Effects of temperature and physical activity on blood flow shunts and intracardiac mixing in the toad Bufo marinus.

Blood flow in systemic (.Qsys) and pulmocutaneous (.Qpul) arteries was measured as a function of body temperature (10 degrees, 20 degrees, and 30 degrees C) at rest and following enforced physical activity in conscious, adult cane toads (Bufo marinus). Arterial and mixed venous hemoglobin concentration (CHb) and total oxygen content (Co2, tot) were measured in a separate group under identical conditions. Heart rate (fH) and total flow (.Qtot) increased significantly (P<0.001) with elevated temperature and with activity, whereas stroke volume (VS) increased (P<0.001) only with activity. .Qtot ranged about 10-fold, from 10 degrees C (rest) to 30 degrees C (activity); increases in both fH and VS contributed to the increase in .Qtot. The overall distribution of blood to the pulmocutaneous circuit (net L-R shunt) increased with both temperature and activity and was significantly correlated with .Qtot. These data indicate that blood flow distribution in toads is a direct function of cardiac output, and this is linked to relative changes in resistance in the major outflow vessels. Arterial O2 saturation (Sa) was high (mean=93%) in all conditions except activity at 30 degrees C, when it decreased to 74% and contributed to a decrease in the arteriovenous O2 difference. Venous O2 saturation (Sv) was high at rest (76%) and dropped significantly during activity to about 30% at all temperatures. Intracardiac arterial-venous mixing (systemic mixing index) showed the strongest correlation with variation in fH with minimal mixing (17%) occurring at about 50 beats min-1. The most mixing occurred at the lowest fH (13 beats min-1) and at the highest fH (103 beats min-1). The results indicate that the heart of a 0.25-kg toad becomes more efficient from an oxygen transport perspective from low fH to 50 beats min-1 and then less efficient at higher fH, contributing to an uncoupling of blood flow and metabolic rates at these high rates.     

The effect of ciliate protozoa on the turnover of bacterial and fungal protien in the rumen of sheep

A four-fold increase (P < 0.001) in the total bacterial population in the rumen of sheep was observed following defaunation. A two-fold (P > 0.05) increase in the anacrobic fungal population was also observed. Defaunation caused a 10-fold (P < 0.001) reduction in the rate of protein turnover of Selenomonas rurninantium protein in vitro . However, only a two-fold reduction (P < 0.05) was observed in the rate of protein turnover of the rumen fungi Piromonas communis, Neocallimastix patriciarum and N. frontalis. It was concluded that although protozoa may play an important role in the turnover of fungal protein in the rumen, they have a greater role in the turnover of bacterial protein.     

Perfusion‐based fluorescence imaging method delineates diverse organs and identifies multifocal tumors using generic near‐infrared molecular probes

Rapid detection of multifocal cancer without the use of complex imaging schemes will improve treatment outcomes. In this study, dynamic fluorescence imaging was used to harness differences in the perfusion kinetics of near‐infrared (NIR) fluorescent dyes to visualize structural characteristics of different tissues. Using the hydrophobic nontumor‐selective NIR dye cypate, and the hydrophilic dye LS288, a high tumor‐to‐background contrast was achieved, allowing the delineation of diverse tissue types while maintaining short imaging times. By clustering tissue types with similar perfusion properties, the dynamic fluorescence imaging method identified secondary tumor locations when only the primary tumor position was known, with a respective sensitivity and specificity of 0.97 and 0.75 for cypate, and 0.85 and 0.81 for LS288. Histological analysis suggests that the vasculature in the connective tissue that directly surrounds the tumor was a major factor for tumor identification through perfusion imaging. Although the hydrophobic dye showed higher specificity than the hydrophilic probe, use of other dyes with different physical and biological properties could further improve the accuracy of the dynamic imaging platform to identify multifocal tumors for potential use in real‐time intraoperative procedures.      

Covalent structure of mutacin 1140 and a novel method for the rapid identification of lantibiotics.

The primary structure of the Streptococcus mutans lantibiotic mutacin 1140 was elucidated by NMR spectroscopy, mass spectrometry, and chemical sequencing. The structure is in agreement with other closely related lantibiotics, such as epidermin. A novel method was developed in which mutacin 1140 was chemically modified with sodium borohydride followed by ethanethiol, allowing the differentiation of the thioether-containing residues from the dehydrated residues. This double-labeling strategy provides a simple method to reliably identify all modified lantibiotic residues with a minimal amount of material. While NMR spectroscopy is still required to obtain thioether bridging patterns and thus the complete covalent structure, the double-labeling technique, along with mass spectrometry, provides most of the information in a fraction of the time required for a complete NMR analysis. Thus, with these new techniques lantibiotics can be rapidly characterized.     

On the use of morphactin and triiodobenzoic acid in apical dominance studies

Summary Application of either CFM or TIBA to bean plants caused four main effects: (i) inhibition of main shoot and leaf growth; (ii) abscission of young leaflets and internodes; (iii) limited outgrowth of lateral buds below the point of application of the substances followed by abscission of these buds; (iv) abscission of all other lateral buds. Although the chemical pruning effects of CFM and TIBA may be the result of their action in blocking auxin transport, the use of these substances for analysing auxin effects in apical dominance is questionable.     

Localization and identification of auxin in roots of Zea mays

Summary Roots of 3.5-day-old seedlings of Zea mays cv. Giant White Horsetooth contain an extractable auxin which has chromatographic properties and reactions to chromogenic sprays identical with those of indole-3-acetic acid (IAA). By separating stele from cortex (and root tips) before extraction it was shown that the auxin is localized predominantly in the stele, with little being found in the cortex. Whole roots, isolated cortices and isolated steles accumulate and metabolize exogenously applied IAA-1-¹⁴C. The stelar tissue is distinguished from whole roots and cortical tissue in having a different pattern of IAA metabolism.     

Identification and localisation of auxin in primary roots of Zea mays by mass spectrometry

Summary Roots of 3.5-day-old seedlings of Zea mays L. var. Giant White Horsetooth contain an extractable auxin which has been identified unequivocally as IAA. A mass spectrometric technique has been used to determine quantitatively the levels of IAA in the cortical, stelar and apical regions of the roots. The IAA is predominantly located in the steles.