probably non-covalently bound to the lipids.     

Organogenesis in callus derived from stem and leaf tissues of apple and cherry rootstocks

Callus formation from stem internodes of the apple rootstocks M.9, M.25, M.26, M.27 and the cherry rootstock Colt, and from pith of Nicotiana tabacum cv. Wisconsin 38 was initiated on 4 -naphthaleneacetic acid (NAA)-based media (2.0–10.0 mg1^-1). Transfer of callus to corresponding media lacking NAA allowed regeneration of shoots from callus of M.25, M.27, Colt and tobacco but not of M.9 and M.26. With M.25 phloroglucinol (PG) depressed regeneration from 30 to 10% and no regeneration was observed in cultures grown in the presence of casein hydrolysate (CH) and glutathione (GSH).Organogenesis was also obtained from leaf discs of M.27 employing 6-benzyl-aminopurine (BAP) at 5.0mg 1^-1 and 2,4-dichlorophenoxy acetic acid (2,4-D) at 0.1 mg1^-1. The regenerated shoots have been multiplied and rooted.Organogenesis also occurred in M.26 from small (1–2mm), green, compact embryoid-like structures derived from stem and leaf surfaces of excised axillary shoots. These structures differentiated into shoots at a low frequency (< 1%) on media containing BAP (1.0mg1^-1) and indole-3-butyric acid (IBA) (0.1 mg1^-1) and could also be micropropagated by subsequent axillary shoot proliferation.     

Localization of corticotropin-releasing factor-containing neurons in the brain of the domestic fowl

Summary The corticotropin-releasing factor (CRF)-containing neurons were investigated in the brain of the domestic fowl by means of the peroxidase-antiperoxidase technique at the light-microscopic level. The detection of CRF-immunoreactivity was facilitated by silver intensification. CRF-containing perikarya were found in the paraventricular, preoptic and mammillary nuclei of the hypothalamus and in some extrahypothalamic areas (nuclei dorsomedialis and dorsolateralis thalami, nucleus accumbens septi, lobus parolfactorius, periaqueductal gray of the mesencephalon, nucleus oculomotorius ventralis). Immunoreactive nerve fibers and terminals were demonstrated in the external zone of the median eminence and the organum vasculosum of the lamina terminalis. These results indicate that an immunologically demonstrable CRF-neurosecretory system also exists in the avian central nervous system.     

An aetiological study of 290 XXY males,with special reference to the role of paternal age

Summary Data on 290 non-mosaic 47,XXY males have been analysed for possible associations with parental ages at birth, season of birth, sex ratio among sibs, and twinning. Comparison with matched population controls revealed a highly significant association with parental age, which was fully explained by dependence on maternal age and maternal age alone. The maternal age effect was determined with greater precision than in an earlier study of the same material, in which siblings were used as controls, and was estimated to result in an increased risk of between 5% and 10% per annum (p.a.). The estimated independent effect of paternal age, after fitting maternal age, was marginally (but not significantly) negative, and excluded an increased risk in excess of 3% p.a. Paternal age therefore appears to have little if any independent significance in the aetiology of 47,XXY. After correcting for seasonal variations in the population birth rate and smoothing, there was a peak of XXY births in March and a trough in November. Though not statistically significant, the pattern resembled that reported in previous studies, and was similar for both younger and older mothers. The twinning rate for both the XXYs and their sibs, and the sex ratio among the latter, were close to the corresponding population values.     

Nucleotide sequence of the VP1 gene of the foot-and-mouth disease virus strain A Venceslau

The VP1 coat protein of FMDV strain A Venceslau (Aven) consists of 213 amino acid residues. Serum neutralization tests demonstrated that strain Aven is closely related to strain A Argentina/79 (A₇₉) but significantly different from strain A₂₄ Cruzeiro (A₂₄). There is a strong correlation between the amino acid sequences and the serological data. Nucleotide and amino acid sequence analyses of VP1 showed that serologically related viruses (Aven and A₇₉) differ less in this region of the genome than those of serologically distinct viruses (Aven vs. A₂₄). The most significant variation between Aven and A₂₄ occurs at amino acid positions 43 to 46, in which all four residues are different.     

Cell interactions during the fusionin vitro ofDrosophila eye-antennal imaginal discs

Summary The fusion of the eye-antennal discs during culturein vitro has been investigated, and the complex morphogenetic movements which occur during the formation of the head capsule of the insect are described. The initial contact between the eye anlagen is by means of cell processes spanning the gap between the two discs. Subsequently the two epithelia become firmly apposed, and then the integrity of the epithelium in the region of fusion breaks down, cells appearing to move to new positions in order to form an epithelium which unites the two discs. The epithelium eventually secretes a pattern of cuticular structures which is continuous between the derivatives of the two discs. Bristles on either side of the line of fusion are perfectly aligned, and structures such as the median ocellus, which are formed jointly by the cells of the two discs, differentiate normally. This is also found when left and right eye-antennal discs of different genotypes are placed side-by-side, indicating that processes of pattern regulation can occur in culture.