Photosynthetic differences between saplings and adult trees: an integration of field results by meta-analysis

Ontogenetic changes in gas exchange parameters provide both insight into mechanisms underlying tree growth patterns, and data necessary to scale environmental impacts on young trees to predict responses of older trees. We present a quantitative review and meta-analysis of field measurements of gas exchange parameters in saplings and mature trees of 35 tree species (seven conifers, seven temperate deciduous trees, and 21 tropical evergreen trees). Data for saplings were obtained in both understory environments and open areas or large gaps. We also present data on ontogenetic changes in photosynthesis for Pseudotsuga menziesii (Mirb.) Franco and Tsuga heterophylla (Raf.) Sarg., species of particular interest because of their large maximal heights and long life-spans. Among tree species, there is evidence for both ontogenetic increases and ontogenetic decreases in photosynthetic capacity on a leaf area basis (A(area)). Overall, A(area) is generally higher for upper-canopy leaves of adult trees than for saplings, especially in temperate deciduous trees. However, the pattern for photosynthetic capacity on a leaf mass basis (A(mass)) is the reverse of that observed for A(area). Saplings of both conifers and broad-leaved trees, even when acclimated to low-light conditions, characteristically have a higher A(mass) than adult trees. This pattern is driven largely by an ontogenetic increase in leaf mass per unit area (LMA), as found in 100% of studies reviewed. Data for Pacific Northwest conifers, although including measurements on some of the tallest trees studied, did not differ greatly from patterns found in other tree species. We conclude that ontogenetic changes in LMA are the single most consistent difference between saplings and adult trees, and that changes in LMA and related aspects of leaf morphology may be critical to understanding both variation in gas exchange during tree growth, and stage-dependent responses of trees to environmental change.     

Surgical treatment of an intramedullary spinal cord hamartoma in a dog

A 9-year-old spayed female Golden Retriever was examined because of progressive hind limb lameness. Magnetic resonance imaging of the thoracic and lumbar portions of the vertebral column revealed a focal, contrast-enhancing, intramedullary spinal cord mass. The history, signalment, and magnetic resonance findings were suggestive of spinal cord neoplasia. A hemilaminectomy, durotomy, and longitudinal myelotomy were performed, and a 1 X 1-cm mass that contained numerous blood vessels was removed with blunt dissection. Results of histologic examination and immunohistochemical staining of the mass suggested that it was a hamartoma. The dog improved after surgery, with no evidence of a recurrence of clinical signs 14 months after surgery. Vascular malformations of the CNS in dogs include hamartomas, hemangiomas, angiomas, hemangioblastomas, meningocerebral hemangiomatosis, and arteriovenous malformations. A hamartoma is a non-neoplastic overgrowth of cells or an improper proportion of cells that are normally in the involved tissue. Although magnetic resonance imaging may be helpful in determining the extent of the lesion in dogs with vascular malforrmations, it cannot be used to distinguish neoplastic from non-neoplastic formations. Excision may result in a good outcome for dogs with an intramedullary spinal cord hamartoma.     

A severe outbreak of respiratory tract disease associated with bovine respiratory syncytial virus probably enhanced by vaccination with modified live vaccine

A severe outbreak of respiratory tract disease associated with bovine respiratory syncytial virus (BRSV) on a large beef-fattening farm is described. The outbreak started two days after five- to seven-month-old calves were vaccinated with a modified live BRSV vaccine. The disease ran a very severe course among five- to seven-month-old vaccinated calves, but disease was absent in eight-month-old an older non-vaccinated calves. The presence of IgM antibodies in sera of non-vaccinated calves indicated that BRSV was spreading on the farm between two to 15 days before the day of vaccination. The data indicate that vaccination with modified live vaccine during the course of a natural infection may enhance the severity of disease. The possible pathogenesis of the disease is discussed.     

Effects of pretreating broad bean leaflets with decenylsuccinic acid on subsequent attack by Botrytis fabae

Pretreating with decenylsuccinic acid (DSA) increased numbers of lesions developing whenVicia faba leaflets were inoculated with conidia ofBotrytis fabae. The increase is partly attributed to an effect on conidial germination. More conidia germinated on DSA than on water-prepreated leaflets, an effect associated with greater concentrations of sugars and amino acids in leachates from the former.Samenvatting Eén van de blaadjes van het jongste tweetallige blad van een tuinbouwplant werd voor de inoculatie met conidiën vanBotrytis fabae gedurende 2 uur ondergedompeld in een 3×10^–5M decenylbarnsteenzuuroplossing (DSA), het andere blaadje van het bladpaar in gedistilleerd water. Op de met DSA behandelde blaadjes waren 24 uur na de inoculatie meer vlekjes aanwezig dan op de met water behandelde (Tabel 2). Deze verhoging van de vatbaarheid moet voor een deel worden toegeschreven aan een effect op de ontkieming van de conidiën op het blad. Hogere percentages ontkiemde conidiën werden gevonden op de met DSA behandelde blaadjes (Tabel 3). Dit zou het gevolg kunnen zijn van een grotere afgifte van kiemingsbevorderende stoffen door het met DSA behandelde blaadje in vergelijking met een met water behandeld (Tabel 1).     

Detection of silver protein complex injections in the bovine udder using x-ray fluorescence: A preliminary investigation

To determine the feasibility of using x-ray fluorescence (XRF) to detect the presence of silver in the mammary gland of dairy cows injected with mild silver protein suspension. The XRF spectroscopy was conducted on cadaver udders with and without mild silver protein injected. Spectral analysis was performed in order to determine the amplitude of the silver K-alpha peak that was detected. By comparing the amplitude of the K-alpha peak to the background, a minimum time of collection was determined, as a measure of the time required to observe a silver signal that is significantly non-zero. The minimum detection time required for evidence of injected silver suspension was calculated to be 2.8 +/- 0.2 s. Even with an additional requirement that the net signal exceed 50 counts, the clear indication of the presence of silver will be observed within 4 min of interrogation. X-ray fluorescence spectroscopy was shown to be a viable method for the detection of injected silver protein in cadaver mammary glands of dairy cows. While these findings are promising, further studies must be conducted to investigate the time dependence of the silver signal when diffusion, absorption, and redistribution are involved, under conditions that better mimic those encountered at an exhibition. This technique, used in conjunction with screening ultrasound examinations, has the potential to confirm sites of injection of silver compounds.     

An outbreak of low pathogenic avian influenza in a mixed-species aviculture unit in Dubai in 2005.

This case describes an outbreak of low pathogenic hemagglutinin 9 neuraminidase 2 avian influenza virus (AIV) in two white-bellied bustards (Eupodotis senegalensis), one stone curlew (Burhinus oedicnemius), and a blacksmith plover (Antibyx armatus) in a private zoologic collection in Dubai, United Arab Emirates. The four birds showed signs of respiratory disease, and all died as a result of disease or euthanasia. Attention has been paid to the diagnostic process and common differential diagnosis for upper respiratory tract disease in bustards, curlews, and plovers. To the knowledge of the authors, AIV has not been previously described in these species.     

Management of anorexia in dogs and cats.

The management of anorexia should center first on the urgent and emergent medical management of the patient and be followed by feeding of a highly palatable food in a low-stress environment and manner. Diet palatability can potentially be improved by increasing dietary moisture, fat, or protein, and, in the dog, by adding sugar or salt as well as by using a variety of fresh, pleasantly aromatic, and uncommon foods. Caution should be used when increasing or adding nutrients that may be harmful to patients with specific diseases. Concurrent drug therapy that may reduce appetite should be minimized, and physical barriers to eating should be removed. Patients that consume less than resting energy requirement of longer than 3 to 5 days with no trend toward improving should receive parenteral or enteral nutrition.     

Successful treatment of atlantooccipital luxation in an alpaca (Lama pacos).

A 7-mo-old male alpaca (Lama pacos) presented with an abnormal lowered posture of the head and neck and reluctance to walk. Cervical radiographs demonstrated atlantooccipital luxation. Successful manual closed reduction was achieved while the animal was anesthetized, resulting in complete return to normal gait and posture.     

Diagnosis of chronic myelogenous leukemia in a dog using morphologic,cytochemical, and flow cytometric techniques

Abstract: Chronic myelogenous leukemia was diagnosed in a 3.5-year-old neutered male Golden Retriever. The diagnosis was based on persistent leukocytosis (>73.0×10³/μL), composed of a proportionate left shift to pro-granulocytes with no evidence of underlying inflammation, infection, or neoplasia. Marked dysplasia was evident in neutrophils and platelets in peripheral blood. Bone marrow and splenic aspirates were dominated by mature and immature neutrophils with < 2% myeloblasts. Cytochemical and flow cytometric assays confirmed that cells in the peripheral blood and spleen were of committed neutrophil lineage. The dog responded initially to treatment with hydroxyurea, but developed acute undifferentiated leukemia approximately 83 days after initial presentation.