Effects of medium-chain triglycerides on brush border membrane-bound enzyme activity in rat small intestine

The effects of various types of dietary fat on brush border membrane-bound enzymes in rat intestinal mucosa were examined. Four groups of five rats were pair-fed defined diets for 10 d. The control group was fed a diet containing 57% sucrose and 2% corn oil as a fixed carbohydrate reference; the three experimental groups received diets containing 57% sucrose and 2% corn oil plus 13% fat in the form of medium-chain triglycerides (MCT) or long-chain triglycerides (LCT) (either lard as a highly saturated fat or corn oil as a highly unsaturated fat). Feeding LCT compared to the control diet, decreased sucrase activity in mucosal brush borders of the duodenum and jejunum. In these segments of MCT-fed rats, sucrase activity was similar to that in the control animals. In another experiment, measuring immunoreactive sucrase-isomaltase in jejunal brush border membranes revealed that feeding a high corn oil diet, but not a high MCT diet, led to a reduction in the sucrase catalytic activity per unit weight of enzyme protein, suggesting that the degradation status of sucrase-isomaltase might be altered by the different types of dietary fats. With MCT feeding, jejunal alkaline phosphatase activity was enhanced to a large extent compared to the activity in other groups. Feeding MCT, compared to lard or corn oil, also increased microvillus phospholipids of the jejunal mucosa. These results suggest that MCT, unlike LCT, do not suppress the activity of mucosal microvillus membrane enzymes in rat small intestine.     

Purification, properties, and developmental changes of cellular retinol-binding protein, type II, in chicken intestine

Two distinct cellular retinol-binding proteins were detected in chicken small intestine. A predominant form was purified to homogeneity. The apparent molecular weight of this protein was estimated to be 17,200. This form was larger than a second minor form partially purified (molecular weight of 15,000). The absorption and fluorescence spectra of the bound retinol to the purified proteins were typical for the known cellular retinol-binding proteins. The results suggest that the purified binding protein corresponds to CRBP(II), previously identified in small intestine of rats and humans. To gain an insight into the possible role of CRBP(II) in chicken small intestine, the CRBP(II) contents in cytosols of small intestine of embryonic and post-hatch chicks were determined by enzyme-linked immunosorbent assay. The amount of CRBP(II) per unit DNA in small intestine was low at 15- and 17-day embryonic stage, but rapidly increased around the period of hatching. The increased level was still maintained in 6-week-old chicks, which accounted for 0.9% of total proteins in duodenum. The developmental pattern and the presence of abundant amount of CRBP(II) in chicken small intestine supports the hypothesis that CRBP(II) might play some role in the intestinal absorption of retinoids. Thus the involvement of a tissue-specific cellular retinol-binding protein in the intestinal absorption of retinoids appears to be common in mammalian and avian species.     

Left ventricular diastolic dysfunction as assessed by echocardiography in metabolic syndrome.

The purpose of the present study was to elucidate the cardiac structure and function in patients who have metabolic syndrome but no history of cardiovascular disease by analyzing echocardiographic findings. Echocardiographic examination was performed to screen for cardiovascular disease in 135 patients who were in their sixties. Patients were divided into metabolic syndrome (n=65, age: 65+/-2.7 years) and non-metabolic syndrome (n=70, age: 66+/-2.5 years) groups based on the criteria for metabolic syndrome proposed by the Japanese Society of Hypertension and seven other societies in 2005. The left ventricular (LV) wall thickness and dimension were measured by M-mode echocardiography. The relative wall thickness, LV mass index, and LV ejection fraction (LVEF) were calculated. LV diastolic function was assessed by the peak velocity of early rapid filling (E velocity) and the peak velocity of atrial filling (A velocity), and the ratio of E to A (E/A) was assessed by the transmitral flow. The Tei index, which reflects both LV diastolic and systolic function, was also calculated. There were no differences in relative wall thickness, LV mass index, or LVEF between the two groups. However, both the EIA and Tei index were significantly different between the metabolic syndrome (0.66+/-0.14 and 0.36+/-0.07, respectively) and non-metabolic syndrome (0.88+/-0.25 and 0.29+/-0.09) groups (p<0.001). These results indicate that patients with metabolic syndrome can have cardiac diastolic dysfunction even if they have neither LV hypertrophy nor systolic dysfunction.     

Use of epr oximetry with india ink to measure the po2 in the liver in vivo in mice

The partial pressure of oxygen (pO₂) of the liver in vivo in unanesthetized mice was determined using electron paramagnetic resonance (EPR) oximetry with India ink. The EPR spectra were obtained using a low-frequency (1.2 GHz) EPR spectrometer with a loop gap cavity resonator. The line width of the India ink used in this experiment was reversibly broadened by oxygen and was particularly sensitive to pO₂ below 30 torr. After the administration of India ink into the tail vein, the India ink particles were taken up mainly by Kupffer cells in the liver and in part by phagocytes in the spleen. The pO₂ measured in the normal liver was about 14 torr and was constant for the 2-week experimental period. The pO₂ decreased when measured at 1, 2, and 6 days after treatment with a hepatotoxin (carbon tetrachloride (CCI₄)); within 2 weeks, it returned almost to the initial level. Measurements by EPR at sacrifice of controls and CCI₄-treated mice indicated that more than 90% of the India ink went to the liver; the spleen contained 4.7% of total amount in control mice and 8.8% in CCI₄-treated mice when measured 2 weeks after the treatment. These data indicate the usefulness of India ink for measuring the pO₂ of the liver in vivo and that the pO₂ in the Kupffer cells is decreased when the liver is damaged by CCI₄.     

Induction and activation of the aryl hydrocarbon receptor by IL-4 in B cells

It is widely known that IL-4 and IL-13 act on various kinds of cells, including B cells, resulting in enhancement of proliferation, class switching to IgE and expression of several surface proteins. These functions are important for the recognition of the various antigens in B cells and are known to be involved in the pathogenesis of allergic diseases. However, it has not been known whether IL-4/IL-13 is involved in the metabolism of various kinds of xenobiotics including 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), and it remains undetermined whether TCDD, an environmental pollutant, influences IgE production in B cells, exaggerating allergic reactions. We identified IL-4- or IL-13-inducible genes in a human Burkitt lymphoma cell line, DND-39, using microarray technology, in which the AHR gene was included. The AHR gene product, the aryl hydrocarbon receptor (AhR), was induced by IL-4 in both mouse and human B cells in a STAT6-dependent manner. IL-4 alone had the ability to translocate the induced AhR to the nuclei. TCDD, a ligand for AhR, rapidly degraded the induced AhR by the proteasomal pathway, although IL-4-activated AhR sustained its expression. AhR activated by IL-4 caused expression of a xenobiotic-metabolizing gene, CYP1A1, and TCDD synergistically acted on the induction of this gene by IL-4. However, the induction of AhR had no effect on IgE synthesis or CD23 expression. These results indicate that the metabolism of xenobiotics would be a novel biological function of IL-4 and IL-13 in B cells, whereas TCDD is not involved in IgE synthesis in B cells.     

Organ design for generation and reception of CO: lessons from the liver

Carbon monoxide (CO) is synthesized in vivo by heme oxygenase. Although for many years CO had been regarded as potentially toxic waste, recent studies have indicated that it is a signaling molecule with important physiological functions. Nitric oxide (NO), another diatomic diffusible gas, is regarded as an established signaling molecule. Structural similarities between CO and NO have led many investigators to draw analogies between the two gaseous mediators. Whereas the NO signaling system has been well defined as to its receptor molecule, soluble guanylate cyclase, the CO system has been conceived to require further tuning with respect to identifying its receptor molecules and its downstream effectors. Furthermore, there has been little quantitative information to argue for a physiological role of CO in vivo. This review, therefore, focuses on recent developments on both physiologic and pathophysiologic roles of CO in the model of isolated perfused liver of rats where endogenous production of CO is actually estimated. This model has revealed that CO acts as an endogenous vasorelaxant in the liver and that effects of CO are at least in part cyclic GMP-dependent. It has also provided answers to many questions of hepatobiliary functions that had not been resolved because of the complexity introduced by the interplay between NO and CO.     

Effects of intravenous nitroglycerin combined with dopamine on intracranial pressure and cerebral arteriovenous oxygen difference in patients with acute subarachnoid haemorrhage

Summary The effects of intravenous nitroglycerin (NTG) combined with dopamine on intracranial pressure (ICP) and cerebral arteriovenous oxygen difference (AVDO₂) were studied in 11 patients with acute subarachnoid haemorrhage (SAH). The study was performed on Days 1 to 3 of SAH after aneurysmal clipping. Treatment consisted of an intravenous drip infusion of NTG in increasing incremental doses of 0.5, 1.0, 1.5, 2.0, and 2.5 g/kg/min at one-hour intervals. Dopamine (5 to 10 g/kg/min) was also given concurrently to maintain systemic blood pressure. ICP values before NTG administration ranged from 7 to 24 mmHg (mean, 11.91±5.30 mmHg). ICP began to increase immediately after the adminisration of NTG 0.5 g/kg/min and peaked at 14.64±5.93 mmHg 10 minutes after onset of infusion. Thereafter, ICP gradually returned to pretreatment levels. Increasing the dose of NTG failed to induce further significant rises in ICP. Mean AVDO₂ before NTG administration was 4.69±0.62 ml/dl. This parameter showed no significant change during NTG infusion, although cerebral perfusion pressure decreased to between 75% to 94% of the control value after NTG administration. These results indicate that continuous NTG infusion combined with dopamine does not have adverse effects on ICP (the ICP increase is minimal and transient) and may even have beneficial effects on CBF in patients with acute SAH.