Pollen tube pathway through the gynoecium of Monotropsis odorata (Monotropaceae)

Monotropsis odorata Elliott. is one of the most cryptic and relatively rare North American endemic species of the Monotropaceae; therefore, information concerning the biology of this achlorophyllous, mycotrophic angiosperm is limited. Bright field and fluorescence microscopic investigations of postpollination gynoecia reveal that pollen tubes follow a continuous pathway from the receptive surface of the stigma to micropyles of the ovules. The pollen tube pathway is characterized by discrete strands of transmitting tissue connecting an exudate-coated stigma to an exudate-filled, stylar canal that leads directly to exudate-coated placentae. Pollen tube growth appears restricted to those areas associated with an exudate. The gynoecial pathway for pollen tube growth in this taxon conforms to those described from other monotropàceous species.     

REHABILITATION AND RELEASE OF MARINE MAMMALS IN THE UNITED STATES: RISKS AND BENEFITS

Rehabilitation of stranded marine mammals elicits polarized attitudes: initially done alongside display collections, but release of rehabilitated animals has become more common. Justifications include animal welfare, management of beach use conflict, research, conservation, and public education. Rehabilitation cost and risks have been identified that vary in degree supported by data rather than perception. These include conflict with fisheries for resources, ignorance of recipient population ecology, poor understanding of long-term survival, support of the genetically not-so-fit, introduction of novel or antibiotic-resistant pathogens, harm to human health, and cost. Thus facilities must balance their welfare appeal against public education, habitat restoration, human impact reduction, and other conservation activities. Benefits to rehabilitating marine mammals are the opportunity to support the welfare of disabled animals and to publish good science and so advance our understanding of wild populations. In specific cases, the status of a population may make conservation the main reason for rehabilitation. These three reasons for rehabilitation lead to contrasting, and sometimes conflicting, management needs. We therefore outline a decision tree for rehabilitation managers using criteria for each management decision, based on welfare, logistics, conservation, research, and funding to define limits on the number of animals released to the wild.     

In vivo effects of lipopolysaccharide and TLR4 on platelet production and activity: implications for thrombotic risk.

Gram-negative bacteria release LPS, which activates Toll-like-receptor-4 (TLR4) in the host, initiating an inflammatory response to infection. Infection increases risk for thrombosis. Platelets contribute to defense from infection and to thrombosis. Experiments were designed to determine whether LPS, through TLR4 signaling, affects platelet phenotype. Platelet responses in wild-type (WT) mice and mice that lack the TLR4 gene (dTLR4) were compared following a single nonlethal injection of LPS (0.2 mg/kg iv). Compared with WT mice, mice without TLR4 had fewer circulating platelets with lower RNA content and were less responsive to thrombin-activated expression of P-selectin but were equally sensitive to aggregation or ATP secretion. One week following the LPS injection, the time it takes for the circulating platelet pool to turnover, the number of circulating platelets, thrombin-induced expression of P-selectin, and collagen-activated aggregation were increased comparably in both groups of mice. Therefore, the change of the platelet pool to an activated phenotype 1 wk after a single exposure to LPS appears to arise from a process that is independent of TLR4. The persistence of the effect 1 wk after the injection suggests that the changes reflect an action of LPS on megakaryocytes and their platelet progeny rather than on circulating platelets, which would have been cleared.     

Citrate synthase expression and enzyme activity after endurance training in cardiac and skeletal muscles.

The present study was designed to examine the acute and chronic effects of endurance treadmill training on citrate synthase (CS) gene expression and enzymatic activity in rat skeletal and cardiac muscles. Adult rats were endurance trained for 8 wk on a treadmill. They were killed 1 h (T(1), n = 8) or 48 h (T(48), n = 8) after their last bout of exercise training. Eight rats were sedentary controls (C) during the training period. CS mRNA levels and enzymatic activities of the soleus and ventricle muscles were determined. Training resulted in higher CS mRNA levels in both the soleus muscles (21% increase in T(1); 18% increase in T(48), P < 0.05) and ventricle muscles (23% increase in T(1); 17% increase in T(48), P < 0.05) when compared with the C group. The CS enzyme activities were 42 (P < 0.01) and 25% (P < 0.01) greater in the soleus muscles of T(1) and T(48) groups, respectively, when compared with that of the C group. Soleus CS enzyme activity was significantly greater in the T(1) vs. T(48) groups (P < 0.05). However, no appreciable alterations in CS enzyme activities were observed in the ventricle muscles in both training groups. These findings suggest differential responses of skeletal and cardiac muscles in CS enzymatic activity but similar responses in CS gene expression at 1 and 48 h after the last session of endurance training. Moreover, our data support the existence of an acute effect of exercise on the training-induced elevation in CS activity in rat soleus but not ventricle muscles.     

Social correlates of stress in adult males of the great gerbil,Rhombomys opimus,in years of high and low population densities

The great gerbil, Rhombomys opimus, is the most social species in the Gerbillinae. The social structure consists of family groups that occupy isolated systems of burrows consisting of one breeding male, from one to seven females, and juveniles. During a year of peak density and one of density decline, we studied the influence of group size, group composition, local density, and distance to the nearest groups on fecal corticosterone and testosterone concentrations in breeding males. We also examined the relationship of hormone concentrations to the survival of males during the summer drought between the spring and the fall. We found that males differed in concentrations of steroid hormones. Concentrations of testosterone were lower whereas those of corticosterone tended to be higher in a year of high population densities compared with higher testosterone and lower corticosterone in a year with a lower density. This finding suggests that stress may be greater in higher densities because of increased social contact. Stepwise regression analysis revealed a positive and significant influence of the number of adult females in a family group on concentrations of fecal corticosterone and testosterone in adult males. Concentrations of corticosterone were also significantly higher in males that disappeared from family groups between the spring and the fall compared with males still alive in family groups in the fall. There was no change in concentrations of testosterone. These results suggest that social interactions within large family groups may be an important source of stress for adult males.     

Evolutionary relationships in the Asteraceae tribe Inuleae (incl. Plucheeae) evidenced by DNA sequences of ndhF; with notes on the systematic positions of some aberrant genera

The phylogenetic relationships between the tribes Inuleae sensu stricto and Plucheeae are investigated by analysis of sequence data from the cpDNA gene ndhF. The delimitation between the two tribes is elucidated, and the systematic positions of a number of genera associated with these groups, i.e. genera with either aberrant morphological characters or a debated systematic position, are clarified. Together, the Inuleae and Plucheeae form a monophyletic group in which the majority of genera of Inuleae s.str. form one clade, and all the taxa from the Plucheeae together with the genera Antiphiona, Calostephane, Geigeria, Ondetia, Pechuel-loeschea, Pegolettia, and Iphionopsis from Inuleae s.str. form another. Members of the Plucheeae are nested with genera of the Inuleae s.str., and support for the Plucheeae clade is weak. Consequently, the latter cannot be maintained and the two groups are treated as one tribe, Inuleae, with the two subtribes Inulinae and Plucheinae. The genera Asteriscus, Chrysophthalmum, Inula, Laggera, Pentanema, Pluchea, and Pulicaria are demonstrated to be non-monophyletic. Cratystylis and Iphionopsis are found to belong to the same clade as the taxa of the former Plucheeae. Caesulia is shown to be a close relative of Duhaldea and Blumea of the Inuleae-Inulinae. The genera Callilepis and Zoutpansbergia belong to the major clade of the family that includes the tribes Heliantheae sensu lato and Inuleae (incl. Plucheeae), but their exact position remains unresolved. The genus Gymnarrhena is not part of the Inuleae, but is either part of the unresolved basal complex of the paraphyletic Cichorioideae, or sister to the entire Asteroideae.     

Social environment and morpho-physiological status of young males in the fall groups of great gerbil (Rhombomys opimus Licht). Effect of adults' presence

The dependence of stress and sex hormone levels, size of mid-ventral skin gland, and body mass of young males on the presence in social groups of adult gerbils (>1 year old) were studied during the fall of 1999 in the non-breeding high density population of the great gerbil (Rhombomys opimus Licht; Bukhara region, Uzbekistan). Contents of corticosterone and testosterone in fecal samples collected from young males in the field were analyzed by non-invasive radioimmunoassay. The fall gerbil groups with adults were of larger size than those without adults. The total number of individuals in a group is positively correlated with concentration of corticosterone in feces of young males. Presence of adult male and especially of adult female suppresses maturation of juvenile males indicated by size of the androgene-dependent mid-ventral gland, but accelerates their total growth. Thus, the social environment influences morpho-physiological characters of young males, effecting rate of their maturation directly or indirectly through the density dependent stress.     

Mutation of the cyclin-dependent kinase phosphorylation site in simian virus 40 (SV40) large T antigen specifically blocks SV40 origin DNA unwinding.

A mutant simian virus 40 (SV40) large tumor (T) antigen bearing alanine instead of threonine at residue 124 (T124A) failed to replicate SV40 DNA in infected monkey cells (J. Schneider and E. Fanning, J. Virol. 62:1598-1605, 1988). We investigated the biochemical properties of T124A T antigen in greater detail by using purified protein from a baculovirus expression system. Purified T124A is defective in SV40 DNA replication in vitro, but does bind specifically to the viral origin under the conditions normally used for DNA replication. The mutant protein forms double-hexamer complexes at the origin in an ATP-dependent fashion, although the binding reaction requires somewhat higher protein concentrations than the wild-type protein. Binding of T124A protein results in local distortion of the origin DNA similar to that observed with the wild-type protein. These findings indicate that the replication defect of T124A protein is not due to failure to recognize and occupy the origin. Under some conditions T124A is capable of unwinding short origin DNA fragments. However, the mutant protein is almost completely defective in unwinding of circular plasmid DNA molecules containing the SV40 origin. Since the helicase activity of T124A is essentially identical to that of the wild-type protein, we conclude that the mutant is defective in the initial opening of the duplex at the origin, possibly as a result of altered hexamer-hexamer interactions. The phenotype of T124A suggests a possible role for phosphorylation of threonine 124 by cyclin-dependent kinases in controlling the origin unwinding activity of T antigen in infected cells.     

Endemic infection reduces transmission potential of an epidemic parasite during co-infection

Endemic, low-virulence parasitic infections are common in nature. Such infections may deplete host resources, which in turn could affect the reproduction of other parasites during co-infection. We aimed to determine whether the reproduction, and therefore transmission potential, of an epidemic parasite was limited by energy costs imposed on the host by an endemic infection. Total lipids, triacylglycerols (TAG) and polar lipids were measured in cockroaches (Blattella germanica) that were fed ad libitum, starved or infected with an endemic parasite, Gregarina blattarum. Reproductive output of an epidemic parasite, Steinernema carpocapsae, was then assessed by counting the number of infective stages emerging from these three host groups. We found both starvation and gregarine infection reduced cockroach lipids, mainly through depletion of TAG. Further, both starvation and G. blattarum infection resulted in reduced emergence of nematode transmission stages. This is, to our knowledge, the first study to demonstrate directly that host resource depletion caused by endemic infection could affect epidemic disease transmission. In view of the ubiquity of endemic infections in nature, future studies of epidemic transmission should take greater account of endemic co-infections.