Propofol-induced unresponsiveness is associated with impaired feedforward connectivity in cortical hierarchy.

BACKGROUND: Impaired consciousness has been associated with impaired cortical signal propagation after transcranial magnetic stimulation (TMS). We hypothesised that the reduced current propagation under propofol-induced unresponsiveness is associated with changes in both feedforward and feedback connectivity across the cortical hierarchy. METHODS: Eight subjects underwent left occipital TMS coupled with high-density EEG recordings during wakefulness and propofol-induced unconsciousness. Spectral analysis was applied to responses recorded from sensors overlying six hierarchical cortical sources involved in visual processing. Dynamic causal modelling (DCM) of induced time-frequency responses and evoked response potentials were used to investigate propofol's effects on connectivity between regions. RESULTS: Sensor space analysis demonstrated that propofol reduced both induced and evoked power after TMS in occipital, parietal, and frontal electrodes. Bayesian model selection supported a DCM with hierarchical feedforward and feedback connections. DCM of induced EEG responses revealed that the primary effect of propofol was impaired feedforward responses in cross-frequency theta/alpha-gamma coupling and within frequency theta coupling (F contrast, family-wise error corrected P<0.05). An exploratory analysis (thresholded at uncorrected P<0.001) also suggested that propofol impaired feedforward and feedback beta band coupling. Post hoc analyses showed impairments in all feedforward connections and one feedback connection from parietal to occipital cortex. DCM of the evoked response potential showed impaired feedforward connectivity between left-sided occipital and parietal cortex (T contrast P=0.004, Bonferroni corrected). CONCLUSIONS: Propofol-induced loss of consciousness is associated with impaired hierarchical feedforward connectivity assessed by EEG after occipital TMS.

Disruption of cortical network activity by the general anaesthetic isoflurane.

BACKGROUND: Actions of general anaesthetics on activity in the cortico-thalamic network likely contribute to loss of consciousness and disconnection from the environment. Previously, we showed that the general anaesthetic isoflurane preferentially suppresses cortically evoked synaptic responses compared with thalamically evoked synaptic responses, but how this differential sensitivity translates into changes in network activity is unclear. METHODS: We investigated isoflurane disruption of spontaneous and stimulus-induced cortical network activity using multichannel recordings in murine auditory thalamo-cortical brain slices. RESULTS: Under control conditions, afferent stimulation elicited short latency, presumably monosynaptically driven, spiking responses, as well as long latency network bursts that propagated horizontally through the cortex. Isoflurane (0.05-0.6 mM) suppressed spiking activity overall, but had a far greater effect on network bursts than on early spiking responses. At isoflurane concentrations >0.3 mM, network bursts were almost entirely blocked, even with increased stimulation intensity and in response to paired (thalamo-cortical + cortical layer 1) stimulation, while early spiking responses were <50% blocked. Isoflurane increased the threshold for eliciting bursts, decreased their propagation speed and prevented layer 1 afferents from facilitating burst induction by thalamo-cortical afferents. CONCLUSIONS: Disruption of horizontal activity spread and of layer 1 facilitation of thalamo-cortical responses likely contribute to the mechanism by which suppression of cortical feedback connections disrupts sensory awareness under anaesthesia.

Calpain activation through galectin-3 inhibition sensitizes prostate cancer cells to cisplatin treatment.

Prostate cancer will develop chemoresistance following a period of chemotherapy. This is due, in part, to the acquisition of antiapoptotic properties by the cancer cells and, therefore, development of novel strategies for treatment is of critical need. Here, we attempt to clarify the role of the antiapoptotic molecule galectin-3 in prostate cancer cells using siRNA and antagonist approaches. The data showed that Gal-3 inhibition by siRNA or its antagonist GCS-100/modified citrus pectin (MCP) increased cisplatin-induced apoptosis of PC3 cells. Recent studies have indicated that cisplatin-induced apoptosis may be mediated by calpain, a calcium-dependent protease, as its activation leads to cleavage of androgen receptor into an androgen-independent isoform in prostate cancer cells. Thus, we examined whether calpain activation is associated with the Gal-3 function of regulating apoptosis. Here, we report that Gal-3 inhibition by siRNA or GCS-100/MCP enhances calpain activation, whereas Gal-3 overexpression inhibits it. Inhibition of calpain using its inhibitor and/or siRNA attenuated the proapoptotic effect of Gal-3 inhibition, suggesting that calpain activation may be a novel mechanism for the proapoptotic effect of Gal-3 inhibition. Thus, a paradigm shift for treating prostate cancer is suggested whereby a combination of a non-toxic anti-Gal-3 drug together with a toxic chemotherapeutic agent could serve as a novel therapeutic modality for chemoresistant prostate cancers.

ATENCIÓN ATÍPICA. Una alternativa al tratamiento farmacológico de expectación / ATYPICAL ATTENTION An alternative to pharmacological treatment of expectation

Introducción: Las técnicas de neuroimagen funcional destacan el papel de la atención en la fisiopatología de algunos trastornos mentales, por lo que parece adecuado buscar nuevas alternativas al tratamiento farmacológico que puedan influir funcionalmente sobre los sustratos neurológicos de la atención. Objetivos: Reforzar nuestro conocimiento acerca de la atención, percibida funcionalmente como un sistema, y demostrar cómo la sugestión puede modificada focalmente. Desarrollo: La hipnosis o atención atípica es una forma de concentración atento-receptiva que, adecuadamente instruida, puede ayudar al sujeto a modificar el patrón de activación funcional de áreas cerebrales como las cortezas cingular anterior y prefrontal, y suprimir procesos automáticos como la lectura. La hipnoterapia ha sido empleada con éxito en la regulación del dolor, tics, trastornos conversivos y ansiedad. La susceptibilidad a la hipnosis puede medirse mediante escalas validadas con excelentes propiedades psicométricas y es mayor durante la pubertad, lo que resulta atractivo para el tratamiento de adolescentes. Conclusiones: La atención está centralmente implicada en la fisiopatología de algunos trastornos mentales. La hipnosis puede influir en el sustrato neurológico de la atención. La susceptibilidad a la hipnosis presenta un pico en la pubertad. La hipnoterapia puede constituir una alternativa terapéutica viable en Psiquiatría Infanto-juvenil

Introduction: Since functional neuroimaging techniques highlight the role of attention in the pathophysiology of mental disorders, it seems appropriate to look for new alternatives to pharmacological treatments that can influence the neural substrates of attention. Objetives: To enhance our knowledge of how attention can be perceived as an organ system and to demonstrate how suggestion can focally modify it. Discussion: Hypnosis or atypical attention is a form of attentive-receptive concentration that, together with the proper instruction, can help a subject modify the functional activation pattern of such brain areas as the anterior cingular cortex and prefrontal cortex activation and to suppress an involuntary process such as the word reading. Hypnotherapy has been used successfully in the regulation of pain, tics, conversion disorders, and anxiety. Hypnotic susceptibility can be measured using standardized scales with excellent psychometric functions. It peaks in puberty, which makes it attractive for treating adolescents. ConcIusions: Attention is centrally involved in the pathophysiology of certain mental disorders. Hypnosis can influence the neural substrate of attention. Susceptibility to hypnosis peaks in puberty. Hypnotherapy may constitute a viable alternative to pharmacological treatments in Child and Adolescent Psychiatry

Is pre-attentive processing compromised by prolonged wakefulness? Effects of total sleep deprivation on the mismatch negativity.

We investigated the potential influence of sustained wakefulness on pre-attentive capacities by recording the mismatch negativity (MMN), an electrophysiological manifestation associated with nonintentional detection of auditory oddball stimuli. The MMN was elicited by pitch deviants presented to both ears via earphones, at the beginning of a total sleep deprivation session (baseline), after 24 hr, and after 36 hr of continuous controlled wakefulness. A conspicuous MMN response was elicited at all three sessions. With time, however, a small yet significant gradual reduction in the MMN amplitude was evident. Whereas previous research suggested that controlled attention-demanding tasks are hampered by sleep deprivation, the balance of the present results suggests that passive (total) sleep deprivation may also bring about some degradation in the pre-attentive detection of environmental irregularities and as a consequence may disrupt the reflexive shift of attention induced by such events.

Electrospray/tandem mass spectrometry for quantitative analysis of lipid remodeling in essential fatty acid deficient mice.

A method utilizing electrospray ionization coupled with tandem mass spectrometry was developed as a facile and rapid method to identify and quantify lipid remodeling in vivo. Electrospray/tandem mass spectrometric analyses were performed on lipids isolated from liver tissue and resident peritoneal cells from essential fatty acid sufficient and deficient mice. Essential fatty acid deficiency was chosen as the paradigm to evaluate the methodology because it epitomizes the most extreme dietary means of altering fatty acid composition of virtually all cellular lipid species. Qualitative and quantitative changes were measured in the phospholipid and cholesterol ester species directly in the chloroform/methanol lipid extract without any prior chromatographic separation. Lipid remodeling in liver and peritoneal cells from essential fatty acid deficient mice was qualitatively similar in cholesterol ester, phosphatidylcholine, and phosphatidylethanolamine. The monoenoic fatty acids palmitoleic acid (16:1 n-7) and oleic acid (18:1 n-9) were increased markedly, whereas all n-6 and n-3 polyunsaturated fatty acids were nearly depleted in phospholipid and cholesterol ester species. The n-9 polyunsaturated fatty acid surrogate, Mead acid (20:3 n-9), substituted for arachidonic acid (20:4 n-6) and docosahexaenoic acid (22:6 n-3) in phospholipid, but not in cholesterol ester, species. Another notable difference was that adrenic acid (22:4 n-6) and docosapentaenoic acid (22:5 n-6), both metabolites of arachidonic acid, accumulated in phospholipid and cholesterol ester species of peritoneal cells, but not in liver cells, of essential fatty acid sufficient mice. The overall body of data presented illustrates the implementation of electrospray/tandem mass spectrometry as a method for facile and direct quantification of changes in lipid species during lipid metabolic studies.

The effect of fish oil on hypertension, plasma lipids and hemostasis in hypertensive, obese, dyslipidemic patients with and without diabetes mellitus.

We have recently reported that dietary fish oil supplementation (n-3) polyunsaturated fatty acid (PUFA) led to a reduction in blood pressure (BP) and serum triglycerides (TG), in addition to the normalization of the hypercoagulable state in subjects with obesity, hypertension and dyslipidemia without diabetes mellitus (OHD-DM). The aim of the present study was to explore the mechanism of this amelioration by comparing the previous results to those obtained from 19 subjects who, in addition to the conditions described above, also suffer from diabetes mellitus (OHD+DM) and proteinuria. In both the non-diabetic and diabetic groups, a similar reduction was observed in BP (from 158.7/80.8 to 146/72.9 mmHg, and from 157.6/83.2 to 141.9/75.6 mmHg, respectively, P<0.001) and TG levels (from 159.2 to 108.0 mg/dl and from 208.7 to 153.1 mg/dl, respectively, P<0.001). However, a favorable reduction in hemostasis parameters (platelet aggregation on extracellular matrix and (alpha2-antiplasmin) was only seen among the nondiabetic patients (from 12.1+/-4.9 to 4.2+/-3.2%, P<0.001). This difference may stem from a less efficient exchange between n-3 and n-6 PUFA in serum phospholipid of the OHD+DM patients. Overall, this 13-day fasting/refeeding method developed by us has proven to cause the rapid exchange of arachidonic acid for eicosapentaenoic acid. It appears to be an effective regimen for the reduction of cardiovascular risk factors (BP, TG and hemostatic variables) in OHD-DM patients and to a lesser extent in OHD+DM patients.

Identification and characterization of a novel delta6/delta5 fatty acid desaturase inhibitor as a potential anti-inflammatory agent.

The anti-inflammatory properties of essential fatty acid deficiency or n-3 polyunsaturated fatty acid supplementation have been attributed to a reduced content of arachidonic acid (AA; 20:4 n-6). An alternative, logical approach to depleting AA would be to decrease endogenous synthesis of AA by selectively inhibiting the delta5 and/or the delta6 fatty acid desaturase. High-throughput radioassays were developed for quantifying delta5, delta6, and delta9 desaturase activities in vitro and in vivo. CP-24879 (p-isopentoxyaniline), an aniline derivative, was identified as a mixed delta5/delta6 desaturase inhibitor during the screening of chemical and natural product libraries. In mouse mastocytoma ABMC-7 cells cultured chronically with CP-24879, there was a concentration-dependent inhibition of desaturase activity that correlated with the degree of depletion of AA and decreased production of leukotriene C4 (LTC4). Production of LTC4 was restored by stimulating the cells in the presence of exogenous AA, indicating that endogenous AA was limiting as substrate. In the livers of mice treated chronically with the maximally tolerated dose of CP-24879 (3 mg/kg, t.i.d.), combined delta5/delta6 desaturase activities were inhibited approximately 80% and AA was depleted nearly 50%. These results suggest that delta5 and/or delta6 desaturase inhibitors have the potential to manifest an anti-inflammatory response by decreasing the level of AA and the ensuing production of eicosanoids.

Modulation of adjuvant-induced arthritis by dietary arachidonic acid in essential fatty acid-deficient rats.

Controlled feeding of linoleic acid (LA) or arachidonic acid (AA) to essential fatty acid-deficient (EFAD) rats was used to define the relationship between dietary AA and the inflammatory response evoked during adjuvant-induced arthritis. Based on energy percentage, EFAD rats were fed AA at the human daily equivalent (1x; 5.5 mg/day) or 10 times that amount (10x; 55 mg/day) or, alternatively 0.5x of LA (273 mg/day). Feeding of 0.5x LA restored the plasma level of AA to that in chow-fed controls. In contrast, feeding of 1x AA only partially restored the plasma level of AA; 10x AA was required to fully replete AA. In parallel to the degree of repletion of AA in plasma, there were accompanying decreases in the levels of palmitoleic acid, oleic acid, and Mead acid. Compared to rats fed the standard laboratory chow diet (Control), edema in the primary hind footpads was decreased by 87% in EFAD, 71% in EFAD + 1x AA, 45% in EFAD + 10x AA, and 30% in EFAD + 0.5x LA. The decrease in edema in the footpads of EFAD rats was nearly identical to the decrease in edema in the footpads of Control rats dosed with indomethacin. Hind footpad edema correlated with the final AA plasma level and eicosanoid levels extracted from hind footpad tissue, but not with neutrophil infiltration. The data showed that 0.5x LA and 10x AA, but not 1x AA, could quickly replete AA, accompanied by the synthesis of AA-derived eicosanoids and restoration of edema. These results suggest that in humans consumption of the average daily amount of AA without concurrent ingestion of LA would not alleviate an EFAD state.

Repeated fasting and refeeding with 20:5, n-3 eicosapentaenoic acid (EPA): a novel approach for rapid fatty acid exchange and its effect on blood pressure, plasma lipids and hemostasis.

Twenty hypertensive subjects participated in three clinical trials of 13 days each, to examine the effects of Alsepa fish oil [20:5, n-3 eicosapentaenoic acid (EPA) 180 mg, and 22:6 n-3 docosahexaenoic acid (DHA) 120 mg] on n-3 for n-6 polyunsaturated fatty acids (PUFA) exchange on serum phospholipids, blood pressure (BP), triglycerides (TG) and primary hemostasis. After 13 days, plasma phospholipids showed an increase in sigma n-3 (EPA and DHA) from 2.0 to 5.9% (P < 0.01), and a decrease in sigma n-6 (arachidonic acid and linoleic acid) from 29.8 to 22.6% (P < 0.01). A concomitantly significant reduction in systolic BP (SBP) (158.7 +/- 23.8 mm Hg to 146.5 +/- 17.0 mm Hg, P = 0.04), and diastolic BP (DBP) (80.8 +/- 8.4 mm Hg to 72.9 +/- 14.9 mm Hg, P = 0.04) as well as a significant decrease in platelet adhesion and aggregation on extra cellular matrix measured as a percentage of surface coverage (11.9 +/- 4.8% to 4.2 +/- 3.2%, P = 0.0001) was observed. In addition, a significant reduction in baseline dependent TG was observed; the higher the baseline level TG, the more pronounced the reduction (average 159.2 +/- 74.6 mg% to 108.0 +/- 46.1 mg%, P = 0.001). No change was observed in total cholesterol, high and low density lipoprotein (HDL, LDL), platelet and fibrinogen. Repeated fasting and refeeding with fish oil facilitated plasma exchange of n-3 for n-6 PUFA, improved BP, clinical metabolic parameters and lowered platelet reactivity in the vessel wall (primary hemostasis). In severe and life-threatening situations, the beneficial effects of fish oil should be considered for rapid exchange of n-3 for n-6 PUFA. In this study we describe a novel approach for rapid fatty acid exchange by fasting/refeeding with fish oil supplementation, as well as improved BP, plasma lipids and primary hemostasis. Further research is required on the therapeutic use of fish oils and the physiological mechanisms involved in fatty acid exchange.

Inhibition of spontaneous metastasis in a rat prostate cancer model by oral administration of modified citrus pectin.

BACKGROUND: Prostate cancer is the most common cancer diagnosed in U.S. men and remains incurable once it has metastasized. Many stages of the metastatic cascade involve cellular interactions mediated by cell surface components, such as carbohydrate-binding proteins, including galactoside-binding lectins (galectins). Modified citrus pectin (pH-modified), a soluble component of plant fiber derived from citrus fruit, has been shown to interfere with cell-cell interactions mediated by cell surface carbohydrate-binding galectin-3 molecules. PURPOSE: The aim of this study was to determine whether modified citrus pectin, a complex polysaccharide rich in galactosyl residues, could inhibit spontaneous metastasis of prostate adenocarcinoma cells in the rat. METHODS: The ability of modified citrus pectin to inhibit the adhesion of Dunning rat prostate cancer MAT-LyLu cells to rat endothelial cells was measured by 51Cr-labeling. Modified citrus pectin inhibition of MAT-LyLu cell anchorage-independent growth was measured by colony formation in agarose. The presence of galectin-3 in rat MAT-LyLu cells and human prostate carcinoma was demonstrated by immunoblotting and immunohistochemistry. One million MAT-LyLu cells were injected subcutaneously into the hind limb of male Copenhagen rats on day 0. Rats were given 0.0%, 0.01%, 0.1%, or 1.0% (wt/vol) modified citrus pectin continuously in their drinking water (from day 4 until necropsy on day 30). The number of MAT-LyLu tumor colonies in the lungs were counted. RESULTS: Compared with 15 or 16 control rats that had lung metastases on day 30, seven of 14 rats in the 0.1% and nine of 16 rats in the 1.0% modified citrus-pectin group had statistically significant (two-sided; P < .03 and P < .001, respectively) reductions in lung metastases. The lungs of the 1.0% modified citrus pectin-treated rats had significantly (two-sided; P < .05) fewer metastatic colonies than control groups (9 colonies +/- 4 [mean +/- SE] in the control group compared with 1 colony +/- 1 in the treated group). Modified citrus pectin had no effect on the growth of the primary tumors. In vitro, modified citrus pectin inhibited MAT-LyLu cell adhesion to rat endothelial cells in a time- and dose-dependent manner as well as their colony formation in semisolid medium. CONCLUSIONS: We present a novel therapy in which oral intake of modified citrus pectin acts as a potent inhibitor of spontaneous prostate carcinoma metastasis in the Copenhagen rat. IMPLICATIONS: Further investigations are warranted to determine the following: 1) the role of galectin-3 in normal and cancerous prostate tissues and 2) the ability of modified citrus pectin to inhibit human prostate metastasis in nude mice.

Effects of natural complex carbohydrate (citrus pectin) on murine melanoma cell properties related to galectin-3 functions.

Citrus pectin (CP) and pH-modified citrus pectin (MCP) are highly branched and non-branched complex polysaccharides, respectively, rich in galactoside residues, capable of combining with the carbohydrate-binding domain of galectin-3. We reported previously that intravenous injection of B16-F1 murine melanoma cells with CP or MCP into syngeneic mice resulted in a significant increase or decrease of lung colonization, respectively (Platt D, Raz A (1992) J Natl Cancer Inst 84:438-42). Here we studied the effects of these polysaccharides on cell-cell and cell-matrix interactions mediated by carbohydrate-recognition. MCP, but not CP, inhibited B16-F1 melanoma cells adhesion to laminin and asialofetuin-induced homotypic aggregation. Both polysaccharides inhibited anchorage-independent growth of B16-F1 cells in semisolid medium, i.e. agarose. These results indicate that carbohydrate-recognition by cell surface galectin-3 may be involved in cell-extracellular matrix interaction and play a role in anchorage-independent growth as well as the in vivo embolization of tumour cells.

Oral ciprofloxacin in the management of chronic suppurative otitis media without cholesteatoma in children: preliminary experience in 21 children.

The current medical management of children with chronic suppurative otitis media without cholesteatoma unresponsive to local treatment and oral antibiotics is intravenous antibiotic therapy in the hospital setting. We studied the efficacy and toxicity of oral ciprofloxacin in chronic suppurative otitis media. Twenty-one children received oral ciprofloxacin, 30 mg/kg/day. Ear discharge was positive for bacteria resistant to other oral medications and susceptible to the quinolones. The mean duration of treatment was 16.7 days. In 18 children suppuration ceased and 3 failed their first course. During a mean follow-up of 15.4 months, 6 children remained free of ear, nose and throat problems. Otorrhea recurred in 12 children. Ear cultures were positive for organisms susceptible to amoxicillin in 5 of them. In 7 cases Pseudomonas aeruginosa was again isolated from otorrhea. Repeated antibiotic therapy was advocated only in 3 (2 responded to ciprofloxacin; 1 failed ciprofloxacin and was cured by ceftazidime). Adverse clinical effects were not observed. Transient neutropenia was observed in 1 child. There was no change in the height percentile. The results of this study show that children with chronic suppurative otitis media without cholesteatoma can be effectively treated with oral ciprofloxacin. This novel approach may prevent hospitalization.

Modulation of the lung colonization of B16-F1 melanoma cells by citrus pectin.

CONTEXT: Studies have shown that the galactoside-containing simple sugars and anti-galactoside-binding lectin antibodies may affect experimental tumor cell metastasis. However, the limited number of reagents used thus far necessitate further observations. PURPOSE: Natural citrus pectin (CP) and pH-modified CP (MCP), rich in galactose residues, were used to study the involvement of carbohydrates containing galactoside residues in cellular interaction in vitro and in lung colonization in vivo of B16-F1 melanoma cells. METHODS: B16-F1 melanoma cells were incubated with various concentrations of CP and MCP. Their ability to form homotypic aggregation in vitro and tumor lung colonization in vivo in 8-week-old female C57BL/6 mice was then analyzed. RESULTS: The CP binds to the surface of B16-F1 melanoma cells; this binding can be inhibited by lactose at a concentration of 0.15 M. Intravenous injection of the murine B16-F1 melanoma cells with the natural CP resulted in a significant increase (up to threefold) in the appearance of tumor colonies in the lung and in increased homotypic aggregation properties of the cells, while injection of MCP significantly decreased B16-F1 experimental metastasis (greater than 90%). CONCLUSIONS: Tumor galactoside-binding proteins mediate cellular recognition by linking oligosaccharides with terminal D-galactoside residues on adjacent cells. Successful interference with such a process with MCP may lead to a reduced ability to form tumor cell emboli and metastasis. IMPLICATIONS: These findings imply that the galactose-containing carbohydrate side chains of CP might mimic or compete with the natural ligand(s) of the tumor galactoside-binding protein (gal-lectin) and thus affect cellular interactions relevant for metastasis.

Radioimmunoassay of human plasma retinol-binding protein.

A radioimmunoassay for human plasma retinol-binding protein (RBP) has been developed utilizing a double antibody precipitation technique. RBP was purified 1500- to 2000-fold by procedures described previously. A specific anti-human RBP antiserum was prepared in rabbits by three once-weekly injections of purified RBP emulsified with Freund's adjuvant. RBP was iodinated with (131)I and the RBP-(131)I was purified by gel filtration on Sephadex G-100 after complex formation with human plasma prealbumin. The RBP-(131)I was completely (> 95%) immunoprecipitable in the presence of an excess of specific antiserum, it was not (< 5%) immunoprecipitable in the absence of specific antiserum, and it could be completely displaced from antibody by excess unlabeled RBP. The standard curve obtained in the immunoassay with normal plasma was identical to that with pure RBP. Duplicate samples differed from their mean by 5 +/-5% (+/-SD). There was a quantitative recovery of pure RBP added in varying amounts to normal plasma. The immunoassay accurately measured RBP in amounts of 10-100 ng per assay tube. There was no significant difference in the immunoreactivity of apo-RBP as compared to holo-RBP. The mean plasma values (+/-SEM) for a group of 76 normal subjects were 47.2 +/-1.6 mug/ml for males and 41.6 +/-1.6 mug/ml for females. Plasma RBP levels were markedly depressed (15 +/-2.3 mug/ml) in 14 patients with acute viral hepatitis. There was a highly significant correlation between the plasma levels of RBP and of vitamin A in both normal subjects and patients with hepatitis. In all subjects plasma RBP was generally saturated with retinol. The data suggest that under normal circumstances RBP circulates almost exclusively as the holoprotein.