Book Reviews

Books reviewed in this article:
PHOTOSYNTHESIS BIBLIOGRAPHY , (1976) Volume 7. Edited by Z. SESTAK & J. CATSKY
PHOTOSYNTHESIS AND PLANT DEVELOPMENT . Edited by R. MARCELLE, H. CLUSTERS & M. VAN POUCKE
WORLD SOYBEAN RESEARCH CONFERENCE. II: PROCEEDINGS . Granada Publishing, St Albans, (Sept. 1980) and ABSTRACTS Granada Publishing, St Albans, (Sept. 1980) edited by F REDERICK T. C ORBIN     

Developmental regulation of pectic epitopes during potato tuberisation

We show, by immunogold labelling, that potato (Solanum tuberosum L. cv Karnico) pectic epitopes are developmentally regulated within regions of the stolon, in addition to showing tissue-specific differences in abundance and localisation. The (1-->4)-beta-D-galactan and (1-->5)-alpha-arabinan epitopes demarcate two distinct zones within stolons; galactans are enriched in primary walls of elongating cells proximal to the stolon hook, whilst arabinans predominate in younger cells distal to the hook. Low-methoxyl homogalacturonan epitopes are concentrated in the middle lamella and show a proximo-distal gradient in stolons similar to that of galactans, whilst high-methoxyl homogalacturonan is uniformly abundant. Calcium pectate is restricted to the middle lamella at cell corners and pit fields. Calcium-binding sites are uniformly present in stolon cell walls, but their total density is reduced and they become localised to a few cell corners in mature tubers, as determined by image-electron energy loss spectroscopy. During the transition from elongation growth to isodiametric expansion during tuberisation of the stolon hook, there were no detectable changes in pectic epitope abundance or localisation. As tubers matured, all epitopes increased in abundance in parenchymal cell walls, except for calcium pectate. We conclude that potentially significant changes in pectic composition occur as young cells distal to the stolon hook move into the zone of cell elongation proximal to the hook.     

The permeability of reconstituted liposomes containing the purified lens fiber cell integral membrane proteins MP20, MP26 and MP70

Summary A number of lens fiber cell integral membrane proteins have been localized to junctional regions where they have been proposed to play a role in either mediating or controlling cell-to-cell communication. We have examined the effect of three lens fiber cell membrane proteins, MP20, MP26 and MP70, on the permeability properties of unilamellar phospholipid liposomes. This approach has been previously used to examine the channel-forming properties of MP26. Liposome permeability was determined by measuring the effect of Co²⁺ on the quenching of the fluorescence of N-4-nitrobenzo-2-oxa-1,3 diazole phosphatidyl ethanolamine (NBD-PE)-containing liposomes as described previously by Scaglione and Rintoul (Invest. Ophthalmol. Vis. Sci. 30:961–966, 1989). The effect of all three proteins on liposome permeability was similar. Permeability was dependent on the protein/phospholipid ratio and was not significantly affected by agents known to modify gap junctional permeability in vivo. Glycophorin A, a non-channel-forming integral membrane protein derived from erythrocytes, was also shown to increase the permeability of unilamellar phospholipid liposomes. The ability of a non-channel membrane protein to increase Co²⁺ quenching of NBD-PE-containing liposomes (presumably in a nonspecific manner) indicates that reports describing the permeability of lens membrane protein-containing liposomes should be interpreted with caution in terms of their relationship to cell-to-cell communication.We would like to thank Dr. Rita Meyer for technical assistance with the freeze-fracture electron microscopy, Drs. Wolfgang Baumann and Barbara Malewicz for the purification of bovine lens lipids, and Dr. Gary Nelsestuen for the use of both the fluorescence and photon correlation spectrophotometers as well as for many helpful discussions. This research was supported by NIH grant EY 05684.     

Adolescent smokers seen in general practice: health,lifestyle, physical measurements,and response to antismoking advice.

OBJECTIVE--To compare physical, lifestyle, and health characteristics of adolescent smokers and non-smokers and their initial response to anti-smoking counselling. DESIGN--Adolescents aged 13, 15, and 17 years were identified from age-sex registers and invited by letter for a general practice health check. SETTING--Three general practices in the MRC general practice research framework. MAIN OUTCOME MEASURES--Blood pressure, body mass index, saliva cotinine concentration, peak flow rate, alcohol consumption, exercise, duration of sleep, and stated persistent health problems. RESULTS--73% of the adolescents (491) attended for the health check. A total of 68 (14%) were regular smokers. By age 17 those who smoked regularly had a significantly lower systolic blood pressure than those who had never smoked regularly (by 6 mm Hg; p = 0.025) despite a significantly higher body mass index (by 1.5; p <0.001) [corrected]. Cotinine concentrations increased with smoking exposure, from 0.7 ng/ml when no family member smoked to 155 ng/ml in active smokers of six or more cigarettes a week. Significantly more regular smokers than never regular smokers drank greater than or equal to 8 g alcohol a day (chi 2 = 15.2 adjusted for age and sex p less than 0.001); regular smokers exercised less (1.0 hrs/week in boys and 0.8 hrs/week in girls v 3.4 hrs/week in boys and 2.2 hrs/week in girls; p less than 0.001) and slept less (8.0 hrs/night v 8.5 hrs/night at age 17; p less than 0.005). Persistent health problems, mostly asthma or allergic symptoms, were reported by 25% (17/68) of the smokers and 16% (60/381) of the non-smokers. Of the smokers given counselling, 60% (26/43) made an agreement with the practice doctor or nurse to give up smoking. CONCLUSION--General practice is an appropriate setting for adolescents to receive advice on healthy lifestyle, which should not focus solely on smoking.     

Role of glycosylation in the transport of recombinant glycoproteins through the secretory pathway of lepidopteran insect cells

Cell lines established from the Lepidopteran insect Spodoptera frugiperda (e.g., Sf9) are used routinely as hosts for the expression of foreign proteins by baculovirus vectors. Previously, we showed that human tissue plasminogen activator (t-PA) was expressed, N-glycosylated, and secreted by Sf9 cells infected with a recombinant baculovirus (Jarvis DL, Summers MD: Mol Cell Biol 9:214-223, 1989). We also showed that t-PA secretion was blocked by tunicamycin (TM), an inhibitor of N-glycosylation, but not by castanospermine (CS) or N-methyldeoxynojirimycin, inhibitors of the initial steps in N-linked oligosaccharide processing. This suggested that the addition, but not the processing, of N-linked oligosaccharides is required for the secretion of recombinant t-PA from baculovirus-infected Sf9 cells. In this study, we present a more generalized evaluation of the role of N-glycosylation in the transport of recombinant glycoproteins through the Sf9 cell secretory pathway. Several different secretory or membrane-bound glycoproteins were expressed in control, TM-treated, or CS-treated Sf9 cells, and their appearance in the medium or on the cell surface was measured. The results showed that TM blocked the transport of some, but not all, of these proteins, whereas CS did not block the transport of any. This suggests that N-glycosylation is sometimes required for the transport of recombinant glycoproteins through the Sf9 secretory pathway, while processing of the oligosaccharides is not. At least two other proteins, p80 and p31, consistently coimmunoprecipitated with the nonglycosylated precursors of recombinant glycoproteins expressed in TM-treated Sf9 cells. Neither was antigenically related to any of the recombinant proteins. Relatively larger amounts of p80 and p31 were coprecipitated when transport was completely blocked by TM compared to when transport was only reduced or was unaffected. These results suggest that p80 and p31 block the transport of some nonglycosylated glycoprotein precursors in TM-treated Sf9 cells by binding to them and producing transport-incompetent heterooligomeric complexes. If this speculation is correct, then p80 and p31 are functionally analogous to the mammalian immunoglobulin heavy chain binding/glucose-regulated 78 kilodalton protein (BiP/GRP78).     

Zooplankton feeding on size fractionated Microcystis colonies and Chlorella in a hypertrophic lake (Hartbeespoort Dam, South Africa): implications to resource utilization and zooplankton succession

A line of text on p. 1246 was mistakenly substituted after pageproof stage. Line 21 should read: 1986). Pace et al. (1983)demonstrated that Ceriodaphnia efficiently utilizes and sur-