bluuebunny/crossref_metadata_2025 huggingface dataset:
The antilymphangiogenic effect of aqueous humour
Authors: BOCK FB , ONDERKA JO , DIETRICH TD , BACHMANN BB , HOS DH , CURSIEFEN CC
Published: October 2007

Purpose: The cornea, which is free of blood and lymphatic vessels bathes on the endothelial site in the Aqueous humor (AqH). Because of the direct contact of AqH to the cornea, we wanted to know whether it could prevent ingrowths of blood and, especially, lymphatic vessels into the cornea.

Methods: In vitro: quantifying lymphatic endothelial cell (LEC) proliferation with a colorimetric (BrdU) proliferation ELISA with 5 or 20 μl of human AH and as control EGM‐2MV medium. In vivo: murine model of inflammatory corneal neovascularization; treatment group (n=5) received 3 μl of murine AH once a day at day of surgery and for the following three days(control saline solution). After five days, mice were sacrificed. Corneal flat mounts were stained with LYVE‐1 as a specific lymphatic vascular endothelial marker and CD31 as panendothelial marker. Morphometry of blood and lymphatic vessels was performed with the image analysis software analySIS^B.

Results: Human AH inhibited the proliferation of the lymphatic endothelial cells in vitro in a dose dependent manner (5μl: p>0.0847 n.s; 20μl: p< 0.0001). The topical application of aqueous humour inhibited the outgrowth of blood vessels significant (P < 0.006) in comparison to the control. The outgrowth of lymphatic vessels was also inhibited significant (P< 0.0002).

Conclusions: AH inhibits the proliferation of lymphatic endothelial cells in vitro and the outgrowth of blood and lymphatic vessels in the cornea in vivo. Tissues like the cornea, the iris and the ciliary body are naturally free of blood and, moreover, lymphatic vessels. Therefore, the aqueous humour seems to play an important role to avoid the ingrowths of blood and lymphatic vessels into the anterior chamber and its adjacent tissues.
Comparison of Icare, dynamic contour tonometer, and ocular response analyzer with goldmann applanation tonometer.
Authors: VANDEWALLE E , STALMANS I , VANDENBROECK S , ZEYEN T
Published: October 2007

Purpose: To compare the intraocular pressure (IOP) readings taken with the ICare tonometer, the Pascal Dynamic Contour Tonometer (DCT), and the Ocular Response Analyzer (ORA) with the Goldmann Applanation Tonometer (GAT). To evaluate the influence of central corneal thickness (CCT) on the IOP measurements.

Methods: In a prospective study 93 eyes of 93 patients attending the glaucoma clinic were examined. Patients were randomly divided into four groups to vary the order in which the tonometers were applied. CCT was measured with an ultrasound pachymeter (Pachmate). A multivariate normal model was used to compare the mean IOP measurements between the four instruments. Spearman correlation coefficients were used to assess the correlation between IOP measurements and CCT. Bland‐Altman plots were used to assess the agreement between the tonometry methods.

Results: The average CCT was 558 ±47.4 μm. The mean IOP for GAT, ICare, DCT, and ORA (Goldmann correlated IOP) were 15.1 ±4.8, 15.7 ±5.7, 18.3 ±5.1, and 18.3 ±6.6 mmHg respectively. There was no significant difference between the mean IOP obtained with GAT and ICare (p=0.44), nor between DCT and ORA (p=0.99). There was no correlation between the IOP measurements and CCT for the four instruments. Bland‐Altman graphs show disagreement between the measurements taken by the four tonometers.

Conclusions: IOP readings from ICare are in accordance with those from GAT, whereas DCT readings correspond well to (Goldmann correlated) ORA measurements. DCT and ORA readings both overestimate IOP measured with GAT.
Diclofenac effect on conjunctival goblet cells density after LASIK
Authors: RODRIGUEZ AE , RODRIGUEZ‐PRATS JL , MEZQUIDA G , ALIO JL
Published: October 2007

Purpose: Dry eye is a common condition after LASIK surgery, and in previous studies we have demonstrated a great decrease of the goblet cell population after LASIK. Taking into account that dry eye syndrome has an inflammatory origin we performed this study with Diclofenac 0,1% after LASIK surgery .

Methods: 40 patients scheduled for LASIK surgery were included into two groups. In 20 of them the flap was made with a mechanical microkeratome, M2 (Moria), and in the other 20 patients the flaps were made by femtosecond laser (IntraLase). Topical Diclofenac 0,1% was applied twice a day for two months following LASIK surgery only in the left eye of the patients. Artificial tears were used 4 times a day in both eyes. Goblet cell count in conjunctiva and inflammatory cells were studied by impression cytology pre‐operatively, at one, two and three months after surgery.

Results: Analysis by impression cytology of the ocular surface showed a decrease in the inflammation after surgery in the eyes treated with Diclofenac 0,1%. The goblet cell count in both groups decreased after LASIK surgery, however there were no statistically significant differences between left and right eyes of patients at any time in the goblet cell count in any of them.

Conclusions: Diclofenac 0,1% decreased inflammation in the treated eyes, however no differences were found with this treatment in the conjunctival goblet cell count .
Neural and behavioral mapping of the visual field in true and simulated visual field deficits
Authors: KOZAK LR , SZATMARY G , VIDNYANSZKY Z
Published: October 2007

Purpose: Our goal was to assess the utility of functional magnetic resonance imaging (fMRI) in simultaneous mapping of perceptual and neural visual field deficits, and in the assessment of neural plasticity processes underlying spontaneous and medication‐induced visual field recovery.

Methods: Neural function of two patients with predominantly unilateral visual field deficits and three volunteers with simulated scotomas was assessed using fMRI retinotopic mapping procedures. In the patients behavioral testing has also been done by asking for reports in a forced choice manner on the color of a 1.66° diameter circle patch pseudo‐randomly overlaid on the standard fMRI retinopic mapping stimuli.

Results: Retinotopic mapping provided a reliable voxel‐based quantification of the extent of both real and simulated visual field deficits. The pattern of BOLD responses in retinotopic visual cortical areas – in particular in the primary visual cortex – showed close correlation with the performance in the perimetry tests, and the behavioral responses obtained during scanning. Moreover, we found a marked difference between true and simulated visual field deficits.

Conclusions: The presented fMRI retinotopic mapping techniques are suitable for the simultaneous assessment of the functional and behavioral aspects of visual field loss, thus providing an opportunity to investigate neural plasticity in affected patient populations.
Strategies to prevent anophthalmic socket contraction in retinoblastoma patients
Authors: TUNC M
Published: October 2007

Purpose: The combination of enucleation plus irradiation often leads to a significant orbital volume loss and severe enophthalmos in retinoblastoma patients. Our purpose is to discuss the strategies to prevent anophthalmic socket related complications.

Methods: In this retrospective study we reviewed our retinoblastoma patients who underwent enucleation. We evaluated the enucleation technique, possible causes and preventive factors for anophthalmic socket contraction.

Results: In our clinic, four patients developed severe anophthalmic socket contraction following retinoblastoma treatment. One of these patients had bilateral enucleation and three patients had only one eye removal. The patient who had bilateral enucleation also had external orbital irradiation. All patients had small orbital implants (12 to 14 mm in diameter) and smaller orbital volumes. One patient had severe ectropion and one patient had severe entropion with granuloma formation.

Conclusions: Surgical technique, adjunctive radiotherapy, implant diameter, orbital growth retardation and fat atrophy are important factors in development of anophthalmic socket contraction in retinoblastoma patients. Most of these factors are preventable with appropriate surgical approach in enucleation.
Antimicrobial peptides on the ocular surface in health and disease
Authors: ABEDIN A , MOHAMMED I , DUA HS
Published: October 2007

Purpose: Antimicrobial peptides (AMPs) are the eukaryotic analogues of antibiotics and of paramount importance in host defence. We report herein the expression of a spectrum of AMPs at the ocular surface in infective conditons compared to controls.

Methods: RNA obtained from impression cytology samples of conjunctival and corneal epithelial cells of normal persons and of patients with bacterial, viral, acanthamoeba and dry eye disease underwent reverse‐transcription‐ Polymerase Chain Reaction (PCR) to assess expression of the AMPs HBD‐1 to ‐4( Human Beta Defensin),Dermicidin, LL‐37 (or Cathelicidin), LEAP‐1 and LEAP‐2 (Liver Expressed Antimicrobial Peptide) and a number of putative AMPs.

Results: HBD‐1 and ‐2 were universally expressed in both health and disease. HBD‐3 was seen only occasionally in infection and not in controls and seemed to be commonly expressed in dry eye disease. LL‐37 occurred in both normals and infective groups but the level of expression was variable and was less in acanthamoeba infection. Likewise LEAP‐1 and ‐2 were commonly seen both in control and infection and appeared to be more strongly expressed i the former. The latter AMPs, i.e., the putative AMPs were not expressed.

Conclusions: AMPs have a distinct profile on the ocular surface as opposed to other mucosal surfaces and different disease conditions appear to further modify gene expression. In contrast to other surfaces HBD‐1 and ‐2 both appear to be constitutively expressed on the ocular surface and other AMPs are more storngly expressed in certain disease states than others whereas others are more common in control groups than in infective conditions.
Intermediate and combined forms of retinal telangiectasies
Authors: ZOGRAFOS L
Published: October 2007

Purpose: Idiopathic retinal telangiectasis are usually classified as Leber ‐ Coats disease or juxtafoveal telangiectasies. Intermediate and combined forms of these vascular disorders are rare and poorly described and understood.

Methods: Clinical presentation of four cases of congenital telangiectasies associated to pigment epithelium disorders, two cases associated with optic disc anomalies, nine cases of multifocal progressive retinal telangiectasies and six cases of junctional congenital retinal telangiectasies.

Results: Clinical presentations of four types of poorly described and understood congenital retinal telangiectasies considering fluorescein angiography pattern and therapeutic approach.

Conclusions: Intermediate and combined forms of congenital retinal telangiectasies are highly interesting in order to attend a more accurate classification of these disorders based on presumed etiopathogenic mechanisms.
Growth factor signalling and regulation of lens cell differentiation
Authors: MCAVOY JW , STUMP RJW , ANG S , CHEN Y , LOVICU FJ
Published: October 2007

Studies on explanted lens epithelial cells have been central to the identification of growth factor families that play key roles in determining the differentiated states of lens cells. In vitro models have shown that quiescent epithelial cells can be induced to differentiate down the normal fibre differentiation pathway by FGF, or induced to undergo an epithelial mesenchymal transition (EMT) that is a key feature of subcapsular cataracts (including PCO) by TGFß. Central to the generation of these divergent phenotypes is reorganisation of the lens cell cytoskeleton. Recent studies in our laboratory have identified key roles for the Wnt growth factor family in regulating the lens cell cytoskeleton. Transgenic mice that overexpress the Wnt signalling inhibitor, secreted frizzled‐related protein 2 (Sfrp2), specifically in the lens, develop cataract and microphthalmia and exhibit a severely disrupted lens cellular architecture. The epithelial sheet is reduced and disordered. The lens fibre compartment is severely disrupted and it is notable that fibres do not elongate and undergo directed cell migration to form sutures. This is reflected in the absence of aligned microtubules and disrupted expression/activity of components of Wnt/planar cell polarity (PCP) signalling cascades including small GTPases (Cdc42, Rac1 and RhoA) and phospho‐JNK. These results have highlighted an important role for Wnt/PCP signalling in orchestrating the development of the highly ordered lens cellular architecture.
Alpha‐Crystallins and their role in cataract and other diseases
Authors: HORWITZ J
Published: October 2007

In spite of intensive work trying to elucidate the 3 dimensional structure of alpha‐crystallin, we still do not have a high‐resolution structure. This is because alpha‐crystallin is ploydispersed and cannot be crystallized. We can infer its structure from other small heat‐shock proteins belonging to the alpha‐crystallins family that were crystallized. To study its function in the lens, we are at present using a genetic approach. Xiaohua Gong and his collaborators have recently identified 2 mouse cataractous mutant lines. One such mutation is αA‐R54C, and the second is αA‐Y118D. The two mutations cause a recessive and a dominant cataract respectively. The first mutation (αA‐R54C) which is in N‐terminal region of alpha‐crystallin seem to affect lens epithelial and fiber cell during development, the αA‐Y118D mutation which is in the “α‐crystallin domain” of the molecule affect the interaction of alpha‐crystallin with the other major lens crystallins namely beta and gamma‐crystallins. This approach and these kinds of animal models will help us understand the multiple roles of the alpha‐crystallin in the lens and in the other tissues. The involvement of alpha‐crystallin in age‐related macular degeneration and various types of cancer will also be discussed.
The effect of laser on retinal oxygenation (animal studies)
Authors: POURNARAS CJ
Published: October 2007

Purpose: To discuss the effect of laser on the retinal oxygen distribution, in experimental animal models.

Methods: Transretinal and preretinal O2 measurments were obtained by O2 sensitive micro‐electrodes in anesthetized animal models. The effect of laser photogoagulation on the oxygen preretinal and transretinal distribution and retinal oxygen consumption, within normal and post experimental ischemic micro‐angiopathies retinas, were calculated.

Results: Laser photocoagulation, resulting to pigment epithelium and photoreceptors layers disruption, reduces the outer retina’s demand for O2 and nutrients. Transretinal PO2 measurements confirm changes of the tranretinal PO2 grandients distribution. O2 diffusing from the choroid, non consumpted by the outer retinal layers reaches the inner retina, resulting to PO2 raise in preretinal areas and in the inner healthy retinal layers of experimental animal and relieve retinal hypoxia in experimental BRVO in mini‐pigs and cats. Improvement of inner retinal oxygenation affect the retinal circulation resulting to retinal vessels constriction and restoration of retinal blood flow regulation.

Conclusions: Laser photocoagulation improves the inner retinal layers oxygenation thus reversing tissue hypoxia and improving the retinal blood flow regulation in retinas with ischemic micro‐angiopathies. Reversal of retinal tissue hypoxia and restoration of retinal blood flow regulation potentially affect the evolution of the macular edema related to ischemic microagiopathies.
The eyes – Doors to the world
Authors: ECKER B , GERBER G , REINELT T
Published: October 2007

Our eyes are the sense organs which provide us with the greatest perspective of our world. Therefore they are deemed to be the most intellectual of our sense organs. But through our eyes we can understand only to a certain extent. We need the use of other senses which come together, stabilize and are rooted in our neurophysiological system. The eyes are an important door to the world which inspires and motivates to further discovery and invention. They create aspects of motivation dealing with perception, combinations of distant, nearby and internal senses which are the basis for increasing the depth of our knowledge and true understanding. We also want to emphasize the emotional side of those interna‐lised, neurophysiological, “bio‐psychic representations” (Gerber/Reinelt 1989). Emotions are created within us ‐ fear, joy, panic, visions, dreams and much more. This “Power of internal images” (Huether, 2006) is our partner on our way. Each psycho‐therapy works at these basics to differenciate, to change these emotions with whatever motivation created them. In addition, we will show, based on “Constructivism”(Foerster, 1999), that in each of us there arise subjectiv realities, which are individual and not objective.

But what happens when we are unable to see with our eyes? When one is blind or visually handicapped? As a result of these questions we want to describe our project “Theatre for Everyone“ in the Viena Schauspielhaus with Airan Berg as director with Walther Schorn and Birgit Ecker in cooperation with the professors Gisela Gerber and Toni Reinelt as scientifique co‐ordinators from the University of Viena. Connie Ederer und Clemens Desero are the student’s co‐ordinators. This project has been developed since 2005 for visually handicapped and blind people, enabling them to attend the theatre with the assistence of students.
Effect of Silver Content on the Structure and Antibacterial Activity of Silver-Doped Phosphate-Based Glasses
Authors: Valappil Sabeel P. , Pickup David M. , Carroll Donna L. , Hope Chris K. , Pratten Jonathan , Newport Robert J. , Smith Mark E. , Wilson Michael , Knowles Jonathan C.
Published: October 2007

Staphylococcus aureus
can cause a range of diseases, such as osteomyelitis, as well as colonize implanted medical devices. In most instances the organism forms biofilms that not only are resistant to the body's defense mechanisms but also display decreased susceptibilities to antibiotics. In the present study, we have examined the effect of increasing silver contents in phosphate-based glasses to prevent the formation of
S. aureus
biofilms. Silver was found to be an effective bactericidal agent against
S. aureus
biofilms, and the rate of silver ion release (0.42 to 1.22 μg·mm
−2
·h
−1
) from phosphate-based glass was found to account for the variation in its bactericidal effect. Analysis of biofilms by confocal microscopy indicated that they consisted of an upper layer of viable bacteria together with a layer (∼20 μm) of nonviable cells on the glass surface. Our results showed that regardless of the silver contents in these glasses (10, 15, or 20 mol%) the silver exists in its +1 oxidation state, which is known to be a highly effective bactericidal agent compared to that of silver in other oxidation states (+2 or +3). Analysis of the glasses by
31
P nuclear magnetic resonance imaging and high-energy X-ray diffraction showed that it is the structural rearrangement of the phosphate network that is responsible for the variation in silver ion release and the associated bactericidal effectiveness. Thus, an understanding of the glass structure is important in interpreting the in vitro data and also has important clinical implications for the potential use of the phosphate-based glasses in orthopedic applications to deliver silver ions to combat
S. aureus
biofilm infections.
Activity of a Potent Hepatitis C Virus Polymerase Inhibitor in the Chimpanzee Model
Authors: Chen Chih-Ming , He Yupeng , Lu Liangjun , Lim Hock Ben , Tripathi Rakesh L. , Middleton Tim , Hernandez Lisa E. , Beno David W. A. , Long Michelle A. , Kati Warren M. , Bosse Todd D. , Larson Daniel P. , Wagner Rolf , Lanford Robert E. , Kohlbrenner William E. , Kempf Dale J. , Pilot-Matias Tami J. , Molla Akhteruzzaman
Published: October 2007

A-837093 is a potent and specific nonnucleoside inhibitor of the hepatitis C virus (HCV) nonstructural protein 5B (NS5B) RNA-dependent RNA polymerase. It possesses nanomolar potencies in both enzymatic and replicon-based cell culture assays. In rats and dogs this compound demonstrated an oral plasma half-life of greater than 7 h, and its bioavailability was >60%. In monkeys it had a half-life of 1.9 h and 15% bioavailability. Its antiviral efficacy was evaluated in two chimpanzees infected with HCV in a proof-of-concept study. The design included oral dosing of 30 mg per kg of body weight twice a day for 14 days, followed by a 14-day posttreatment observation. Maximum viral load reductions of 1.4 and 2.5 log10copies RNA/ml for genotype 1a- and 1b-infected chimpanzees, respectively, were observed within 2 days after the initiation of treatment. After this initial drop in the viral load, a rebound of plasma HCV RNA was observed in the genotype 1b-infected chimpanzee, while the genotype 1a-infected chimpanzee experienced a partial rebound that lasted throughout the treatment period. Clonal analysis of NS5B gene sequences derived from the plasma of A-837093-treated chimpanzees revealed the presence of several mutations associated with resistance to A-837093, including Y448H, G554D, and D559G in the genotype 1a-infected chimpanzee and C316Y and G554D in the genotype 1b-infected chimpanzee. The identification of resistance-associated mutations in both chimpanzees is consistent with the findings of in vitro selection studies, in which many of the same mutations were selected. These findings validate the antiviral efficacy and resistance development of benzothiadiazine HCV polymerase inhibitors in vivo.
National and Regional Assessment of Antimicrobial Resistance among Community-Acquired Respiratory Tract Pathogens Identified in a 2005-2006 U.S. Faropenem Surveillance Study
Authors: Critchley Ian A. , Brown Steven D. , Traczewski Maria M. , Tillotson Glenn S. , Janjic Nebojsa
Published: October 2007

Surveillance studies conducted in the United States over the last decade have revealed increasing resistance among community-acquired respiratory pathogens, especially
Streptococcus pneumoniae
, that may limit future options for empirical therapy. The objective of this study was to assess the scope and magnitude of the problem at the national and regional levels during the 2005-2006 respiratory season (the season when community-acquired respiratory pathogens are prevalent) in the United States. Also, since faropenem is an oral penem being developed for the treatment of community-acquired respiratory tract infections, another study objective was to provide baseline data to benchmark changes in the susceptibility of U.S. respiratory pathogens to the drug in the future. The in vitro activities of faropenem and other agents were determined against 1,543
S. pneumoniae
isolates, 978
Haemophilus influenzae
isolates, and 489
Moraxella catarrhalis
isolates collected from 104 U.S. laboratories across six geographic regions during the 2005-2006 respiratory season. Among
S. pneumoniae
isolates, the rates of resistance to penicillin, amoxicillin-clavulanate, and cefdinir were 16, 6.4, and 19.2%, respectively. The least effective agents were trimethoprim-sulfamethoxazole (SXT) and azithromycin, with resistance rates of 23.5 and 34%, respectively. Penicillin resistance rates for
S. pneumoniae
varied by region (from 8.7 to 22.5%), as did multidrug resistance rates for
S. pneumoniae
(from 8.8 to 24.9%). Resistance to β-lactams, azithromycin, and SXT was higher among
S. pneumoniae
isolates from children than those from adults. β-Lactamase production rates among
H. influenzae
and
M. catarrhalis
isolates were 27.4 and 91.6%, respectively. Faropenem MICs at which 90% of isolates are inhibited were 0.5 μg/ml for
S. pneumoniae
, 1 μg/ml for
H. influenzae
, and 0.5 μg/ml for
M. catarrhalis
, suggesting that faropenem shows promise as a treatment option for respiratory infections caused by contemporary resistant phenotypes.
Neutrophils Play an Important Role in Host Resistance to Respiratory Infection with
Acinetobacter baumannii
in Mice
Authors: van Faassen Henk , KuoLee Rhonda , Harris Greg , Zhao Xigeng , Conlan J. Wayne , Chen Wangxue
Published: October 2007

Acinetobacter baumannii
has emerged as a major cause of both community-associated and nosocomial pneumonia, but little is known about the cellular and molecular mechanisms of host defense against respiratory infection with this bacterial pathogen. In this study, we examined the role of neutrophils in host resistance to pulmonary
A. baumannii
infection in a mouse model of intranasal (i.n.) infection. We found that neutrophils were rapidly recruited to the lungs following i.n. inoculation of the pathogen and declined to baseline level upon clearance of the infection. Depletion of neutrophils using monoclonal antibody RB6-8C5 prior to infection resulted in an acute lethal infection that was associated with enhanced bacterial burdens in the lung (
P
< 0.05) and extrapulmonary dissemination to the spleen. The increased susceptibility to
A. baumannii
in neutropenic mice was associated with a delay in the mRNA expression and production of early proinflammatory cytokines such as tumor necrosis factor alpha, interleukin-6, keratinocyte chemoattractant protein, monocyte chemoattractant protein 1, and macrophage inflammatory protein 2 (MIP-2) in the lungs and development of severe bronchopneumonia and lymphoid tissue destruction in the spleen. Moreover, i.n. administration of the neutrophil-inducing chemokine MIP-2 to normal mice induced a pulmonary influx of neutrophils and significantly enhanced the clearance of
A. baumannii
from the lungs (
P
< 0.01). These results imply that neutrophils play a critical role in host resistance to respiratory
A. baumannii
infection.
Contribution of
Moraxella catarrhalis
Type IV Pili to Nasopharyngeal Colonization and Biofilm Formation
Authors: Luke Nicole R. , Jurcisek Joseph A. , Bakaletz Lauren O. , Campagnari Anthony A.
Published: October 2007

Moraxella catarrhalis
is a gram-negative mucosal pathogen of the human respiratory tract. Although little information is available regarding the initial steps of
M. catarrhalis
pathogenesis, this organism must be able to colonize the human mucosal surface in order to initiate an infection. Type IV pili (TFP), filamentous surface appendages primarily comprised of a single protein subunit termed pilin, play a crucial role in the initiation of disease by a wide range of bacteria. We previously identified the genes that encode the major proteins involved in the biosynthesis of
M. catarrhalis
TFP and determined that the TFP expressed by this organism are highly conserved and essential for natural transformation. We extended this initial study by investigating the contribution of TFP to the early stages of
M. catarrhalis
colonization. TFP-deficient
M. catarrhalis
bacteria exhibit diminished adherence to eukaryotic cells in vitro. Additionally, our studies demonstrate that
M. catarrhalis
cells form a mature biofilm in continuous-flow chambers and that biofilm formation is enhanced by TFP expression. The potential role of TFP in colonization by
M. catarrhalis
was further investigated using in vivo studies comparing the abilities of wild-type
M. catarrhalis
and an isogenic TFP mutant to colonize the nasopharynx of the chinchilla. These results suggest that the expression of TFP contributes to mucosal airway colonization. Furthermore, these data indicate that the chinchilla model of nasopharyngeal colonization provides an effective animal system for studying the early steps of
M. catarrhalis
pathogenesis.
The ecology of Rhizocarpon superficial. II. The seasonal response of net photosynthesis and respiration to temperature, moisture, and light
Authors: Coxson D. S. , Kershaw K. A.
Published: October 2007

The seasonal gas-exchange response matrix for the crustaceous lichen Rhizocarpon superficiale (Schaer.) Vain, is presented. Maximum rates for net photosynthesis of ca. 1 mg CO2 g−1 h_1 are generated at 900 μE m−2 s−1 illumination between 50 and 60% relative thallus moisture content and at thallus temperatures of 14 °C down to 1 °C, during all seasons of the year. This broad response to temperature as well as the apparently high resistance to heat stress in Rhizocarpon is discussed in relation to the special characteristics of its boundary-layer habitat. The absence of any seasonal photosynthetic capacity change is discussed in terms of the constraint imposed by the random fluctuations in the thermal operating environment of the lichen. We postulate that the predictability of the operating environment largely determines the extent and the level of any photosynthetic adaptation.
Shoot development in Betula papyrifera. I. Short-shoot organogenesis
Authors: Macdonald Alastair D. , Mothersill D. H.
Published: October 2007

Buds and developing branches of Betula papyrifera were collected weekly from mature trees during three successive growing seasons. Material was prepared to show stages of bud inception, development, and flushing and female inflorescence inception. Short shoots develop from (i) proximal axillary buds on long shoots (ii) short-shoot terminal buds, or (iii) axillary buds on flowering short shoots. An axillary bud apex forms a terminal bud after bud burst. An axillary bud possesses one outer rudimentary leaf, but all other short-shoot buds have three outer rudimentary leaves. All short-shoot buds possess, in addition, one–three embryonic foliage leaves and, distally, three primordial rudimentary leaves which form the outermost appendages of the succeeding terminal bud. Rudimentary leaf stipules form the cataphylls. Foliage leaf primordia are initiated in May – early June and rudimentary leaves arise in late June – July. If a bud apex is initiated in year n, female inflorescence induction occurs in late June of year n + 1 or any succeeding year. An axillary bud develops on a short shoot as a consequence of flowering; it is initiated concurrently with inflorescence development and its development is completed during flowering and seed maturation. Short- and long-shoot buds can be distinguished, upon dissection, in mid-July when buds are forming. Hence, determination of potential long and short shoots occurs the year before bud burst.
An integrating sphere for the rapid nondestructive estimation of whole-plant chlorophyll content
Authors: Macdowall F. D. H.
Published: October 2007

The chlorophyll contents of seedlings of several plant species were estimated from the voltages emitted by a photocell before and after the insertion of the shoot systems into a 61-cm integrating sphere. Red light of 675-nm wavelength was projected into the sphere for selective absorption by chlorophyll, as shown by an absorption spectrum, and the readout was calibrated against total extracted chlorophyll. The species and thus the morphology of the plant were of no significant consequence. The absorbance by chlorophyll in plants obeyed Beer's law up to a content of about 60 mg chlorophyll; however, over a wider range the calibration curve for absorbance, like that for absorptance, was best fitted by a quadratic equation which gave a coefficient of determination of 98% and a standard error of estimate for chlorophyll of 2 mg. A band width of 4 mg chlorophyll was obtained between the 95% confidence limits for chlorophyll as a function of absorbance of plants that contained less than 20 mg chlorophyll. A similar 4-mg confidence belt for chlorophyll on absorptance applied through the range of about 5 to 45 mg chlorophyll in plants. A usable linear relation was obtained between chlorophyll content and the ratio of the scattered light not absorbed at 750 nm to that at 675 nm.
Fusarium toxins in field corn. I. Time course of fungal growth and production of deoxynivalenol and other mycotoxins
Authors: Miller J. David , Young J. Christopher , Trenholm H. Locksley
Published: October 2007

The formation of the trichothecene mycotoxins deoxynivalenol and 15-acetyldeoxynivalenol and zearalenone in field corn inoculated with Fusarium graminearum was studied over a growing season. The mycotoxins, ergosterol, colony forming units, weight, moisture, and ash contents were measured in the infected ears. Measurements of toxins and ergosterol in infected plants, weather data, and analyses of the soil mycoflora were also taken. In the infected ears, fungal propagule counts rapidly increased up to 6 weeks after inoculation and then sharply declined. Ergosterol concentrations followed the propagule data for the first 6 weeks and then levelled off (at about 70 ppm). Deoxynivalenol concentrations increased (to about 580 ppm), over the same period and then declined (to about 430 ppm); 15-acetyldeoxynivalenol concentrations rose rapidly in the first 2 weeks (to 64 ppm) and then slowly declined (to 20 ppm); an appreciable amount of zearalenone (10 ppm) was not observed until 9 weeks after inoculation. The data indicated that the relative and absolute concentrations of the two trichothecenes present in the corn may have been affected by the plant, and toxins were found throughout the plant but mainly in the infected part.
A new Amoebophilus (Zygomycetes) ectoparasitic on amoebae
Authors: Barron G. L.
Published: October 2007

Amoebophilus simplex is described as an ectoparasite of amoebae recovered from rotten wood. The short-cylindrical to subclavate conidium attaches by one end to the pellicle of the host, penetrates with a slender germ tube, and produces a lobed haustorium to anchor the thallus and absorb nutrient. Simple or branching chains of conidia are produced from near the apex of the infecting spore. The fungus produces small, polyhedral zygospores which originate from elongate progametangia arising from the conidia in older infections.
Effects of simulated acid rain on pollen germination and pollen tube growth of white spruce (Picea glauca)
Authors: Sidhu S. S.
Published: October 2007

The effects of simulated rain of pH 2.6 to 5.6 on pollen germination and pollen tube growth were studied in white spruce (Picea glauca (Moench) Voss.) under three temperature regimes. Results indicate that little or no adverse effects were produced on germination and pollen tube growth by acid rain of pH above 3.6 during release or germination. However, rain of equal to or less than pH3.6 reduced germination by up to 30% in pollen washed with acid rain and germinated on normal agar medium. Germination was reduced further and pollen tube growth strongly inhibited in pollen germinated on agar medium prepared with acid rain of equal to or less than pH 3.6.
Freeze-induced fluctuations in xylem sap pressure in Acer pseudoplatanus
Authors: O'Malley P. E. R. , Milburn J. A.
Published: October 2007

Xylem sap pressures in response to temperature changes were investigated in Acer pseudoplatanus L., the British sycamore. Mature trees were used for field experiments; excised seedling stem segments were used in the laboratory. A general correlation was observed between changes in pressure potential (ψp) of the xylem sap of mature trees and ambient temperatures above zero (freezing point). More outstanding, however, were the characteristic decreases in pressure potential observed in response to subzero air temperatures. Investigation of this phenomenon under controlled conditions using excised stem segments revealed that rapid decreases in sap pressure occurred simultaneously with freezing. Freezing caused the stem wood to absorb water. This is a surprising response because water expands on freezing. Subsequently exudation of sap was triggered by thawing. Freezing and thawing responses appeared to be similar whether stem segments were collected during summer, when the xylem sap contained no detectable sugars, or during winter, when sugars were present in the sap. Apparently water uptake or replenishment (termed "conditioning") during cooling is of paramount importance in determining the capability of maple wood to exude sap. The freeze-induced uptake of sap under negative pressures described here is considered to be the process fundamental to conditioning.
Vertical zonation of Sphagnum mosses along hummock-hollow gradients
Authors: Andrus Richard E. , Wagner Daniel J. , Titus John E.
Published: October 2007

The vertical distributions of nine Sphagnum species and four associated mosses in two bogs (Adirondack Mountains, New York) were analyzed for interspecific and interbog differences. Based on 4300 sample points, Sphagnum mean heights ranged from 12 to 43 cm above the water table and the sequence of species was similar in both bogs (S. cuspidatum and S. majus) < (S. fallax and S. angustifolium) < (S. magellanicum, S. rubellum, and S. russowii) < (S. fuscum and S. nemoreum). However, at Bloomingdale Bog, a relatively dry mire with many well-developed hummocks and narrow hollows, mosses had significantly greater means (by 4-12 cm) than at Raybrook Bog, a relatively wet mire with wide Sphagnum carpets and fewer hummocks. South- and east-facing hummock slopes tended to be gentler than the north and west slopes, but the mosses’ mean heights did not vary with aspect. The abundance of hummocks at Bloomingdale seems responsible for not only the greater mean heights, but also for broader ranges and greater vertical overlap with other species. However, the ability of each species to dominate a certain array of height classes did not differ between bogs. Within each bog, hummock species tended to have larger vertical ranges than hollow species, implying a lesser ability of hollow mosses to tolerate the full range of conditions along the hummock-hollow gradient.
Karyotypic analysis of Polymyxa betae (Plasmodiophoromycetes) based on serial thin sections of pachytene nuclei
Authors: Braselton James P.
Published: October 2007

Three pachytene nuclei of Polymyxa betae Keskin were reconstructed from serial thin sections. Thirty synaptonemal complexes (SCs) were counted, indicating a haploid chromosome number of 30. SCs of Polymyxa were similar to those of Sorosphaera veronicae Schroeter and Membranosorus heterantherae Ostenfeld and Peterson but differed from SCs of Plasmodiophora brassicae Woron. and Woronina pythii Goldie-Smith.
A scanning electron microscopic study of the external features of perithecium development in Sordaria humana
Authors: Read N. D.
Published: October 2007

The external features of perithecium development in Sordaria humana have been examined with the scanning electron microscope. Variations in specimen preservation were evident after using different preparative procedures. Different stages of perithecium development were correlated with culture age. The developmental sequence was as follows. An ascogonial coil was initiated as a side branch of a vegetative hypha and became enclosed by enveloping hyphae originating from one or more locations. The enveloping hyphae of the resultant spherical protoperithecium gave rise to fringe hyphae and, after cohesion, to the protoperithecium peridium. The neck was first evident as a bulge on the fruit body surface. Ostiolar pore formation soon followed. Neck extension primarily involved the differentiation of periphyses, lining the ostiolar canal, into the coherent cells of the neck peridium. A positive neck phototropism resulted from the differential growth of periphyses. Neck hyphae often grew from the base of the neck peridium. Neck development was sometimes terminated by ostiolar pore occlusion. The different cellular elements observed have been classified into two basic types: (i) discrete hyphae and hyphallike elements which exhibit a pronounced longitudinal type of growth pattern; and (ii) coherent elements which arise by the cohesion of adjacent hyphae or hyphallike elements.
The effects of nesting gulls on the vegetation and soil of islands in the Great Lakes
Authors: Hogg E. H. , Morton J. K.
Published: October 2007

The effects of nesting colonies of the Ring-billed Gull (Larus delawarensis Ord.) on vegetation and soil nutrients were monitored over a 4-year period on Barrier Island and other islands in Georgian Bay and Lake Huron, in the Great Lakes region of Canada. Nesting had a profound effect on the vegetation and species composition. Two distinct communities of annual alien species dominated the nesting sites, one flowering in May and June and the other from late August to October. Native species were rare in the nesting sites, in contrast to adjacent areas, where perennial native grasses were dominant. Factors favouring the replacement of indigenous vegetation by annual aliens include physical disturbance by gulls during nesting and deposition of guano, which caused dramatic increases in the levels of soil nutrients. Plant succession in nesting sites that had been abandoned for 3 and 4 years was characterized by a rapid decline in the abundance of annual aliens and their replacement by perennials. After the 2nd year native perennial grasses were dominant. Nutrient levels in the soil rapidly returned to near normal, except for phosphorus, which persisted at high levels. Herring Gull (Larus argentatus Pontoppidan) nests were also studied. Their density was much lower, and hence their effects were less pronounced. However, they supported a similar annual alien flora. Herring Gulls frequently nested on unvegetated cobble or gravel shores where the humus from the nests permitted the establishment of a permanent vegetation.
Ascocarp induction in a natural auxotroph of a predatory fungus
Authors: Zachariah K.
Published: October 2007

A natural auxotroph of Arthrobotrys dactyloides with an absolute requirement for several amino acids was isolated from forest soil. When combined with a prototrophic strain the putative heterokaryon had growth characteristics differing from those of either component. With a second prototroph, the putative heterokaryon acquired the ability to produce sterile apothecia. The possibility is discussed that the auxotroph is essential to the initiation of sexual morphogenesis in these anamorphs.
Excretion of a natural inhibitor of anthocyanin synthesis during germination of mung bean seedlings
Authors: Dumortier Françoise M. , Vendrig Jan C.
Published: October 2007

A natural inhibitor of anthocyanin synthesis has been found in seeds of mung beans (Vigna radiata). The inhibitor might play an important role in the regulation of anthocyanin accumulation in seedlings. It is mainly localized in the seed coat and in the cotyledons and is excreted in the incubation medium soon after sowing. Removal of the inhibitor by rinsing the seedlings and transferring them to fresh medium results in higher anthocyanin accumulation as compared with seedlings left in the original incubation medium. Addition of the inhibitor 12 h after its removal does not affect anthocyanin accumulation when the seedlings have been grown in complete darkness. On the other hand, anthocyanin accumulation initiated by irradiation with red light is inhibited under these conditions. The inhibitor has been partially purified and some of its chemical characteristics were determined from its behaviour during purification.
Characteristics of pea leaves and their relationships to photosynthetic CO2 exchange in the field
Authors: Mahon J. D. , Hobbs S. L. A. , Salminen S. O.
Published: October 2007

Photosynthetic CO2 exchange rate (CER) was determined in attached leaflets of field-grown peas (Pisum sativum L.) Three populations of genotypes were studied in different field locations and years. In 1 year, CER, leaf characteristics, and meteorological factors were measured in parallel at different times of the day and season. Differences in CER across environments or time of day were related to differences in stomatal resistance; however, changes during the season, which might be of environmental or developmental origin, were not. Genotype ranking for CER was largely independent of measuring time, field location, and year. None of the leaf characters which have been suggested as simple assays for photosynthetic ability (specific leaf weight, chlorophyll content, stomatal resistance) was consistently related to CER over several tests. In the single experiment in which they were determined, ribulose bisphosphate carboxylase activity, leaf soluble protein content, and the difference in CER at 2 and 20 kPa O2 were also not correlated with CER. The O2 effect expressed as a percentage of CER at 2 kPa O2 and the slope of the light response above 50 nE cm−2 s−1 were significantly correlated to CER, but neither is suitable for predicting CER in different genotypes. A significant multiple regression of CER on stomatal resistance, total chlorophyll, and ribulose bisphosphate carboxylase activity suggests that the genetic control of CER may involve several characters. In this case, direct determination of CO2 exchange may be the easiest and most reliable way of assessing genetic differences in photosynthetic performance.
The depth profile of a shoreline seed bank in Matchedash Lake, Ontario
Authors: Nicholson Anne , Keddy Paul A.
Published: October 2007

Sediment cores were collected from the shore of Matchedash Lake, Simcoe Co., Ontario, on 15 May 1981. Each core was separated into seven depth classes, 0–2, 2–4, 4–6, 6–8, 8–10, 14–16, and 19–21 cm. These classes from each of 49 cores were placed in plastic pots and the seeds in them were allowed to germinate under greenhouse conditions. After 17 weeks, 1458 seedlings representing at least 25 species had germinated; 81% occurred in the top 2 cm of the sediment cores. Both the number of seedlings and the number of species declined rapidly with depth. Seedlings of the following species were most abundant: Eriocaulon septangulare With., Juncus effusus L., Panicum lanuginosum Ell., and Rhynchospora fusca (L.) Ait. Of the remaining species, only two were woody, and each of these was represented by a single seedling. The distribution of germinable seeds in this seed bank indicates that Matchedash Lake has an exceptionally shallow seed bank in relation to other aquatic systems.
Petiole growth in Ranunculus sceleratus: the role of growth regulators and the leaf blade
Authors: Samarakoon Ananda B. , Horton Roger F.
Published: October 2007

In the presence of the leaf blades, excised petioles of the semiaquatic celery-leaved buttercup Ranunculus sceleratus L. elongate when submerged, or when treated in air with indoleacetic acid (IAA), gibberellin A3 (GA3), or C2H4 alone or in combination, responses that are similar to those obtained using intact plants. Isolated petiole sections do not respond to C2H4, but are responsive in the presence of low levels (10−6 mol L−1) IAA. Gibberellin A3 is less active than IAA in promoting growth or in sensitizing the petiole tissue to C2H4.
The cytology of Audouinella hermannii (Rhodophyta, Florideophyceae). I. Vegetative and hair cells
Authors: Hymes Beverly J. , Cole Kathleen M.
Published: October 2007

A cytological study was conducted on the freshwater red alga Audouinella hermannii (Roth) Duby (Acrochaetiales) from the North Alouette River, British Columbia. Cell division and elongation occurred exclusively in apical cells of the primary axis, branches, and branchlets; new cell wall material was produced at the tip of the cells. Six chromosomes were counted in vegetative cells. The fine structure of vegetative cells was similar to that of the few other florideophycean algae studied to date. Ultrastructure of apoplastic hair cell development was recorded for the first time in the Rhodophyta. Mature hair cells were long and characterized by a thin wall, a large proximal vacuole, and cytoplasm concentrated at the distal end containing a large central nucleus, active dictyosomes, and an abundance of endoplasmic reticulum, and mitochondria.
The cytology of Audouinella hermannii (Rhodophyta, Florideophyceae). II. Monosporogenesis
Authors: Hymes Beverly J. , Cole Kathleen M.
Published: October 2007

Monosporogenesis was described for the first time in the Florideophyceae in the freshwater species Audouinella hermannii (Roth) Duby (Acrochaetiales). Three morphological stages were observed in the developing sporangium, ascribed mainly to activities of the endomembrane system (dictyosomes, endoplasmic reticulum, and plasmalemma). Based on the few published reports of rhodophytan sporangia, excluding nuclear activities, differentiation in this florideophycean monosporangium was similar to monosporogenesis in the Bangiophyceae and to carposporogenesis and tetrasporogenesis in the Florideophyceae.