Comparison of fresh tissue incubation assay and the in vivo localization of monoclonal antibodies to renal cell carcinoma

Few in vitro tests currently available are able to accurately predict the in vivo localization of monoclonal antibodies (Mabs) to cancer. We report on a fresh tissue incubation assay (FTIA) and compare the results of this assay to the in vivo localization of renal cell carcinoma (RCC)-reactive Mab A6H and control Mab AFP-22 to RCC and non-RCC xenografts implanted in nude mice. Both the FTIA and in vivo localization study demonstrated highly selective uptake of A6H in RCC but not in non-RCC xenografts. Radioimmunoscintigraphy using A6H clearly visualized RCC xenografts in every attempt, while AFP-22 did not highlight any of the tumor xenografts. The results demonstrate that FTIA may be a useful in vitro assay for selecting Mabs for in vivo application, and that radioimmunoscintigraphy is a potentially useful tool in detecting cancer sites.     

Microsurgical unilateral approaches for spinal tumour surgery: Eight years' experience in 256 primary operated patients

Summary A series of 256 consecutive patients suffering from spinal tumours was studied with respect to the value of bilateral or unilateral surgical approaches. The case material included 152 extradural, 87 intradural, extramedullary and 17 intramedullary tumours. The cervical spinal cord was involved in 43, the thoracic in 152 and the lumbosacral region in 61 cases. Hemilaminectomy was chosen mainly for juxtamedullary tumours, while laminectomy was used for intramedullary tumours. No remarkable difference regarding the choice of approaches was found in extradural tumours. More than 60% of cervical or lumbosacral tumours were managed using unilateral procedures. A higher rate of surgical radicality but fewer complications, shorter stay in hospital and better early results were achieved using hemilaminectomy especially in patients with juxtamedullary tumours. From the observations it may be concluded that the results do not depend on the type of surgical approach but are closely related to the histology and location of tumours. Under the prerequisite of exact pre-operative definition of tumour location, unilateral approaches are advantageous for all kinds of spinal tumours especially for juxtamedullary benign tumours.     

Effects of glucose on neuroblastoma in vitro and in vivo

Because neuroblastoma cells in vitro are sensitive to changes in glucose levels in growth media, the effects of glucose levels and dietary carbohydrate on the sensitivity of neuroblastoma cells to chemotherapy were studied. In vitro, 20 microM bromoacetylcholine, 3mM 1,3-diaminopropane, and 5 mM 5-fluorouracil were added to the growth medium of strain N2a neuroblastoma cells cultured in Dulbecco's modified Eagle medium with high glucose (4.5 g/L, HG), normal glucose (1.0 g/L, NG), or low glucose (0.1 g/L, LG). Diaminopropane and 5-fluorouracil had some cytotoxic effect on cells in all media. Bromoacetylcholine killed cells in all media, but at a concentration of 20 microM was most effective in LG medium. Mice (A/Jax) were inoculated with neuroblastoma cells for in vivo studies. Mice could not tolerate a carbohydrate-free diet, while a high-carbohydrate diet caused no change in survival time. When mice on a high carbohydrate diet were treated with cyclophosphamide (100 mg/kg, ip) or 5-fluorouracil (125 mg/kg, ip) they died faster than drug-treated mice on a normal diet. Oral chlorpropamide or cimetidine did not prolong survival time. Analysis of blood glucose levels showed neuroblastoma significantly lowered blood glucose levels (p less than 0.05), while chlorpropamide had no significant effect. It is proposed that manipulation of plasma glucose to lower levels will not be effective in enhancing the chemotherapy of neuroblastoma.     

Electropharmacologic characteristics of ventricular proarrhythmia induced by ibutilide.

The purpose of this study was to evaluate in vivo the proarrhythmic effects of ibutilide in dogs with or without ventricular hypertrophy. Fourteen dogs received repeated experiments both during the acute and chronic phases (8 weeks, with ventricular hypertrophy) of complete atrioventricular (AV) block. Twelve-lead ECG, monophasic action potentials in the left and right ventricle were recorded before and after each dose of ibutilide (0.01-0.08 mg/kg) during different ventricular rates. In these dogs, ibutilide increased QT interval, biventricular APD90, interventricular deltaAPD90 (difference between the left and right ventricular APD90), and QT dispersion, and induced early afterdepolarizations in a dose-dependent manner. The interventricular deltaAPD90, QT dispersion, and increases of QT interval were more pronounced during slower ventricular rates. There were greater QT interval, biventricular APD90 interventricular deltaAPD90, and QT dispersion values during chronic AV block than during acute AV block. Moreover, ibutilide can induce higher incidences of early afterdepolarizations and torsades de pointes [six (43%) of 14 versus 0 of 14; p < 0.05] during chronic AV block than during acute AV block. In conclusion, ibutilide can prolong ventricular repolarization and increase dispersion of ventricular repolarization in a dose-dependent and reverse rate-dependent manner. The high incidence of torsades de pointes in the dogs during chronic AV block suggests the importance of ventricular hypertrophy in the occurrence of ibutilide-induced proarrhythmia.     

Antiviral tannins from two Phyllanthus species

Seven ellagitannins isolated from Phyllanthus myrtifolius and P. urinaria (Euphorbiaceae) have been shown, for the first time, to be active against Epstein-Barr virus DNA polymerase (EBV-DP) at the microM level. All these compounds have the same moiety of a corilagin, and differ from each other by different substitutions at C-2 and C-4 of the glucose core. SAR analysis and molecular modeling reveal that the essential pharmacophore of these tannins resides in the corilagin moiety. The outer complex carboxylic acid moieties appear to act only as auxopharmacore.     

DT-diaphorase protects against menadione-induced oxidative stress

To study the role of DT-diaphorase in menadione-mediated cytotoxicity, menadione-resistant cells were selected from P19 cells by stepwise increasing concentrations of menadione from 10 to 60, 120 or 300 microM without mutagenic pretreatment. Three isolated clones, K60, K120 and K300, were maintained in media containing 60, 120 or 300 microM menadione, respectively. The resistance of these cells to menadione, in order, was: K300 > K120 > K60 > P19 cells. K300 cells were the most resistant. Acquisition of resistance was associated with elevation in DT-diaphorase activity. Pretreatment of the resistant cells with 30 microM dicumarol at 37 degrees C for 30 min sensitized the resistant cells to menadione. When the resistant cells were maintained in the absence of menadione for 28 days, the resistance of K60 and K120 cells was lost. The lower degree of resistance was accompanied by a decrease in DT-diaphorase activity in the revertant cells. However, the resistance and the activity of DT-diaphorase in K300 cells were quite stable in the same period. These results support strongly that DT-diaphorase protects against menadione-induced oxidative stress.     

Phe1psi(CH2-NH)Gly2]nociceptin-(1 - 13)-NH2 activation of an inward rectifier as a partial agonist of ORL1 receptors in rat periaqueductal gray.

1. [Phe1psi(CH2-NH)Gly2]nociceptin-(1 - 13)-NH2 (Phepsi), a tridecapeptide analogue of orphanin FQ/nociceptin (OFQ/N), was introduced as a competitive antagonist of opioid receptor-like orphan receptor (ORL1) in guinea-pig ileum and mouse vas deferens preparations in vitro but was recently found to act as an agonist in vivo. 2. In the periaqueductal gray, a site enriched with both OFQ/N and ORL1 and involved in OFQ/N-induced hyperalgesia and anti-analgesia, the effects of Phepsi and OFQ/N on the membrane current were studied using whole cell patch clamp recording technique in rat brain slices. 3. OFQ/N (0.01 - 1 microM) activated an inwardly rectifying type of K+ channels in ventrolateral neurons of PAG. Phepsi (0.03 - 1 microM), like OFQ/N, also activated this inward rectifier but had only 30% efficacy of OFQ/N. 4 At maximal effective concentration (1 microM), Phepsi reversed the increment of K+ conductance induced by OFQ/N (300 nM) by 46%. On the other hand, Phepsi also prevented the effect of OFQ/N if pretreated before OFQ/N. 5 It is suggested that Phepsi acts as a partial agonist of ORL1 that mediates the activation of inwardly rectifying K+ channels in ventrolateral neurons of rat periaqueductal gray.     

The phenomenon and cause of the dose-dependent oral absorption of chlorothiazide in rats: extrapolation to human data based on the body surface area concept

The reported incomplete and dose-dependent absorption of chlorothiazide in humans was demonstrated in six rats after five oral solutions at doses of 0.93, 2.55, 9.23, 25.6, and 70.2 mg/kg. Mean 48-hr urinary recoveries of intact drug were 57.3, 50.4, 36.7, 22.8, and 15.3%, respectively. A similar degree of dose dependency in absorption was found in rat, dog, and human when the doses were related to unit body surface area (BSA) but not on unit body weight, indicating similar interspecies absorptive capacity in terms of unit BSA. This finding may be partly rationalized by marked similarities in the reported solution transit time (2-3 hr) in the small intestine as well as in the calculated gross surface area of the small intestine per unit BSA (0.163 for rat and 0.132 for human). Contrary to the previous postulation of a specific absorption site, the drug was absorbed from different regions of the GI tract with apparent 1-hr absorption rates, studied by the in situ closed-loop method, in the following rank order: jejunum (34.6%) greater than duodenum (32.7%) greater than large intestine (20.1%) greater than ileum (18.0%) greater than stomach (12.4%). Different from the commonly assumed first-order absorption process, the intestinal loop absorption was concentration-dependent, suggesting a saturable mechanism. For example, the absorption rate at 0.008 mg/mL was higher than that at 0.2 mg/mL in ileal loops (61%, p less than 0.01) and jejunal loops (22%, p less than 0.1). In addition, the absorption rates at pH 6 and 7.4 were statistically identical, indicating a lack of ionization effect that is important in the passive absorption process. The solubility-limited absorption could probably be ruled out at doses below 2.55 mg/kg for rat and 125 mg for human in view of higher aqueous solubilities at 37 degrees C (e.g., 1.3 mg/mL at pH 7) found in the present study. Contrary to the previous hypothesis of low membrane permeability as a limiting factor for absorption, the "intrinsic" partition coefficient in 1-octanol/aqueous buffer was moderate, 0.6. Furthermore, the absorption in ileal and jejunal loops was enhanced by an apparent increase in mesenteric blood flow by caffeine. The existence of prolonged oral absorption in rats and humans is discussed.     

Immunotherapy for renal cell carcinoma: recent results

Summary Advanced renal cell carcinoma (RCC) is refractory to all traditional therapies and has been the subject of intense investigation using newer therapeutic modalities, including monoclonal antibodies, lymphokine-activated killer cells and vaccines. We review these newer immunotherapies and summarize our results with radioimmune imaging and radioimmunotherapy using mouse xenografts of human RCC and one of our RCC-preferential monoclonal antibodies (A6H). We have consistently been able to image RCC xenografts without background subtraction. Radioimmunotherapy caused tumor shrinkage, and dosimetry results were consistent with xenograft cure. Phase I clinical trials are now underway at this institution.     

Compartment- and model-independent linear plateau principle of drugs during a constant-rate absorption or intravenous infusion

A simple general equation is derived to show the linear plateau principle under various conditions during or after a constant or changing rate of absorption or intravenous infusion. The time required to cause a certain fraction (f_t) of the total shift or change between the two steady-state plasma concentrations is equal to the time required for the cumulative (from time zero) plasma area, AUC_0t, to reach the same fraction of AUC₀ assumed to be obtained after an instantaneousintravenous dosing. The role of the terminal biological half-life and the importance of the earlydistribution phase and its exponential half-life or lives in the plateau principle are discussed.Clinical implications and applications to multiple dosage regimens are also discussed.