bluuebunny/crossref_metadata_2025 huggingface dataset:
RNA Structure and Packaging Signals in the 5′ Leader Region of the Human Immunodeficiency Virus Type 1 Genome
Authors: Clever Jared L. , Miranda, Daniel , Parslow Tristram G.
Published: November 2002

The leader region of the human immunodeficiency virus type 1 (HIV-1) genome has a highly folded structure, comprising at least two RNA stem-loops [the transactivation response (TAR) and poly(A) hairpins] near its 5′ end and four others (SL1 to SL4) downstream. Each of these stem-loops contributes to the function of the HIV-1 packaging signal, which efficiently targets genomic RNA into nascent virions. The central 140-base region of the leader, which includes the U5 and primer binding site (PBS) sequences, is also believed to adopt a complex structure, but the nature of this structure and its possible role in RNA packaging have not been extensively explored. Here we report a mutational analysis identifying at least three separate loci within the U5-PBS region which, when mutated, impair both HIV-1 packaging specificity and infectivity in a single-round proviral assay. In common with those of all previously described packaging signals in the leader, the function of one of these loci appeared to depend on secondary structure rather than on sequence alone. By contrast, the activity of the other two loci did not correlate with any predicted conformations. Moreover, unlike SL1 to SL4, the TAR, poly(A), and U5-PBS hairpins were not bound with high affinity by the nucleocapsid portion of the HIV-1 Gag protein in vitro, implying that they contribute to packaging through a mechanism distinct from that of SL1 to SL4. Our findings confirm the existence and importance of secondary structure around the PBS and demonstrate that functional packaging signals are distributed across the entire HIV-1 leader.
Compromised Influenza Virus-Specific CD8+-T-Cell Memory in CD4+-T-Cell-Deficient Mice
Authors: Belz Gabrielle T. , Wodarz Dominik , Diaz Gabriela , Nowak Martin A. , Doherty Peter C.
Published: November 2002

The primary influenza A virus-specific CD8+-T-cell responses measured by tetramer staining of spleen, lymph node, and bronchoalveolar lavage (BAL) lymphocyte populations were similar in magnitude for conventionalI-Ab+/+and CD4+-T-cell-deficientI-Ab−/−mice. Comparable levels of virus-specific cytotoxic-T-lymphocyte activity were detected in the inflammatory exudate recovered by BAL following challenge. However, both the size of the memory T-cell pool and the magnitude of the recall response in the lymphoid tissues (but not the BAL specimens) were significantly diminished in mice lacking the CD4+subset. Also, the rate of virus elimination from the infected respiratory tract slowed at low virus loads following challenge of naïve and previously immunizedI-Ab−/−mice. Thus, though the capacity to mediate the CD8+-T-cell effector function is broadly preserved in the absence of concurrent CD4+-T-cell help, both the maintenance and recall of memory are compromised and the clearance of residual virus is delayed. These findings are consistent with mathematical models that predict virus-host dynamics in this, and other, models of infection.
Involvement of Apolipoprotein E in the Hematogenous Route of Herpes Simplex Virus Type 1 to the Central Nervous System
Authors: Burgos Javier S. , Ramirez Carlos , Sastre Isabel , Bullido María J. , Valdivieso Fernando
Published: November 2002

Apolipoprotein E (ApoE), a constituent of the lipoproteins, may be relevant in herpes simplex virus type 1 (HSV-1) infection of the central nervous system (CNS), since HSV-1 binds to human serum ApoE lipoproteins. This study demonstrates the involvement of ApoE in the hematogenous route of HSV-1 to the CNS.
Inhibition of Hepatitis Delta Virus RNA Editing by Short Inhibitory RNA-Mediated Knockdown of ADAR1 but Not ADAR2 Expression
Authors: Jayan Geetha C. , Casey John L.
Published: November 2002

Hepatitis delta virus (HDV) requires host RNA editing at the viral RNA amber/W site. Of the two host genes responsible for RNA editing via deamination of adenosines in double-stranded RNAs, short inhibitory RNA-mediated knockdown of host ADAR1 expression but not that of ADAR2 led to decreased HDV amber/W editing and virus production. Despite substantial sequence and structural variation among the amber/W sites of the three HDV genotypes, ADAR1a was primarily responsible for editing all three. We conclude that ADAR1 is primarily responsible for editing HDV RNA at the amber/W site during HDV infection.
Diagnosis and treatment of viral encephalitis
Authors: Chaudhuri A , Kennedy P G E
Published: November 2002

Acute encephalitis constitutes a medical emergency. In most cases, the presence of focal neurological signs and focal seizures will distinguish encephalitis from encephalopathy. Acute disseminated encephalomyelitis is a non-infective inflammatory encephalitis that may require to be treated with steroids. Acute infective encephalitis is usually viral. Herpes simplex encephalitis (HSE) is the commonest sporadic acute viral encephalitis in the Western world. Magnetic resonance imaging of brain is the investigation of choice in HSE and the diagnosis may be confirmed by the polymerase chain reaction test for the virus in the cerebrospinal fluid. In this article, we review the diagnosis, investigations, and management of acute encephalitis. With few exceptions (for example, aciclovir for HSE), no specific therapy is available for most forms of viral encephalitis. Mortality and morbidity may be high and long term sequelae are known among survivors. The emergence of unusual forms of zoonotic encephalitis has posed an important public health problem. Vaccination and vector control measures are useful preventive strategies in certain arboviral and zoonotic encephalitis. However, we need better antiviral therapy to meet the challenge of acute viral encephalitis more effectively.
Prostate cancer
Authors: Mazhar D , Waxman J
Published: November 2002

It is a paradigm in cancer treatment that early detection and treatment improves survival. However, although screening measures lead to a higher rate of detection, for small bulk localised prostate cancer it remains unclear whether early detection and early treatment will lead to an overall decrease in mortality. The management options include surveillance, radiotherapy, and radical prostatectomy but there is no evidence base to evaluate the benefits of each approach. Advanced prostate cancer is managed by hormonal therapy. There have been major changes in treatment over the last two decades with the use of more humane treatment and developments in both chemotherapy and radiation. In this article we review the natural history and management of prostate cancer.
Nocturnal leg cramps in older people
Authors: Butler J V , Mulkerrin E C , O’Keeffe S T
Published: November 2002

Nocturnal leg cramps are common in older people. Such cramps are associated with many common diseases and medications. Physiological methods may be useful for preventing cramps in some people, but there have been no controlled trials of these approaches. Quinine is moderately effective in preventing nocturnal leg cramps. However, there are concerns about the risk/benefit ratio with this drug. In patients with severe symptoms, a trial of 4–6 weeks’ treatment with quinine is probably still justified, but the efficacy of treatment should be monitored, for example using a sleep and cramp diary.
Current concepts for the management of systemic lupus erythematosus in adults: a therapeutic challenge
Authors: Ioannou Y , Isenberg D A
Published: November 2002

Systemic lupus erythematosus (SLE) is a chronic, autoimmune rheumatic disease with many clinical presentations typically affecting women of childbearing age. The successful therapy of SLE depends upon treating both symptoms and the underlying inflammation. Both non-pharmacological as well as pharmacological therapies are invariably required. Non-pharmacological therapy includes avoiding over-exposure to sunlight with the use of adequate sunscreen protection, avoiding “live” vaccination if on immunosuppressive agents, adherence to a diet low in saturated fat and high in fish oil, stress avoidance, and smoking cessation. Pharmacological measures revolve around four main classes of drugs: non-steroidal anti-inflammatory drugs, antimalarials, corticosteroids, and cytotoxic agents. Cyclophosphamide and azathioprine are the two most commonly used cytotoxic agents and these in combination with corticosteroids need to be employed early if there is major organ involvement to prevent or minimise irreversible damage. The potential side effects of corticosteroids and cytotoxic agents need constant consideration. The rapid developments in biotechnology of recent years may soon lead to new and more specific therapies for patients with SLE.
Surveillance of surgical training by detailed electronic registration of logical components
Authors: Tøttrup A
Published: November 2002

Objective

To obtain detailed information about the degree of surgical trainee supervision and delegation of procedures in a subspecialised department.

Design

Operative procedures and their logical components were recorded in a database constructed in Microsoft Access. Information about operating surgeon and assistants and their grade was registered prospectively over 12 months.

Subjects and methods

A total of 1250 intermediate or major procedures were performed by eight consultants, one staff specialist, four senior registrars, three specialist registrars, and five registrars.

Main measure

Number of components performed by surgeons in each grade and the degree of supervision and delegation.

Results

Eight hundred and eighty five of the operations were elective, while 365 were done as emergency procedures. Emergency procedures were far more often done by surgeons in training than by a staff surgeon, while the opposite was true for elective operations. Out of 323 elective operations done by surgeons in training, 189 were done under supervision (58.5%), while 119 out of 276 emergency operations done by surgeons in training were supervised (43.1%; p=0.0002). One hundred and twenty eight of 638 (20%) open abdominal operations were done by the most junior surgeons, and yet they closed 36% of all abdominal wounds. Although the most junior surgeons only served as operating surgeons in 39 of 334 bowel operations (12%), they constructed 24% of all stomas, and 20% of all anastomoses. Registrars and specialist registrars never constructed stomas or anastomoses without supervision.

Conclusion

Detailed information about individual and general training and supervision was achieved by a simple registration. Significant additional information was obtained about the extent of delegation of components compared with standard registration of operative procedures.
Does patient knowledge affect the colorectal cancer risk in ulcerative colitis?
Authors: Eaden J A , Abrams K , Mayberry J F
Published: November 2002

Objectives

Formal efforts to improve patient education are associated with fewer disease complications in a number of conditions. The possible relationship between knowledge about ulcerative colitis and its cancer risk, and the development of colorectal cancer using a previously developed and validated instrument—the Crohn’s and colitis knowledge (CCKNOW) score—were investigated.

Methods

The 24 item CCKNOW questionnaire was mailed to patients known to have developed colorectal cancer as a complication of ulcerative colitis (cases) and to colitics from the Leicestershire inflammatory bowel disease patient database who had not developed cancer (controls).

Results

The mean (SD) CCKNOW scores for cases was 8.21 (3.02) and for controls was 8.27 (4.3). These scores did not differ significantly between cases and controls (difference 0.06, 95% confidence interval (CI) −1.7 to 1.5, p=0.9). There were four times as many members of the National Association of Crohn’s and Colitis (NACC) in the control group compared with the cancer group and patients who are members of NACC achieve statistically significantly higher scores than non-members (11.6 v 7.8, p=0.05, 95% CI −0.1 to 7.6). However, after adjusting for NACC membership, the CCKNOW score did not appear to be associated with having developed cancer (odds ratio 1.04, 95% CI 0.92 to 1.18, p=0.5).

Conclusions

The CCKNOW scores were comparable in cases and controls. Thus, in a retrospective study, no evidence has been demonstrated of an association between patient knowledge and the risk of developing colorectal cancer in patients with ulcerative colitis. However, knowledge may have been increased in cases as a direct result of having had colorectal cancer as a complication of ulcerative colitis.
An unusual epistaxis
Authors: Saunders S , Young C
Published: November 2002

The case of a man who presented complaining of epistaxis is reported. He had coarctation repair 18 years previously. Subsequent investigation revealed an aortobronchial fistula resulting from false aneurysm formation distal to the original vessel anastamosis. This was repaired at surgery, the patient suffering a minor stroke, before rehabilitation and good recovery.
Bronchiolitis obliterans and organising pneumonia caused by carbamazepine and mimicking community acquired pneumonia
Authors: Banka R , Ward M J
Published: November 2002

Bronchiolitis obliterans and organising pneumonia (BOOP) presents with fever, dyspnoea, and other features that may be mistaken for pneumonia. Treatment is, however, very different, requiring corticosteroids.

A man was admitted as an emergency with fever, dyspnoea, and non-productive cough. The chest radiograph showed consolidation which, despite antibiotics, progressed to become bilateral. BOOP was considered, and confirmed by transbronchial biopsy. The response to oral prednisolone was rapid with complete resolution of symptoms and radiographic consolidation within three weeks. The cause of BOOP is often never found; it is believed, however, that in this instance it occurred as a result of carbamazepine therapy started seven weeks earlier.
Possible functional regression of insulinoma with prolonged octreotide
Authors: Craig C E H , Gallen I W
Published: November 2002

A 75 year old woman was treated for over three years with the somatostatin analogue, octreotide for an insulinoma. She had presented in a hypoglycaemic coma. C-peptide and insulin concentrations were both raised and an area of increased vascularity within the pancreas was shown by angiography. No lesion was found at laparotomy and no resection was performed. After over three years of octreotide treatment it was withdrawn for a week. Her insulin and C-peptide concentrations were greatly reduced at this time and remained so.
How safe is blood sampling? Anterior interosseus nerve injury by venepuncture
Authors: Zubairy A I
Published: November 2002

All invasive procedures carry some degree of risk of damage to the normal structures in the proximity of the region where the procedure is performed. The risk is, however, minimal for venous cannulation. A case is reported of an injury to the anterior interosseus nerve sustained during venepunture for routine blood sampling at the cubital fossa.
Comparing methods of preservation for cultures of entomopathogenic fungi
Authors: López Lastra Claudia C , Hajek Ann E , Humber Richard A
Published: November 2002

Nine species of entomopathogenic fungi were tested for viability after they had been stored with deionized water, mineral oil, or silica gel or frozen at 20 or 80°C. Species tested included members of the Hyphomycetes, Entomophthorales, Trichomycetes, and Oomycetes. The fungal cultures were maintained up to 1.5 years and were checked at 3, 6, 12, and 18 months. For all species evaluated, Paecilomyces fumosoroseus demonstrated the best results, surviving through 18 months when stored with water or mineral oil and when frozen at 80°C. For the majority of other fungal species tested, except the trichomycete Smittium culisetae and oomycete Leptolegnia chapmanii, freezing at 80°C was the best storage method and storage with silica gel was the worst. In addition to culture viability, infectivity against Aedes aegypti larvae was evaluated after 18 months of storage for L. chapmanii and S. culisetae. The simplest and least expensive methods, using water or mineral oil, were the only successful methods for maintaining viability and infectivity of L. chapmanii and S. culisetae.Key words: entomopathogenic fungi, preservation, storage, viability.
Lignification of spruce tracheid secondary cell walls related to longitudinal hardness and modulus of elasticity using nano-indentation
Authors: Gindl W , Gupta H S , Grünwald C
Published: November 2002

The lignin content and the mechanical properties of lignifying and fully lignified spruce tracheid secondary cell walls were determined using UV microscopy and nano-indentation, respectively. The average lignin content of developing tracheids was 0.10 g·g1, as compared with 0.21 g·g1 in mature tracheids. The modulus of elasticity of developing cells was on average 22% lower than the one measured in mature, fully lignified cells. For the longitudinal hardness, a larger difference of 26% was observed. As lignifying cells in the cambial zone are undergoing cell wall development, spaces in the cellulosehemicellulose structure are filled with lignin and the density of the cell wall is believed to increase. It is therefore suggested that the observed difference in modulus of elasticity between developing and fully lignified cell walls is due to the filling of spaces with lignin and an increase of the packing density of the cell wall during lignification. Although remarkably less stiff than the composite polysaccharide structure in the secondary cell wall, lignin may be considered equally hard. Therefore, the observed increase in lignin content may contribute directly to the measured increase of hardness.Key words: secondary cell wall, hardness, lignin, modulus of elasticity, wood formation.
Development of primary germ tubes by conidia of Blumeria graminis f.sp. hordei on leaf epidermal cells of Hordeum vulgare
Authors: Edwards H H
Published: November 2002

Development of primary germ tubes from conidia of Blumeria graminis f.sp. hordei on primary leaf segments of Hordeum vulgare was investigated from 3 to 13 h postinoculation (hpi) using transmission electron microscopy. By 3 hpi, the primary germ tube wall that makes contact with the host cuticle develops a small protrusion that breaches the host cuticle and touches the host cell wall but does not penetrate any further. This protrusion is the cuticular peg. From 3 to 13 hpi, the cuticular peg swells, becomes quite electron dense, and finally develops a loose fibrillar texture. The structure of the primary germ tube with the terminal cuticular peg is consistent with the hypothesis that it allows the conidium to absorb water and solutes present in the host cell wall.Key words: powdery mildew, barley, ultrastructure.
Low growth temperature inhibition of photosynthesis in cotyledons of jack pine seedlings (Pinus banksiana) is due to impaired chloroplast development
Authors: Krol Marianna , Hurry Vaughan M , Maxwell Denis P , Malek Lada , Ivanov Alexander G , Huner Norman PA
Published: November 2002

Cotyledons of jack pine seedlings (Pinus banksiana Lamb.) grown from seeds were expanded at low temperature (5°C), and total Chl content per unit area of cotyledons in these seedlings was only 57% of that observed for cotyledons on 20°C-grown controls. Chl a/b ratio of 5°C-grown jack pine was about 20% lower (2.3 ± 0.1) than 20°C controls (2.8 ± 0.3). Separation of Chl-protein complexes and SDS-PAGE indicated a significant reduction in the major Chl a containing complex of PSI (CP1) and PSII (CPa) relative to LHCII1in 5°C compared to 20°C-grown seedlings. In addition, LHCII1/LHCII3ratio increased from 3.8 in control (20°C) to 5.5 in 5°C-grown cotyledons. Ultrastructurally, 5°C-grown cotyledons had chloroplasts with swollen thylakoids as well as etiochloroplasts with distinct prolamellar bodies. Based on CO2-saturated O2evolution and in vivo Chl a fluorescence, cotyledons of 5°C jack pine exhibited an apparent photosynthetic efficiency that was 40% lower than 20°C controls. Seedlings grown at 5°C were photoinhibited more rapidly at 5°C and 1200 µmol·m2·s1than controls grown at 20°C, although the final extent of photoinhibition was similar. Exposure to high light at 5°C stimulated the xanthophyll cycle in cotyledons of both controls and 5°C-grown seedlings. In contrast to winter cereals, we conclude that growth of jack pine at 5°C impairs normal chloroplast biogenesis, which leads to an inhibition of photosynthetic efficiency.Key words: chloroplast, growth, temperature, photosynthesis, photoinhibition, Pinus banksiana Lamb., ultrastructure.
Fine-scale genetic structure in populations ofQuercus variabilis(Fagaceae) from southern Korea
Authors: Chung Mi Yoon , Chung Myong Gi
Published: November 2002

Quercus variabilis Blume (Fagaceae) is a deciduous broad-leaved tree, and an important forest element among the hillsides of southern Korea. To date, there are contrasting results with respect to fine-scale spatial genetic structure among adults in populations of several oak species; some studies have shown evidence of significant within-population spatial genetic structure, while others found weak or little evidence of fine-scale genetic structuring within populations. We used allozyme loci, Wright's F statistics, and multilocus spatial autocorrelation statistics to examine the distribution of genetic diversity and the spatial genetic structure within three undisturbed populations at a landscape level (72.5 ha, 500 × 1450 m) on Dolsan Island, South Korea. The spatial autocorrelation analyses of adults showed little evidence of fine-scale genetic structuring within populations, which could be due to random mortality among related seedlings, resulting in extensive thinning within maternal half-sib groups. Alternatively, low genetic differentiation between adjacent populations (mean FST= 0.023) and little within-population spatial genetic structure suggest probable secondary acorn movement by animals. Our results are very similar to those observed in three populations of Quercus acutissima at a landscape level (15 ha, 250 × 600 m) on Oenaro Island, South Korea. Together, these studies describe relatively subtle differences in genetic structure among adjacent populations of oaks on southern islands in Korea.Key words: allozymes, Quercus variabilis, Fagaceae, landscape level, multiple populations, spatial genetic structure.
Clonal expansion in the deciduous understory shrub, devil's club (Oplopanax horridus; Araliaceae)
Authors: Lantz Trevor C , Antos Joseph A
Published: November 2002

To examine clonal growth and the ability of devil's club (Oplopanax horridus (Sm.) Torr. & A. Gray ex Miq.) to persist throughout stages of forest succession, we sampled populations in three classes of stand development: clearcuts (110 years old), young stands (1150 years old), and maturing stands (51200+ years old). We completely excavated and mapped all clonal fragments (systems of ramets connected by decumbent stems) in a plot at each site and determined ramet and clonal fragment age using annual growth rings on stem cross sections. Clonal fragment density and size, ramet density and age, decumbent stem length, annual stem elongation, annual ramet recruitment, lateral meristem formation, and the number of persistent dead ramets were significantly (P < 0.05) related to stand development class. Clonal fragments in clearcut stands were large, predating the year of stand establishment, with many dead, old ramets, but many young stems. Ramet recruitment and lateral meristem formation were highest in clearcut stands, which contributed to replacement of older ramets lost to the disturbance. Clonal fragments in young stands were few and small, consisting of a few ramets and short decumbent stems. In maturing stands, clonal fragments were numerous but consisted of few ramets with extensive decumbent stem connections. No devil's club seedlings were observed in any of the stands sampled. Devil's club populations are maintained by prolific basal stem sprouting following disturbance and continual layering and clonal fragmentation throughout stand development.Key words: age structure, clonal architecture, clonal shrubs, demography, layering, population dynamics.
Light environment and crown architecture of two temperate Vaccinium species: inherent growth rules versus degree of plasticity in light response
Authors: Kawamura Koji , Takeda Hiroshi
Published: November 2002

Light environment and crown architecture were investigated in two closely related species (deciduous Vaccinium hirtum and evergreen Vaccinium bracteatum) in a young and an old secondary forest. Light environment was determined by photographic estimation of light above ramets (30500 cm tall). Crown architecture was examined to determine the effects of ramet age and light level on several architectural traits. In the young secondary forest, both species were mainly found in large gaps. In the old secondary forest, V. bracteatum persisted in deep shade, whereas V. hirtum was concentrated in small gaps. Vaccinium hirtum had narrower crowns and thinner stems than V. bracteatum, indicating lower structural costs in V. hirtum. Older ramets had greater total shoot extension (only V. bracteatum) and shorter length of the current-year shoots (markedly so in V. hirtum) than younger ramets. In higher light levels, V. bracteatum had greater aboveground growth and higher leaf area indices, whereas V. hirtum had only greater flowering intensity. Architectural traits were highly correlated with ramet age in V. hirtum, whereas these were mainly affected by light in V. bracteatum, indicating higher architectural plasticity in the latter species. The differences in architecture and its plasticity can be relevant for the segregation of light habitats between the species.Key words: light environment, crown architecture, leaf display, morphological plasticity, current-year shoot.
Eocene Ginkgo leaf fossils from the Pacific Northwest
Authors: Mustoe George E
Published: November 2002

Middle Eocene lacustrine deposits in south-central British Columbia and north-central Washington state preserve two types of Ginkgo leaves. A morphotype characterized by deeply divided multiple lobes is herein described as Ginkgo dissecta sp.nov. Leaves that are either undivided or shallowly divided into bilobate symmetry are indistinguishable from foliage of extant Ginkgo biloba Linnaeus. These fossils contradict the widely held belief that only a single Ginkgo species, Ginkgo adiantoides (Unger) Heer, inhabited Cenozoic forests.Key words: British Columbia, Eocene, fossil, Ginkgo adiantoides, Ginkgo biloba, Ginkgo dissecta, McAbee, Republic, Tertiary, Washington.
Sporidial mating and infection process of the smut fungus,Ustilago hordei, in susceptible barley
Authors: Hu G G , Linning R , Bakkeren G
Published: November 2002

Ustilago hordei (Pers.) Lagerh. causes covered smut of barley and oats. Sporidial mating and the infection process on compatible barley plants, cv. Hannchen, were investigated using light microscopy and scanning and transmission electron microscopy. Within 2 h after mixing of sporidia of opposite mating types on water agar, polar conjugation tubes emerged that subsequently fused, producing infection hyphae at the junctions. Similar events occurred on germinated barley shoots, although sporidia regularly produced several conjugation tubes, of which only one was involved in mating. Tubes emerging from the sides of cells were also observed. Infection hyphae emerged from either the conjugation tube or conjugated cell body. Hyphae elongated along the shoot surface until characteristic crook and appressorium-like structures were formed. An invading hypha emerged beneath this structure and directly penetrated the underlying epidermal cell. Hyphae extended both intra- and inter-cellularly into tissues, without much branching, before becoming established in the shoot meristematic region. Plant plasma membranes remained intact during pathogen ingress and an electron-dense matrix of unknown origin appeared in the interface between plant plasma membrane and invading hypha. A large fungal biomass was generated in the host spike tissue at 4263 days postinoculation during the development of the floral meristem.Key words: Hordeum vulgare, pathogen, sporidia, teliospores, ultrastructure, Ustilaginales.
Selfed-seed production depending on individual size and flowering sequence in Iris gracilipes (Iridaceae)
Authors: Kimura Takashi , Ishii Hiroshi S , Sakai Satoki
Published: November 2002

To examine the influence of individual size and time of pollination on selfed and outcrossed seed production, we conducted hand-pollination experiments in 2000 and 2001 in the perennial herb Iris gracilipes A. Gray (Iridaceae). Small individuals produced outcrossed seeds to a greater extent than selfed seeds, whereas large individuals produced not only outcrossed seeds but also selfed seeds. On the other hand, when half of all flowering shoots of an individual were removed, both selfed and outcrossed seeds were produced independent of individual size. Flowers that opened earlier within the same flowering shoots were likely to produce outcrossed seeds, while those that opened later within the same flowering shoots produced relatively more selfed seeds than did the flowers which opened earlier. Thus, the ratio of the numbers of selfed to outcrossed seeds produced may differ between small and large individuals. These results suggest that plants regulate selfed- and outcrossed-seed production depending on their sizes and flowering sequence.Key words: self-fertilization, individual size, flowering sequence, Iris gracilipes.
Characterization of anAvenaisolate ofMagnaporthe griseaand identification of a locus conditioning its specificity on oat
Authors: Oh H S , Tosa Y , Takabayashi N , Nakagawa S , Tomita R , Don L D , Kusaba M , Nakayashiki H , Mayama S
Published: November 2002

An isolate of Magnaporthe grisea was collected from a blast lesion on oat in Brazil. Sequence analysis of the rDNA-ITS-2 region and DNA fingerprinting with repetitive elements revealed that the Avena isolate belongs to the "crop isolate group" and is similar to Triticum isolates. At high temperature (28°C), the Avena isolate caused severe disease symptoms on primary leaves of oat and wheat. When the temperature was decreased to 20°C, wheat leaves expressed resistance to the Avena isolate. Cytologically, this temperature-dependent resistance was associated with an increase in the incidences of papilla formation and a hypersensitive reaction. Pathogenicity tests with various plant species at 20°C revealed that the Avena isolate is exclusively parasitic on oat. To elucidate genetic mechanisms of this species-specific parasitism, the Avena isolate was crossed with a Triticum isolate and resulting F1progenies were subjected to pathogenicity tests on oat seedlings. In the F1population, avirulent and virulent cultures segregated in a 1:1 ratio, suggesting that the specific parasitism on oat is controlled by a single gene. This locus was designated as Pat1.Key words: Magnaporthe grisea, species-specific parasitism, oat, temperature sensitive.
Differential effects of acorn burial and litter cover onQuercus rubrarecruitment at the limit of its range in eastern North America
Authors: García Daniel , Bañuelos María-José , Houle Gilles
Published: November 2002

Primary predators or dispersers such as birds and rodents cache acorns of northern red oak (Quercus rubra L.). A proportion of these acorns are not retrieved, and thus, animals may favour oak regeneration by placing acorns in microsites suitable for recruitment. We experimentally investigated the effects of acorn burial and litter cover on red oak recruitment at two sites at the northern limit of the species' range in North America. Laboratory experiments also tested the effects of acorn burial and litter cover on desiccation and germinability and the influence of soil moisture on germination. Burial and litter protected acorns against predation by deer in the field. Germination was promoted by burial both in field and laboratory experiments. Germination was proportional to acorn water content and to soil moisture. Seedling emergence in the field was enhanced by burial but reduced by litter cover. Acorns buried but uncovered by litter had the highest probability of recruiting a seedling. A potential effect of seed predators or dispersers on red oak regeneration and expansion is suggested, as acorn caching by birds and rodents may actually enhance population recruitment, despite high mortality through acorn consumption.Key words: acorn burial, litter, microsite effects, recruitment, northern red oak, southern Quebec.
The effect of spatially variable overstory on the understory light environment of an open-canopied longleaf pine forest
Authors: Battaglia Michael A , Mou Pu , Palik Brian , Mitchell Robert J
Published: November 2002

Spatial aggregation of forest structure strongly regulates understory light and its spatial variation in longleaf pine (Pinus palustris Mill.) forest ecosystems. Previous studies have demonstrated that light availability strongly influences longleaf pine seedling growth. In this study, the relationship between spatial structure of a longleaf pine forest and spatial pattern of understory light availability were investigated by comparing three retention harvest treatments: single-tree, small-group, large-group, and an uncut control. The harvests retained similar residual basal area but the spatial patterns of the residual trees differed. Hemispherical photographs were taken at 300 stations to calculate gap light index (GLI), an estimate of understory light availability. Stand-level mean, variation, and spatial distribution of GLI were determined for each treatment. By aggregating residual trees, stand mean GLI increased by 20%, as well as its spatial variation. Spatial autocorrelation of GLI increased as the size of the canopy gaps increased and the gaps were better defined; thus, the predictability of GLI was enhanced. The ranges of detrended semivariograms were increased from the control to the large-group harvest indicating the spatial patterns of understory GLI became coarser textured. Our results demonstrated that aggregated canopy structure of longleaf pine forest will facilitate longleaf pine seedling regeneration.
A calibrateable site index model for Pinus kesiya plantations in southeastern Africa
Authors: Eerikäinen Kalle , Mabvurira Danaza , Nshubemuki Ladislaus , Saramäki Jussi
Published: November 2002

The aim of the study was to develop a site index model for Pinus kesiya Royle ex Gordon plantations in southeastern Africa based on the relationship between the dominant height and stand age. Conversely, analysis of dominant height and age data showed that the growth patterns of plantations were different. In addition, the asymptotes and forms of standwise dominant height curves varied within plantations. In developing a common site index model, instead of using the more common approach of estimating separate dominant heightage models for different plantations or sites, a mean curve approach based on a linear random parameter model with fixed and random parameters was applied. The random parameter model of this study was calibrated by predicting random parameters for the plantation and stand effects, in accordance with the standard linear prediction theory. The analyses showed that the calibration of the dominant height model was an efficient method to obtain reliable dominant height predictions of a stand, particularly when several dominant heightage observations from different stands of a plantation and at least one measured dominant height and stand age of a target stand are available. This is the case in many forest inventories based on temporary samples, i.e., cross-sectional data. The new site index model is a useful tool for use in different mensurational applications, and its properties can efficiently be utilized for example in forest inventories of P. kesiya plantations in southeastern Africa.
A spatial statistical analysis of cork oak competition in two Portuguese silvopastoral systems
Authors: Paulo M J , Stein A , Tomé M
Published: November 2002

This paper considers competition among cork oaks (Quercus suber L.) at three plots in two representative Portuguese stands. It uses spatial point pattern functions to describe densities and quantify differences among stands. Relations between cork oak characteristics and indices measuring intertree competition are modelled. Tree competition has a significant effect on tree crown characteristics. In particular, cork oaks with much competition have smaller and more elongated crowns. A standard model that relates crown diameter with diameter at breast height was improved. The R2 value increased from 0.53 to 0.63 by including a crown shape parameter and competition indices.
Eighty years of change: vegetation in the montane ecoregion of Jasper National Park, Alberta, Canada
Authors: Rhemtulla Jeanine M , Hall Ronald J , Higgs Eric S , Macdonald S Ellen
Published: November 2002

Repeat ground photographs (taken in 1915 and 1997) from a series of topographical survey stations and repeat aerial photographs (flown in 1949 and 1991) were analysed to assess changes in vegetation composition and distribution in the montane ecoregion of Jasper National Park, in the Rocky Mountains of Alberta, Canada. A quantitative approach for assessing relative vegetation change in repeat ground photographs was developed and tested. The results indicated a shift towards late-successional vegetation types and an increase in crown closure in coniferous stands. Grasslands, shrub, juvenile forest, and open forests decreased in extent, and closed-canopy forests became more prevalent. The majority of forest stands succeeded to dominance by coniferous species. Changes in vegetation patterns were likely largely attributable to shifts in the fire regime over the last century, although climatic conditions and human activity may also have been contributing factors. Implications of observed changes include decreased habitat diversity, increased possibility of insect outbreaks, and potential for future high-intensity fire events. Results of the study increase knowledge of historical reference conditions and may help to establish restoration goals for the montane ecoregion of the park.
Fire frequency and vegetation dynamics for the south-central boreal forest of Quebec, Canada
Authors: Lesieur Daniel , Gauthier Sylvie , Bergeron Yves
Published: November 2002

Fire history and forest dynamics were reconstructed for a 3800-km2 territory located in the south-central boreal forest of Quebec. Fire cycle was characterized using a random sampling strategy combined with archival data on fires that had occurred since 1923 on private land owned by Smurfit-Stone. Bioclimatic subdomain, land use, surficial deposit, and mean distance from a firebreak did not affect the fire cycle. Fire cycles have been longer since the end of the Little Ice Age (~1850). Warming after the Little Ice Age seems to have triggered a change in fire frequency. Forest dynamics were characterized by transition matrices for changes in dominant canopy composition from 344 permanent sampling plots. These permanent plots were sampled approximately every 15 years over the preceding 40 years. We observed two distinct patterns of replacement: (i) deciduous and mixed stands were replaced by balsam fir (Abies balsamifera (L.) Mill.) (and, to a lesser extent, by black spruce (Picea mariana (Mill.) BSP)) and (ii) jack pine (Pinus banksiana Lamb.) was replaced by black spruce. Analyses confirm that species replacement occurs in the eastern boreal forest of Canada when the fire-return interval is long enough and that the substrate plays an important role along with other disturbances, such as insect outbreaks. Our results also suggest that the proportion of old-growth forests (>100 years old) in the landscape should increase as a result of the lengthening of the fire cycle. More and more stands are likely to experience species replacement. From the standpoint of sustainable forest management, this perspective calls into question the widespread use of clear-cutting in the boreal forest. Regional context must be taken into account in forest management if the conservation of biodiversity and ecosystem integrity are serious objectives. Economically and ecologically sound silvicultural scenarios that emulate natural processes are discussed.
White tree rings formed in trembling aspen saplings following experimental defoliation
Authors: Hogg E H , Hart M , Lieffers V J
Published: November 2002

Recent studies of trembling aspen (Populus tremuloides Michx.) in western Canada have shown a correlation between past insect defoliation events and the formation of narrow, abnormally pale-coloured ("white") tree rings. The objectives of this study were to test the hypothesis that defoliation causes the formation of white rings and to examine how defoliation affects ring width and density. We experimentally defoliated 7- to 18-year-old aspen in June, July, or August 1997 and subsequently found that white rings were formed the same year in all aspen that were severely defoliated in early June. These white rings were much narrower than in adjacent trees left as controls, and mean xylem density of the white rings (0.27 g·cm3) was significantly reduced relative to normal rings (0.350.40 g·cm3). In the year following defoliation, the tree rings remained narrow, but their appearance and density had returned to normal. Aspen defoliated later in the season formed relatively normal rings in 1997, but ring widths were reduced in 1998. The results confirm that white rings in aspen can be a useful retrospective indicator of the severe, early season defoliation that is typical during major outbreaks of forest tent caterpillar (Malacosoma disstria Hbn.) and other insects.
Comparison of some annual forest inventory estimators
Authors: Van Deusen Paul C
Published: November 2002

Three estimators of current status and trend are compared for an annual interpenetrating panel design. The five-panel annual inventory design is simulated over a 10-year period with flat, increasing, and quadratic growth trends. The simulated comparisons show that the mixed estimator performs well relative to the 5-year moving average in terms of bias and mean squared error in all cases. The one-panel mean can have less bias than the moving average when there is a trend, but it is more variable. The moving average tends to lag evolving trends, which can result in very large bias.
Dynamics of an old-growth, fire-initiated, subalpine forest in southern interior British Columbia: tree size, age, and spatial structure
Authors: Antos Joseph A , Parish Roberta
Published: November 2002

We used dendrochronological analysis of over 2000 trees in four 50 × 50 m plots to reconstruct the history and dynamics of a 330-year-old, fire-initiated spruce-fir forest. All lodgepole pine (Pinus contorta Dougl. ex Loud.), half of the canopy Engelmann spruce (Picea engelmannii Parry ex Engelm.), but less than 10% of the canopy subalpine fir (Abies lasiocarpa (Hook.) Nutt.) dated from the first 50 years of stand development. Tree-ring patterns of individual surviving trees showed no evidence of disturbance during the first 200 years after stand initiation; subsequently, episodes of disturbance are indicated by periods of release in understory fir. Although many fir owe their canopy position to release after disturbance, few canopy fir in the current stand established in response to either the stand-initiating event or subsequent partial disturbances. A seedling bank of long-lived fir appears critical to the dynamics of this forest. In contrast, establishment of almost all canopy spruce can be related to disturbance. This stand, although fire initiated, was structured primarily by a combination of partial disturbances and autogenic processes. We suspect that most old, fire-initiated stands in many forest regions are similarly structured and emphasize that the contribution of partial disturbances and autogenic processes should be fully assessed when examining their dynamics or managing such forests.
Genetic resistance of Eucalyptus globulus to autumn gum moth defoliation and the role of cuticular waxes
Authors: Jones T H , Potts B M , Vaillancourt R E , Davies N W
Published: November 2002

This study investigated the association between resistance of Eucalyptus globulus Labill. to autumn gum moth (Mnesempala privata Guenée) defoliation and cuticular wax compounds. In a field trial consisting of clonally replicated F2 families of E. globulus, situated in Tasmania, Australia, significant genetic variation in resistance was detected in two of three F2 families. The broad-sense heritability for defoliation within families ranged from 0.24 to 0.33. The 15 most resistant and the 15 most susceptible genotypes within each variable family were compared for their relative levels of 26 cuticular wax compounds. While no significant correlation between resistance and total wax yield estimates was found, significant differences were detected between resistant and susceptible classes in the relative quantities of several aliphatic phenylethyl and benzyl wax esters within both families. This association does not appear to be a response induced by defoliation. The broad-sense heritabilities of the variation in these compounds were high (0.820.94). Our findings suggest that these wax compounds are a mechanism of genetic resistance to autumn gum moth in E. globulus.
Influence of age on growth efficiency of Tsuga canadensis and Picea rubens trees in mixed-species, multiaged northern conifer stands
Authors: Seymour Robert S , Kenefic Laura S
Published: November 2002

Well-known patterns in the fundamental relationship between tree-level stemwood volume increment (VINC) and projected leaf area (PLA) are examined and quantified for Tsuga canadensis (L.) Carrière (eastern hemlock) and Picea rubens Sarg. (red spruce) growing in managed, mixed-species, multiaged stands in east-central Maine, U.S.A. Both species follow a sigmoid pattern, suggesting a peak growth efficiency (GE, stemwood volume growth per unit of PLA) in mid- to upper-canopy trees with PLAs of less than half that of the largest trees sampled. Tree age negatively influenced the VINCPLA relationship in the expected manner: at a given PLA, older trees produce less stemwood than younger ones. The combined effect of leaf area and age is accurately modeled with a Weibull-like function in which the asymptote is an index of tree maturity defined as tree age relative to an estimated maximum for the species. Although previous studies have independently documented both the sigmoid relationship between VINC and PLA and the negative effect of age, their conclusions have been confounded by the strong correlation between age and mean tree PLA. This study addresses both issues simultaneously, and is the first to demonstrate a decline in GE with age independent from the effect of increasing PLA.