Targeted disruption of mammalian hairy and Enhancer of split homolog-1 (HES-1) leads to up-regulation of neural helix-loop-helix factors, premature neurogenesis, and severe neural tube defects

Mammalian hairy and Enhancer of split homolog-1 (HES-1) encodes a helix-loop-helix (HLH) factor that is thought to act as a negative regulator of neurogenesis. To directly investigate the functions of HES-1 in mammalian embryogenesis, we performed a targeted disruption of the HES-1 locus. Mice homozygous for the mutation exhibited severe neurulation defects and died during gestation or just after birth. In the developing brain of HES-1-null embryos, expression of the neural differentiation factor Mash-1 and other neural HLH factors was up-regulated and postmitotic neurons appeared prematurely. These results suggest that HES-1 normally controls the proper timing of neurogenesis and regulates neural tube morphogenesis.     

Microdialysis calibration using retrodialysis and zero-net flux: application to a study of the distribution of zidovudine to rabbit cerebrospinal fluid and thalamus

A retrodialysis (RD) method for the real-time calibration of on-line microdialysis (MD) procedures was investigated in vitro and in vivo. Calibration by retrodialysis was simultaneously validated through the use of a zero-net flux (ZNF) method, which assumes directional independence of diffusion of the solute. In RD, a calibrator with dialysance (PeA; effective permeability-surface area product) similar to that of the compound of interest is introduced into the perfusate. If the calibrator is suitable, its loss from the perfusate during RD is identical to the recovery of the solute of interest determined simultaneously by normal MD. Two antiviral nucleosides (AZT and AZdU) which differ structurally by only a methylene group were utilized as solute and calibrator, respectively. Both nucleosides exhibited similar recovery and loss at flow rates of 0.5 to 5 microL/min in vitro, indicating a similar PeA product in this flow domain. Furthermore, both compounds showed similar loss into the lateral ventricle or thalamus of rabbits (n = 4) during RD at a flow rate of 1 microL/min for 6 hr. The relative loss decreased rapidly within the first hour, reaching a relatively stable value after 2 hr. The significant reduction in the loss of AZdU and AZT in vivo compared with that in vitro likely results from a lower diffusion coefficient in tissue. The distribution of AZT between plasma and cerebrospinal fluid (CSF) in the ventricle and extracellular fluid (ECF) in thalamus was determined at steady state using calibration by RD and ZNF simultaneously.(ABSTRACT TRUNCATED AT 250 WORDS)     

Factors affecting circulating growth hormone binding protein in chickens

Growth hormone binding protein (GHBP) may be an important factor in the regulation of growth and might provide an indirect, relatively noninvasive means of predicting the status of hepatic growth hormone receptor (GHR) activity. Several factors have been reported to influence growth hormone (GH), GHR, or GHBP. Therefore, these studies were conducted to test how age, sex, nutritional status, and glucocorticoids (cortisone acetate, CA) influence serum concentrations of chicken GHBP. Serum GHBP activity was highest (mean percentage specific binding (%SB) = 12.43 +/- .80) at hatch and decreased linearly (P < .0001) to 5 wk of age (%SB = 1.99 +/- 1.13). There were no sex-related differences in serum GHBP activity from hatch to 5 wk of age (P > .08). Short-term nutrient deprivation (24-h) of 4-wk-old broilers also had a significant effect on serum GHBP activity (P < .0001). Measurement of serum GHBP activity with refeeding (after a 24-h period without feed) restored %SB to normal values. Feeding broilers a low-protein diet (12% CP) did not significantly affect serum GHBP activity when compared with that of broilers fed a commercial broiler diet (23% CP; P > .30). Administration of cortisone (1, 5, and 10 mg/day), every 24 h for 7 days, had no effect, at any dose, on serum GHBP activity at 48 h and 1 wk after the last injection. These results indicate that serum GHBP activity is influenced by factors such as age and feed deprivation. It remains to be determined whether these changes in GHBP are associated with changes in GHR as reported for mammalian species.     

Sputum and serum pharmacokinetics of loracarbef (LY163892) in patients with chronic bronchial sepsis

BACKGROUND: Carbon dioxide absorption into the blood during laparoscopic surgery using intraperitoneal carbon dioxide insufflation may lead to respiratory acidosis, increased ventilation requirements, and possible serious cardiovascular compromise. The relationship between increased carbon dioxide excretion (VCO2) and intraperitoneal carbon dioxide insufflation pressure has not been well defined. METHODS: In 12 anesthesized pigs instrumented for laparoscopic surgery, intraperitoneal carbon dioxide (n = 6) or helium (n = 6) insufflation pressure was increased in steps, and VCO2 (metabolic cart), dead space, and hemodynamics were measured during constant minute ventilation. RESULTS: VCO2 increases rapidly as intraperitoneal insufflation pressure increases from 0 to 10 mmHg; but from 10 to 25 mmHg, VCO2 does not increase much further. PaCO2 increases continuously as intraperitoneal insufflation pressure increases from 0 to 25 mmHg. Hemodynamic parameters remained stable. CONCLUSIONS: By considering Fick's law of diffusion, the initial increase in VCO2 is likely accounted for by increasing peritoneal surface area exposed during insufflation. The continued increase in PaCO2 without a corresponding increase in VCO2 is accounted for by increasing respiratory dead space.     

P2X purinoceptors in postmortem human cerebral arteries

Pharmacological studies have demonstrated that various purinoceptors are involved in the control of the cerebral vascular tone in many species. In this study, the existence of P2X purinoceptors in the postmortem human cerebral arteries was investigated with organ-bath pharmacology, autoradiography, and immunohistochemistry. Specimens were obtained from the M2 region of the middle cerebral arteries from human cadavers with an age range of 53-91 years and postmortem time of 37-54 h. Application of alpha,beta-methylene adenosine triphosphate (ATP) produced concentration-dependent contraction in the arterial ring, whereas transmural nerve stimulation and noradrenaline did not elicit contraction. Autoradiography using [3H]alpha,beta-methylene ATP (a radioligand for P2X purinoceptors) showed specific [3H]alpha,beta-methylene ATP binding sites in the smooth-muscle cells of the postmortem human cerebral arteries. Immunohistochemistry with specific P2X1 purinoceptor antibodies revealed positive staining exclusively in the smooth muscle of the same specimens. All these results demonstrate the existence of P2X purinoceptors in human cerebral arteries, which were still functionally active despite the long postmortem time. The results from this study suggest that the postmortem human cerebral arteries can be useful specimens for studying the P2X purinoceptor-mediated responses.     

Combination therapy with suicide and cytokine genes for hepatic metastases of lung cancer

Metastases of lung cancer are a major cause of treatment failure. To evaluate the therapeutic efficacy of gene therapy in metastatic lung cancer, we used adenoviral (ADV) mediated transfer of the herpes simplex virus thymidine kinase (HSV-tk) gene and the cytokine gene interleukin-2 (IL-2) to treat a murine model of metastatic lung cancer in the liver. Hepatic metastases were established by intrahepatic implantation of LL2 cells in syngeneic recipient mice. One week after tumor implantation, various replication defective ADV vectors were injected intratumorally. Treatment with a vector expressing the HSV-tk followed by ganciclovir administration with ADV.tk resulted in significant regression of tumor (p<0.01) as well as prolongation of survival (p<0.001). While a vector expressing mouse IL-2 ADV.IL-2 alone was ineffective, combination therapy with HSV-tk resulted in further tumor regression and improvement of animal survival (p<0.05). These results demonstrate that suicide and cytokine genes can be utilized in combination to treat metastatic lung cancer in vivo.