Microfilament depletion and circumvention of multiple drug resistance by sphinxolides

Sphinxolides, a newly described family of cytotoxins from the New Caledonian sponge Neosiphonia superstes, bear structural resemblance to scytophycins. We now demonstrate that the cytotoxicity of sphinxolides is associated with cell cycle arrest in G2-M and induction of apoptosis. Like scytophycins and cytochalasins, sphinxolides caused rapid loss of microfilaments in cultured cells, without affecting microtubule organization. Microfilament reassembly was very slow after removal of the sphinxolide, consistent with the slow recovery of cellular proliferation. Sphinxolides potently inhibited actin polymerization in vitro and the microfilament-dependent ATPase activity of purified actomyosin, indicating a direct effect on actin. Importantly, sphinxolides were equally cytotoxic toward MCF-7 human breast carcinoma cells and a subline which overexpresses P-glycoprotein (MCF-7/ADR). Similarly, overexpression of the multidrug resistance-associated protein MRP by HL-60 cells did not confer resistance to the sphinxolides. These studies demonstrate that sphinxolides are potent new antimicrofilament compounds that circumvent multidrug resistance mediated by overexpression of either P-glycoprotein or MRP. Therefore, these agents may be useful in the treatment of drug-resistant tumors.

The expression of creatine kinase isoenzymes in neocortex of patients with neurodegenerative disorders: Alzheimer's and Pick's disease

Creatine kinase (CK) activity was found decreased in the brains of patients with Alzheimer's disease (AD) and Pick's disease (PD). However, the decrease of total CK activity in AD was more pronounced than in PD. Analysis of the activity of two CK isoforms, BCK and ubiquitous mitochondrial CK, demonstrated that the decrease of total CK activity in AD and PD was related to the decrease of BCK activity. The decline of CK activity both in AD and PD correlated well with the decline of the content of immunoreactive BCK in brain extracts. The BCK mRNA level in AD and PD was not significantly different from control patients and could not be the primary reason for decreases in CK content and activity. The decreased level of BCK in AD and PD brains might be caused by posttranscriptional events, which could affect the translation of BCK mRNA and/or lead to the inactivation and degradation of the enzyme. Because CK is sensitive to oxidative modification, it is possible that the changes observed in this study result from free radical damage.

Preliminary crystallographic study on a low molecular weight form of bacterial plasminogen activator staphylokinase

Staphylokinase, a 17 kDa protein, produced by certain strains of Staphylococcus aureus functions as a fibrin-specific plasminogen activator. During its interaction with plasminogen, staphylokinase is converted into a low molecular weight form by loss of ten amino-terminal residues. This low molecular weight form of recombinant staphylokinase has been crystallized using the hanging-drop vapor-diffusion technique with polyethylene glycol 4000 as precipitant. Crystals belong to the orthorhombic space group C222(1) with unit-cell dimensions a = 43.78, b = 59.86 and c = 103.25 A and one molecule in the asymmetric unit. These crystals diffract to about 2.4 A resolution.

Crystallization and preliminary cryogenic X-ray diffraction analyses of protein L-isoaspartyl O-methyltransferase from human fetal brain

Recombinant human fetal brain protein L-isoaspartyl O-methyltransferase, EC 2.1.1.77, was crystallized in PEG 8000 with adenosine homocysteine by a macroseeding technique. The space group was P2(1) with a = 47.4 A, b = 53.9 A, c = 48.7 A and beta = 116.4 degrees for cryofrozen crystals at 90 K. The crystals diffracted to 2.1 A and have one molecule per asymmetric unit.

Save the child's esophagus, Part II: Colic patch repair

PURPOSE

In a previous report, the authors documented the procedures necessary to regain esophageal continuity in infants who had massive disruption of the suture line following esophagoplasty. As a corollary, this study shows the feasibility of preserving the esophagus in older children by using an esophageal patch.

METHODS

Fifteen children ranging in age from 8 months to 16 years at the time of surgery had repair of esophageal strictures or tracheoesophageal fistulae by the use of a vascularized patch rather than esophageal resection and interposition with colon or stomach. The technique of "colonic-patch oesophagoplasty" was described by Hecker and Hollman in 1975. From 1976 to 1995, the authors have used a modification of their procedure in 14 children, and in one patient an intercostal muscle flap was interposed. The technique consists of esophagotomy through the area of stricture with application of a vascularized patch of colon to the resulting defect.

RESULTS

Ten of the patients were boys and four were girls with an additional girl considered for the procedure at 8 months of age. However, during surgery, an intercostal muscle flap interposition was used. Eight children had esophageal stricture caused by lye ingestion; two from anastomotic stricture; two from gastroesophageal reflux; two from recurrent tracheoesophageal fistula; and one from long-term nasogastric intubation. Follow-up showed excellent results in nine patients who had the colic patch operation. All had good swallowing. A tenth patient, the child with the vascularized intercostal muscle flap, is currently eating a regular diet but it has only been 4 months since the operation. However, one of these excellent patients continues to have a small focus of Barrett's esophagus and another one was killed in an automobile accident one year after operation. Three children have good results but with occasional difficulty in swallowing boluses of meat or with continuing reflux. Two patients had poor results and both have undergone reoperation. In one of these children with Down's syndrome and diabetes, the colic patch worked well for 6 years but because of continuing reflux, distal esophageal scarring and obstruction eventually ensued. After reoperation for distal esophageal resection and colic interposition, the patient died of pulmonary failure. The second child with poor results has recently undergone reoperation to extend the esophagotomy through the distal scarred esophagus and to revise the colic patch.

CONCLUSION

The use of a vascular colic patch for treatment of severe esophageal strictures is a viable alternative to esophageal resection and interposition. However, patients with continuing reflux or Barrett's esophagus, or both, may progress with distal esophageal scarring and obstruction and subsequent dilation of the patch. Those patients will require reoperation.

Laparoscopic splenectomy by the lateral approach: a safe and effective alternative to open splenectomy for hematologic diseases

BACKGROUND

The purpose of this study was to compare the clinical outcomes and expense of laparoscopic splenectomy by the lateral approach with open splenectomy for the treatment of hematologic diseases.

METHODS

Medical records of 20 matched patients undergoing open splenectomy and lateral approach laparoscopic splenectomy were retrospectively reviewed detailing perioperative course, clinical outcome, and hospital charges.

RESULTS

Patients undergoing laparoscopic splenectomy (n = 10) experienced longer anesthesia (324 versus 176 minutes; p < 0.05) and operative times (261 versus 131 minutes; p < 0.05) than those undergoing open splenectomy (n = 10). No difference was noted in both intraoperative and postoperative packed red blood cells transfused. Laparoscopic splenectomy resulted in a shorter duration of nasogastric decompression (1.2 versus 2.6 days), more rapid resumption of normal oral intake (1.9 versus 4.4 days), and earlier hospital dismissal (3.0 versus 5.8 days). Although hospital charges were not significantly higher in the laparoscopic group ($17,071.00 versus $13,196.00; p > 0.05), operative charges were always significantly higher.

CONCLUSIONS

When compared with open splenectomy, lateral approach laparoscopic splenectomy allows a more rapid return of normal gastrointestinal function and shorter hospital stay. The operative expense of laparoscopic splenectomy is significantly higher; however, the overall hospital expense is not. If costs can be decreased, the lateral approach laparoscopic splenectomy will be the preferred operative approach.

Magnetic resonance imaging of the brain in Aicardi's syndrome. Report of 20 patients

Aicardi's syndrome consists of multiple anomalies of the eye, brain, and axial skeleton in females, and is associated with early-onset infantile spasms and severe developmental delay. For the present study, magnetic resonance images of 20 patients with Aicardi's syndrome were obtained and the neuroimaging findings catalogued. These were compared to previously reported results and the findings correlated with current theories of fetal brain development. The results revealed a high frequency of cortical migration defects (94%) and a wide variability in the callosal defect, migrational abnormalities, and other findings in Aicardi's syndrome.

Renal apoptosis and clusterin following ureteral obstruction: the role of maturation

PURPOSE

Unilateral ureteral obstruction (UUO) increases renal apoptosis as well as clusterin, which in turn is modulated by angiotensin II. The present study was designed to investigate the role of maturation in these responses.

MATERIALS AND METHODS

Neonatal and adult Sprague-Dawley rats underwent UUO or sham operation. Fourteen days later, renal apoptosis was quantitated by flow cytometry, and renal messenger RNA (mRNA) was quantitated for renin and clusterin. Apoptotic cells, macrophages, clusterin and Dolichos biflorus agglutinin were localized by immunohistochemistry.

RESULTS

Following ipsilateral UUO, renal DNA content increased in the adult but decreased in the neonate. Renal macrophage infiltration induced by UUO was 2-fold greater in adults than in neonates, while distal tubular apoptosis was 2-fold greater in neonatal than in adult kidneys. Unilateral ureteral obstruction markedly increased renal renin mRNA expression in the neonate, but not in the adult, while clusterin expression was greater in adults than in neonates. Clusterin was localized to some, but not all, distal tubules containing apoptotic cells.

CONCLUSIONS

We conclude that, compared with the adult, UUO in the neonate induces greater apoptosis, which in turn contributes to reduced renal DNA. This may be modulated by relative suppression of clusterin in the obstructed neonatal kidney due to greater activation of the renin-angiotensin system.

Multi-organ erythrocyte sequestration and ligand expression in rhesus monkeys infected with Plasmodium coatneyi malaria

The pathogenesis of human cerebral malaria is suspected to be caused by blockage of cerebral microvessels by the sequestration of parasitized human red blood cells (PRBC). Examination of infected tissues indicate PRBC sequestration in microvessels is the result of PRBC knob attachment to endothelial cell surface cytoadherence receptors such as CD36, thrombospondin (TSP), and intercellular adhesion molecule-1 (ICAM-1). In lieu of fresh human tissue, several animal models for human cerebral malaria have been developed, the Plasmodium coatneyi-infected rhesus monkey model being the most versatile. To further the understanding of noncerebral malarial complications during disease, we examined noncerebral tissues of infected rhesus monkeys. Our study demonstrated similar microvessel PRBC sequestration and the presence of cytoadherence ligands in noncerebral tissues. Immunohistochemical analysis showed CD36, TSP, and ICAM-1 cytoadherence proteins in several major organs.

MHC studies of the primary antiphospholipid antibody syndrome and of antiphospholipid antibodies in systemic lupus erythematosus

OBJECTIVE

To study the association of HLA Class I, II, and III alleles with antiphospholipid antibodies, both in patients with systemic lupus erythematosus (SLE) and patients with primary antiphospholipid antibody syndrome (APS).

METHODS

We studied Caucasian patients with SLE (n = 91) and with primary APS (n = 16) followed at the Ottawa General Hospital Rheumatic Disease Unit. Antiphospholipid antibodies (aPL) were defined by a positive IgG anticardiolipin antibody by serum ELISA and/or the presence of a lupus anticoagulant. HLA Class I by serology and Class II by restriction fragment length polymorphism were compared in patients with and without serum aPL, and in patients with primary APS compared to controls. C4A null alleles were studied in patients with primary APS.

RESULTS

aPL were found in 19 of 91 (21%) patients with SLE, and were associated with deep venous thrombosis in this group. In patients with primary APS, stroke, deep vein thrombosis, and recurrent fetal loss were the most common clinical features. HLA-DR17(3) and Dw24 were decreased in patients with SLE with aPL and in patients with primary APS. HLA-DR4 and the linked DR53 were significantly increased in patients with primary APS compared to patients with SLE. In patients with aPL (SLE and primary APS) compared to patients with SLE without aPL, associations were found with HLA-DR53 (p = 1.5 x 10(-4), RR 5.1), DR7 (p = 0.01, RR 5.6), and to a slightly lesser degree DQ7 (p = 0.005, RR 3.6). C4A null alleles by protein allotyping and the C4A gene deletion were not associated with primary APS.

CONCLUSION

We confirm the association of aPL with HLA Class II alleles. The strongest association with aPL in our study is with the HLA-DR53 haplotypes, some of which include the DQ7 allele, as suggested in an earlier study. The HLA-B8, DR17, DQ2 haplotype so closely associated with SLE is significantly decreased in both patients with aPL and with primary APS. C4A null alleles are not associated with primary APS in this population. Our study suggests the aPL response in SLE and primary APS is immunogenetically distinct from SLE itself.

Dendroamides, new cyclic hexapeptides from a blue-green alga. Multidrug-resistance reversing activity of dendroamide A

Dendroamide A (1), one of three new bistratamide-type cyclic hexapeptides from the terrestrial blue-green alga (cyanobacterium) Stigonema dendroideum Fremy, exhibits multidrug-resistance reversing activity. The gross structures of the three compounds, dendroamides A-C, were determined by NMR and mass spectral analyses. Their absolute stereochemistries were determined by Marfey and chiral GC/MS analyses of derivatives formed from acid hydrolysis of the intact and ozonized peptides.

Credentialing of research surgeons: can computers help in the process?

There has been recurring debate regarding the need for a process of ensuring that individuals who propose research using live animals will be competent in the research and compassionate in their care of animals. The mechanism by which this goal can be accomplished is presently under consideration and acceptance by investigators is of concern. As a first step, the authors propose utilization of an interactive computer program that not only would evaluate cognitive knowledge but also would instruct in areas found to be deficient. Immediate feedback with educational reinforcement is possible. The authors' interest in such a program began with a pediatric surgical postgraduate course presented in 1994 at the Clinical Congress of the American College of Surgeons. The computer program utilized was IRIS (Instantaneous Response Interactive System: IRIS, Denver, CO, USA). This system was well suited to evaluation and instantaneous feedback. That program, or one like it, would be suited to initial evaluation and education of researchers. The important aspect is interaction and immediate feedback. This article also includes the results of a panel discussion at the annual meeting of the Academy of Surgical Research in Albuquerque, New Mexico.

Aortoesophageal fistula and double aortic arch: two important points in management

Two children with double aortic arch and aortoesophageal fistula (AEF) are reported to warn of this lethal complication of double aortic arch and to stress important points in the diagnosis and management. A review of the records of 30 children with double aortic arch disclosed two patients who had AEF. The first patient had respiratory distress and repair of a vascular ring (double aortic arch) at 5 weeks of age. At 9 weeks of age, because of difficulty with tracheal extubation, aortopexy was performed. Ten days later, profuse upper gastrointestinal bleeding required control by a Sengstaken-Blakemore (SB) tube. Thoracotomy and repair AEF was accomplished successfully under cardiopulmonary bypass. The second patient had hepatomegaly and Pseudomonas sepsis. Endotracheal and nasogastric intubation was necessary, and subsequently the double aortic arch was demonstrated by magnetic resonance imaging (MRI). On the 48th day of hospitalization, life-threatening upper gastrointestinal hemorrhage required insertion of an SB tube. Cardiopulmonary bypass allowed successful repair of the AEF. Both children are alive, after 3 and 2 years (respectively). These patients demonstrate that AEF must be diagnosed clinically (no imaging technique is effective); its history and physical presentation are typical. The SB tube is effective for controlling the hemorrhage until cardiopulmonary bypass can be performed to allow repair.

Ethical theories and principles

Ethically sensitive situations and issues are not new in today's health care practice. They are increasing in frequency and complexity. For practitioners to face these challenges, they must not only understand their own values and beliefs, but understand the tools available to resolve these ethical dilemmas when they arise. Ethical theories and principles and decision-making models can assist the practitioner in obtaining resolution.

Esophageal foreign bodies in children: diagnosis, treatment, and complications

OBJECTIVE

We performed this study to identify the role of radiology in the diagnosis, treatment, and complications of esophageal foreign bodies in children.

MATERIALS AND METHODS

We retrospectively reviewed the charts and radiographs of 123 esophageal foreign bodies seen in 118 children at the Medical University of South Carolina from May 1980 through May 1995.

RESULTS

Most foreign bodies were coins in the upper esophagus (69%) in infants less than 2 years old (65%) for fewer than 24 hr (60%). The presenting symptoms varied, with 20% of patients asymptomatic. Respiratory symptoms that mimicked upper respiratory tract infections or croup proved misleading with long-standing foreign body retention. Preexisting esophageal disease was present in 17% of patients. The Foley catheter method of foreign body extraction was attempted in 53 cases (43%) and was successful without complications in 46 (87%). Esophagoscopy was attempted in 72 cases (58%) and was successful without complications in 66 (92%). Three patients had major complications: a fatal aorticoesophageal fistula, an extraluminal migration of a coin, and a large esophageal diverticulum. Significant mucosal erosions were shown in six patients on radiologic studies after extraction.

CONCLUSION

Early recognition and treatment of esophageal foreign bodies is imperative because the complications are serious and can be life-threatening. Radiology plays an important role in the initial diagnosis, in recognition of complications, and in treatment. The Foley catheter method of foreign body extraction can be used on some patients, but esophagoscopy remains the safest method of esophageal foreign body extraction.

Mechanism of action cryptophycin. Interaction with the Vinca alkaloid domain of tubulin

Cryptophycin is a potent antitumor agent that depletes microtubules in intact cells, including cells with the multidrug resistance phenotype. To determine the mechanism of action of cryptophycin, its effects on tubulin function in vitro were analyzed. Cryptophycin reduced the in vitro polymerization of bovine brain microtubules by 50% at a drug:tubulin ratio of 0.1. Cryptophycin did not alter the critical concentration of tubulin required for polymerization, but instead caused substoichiometric reductions in the amount of tubulin that was competent for assembly. Consistent with its persistent effects on intact cells, cryptophycin-treated microtubule protein remained polymerization-defective even after cryptophycin was reduced to sub-inhibitory concentrations. The effects of cryptophycin were not due to denaturation of tubulin and were associated with the accumulation of rings of microtubule protein. The site of cryptophycin interaction with tubulin was examined using functional and competitive binding assays. Cryptophycin blocked the formation of vinblastine-tubulin paracrystals in intact cells and suppressed vinblastine-induced tubulin aggregation in vitro. Cryptophycin inhibited the binding of [3H]vinblastine and the hydrolysis of [gamma32P]GTP by isolated tubulin, but did not block the binding of colchicine. These results indicate that cryptophycin disrupts the Vinca alkaloid site of tubulin; however, the molecular details of this interaction are distinct from those of other antimitotic drugs.

Temperature effects in cyanolysis using elemental sulfur

As part of our studies directed at new treatments for cyanide poisoning we examined the effect of temperature on both the non-catalyzed and the albumin-catalyzed reactions of cyanide with a colloidal suspension of elemental sulfur (CSES). Using saturated sulfur solutions prepared in two solvents, pyridine (PY) and methyl cellosolve (MC), the reactions were studied at 15.0, 25.0, 30.0 and 37.5 degrees C. For all the cyanolysis reactions (non-catalyzed and albumin-catalyzed) there is an enhancement of reaction rate when the organic solvent for the sulfur is MC. Irrespective of the solvent for the CSES, the non-catalyzed reactions gave linear Arrhenius plots (PY, correlation coefficient = 0.998; MC, correlation coefficient = 0.997). In each case the entropy of activation was positive (14.1 cal K-1 mol-1 for PY and 56.4 cal K-1 mol-1 for MC). In contrast with these results the albumin-catalyzed reactions generated non-linear Arrhenius plots and negative entropies of activation. Non-linear plots were observed with the three albumins studied: human serum albumin, heat-shock bovine serum albumin and fatty acid-free bovine serum albumin. The non-linear plots are the result of a more complex reaction sequence than a simple cyanolysis reaction.

Cortical activation in confrontation naming

Functional magnetic resonance imaging was used to detect cortical activation in the right and left perisylvian cortex of seven young adult right-handed volunteers in response to a letter fluency task and to a visual naming task using standardized line drawings. Both letter fluency and visual naming activated left dorsolateral prefrontal cortex (Brodmann's areas 6, 9, 44 and 45). Only visual naming activated area 37 (a cortical region with strong connections to visual association areas), visual association area 19, and areas 39 and 21 previously shown to activate with auditory semantic tasks. This study supports a role for area 37 as participant in a visual lexicosemantic processing network which may otherwise overlap the auditorysemantic network.

Microtubule effects of welwistatin, a cyanobacterial indolinone that circumvents multiple drug resistance

Welwitindolinones are a family of novel alkaloids recently isolated from the blue-green alga Hapalosiphon welwitschii. We demonstrate that incubation of SK-OV-3 human ovarian carcinoma cells and A-10 vascular smooth muscle cells with welwitindolinone C isothiocyanate, now termed welwistatin, results in dose-dependent inhibition of cell proliferation, which is correlated with increases in the percentage of cells in mitosis. Treatment of A-10 cells with welwistatin resulted in reversible depletion of cellular microtubules but did not affect microfilaments. Pretreatment of A-10 cells with paclitaxel prevented microtubule depolymerization in response to welwistatin. Welwistatin inhibited the polymerization of purified tubulin in vitro but did not alter the ability of tubulin to bind [3H]colchicine or to hydrolyze GTP. Also, welwistatin did not induce the formation of topoisomerase/DNA complexes. Results of the present study indicate that welwistatin is a new antimicrotubule compound that circumvents multiple drug resistance and so may be useful in the treatment of drug-resistant tumors.

Quantitative computed tomography and magnetic resonance imaging in aging and Alzheimer's disease. A review

In recent aging research, quantitative techniques have been used to overcome limitations of qualitative interpretation of magnetic resonance and computed tomographic imaging. The purpose of this review is to summarize imaging results emphasizing quantitative studies using these two modalities in human aging. Magnetic resonance spectroscopy is viewed as an extension of imaging, and results of in vivo spectroscopic studies are included. Because Alzheimer's disease (AD) is closely related to aging, a discussion of quantitative imaging techniques that may distinguish normal elderly from patients with AD is included.

Circumvention of P-glycoprotein-mediated multiple drug resistance by phosphorylation modulators is independent of protein kinases

Expression of P-glycoprotein by tumor cells confers resistance to multiple natural product drugs because of its ability to export these compounds. This transporter is a substrate for several protein kinases; however, the functional significance of its phosphorylation is not defined. We examined the effects of many activators and inhibitors of protein kinases on the activity of P-glycoprotein in drug-resistant human breast carcinoma cells (MCF-7/ADR). Several phorbol esters sensitized these cells to P-glycoprotein substrate drugs; however, there was no correlation with activation of protein kinase C. The 4 alpha- and 4 beta-isomers of phorbol 12-myristate 13-acetate were equally potent in sensitizing the cells to actinomycin D and daunomycin and in increasing the intracellular accumulation of [3H]vinblastine. These effects of 4 beta-phorbol myristate acetate required much higher concentrations than were needed to increase P-glycoprotein phosphorylation and were not antagonized by staurosporine. Similar to verapamil, the phorbol esters did not sensitize MCF-7/ADR cells to cisplatin, nor parental MCF-7 cells to any of the anticancer drugs. Mezerein, K-252a, and H-89 sensitized MCF-7/ADR cells, increased intracellular accumulation of [3H]vinblastine, and antagonized photolabeling of P-glycoprotein by [3H]azidopine. Therefore, phosphorylation does not appear to play a significant role in regulating P-glycoprotein activity in MCF-7/ADR cells.

Prosodic characteristics of speech pre- and post-right hemisphere stroke

Case-control studies have shown right hemisphere specialization in the production of intonation in speech. We examined spontaneous prosody in audiotapes of interviews with a 77-year-old right-handed woman recorded 6 months before and 6 weeks after she suffered a stroke affecting the right frontotemporo-parietal regions and the right basal ganglia. Post-stroke, the patient had a normal Mini-Mental Status Examination Score of 29, hemispatial neglect, and impairments in the comprehension of facial expression and prosody. Self-rated mood was within normal limits. We compared beginning, peak, and ending fundamental frequencies (fo) in breath groups, the timing of these fo changes, rate of speech, pause duration, and breath-group duration. We found that post-stroke, the patient had a more restricted fo contour, no changes in the timing of peak fo, an increased rate of speech, less variability in pause duration, and no changes in breath-group duration.

Microtubule-associated protein 2 (MAP-2): a sensitive marker of seizure-related brain damage

We have assessed the efficacy of MAP-2 immunohistochemistry as a marker of seizure-related brain damage and its suitability for quantitation of the damage using densitometric and morphometric image analysis. Seizures were produced in rats by administration of 1.5 LD50 soman, an irreversible AChE inhibitor. Our results demonstrate that neuronal damage, assessed using hematoxylin and eosin, and cresyl violet staining, was colocalized on adjacent serial sections with clearly demarcated reductions in MAP-2 staining. The most severely damaged brain regions were devoid of MAP-2 staining. Reductions in MAP-2 immunostaining were found to be exceptionally well suited for quantitation using densitometric and morphometric image analysis. This study represents the first demonstration of seizure-induced excitotoxic alterations in MAP-2.

Frontal lobe phosphorus metabolism and neuropsychological function in aging and in Alzheimer's disease

31P Magnetic resonance spectroscopy of the frontal lobe was performed in 17 patients with Alzheimer's disease (AD), 8 elderly controls (EC), and 17 young controls (YC). The phosphocreatine/inorganic phosphate (PCr/Pi) ratio in AD (2.32 +/- 0.26 SD) was significantly lower than in EC (2.65 +/- 0.41). In AD patients, a correlation was observed between the PCr/Pi ratio and the dementia rating scale (r = -0.50, p = 0.04). A significant positive correlation between PCr/Pi ratio and age was observed in both AD (r = 0.67, p = 0.003) and YC (r = 0.63, p = 0.006) groups, however, suggesting caution in interpretation of this ratio in AD. We did not find differences between AD, EC, or YC in any other spectroscopic measure. A significant sex difference in the phosphomonoester/phosphodiester ratio (PME/PDE) ratio was observed in AD brain. Females had a lower PME/PDE ratio than males.

Modulation of P-glycoprotein activity by estramustine is limited by binding to plasma proteins

BACKGROUND

Estramustine previously has been shown to interact with P-glycoprotein and to restore intracellular accumulation of vinblastine and paclitaxel in cells overexpressing this drug transporter. However, the ability of estramustine to potentiate the cytotoxicities of several drugs was less than that expected. To resolve this apparent discordance, the authors examined the effects of serum on the actions of estramustine.

METHODS

The cytotoxicities of anticancer drugs with or without estramustine or verapamil toward MCF-7 breast carcinoma cells and a P-glycoprotein-overexpressing subline MCF-7/ADR were determined using the sulforhodamine-binding assay. The extent of intracellular accumulation of [3H]vinblastine and [3H]paclitaxel was determined for each using standard methods, and the binding of radiolabeled drugs to plasma proteins was characterized by equilibrium dialysis.

RESULTS

Without serum, the sensitivities of MCF-7/ADR cells to several P-glycoprotein-transported drugs were increased by estramustine and verapamil. Conversely, when the cells were treated with a 10% serum, the cytotoxicities of these drugs were increased by verapamil, but not by estramustine. Without serum, intracellular accumulation of [3H]vinblastine and [3H]paclitaxel by MCF-7/ADR cells was increased markedly by verapamil and estramustine; however, serum suppressed the effects of estramustine much more strongly than those of verapamil. Equilibrium dialysis experiments demonstrated that [3H]estramustine binds to plasma proteins, predominantly albumin, whereas [3H]paclitaxel binds to albumin and alpha 1-acid-glycoprotein, and [3H]vinblastine binds predominantly to alpha 1-acid-glycoprotein.

CONCLUSION

Although estramustine can bind to P-glycoprotein, its effectiveness as a reversing agent in vivo likely is limited by binding to plasma proteins.

Inhibition of ileal sodium-dependent bile acid transport by 2164U90

Inhibition of the ileal bile acid active transport system, previously shown to be mechanism underlying the hypocholesterolemic activity of 2164U90 in rodents, was further characterized in isolated intestinal preparations from three species. 2164U90 inhibited sodium-dependent transport of taurocholic acid by Caco-2 cells and by monkey and human ileal brush border membrane vesicles in a concentration-dependent manner with IC50s of 7 microM, 5 microM, and 2 microM, respectively. In rat ileal brush border membrane vesicles, 2164U90 was a competitive inhibitor of sodium-dependent taurocholic acid uptake with an estimated Ki of 1.8 +/- 0.2 microM. In anesthetized rats, 5 microM 2164U90 placed in the isolated distal ileum with 3 mM [3H]taurocholic acid decreased ileal uptake, transport into the bile, and transport rate of taurocholic acid by 31-35%. Stereospecificity of inhibition by 2164U90 was demonstrated by the relative inactivity of three other possible stereoisomers in rat ileal sacs and brush border membrane vesicles. 2164U90 did not inhibit sodium-dependent glucose transport by monkey jejunal brush border membrane vesicles, indicating that 2164U90 may be specific for the bile acid transporter. These results suggest that 2164U90 is a potent, selective, stereospecific, competitive inhibitor of the sodium-dependent bile acid transporter in the ileal mucosal cell brush border membrane.

Assessment of primary neuronal culture as a model for soman-induced neurotoxicity and effectiveness of memantine as a neuroprotective drug

An in vitro mammalian model neuronal system to evaluate the intrinsic toxicity of soman and other neurotoxicants as well as the efficacy of potential countermeasures was investigated. The link between soman toxicity, glutamate hyperactivity and neuronal death in the central nervous system was investigated in primary dissociated cell cultures from rat hippocampus and cerebral neocortex. Exposure of cortical or hippocampal neurons to glutamate for 30 min produced neuronal death in almost 80% of the cells examined at 24 h. Hippocampal neurons exposed to soman for 15-120 min at 0.1 microM concentration caused almost complete inhibition (> or = 90%) of acetylcholinesterase but failed to show any evidence of effects on cell viability, indicating a lack of direct cytotoxicity by this agent. Acetylcholine (ACh, 0.1 mM), alone or in combination with soman, did not potentiate glutamate toxicity in hippocampal neurons. Memantine, a drug used for the therapy of Parkinson's disease, spasticity and other brain disorders, significantly protected hippocampal and cortical neurons in culture against glutamate and N-methyl-D-aspartate (NMDA) excitotoxicity. In rats a single dose of memantine (18 mg/kg) administered 1 h prior to a s.c. injection of a 0.9 LD50 dose of soman reduced the severity of convulsions and increased survival. Survival, however, was accompanied by neuronal loss in the frontal cortex, piriform cortex and hippocampus.

Hippocampal volume measurements using magnetic resonance imaging in normal young adults

Volumetric analysis of brain magnetic resonance images (MRIs) measures structural changes associated with neurological and neuropsychiatric disorders. Several studies investigated the hippocampus specifically, reporting degrees of atrophy in such disorders. However, the range of normal hippocampal volumes must be known to assess atrophy. In tracings of T1 oblique slice and three-dimensional MRIs in 24 normal subjects reported here, the average volume of right and left hippocampus was 2.90 cm3 and 2.78 cm3, respectively. On paired analysis, this difference was significant. The literature indicated these volumes are in the middle of a wide range of hippocampal volumes (1.73-5.68 cm3) in both MRI-based and histology-based studies. This wide variation can be explained by differing hippocampal boundary definitions; technical factors of image processing, segmentation, and display; sample heterogeneity; and interoperator differences.

Brain metabolism in hypothyroidism studied with 31P magnetic-resonance spectroscopy

Metabolic consequences of hypothyroidism in adult human brain, despite neuropsychological symptoms, have not been reported. We used 31P nuclear magnetic-resonance spectroscopy of the frontal lobe to examine the effect of acute hypothyroidism on cerebral metabolism. Paired analysis showed that the phosphocreatine/inorganic-phosphate (PCr/Pi) ratio increased from a median of 2.04 (interquartile range 0.15) to 2.22 (0.25) after treatment with levothyroxine (p = 0.01). These reversible alterations in adult cerebral phosphate metabolism during acute hypothyroidism parallel PCr/Pi ratio changes described in skeletal muscle. This is the first direct evidence of cerebral metabolic effects of hypothyroidism on adult brain.

Update on the analysis of the need for pediatric surgeons in the United States

Accurate estimations of pediatric surgical manpower needs are necessary if this specialty is to avoid the consequences of under- or oversupply, and reasonable decisions must be made relative to the number of training programs needed.

METHODS

Fifteen, 10, and 5 years ago, pediatric surgeons (PSs) in 62 standard metropolitan statistical areas (SMSAs) having a population of at least 200,000 were asked to estimate the number of PSs needed in their localities. A computer program analogous to the SOSSUS program was designed to project the number of PSs that would result from various numbers of trainee graduates per year. The program has been updated for comparison. Known input data included the present number and age of PSs, age range of trainees, current US population projections to the year 2025, and the average retirement age.

RESULTS

These PSs estimated that 88 additional PSs are needed in the next 10 years. Currently, 26 programs in the United States graduate an average of 24 trainees per year, and six programs in Canada graduate six trainees per year. The previous projection indicated that 20 trainees per year would result in 525 PSs in 1993, and the actual number is 559; so the figures indicate that 27 or 28 PSs are entering practice each year. The apparent increase in numbers is related to entry of Canadian trainees primarily, and a few others, into practice. The current computer projection indicates that 20 graduate trainees per year would result in an absolute increase of 0.55% per year, and 25 per year would result in an increase of 1.43% per year, to 2020, while the increases in the US population would be 1.02% per year for all ages and 0.52% for 0 to 15 year olds. If all programs currently being considered for approval are certified, as many as 36 trainees per year--or 7 times the rate of the 0-15-year population increase--will result.

CONCLUSION

Although an average of 20 graduates per year entering practice would keep pace with the pediatric population, 25 to 27 graduates per year--or 3.5 to 4 times the rate of the 0- to 15-year population increase--can be accommodated now into the current system of delivery of pediatric surgical care on the basis of estimated need. Many more graduates than this would create an excess of surgeons before long.

Welwitindolinone analogues that reverse P-glycoprotein-mediated multiple drug resistance

Welwitindolinones are a family of novel alkaloids recently isolated from the blue-green alga Hapalosiphon welwitschii as a part of our effort to identify new compounds that overcome multiple drug resistance. The abilities of three structurally similar members of this family to interact with P-glycoprotein have been compared. Similarly to the effects of verapamil, N-methylwelwitindolinone C isothiocyanate (compound 1) attenuated the resistance of MCF-7/ADR cells to natural product anticancer drugs, including vinblastine, taxol, actinomycin D, daunomycin, and colchicine, without affecting the cytotoxicity of cisplatin. These effects of compound 1 were apparent at doses as low as 0.1 microM, indicating that it is considerably more potent than verapamil for reversal of resistance. Welwitindolinone C isothiocyanate (compound 3) demonstrated weaker reversing activity, whereas an analogue of compound 1 in which the isothiocyanate group is replaced by an isonitrile group (compound 2) was inactive. The accumulation of [3H]vinblastine in SK-VLB-1 cells was increased by compound 1 > compound 3 > verapamil >> compound 2. Interestingly, only compound 1 and verapamil enhanced [3H]taxol accumulation by these cells. Photoaffinity labeling of P-glycoprotein with [3H]azidopine in membranes from SK-VLB-1 cells was inhibited by compounds 1 and 3, but not by compound 2. Therefore, the differences in the size and/or the electronegativity of the isothiocyanate and isonitrile moieties appear to dramatically affect the abilities of the compounds to interact with P-glycoprotein.

The development of beta 1-adrenoceptors in brown adipose tissue following prenatal alcohol exposure

Prenatal alcohol exposure delays the development of thermoregulation in newborn rats. Newborns generate heat by the sympathetic nervous system's activation of nonshivering thermogenesis in brown adipose tissue (BAT). In this study, the effects of prenatal alcohol exposure on the development of the beta-adrenergic receptor system of BAT was investigated by assessing the number and pharmacological properties of beta-adrenergic receptors in BAT in 1-, 5-, 10-, and 20-day-old offspring. Pregnant dams were given either a liquid diet with 35% of the calories derived from alcohol, a liquid diet without alcohol for any effects of the liquid diet administration, or ad lib food and water. Offspring from the alcohol prenatal treatment group had a greater number of beta 1 adrenergic receptors compared to offspring from both from the pair-fed and lab chow control groups, which did not differ from each other. The greater number of receptor sites in 5-day-old subjects suggests that the number of binding sites in alcohol-exposed BAT cells continues to rise due to the absence of sufficient neurotransmitter, and perhaps reflects a delay in the arrival of sympathetic nervous system neurons. During the second and third postnatal weeks, when NE concentrations are rising and reaching asymptotic levels, the number of beta 1 adrenergic receptors in BAT of control subjects is decreasing. This expected compensatory "downregulation" response in receptor concentration was not seen in BAT from subjects exposed to alcohol prenatally. These findings may have important implications for understanding the effects of prenatal alcohol exposure on developing plasticity in the peripheral nervous system.

Incidence and management of pancreatic and enteric fistulas after surgical management of severe necrotizing pancreatitis

OBJECTIVE

To determine the incidence, type, and outcome of complications of necrotizing pancreatitis.

SETTING

Major tertiary referral center (Mayo Clinic, Rochester, Minn).

PATIENTS

Sixty-one patients seen from 1985 to 1994 who underwent surgical management of severe necrotizing pancreatitis and who developed pancreatic or gastrointestinal fistulas.

MAIN OUTCOME MEASURES

Incidence, management, and outcome of pancreatic and gastrointestinal fistulas.

RESULTS

Twenty-five patients (41%) developed pancreatic (14 patients) and/or gastrointestinal tract cutaneous (19 patients) fistulas. While three duodenal fistulas and one colonic fistula were recognized at the initial operation for pancreatic necrosectomy, the remainder developed 4 to 60 days after the initial operation. Spontaneous closure occurred in nine of 14 pancreatic, two of two gastric, two of four enteric, two of eight colonic, and four of five duodenal fistulas. Mortality of the group with fistulas was 24% (6/25) and was not different from the mortality of the patients with necrotizing pancreatitis without fistulas (28% [10/36]).

CONCLUSIONS

Pancreatic and gastrointestinal tract fistulas are common complications of surgical treatment of severe necrotizing pancreatitis. Well-controlled gastric, pancreatic, and enteric fistulas have the greatest likelihood of spontaneous closure. Duodenal and colonic fistulas may need surgical intervention for control or repair. Mortality in these patients parallels the mortality for severe necrotizing pancreatitis.

Aging- and oxygen-induced modifications in brain biochemistry and behavior

In summary, the work presented here has shown accumulation of oxidized protein with age in an animal aging model. In gerbil brain, this accumulation is associated with (1) decreased activity of oxidatively sensitive enzymes creatine kinase and glutamine synthetase; (2) decreased function of particular cytoskeletal proteins; and (3) decreased performance in a radial-arm maze task. Manipulations shown to increase the presence of reactive oxygen species in the brain increase oxidized protein, decrease the index enzyme activities and cytoskeletal protein defects, and worsen performance deficits. Moreover, intervention designed to quench ROS-mediated reactions decrease oxidized protein levels, and nearly normalize index enzyme activities and associated behavioral deficits. The precise connections between the performance deficits and protein measures are probably highly complex and likely to remain obscure for now. Currently, the behavioral measures serve as a marker for the functional consequences of the protein alterations. Our studies in humans have shown oxidized protein accumulation with age and a differential decrease of glutamine synthetase activity in the frontal lobe in AD. Further preliminary results in AD autopsy material show a striking correlation between the distribution of index enzyme inactivation and the known intensity distribution of AD pathology. These findings support the hypothesis that inability to restrain age- or pathology-related increases in local ROS activity can result in AD.

Malaria-induced increase of splenic gamma delta T cells in humans, monkeys, and mice

The number and distribution of gamma delta T cells in spleens from patients who died of cerebral malaria and from rhesus monkeys severely infected with Plasmodium coatneyi were examined by immunocytochemistry. gamma delta T cells were significantly increased in these spleens. In a rodent malaria model using Plasmodium chabaudi adami, an avirulent strain of murine malaria parasites, the degree of parasitemia appears to be modulated by the number of gamma delta T cells in the spleen. As parasitemia increases, these T cells increase in number. At some critical point, gamma delta T cells in collaboration with macrophages and alpha beta T cells apparently start to clear parasitized erythrocytes from the blood, leading to an abatement of the parasitemia, which is followed by a reduction in the number of gamma delta T cells. This gamma delta T cell phenomenon may be responsible for the self-limiting infection in mice.

Pathology of Rickettsia tsutsugamushi infection in Bandicota savilei, a natural host in Thailand

Following rodent surveys in a rice-growing area of central Thailand where we found Bandicota savilei, B. indica, and Rattus rattus infected with Rickettsia tsutsugamushi, we performed a study of pathogenesis of R. tsutsugamushi in laboratory-reared B. savilei. Eight animals were injected with saline and 19 animals were injected with 4.0 x 10(6) mouse 50% lethal dose units of a strain of R. tsutsugamushi isolated from a human in central Thailand. Animals were evaluated at intervals for IgG and IgM antibodies to R. tsutsugamushi by an indirect immunoperoxidase assay, the presence of the pathogen in liver and spleen by murine inoculation, and the pathology of representative tissues by gross and microscopic examination. The infected animals began to show internal evidence of mild illness 7-14 days after inoculation, and exhibited no changes in behavior. Total white blood cell counts decreased on day seven (including lymphocytes and polymorphonuclear leukocytes), followed by an almost equal increase on day 14. Gross pathology noted at necropsy was limited to slight liver and spleen enlargement accompanied by low numbers of abscesses and fibrinous tags present in the abdominal cavity. In addition to the gross morphologic changes, histopathologic lesions noted were all mild, consisting of vasculitis of the lung, activation of the mononuclear phagocyte system, abdominal mesothelial cell hyperplasia, and peritonitis. Rickettsiae were isolated from liver and spleen on days 0, 7, and 14, but not thereafter. Specific antibody response was first observed on day 14, peaked on day 21, and it decreased to levels observed in uninfected animals between days 120 and 180.(ABSTRACT TRUNCATED AT 250 WORDS)

Successful medical treatment of a spinal histoplasmoma

A woman with previously treated disseminated histoplasmosis was admitted with progressive paraparesis. Magnetic resonance imaging showed multifocal cerebritis and spinal histoplasmoma. She recovered following a second treatment with amphotericin B. This is the fourth reported patient with intramedullary spinal histoplasmoma, and the first demonstrating successful treatment of the lesion with medical therapy alone.

The VBP and a1/EBP leucine zipper factors bind overlapping subsets of avian retroviral long terminal repeat CCAAT/enhancer elements

Two long terminal repeat (LTR) enhancer-binding proteins which may regulate high rates of avian leukosis virus (ALV) LTR-enhanced c-myc transcription during bursal lymphomagenesis have been identified (A. Ruddell, M. Linial, and M. Groudine, Mol. Cell. Biol. 9:5660-5668, 1989). The genes encoding the a1/EBP and a3/EBP binding factors were cloned by expression screening of a lambda gt11 cDNA library from chicken bursal lymphoma cells. The a1/EBP cDNA encodes a novel leucine zipper transcription factor (W. Bowers and A. Ruddell, J. Virol. 66:6578-6586, 1992). The partial a3/EBP cDNA clone encodes amino acids 84 to 313 of vitellogenin gene-binding protein (VBP), a leucine zipper factor that binds the avian vitellogenin II gene promoter (S. Iyer, D. Davis, and J. Burch, Mol. Cell. Biol. 11:4863-4875, 1991). Multiple VBP mRNAs are expressed in B cells in a pattern identical to that previously observed for VBP in other cell types. The LTR-binding activities of VBP, a1/EBP, and B-cell nuclear extract protein were compared and mapped by gel shift, DNase I footprinting, and methylation interference assays. The purified VBP and a1/EBP bacterial fusion proteins bind overlapping but distinct subsets of CCAAT/enhancer elements in the closely related ALV and Rous sarcoma virus (RSV) LTR enhancers. Protein binding to these CCAAT/enhancer elements accounts for most of the labile LTR enhancer-binding activity observed in B-cell nuclear extracts. VBP and a1/EBP could mediate the high rates of ALV and RSV LTR-enhanced transcription in bursal lymphoma cells and many other cell types.

Jejunal responses to absorptive and secretory stimuli in the neurally isolated jejunum in vivo

BACKGROUND

Our aim was to assess changes in transport of water and electrolytes under basal, proabsorptive, and prosecretory conditions after an in situ neural isolation of the jejunoileum.

METHODS

Eight dogs underwent intraoperative perfusion of 50 cm of jejunum with a balanced electrolyte solution during sham operation and after neural isolation of the jejunoileum. Jejunal perfusion studies were later conducted in seven conscious dogs with a triple-lumen technique before and 2 and 8 weeks after neural isolation of the jejunoileum during intravenous infusion of 150 mmol/L sodium chloride (basal conditions), vasoactive intestinal polypeptide (VIP conditions), 500 pmol/kg per hour (prosecretory conditions), and the alpha 2-adrenergic agonist alpha-methylnorepinephrine (MNE), 900 nmol/kg per hour (proabsorptive conditions).

RESULTS

Neural isolation decreased intraoperative net absorption of water (4.4 +/- 0.9 vs 2.2 +/- 0.5 microliters/cm/min; p < 0.05) and electrolytes (sodium, chloride, bicarbonate, potassium). In conscious dogs during basal conditions, net absorptive flux was decreased (p < 0.05) at 2 but not at 8 weeks. VIP produced similar absolute decreases in net absorptive flux at all three time points. MNE increased net absorption before and at 8 weeks, but not at 2 weeks after autotransplantation.

CONCLUSIONS

In situ neural isolation of the jejunoileum decreased net basal jejunal absorption of water and electrolytes immediately and for at least 2 weeks. Proabsorptive responses to MNE but not prosecretory responses to VIP were altered at 2 weeks. Jejunal adaptation allowed absorptive function to return to near normal by 8 weeks.

Cryptophycin: a new antimicrotubule agent active against drug-resistant cells

Cryptophycin is a cytotoxic dioxadiazacyclohexadecenetetrone isolated from cyanobacteria of the genus Nostoc. Incubation of L1210 leukemia cells with cryptophycin resulted in dose-dependent inhibition of cell proliferation in parallel with increases in the percentage of cells in mitosis (half-maximal effects at < 10 pM). Indirect immunofluorescence studies demonstrated that treatment of A-10 vascular smooth muscle cells with cryptophycin results in marked depletion of cellular microtubules and reorganization of vimentin intermediate filaments, similar to the effects of vinblastine. Cytochalasin B caused the depolymerization of microfilaments in these cells, while neither vinblastine nor cryptophycin affected this cytoskeletal component. Pretreatment of cells with taxol prevented microtubule depolymerization in response to either vinblastine or cryptophycin. While microtubule depolymerization in response to vinblastine was rapidly reversed by removal of the drug, cells treated with cryptophycin remained microtubule depleted for at least 24 h after removal of the compound. Combinational treatments with vinblastine and cryptophycin resulted in additive cytotoxicity. Ovarian carcinoma and breast carcinoma cells which are multiply drug resistant due to overexpression of P-glycoprotein are markedly less resistant to cryptophycin than they are to vinblastine, colchicine, and taxol. Therefore, cryptophycin is a new antimicrotubule compound which appears to be a poorer substrate for P-glycoprotein than are the Vinca alkaloids. This property may confer an advantage to cryptophycin in the chemotherapy of drug-resistant tumors.

A sensitive assay for taxol and other microtubule-stabilizing agent

The ability of taxol to protect microtubules in cultured human ovarian carcinoma cells from drug- and cold-induced depolymerization was characterized as a functional assay for microtubule stabilizing agents. Treatment of the cells with concentrations of vinblastine or colchicine of 50 nM or greater, or incubation at 4 degrees C resulted in complete depolymerization of cytoplasmic microtubules. Pretreatment with taxol for 3 h enabled the cells to maintain substantial numbers of microtubules following the application of vinblastine or colchicine. This protective effect was easily observed at 50 nM taxol, whereas taxol-induced microtubule bundling was observed only at concentrations of 500 nM or greater. Concentrations of taxol as low as 10 nM stabilized microtubules against cold-induced depolymerization. Therefore, protection of microtubules from drug- and cold-induced depolymerization provides a sensitive functional assay for taxol. These systems should be similarly effective in identifying novel compounds which stabilize microtubules.

P-glycoprotein binding and modulation of the multidrug-resistant phenotype by estramustine

BACKGROUND

Previous preclinical studies of combinations of estramustine and vinblastine or paclitaxel (Taxol) have shown that it is possible to achieve a greater than additive cytotoxicity with these antimicrotubule drug combinations. Phase II studies in hormone-refractory prostate cancer have demonstrated clinical antitumor activity of sufficient magnitude to stimulate further laboratory and clinical studies of these drugs combinations.

PURPOSE

Our purpose was to characterize the interactions of estramustine with P-glycoprotein and to determine its effects.

METHODS

Standard laboratory techniques were used to study the effects of estramustine on intracellular drug concentrations, cytotoxicity, and induction of messenger RNA (mRNA) for the MDR1 (also known as PGY1) gene. Using a photoaffinity analogue of estramustine 17-0-[[2-[3-(4-azido-3-[125I]-iodophenyl) propionamido]ethyl]-carbamyl]estradiol-3-N-bis(2-chloroethyl)ca rba mate ([125I]AIPP-estramustine), binding to the membrane proteins of human ovarian (SKOV3) and their multidrug-resistant counterpart SKVLB1 cells was studied. Southern-blot analysis was performed on DNA extracted from human prostate carcinoma wild-type DU145, estramustine-resistant cell line (E4), and SKVLB1 cells.

RESULTS

Membrane fractions from SKOV3 and SKVLB1 cells were analyzed for proteins that could be photoaffinity labeled with [125I]AIPP-estramustine. Competitive inhibition of this binding was achieved with excess concentrations of (in order of efficacy) estramustine, vinblastine, verapamil, progesterone, and to a lesser degree, by paclitaxel but not with estramustine phosphate, estradiol, and estriol. SKVLB1 cells accumulated much less [3H]vinblastine and [3H]paclitaxel than did SKOV3 cells. Estramustine caused a concentration-dependent enhancement of drug accumulation in the SKVLB1 cells to a maximum of approximately 12-fold. No effect of estramustine was apparent for the wild-type SKOV3 cells. In comparison with verapamil, estramustine was less effective as a modulator; however estramustine demonstrated good chemosensitizing activity in combination with actinomycin D and vinblastine. Neither short-term, low-dose no longer-term, higher concentration were found to produce measurable transcript (mRNA for the MDR1 gene levels. Such data suggest that, at least levels. Such data suggest that, at least for two distinct human cell line (SKOV3 and DU145), estramustine does not induce the overexpression of the MDR1 gene.

CONCLUSION

It is apparent from the P-glycoprotein data that estramustine interacts with this efflux pump, altering intracellular drug accumulation. Overall, the nonempiric basis for including estramustine in clinical protocols that contain other multidrug-resistant drugs is strengthened by the present data.

Proguanil plus sulfamethoxazole is not causally prophylactic in the Macaca mulatta--Plasmodium cynomolgi model

New drugs for causal prophylaxis of malaria are needed. A proguanil/sulfamethoxazole combination was investigated using a rhesus monkey model (Macaca mulatta infected with Plasmodium cynomolgi) to determine whether causal prophylaxis could be achieved. When a five-day regimen of proguanil (40 mg/kg/day) combined with sulfamethoxazole (100 mg/kg/day) was used, infection of all animals (6 of 6) was observed, with an extended prepatent period (median 40 days). Two control animals became infected on days 9 and 23 following sporozoite inoculation. Plasma concentrations indicated that proguanil and sulfamethoxazole were adequately absorbed and metabolized to cycloguanil and N4-acetylsulfamethoxazole, respectively. Analysis of liver biopsy specimens demonstrated that the drugs were present two days following sporozoite inoculation but were not detectable one week later. Proguanil plus sulfamethoxazole does not eliminate exoerythrocytic-stage parasites in the rhesus monkey--P. cynomolgi model.

Transcriptional regulation of ALV bursal lymphomagenesis

Avian leukosis virus (ALV) induces bursal lymphoma in chickens after rare integration of proviral long terminal repeat (LTR) sequences next to the c-myc proto-oncogene. Labile LTR-binding proteins are essential for c-myc hyperexpression, since LTR-enhanced transcription, as well as the activity of the LTR-binding proteins, is specifically decreased following protein synthesis inhibition. This lability is restricted to hematopoetic cells of ALV-susceptible chicken strains, suggesting that the labile proteins play an important role in susceptibility to lymphomagenesis. Five proteins that interact with the ALV LTR enhancer were identified from bursal lymphoma cells: two proteins are stable (b and c), while three proteins (a1, a3, and b*) are labile in pre-B cell types. Two cDNAs (a1/EBP and a3/EBP) encoding leucine zipper proteins that bind to the ALV LTR enhancer were cloned using a lambda gt11 cDNA expression library made from bursal lymphoma cells. We are presently studying the roles of a1/EBP and a3/EBP in labile regulation of LTR-enhanced c-myc transcription and susceptibility to bursal lymphomagenesis.