Epo-induced hemoglobinization of SKT6 cells is mediated by minimal cytoplasmic domains of the Epo or prolactin receptors without modulation of GATA-1 or EKLF

The characteristics of GABAergic inhibitory modulation of respiratory bulbospinal neuronal activity and short-term potentiation (STP) of phrenic motoneuronal activity were studied. Extracellular unit recording and picoejection techniques in anesthetized dogs showed that both the spontaneous rhythmic and reflexly induced discharge patterns of inspiratory (I) and expiratory (E) premotor neurons were proportionately amplified by the localized application of picomole amounts of bicuculline (Bic), a competitive GABAA antagonist. Intracellular recording and paired-pulse stimulation techniques in anesthetized rats demonstrated an STP of phrenic motor output that appears to be mediated by NMDA receptors and is associated with facilitation of EPSPs and prolonged depolarization of individual phrenic motoneurons. We speculate that both GABAergic gain modulation of premotor neuronal activity and NMDA-mediated STP of phrenic activity may be neural substrates which are involved with the optimization of respiratory and non-respiratory behaviors, via adaptive and/or differential control of breathing.     

Light scattering changes follow evoked potentials from hippocampal Schaeffer collateral stimulation

We assessed relationships of evoked electrical and light scattering changes from cat dorsal hippocampus following Schaeffer collateral stimulation. Under anesthesia, eight stimulating electrodes were placed in the left hippocampal CA field and an optic probe, coupled to a photodiode or a charge-coupled device camera to detect scattered light changes, was lowered to the contralateral dorsal hippocampal surface. Light at 660 +/- 10 (SE) nm illuminated the tissue through optic fibers surrounding the optic probe. An attached bipolar electrode recorded evoked right hippocampal commissural potentials. Electrode recordings and photodiode output were simultaneously acquired at 2.4 kHz during single biphasic pulse stimuli 0.5 ms in duration with 0.1-Hz intervals. Camera images were digitized at 100 Hz. An average of 150 responses was calculated for each of six stimulating current levels. Stimuli elicited a complex population synaptic potential that lasted 100-200 ms depending on stimulus intensity and electrode position. Light scattering changes peaked 20 ms after stimuli and occurred simultaneously with population spikes. A long-lasting light scattering component peaked 100-500 ms after the stimulus, concurrently with larger population postsynaptic potentials. Optical signals occurred over a time course similar to that for electrical signals and increased with larger stimulation amplitude to a maximum, then decreased with further increases in stimulation current. Camera images revealed a topographic response pattern that paralleled the photodiode measurements and depended on stimulation electrode position. Light scattering changes accompanied fast electrical responses, occurred too rapidly for perfusion, and showed a stimulus intensity relationship not consistent with glial changes.     

Effect of Glycine max lectin on the interaction of prothrombin and erythrocytes

Native porcine erythrocytes do not initiate blood coagulation, though even the weak association (Kd = 4,25 +/- 9,35 microM) of prothrombin with their surface which is limited to the projection of two phospholipid polar head groups onto the external cell membrane, exerts a slight but authentic influence on the acceleration of blood clotting. There are 11.9 x 10(7) sites for 125I-prothrombin on one erythrocytes. At physiological concentration of prothrombin the surface of erythrocytes is far from saturation. The binding of 125I-labelled prothrombin to erythrocytes after their surface was covered by lectin Glycine max by means of the accessible residues of N-acetyl-D-galactosamine and D-galactose, glycoproteins and dlycolipids can never become saturated with any used concentration of the ligand. In the presence of the suspension of erythrocytes treated lectin platelet free plasma coagulates at the same speed as the control plasma.     

Development and implementation of an extremity free-tissue-transfer database

Rigorous clinical outcomes research requires accurate, complete, and standardized data. No such system is currently being used by reconstructive microsurgeons to evaluate free-tissue-transfer procedures. To facilitate collection of relevant and complete data, the authors propose a standardized format for data collection regarding these procedures. Data are collected via computer entry or scannable forms. The database includes sociodemographic, clinical, health/functional status, patient satisfaction, and resource utilization variables--the necessary components of a well-constructed clinical outcome study. Such studies will give rise to meaningful treatment algorithms for managing reconstructive problems. In addition, widespread use of a standardized databse will facilitate comparisons between practices and allow for meta-analyses. Resultant practice guidelines and microsurgery care maps will ultimately improve patient care and minimize unnecessary costs.     

Thymineless death in colon carcinoma cells is mediated via fas signaling

Fas is expressed constitutively in colonic epithelial cells and is also expressed in colon carcinomas and in cultured colon carcinoma cell lines. However, the potential role of Fas signaling in mediating apoptosis in cells of this type remains unknown. We have developed human colon carcinoma cell models deficient in thymidylate synthase that demonstrate acute (TS- cells) or delayed (Thy4 cells) apoptosis following DNA damage induced by thymineless stress. Complete protection of cells from acute apoptosis and prolongation of delayed apoptosis was obtained following exposure to the NOK-1 monoclonal antibody (inhibitory to Fas signaling) during the period of dThd deprivation. These results suggested that apoptosis induced by thymineless stress was regulated by autocrine signaling via Fas-FasL interactions. Fas expression was high in both TS- and Thy4 cells. However, FasL, undetectable in synchronous cultures, was up-regulated in TS- cells at 48 hr, when cells were undergoing acute apoptosis, and in Thy4 cells at 96 hr, correlating with the delayed onset of thymineless death. FasL expression also correlated with acute apoptosis induced in parental GC3/cl cells, commencing at 48 hr, following thymidylate synthase inhibition by 5-fluorouracil/leucovorin exposure. Fas-mediated apoptosis induced by the cytotoxic anti-Fas monoclonal antibody CH-11 was inhibited following adenoviral delivery of a Bcl-2 cDNA, and Bcl-2 also protected cells from acute apoptosis induced by dThd deprivation. Taken together, these data demonstrate a functional Fas system in these cultured colon carcinoma cell models, and they demonstrate that Fas-FasL interactions can link DNA damage induced by thymineless stress to the apoptotic machinery of colon carcinoma cells.     

Differential retinoic acid radiosensitization of cervical carcinoma cell lines

The potential of retinoic acid as a radiosensitizer was investigated using SiHa and CC-1 human uterine cervical carcinoma cell lines, representative of high- and low-grade lesions, respectively. SiHa was significantly (P < 0.05) radiosensitized, whereas CC-1 was not. Although 48 h of treatment with 5 microM 13-cis-retinoic acid prior to irradiation was sufficient to induce radiosensitization, continuation of treatment after irradiation significantly increased the effect (P < 0.05). Three hypotheses were tested to explain the different responses of the two lines. One hypothesis was that SiHa is more sensitive to retinoic acid than CC-1. Measurement of growth revealed that SiHa was more sensitive to growth inhibition by retinoic acid than CC-1. The second hypothesis was that retinoic acid increases the proportion of G1-phase cells in SiHa but not in CC-1. This was found not to be true, because a retinoic acid treatment schedule that induced radiosensitization did not alter cell cycle distribution profiles in the absence of radiation. The third hypothesis was that retinoic acid alters the cell cycle response of SiHa but not CC-1 to radiation. Postirradiation cell cycle profiles revealed that retinoic acid increased G1 delay in SiHa, whereas CC-1 exhibited no significant G1 delay. Both lines exhibited G2 delays that were unaffected by retinoic acid. In conclusion, radiosensitization of SiHa but not CC-1 may be explained by different sensitivities to retinoic acid and differences in postirradiation cell cycle responses. Radiosensitization at radiation doses used clinically was observed when retinoic acid was administered both before and after irradiation.     

In vitro antimicrobial activity and MIC quality control guidelines of RPR 106972 (RPR 112808/RPR106950): a novel orally administered streptogramin combination. The Quality Control Study Group

Thymidylate synthase (TS) inhibitor effects on growth of human head and neck squamous cell carcinoma (HNSCC) cell lines and CCRF-CEM human leukemia cells and sublines with acquired methotrexate (2,4-diamino-10-methylpteroylglutamic acid) (MTX) resistance were studied. During 120-h treatment, HNSCC cell lines A253 and FaDu are equally sensitive to MTX, whereas the polyglutamylatable TS inhibitors ZD1694 and BW1843U89 are 5- to 35-fold more potent than MTX and the lipophilic AG331 is approximately 10(2)-fold less potent than MTX. A253 is intrinsically resistant to intermittent (24 h) MTX and BW1843U89 exposure (higher EC50 values and shallower slopes of concentration-response curves relative to FaDu); AG331 and ZD1694 largely overcome this intrinsic resistance to intermittent exposure. Thymidine (TdR) protects against growth inhibition by these inhibitors, confirming that TS is their target in HNSCC; at high AG331 levels, TdR only partially protects, implying that a second site of action exists. Growth inhibition of HNSCC by ZD1694 and BW1843U89 is protected by leucovorin (LV) at > or = 10(-7) and > 10(-3) M, respectively; 10(-4) M LV cannot protect HNSCC cells against AG331. Results similar to protection studies are obtained if LV addition is delayed < or = 24 h after ZD1694 or BW1843U89 exposure. CCRF-CEM sublines with acquired MTX resistance resulting from dihydrofolate reductase (DHFR) overexpression, defective MTX transport, or defective MTX polyglutamylation retain full sensitivity to AG331. Cells with defective MTX transport are highly cross-resistant to ZD1694 and BW1843U89, implicating the reduced folate/MTX carrier in their transport. Minor cross-resistance of the DHFR overexpressing line to ZD1694 and BW1843U89 is observed. A subline with highly defective MTX polyglutamylation is cross-resistant to 120-h exposure to ZD1694, but not to BW1843U89, suggesting a profound contribution of polyglutamylation to the mechanism of action of ZD1694.