Antimicrobial activity of rabbit CAP18-derived peptides

A cationic antimicrobial protein of 18 kDa (CAP18) was originally isolated from rabbit granulocytes by using as an assay the agglutination of Re-lipopolysaccharide-coated erythrocytes. The C-terminal 37 amino acids of CAP18 (CAP18(106-142)) make up the lipopolysaccharide-binding domain. Synthetic CAP18(106-142) has broad antimicrobial activity against both gram-positive (50% inhibitory concentration, 130 to 200 nM) and gram-negative (50% inhibitory concentration, 20 to 100 nM) bacteria. Susceptible strains include Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium. Antimicrobial activity is highly dependent on peptide structure. Although a 32-amino-acid peptide resulting from the truncation of 5 amino acids from the C terminus of CAP18(106-142) is highly active, other fragments of CAP18(106-142), including CAP18(106-142) with a truncated N terminus, do not exhibit antimicrobial activity. Unlike previously characterized antimicrobial peptides derived from granulocyte proteins, CAP18(106-142) is active in serum. CAP18(106-142) or a derivative peptide may have therapeutic potential for bacterial sepsis.

Role of protein phosphorylation in TNF-induced apoptosis: phosphatase inhibitors synergize with TNF to activate DNA fragmentation in normal as well as TNF-resistant U937 variants

This study examined the role of protein phosphorylation in TNF induction of apoptosis in several tumor cell lines by testing the effects of agents that either stimulate or inhibit protein phosphorylation. The serine-threonine phosphatase inhibitors, okadaic acid (OKA) and calyculin A (CLA), synergistically augmented TNF-induced apoptosis in several TNF-sensitive tumor cell lines including the U937 histiocytic lymphoma, the BT-20 mammary carcinoma, and the LNCap prostatic tumor cell line. Furthermore, the phosphatase inhibitors completely reversed the TNF resistance of a variant (U9-TR) derived from U937. CLA also inhibited phosphatase activity in cell-free extracts from both U937 and U9-TR at the same concentrations (0.4-2.0 nM) that it synergized with TNF. In contrast, TNF treatment of U937 cells did not result in inhibition of phosphatase activity mediated by protein phosphatase 1 (PP1) and PP2A in cell extracts. Since the phosphatase inhibitors are known to increase the overall levels of protein phosphorylation in cells, this suggested that TNF may act by stimulating protein kinase (PK) activity. This hypothesis was supported by the results of testing a panel of relatively specific protein kinase inhibitors. TNF activation of DNA fragmentation was blocked by a potent inhibitor of myosin light chain kinase (MLCK) but was unaffected by inhibitors of cAMP or cGMP-dependent PKs. We postulate that a defect in the activation of MLCK or possibly some other as yet unknown PK may be responsible for the TNF resistance of U9-TR. Furthermore, this resistance may be circumvented by promoting protein phosphorylation with the serine-threonine-dependent phosphatase inhibitors.

Changes in water diffusion and relaxation properties of rat cerebrum during status epilepticus

Diffusion-weighted (DW) imaging has been used to record changes associated with status epilepticus (SE) in rat brain. It was found that the apparent diffusion coefficient (ADC) of water in brain decreased 14-18% during SE, and it fell a further 20-22% when the animals were sacrificed. The transverse decay time constant T2* showed corresponding reductions, but no significant changes were seen in relaxation times T1 or T2 values. Changes in ADC in status epilepticus are similar to those seen in stroke and ischemia but occur under very different conditions of blood flow and metabolism.

Nicotine inhibition of apoptosis suggests a role in tumor promotion

Recent evidence indicates that cell death through apoptosis may be an important mechanism to prevent tumor development. Therefore, agents that inhibit apoptosis may function as tumor promoters. The purpose of this study was to determine the effects of nicotine on the process of apoptosis. The results demonstrate that nicotine inhibits apoptosis induced by diverse stimuli including tumor necrosis factor (TNF), UV light, chemotherapeutic drugs, and calcium ionophore. This phenomenon was observed in normal and transformed cells derived from a variety of species and tissues, including tumor cell types related to tobacco use. The major nicotine metabolite, cotinine, also inhibited apoptosis, whereas N-nitrosodiethylamine, a carcinogen found in tobacco, was without effect. Therefore, nicotine-mediated inhibition of apoptosis may contribute to the pathogenesis of tobacco-related cancer as well as decrease the efficacy of cancer therapies.

On generalized photocurrent spectral moments and the recovery of speed distribution in laser Doppler flowmetry

Laser Doppler flowmetry (LDF) is a noninvasive method to assess tissue blood flow. By calculating the first moment of the Doppler signal power spectral density, a real-time output is generated that scales linearly with the perfusion flux defined as the product of average speed and concentration of moving blood cells (MBC's) if multiple scattering is negligible. However, this first spectral moment alone is apparently deficient to provide further information about the MBC's under study and therefore unable to answer more intricate questions in LDF. Without assuming any specific MBC speed or scattering vector distribution, a generalized formula for photocurrent spectral moments is first derived in the case of low and moderate MBC concentration. Then as a direct and important use of the formula, the speed distribution of MBC's is obtained via Henyey-Greenstein phase function and a Fourier inversion. The important implications and applications of this formulation in extracting more MBC information are discussed together with some other related issues.

Urinary excretion of nitrosamino acids and nitrate by inhabitants of high- and low-risk areas for nasopharyngeal carcinoma in southern China

The hypothesis that endogenous synthesis of nitrosamines from dietary precursors is a risk factor for nasopharyngeal carcinoma (NPC) in China was tested by applying the nitrosoproline (NPRO) test to subjects living in high- and low-risk districts for NPC in Zangwu county, Guangxi region, in southern China. Samples of 12-h urine were collected from 77 subjects: (a) before any treatment; (b) after ingestion of proline; and (c) after ingestion of proline together with vitamin C. NPRO, other nitrosamino acids, and nitrate were measured as indices of exposure to preformed and endogenously formed nitrosamines or their precursors. The NPRO level after proline intake was significantly increased in subjects from the high-risk area (P = 0.012) and markedly reduced after ingestion of ascorbic acid (P = 0.007), but such an effect was not seen in subjects from the low-risk area. Levels of N-nitrosothiazolidine-4-carboxylic acid and the sum of nitrosamino acids in subjects in the high-risk area were significantly reduced by ascorbic acid (P < 0.01) but were not reduced in subjects from the low-risk area. The urinary nitrate level was about twice as high in subjects from the high-risk area. In subjects from high- and low-risk areas combined, NPRO levels in any of the three dose groups were highly correlated with nitrate levels (P = 0.0001). These results demonstrate a higher potential for endogenous nitrosation in subjects living in the high-risk area of NPC and suggest the occurrence of nitrosation inhibitors in the diet consumed in the low-risk area.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and experimental studies on tong yu ling in the treatment of diabetic hyperlipemia

72 diabetes mellitus patients (70 cases non-insulin-dependent) were treated routinely with D860. After one month, cases with persisting hyperglycemia and hyperlipemia were randomly divided into Group A to be treated with D860 plus Tong Yu Ling (TYL), and Group B to continue treatment with D860 alone, while Group C, comprising cases with persisting hyperlipemia only, were treated with TYL alone. Therapeutic results showed that of the total 50 cases of Group A and C, 26 were markedly improved, 14 improved, and 10 cases ineffective. The antihyperlipemic effect was pronounced in Group A, where the blood cholesterol, beta-lipoprotein and triglyceride showed remarkable decline, less pronounced in Group C, and insignificant in Group B. Experiments in rat models of non-insulin-dependent diabetes demonstrated that TYL was markedly effective in treating hyperlipemia.

[The immunologic studies on experimental heterogeneous penetrating keratoplasty]

Using the experimental model of chicken-rabbit penetrating corneal grafting, micro-whole-blood 3H-TdR incorporation and ELISA the authors dynamically observed the functional state of cellular and humoral immunities for 10 weeks after operation. The results showed, (1) In both the homogroup and the hetero-group, the transformational degree of lymphocytes in peripheral blood increased, most obviously in the 3rd or 4th week postoperatively. (2) In the hetero-group, specific anti-corneal antibody appeared obviously in the serum during 2-8 weeks postoperatively. Combined with morphologic observation, it has proved that: (1) The immune rejection is mainly cellular mediated immunoresponse, meanwhile, the humoral immunoresponse also participates in it, and the humoral immunoresponse participates in the heterokeratoplasty more obviously. (2) Applying the micro-whole-blood 3H-TdR incorporation is capable of determining the immunologic state of the body after corneal transplantation. (3) Attention should be focused on the 3-4 week period postoperatively when immunosuppressive-agent is administered.

Inhibitory effect of rhynchophylline on platelet aggregation and thrombosis

Rhynchophylline (Rhy) inhibited rabbit platelet aggregation induced by arachidonic acid (AA), collagen, and ADP. The values of IC50 were 0.72, 0.74, and 0.67 mmol.L-1, respectively. Rhy reduced the thromboxane B2 (TXB2) generation in PRP induced by collagen but failed to reduce that induced by AA. Rhy suppressed malondialdehyde (MDA) formation in platelet suspension stimulated by thrombin, inhibited the platelet factor 4 (PF4) release. It did not alter intraplatelet cAMP concentration. Rhy 10-20 mg.kg-1 iv showed a significant inhibition of venous thrombosis and cerebral thrombosis in rats.

Factors influencing contrast in fast spin-echo MR imaging

Multi-echo pulse sequences for producing T2-weighted images in much reduced imaging times have recently been developed for routine clinical use. A number of recent articles have described the contrast obtained with fast spin-echo (FSE) sequences and have generally indicated that they depict tissues very similarly to conventional spin-echo (SE) imaging. There are, however, some important differences in contrast between some tissues in FSE images. This work presents a detailed study of the contrast obtained with FSE imaging sequences and examines the image sequence and tissue parameters which influence contrast. The use of multiple refocusing pulses produces several subtle effects not seen in conventional SE imaging sequences, and in this study the precise nature and extent of such effects are described. The relative contributions to image contrast of magnetization transfer, the decoupling of J-modulation effects, the production of stimulated echoes and direct saturation effects, of diffusion and of the effects of the differential attenuation of different spatial frequencies, are each quantified. The mechanisms responsible for the brighter fat signal seen in FSE images, as well as the loss of signal from some other tissues, are explained. Computer simulations, phantom experiments, and clinical images are all used to support the conclusions.

On the relative importance of paramagnetic relaxation and diffusion-mediated susceptibility losses in tissues

Susceptibility agents such as dysprosium may reduce the apparent T2 of a tissue by inducing magnetic field gradients so that diffusion of water molecules causes dephasing of the transverse magnetization. Gadolinium has a susceptibility that is about 30% lower than dysprosium, so that diffusion losses are expected to be only half as big, but it also may produce paramagnetic relaxation by dipolar interactions. The relative importance of these two processes is dependent on several parameters, including the metal concentration, pulse sequence timing, field strength, and the permeability of tissue interfaces to water exchange. The conditions under which exchange-mediated dipolar interactions are less important than diffusion losses have been derived for capillary borne contrast agents in realistic situations.

NMR relaxation of water in hydrogel polymers: a model for tissue

The NMR relaxation rates of a class of hydrated polymers (hydrogels) have been investigated over a wide range of frequencies (0.01 to 60 MHz) and compositions. The gels comprise long chains of polytetramethylene oxide diol crosslinked by copolymers of dimethylacrylamide and methylmethacrylate. The longitudinal relaxation rate dispersion curves of these materials are very similar to those shown by human tissues and they can be altered in flexible fashion by changing the polymer content. By substitution of the water by deuterium oxide, the contribution of intermolecular cross-relaxation effects has been shown to account for two-thirds the total water relaxation rate. With their close similarity to tissue relaxation behavior, hydrogels of differing compositions are particularly well-suited to MRI phantoms and test objects.

Inhibition of carnitine acetyltransferase by metabolites of 4-pentenoic acid

The inhibition of carnitine acetyltransferase (EC 2.3.1.7) by metabolites of 4-pentenoic acid was studied. 3-Keto-4-pentenoyl-CoA, a beta-oxidation metabolite of 4-pentenoic acid, was found to be an effective inhibitor of the enzyme in the presence, but not in the absence of L-carnitine. Since acetyl-CoA protects the enzyme against this inhibition, 3-keto-4-pentenoyl-CoA seems to be an active site-directed inhibitor. 3-Keto-4-pentenoyl-CoA, which is a substrate of carnitine acetyltransferase, causes the irreversible inactivation of the enzyme. All observations together lead to the suggestion that 3-keto-4-pentenoyl-CoA is a mechanism-based inhibitor of carnitine acetyltransferase.