EFFECT OF REMOVAL OF CO-OCCURRING SPECIES ON DISTRIBUTION AND ABUNDANCE OF ERYTHRONIUM AMERICANUM (LILIACEAE), A SPRING EPHEMERAL

Growth of spring ephemerals in northern forests is limited to early spring when competition for resources from other species is at a minimum. The abundance of resources during this vernal period suggests that spring ephemerals might grow continuously over a wide range of sites, but distributions tend to be patchy. I hypothesized that co-occurring plants that grow later in the season compete for resources to a limited extent, but that competition from these other species is sufficient to restrict the spread of spring ephemerals into unoccupied sites. Population dynamics of Erythronium americanum were compared on sites at the Hubbard Brook Experimental Forest in New Hampshire subjected to varying removals of cooccurring plants. During the 3-year period after removal of only overstory trees the density and frequency of occurrence of Erythronium increased by 225% and 180%, respectively, and removal of all co-occurring vegetation after 1 year's regrowth had an even more pronounced effect (400% and 195% increases, respectively). The abundance of Erythronium in the undisturbed forest did not change over the 3-year period. Elevational distribution of Erythronium also was directly related to the extent of removal of summer plants. Recruitment was mostly vegetative, but flower production on the tree removal site increased by a factor of six, and some distant sites apparently were colonized by seedlings. For several years following large-scale disturbances that eliminate co-occurring vegetation, the vernal growing season is lengthened and resources are more available, and spring ephemerals such as Erythronium americanum exploit these resource-rich opportunities to expand populations and colonize new sites. It appears that, as forest succession proceeds, the size and survival of newly established colonies are gradually constrained by competition from co-occurring species that grow later in the season.     

The effects of pentobarbital, fentanyl-droperidol, ketamine-xylazine and ketamine-diazepam on core and surface body temperature regulation in adult male rats

Many commonly used anesthetics cause hypothermia by inhibiting central and peripheral thermoregulatory mechanisms. Although it is probable that a loss of thermal homeostasis contributes directly to the high mortality frequently reported following anesthesia of laboratory rodents, this adverse effect has been investigated rarely in the past. This study compared the effects of three parenteral anesthetics (pentobarbital, ketamine-xylazine and ketamine-diazepam) and a neuroleptanalgesic (fentanyl-droperidol) on core and surface body temperature regulation in rats. Results showed a profound hypothermia with all dosages of pentobarbital, while ketamine-xylazine and ketamine-diazepam caused a dose-dependent depression in core and surface body temperature. All dosages of fentanyl-droperidol (Innovar-Vet) caused minimal depression in thermoregulation, suggesting that it is the drug which requires the least external thermal support. Results of this study also suggested that inability to compensate for heat loss, particularly from the body core, may profoundly influence anesthetic toxicity and the safety of anesthetic procedures.     

The effects of pentobarbital, fentanyl-droperidol, ketamine-xylazine and ketamine-diazepam on arterial blood pH, blood gases, mean arterial blood pressure and heart rate in adult male rats

Although anesthetics are known to cause respiratory and cardiovascular depression in humans, these adverse effects rarely have been investigated in laboratory rodents. This study evaluated the effects of four different injectable drugs, pentobarbital, fentanyl-droperidol (Innovar-Vet), ketamine-xylazine and ketamine-diazepam on the respiratory and cardiovascular systems of rats. Results showed marked acidosis, hypercarbia and hypoxia with high doses of Innovar-Vet, moderate respiratory depression with all dosages of pentobarbital and minimal respiratory depression with ketamine-xylazine and ketamine-diazepam. Innovar-Vet, ketamine-xylazine and pentobarbital caused profound hypotension, particularly at high dosages, while ketamine-diazepam caused the least depression in mean arterial blood pressure of all drugs evaluated. None of the drugs studied produced significant alterations in heart rate. Throughout all dosages investigated, the ketamine-diazepam combination showed the least overall effects on ventilation and perfusion of the four parenteral drug combinations studied.     

Seed Dormancy in Red Rice : VI. Monocarboxylic Acids: A New Class of pH-Dependent Germination Stimulants

The addition of an elicitor (glucan) to Phaseolus vulgaris cell suspension cultures increased the formation of the phytoalexin phaseollin. Intracellular pH and phosphate concentrations were studied with ³¹P nuclear magnetic resonance spectroscopy on elicitor-treated cells which were aerated during the nuclear magnetic resonance measurement. The pH of the vacuole and to a lesser extent the pH of the cytoplasm were affected at 10 minutes after elicitor addition; a decrease in pH from 5.3 to 4.8 was noted in the vacuole and from 7.46 to 7.28 in the cytoplasm. The ratio between the amount of Pi in the vacuole to that in the cytoplasm also changed within 10 minutes after elicitor addition. The signal for ATP (β-ATP) was low after elicitor addition and was high again 23 hours after elicitation. Forty-eight hours after elicitor addition, vacuolar and cytoplasmic pH had almost returned to their initial values. The rapid change in vacuolar and cytoplasmic pH may cause the change of metabolism that occurs in elicitor-treated P. vulgaris cells.     

Rec dependence of mu transposition from P22-transduced fragments.

Derivatives of bacteriophage Mu carrying a lac operon and a selectable drug resistance element (Mu d phages) are frequently used tools of bacterial genetics. Mu d prophages used in this way can be treated as transposons, in that the inserted material can be transduced from one strain to another by general transducing phages, such as P1 and P22. When a Mu d prophage is transduced into a new recipient by P1 or P22, the Mu d element can transpose from the transduced fragment into the bacterial chromosome. Transposition of the Mu d element from a P22-transduced fragment shows several striking differences from transposition of a Mu d genome injected by a Mu virion. First, the frequency of transposition from a transduced fragment is greatly enhanced by a P22 helper genome. Second, transposition requires the host recA, B, and C functions. Transposition of Mu following injection by a Mu virion is rec independent. While the basis of these observations is not understood, we suggest that the Mu X protein, a 65-kilodalton protein injected by a Mu virion and required for Mu transposition, may not be packaged by P22. We suggest that the effects seen reflect the behavior of a Mu genome in the absence of the X protein.     

High and low molecular weight rabbit secretory components. Evidence for the deletion of the second and third domains in the smaller polypeptide

Rabbit secretory components exist in two forms which differ in apparent mass by about 25 kDa. Each of these two forms were reduced, carboxymethylated, and extensively digested with trypsin. The resulting peptides were purified by reverse-phase high performance liquid chromatography and characterized by NH2- and COOH-terminal sequence determination and/or amino acid analysis. They were aligned with the protein sequence predicted from the cDNA nucleotide sequence encoding the rabbit poly(Ig) receptor (Mostov, K. E., Friedlander, M., and Blobel, G. (1984) Nature 308, 37-43). All peptides belonging to the fourth and fifth domains except one (positions 488-496) were accounted for in both forms. In addition, limited tryptic proteolysis of the native low Mr secretory components produced the intact 18-kDa NH2-terminal domain (positions 1-117) and the 30-kDa fragment encompassing the fourth and fifth domains. These results suggest that the smaller polypeptide derives from the larger secretory component form by the deletion of the second and third domains.     

Rat hepatocytes in serum-free primary culture elaborate an extensive extracellular matrix containing fibrin and fibronectin

Adult rat hepatocytes cultured on type IV collagen, fibronectin, or laminin and maintained in serum-free medium were examined by indirect immunofluorescence using polyclonal antibodies against extracellular matrix proteins. An extensive fibrillar matrix containing fibronectin and fibrin was detected in all hepatocyte cultures irrespective of the exogenous matrix substratum used to support cell adhesion. Fibrils radiated from the cell periphery and covered the entire culture substratum. In addition, thicker fibers or bundles of fibers were localized on top of hepatocytes. This matrix did not contain laminin or the major types of collagen found in the liver biomatrix (types I, III, and IV). Isolation of the fibrillar matrix and analysis on polyacrylamide gels under reducing conditions demonstrated a major 58-kD polypeptide, derived from beta-fibrinogen as indicated by immunoblotting and two-dimensional peptide mapping. Plasmin rapidly dissolved the matrix. Deposition of the fibrin matrix in hepatocyte cultures was arrested by hirudin, by specific heparin oligosaccharides that potentiate thrombin inhibition by antithrombin III, and by dermatan sulfate, an activator of heparin cofactor II-mediated inhibition of thrombin. The results indicate that hepatocytes in culture synthesize and activate coagulation zymogens. In the absence of inhibitory and fibrinolytic mechanisms, a fibrin clot is formed by the action of thrombin on fibrinogen. Fibronectin attaches to this fibrin clot but fails to elaborate a fibrillar matrix on its own in the presence of coagulation inhibitors.     

Rabbit secretory components: identification of a third allotype, t63

A third allotype of rabbit secretory component has been identified. The allotype previously referred to as t62 by our laboratory can now be subdivided into two allotypes, t62 and t63, with alloantisera capable of discriminating between the two. Results of family studies are consistent with a three allele system (t61, t62 and t63) at the t-locus. By SDS PAGE, electrophoretic mobilities of the multiple SC bands for each of the three allotypes are characteristic of the allotype; the apparent molecular sizes of the bands of the t62 allotype are 2 to 3 kDa lower than those for the t61 allotype. The banding patterns of the t61 and t63, although similar, are not identical to each other. Results of serologic cross-reaction studies and of tryptic peptide mapping studies suggest multiple structural differences between the allotypes as well as a closer relationship between t62 and t63 than between either of these allotypes and t61.