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1.
This book, aimed at undergraduates, deals mostly with the informationthat can be gleaned about plant evolution from the fossil record.In some sense, its broad title is slightly misleading becauseother topics central to plant evolution such as genetic changein populations and mechanisms of speciation are hardly covered.After a brief introduction to the geological timescale, typesof fossil and how they are dated, the central six chapters formingthe bulk of the book follow a chronological journey. This takesthe reader from the appearance of the first photosynthesizers,to the colonization of the land, through to the evolution anddominance of  相似文献   

2.
LAWLOR  D. W. 《Annals of botany》2004,93(4):479-480
That this text book is now in its fifth edition clearly showsthe strength of its content and presentation, and its relevanceto the scientific community, which should include all thoseinterested in plants and their growth. There are 20 chapters.The first is an overview of definitions and processes whichare considered in much greater depth later. Then follow substantialchapters on ‘The Soil as a Plant Nutrient Medium’,  相似文献   

3.
A new autosomal recessive mutation in the mouse, little (lit), has been shown to be located on Chromosome 6. The mutation in the homozygous state causes ateliotic dwarfism that is first detected at 15 days of age by decreased body weight. Long bone lengths are significantly reduced. Skull width, however, is not affected. Female little mice are fully fertile; they may lose their first litters. Although most of the little males sire one or two litters, they rarely sire a third litter. Analysis of pituitary extracts electrophoresed on acrylamide gels reveal a significant reduction of the two anterior pituitary hormones, GH and PRL, in both male and female little mice. Because the little mouse shares a number of similarities with the human ateliotic dwarfism, isolated growth hormones deficiency type I, it may be a useful animal model for this inherited human growth disorder.  相似文献   

4.
Chromosome number determinations from 118 populations of eight species of the aster genus Virgulus are reported for the first time. Based on these counts and literature reports the geographic distributions of diploids and tetraploids in V. concolor, V. novae-angliae, V. oblongifolius, and V. patens have been determined. In the first three species, diploids were widely distributed, while tetraploids were more restricted. In V. patens, diploids were restricted to the southwestern portion of the species’ range, while tetraploids were found throughout the range. Both V. adnatus and V. walteri were found only at the tetraploid level throughout their ranges. Two other species with restricted distributions were consistently found to be high level polyploids: V. georgianus with 2n = 50, V. grandiflorus with 2n = 60. The following new combinations are listed: Virgulus georgianus (Alexander ex Small) Semple; Virgulus subsect. Brachyphylli (Torr. & Gray) Semple; and Virgulus sect. Polyliguli (Semple & Brouillet) Semple.  相似文献   

5.
GASSON  PETER 《Annals of botany》2003,92(3):472-473
IAWA (International Asso ciation of Wood Anato mists) publishesa high quality journal in four parts, comprising about 500 pagesa year. Every so often they publish supplements that are muchlonger and more comprehensive than traditional scientific papers.The first two were Bibliography of systematic wood anatomy ofdicotyledons (265 pages) by Mary Gregory (1994) and Wood anatomyof Sapindaceae (214 pages) by René Klaasen (1999). Thisthird supplement is on a fossil flora which has many well-preservedwoods that have now been studied in detail. The only minor criticismI have is that the title of  相似文献   

6.
Joseph A. Grasso 《Cell》1980,20(3):885-887
We have utilized a cracking procedure followed by a rotary shadow technique to examine the ultrastructure of cultured ovarian granulosa cells. We have demonstrated that the structures observed are not artifacts of fixation or cracking by generating equivalent images following freezing and deep etching as well as by fixation prior to cracking. The cytoplasm of granulosa cells exhibits a complex cytoskeletal lattice composed of many 40–55 nm filaments. This filamentous network is continuous with the plasma membrane and appears to incorporate all formed elements within the cytoplasm. Filaments are organized in three ways: first, in large bundles, second, in individual filaments that are in direct association with organelles, and third, in a complex branching and anastomosing configuration. S-1 decoration revealed that the predominant filament species is actin.  相似文献   

7.
In the originally published version of this article the first and surnames of the authorship were transposed. This notice is being published to amend the error and corrected online files of the original article are now available. J. Cell. Biochem. 108: 536, 2009. © 2009 Wiley‐Liss, Inc.  相似文献   

8.
The immature fruits of domesticated Luffa acutangula (L.) Roxb. are a common vegetable in Asia and India. To learn more about traditional cultivars, accessions were collected from southern Yunnan Province of China, northern Laos, and southeastern Nepal, and assessed for various parameters of genetic diversity. The size and shape of the fruits and seeds varied considerably. A form that we found cultivated only in Nepal bore clusters of small fruits that are produced by hermaphrodite flowers. Plants produced male flowers first, and the first node to bear flowers varied from the second to the twenty-seventh. Twenty-nine allozyme loci were assayed. Within L. acutangula one allozyme locus was polymorphic. Luffa acutangula andL. aegyptiaca are fixed for different alleles at nine loci, indicating that they are completely reproductively isolated from each other.  相似文献   

9.
Antimicrobial peptides and proteins (AMPs) are among the most important components of the immune system of multicellular organisms. The role of AMPs is of particular importance for invertebrates which constitute the vast majority of species diversity of the living world, because these animals lack acquired immunity. The AMPs of animal origin are ribosomally-synthesized molecules that have, as a rule, a positive net charge and amphiphilic properties. They can act against bacteria, yeast and filamentous fungi, protozoa, and enveloped viruses. AMPs can also play a role of mediators of the immune system. Search and investigation for protective factors of the invertebrate host defense provide a better understanding of mechanisms of the innate immunity of humans and other mammals and give a key to a development of new medicines. The first part of this review focuses on special features of a structure, biosynthesis, regulation of gene expression, and molecular evolution of AMPs of invertebrates.  相似文献   

10.
The montane and subalpine forests of a mountain range in northwestern Montana were investigated using phytosociological and numerical methods. Twelve associations and two subassociations were identified, of which eight are described here for the first time. The forest vegetation of valleys and lower slopes is strongly affected by repeated fire and is placed in the new orderCalamagrostio-Pseudotsugetalia glaucae, which includes temperate, low elevation forests in inland regions of northwestern North America. These forests bear only weak resemblance to forests traditionally assigned to the classVaccinio-Piceetea, and occupy the habitats filled by broad-leaved forests elsewhere at temperate latitudes. Montane and subalpine forest vegetation is moister and has longer snow duration and a shorter growing season. Upper montane vegetation more closely resembles that of other temperate montane forests of the classVaccinio-Piceetea.  相似文献   

11.
Developmental milestones, problems with bladder and bowel control, sleep disturbances, allergies, and handedness were compared in 247 consecutive Tourette syndrome (TS) patients, 17 patients with attention-deficit disorder (ADD), 15 patients with ADD secondary to TS (ADD 2(0) TS), and 47 random controls. There were no significant differences in age of first talking or walking. By contrast, there were significant differences in problems with bladder and bowel control between TS patients and controls, as measured by age of first toilet training, age of last bed-wetting, frequency of enuresis, and age that bowel control was achieved. Sleep problems were pervasive in TS patients, with a significantly increased frequency of sleepwalking, night terrors, trouble getting to sleep, early awakening, and inability to take afternoon naps as a young child. In all diagnostic categories, including mild (grade 1) TS patients, a total sleep-problem score was significantly greater than that in controls. The sleep disorders and other TS symptoms are consistent with TS as a disorder of disinhibition of the limbic system. Allergies and left-handedness have been evoked as contributing to or being associated with ADD and learning disorders. There were no significant differences in the frequency of allergies or left-handedness in TS patients compared with that in controls. We conclude that when there is a clearly defined genetic cause of ADD and learning disorders, it is not associated with an increased frequency of allergies or left-handedness.  相似文献   

12.
The partial nucleotide sequence of a Lactococcus lactis subsp. lactis ADRIA 85LO30 bacteriocin-producing operon was determined. The first two open reading frames of the operon are necessary to get bacteriocin expression in L. lactis IL1403R.  相似文献   

13.
Three species of marine algae are reported from the Bermuda islands for the first time, Avrainvillea sylvearleae D. S. Littler et Littler, Discosporangium mesarthrocarpum (Menegh.) Hauck, and Peyssonnelia valentinii Yonesh. et Boudour. The presence of Avrainvillea sylvearleae in Bermuda prompted a taxonomic reinvestigation of North Carolina specimens attributed recently to that taxon, and we find them better placed in A. longicaulis f. laxa D. S. Littler et Littler. The report of the eastern Atlantic/Mediterranean Discosporangium mesarthrocarpum is the first from the western Atlantic Ocean and joins only 12 other amphi-Atlantic species with strictly warm-temperate zone distributions. Peyssonnelia valentinii is discovered for the first time outside of Brazil.  相似文献   

14.
The rate and extent of electron transfer from ferrous ion to ferricytochrome c are enhanced by the presence of inorganic orthophosphate at concentrations comparable to those of reductant and oxidant. Evidence, obtained by the method of continuous variations, shows that the electron transfer occurs within a stoichiometric complex composed of cytochrome c, ferrous ion, and phosphate in molar proportions of about 1:1:1. The incorporation of the anion into this complex appears to result in a modulation of the extent and rate of cytochrome c reduction. The rate of electron transfer obeys a first order rate law, characterized by an apparent first order rate constant of 1.4 min-1. The complex has kinetic significance only; equilibrium dialysis, gel filtration, and sedimentation velocity experiments yielded no evidence for stable binding of phosphate and iron, or of aggregation, on a significant scale. The extent of reduction is limited (for reasons not yet known) to about one-half of the available cytochrome molecules. Reduction in excess of 50% can be achieved only when both, ferrous ion and phosphate, are present in excess of the cytochrome concentration. Kinetic data indicate that reduction to extents over and below 50% occurs by different mechanisms.  相似文献   

15.
16.
A comparison of the physical-chemical properties of human, bovine, and horse antithrombin III has been made. These three plasma proteins are strong inhibitors of bovine factor Xa and form a 1:1 molar complex with this coagulation enzyme. Human, bovine, and horse antithrombin III are glycoproteins containing hexose, hexosamine, and neuraminic acid. The total carbohydrate was 9, 12, and 16% for human, bovine, and horse antithrombin III, respectively. These proteins have a similar amino acid composition, although some monor variations were noted. Each antithrombin III is composed of a single polypeptide chain with an amino-terminal histidine residue. Of the first 17 amino-terminal residues, only three differences were noted between the three proteins. These occur in position 2 which is occupied by Gly, Arg, and Trp in human, bovine, and horse, respectively; position 6 which has a deletion in human antithrombin III; and position 8 where Ile in human and horse antithrombin III has been replaced by Val in the bovine preparation. The remainder of the first 17 residues is the same in all three proteins. The molecular weights for the bovine and horse preparation were 56 600 and 52 500, respectively, as determined by sedimentation equilibrium in the presence of guanidine hydrochloride. Some immunological cross-reactivity was also observed between the three different proteins.  相似文献   

17.
The antihypertensive properties of the new diuretic tienilic acid were investigated. Thirteen previously untreated hypertensive patients took part in a double-blind crossover study in which 30 days'' treatment with tienilic acid 250 mg, bendrofluazide 5 mg, and spironolactone 100 mg were compared. Bendrofluazide caused the greatest natriuresis on the first treatment day and the most rapid fall in blood pressure. The ultimate antihypertensive effect of all three drugs was similar. Tienilic acid caused a noticeable reduction in serum urate concentrations and a rise in urate clearance, in contrast to the other two agents, which caused slight urate retention. Tienilic acid and bendrofluazide caused falls and spironolactone a rise in plasma potassium concentrations. No untoward effects were seen from any of the drugs. It is concluded that tienilic acid is a moderately potent diuretic that lowers plasma urate concentrations. It may be the drug of first choice for hypertensive patients who already have gout or are likely to develop it when taking thiazide diuretics.  相似文献   

18.
Heterophyes heterophyes is reported for the first time from the snail host Pirenella conica in Greece. H. aequalis and H. dispar are reported for the first time from Greece and from Europe. The results presented, together with the available data on necropsies of dogs and cats, human infections and the biotope preference of the snail, suggest that Greece is an important focus of infection in Europe.  相似文献   

19.
The occupancy principle and the mean-transit-time theorem are derived for the passage of a tracer through a system that can be described by a general pool model. It is proved, using matrix theory, that if (and only if) tracer entering the system labels equally all tracee fluxes into the system, then the integral of the tracer concentration is the same in all the pools. It is also proved that if, in addition, all flow out of the system is through the observation point, the first moment of the tracer concentration at the observation point can be used to calculate the total amount of trace in the system. The necessity of this condition is analyzed. Examples are given of models in which the occupancy principle and the mean-transit-time theorem hold or do not hold.  相似文献   

20.
Initial velocity and ATP-ADP isotope exchange kinetic data on yeast nicotinate phosphoribosyltransferase indicate a sequential steady-state mechanism m which ATP adds first, followed by a random order of addition of the substrates PP-ribose-P and nicotinic acid. Reaction flux through the alternative ping-pong pathway, evidenced first by ATP-ADP isotope exchange in the absence of nicotinic acid and PP-ribose-P substrates, is reduced by low concentrations of either, or both, of these substrates. Both Mg2+-complexed and -free PP-ribose-P are enzymatically active. Phosphorylated enzyme, prepared with [γ-32P]ATP and separated by gel chromatography, retains 32Pi until incubated with both substrates, PP-ribose-P and nicotinic acid, which completely discharge the 32Pi.  相似文献   

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