Effect of Er,Cr:YSGG Laser at Different Output Powers on the Micromorphology and the Bond Property of Non-Carious Sclerotic Dentin to Resin Composites

Background

The objective of this study was to investigate the influence of Er,Cr:YSGG laser irradiated at different powers on the micromorphology and the bonding property of non-carious sclerotic dentin to resin composites.

Methods

Two hundred bovine incisors characterized by non-carious sclerotic dentin were selected, and the seventy-two teeth of which for surface morphological analysis were divided into nine groups according to various treatments (A: the control group, B: only treated with the adhesive Adper Easy One, C: diamond bur polishing followed by Adper Easy One, D-I: Er,Cr:YSGG laser irradiating at 1W, 2W, 3W, 4W, 5W, 6W output power, respectively, followed by Adper Easy One). The surface roughness values were measured by the non-contact three-dimensional morphology scanner, then the surface micromorphologies of surfaces in all groups were assessed by scanning electron microscopy (SEM); meanwhile, Image Pro-Plus 6.0 software was used to measure the relative percentage of open tubules on SEM images. The rest, one hundred twenty-eight teeth for bond strength test, were divided into eight groups according to the different treatments (A: only treated with the adhesive Adper Easy One, B: diamond bur polishing followed by the above adhesive, C-H: Er,Cr:YSGG laser irradiating at 1 W, 2 W, 3 W, 4 W, 5 W, 6 W output power, respectively, followed by the above adhesive), and each group was subsequently divided into two subgroups according to whether aging is performed (immediately tested and after thermocycling). Micro-shear bond strength test was used to evaluate the bond strength.

Results

The 4W laser group showed the highest roughness value (30.84±1.93μm), which was statistically higher than the control group and the diamond bur groups (p<0.05). The mean percentages ((27.8±1.8)%, (28.0±2.2)%, (30.0±1.9)%) of open tubules area in the 4W, 5W, 6W group were higher than other groups (p<0.05). The 4W laser group showed the highest micro-shear bond strength not only in immediately tested (17.60±2.55 PMa) but after thermocycling (14.35±2.08MPa).

Conclusion

The Er,Cr:YSGG laser at 4W power can effectively improve the bonding property between non-carious sclerotic dentin and resin composites by increasing the roughness and mean percentage area of open tubules.     

A critical evaluation of HL-A phenotype and genotype frequencies in a large German population determined by platelet complement fixation and lymphocytotoxicity

Summary 1047 healthy, random blood donors were typed independently for HL-A antigens by platelet complement fixation and lymphocytotoxicity. The results of both methods were analyzed statistically and the gene frequencies calculated. The gene frequencies were: first HL-A locus: 1: 0.1277–0.1316; 2: 0.3018–0.3053; 3: 0.1411–0.1456; 9: 0.1061–0.1088; 10: 0.0540–0.0564; 11: 0.0381–0.0416; W28: 0.0096–0.0271; W32: 0.0365–0.0469; second HL-A locus: 5: 0.0613–0.0649; 7: 0.1367–0.1401; 8: 0.0716–0.0920; 12: 0.0383–0.0903; 13: 0.0357–0.0371; W5: 0.0786–0.0844; W10: 0.0594–0.0620; W14: 0.0280–0.0315; W15: 0.0650–0.0722; W17: 0.0399; W18: 0.0241–0.0374; W22: 0.0037–0.0161; W27: 0.0406–0.0532; W21: 0.0329–0.0428. The discrepancies of typing results are discussed and their practical importance for paternity serology is stressed.Supported by the Deutsche Forschungsgemeinschaft (Mu 277/5).     

重组人粒细胞集落刺激因子缓释微球的研究

目的：研究固体／油／水法制备重组人粒细胞集落刺激因子缓释微球,为开发其缓释剂型进行初步研究。方法：以聚乳酸．聚羟乙酸共聚物（PLGA）为载体材料：用固体／油／水法和水／油／水法制备载rhG-CSF缓释微球;考察粒径大小、外观、包封率等理化性质;用MieroBCA法考察微球的体外释药特性及影响因素;用SEC-HPLC和MTT比色法初步评价了微球制备工艺过程对rhG-CSF稳定性的影响。结果：两种方法制得的微球形态圆整、分散性良好,包封率均超过80％。固／油／水法制得的微球体外释放在2周内可超过90％,而水／油／水法制得的微球在相同的时间内仅释放30％。对于固／油／水法制备过程,SEC-HPLC法测定蛋白无明显聚集体出现,MTT法测定蛋白活性无明显损失。结论：实验证明了固／油／水法制备的PLGA微球可以实现2周以上的体外缓释。     

Role of the N-terminal polycystic kidney disease domain in chitin degradation by chitinase A from a marine bacterium, Alteromonas sp. strain O-7

AIMS: The aim of study was to clarify whether the polycystic kidney disease (PKD) domain of chitinase A (ChiA) participates in the hydrolysis of powdered chitin. METHODS AND RESULTS: Site-directed mutagenesis of the conserved aromatic residues of PKD domain was performed by PCR. The aromatic residues, W30, Y48, W64 and W67, were replaced by alanine, and single- and double-mutant chitinases were produced in Escherichia coli XL10 and purified with HisTrap column. Single mutations were not quite effective on the hydrolysing activities against chitinous substrates when compared with wild-type ChiA. However, mutations of W30 and W67 decreased the activities against powdered chitin by 87.6%. Wild-type and mutant PKD domains were produced in E. coli TOP10 and purified with glutathione-Sepharose 4B column. Wild-type PKD domain showed significant binding activity to powdered chitin, whereas mutations of W30 and W67 reduced the binding activity to powdered chitin drastically. These results suggest that PKD domain of ChiA is essential for effective hydrolysis of powdered chitin through the interaction between two aromatic residues and chitin molecule. CONCLUSIONS: PKD domain of ChiA participates in the effective hydrolysis of powdered chitin through the interaction between two aromatic residues (W30 and W67) and chitin molecule. SIGNIFICANCE AND IMPACT OF THE STUDY: The findings of this study provide important information on chitin degradation by microbial chitinases.     

Photographic methods for observation of the eye-fundus of rhesus monkeys (author's transl)]

The method for observing the eye-fundus of rhesus monkeys was devised by the use of Kowa RC-2 Hand-held Fundus Camera. 1. For monochrome photography, Fuji Neopan F (ASA 32) and Fuji Neopan SS (ASA 100) films were used. The best result was obtained under the following conditions : the Strong Power Pack "50W" X 6 for Neopan F and "50W" X 3 for Neopan SS. 2. For color photography, Fuji Color (ASA 100 : Negative, Positive) and Sakura Color (ASA 100 : Negative) films were used. The best result were obtained under the following conditions : the Strong Power Pack "50W" X 2 for Fuji Color (ASA 100 : Negative), "50W" X 3 for Fuji Color (ASA 100 : Positive) and "50W" X 3 for Sakura Color. 3. Four fluorescein angiography, 0.3ml/kg of 10% sodium fluorescein was injected into the vein, and then photographs were taken under the condition of "100W" X 6. For monochrome photography (Kodak Tri-X ASA 400 : Negative), a combination of Kodak Wratten Filter 47 (excitor) X K. W. 15 (barrier) brought about the best photographic result. FOR COLOR PHOTOGRAPHY (Kodak Ektachrome High Speed ASA 160 : Positive), the filters (K. W. 32 X K. W. 56, K. W. 47 A X K. W. 12 . 15, K. W. 47 X K. W. 12 . 15 and Fuji Filter BPB 45 X BPB 55) were used and the films were developed by a double sensitivity method to obtain the best photograph.     

Book reviews

Book reviews in this article: Fauna of Australia. Vol. IB. Mammalia Edited by D. W. Walton and B. J. Richardson. Plant Physiological Ecology: Field Methods and Instrumentation Edited by R. W. Pearcy, J. Ehleringer, H. A. Mooney and P. W. Rundel. Fire in the Tropical Biota: Ecosystem Processes and Global Challenges Edited by J. G. Goldammer. Nature Conservation 2: The Role of Corridors Edited by D. A. Saunders and R. J. Hobbs.     

Untersuchungen zur ernährungsphysiologischen Bedeutung von NPN-Verbindungen

The aims of the experiment were to investigate the variation in ruminal fermentation, milk performance and milk fatty acid profile triggered by induced subacute ruminal acidosis (SARA); and to evaluate the ability of beet pulp (BP) as a replacement for ground maize in order to alleviate SARA. Eight Holstein-Friesian cows were fed four diets (total mixed rations) during four successive periods (each of 17 d): (1) without wheat (W0); (2) with 10% finely ground wheat (FGW) (W10); (3) with 20% FGW (W20); (4) with 20% FGW and 10% pelleted BP (BP10). Inducing SARA by diet W20 decreased the daily mean ruminal pH (6.37 vs. 5.94) and the minimum ruminal pH (5.99 vs. 5.41) from baseline to challenge period. Ruminal concentrations of total volatile fatty acid, propionate, butyrate, valerate and isovalerate increased with the W20 compared with the W0 and W10 treatments. The substitution of BP for maize increased the minimum ruminal pH and molar percentage of acetate and decreased the molar percentage of butyrate. The diets had no effect on dry matter intake (DMI) and milk yield, but the milk fat percentage and yield as well as the amount of fat-corrected milk was reduced in the W20 and BP10 treatments. The cows fed the W20 diet had greater milk concentrations of C11:0, C13:0, C15:0, C14:1, C16:1, C17:1, C18:2n6c, C20:3n6, total polyunsaturated fatty acids (FA) and total odd-chain FA, and lower concentrations of C18:0 and total saturated FA compared with the cows fed the W0 diet. Therefore, it can be concluded that changes in ruminal fermentation, milk fat concentration and fatty acid profile are highly related to SARA induced by feeding high FGW diets, and that the substitution of BP for maize could reduce the risk of SARA in dairy cows.     

Hemin Regulation of Hemoglobin Binding by Porphyromonas gingivalis

Hemoglobin binding to chemostat-grown hemin-excess and hemin-limited cells of Porphyromonas gingivalis W50, and to cells of the avirulent, beige-pigmenting variant W50/BE1, was quantified. Hemin-excess W50 bound more hemoglobin than hemin-limited W50, mirroring the hemin-binding ability of these cells [Microb Ecol Health Dis 7:9–15, 1994]. In contrast to hemin, hemoglobin binding was not enhanced by sodium dithionite. The hemoglobin-binding capacity of hemin-excess W50/BE1 was below that of hemin-limited W50 and only observed under oxidizing conditions. Scatchard analysis revealed similar affinity constants for hemin-excess and hemin-limited W50, and confirmed a lower binding maximum for the latter. Hemin-excess W50/BE1 displayed cooperative binding of hemoglobin. These differences in binding were reflected in the binding of a horse radish peroxidase-conjugated hemoglobin (HHRPO) in a dot-blot assay. However, neither the 32-kDa hemin-binding protein, nor its 19-kDa heat-modified form, from either hemin-limited W50 or hemin-excess W50/BE1, bound this conjugate. These data indicate that hemoglobin binding by P. gingivalis is hemin-regulated and occurs via a mechanism different from hemin binding. Received: 2 June 1997 / Accepted: 4 August 1997     

Book reviews

THE BIOLOGY OF MOSSES. by D. H. S. R ichardson
PRINCIPLES OF GENETIC MANIPULATION: AN INTRODUCTION TO GENETIC ENGINEERING . By R. W. O ld & S. B. P rimrose Second Edition
HANDBOOK OF PLANT VIRUS INFECTIONS: COMPARATIVE DIAGNOSIS . Edited by E douard K urstak .
CYTOGENETICS . By J urgen S chulz -S chaeffer
PLANT SCIENCE: AN INTRODUCTION TO WORLD CROPS . By J. J anick , R. W. S chery , F. W. W oods , & V. W. R uttan     

Book reviews

Book reviewed in this article:
M icroalgae (1994) By E.W. Becker.
T he E volutionary B iology of V iruses (1994). Edited by S.S. Morse.
MCQ s in M edical M icrobiology and I nfectious D iseases (1993). By P.W. Ross and F.X.S. Emmanuel.
T uberculosis : B ack to T he F uture (1994). Edited by J.D.H. Porter and K.P.W. McAdam.
M aking S afe F ood : A M anagement G uide for M icrobiological Q uality (1991). By W.F. Harrigan and R.W.A. Park.
B acterial P rotein T oxins : FEMS S ymposium No. 73. (1994). Edited by J. Freer, R. Aitken, J.E. Alouf, G. Boulnois, P. Falmagne, F. Fehrenbach, C. Montecucco     

Effects of standing vs. seated posture on repeated Wingate performance

Standing during cycling may increase overall muscular activity. However, effects of standing vs. seated posture on performance measures during repeated bouts have not been extensively explored. The purpose of this study was to examine the effects of standing vs. seated posture on repeated Wingate performance. Healthy volunteers (n = 35) performed 3 consecutive Wingate anaerobic power tests (W(1), W(2), W(3)) in a standing (STA) as well as seated (SIT) posture. Within-group comparisons were made for peak power, mean power, minimum power, and fatigue index. Results were considered significant at p < or = 0.05. No significant differences were found for peak power in W(1), W(2), or W(3). No significant difference was found for mean power in W(1) or W(2), but significant differences were found for mean power in W(3) (STA: 451.5 +/- 105.3, SIT: 425.7 +/- 110.0); minimum power in W(1) (STA: 433.6 +/- 100.8, SIT: 381.5 +/- 96.9), W(2) (STA: 348.1 +/- 112.9, SIT: 308.0 +/- 95.8), W(3) (STA: 292.0 +/- 103.6, SIT: 265.3 +/- 90.8); and fatigue index: W(1) (STA: 51.3 +/- 10.7, SIT: 56.9 +/- 9.3), W(2) (STA: 56.5 +/- 12.6, SIT: 61.8 +/- 12.2), W(3) (STA: 59.4 +/- 13.1, SIT: 63.6 +/- 12.4). Results suggest that a standing posture enhances performance during repeated Wingate cycling. The enhancement is most likely due to an attenuated loss in power, which in turn improves fatigue index.     

Er,Cr:YSGG激光处理正常及龋坏牙本质的扫描电镜观察

目的：利用扫描电镜观察Er,Cr：YSGG激光处理龋坏牙本质的形态学改变,并与常规方法进行比较。方法：将24颗新拔除的患龋牙随机分成2组,每组12颗牙。第1组常规处理组：分别用金刚砂石针、碳钢裂钻和挖器处理正常及龋坏牙本质;第2组激光处理组：分别用2WEr,Cr：YSGG激光、4WEr,Cr：YSGG激光处理正常及龋坏牙本质。常规制片,扫描电镜下观察。结果：与常规方法相比,激光处理后的牙本质表面不平,呈鱼鳞状、片状的粗糙外观;表面清洁,无玷污层,牙本质小管口清晰可见;4W激光作用时偶见微裂;激光处理后的牙本质表面具有增加树脂黏结性的形态学改变．结论：Er,Cr：YSGG激光能有效地清除龋坏牙本质及玷污层,并可使牙体组织发生一定的形态学改变。因此,Er,Cr：YSGG激光能够替代常规去龋备洞方法。     

Book Reviews

Book reviewed in this article:
REPRODUCTIVE BEHAVIOUR OF INSECTS. Edited by W. J. Bailey and J. Ridsdill-Smith
THE ACARI: REPRODUCTION, DEVELOPMENT AND LIFE-HISTORY STRATEGIES. Edited by Reinhart Schuster and Paul W. Murphy     

Clenbuterol, a β2-adrenergic agonist, reciprocally alters PGC-1 alpha and RIP140 and reduces fatty acid and pyruvate oxidation in rat skeletal muscle

Clenbuterol, a β2-adrenergic agonist, reduces mitochondrial content and enzyme activities in skeletal muscle, but the mechanism involved has yet to be identified. We examined whether clenbuterol-induced changes in the muscles' metabolic profile and the intrinsic capacity of mitochondria to oxidize substrates are associated with reductions in the nuclear receptor coactivator PGC-1 alpha and/or an increase in the nuclear corepressor RIP140. In rats, clenbuterol was provided in the drinking water (30 mg/l). In 3 wk, this increased body (8%) and muscle weights (12-17%). In red (R) and white (W) muscles, clenbuterol induced reductions in mitochondrial content (citrate synthase: R, 27%; W, 52%; cytochrome-c oxidase: R, 24%; W, 34%), proteins involved in fatty acid transport (fatty acid translocase/CD36: R, 36%; W, 35%) and oxidation [β-hydroxyacyl CoA dehydrogenase (β-HAD): R, 33%; W, 62%], glucose transport (GLUT4: R, 8%; W, 13%), lactate transport monocarboxylate transporter (MCT1: R, 61%; W, 37%), and pyruvate oxidation (PDHE1α, R, 18%; W, 12%). Concurrently, only red muscle lactate dehydrogenase activity (25%) and MCT4 (31%) were increased. Palmitate oxidation was reduced in subsarcolemmal (SS) (R, 30%; W, 52%) and intermyofibrillar (IMF) mitochondria (R, 17%; W, 44%) along with reductions in β-HAD activity (SS: R, 17%; W, 51%; IMF: R, 20%; W, 57%). Pyruvate oxidation was only reduced in SS mitochondria (R, 20%; W, 28%), but this was not attributable solely to PDHE1α, which was reduced in both SS (R, 21%; W, 20%) and IMF mitochondria (R, 15%; W, 43%). These extensive metabolic changes induced by clenbuterol were associated with reductions in PGC-1α (R, 37%; W, 32%) and increases in RIP140 (R, 23%; W, 21%). This is the first evidence that clenbuterol appears to exert its metabolic effects via simultaneous and reciprocal changes in the nuclear receptor coactivator PGC-1α and the nuclear corepressor RIP140.     

Phosphoglucomutase phenotyping among Chinese in Taiwan.

Phosphoglucomutase 1 (PGM1) phenotyping was performed in 1,128 Chinese blood donors by thin-layer isoelectric focusing on agarose. The PGM1 gene frequencies were as follows: 1A, 0.6005; 1B, 0.1500; 2A, 0.1510, 2B, 0.0973; variants, 0.0058, with W21, 0.0040. The variants found in this series were PGM1 W21, W2, W3, W6 and W9 (or W10) with PGM1 W21 being the most common variant among Chinese, having a phenotype frequency of 0.8%.     

The isolation and microbial community analysis of hydrogen producing bacteria from activated sludge

AIMS: To profile the fractions of bacteria in heat-treated activated sludge capable of producing hydrogen and subsequently to isolate those organisms and confirm their ability to produce hydrogen. METHODS AND RESULTS: Profiling the community composition of the microflora in activated sludge using 16S rRNA gene-directed polymerase chain reaction-denaturing gradient gel electrophoresis suggested that a majority of bacteria were various Clostridium species. This was confirmed by clone library analysis, where 80% of the cloned inserts were Clostridium sp. A total of five isolates were established on solid media. Three of them, designated as W1, W4 and W5, harboured the hydrogenase gene as determined by PCR and DNA sequence analysis (99% similarity). These isolates were similar to Clostridium butyricum and Clostridium diolis as determined by 16S rRNA gene sequence. A maximum hydrogen production yield of 220 ml H(2) g(-1) glucose was achieved by W5, which was grown on improved mineral medium by batch fermentation without pH adjustment and nitrogen sparging during fermentation. Accumulation of malic acid and fumaric acid during hydrogen fermentation might lead to higher hydrogen yields for W4 and W5. W1 is the first reported Clostridium species that can tolerate microaerobic conditions for producing hydrogen. CONCLUSION: Clostridium species in heat-treated activated sludge were the most commonly identified bacteria responsible for hydrogen production. Specific genetic markers for strains W1, W4 and W5 would be of great utility in investigating hydrogen production at the molecular level. Two previously described primer sets targeting hydrogenase genes were shown not to be specific, amplifying other genes from nonhydrogen producers. SIGNIFICANCE AND IMPACT OF THE STUDY: Clostridium species isolated from heat-treated activated sludge were confirmed as hydrogen producers during dark hydrogen fermentation. The isolates will be useful for studying hydrogen production from wastewater, including the process of gene regulation and hydrogenase activity.     

W::Neo: a novel dual-selection marker for high efficiency gene targeting in Drosophila

We have recently developed a so-called genomic engineering approach that allows for directed, efficient and versatile modifications of Drosophila genome by combining the homologous recombination (HR)-based gene targeting with site-specific DNA integration. In genomic engineering and several similar approaches, a "founder" knock-out line must be generated first through HR-based gene targeting, which can still be a potentially time and resource intensive process. To significantly improve the efficiency and success rate of HR-based gene targeting in Drosophila, we have generated a new dual-selection marker termed W::Neo, which is a direct fusion between proteins of eye color marker White (W) and neomycin resistance (Neo). In HR-based gene targeting experiments, mutants carrying W::Neo as the selection marker can be enriched as much as fifty times by taking advantage of the antibiotic selection in Drosophila larvae. We have successfully carried out three independent gene targeting experiments using the W::Neo to generate genomic engineering founder knock-out lines in Drosophila.     

Phosphoglucomutase-1 polymorphism among Chinese in Taiwan.

Phosphoglucomutase-1 (PGM1) phenotyping of 1,128 Chinese blood donors was performed by thin-layer isoelectric focusing on agarose. The PGM1 gene frequencies were: 1A, 0.6005; 1B, 0.1500; 2A, 0.1510; 2B, 0.0973, and rare variants, 0.0058. The rare variants found in this series were PGM1 W21, W2, W3, W6 and W9 (or W10) with PGM1 W21 being the most common variant among Chinese with a phenotype frequency of 0.8%.     

Interrelationships between plasma insulin-like growth factor-I (IGF-I) concentrations and plasma sex hormone levels in the growing male guinea-pig.

The aim of the present study was to determine the influence of androgens on Insulin-like Growth Factor-I (IGF-I) release at puberty in male guinea-pigs. After the animals were orchiectomised (CX) or sham-operated (SO) at the end of weaning, plasma testosterone (T), dihydrotestosterone (DHT) and IGF-I levels were measured by RIA at the 4th (W4), 8th (W8) and 12th (W12) week after delivery. Body weight (BW) was recorded before sampling at each stage of the experiment. Body growth was maximal between W4 and W8 for both SO (+97%) and CX (+84%). However SO were heavier than CX at W8 and W12. In SO, a surge of plasma IGF-I levels was observed between W4 and W8, concomitantly to the increase of androgen levels (IGF-I: +86%, P less than 0.01; T: +190%, P less than 0.001; DHT: +18%; P less than 0.01). Significant correlations between IGF-I, T, DHT and BW were found only from W4 to W8 but not from W8 to W12. In CX, IGF-I levels were higher than in SO at W4 (+72%, P less than 0.01) and at W12 (+39%, P less than 0.01). A surge of IGF-I levels (+47%, P less than 0.01) was also observed but was delayed compared to SO (between W8 and W12 vs W4 and W8). BW and IGF-I levels were significantly correlated during this period. Because the surge of IGF-I levels may occur even in absence of gonads, these results give evidence that the increases in IGF-I and androgens at puberty were independent in guinea-pigs during this period.(ABSTRACT TRUNCATED AT 250 WORDS)     

REVIEWS

Book reviewed in this article:
Atlas of the British Flora . Edited by F. H. P erring and S. M. W althrs .
Handbuch der Pflanzenphysiologie: Encyclopedia of Plant Physiology . Vol. XIV: Growth and Growth Substances. Edited by W. R uhland .
Drawings of British Plants . Part XVII: Compositae (3). By S tella R oss -C raig .
Apical Meristems . By F. A. L. C lowes . Botanical Monographs, vol. 2. Edited by W. O. J ames .
Cellular Regulatory Mechanisms . Cold Spring Harbor Symposia on Quantitative Biology
Proceedings of the Summer School of Botany held June 2–15, 1960, at Darjeeling . Edited by P. M aheshwari , B. M. J ohri and I. K. V asil .
Exotic Forest Trees in the British Commonwealth . By R. J. S treets . Edited by Sir H arry C hampion .
A Flora of the Alaskan Arctic Slope . By I. L. W iggins and J. H. T homas
Grundzüge der Pflanzenanatomie . By B. H uber .
Taschenbuch der Botanik . By H. M iehe . Revised by W. M evius .
A Conspectus of Aphids as Vectors of Plant Viruses . By J. S. K ennedy , M. F. D ay and V. F. E astop .
Crop Adaptation and Distribution . By C arroll P. W ilsie .
Flora of Cultivated Plants of the U.S.S.R. Vol. XIII: Perennial Leguminous Plants: Medicago, Melilotus and Trigonella. Edited by E. N. S inskaya . Translated by N. L andau .
Der Federsee . Edited by W. Z immermann .
Carbohydrate Resources within the Perennial Plant . By C. A. P riestley .
Flora of the British Isles . By A. R. C lapham , T. G. T utin and E. F. W arburg .
Mineral Salts Absorption in Plants . By J. F. S utcliffe .
The Development of British Heathlands and their Soils . By G. W. D imbleby .
Annual Review of Plant Physiology , vol. 13. Edited by L. M achlis and W. R. B riggs .