M(2) and M(4) muscarinic receptor subtypes couple to activation of endothelial nitric oxide synthase.

In this report we studied coupling of M(2) and M(4) muscarinic acetylcholine receptors to activation of endothelial nitric oxide synthase (eNOS). Chinese hamster ovary cells that co-express the individual receptor subtypes and eNOS in a stable fashion were used as a model. Activation of eNOS was assayed by measuring increasing levels of cyclic GMP in admixed cells that contain guanylate cyclase. Activation of both M(2) or M(4) muscarinic receptors resulted in marked activation of eNOS, in a time- and concentration-dependent manner. The time course of the response exhibited a transient peak, followed by a sustained lower plateau. While the sustained phase was dependent on influx of extracellular calcium, the transient response showed dependency on both mobilization of intracellular calcium and extracellular influx.

Mass attenuation coefficients of clear-Pb for photons from 125I, 103Pd, 99mTc, 192Ir, 137Cs and 60Co.

The mass attenuation coefficients, mu/rho, for Clear-Pb for photon energies ranging from 10 keV to 10 MeV were determined using Monte Carlo methods and simple equations used to manipulate elemental mass attenuation coefficients. It was determined that the effectiveness of Clear-Pb as a radiation shielding material was greater than plain acrylic for all photon energies, especially those less than 150 keV, and for deep penetration problems where the differences in mu/rho between Clear-Pb and acrylic became more significant. Finally, the usefulness of Clear-Pb as a shielding material when compared with acrylic was determined for the following commonly used radionuclides: 125I, 103Pd, 99mTc, 192Ir, 137Cs, and 60Co.

A comparison of the use of tympanic, axillary, and rectal thermometers in infants.

This study examined the relationship between three instruments used in measuring tympanic, axillary, and rectal temperatures in infants less than 1 year of age. Temperatures were measured by Oto-temp Pedi Q tympanic thermometers, Becton Dickinson axillary thermometer, and rectal thermometers. A convenience sample of 5 infants less than 90 day and 54 greater than 90 days with fever, as well as 34 infants less than 90 days and 27 infants greater than 90 days without fever were studied. Correlations of infants less than 90 days and greater 90 days of age, as well as differences between infant temperature with and without fevers as variables, were examined. Results indicated a strong statistical relationship between Oto-Temp Pedi Q, Becton Dickinson axillary temperatures, and rectal temperatures, but not strong enough to base critical clinical decisions. Age and presence or absence of fever significantly affected the relationships between thermometers.

Calculated dosimetric parameters of the IoGold 125I source model 3631-A.

Basic dosimetric parameters as recommended by the AAPM Task Group No. 43 (TG-43) have been determined for recently available IoGold 125I brachytherapy seeds. Monte Carlo methods (MCNP) were used in the calculation of these parameters in water, and results compared with soon to be published experimental parameters also for 125I IoGold seeds as well with parameters for model 6702 and 6711 125I seeds. These parameters were the radial dose function, anisotropy factor and constant, and the dose rate constant. Using MCNP, values for the radial dose function at 0.5, 2.0, and 5.0 cm were 1.053, 0.877, and 0.443, respectively. The anisotropy factor was 0.975, 0.946, 0.945, and 0.952 at 0.5, 1.0, 2.0, and 5.0 cm, respectively, with an anisotropy constant of 0.95. The IoGold dose rate constant was determined by excluding the low energy titanium characteristic x rays produced in the IoGold titanium capsule. Using this post TG-43 revised NIST air kerma methodology, the IoGold dose rate constant was 0.96 cGy h-1 U-1. These calculatively determined parameters for IoGold seeds were compared with those determined experimentally for IoGold seeds, and also compared with parameters determined for model 6702 and 6711 seeds as presented in TG-43.

Ganglion cells influence the fate of dividing retinal cells in culture.

The different retinal cell types arise during vertebrate development from a common pool of progenitor cells. The mechanisms responsible for determining the fate of individual retinal cells are, as yet, poorly understood. Ganglion cells are one of the first cell types to be produced in the developing vertebrate retina and few ganglion cells are produced late in development. It is possible that, as the retina matures, the cellular environment changes such that it is not conducive to ganglion cell determination. The present study showed that older retinal cells secrete a factor that inhibits the production of ganglion cells. This was shown by culturing younger retinal cells, the test population, adjacent to various ages of older retinal cells. Increasingly older retinal cells, up to embryonic day 9, were more effective at inhibiting production of ganglion cells in the test cell population. Ganglion cell production was restored when ganglion cells were depleted from the older cell population. This suggests that ganglion cells secrete a factor that actively prevents cells from choosing the ganglion cell fate. This factor appeared to be active in medium conditioned by older retinal cells. Analysis of the conditioned medium established that the factor was heat stable and was present in the <3 kDa and >10 kDa fractions. Previous work showed that the neurogenic protein, Notch, might also be active in blocking production of ganglion cells. The present study showed that decreasing Notch expression with an antisense oligonucleotide increased the number of ganglion cells produced in a population of young retinal cells. Ganglion cell production, however, was still inhibited in cultures using antisense oligonucleotide to Notch in medium conditioned by older retinal cells. This suggests that the factor secreted by older retinal cells inhibits ganglion cell production through a different pathway than that mediated by Notch.

Large discrepancies between calculated Dmax and diode readings for small field sizes and small SSDs of 15 MV photon beams.

Clinical observations have revealed that diode readings from 15 MV photon beams with small field sizes and small SSD values were consistently 5%-10% higher than doses calculated at the maximum depth. Dose at depth depends on the collimator scattering factor and the phantom scattering factor--both field size dependent. Diodes are placed on the skin surface, and therefore the phantom scatter factor is different than at depth. In addition, inverse square corrections should be calculated with respect to the location of the diode itself rather than the location of Dmax within the tissue. This may account for about 8% difference between calculated Dmax and diode readings for very small radiation fields and small SSDs, e.g., a prostate boost.

Levels of p21(WAF1/CIP1) do not affect radiation-induced cell death in human breast epithelial cells.

Loss of the wild-type p53 activity and/or overexpression of the proto-oncogene bcl-2 are frequently detected in breast cancer and suggested to be related to chemotherapy and radiation therapy resistance. To identify the downstream signaling molecules for anti-proliferative and apoptotic activities of p53 and to investigate the interaction of bcl-2 with p53 in human breast epithelial cells, we have used the MCF10A cell line. We previously showed that overexpression of bcl-2 downregulates expression of p21(WAF1/CIP1) (a cyclin dependent kinase inhibitor which mediates p53 dependent G(1) arrest) and suppresses DNA damage-induced apoptosis in MCF10A cells. In the present study, we constitutively overexpressed p21(WAF1/CIP1) in bcl-2 overexpressing MCF10A cells to determine whether downregulation of p21(WAF1/CIP1) is necessary for the anti apoptotic activity of bcl-2, and to investigate the roles of p21(WAF1/CIP1) in p53-mediated cell death upon irradiation. Overexpression of p21(WAF1/CIP1) resulted in growth inhibition, but had no effect on bcl-2 inhibition of apoptosis following irradiation. Also, overexpression of p21(WAF1/CIP1) did not affect the dose-dependent radiation-induced cell lethality as determined by a clonogenic survival assay. These results suggest that bcl-2 downregulation of p21(WAF1/CIP1) is independent of the anti-apoptotic activity of bcl-2, and that p21(WAF/CIP1) is not involved in the p53-mediated cell death pathway.

Immediate differentiation of ganglion cells following mitosis in the developing retina.

The aim of this study is to gain insight into the time during the life history of a retinal neuron that it becomes committed to a particular phenotype. At this point, it is not possible to identify the time of commitment, but the time that differentiation begins can be identified. Bromodeoxyuridine labeling coupled with immunohistochemistry with a ganglion cell-specific antibody was used to fix the time of the beginning of ganglion cell differentiation relative to the time of mitosis in the developing chick retina. It was found that ganglion cells can begin to differentiate in less than 15 min after the end of mitosis. This suggests that the retinal ganglion cell fate may be determined before or during mitosis.

Effects of season and physical condition on the gastrointestinal helminth community of white-tailed deer from the Texas Edwards Plateau.

Eighty-six adult female white-tailed deer, Odocoileus virginianus (Zimmermann), collected over a 12-mo period in the Texas Edwards Plateau, harbored six species of nematodes (Haemonchus contortus, Gongylonema pulchrum, Oesophagostomum venulosum, Ostertagia ostertagi, Cooperia sp., and Apteragia odocoilei), and two cestodes (Moniezia sp. and Taenia hydatigena). The patterns of distribution of the three common species of gastrointestinal helminths (H. contortus, O. venulosum, and G. pulchrum) were overdispersed. When analyzed for the main and interactive effects of the extrinsic and intrinsic variables of season and physical condition, respectively, aggregated abundances in H. contortus and O. venulosum appeared to result from the main effect of seasonal changes operating over the collective populations of these two species rather than from the intrinsic factor of physical condition operating within selected subpopulations. Abomasal parasite counts do not appear to be a useful index for monitoring herd condition of white-tailed deer from this geographic region.

Seasonal variations in physiological indices of adult female white-tailed deer in Texas.

Seasonal variations in blood chemistry, urine chemistry, fat reserves, and crude protein levels of rumen contents were determined for free-ranging adult female white-tailed deer (Odocoileus virginianus Zimmermann) in central Texas. Seasonal variations (P less than 0.05) existed for serum total protein, albumin, globulin, albumin/globulin ratios, blood urea nitrogen (BUN), cholesterol, alkaline phosphatase, creatinine, phosphorus, and sodium; and urinary urea/creatinine (U/C) ratios, rumen crude protein, the kidney fat index (KFI), femur marrow fat (FMF), and dressed weights. Variations in BUN, urinary U/C ratios, dressed weights, KFI, and FMF were attributed partially to the nutritional demands of late gestation and lactation.