The effect of essential-fatty-acid deficiency on the activity of liver phosphatidate phosphatase in rats

The activities of the soluble and microsomal phosphatidate phosphatases (EC 3.1.3.4) are greater in the livers of essential-fatty-acid-deficient rats than in rats fed diets containing linoleic acid.     

Separation of isoacceptor cysteine transfer ribonucleic acids of bakers' yeasts

Summary Isoacceptor species of certain amino acidspecific transfer ribonucleic acids (tRNAs) were fractionated by gel permeation chromatography using Sephadex G-100. The separation is attributed to the 20% ethanol-1% NaCl solvent and to the characteristics of Sephadex. Isoacceptor tRNAs specific for cysteine, arginine, phenylalanine, and histidine were recovered from commercial tRNA of yeast by this method. Highly purified cysteine-specific tRNA, obtained by a method which would not be expected to separate isoacceptor molecules when fractionated by this procedure, was shown to contain two cysteine isoacceptor tRNAs.This investigation was supported in part by Public Health Service Research Grant AM-09131 from the National Institute of Arthritis and Metabolic Diseases.     

The Green's function for the convection-diffusion equation in an analytic lung model

The method of Green's functions is applied to the convection-diffusion equation describing gas transport in the human lung. Explicit analytic solutions are found for the zero^th approximation to the value of steady state alveolar oxygen concentration, given the frequency of breathing, tidal volume, oxygen consumption, alveolar volume, volume of the bronchial tree, and two modelling parameters describing the geometry. The results of the calculation are compared favorably with some experimental data.     

The sub-membrane reticulum of the human erythrocyte: A scanning electron microscope study

A web-like reticulum underlying the human erythrocyte membrane was studied at a resolution of 5–10 nm by means of a scanning electron microscope. The network was visualized in isolated membranes (ghosts) torn open to reveal their interior space and in residues derived from ghosts extracted with Triton X-100. It formed a continuous (rather than patchy) cover over the entire cytoplasmic surface, except where lifted off or torn away. Filaments (5–40 nm in diameter), annular figures (40–60 nm in diameter), and nodes (30–100 nm in diameter) were prominent in different networks. The dimensions of the filaments and the interstices in the reticulum varied with conditions, suggesting that the network has elastic properties. This reticulum is probably related to the erythrocyte membrane proteins spectrin and actin.     

Obstetric flying squad service-a defence.

Eighty-one calls made by the obstetric flying squad in West Berkshire were assessed on the basis of a suggestion that patients would do as well, if not better, if they were brought straight to hospital by ambulance rather than await the arrival of the flying squad. Of the 81 calls, 36 were made to general-practitioner maternity units and 45 were made to patients'' homes. In both groups, the flying squad service was considered to be still of great value. Though slightly slower than an emergency ambulance call, it represents a much safer method of transporting an obstetric patient in an emergency.     

SMITHSONIELLA GEN. NOV., A POSSIBLE EVOLUTIONARY LINK BETWEEN THE MULTICELLULAR AND SIPHONOUS HABITS IN THE ULVOPHYCEAE,CHLOROPHYTA

A low relief, green turf-forming alga of a heterotrichous habit was discovered in the coral reef microcosm, Museum of Natural History, Smithsonian Institution. Erect filaments bore lateral, specialized sporangia and together with basal filaments possessed septal plugs between adjacent cells, grossly similar to the “pit connections” of red algae. Data are presented which: 1) establish the identity of our plant with a plant recently described as Pilinia earleae Gallagher et Humm from the Florida Gulf coast; 2) support our establishment of the new genus Smithsoniella and our transfer of P. earleae to this new taxon. Additional data on pigmentation and cytology are related to the fine structure of other selected green algae to develop and test three hypotheses, viz. Smithsoniella earleae represents either: 1) a symbiotic association between a green and a red alga; 2) an alga which belongs to either the Ulotrichales, Chaetophorales or the Chroolepidales; or 3) an alga representing an evolutionary link between filamentous forms of the Ulvophyceae and members of the coenocytic siphonalean complex (e.g., Codiales or Caulerpales) of the Chlorophyta. Data refute hypotheses 1 and 2 but do lend support to the third hypothesis.     

Affinity labelling and characterization of the ppp(A2'p)nA-dependent endoribonuclease from different mammalian sources

The ppp(A2'p)nA-dependent endoribonucleases from a number of different mammalian sources have been investigated. The enzyme from reticulocyte lysates shows optimal activity of 50-150 mM KCl and requires the presence of Mg2+. Whilst the enzyme is inactivated after passage of reticulocyte lysates through Sephadex columns in the absence of ATP, it retains full activity provided ATP is included in the column buffer. The activity of the partially purified nuclease was unaffected by the addition of reticulocyte RNase inhibitor, which, in contrast, effectively inhibited other endogenous endonucleases. The ppp(A2'p)nA-dependent Rnase co-purified with a ppp(A2'p)nA-binding protein and with a protein which could be specifically covalently labelled with an oxidised radioactive analogue of ppp(A2'p)nA. This covalent labelling could be carried out either with the partially purified RNase or in crude extracts from rabbit reticulocytes, mouse Krebs and Ehrlich ascites tumour cells and human lymphoblastoid (Daudi) or HeLa cells. In each case the affinity labelled protein migrated to a position corresponding to a apparent molecular weight of about 85 000 on electrophoresis on dodecylsulphate/polyacrylamide gels. In all cases labelling could be prevented by the addition of an excess of unlabelled ppp(A2'p)nA but not, for example, by a similar excess of the biologically inactive dimer ppp(A2'p)'A. It is concluded that the RNase and ppp(A2'p)nA binding activities are likely to reside in the same molecule.     

The hypothesized hormonal control of mammalian sex ratio at birth--a second update.

Further evidence is adduced to support the hypothesis that the sexes of mammalian (including human) offspring are partially controlled by parental hormone levels at the time of conception. The evidence relates to variation of sex ratios at birth with (1) time of insemination within the cycle of several species, (2) excision of accessory sex glands in rodents, (3) occupation of parents, (4) dominance rating of human mothers and (5) the ordinal rank of wives in polygynous marriages. Much medical research will stem from the hypothesis if it proves to be true. (a) If it were, there would be implications for the testing of causes of many diseases: and it is noted here that the sex ratios of offspring of victims of two types of cancer (prostatic cancer and non-Hodgkin's lymphoma) are consistent with the suspected causes of these diseases. (b) There are a large number of rheumatic diseases associated with the HLA markers B 27 and B 8. These markers are apparently associated respectively with high testosterone levels in men and low testosterone levels in women. If these finding should be confirmed, a causal role for this hormone seems likely in some of these diseases. It will be interesting to examine sex ratios of relatives of probands with these diseases.     

Linear epitope mapping of an Sm B/B' polypeptide.

Autoantibodies binding the Sm B/B' peptides are commonly associated with SLE. IgG antibodies binding overlapping octapeptides of Sm B/B' have been evaluated in 10 patients with anti-Sm and anti-nRNP precipitins, 5 patients with other autoimmune serology, and 4 normal human sera. Neither normal controls nor patients without an anti-Sm precipitin significantly bind any of the Sm B/B' octapeptides. All sera tested containing an anti-Sm precipitin strongly bind octapeptides from eight regions of the Sm B/B' sequence. Three of these eight regions share the same octapeptide sequences (PPPGMRPP) that are consistently the most immunoreactive octapeptides from Sm B/B'. Binding of the similar PPPGIRGP, as well as binding to deletion and substitution peptides, suggest that the motif PPPG(I,M) (R,K) appears to best define this binding. Interestingly, PAPGMRPP in the nRNP C peptide is as antigenic as PPPGMRPP and may provide a partial explanation for the cross-reactivity shown between Sm and nRNP autoantibodies. However, the sequence, PPPGMIPP, from nRNP A is not antigenic. These data define the linear sequence autoantigenicity of the Sm B/B' protein. They also demonstrate that the predominant autoimmune epitope is a proline-rich sequence from which limited variance is permitted before antigenicity is destroyed.