A new hypothesis about the relationship between free radical reactions and hemorheological properties in vivo

This paper is concerned with a hypothesis that disturbance of free radical reactions may lead to abnormality of hemorheological properties in vivo, and so the free radicals generated in vivo may damage certain tissue cells indirectly by reducing the supply of oxygen and nutrients to these cells through slowing the circulation of blood. This hypothesis is based on the following evidence: A. We have found that the whole blood viscosity at low shear rate correlates to the lipid peroxidation in the patients suffering from certain cardio- or cerebrovascular diseases, and in dogs during liver ischemia reperfusion or hemorrhagic pancreatitis. B. Reports have shown that several alterations of hemorheological properties may take place as a result of free radical reactions, such as lipid peroxidation. For instance, lipid peroxidation may lead to decrease of deformability of red cells, increase of aggregation of red cells, formation of liquid thrombin, etc. C. We have demonstrated that some alterations of hemorheological properties involve the role of free radicals in rats suffering from intestinal ischemia/reperfusion. As evidence for this conclusion, superoxide dismutase (SOD) used as a specific scavenger of superoxide anion radical (O2-) can significantly prevent the intestinal ischemia/reperfusion induced changes of lipid peroxidation, red cell aggregation, Cassion's viscosity and whole blood viscosity at low shear rate in rats.

Steric constraints in the retinal binding pocket of sensory rhodopsin I

Steric constraints in the retinal binding pocket of sensory rhodopsin I (SR-I) are analyzed by studying effects of sample temperature and retinal analogs. The flash-induced yield of the earliest detected intermediate S610, which corresponds to the K intermediate in the bacteriorhodopsin (BR) photocycle, decreases below 220 K and reaches zero at 100 K, while K formation is independent of temperature. The reduced S610 formation at low temperatures indicates a more restricted retinal binding pocket in SR-I during primary photochemical events. Introduction of bulky substituents on the retinal polyene chain in four retinal analogs greatly retards or blocks the final step of chromophore binding to the apoprotein of SR-I. Except for the 14-methyl substitution, these modifications exhibit little or no effect on chromophore binding to BR apoprotein. These results corroborate that the retinal polyene chain binding domain in SR-I is more sterically constrained than that of the retinal pocket in BR. Deletion of the beta-ionone ring renders the analog SR-I pigments nonfunctional, as does deletion of the 13-methyl group, but the corresponding BR analogs are both photochemically and physiologically active. In contrast to the corresponding BR analog, photolysis of the analog SR-I reconstituted with 13-desmethylretinal does not produce an S610-like intermediate at room temperature. The above results and the previous findings that protein constraints inhibit the accommodation of a stable 13-cis-retinal configuration in SR-I suggest a model in which the 13-methyl group functions as a fulcrum to permit movement of one or both ends of retinal to overcome an energy barrier against isomerization.

Sensitivity increase in the photophobic response of Halobacterium halobium reconstituted with retinal analogs: a novel interpretation for the fluence-response relationship and a kinetic modeling

Phoborhodopsin (also called sensory rhodopsin II) is a photoreceptor protein which mediates photophobic responses of Halobacterium halobium to blue-green light. Under conditions where the synthesis of the chromophore retinal is inhibited, the photophobic system is reconstituted in vivo by incorporation of all-trans retinal or retinal analogs into the apoprotein of phoborhodopsin. Retinal analogs which retard the cyclic photoreaction kinetics of phoborhodopsin increase significantly the sensitivity of the photophobic response. This supports the previously reported hypothesis that signal amplification occurs during the lifetime of intermediate states of the photocycle. The sensitivity increase caused by the chromophore substitution is observed in cells at several different growth stages, i.e. the naturally occurring chromophore (all-trans retinal) does not produce maximal sensitivity at any stage of the culture growth. These results are difficult to interpret in terms of the proposal by Marwan et al. (J. Mol. Biol. 199, 663-664, 1988) that only a single photon is sufficient to cause the photobehavioral response in cells containing native phoborhodopsin. A new interpretation for the fluence-response curves is described based in part on their Poisson statistical analysis. Further, a kinetic model which relates the receptor photochemical reaction cycle to the behavioral response is developed, which accounts for both the sensitivity increase and the shape of the fluence-response curves.

Transformation of a bop-hop-sop-I-sop-II-Halobacterium halobium mutant to bop+: effects of bacteriorhodopsin photoactivation on cellular proton fluxes and swimming behavior

We have transformed Pho81, a Halobacterium halobium mutant strain which does not contain any of the four retinylidene proteins known in this species, with the bop gene cluster to create Pho81BR, a BR+HR-SR-I-SR-II-strain. The absorption spectrum, pigment reconstitution process, light-dark adaptation and photochemical reaction cycle of the expressed protein are indistinguishable from those of native bacteriorhodopsin (BR) in purple membrane of wild type strains. Strain Pho81BR permits for the first time characterization of effects of BR photoactivation alone on cell swimming behavior and energetics in the absence of the spectrally similar phototaxis receptor sensory rhodopsin I (SR-I) and electrogenic chloride pump halorhodopsin (HR). A non-adaptive upward shift in spontaneous swimming reversal frequency occurs following 3 s of continuous illumination of Pho81BR cells with green light (550 +/- 20 nm). This effect is abolished by low concentrations of the proton ionophore carbonylcyanide m-chlorophenylhydrazone. Although BR does not mediate phototaxis responses in energized Pho81BR cells under our culture conditions, proton pumping by BR in Pho81BR cells partially deenergized by inhibitors of respiration and adenosine triphosphate synthesis results in a small attractant response. Based on our measurements, we attribute the observed effects of BR photoactivation on swimming behavior to secondary consequences of electrogenic proton pumping on metabolic or signal transduction pathways, rather than to primary sensory signaling such as that mediated by SR-I. Proton extrusion by BR activates gated proton influx ports resulting in net proton uptake in wild-type cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Genes for beta-thromboglobulin and platelet factor 4 are closely linked and form part of a cluster of related genes on chromosome 4

The small inducible gene (SIG) family encodes related proteins that are involved in the overlapping processes of coagulation, inflammation, immune response, and wound repair. This family contains two branches, termed CXC and CC, which are distinguished by whether or not the first two of four conserved cysteine residues are separated by an additional amino acid residue. All of the CXC SIGs map to chromosome 4, including those encoding beta-thromboglobulin (beta TG) and platelet factor 4 (PF4), both of which are expressed by megakaryocytes in a tissue-specific fashion. Both of these latter two genes have been previously reported to be duplicated, there being a PF4 and a PF4alt gene, and a beta TG1 and beta TG2 gene. We now show by pulse-field gel electrophoresis (PFGE) that the beta TG genes are closely linked to the PF4 genes and to other previously mapped CXC SIGs, namely IL8 (encoding interleukin-8), GRO1 (encoding a cytokine also called melanoma growth-stimulatory activity), and two related genes GRO2 and GRO3, on a single 700-kb Sfil fragment localized to chromosome bands 4q12-q13. The only CXC SIG not linked to this cluster is that encoding gamma-interferon-induced 10-Kd protein (INP10), which has been previously localized to 4q21. Analysis of lambda genomic clones demonstrate that the beta TG1 and PF4 genes are separated by less than 7 kb, and the beta TG2 and PF4alt genes by approximately 5 kb. Within each beta TG/PF4 duplication, the beta TG-like gene is upstream of its linked PF4-like gene. Thus, the beta TG/PF4 genes appear to form a close-linked complex expressed in a megakaryocyte-specific fashion. Further genomic studies may provide additional insights into the regulation of the tissue-specific expression of the beta TG/PF4 gene complex, while further analysis of the linked CXC SIG cytokine family may provide further understanding of their evolutionary history.

Evidence that the repellent receptor form of sensory rhodopsin I is an attractant signaling state

The lifetime of the Halobacterium halobium sensory rhodopsin I (SR-I) photocycle intermediate S373 was modulated by incorporating retinal analogs into SR-I apoprotein in vitro and in vivo. Photocycles by SR-I analog pigments exhibit the same reaction scheme and similar formation rates, but different decay rates, of their S373-like species as monitored by flash spectroscopy in membrane vesicle suspensions. The attractant receptor signaling efficiencies determined by physiological measurements are proportional to the lifetimes of the S373-like intermediates, indicating that S373 is a physiological active conformation (signaling state) of the receptor. A model incorporating this finding into the SR-I photocycle is presented.

Identification of signaling states of a sensory receptor by modulation of lifetimes of stimulus-induced conformations: the case of sensory rhodopsin II

Lifetimes of stimulus-induced conformations of the phototaxis receptor sensory rhodopsin II (SR-II) from Halobacterium halobium are modulated with seven receptor analogues. By monitoring the receptor dynamics in vitro and physiological responses of the cell in vivo, we observe receptor signaling efficiency increases with decreasing cycling frequency (turnover number) of the receptor. The results demonstrate that modulating lifetimes of protein conformations at the SR-II photoactivation site with chromophore analogues alters the lifetime of the active conformation at the signaling site. We further explore the relationship between photocycle intermediates and the signaling efficiency by analyzing the time-averaged concentrations of the two long-lived spectral intermediates of the SR-II photocycle: S-II350 and S-II530. The results are consistent with the signaling site being activated during formation of S-II350, but not reset by the transition of S-II350 into S-II530; rather deactivation appears to require subsequent decay of S-II530. The results indicate the structural changes at the photoactivation site in the S-II350----S-II530 transition do not reset the signaling site. The procedure used here, applicable in principle to any photoactivated or ligand-activated receptor, provides an initial approach to identify structural alterations key to the receptor activation process.

Mechanism of activation of sensory rhodopsin I: evidence for a steric trigger

Sensory rhodopsin I (SR-I) and bacteriorhodopsin (BR) from Halobacterium halobium show broad structural and spectroscopic similarities and yet perform distinct functions: photosensory reception and proton pumping, respectively. Probing the photoactive sites of SR-I and BR with 24 retinal analogs reveals differences in the protein environments near the retinal 13-methyl group and near the beta-ionone ring. 13-cis-Retinal does not form a retinylidene pigment with the SR-I apoprotein, although this isomer binds to the BR apoprotein even more rapidly than all-trans-retinal, the functional isomer of both pigments. The activation of both SR-I and BR requires all-trans/13-cis isomerization of retinal;however, a steric interaction between the retinal 13-methyl group and the protein is required for SR-I activation but not for that of BR. These results reveal a key difference between SR-I and BR that is likely to be the initial diverging point in their photoactivation pathways. We propose the 13-methyl group-protein interaction functions as a trigger for SR-I activation--i.e., converts photon absorption by the chromophore into protein conformational changes. A similar steric trigger is essential for activation of mammalian rhodopsin, indicating a common mechanism for receptor activation in archaebacterial and vertebrate retinylidene photosensors.

Influence of endogenous Thy1.1 cells upon the efficacy of an anti-Thy1.1 antibody-diphtheria toxin conjugate

The chemical conjugation of antibodies to protein toxins results in cell-specific cytotoxic agents that can be defined in terms of in vitro potency and efficacy; however, it is the in vivo utilities that are largely being pursued in clinical trials. The nature of in vivo target cell depletion by toxin conjugates is largely unknown. The anti-murine Thy1.1 antibody-diphtheria toxin conjugate possesses high in vitro efficacy, and because mice are remarkably resistant to the native toxin, the conjugate possesses in vivo efficacy. When administered intravenously, the conjugate is shown to deplete peripheral blood Thy1.1+ target cells in a concentration-dependent fashion. When the log kill of Thy1.1+ tumor cells was analyzed by the life span extension method, it was determined, however, that the log kill is inversely proportional to the number of target cells. That is, the presence of an endogenous cell population, which is expressing the same surface antigen targeted by the antibody conjugate as on the pathological cell, may drastically lower the clinical efficacy of the immunotoxin. Thus, the greatest potential for antibody-toxin conjugates will be for low target cell burdens and for pathogenic cell populations expressing unique surface antigens. These are important considerations in the design of bioconjugates to insure high in vivo efficacy in elimination of intended target cells.

Development of the light response in neonatal mammalian rods

The sensitivity to light is low in many neonatal mammals when compared with that in the adult. In human infants at one month of age, for example, the dark-adapted sensitivity for detection of large stimuli is 50 times lower than in the adult, and in rats the overall sensitivity of the neonatal retina is also low compared with the adult. This low sensitivity in the neonate has been attributed to a number of factors, but the possibility that the photoreceptors themselves might be an important limitation on the overall visual sensitivity has not so far been clearly established. Here we record the light response of single neonatal rat rods and find that the sensitivity is considerably lower than in the adult. The response to a single photoisomerization is normal in the neonate, and the sensitivity deficit can therefore be attributed to a low level of functional rhodopsin. Opsin, the protein component of rhodopsin, must be present in normal amounts, as the sensitivity can be restored to adult levels by treating the retina with 9-cis retinal, an active homologue of the native chromophore 11-cis retinal. The low sensitivity of photoreceptors in the neonate can therefore be attributed mainly to a low concentration of 11-cis retinal in the developing retina.

Color regulation in the archaebacterial phototaxis receptor phoborhodopsin (sensory rhodopsin II)

Phoborhodopsin, a repellent phototaxis receptor in Halobacterium halobium, exhibits vibrational fine structure, a feature that has not been identified for any other rhodopsin pigment at physiological temperatures. This conclusion follows form analysis of the absorption properties of the pigment in H. halobium membranes containing native retinal and an array of retinal analogues. The absorption spectrum of the native pigment has a maximum at 487 nm with a pronounced shoulder at 460 nm; however, the bandwidth is that expected for a single retinylidene species. Gaussian band-shape simulation with a spacing corresponding to the vibrational frequencies of polyene stretching modes reproduces the structured absorption spectra of native pigment as well as of analogue phoborhodopsin. Absorption shifts produced by a series of dihydroretinal and other retinal analogues strongly indicate that the dominant factor regulating the color of the pigment is planarization of the retinal ring with respect to the polyene chain.

All-trans/13-cis isomerization of retinal is required for phototaxis signaling by sensory rhodopsins in Halobacterium halobium

An analogue of all-trans retinal in which all-trans/13-cis isomerization is blocked by a carbon bridge from C12 to C14 was incorporated into the apoproteins of sensory rhodopsin I (SR-I) and sensory rhodopsin II (SR-II, also called phoborhodopsin) in retinal-deficient Halobacterium halobium membranes. The "all-trans-locked" retinal analogue forms SR-I and SR-II analogue pigments with similar absorption spectra as the native pigments. Blocking isomerization prevents the formation of the long-lived intermediate of the SR-I photocycle (S373) and those of the SR-II photocycle (S-II360 and S-II530). A computerized cell tracking and motion analysis system capable of detecting 2% of native pigment activity was used for assessing motility behavior. Introduction of the locked analogue into SR-I or SR-II apoprotein in vivo did not restore phototactic responses through any of the three known photosensory systems (SR-I attractant, SR-I repellent, or SR-II repellent). We conclude that unlike the phototaxis receptor of Chlamydomonas reinhardtii, which has been reported to mediate physiological responses without specific double-bond isomerization of its retinal chromophore (Foster et al., 1989), all-trans/13-cis isomerization is essential for SR-I and SR-II phototaxis signaling.

Effects of modifications of the retinal beta-ionone ring on archaebacterial sensory rhodopsin I

Ring desmethyl and acyclic analogues of all-trans retinal were incorporated into the apoprotein of the phototaxis receptor sensory rhodopsin I (SR-I) in Halobacterium halobium membranes. All modified retinals generate SR-I analogue pigments which exhibit "opsin shifts," i.e., their absorption spectra are shifted to longer wavelengths compared with model protonated Schiff bases of the same analogues. Each SR-I pigment analogue exhibits cyclic photochemical reactions as monitored by flash spectroscopy, but the analogue photocycles differ from that of native SR-I by exhibiting pronounced biphasic recovery of flash-induced absorption changes and abnormal flash-induced absorption difference spectra. Despite perturbations in the photochemical properties, the SR-I pigment analogues are capable of both attractant (single photon) and repellent (two photon) phototaxis signaling in cells. Our interpretation is that the hydrophobic ring substituents interact with the binding pocket to maintain the correct configuration for native SR-I absorption and photochemistry, but these interactions are not essential for the physiological function of SR-I as a dual attractant/repellent phototaxis receptor. These results support the conclusion emerging from several studies that the photoactivation process that triggers the conformation changes of SR-I and the related proton pump bacteriorhodopsin is conserved despite the different biological functions of their photoactivation.

Studies of safe maximal daily dietary Se-intake in a seleniferous area in China. Part II: Relation between Se-intake and the manifestation of clinical signs and certain biochemical alterations in blood and urine

Selenosis occurs in areas of Enshi county because of the high Se content of the food. Morphological changes in finger-nails were used as the main criterion for clinical diagnosis of selenosis. Pathological nails were observed to occur almost only in adults, not at all in young children and very seldom in teenagers. Symptoms of selenosis in susceptible patients were found at or above an Se-intake of 910 micrograms/d, corresponding to a blood Se level of 1.05 mg/L. There was no evidence for an increased susceptibility to dental caries due to high Se consumption, and an increase in Se-intake seems unlikely to reduce the beneficial effects of fluoride on caries. No abnormalities of liver or heart were seen by supersonic B or electrocardiographic examinations. The biochemical investigations showed that with increasing whole blood Se the ratio of plasma Se to erythrocyte Se tended to decrease. As Se-intake increases to over 750 micrograms daily, the ratio decreases to near a minimal level. Reduced glutathione in whole blood decreases within a blood Se range of 1.01 to 2.28 micrograms in the high Se area. The amount of trimethylselenonium ion excreted in urine increased with the increase of urinary Se. Cases with prolonged prothrombin time occurred as blood Se increased to a level above 1 mg/L. The white blood cell count also increased significantly. Quantitative values were obtained only for ratio of plasma-Se to erythrocyte-Se for prothrombin time and for maintenance of nail Symptoms of susceptible patients. The overall results indicated that a daily Se-intake of 750-850 micrograms [corrected] might be the marginal level of safe intake. When other variable factors are also taken into consideration a daily Se-intake of 400 micrograms [corrected] is suggested as the maximum daily safe intake. At this level of Se-intake the corresponding approximate tissue Se levels are: whole blood 0.559 mg/L, plasma 0.327 mg/L, urine excretion 173 micrograms/d, hair 3.60 mg/kg, toe-nails 4.25 mg/kg, and finger-nails 4.70 mg/kg.

Studies of safe maximal daily dietary selenium intake in a seleniferous area in China. I. Selenium intake and tissue selenium levels of the inhabitants

Studies of marginal safe Se-intake have been carried out in a seleniferous section of China since 1985. Three areas with low, medium and high Se levels were selected for this study. The respective average daily Se-intake (mean +/- SE) was 70.5 +/- 4.8 micrograms, 194.7 +/- 22.9 micrograms and 1438.2 +/- 76.3 micrograms for males, and 62.0 +/- 3.6 micrograms, 198.1 +/- 23.8 micrograms and 1238.5 +/- 64.6 micrograms for females (average body weight: male 55 Kg, female 53 Kg). When the increasing rate of Se-intake was compared with the corresponding tissue-Se levels it was found that the whole blood Se-level reflected more closely the physiological range of Se-intake, while at higher Se-intakes it became less sensitive than the levels in hair, finger-nail and toe-nail, which were comparable to the sensitivity of urine. It is suggested that hair, finger- and toe-nail may all act as excretory organs when excess amounts of Se are ingested. Hair- and blood-Cd are somewhat higher in residents of the high Se area, but whether they have influenced human Se-metabolism at the high level of Se-intake is not yet known. Significant correlations on log-log plots were obtained between levels of daily Se-intake and whole blood r = 0.878), breast milk (r = 0.899) and 24-h-urine (r = 0.859). Highly significant correlations on log-log plots between levels of tissue were also obtained: urine Se--plasma Se (r = 0.968), whole blood Se--hair Se (r = 0.952), fingernail Se--toenail Se (r = 0.919), hair Se--fingernail Se (r = 0.914), hair Se--toenail Se (r = 0.891), whole blood Se--toenail Se (r = 0.849) and whole blood Se--fingernail Se (r = 0.836). The highly significant correlations found between the Se-intake and the tissue-Se level, and also between the Se levels of various tissues, could possibly conveniently be used to convert the known tissue-Se level to the corresponding Se-intake. Taken together with the wide range of Se-intakes and corresponding tissue-Se levels this would provide the necessary conditions for studying the marginal and maximal safe Se-intakes in humans.

Nature of relapse after surgical mandibular advancement

Pre-operative, post-operative and follow-up cephalometric records of 16 cases of mandibular retrognathia treated by surgical mandibular advancement were analysed retrospectively. The results showed good mean stability in the mandibular advancement with variable individual relapse. The pre-operative mandibular plane angle, magnitude of the advancement and post-operative increase in the posterior lower face height were the variables chiefly related to relapse. There appeared to be limited control over the posterior segment which was liable to distraction and rotation. The follow-up changes were time linked. Both mechanical and biological factors are postulated to explain the relapse.