Method to perform IV injections on mice using the facial vein.

A novel technique for gaining IV access in a mouse model is presented. Using a cut-down approach, the facial vein is identified through an incision from anterior to the external auditory meatus to posterior to the lateral ispilateral canthus. A small gage needle (30gauge) may be inserted to inject medications. A high success rate (93%) as determined by direct visualization is achieved. The technique would prove especially useful for animals slated for kinematic testing as the incision does not interfere with the animal's ventral surface.

Prediction of rho-independent transcriptional terminators in Escherichia coli.

A new algorithm called RNAMotif containing RNA structure and sequence constraints and a thermodynamic scoring system was used to search for intrinsic rho-independent terminators in the Escherichia coli K-12 genome. We identified all 135 reported terminators and 940 putative terminator sequences beginning no more than 60 nt away from the 3'-end of the annotated transcription units (TU). Putative and reported terminators with the scores above our chosen threshold were found for 37 of the 53 non-coding RNA TU and for almost 50% of the 2592 annotated protein-encoding TU, which correlates well with the number of TU expected to contain rho-independent terminators. We also identified 439 terminators that could function in a bi-directional fashion, servicing one gene on the positive strand and a different gene on the negative strand. Approximately 700 additional termination signals in non-coding regions (NCR) far away from the nearest annotated gene were predicted. This number correlates well with the excess number of predicted 'orphan' promoters in the NCR, and these promoters and terminators may be associated with as yet unidentified TU. The significant number of high scoring hits that occurred within the reading frame of annotated genes suggests that either an additional component of rho-independent terminators exists or that a suppressive mechanism to prevent unwanted termination remains to be discovered.

Some considerations on the measurements of mean frequency shift and integrated backscatter following administration of Albunex.

Ultrasonic contrast agents have been of heightened interest in recent years. More success has been achieved by agents consisting of micro bubbles, since only a few of these agents are capable of producing very strong ultrasonic backscattered signals for the enhancement of certain tissue structures. Recent investigations also demonstrate that an analysis of the radio frequency (RF) backscattered echoes by the contrast agents may lead to quantitative means for assessing tissue perfusion. In these studies, a parameter, mean frequency shift (MFS) of the RF signal, along with integrated backscatter (IB) has received the most attention. In an effort to better understand the physical mechanisms responsible for the observed mean frequency shift, we have performed experiments on 10 dogs following injections of Albunex (Molecular Biosystems, Inc.) into the left atrium, coronary artery and abdominal aorta, respectively, for investigations in the heart and kidney. The integrated backscatter and mean frequency (MF) of a region of interest (ROI) were calculated from the RF signal acquired with a modified real-time ultrasonic scanner. The results show consistently that the RF signals acquired from all regions of interest are greatly affected by the presence of the contrast agent in the path between the transducer and the ROI, which can cause either an upward or a downward shift of the MF. This could not be observed by video densitometry or a measurement of the IB alone. The MFS is the result of the resonant behavior of the micro bubbles, which is related to the frequency, ambient pressure, and physical properties of the bubbles including size distribution, surface tension and concentration. On the other hand, when there is no contrast agent present in the path, a downward frequency shift is seen.

Quantitative measurements of second harmonic Doppler using ultrasound contrast agents.

Quantitative measurements of second harmonic and first harmonic Doppler were carried out using two ultrasound contrast agents, Albunex and FS069. The RMS amplitudes of the Doppler shift spectra were measured as a function of the concentration of the agents, frequency and transmitted acoustic pressure. The results showed that, for a given lot of contrast agent investigated, FS069 was able to produce higher levels of first and, especially, second harmonic signals compared to Albunex. Under the same experimental conditions, the RMS Doppler amplitude (RDA) of FS069 was 3.8 +/- 0.8 dB higher than Albunex at first harmonic and 12.6 +/- 0.8 dB higher at second harmonic. The ratio of the second harmonic to first harmonic RDA, which we called R2/R1, decreases at a rate of 7 dB/MHz for both agents with increasing frequency. The difference in the value of R2/R1 between FS069 and Albunex at any frequency was approximately 4.5 dB. R2/R1 was found to increase linearly as a function of the transmitted acoustic pressure for both agents. Simulations using the Rayleigh-Plesset equation show a decrease of R2/R1 at a rate of 5 dB/MHz. Comparison of experimental results with theory indicates that the shell elasticity parameter may be an increasing function of the mean diameter of the bubbles.

Hepatic insulin and glucagon receptors in pregnancy: their role in the enhanced catabolism during fasting.

The response to dietary deprivation in late pregnancy, as compared to the non-pregnant condition, is more rapid and profound in terms of mobilization of fuels frm peripheral tissues as well as hepatic ketogenesis and gluconeogenesis ("accelerated starvation"). We examined the potential role of hepatic insulin and glucagon receptors in mediating these changes by comparing 48-h fasted 18-day pregnant and age-matched nongravid rats. Molar ratios for insulin:glucagon in peripheral and portal blood were significantly higher in the pregnant rats. Insulin binding to purified liver plasma membrane receptors, when appropriately corrected for differences in insulin degradation by the membrane system, was marginally diminished in the pregnant animals. Glucagon binding and adenylate cyclase activation by glucagon was indistinguishable in the two groups of animals. On the basis of portal vein hormone concentrations and the values for receptor binding, liver insulinization relative to glucagonization appears to be unchanged or slightly increased in the fasted pregnant rat compared to the fasted nongravid rat. Thus, it seems unlikely that much of the "accelerated starvation" response in late pregnancy can be ascribed to diminished insulin and/or increased glucagon availability at the hepatocellular level. Instead, it is hypothesized that postreceptor events play the major role in sustaining the intrahepatic realignments of established fasting in late pregnancy.