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51.
Ghan Shyam Lohiya Hubert Pirkle Hoan Nguyen Sunita Lohiya Tran Vuu 《The Western journal of medicine》1988,148(4):426-429
We reviewed records of all persons dying between 1979 and 1986 in eight California institutions for the mentally retarded. Autopsies had been done in 71% of the 1,181 deaths. Nine deaths were due to hepatocellular carcinoma, which invariably developed in carriers of hepatitis B surface antigen (HBsAg) and was fatal within four months of diagnosis. The mean age at death was 32.7 years. The incidence of hepatocellular carcinoma in HBsAg carriers was 140 times greater than in the US population. Persistent hepatitis B infection was probably etiologically related to hepatocellular carcinoma in this population, which is relatively free of exposure to other hepatocarcinogens. 相似文献
52.
Summary A simple method is proposed for calculating oxygen pentration depth in immobilized cells by assuming zero order kinetics in the presence of several external oxygen transport resistances. Calculations indicate that typical penetration depths of oxygen for immobilized microbial cells are in the range of 50–200 and those for immobilized or encapsulated animal and plant tissue culture are about 500–1000 . Based on calculations, oxygen transport in microencapsulation and microcarriers for tissue cultures are not transport-limited, but a slight limitation is expected for those in a hollow fiber reactor.Nomenclature as
specific area of a support (cm)
- Bi
Biot number
-
dimensionless
- Cb
oxygen concentration in the bulk liquid (mM)
-
C
b
C
b
*
-Ccr (mM)
- C
b
*
bulk oxygen concentration in equilibrium with air (mM)
- Ccr
critical oxygen concentration (mM)
- Cs
oxygen concentration in the solid phase (mM)
- dp
diameter or thickness of a support (cm)
- Deff
effective diffusivity of oxygen in the solid phase (cm2/s)
- km
membrane permeability of oxygen (cm/s)
- k
m
*
Deff/m
- kLaL
liquid phase mass transfer rate coefficient (1/s)
- ksas
solid phase mass transfer rate coefficient (1/s)
- (OUR)v
volumetric oxygen uptake rate (mmol O2/l)
- p
geometry parameter, p=0 for slab, p=1 for cylinder, p=2 for sphere
- Pd
oxygen penetration depth (cm)
-
P
d
oxygen penetration depth in the absence of external diffusion limitation (cm)
- Q
volumetric oxygen uptake rate,
(mmol O2/l·h)
-
specific oxygen uptake rate (mmol O2gm biomass (dry)·h)
- r
length coordinate (cm)
- rc
oxygen penetration depth for sphere (cm)
-
r
c
rc in the absence of external diffusion limitation (cm)
- r
c
*
oxygen penetration depth for cylinder (cm)
-
r
c
*
r
c
*
in the absence of external diffusion limitation (cm)
- rcom
combined mass transfer rate resistance (s)
- rd
location where Cs becomes zero or Ccr (cm)
- ri
radius of cylinder or sphere, half thickness of slab (cm)
- Usg
superficial gas velocity (cm/s)
- X
cell concentration (g/l)
Greek letters
Thiele modulus, dimensionless
- L, s
liquid and solid phase volume fraction, respectively, dimensionless
-
effectiveness factor
On sabbatical leave from KAIST, Seoul, Korea 相似文献
53.
Metal Ion Interactions with Phosphoenolpyruvate Carboxylase from Crassula argentea and Zea mays 总被引:1,自引:1,他引:0
Metal ion interactions with phosphoenolpyruvate carboxylase from the CAM plant Crassula argentea and the C4 plant Zea mays were kinetically analyzed. Fe2+ and Cd2+ were found to be active metal cofactors along with the previously known active metals Mg2+, Mn2+, and Co2+. In studies with the Crassula enzyme, Mg2+ yielded the highest Vmax value but also generated the highest values of Km(metal) and Km(pep). For these five active metals lower Km(metal) values tended to be associated with lower Km(pep) values. PEP saturation curves showed more kinetic cooperativity than the corresponding metal saturation curves. The activating metal ions all have ionic radii in the range of 0.86 to 1.09 Å. Ca2+, Sr2+, Ba2+, and Ni2+ inhibited competitively with respect to Mg2+, whereas Be2+, Cu2+, Zn2+, and Pd2+ showed mixed-type inhibition. Vmax trends with the five active metals were similar for the C. argentea and Z. mays enzymes except that Cd2+ was less effective with the maize enzyme. Km(metal) values were 10- to 60-fold higher in the enzyme from Z. mays. 相似文献
54.
Inhibition of macrophage activation by isoquinolinesulfonamides, phenothiazines, and a napthalenesulfonamide 总被引:1,自引:0,他引:1
The influence of isoquinolinesulfonamides (H-7 and H-8), phenothiazines(trifluoperazine and fluphenazine), and a naphthalenesulfonamide (N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) on stimulated superoxide anion production and phosphatidyl inositol (PI) cycle activity was investigated in the guinea pig alveolar macrophage. All five drugs were able to inhibit superoxide anion production stimulated by n-formyl-nel-leu-phe (FNLP), leukotriene B4 (LTB4), and phorbol-12,13-dibutyrate (PDB). The order of potency was trifluoperazine greater than or equal to fluphenazine greater than H-7 = W-7 greater than H-8. The dose response curves could be shifted to less efficacy by increasing extracellular calcium. By itself, W-7 markedly stimulated 45Ca+2 efflux, fluphenazine and trifluoperazine slightly stimulated 45Ca+2 efflux, while H-7 and H-8 had no effect on 45Ca+2 efflux from macrophages preloaded with 45Ca+2. Consistent with these results, W-7 markedly stimulated PI cycle activity, fluphenazine and trifluoperazine slightly stimulated PI cycle activity, while H-7 and H-8 had no significant effects on PI cycle activity. In addition, W-7 by itself was able to stimulate a weak and short-lived "burst" of superoxide anion production. In order to evaluate whether a site of action of the inhibitors was at protein kinase C and whether protein kinase C was involved in terminating the normally short-lived FNLP- and LTB4-stimulated macrophage activation, fluphenazine and H-7 were used to evaluate the duration of FNLP- and LTB4-stimulated PI cycle activity, at concentrations of the inhibitors that significantly blocked stimulated superoxide anion production. In all cases, FNLP and LTB4 still stimulated PI cycle activity, which still terminated even though protein kinase C was inhibited. These results suggest that all five drugs block protein kinase C, but H-7 was the most specific in its action at protein kinase C, while the phenothiazines and W-7 have multiple sites of action. In addition, these results suggest that protein kinase C may not function to cause the termination of FNLP- and LTB4-stimulated PI cycle activity and subsequent superoxide anion production. 相似文献
55.
The aspiration of gastric acid causes pulmonary edema and hypoxemia. One approach to the management of this syndrome is to raise cardiac output (Qt) and O2 delivery (QO2) to ensure tissue oxygenation (VO2) at the risk of increasing the edema. Another approach reduces the edema by reducing pulmonary microvascular pressure (Pmv) at the risk of reducing QO2 and VO2. We compared these approaches in 24 anesthetized, ventilated dogs with pulmonary wedge pressure (Ppw), a clinical approximation of Pmv, of 12.5 mmHg. Before and again 1 h after endobronchial instillation of 0.1 N HCl, we measured Qt, QO2, VO2, venous admixture, and in vivo extravascular lung liquid. The dogs were then randomly divided into four equal groups: 1) 12.5 mmHg Ppw, high Qt; 2) 7.5 mmHg Ppw, intermediate Qt; 3) 4.5 mmHg Ppw, low Qt; and 4) 4.5 mmHg Ppw plus dopamine, intermediate Qt. Measured values were followed for 4 more h, after which the lungs were excised to compare wet weight-to-body weight ratios (W/B). When plasmapheresis reduced Ppw at 1 h, edema did not increase further and W/B of groups 2 (21 +/- 3), 3 (18 +/- 3), and 4 (22 +/- 3) were significantly less than in group 1 (27 +/- 3) (P less than 0.001). Although Qt decreased with Ppw, increased hematocrit and reduced venous admixture maintained QO2 in group 2 but not in group 3. In group 4 an intermediate Qt maintained QO2 even at 4.5 mmHg Ppw but edema increased to the group 2 level presumably because Pmv rose with Qt on dopamine. VO2 remained constant over time in each group. These data demonstrate that canine HCl-induced pulmonary edema, measured in vivo or gravimetrically, is very sensitive to reductions in Pmv. Moreover, the lowest Pmv (and QO2) was well tolerated because an O2 supply dependency of VO2 was not observed. 相似文献
56.
Summary Two alternative estimators of individual tree leaf area (A1) area are used to derive estimates of leaf-area index (L) for 40 plots in Pinus contorta Dougl. stands. One estimator of A1 is based on the common assumption of a constant ratio between A1 and sapwood cross-sectional area at breast height (As). The second estimator of A1 accounts for tree-to-tree variation in the relation between A1 and As. The apparent relationship between stand growth and leaf-area index is strongly dependent on the way leaf area is estimated. When L is derived from a constant A1As ratio, stand growth appears to be strongly correlated with L. However, when L is based on estmates of A1 that account for tree-to-tree variation in the A1 — As relation, stand growth is seen to be only weakly related to L. Stand structure, quantified as percent live-crown, accounts for a great deal of the observed variation in leaf-area efficiency. These contrasting relationships illustrate the importance of unbiased estimates of L in interpreting the link between stand-level processes and leaf area.Utah Aggriculural Experiment Station Journal Paper No. 3333 相似文献
57.
Neuropeptide Y (NPY) elicits eating when injected directly into the paraventricular nucleus (PVN) or perifornical hypothalamus (PFH). To identify the essential regions of the NPY molecule and the relative contributions of Y1 and Y2 receptors, the eating stimulatory potency of NPY was compared to that of its fragments, analogues, and agonists when injected into the PVN or PFH of satiated rats. Additionally, antisera to NPY was injected into the cerebral ventricles (ICV) to determine whether passive immunization suppresses the eating produced by mild food deprivation. Tests with NPY fragments revealed that NPY(2-36) was surprisingly potent, nearly three times more so than intact NPY. In contrast, fragments with further N-terminal deletions were progressively less effective or ineffective, as was the free acid form of NPY. Collectively, this suggests that both N- and C-terminal regions of NPY participate in the stimulation of eating. Tests with agonists revealed that the putative Y1 agonist [Pro34]NPY elicited a strong dose-dependent feeding response, while the putative Y2 agonist, C2-NPY, had only a small effect at the highest doses. Although this suggests mediation by Y1 receptors, the uncharacteristically high potency of NPY(2-36) may additionally suggest that the receptor subtype underlying feeding is distinct from that mediating other responses. Additional results revealed that ICV injection of antisera to NPY, which should inactivate endogenous NPY, produced a concentration-dependent suppression of eating induced by mild food deprivation. This finding, along with published work demonstrating enhanced levels of hypothalamic NPY in food-deprived rats, suggests that endogenous NPY mediates the eating produced by deprivation. 相似文献
58.
We investigated the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator on insulin receptors and insulin action in freshly isolated and primary cultures of rat hepatocytes. PMA (1 x 10–7 M) did not alter insulin receptor numbers or affinity either acutely or chronically but within 60 minute inactivated insulin stimulated tyrosine kinase of the insulin receptor. PKC activation inhibitied insulin (1 x 10–7M) stimulation of glycogen and lipid synthesis with a decrease or no change in basal glycogenesis and lipogenesis respectively. However, PKC activation did not alter insulin stimulated or basal amino acid transport even though PCK activation inhibited insulin stimulation of the insulin. receptor tyrosine kinase. Thus, within one tissue, PKC activation has differential effect on insulin action depending on which pathway is examined. Furthermore, insulin stimulation of the insulin receptor tyrosine kinase may not be a necessary step for all insulin signaling pathways. 相似文献
59.
A V Smyshliaeva L H Nguyen Iu B Kudriashov 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1992,(4):9-13
The preparation Hypericum perforatum L. has been shown to decrease the intensity level of enzymatic and non-enzymatic processes of lipid peroxidation of rat liver microsomes in vitro and in vivo. In the mucus of the this intestine in vivo the increase of the number of non-enzymatic SH-groups is observed. Possible mechanisms of radioprotective action of the preparation is under discussion. 相似文献
60.
Indirect immunofluorescence microscopy has been used to investigate the ultraviolet (UV) radiation induced disruption of the organization of microfilaments, keratin intermediate filaments, and microtubules in cultured human epidermal keratinocytes. Following irradiation, concurrent changes in the organization of the three major cytoskeletal components were observed in cells incubated under low Ca2+ (0.15 mM) conditions. UV irradiation induced a dose-dependent condensation of keratin filaments into the perinuclear region. This collapse of the keratin network was accompanied by the reorganization of microfilaments into rings and a restricted distribution of microtubules, responses normally elicited by exposure to high Ca2+ (1.05 mM) medium. The UV induced alteration of the keratin network appears to disrupt the interactions between keratin and actin, permitting the reorganization of actin filaments in the absence of Ca2+ stimulation. In addition to the perinuclear condensation of keratin filaments, UV irradiation inhibits the Ca2+ induced formation of keratin alignments at the membrane of apposed cells if UV treatment precedes exposure to high Ca2+ medium. Incubation of keratinocytes in high Ca2+ medium for 24 hours prior to irradiation results in the stabilization of membrane associated keratin alignments and a reduced susceptibility of cytoplasmic keratin filaments to UV induced disruption. Unlike results from investigations with isogenic skin fibroblasts, no UV induced disassembly of microtubules was discernible in irradiated human keratinocytes. 相似文献