Quantification of perfusion fMRI using a numerical model of arterial spin labeling that accounts for dynamic transit time effects.

A new approach to modeling the signal observed in arterial spin labeling (ASL) experiments during changing perfusion conditions is presented in this article. The new model uses numerical methods to extend first-order kinetic principles to include the changes in arrival time of the arterial tag that occur during neuronal activation. Estimation of the perfusion function from the ASL signal using this model is also demonstrated. The estimation algorithm uses a roughness penalty as well as prior information. The approach is demonstrated in numerical simulations and human experiments. The approach presented here is particularly suitable for fast ASL acquisition schemes, such as turbo continuous ASL (Turbo-CASL), which allows subtraction pairs to be acquired in less than 3 s but is sensitive to arrival time changes. This modeling approach can also be extended to other acquisition schemes.     

Effects of chelating agents on the rheological property of cervical mucus

As an ongoing effort to elucidate the mechanisms involved in the calcium-dependent fertility regulation process, the viscoelastic properties of the mucus obtained from lamb cervix and human semen, as well as their water and total protein contents after exposure to EDTA, a chelating agent, or Nonoxynol-9 (N-9), a spermicidal agent, were examined. The viscosity was measured using a Cone Plate Digital Viscometer, while the water and total protein contents were determined by the lyophilization process and the Lowry method, respectively. The significant changes in the rheological properties of mucus, such as its viscosity and the water content, upon exposure to EDTA were demonstrated. The viscosity of cervical mucus and human semen were significantly increased by EDTA treatment (as compared to the controls): lamb cervical mucus (2.9 ± 0.3 vs. 2.2 ± 0.3 cps) and human semen (5.0 ± 0.3 vs. 4.3 ± 0.3 cps), respectively. The hydration rate was decreased by EDTA treatment as compared with the control (93.6 ± 0.7 vs. 96.8 ± 0.8%). Among tested samples, the reduction in the percentage of sperm penetration through the cervical mucus was the highest in the mucus containing EDTA, which had the lowest water content (93.6 ± 0.7%), indicating that there is a positive relationship between the hydration rate of the cervical mucus and its ability to permit the penetration of spermatozoa. This result indicates that spermicidal activity exerted by high concentrations of EDTA is in part due to its effect on the rheological properties of cervical mucus or semen.     

SOME ANATOMICAL DATA RELATED TO THE TRANSNASO- SPHENOIDAL RESECTION OF PITUITARY FOSSA TUMORS

Since the beginning of this century, trans- naso-sphenoidal resection of the pituitary fossa tumors has been widely used clinically. It has more merits than other operative approaches used before. In China it has been adopted by both ENT doctors and neurosurgeons since 1959.1 In order to afford some relevant anatomical data, we measured 137 adult sagittal plane skulls with distinct landmarks.     

An intracellular self protein synthesized in macrophages is presented but fails to induce tolerance

Mice deficient for the fifth component of murine complement (C5), unlike normal mice, do not possess the secreted form of C5 in their body fluids and can be readily immunized to serum-derived normal C5. Although macrophages from C5-deficient mice do not secrete C5, they synthesize the precursor form (pro-C5). Therefore contact of T cells with autologous pro-C5 presented by macrophages is theoretically possible. We show that macrophages from C5-deficient mice can indeed stimulate a class II restricted C5-specific T cell clone without addition of exogenous C5. Immunization of C5-deficient mice with autologous pro-C5 induces vigorous C5-specific T cell proliferation and pro-C5 is recognized by C5-specific T cells in vitro, demonstrating that this protein fails to induce tolerance under physiological conditions. Thus, intracellular pro-C5 is processed and presented by C5-deficient macrophages and can activate T cell clones in vitro, yet is neither immunogenic nor tolerogenic for T cells in vivo.     

Sleep apnea--an overview

Though distressing and potentially dangerous, sleep apnea may be an under-recognized disease in many countries. The obstructive type, which usually presents with loud snoring and excessive daytime sleepiness, is by far the commonest form. It causes a great deal of medical, social and psychological morbidity as well as an increased mortality. Doctors of different specialties have an important role in detecting and referring suspected patients for early assessment and treatment. Multidisciplinary management in a general hospital and accurate assessment with polysomnography are essential as modern and sometimes effective methods of treatment are becoming available.