Neurotrophic Effects of l-DOPA in Postnatal Midbrain Dopamine Neuron/Cortical Astrocyte Cocultures

Abstract: l -DOPA is toxic to catecholamine neurons in culture, but the toxicity is reduced by exposure to astrocytes. We tested the effect of l -DOPA on dopamine neurons using postnatal ventral midbrain neuron/cortical astrocyte cocultures in serum-free, glia-conditioned medium. l -DOPA (50 µ M ) protected against dopamine neuronal cell death and increased the number and branching of dopamine processes. In contrast to embryonically derived glia-free cultures, where l -DOPA is toxic, postnatal midbrain cultures did not show toxicity at 200 µ M l -DOPA. The stereoisomer d -DOPA (50–400 µ M ) was not neurotrophic. The aromatic amino acid decarboxylase inhibitor carbidopa (25 µ M ) did not block the neurotrophic effect. These data suggest that the neurotrophic effect of l -DOPA is stereospecific but independent of the production of dopamine. However, l -DOPA increased the level of glutathione. Inhibition of glutathione peroxidase by l -buthionine sulfoximine (3 µ M for 24 h) blocked the neurotrophic action of L-DOPA. N -Acetyl- l -cysteine (250 µ M for 48 h), which promotes glutathione synthesis, had a neurotrophic effect similar to that of l -DOPA. These data suggest that the neurotrophic effect of l -DOPA may be mediated, at least in part, by elevation of glutathione content.     

Ragweed sensitization alters pulmonary vascular responses to bronchoprovocation in beagle dogs

Theodorou, Andreas, Natalie Weger, Kathleen Kunke, KyooRhee, David Bice, Bruce Muggenberg, and Richard Lemen. Ragweed sensitization alters pulmonary vascular responses to bronchoprovocation in beagle dogs. J. Appl. Physiol.83(3): 912-917, 1997.In ragweed (RW)-sensitized beagle dogs, wetested the hypothesis that reactivity of the pulmonary vasculature wasenhanced with aerosolized histamine (Hist) and RW. Seven dogs wereneonatally sensitized with repeated intraperitoneal RW injections, and12 dogs were controls (Con). The dogs were anesthetizedwith intravenous chloralose, mechanically ventilated, and instrumentedwith femoral arterial and pulmonary artery catheters. Specific lungcompliance(CL_sp),specific lung conductance (G_sp),systemic vascular resistance index, and pulmonary vascular resistanceindex (PVRI) were measured before and after bronchoprovocation withHist and RW. After Hist inhalation (5 breaths of 30 mg/ml), both Conand RW dogs had significant (P < 0.05) decreases inCL_sp(51 ± 4 and 53 ± 5%, respectively) andG_sp (65 ± 5 and69 ± 3%, respectively), but only RW-sensitized dogs had asignificant increase in PVRI (38 ± 10%). After RW inhalation (60 breaths of 0.8 mg/ml), only RW-sensitized dogs had significant increases (62 ± 20%) in PVRI and decreases inG_sp (77 ± 4%) and CL_sp(65 ± 7%). We conclude that, compared with Con,RW-sensitized beagle dogs have increased pulmonary vasoconstrictiveresponses with Hist or RW inhalation.

     

Respiratory muscle reserve in rats during heavy exercise

Gosselin, Luc E., David Megirian, Joshua Rodman, DonnaMueller, and Gaspar A. Farkas. Respiratory muscle reserve in ratsduring heavy exercise. J. Appl.Physiol. 83(4): 1405-1409, 1997.The extent towhich the respiratory pump muscles limit maximal aerobic capacity inquadrupeds is not entirely clear. To examine the effect of reducedrespiratory muscle reserve on aerobic capacity, whole bodypeak oxygen consumption(O_{2 peak}) wasmeasured in healthy Sprague-Dawley rats before and after Sham,unilateral, or bilateral hemidiaphragm denervation (Dnv) surgery.O_{2 peak} wasdetermined by using a graded treadmill running test.Hemidiaphragm paralysis was verified after testing byrecording the absence of electromyographic activity duringinspiration. Before surgery, O_{2 peak} averaged 86, 87, and 92 ml · kg¹ · min¹for the Sham, unilateral, and bilateral Dnv groups, respectively. Twoweeks after surgery, there was no significant change inO_{2 peak} foreither the Sham or unilateral Dnv group. However,O_{2 peak} decreased~19% in the bilateral Dnv group 2 wk after surgery. These findingsstrongly suggest that the pulmonary system in rats is designed suchthat during heavy exercise, the remaining respiratory pump muscles areable to compensate for the loss of one hemidiaphragm, but not of both.

     

Seasonality of feeding activity in Antarctic suspension feeders

The feeding activity of four benthic suspension-feeding groups (bryozoans, hydroids, polychaetes and holothurians) was monitored in situ every month for a 2-year period at Signy Island in the maritime Antarctic. The bryozoans were monitored at species level, whereas the other taxa could be differentiated only to genus. A marked seasonal variation in feeding activity was observed in most taxa. Although environmental parameters such as sea water temperature, fastice duration and water column chlorophyll concentrations suggested that winter in the maritime Antarctic lasts for about 6 months, many animals ceased feeding only for a short period of 2 or 3 months around the middle of the austral winter (June/July). These suspension feeders must therefore be efficient at utilising the low concentration of the microplankton existing in the water column for much of the year. Comparison with environmental variables suggested several possible cues for changes in feeding activity, but these cues may differ between taxa. Photoperiod and changes in disturbance by water movement (both mediated by ice), and food concentration are likely to be important environmental cues for polar suspension feeders.     

Prothrombin cleavage by human vascular smooth muscle cells: A potential alternative pathway to the coagulation cascade

Thrombin is a potent mitogen for human vascular smooth muscle cells (HVSMC) and its enzymatic activity is required for this function. The present study demonstrates that prothrombin is also mitogenic for HVSMC due to the generation of enzymatically active thrombin which occurs upon incubation of prothrombin with the cells. Analysis by SDS-PAGE, immunoblotting, and amino acid sequencing revealed that prothrombin incubated with HVSMC undergoes limited proteolysis. Prethrombin 1 was formed through cleavage at R¹⁵⁵-S¹⁵⁶. Cleavage at R²⁷¹-T²⁷² generated fragment 1.2 and prethrombin 2 whilst cleavage at R²⁸⁴-T²⁸⁵ yielded truncated prothrombin 2 (prethrombin 2′). However, cleavage at R³²⁰-I³²¹ which, during prothrombin activation produces two-chain α-thrombin, was not detectable. Studies on HVSMC-conditioned medium revealed that a similar pattern of prothrombin cleavage occurred by a cell-secreted factor(s). Amidolytic activity analysis indicated that 1–3% catalytically active thrombin-like activity was generated upon incubation of prothrombin with HVSMC-conditioned medium. By treating conditioned medium with various classes of proteinase inhibitors or hirudin, it was determined that prothrombin is cleaved by a cell-derived serine proteinase-like factor(s) at R²⁷¹-S²⁷² and by α-thrombin at R¹⁵⁵-S¹⁵⁶ and R²⁸⁴-T²⁸⁵. Antibodies neutralising the activity of either urokinase, tissue plasminogen activator, or factor Xa failed to alter the prothrombin cleaving activity of conditioned medium. This activity which may catalyse an alternative pathway for the generation of thrombin, was eluted from a gel filtration column as a single peak with apparent molecular mass of 30–40 kDa. © 1995 Wiley-Liss, Inc.     

Quantitative assessment of pair formation behavior in captive whooping cranes (Grus americana)

Instantaneous scan sampling for mean distance and synchronous action patterns and all-occurrence sampling for unison call, dance, strut, and hoover-up behaviors were conducted for five potential whooping crane pairs at Patuxent Environmental Science Center, Laurel, Maryland. Dance, strut, and hoover-up differed among pairs, as did total frequency of social behaviors. It was unclear whether or not total frequency of social behaviors during pair formation can be used as an index for potential breeding success. The relative importance of different action patterns should be used as indices of pair compatibility in captive whooping cranes. © 1995 Wiley-Liss, Inc.     

Infection ofArabidopsis thaliana ecotype columbia by tomato spotted wilt virus

Mechanical inoculation ofArabidopsis thaliana ecotype Columbia with tomato spotted wilt virus led to viral replication and spread as determined by dot blot and ELISA analysis. Severe symptoms were observed three to four weeks post-inoculation. Early symptoms were manifested as chlorotic spots on uninoculated leaves. Later in the infection process, some plants showed complete chlorosis and wilting prior to bolting. Bolts that were developed by infected plants were chlorotic and deformed. These preliminary results suggest thatA. thaliana could become a model system for the genetic analysis of host factors required for the replication of viruses in the family Bunyaviridae, which includes viruses that cause important diseases of both plants and animals.     

Complex interaction between different proteinaceous components within the cell-wall structure ofCandida albicans

We have previously described a monoclonal antibody, MAb DC3:H10, which recognized an epitope preferentially expressed on the surface ofCandida albicans germ tubes. In the present study we examined the MAb-reactive material further. Immunoblot analysis of the material purified partially by Sephadex G-200 and DEAE-Sephacel chromatography reacted with antibodies to theC. albicans C3d receptor (CR2). In an ELISA, MAb DC3:H10 captured antigen that was recognized by both anti-CR2 and anti-mp58 fibrinogen binding mannoprotein polyclonal antibodies. The MAb DC3:H10 failed to compete with either of these antisera in an ELISA. Indirect immunofluo-rescence (IIF) analysis showed differences in surface distribution for the MAb DC3:H10, the CR2, and the mp 58 epitopes. Dual labeling IIF experiments showed MAb DC3:H10 binding to be unaffected by binding of fibrinogen or anti-mp58 antibody. However, the binding patterns of MAb DC3:H10 were modified in the presence of anti-CR2 antibody, suggesting a complex interaction between these cell wall components.