Regeneration of endothelial cells after balloon denudation of the rabbit carotid artery and changes in responsiveness

The present experiments were carried out to determine the regrowth of endothelial cells (EC) after balloon denudation of the rabbit carotid artery and the changes in responsiveness of the artery with regenerated EC. Scanning electron microscopic findings revealed that 28.8% of the luminal surface was covered with regenerated EC at week 1. The regrowth of EC proceeded progressively, and a full lining was achieved at week 6. Regenerated EC were morphologically different from native ones; they were elongated (weeks 1 and 2) and irregularly oriented (weeks 4 and 6), and their numbers had significantly increased. Light microscopy revealed the intimal thickening and proliferation of smooth muscle cells. No accumulation of lipids in the vascular wall could be detected at any observation time. The experiments in an organ bath demonstrated that the altered appearance of EC was accompanied by depressed endothelium-dependent relaxations to acetylcholine, ADP and A23187. However, sodium nitroprusside-induced relaxation and contractile responses to noradrenaline, serotonin and histamine remained unchanged in the normal and denuded preparations, indicating that the dysfunction of the endothelium occurs at a time when the ability of the underlying vascular smooth muscle to relax or contract was unchanged. In addition, it is suggested that the impairment of the endothelium-dependent relaxation may be partly due to impairment of the synthesis and/or release of endothelium-derived relaxing factor(s) in EC.     

Effects of arginine derivatives on soluble guanylate cyclase from neuroblastoma N1E 115 cells

The effects of L-arginine (Arg) derivatives on soluble guanylate cyclase from neuroblastoma N1E 115 cells were examined. The Arg derivatives were modified at the -NH2, -COOH, C alpha-proton or guanidino group of Arg. Among the synthesized derivatives, eight compounds, i.e. the 5-(dimethylamino)-1-naphthalenesulfonyl (DNS) ones, especially N-cyclohexyl-2-(N-DNSamino)-5-guanidino-2-methylvaleramide and 1-[2-(N-DNSamino)-2-(2-imino-1,2,3,4,5,6-hexahydropyrimidin- 4-yl)acetyl]- piperidine, were found to inhibit the activity of crude guanylate cyclase in the 105,000 g supernatant fraction of the cell homogenate. The enzyme, partially purified by a column of Chelex 100 Na+, was also inhibited by these eight compounds. The mode of the inhibition was competitive. The Ki values were in the range of 2-8 microM for the enzyme in the 105,000 g supernatant fraction and 3-16 microM for the partially purified enzyme, in the presence of Mg2+ as a metal cofactor. In contrast, a new derivative, methyl 2-amino-5-guanidinovalerate (M Arg ME), as well as the Arg methyl ester (Arg ME) and Arg; were found to enhance the activity of the partially purified guanylate cyclase; KA values of M Arg ME, Arg ME and Arg were approximately 9, 4 and 3 microM respectively. From these results, the free guanidino group including 2-imino-1,2,3,4,5,6-hexahydropyrimidin-4-yl or 2-imino-1,2,3,4,5,6-hexahydropyrimidin-5-yl and modification of the --NH2 residue with a hydrophobic group such as DNS seemed to be essential for inhibition of the guanylate cyclase; however, the guanidino and --NH2 residue of Arg should be free for activation by these Arg derivatives.     

Ester prodrugs of zidovudine

Ten novel ester prodrugs of zidovudine (azidothymidine; AZT) were synthesized with aliphatic acids (acetic-stearic), and the enzymatic regeneration of AZT from the prodrugs was investigated both in vitro and in vivo. The enzymatic hydrolysis rates of the AZT esters in the presence of mouse enzyme systems (plasma, liver, and intestine, and kidney) were highly dependent on the lengths of the acyl chains of the prodrugs. The caprate or caprylate of AZT showed the highest reactivity to three of the four enzyme systems; either the decrease or the increase in the acyl chain length resulted in the decrease of the reactivity to the enzymes. Zidovudine (AZT) and three of the prodrugs (acetate, caprate, and stearate) were administered to mice intraperitoneally, and the plasma concentrations of AZT and a corresponding prodrug were measured. The AZT concentrations in plasma following the acetate administration rapidly decreased with a half-life of 14.5 min. This tendency is similar to that shown in direct AZT administration. On the other hand, the concentrations following the caprate or stearate administration decreased slowly and were maintained for as long as 4 h after dosing. The prodrug concentrations in plasma after the prodrug administration were under the detection limit (0.01 micrograms/mL), except for acetate. The absence of the caprate and stearate in plasma may be attributed to the high hydrophobicity or favorable tissue distribution of the ester derivatives.     

Continuous lumbar subarachnoid pressure monitoring as an indicator of shunt operation for so-called normal pressure hydrocephalus

Lumbar subarachnoid pressure (LSP) was continuously monitored via intrathecally introduced polyethylene catheter to select the patients for shunt operation. A total of seventy cases included so-called normal pressure hydrocephalus (NPH) secondary to subarachnoid hemorrhage (SAH; 34 cases), idiopathic NPH (17 cases), secondary NPH whose symptoms developed after operations for brain tumors, head injuries or meningitis (12 cases) and other intracranial diseases including pseudotumor cerebri or meningeal carcinomatosis, etc. (7 cases). Shunt operation was effective in 36 cases and not effective in 9 cases, while 25 cases were not shunted since LSP was not elevated or clinical manifestations were slight. Mean values of baseline pressure and maximum pressure in shunt effective group, shunt non-effective group and non-shunted group were 14.5, 12.7, 9.0 and 29.9, 25.0, 17.9 mmHg, respectively. Statistical difference was observed between shunt effective group and non-shunted group. Frequency of pressure waves was also significantly higher in shunt effective group than in non-shunted group. Above all, measurement of LSP was regarded as useful in idiopathic NPH. However, preoperative clinical symptoms had a closer relationship to shunt response than results of LSP in post SAH patients. Complication related to this monitoring was negligible except in one case of meningitis which was easily treated by administration of antibiotics. Follow-up study also justified our selection since no further deterioration was noted in non-shunted group. The present study indicates that measurement of LSP would be useful in selecting the patients who will benefit from shunting and in eliminating unnecessary shunt operations because this simple method is easily performed at bed side without perforating the skull.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of macrophage and smooth muscle cell apoptosis in association with oxidized low-density lipoprotein in the atherosclerotic development.

To examine the role of the apoptosis of macrophages and smooth muscle cells in the development of atherosclerosis, human aortic tissues with intimal lesions were immunostained with antibodies against terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-biotin nick end labeling (TUNEL), single-stranded DNA (clone F7-26), and active caspase-3. Apoptotic cells were detected in the intima using both TUNEL and single-stranded DNA, however, the latter method was the more sensitive one for detecting apoptotic cells in the early stages of atherosclerosis. The number of apoptotic cells increased as the disease progressed. It implies that the apoptosis of intimal cells is involved in the formation of atherosclerotic lesions. In addition, quantitative analyses of the cell types undergoing apoptosis using double-immunostaining revealed that the susceptibility of macrophages and smooth muscle cells to apoptosis was greater specifically in atheroma than in the other atherosclerotic lesions, and macrophages were more susceptible to apoptosis than smooth muscle cells. The frequency and spatial distribution of oxidized low-density lipoprotein (oxLDL) (FOH1a/DLH3)-positive cells were examined by immunohistochemistry, and the results resembled those of apoptotic cells. The number of oxLDL-positive cells in the intima significantly correlated with the susceptibility of smooth muscle cells, but not with that of macrophages, to apoptosis. These results suggest that oxLDL affects the apoptosis of smooth muscle cells during the atherosclerotic development.     

Quadro-pulse stimulation is more effective than paired-pulse stimulation for plasticity induction of the human motor cortex

OBJECTIVE: Repetitive paired-pulse transcranial magnetic stimulation (TMS) at I-wave periodicity has been shown to induce a motor-evoked potential (MEP) facilitation. We hypothesized that a greater enhancement of motor cortical excitability is provoked by increasing the number of pulses per train beyond those by paired-pulse stimulation (PPS). METHODS: We explored motor cortical excitability changes induced by repetitive application of trains of four monophasic magnetic pulses (quadro-pulse stimulation: QPS) at 1.5-ms intervals, repeated every 5s over the motor cortex projecting to the hand muscles. The aftereffects of QPS were evaluated with MEPs to a single-pulse TMS, motor threshold (MT), and responses to brain-stem stimulation. These effects were compared to those after PPS. To evaluate the QPS safety, we also studied the spread of excitation and after discharge using surface electromyograms (EMGs) of hand and arm muscles. RESULTS: Sizes of MEPs from the hand muscle were enhanced for longer than 75min after QPS; they reverted to the baseline at 90min. Responses to brain-stem stimulation from the hand muscle and cortical MEPs from the forearm muscle were unchanged after QPS over the hand motor area. MT was unaffected by QPS. No spreads of excitation were detected after QPS. The appearance rate of after discharges during QPS was not different from that during sham stimulation. CONCLUSIONS: Results show that QPS can safely induce long-lasting, topographically specific enhancement of motor cortical excitability. SIGNIFICANCE: QPS is more effective than PPS for inducing motor cortical plasticity.