Effects of chronic alcohol ingestion on the mesostriatal dopamine system in the rat

The effects of chronic alcohol use on the mesostriatal dopamine (DA) system remain relatively unknown. The aim of the present study was to assess multiple measures of the status of the mesostriatal DA system in rats chronically fed an alcohol diet for approximately 1 year. Tissue levels of DA and its metabolite, 3,4-dihydroxyphenylacetic acid, were significantly decreased in both the dorsal striatum (34 and 33%, respectively) and ventral striatum (33 and 36%, respectively) in alcohol-fed rats compared to pair-fed matched controls. Western blotting revealed a mean 20% decrease in tyrosine hydroxylase protein levels in the dorsal and ventral striatum of alcohol-fed animals while dopamine transporter protein levels from the same animals were significantly increased compared to controls (mean 60% increase for the dorsal and ventral striatum). The present results demonstrate significant alterations in the mesostriatal DA system after 1 year of chronic alcohol use. It is possible that the observed changes in DA synthesis and re-uptake measures result in altered intracellular and extracellular DA levels, perhaps contributing to the addictive properties of alcohol.

Pharmacokinetics of orally administered camptothecins

Phase I trials of oral camptothecins, including camptothecin (CPT) and irinotecan (CPT-11), have reported substantial interpatient variability in systemic exposure, which could result in suboptimal antitumor activity in some patients or enhanced risk for toxicity in others. This investigation evaluates the contribution of intestinal absorption and first-pass metabolism in the disposition of oral CPT and CPT-11, respectively. The transport of CPT in Caco-2 cell lines (validated model of intestinal drug transport) was concentration dependent and saturable (Vmax: 34 x 10(-5) cm/sec and Km: 20 microM), and was temperature dependent with an activation energy (Ea) of 11.7 kcal/mole. Cumulatively, this data was indicative of carrier-mediated intestinal transport. In addition, a reduction of transport in the presence of sodium azide plus deoxyglucose suggested ATP dependence. Thus, variable expression and availability of intestinal transporters could contribute to the observed wide variability in the exposure to oral CPT. CPT-11 is hydrolyzed by the ubiquitous enzyme carboxyl esterase to active SN-38, and first-pass metabolism of oral CPT-11 would include both intestinal and hepatic hydrolysis. Incubation of CPT-11 with S9 fractions of human liver and intestinal tissues resulted in variable rates of formation of SN-38. The mean (+/- SD) specific activities (pmoles/min/mg) were: liver (8.57 +/- 10.4, n = 8), duodenum (5.06 +/- 3.7, n = 4), jejunum (6.44 +/- 2.8, n = 5), ileum (4.81 +/- 2.4, n = 5), colon (1.93 +/- 1.5, n = 6), and rectum (0.82, n = 1). Interestingly, there was a decrease in SN-38 formation by tumor tissue compared to matched normal liver and colon tissues. Therefore variable first-pass metabolism could contribute to the substantial differences in the systemic exposures to CPT-11 and SN-38 in patients receiving oral CPT-11.

Misuse of antimicrobials in children with asthma and bronchiolitis: a review

Of 200 children hospitalized because of asthma or bronchiolitis, 100 received antibiotics inappropriately.

Reducing the cost of diagnosis of breast carcinoma: impact of ultrasound and imaging-guided biopsies on a clinical breast practice

BACKGROUND

The objective of this study was to determine whether the use of ultrasound and percutaneous breast biopsies in patients with screen-detected nonpalpable abnormalities can reduce benign open surgical biopsies of the breast without increasing cost or sacrificing detection of potentially curable breast carcinomas.

METHOD

Using a computerized mammography database and consecutive logs of needle localization procedures and fine- and large core needle biopsies of a single university-based breast imaging practice, the authors determined the breast carcinoma yield and cost of diagnosis over a 14-year period and the changes that occurred over time with the sequential introduction of ultrasound, ultrasound-guided biopsies, and stereotactic biopsies.

RESULTS

The overall breast carcinoma yield for needle localization biopsies of nonpalpable lesions increased from 21% in 1984 to 68% in 1998 (P < 0.0001). The yield for nonpalpable masses increased from 21% to 87% (P < 0.0001) over the same period. The selective use of ultrasound alone and percutaneous fine- and large core needle biopsy resulted in a substantial reduction in benign open surgical biopsies. A cost analysis showed a 50% reduction in the average expense of discovering breast carcinoma. The breast carcinomas detected after introduction of these methods were prognostically favorable with 88% measuring 1.5 cm or less in size and 66% measuring less than 1 cm.

CONCLUSIONS

Selective use of ultrasound and imaging-guided percutaneous biopsies can significantly reduce the number of benign open surgical biopsies generated by mammographic screening. This can result in substantial cost savings without decreasing the sensitivity for detecting small potentially curable lesions.

Changes in activity and regulation of the cardiac Ca2+ channel (L-type) by protein kinase C in chronic alcohol-exposed rats

BACKGROUND

It has been reported recently that long-term alcohol exposure in rats increases the number of dihydropyridine binding sites in cardiac membrane preparations. We fed Sprague Dawley rats a liquid diet that contained ethanol as 36% of total calories for 4 to 6 months and studied how alcohol exposure affected the activity and regulation of the cardiac Ca2+ channel.

METHODS

Dihydropyridine-sensitive cardiac Ca2+ channel activity was measured as the rate of Mn2+ quench of the cytosolic fura-2 signal in electrically stimulated myocytes.

RESULTS

In control rat myocytes, pretreatment with phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), reduced the rate of Mn2+ quench to 68% of the untreated cell response. Pretreatment with GF109203X, a protein kinase C inhibitor, enhanced the rate of influx by 56%, whereas Gö6976, an inhibitor of PKC alpha, beta, and gamma, did not affect the rate of influx. By contrast, PMA did not affect the rate of Mn2+ quench in alcoholic myocytes; however, the PKC inhibitor GF109203X still enhanced the rate of Mn2+ quench by 33%. Similar to control myocytes, no effect was observed after pretreatment with Gö6976 in the alcoholic cells. In both Western blot and immunoprecipitation experiments, PKC epsilon expression in alcohol-exposed myocytes was reduced to 68% of the control. However, the ratio of membrane/ cytosolic distribution of PKC epsilon in alcoholic myocytes was increased from 1.6 to 2.6. No change was detected in the expression of PKC alpha and PKC delta. PKC activity, measured in the presence of Gö6976, which inhibits PKC alpha, beta, and gamma, was reduced in alcoholic myocytes to 57% of the control, but the proportion of PKC activity in the particulate fraction was increased from 26% in the control myocytes to 36% in the alcoholic myocytes.

CONCLUSIONS

Altered expression and activity of PKC may be associated with changes in the regulation of the cardiac Ca2+ channel found in the hearts of rats chronically exposed to alcohol. Specifically, we found that the novel class of PKC isozymes is responsible for regulating the cardiac Ca2+ channel in control cardiomyocytes, and that the loss of PMA modulation found in the alcoholic cells may be due, in part, to reduced expression and altered distribution of PKC epsilon.

Sonography of palpable breast cancer

PURPOSE

Because of the increasing use of sonography to rule out cancer in women with palpable breast abnormalities, this study was performed to determine the rate of sonographically occult malignancy in this clinical setting.

METHODS

Women who were recommended for biopsy based on mammographic and/or clinical findings underwent breast sonography. This study retrospectively analyzed the subset of patients with palpable malignant lesions. Lesions were classified as visible or occult on mammography and sonography. Patients without a tissue diagnosis of tumor were excluded.

RESULTS

Of 1,346 masses that underwent biopsy or aspiration, 616 lesions were palpable, and of these, 293 were malignant. Sonography detected all 293 palpable malignant lesions (95% confidence interval for sensitivity, 99-100%). Eighteen lesions were mammographically occult. The median lesion size as determined by sonography was 1.8 cm; for the lesions that were mammographically occult, the median size was 1.6 cm. The most common histopathologic diagnosis for both groups of lesions was infiltrating ductal carcinoma.

CONCLUSIONS

All palpable malignant breast lesions were visible by sonography in patients in whom a biopsy was recommended. However, we caution that until the false-negative rate of sonography for equivocal palpable abnormalities is determined prospectively, sonography cannot be accurately applied to rule out malignancy in this setting.

The intestinal absorption of camptothecin, a highly lipophilic drug, across Caco-2 cells is mediated by active transporter(s)

The intestinal transport properties and kinetics of camptothecin (CPT) through Caco-2 cell monolayers were characterized by determining concentration-, temperature-, and ATP-dependence as well as the effect of selected inhibitors. The absorptive permeability (Peff) of CPT was found to be concentration dependent and saturable (K(m) = 31.2 +/- 6.9 microM) indicating the involvement of a high affinity, low capacity transport system. CPT transport was also temperature dependent and inhibited by sodium azide plus 2-deoxyglucose, which deplete cellular ATP, further suggesting that an active, carrier-mediated transport system contributes to CPT absorption. Based on inhibition studies, the involvement of organic anion and cation transporters was implicated but not conclusively demonstrated. Total CPT transport decreased four fold with increasing pH from 5.5 to 8.5 indicating that CPT lactone contributed more significantly to overall CPT transport than CPT carboxylate. The results of these studies suggest that CPT absorption is mediated by multiple mechanisms including significant passive diffusion and active transport components. Since typical substrates for intestinal carriers are hydrophilic and charged, the involvement of putative absorptive carriers in the transport of CPT is a novel finding that may give insight into the erratic oral bioavailability of CPTs observed in the clinic.

Role of pRB dephosphorylation in cell cycle regulation

pRB, the tumor suppressor product of the retinoblastoma susceptibility gene, is regarded as one of the key regulators of the cell cycle. This protein exerts its growth suppressive effect through its ability to bind and interact with a variety of cellular proteins. In turn, pRB binding and interacting ability is governed by its phosphorylation state. In recent years, this negative growth regulatory protein has captured a great deal of attention from investigators around the world due to its ability to modulate the activity of transcription regulatory proteins, enzymes which modify chromatin, and other cellular proteins which contribute to its complex role in mammalian cells. Hypophosphorylated pRB binds and sequesters transcription factors, most notably those of the E2F/DP family, inhibiting the transcription of genes required to traverse the G1 to S phase boundary. This cell cycle inhibitory function is abrogated when pRB undergoes phosphorylation mediated by cyclin/cdk complexes following cell stimulation by mitogens. Removal of these phosphates appears to be carried out by a multimeric complex of protein phosphatase type 1 (PP1) and noncatalytic regulatory subunits at the completion of mitosis. This dephosphorylation returns pRB to its active, growth suppressive state. While the mechanism of pRB phosphorylation has and continues to be extensively studied, dephosphorylation of pRB has received disproportionately less attention. The goal of this review is to revisit the role of pRB dephosphorylation in regulating the cell cycle. Emphasis will be placed on understanding the function and regulation of pRB during the cell cycle as well as our ever-expanding notions of pRB-PP1 interaction and the mechanism of pRB dephosphorylation at mitotic exit.

Potential use of ipatropium bromide for the treatment of clozapine-induced hypersalivation: a preliminary report

Sialorrhea is reported by 31% of patients taking clozapine. Anticholinergic agents and adrenergic agonists are used for its treatment based on empirical evidence. In the present study, 10 patients who failed to respond to anticholinergic or adrenergic agents received intranasal ipatropium bromide (IPB) to minimize anticholinergic systemic absorption. Intranasal IPB was given to 10 patients for clozapine-induced sialorrhea who failed to respond to benztropine or clonidine. Pre-, post- and 6 month follow-up values were recorded on a single-item, 5-point Hypersalivation Rating Scale. The sign test was used for statistical comparison (P < 0.05). Eight patient reported initial improvement in sialorrhea values. Two patients reported no change and two patients discontinued IPB. At 6 months, six patients maintained improvement. Side-effects for IPB were minor. A significant trend was observed in the values pre- and post-treatment with IPB (P < 0.004). Improvement was maintained at 6 month follow-up (P < 0.008). This case series demonstrates the possible utility of intranasal IPB for clozapine-induced sialorrhea. Intranasal IPB lacks significant systemic anticholinergic effects when prescribed along with clozapine. This study shows only qualitative differences in salivation values and large controlled-comparative trials are needed.

Modeling alcohol's effects on organs in animal models

Researchers have developed numerous animal models to investigate the development of various alcohol-related diseases. Such models have provided insights into the mechanism through which alcohol can induce liver damage. Animal models also have helped researchers explore the mechanisms by which both short-term (e.g., binge) and long-term drinking can interfere with the function of the heart, a condition referred to as alcoholic cardiomyopathy. Furthermore, animal models have provided substantial information on the causes of fetal alcohol syndrome. Such models have demonstrated that exposure to alcohol during gestation can lead to prenatal and postnatal growth retardation, characteristic facial malformations, immune system deficiencies, and alterations in the central nervous system.

Effect of chronic ethanol exposure on inositol trisphosphate receptors in WB rat liver epithelial cells

BACKGROUND

Enhanced agonist-induced Ca2+ release has been reported in hepatocytes isolated from ethanol-fed rats. Because myo-inositol 1,4,5-trisphosphate receptors (IP3Rs) are involved in the mobilization of Ca2+, we examined the effects of chronic ethanol treatment on IP3R function and levels of IP3R protein by using WB rat liver epithelial cells.

METHODS

WB cells were treated with ethanol (50-150 mM) for 24 to 48 hr and were loaded with Fura-2 to measure agonist-induced Ca2+ mobilization or saponin permeabilized to measure myo-inositol 1,4,5-trisphosphate (IP3)-mediated Ca2+ release. IP3 levels were measured in [3H]-inositol labeled cells. Levels of IP3R protein were quantitated by immunoblotting with antibodies to IP3R isoforms. Lysosomal and proteasomal peptidase activities were assayed in cytosol and membrane fractions using specific fluorogenic peptide substrates.

RESULTS

Ethanol treatment enhanced Ca2+ mobilization in response to angiotensin II, vasopressin, and bradykinin. This effect was not due to an increased production of IP3. Chronic ethanol treatment stimulated the mobilization of Ca2+ from saponin-permeabilized cells in response to subsaturating doses of IP3 and increased the basal levels of both type I and type III IP3Rs by 1.8-fold and 1.6-fold, respectively. Ethanol treatment did not prevent angiotensin II-induced IP3R down-regulation or alter lysosomal cathepsin B activity or the trypsin-like and peptidylglutamyl peptidase activities of the proteasome. However, chronic ethanol exposure resulted in a 60% and 41% inhibition of the chymotrypsin-like activity of the proteasome in cytosol and microsomal membranes, respectively.

CONCLUSION

We propose that the enhanced agonist-mediated Ca2+ mobilization observed in chronic ethanol-treated WB liver epithelial cells results from increased IP3R expression caused by an inhibition of IP3R degradation pathways by ethanol.

Leucovorin, 5-fluorouracil, and gemcitabine: a phase I study

Gemcitabine is a chemotherapy agent with efficacy in the treatment of lung, pancreas, bladder and breast cancer. It inhibits DNA synthesis by interfering with cytidine triphosphate production and also inhibits the activity of ribonucleotide reductase. Gemcitabine may potentiate fluorouracil's inhibition of thymidylate synthase. This inhibition would be expected to be sequence dependent, occurring only if gemcitabine were administered following fluorouracil (5FU). The combination of leucovorin, 5-FU, and gemcitabine was assessed in this phase I trial. Eligibility requirements included refractory solid tumor malignancy; adequate hematologic, renal and hepatic reserve; no prior therapy with the combination of leucovorin and 5FU, or with gemcitabine; ECOG performance status 0-2, and signed informed consent. Eleven men and nine women were eligible. The median age was 52.5 years and the median performance status was 1. All but three patients had prior chemotherapy. The starting doses were leucovorin 20 mg/m2, 5FU 255 mg/m2 and gemcitabine 600 mg/m2. 5FU and gemcitabine were escalated in tandem to 340 mg/m2 and 800 mg/m2 and thereafter to 425 mg/m2 and 1000 mg/m2, respectively. Gemcitabine administration always followed that of 5FU by 30 minutes. The median number of cycles was 2 (range 1-32). Two patients at the starting dose had disease progression within the first cycle with one death on day 28. One patient with cholangiocarcinoma had a partial response and remained on study for 40 months. There were no other responses. The maximum tolerated dose is leucovorin 20 mg/m2, 5FU 340 mg/m2, and gemcitabine 800 mg/m2. The impact of drug sequence remains undetermined.

Characteristics of medical students completing an honors program in pathology

The Honors Program in pathology at Jefferson Medical College provides a voluntary enrichment opportunity for students who have demonstrated a superior ability to cope with the pathology curriculum and who rank in the upper fifth of their class. This study was performed to determine whether honor students possess cognitive and psychosocial attributes that distinguish them from their classmates. Students from five academic years (entering classes 1991 to 1995) were divided into 3 groups: (1) those who completed the Honors Program (n = 85), (2) those in the top 20% of the class who were offered the option but chose not to participate in the Honors Program (n = 128), and (3) students who did not qualify for the program (n = 953). Comparisons between these three groups were made on the basis of selected measures of academic achievement retrieved from the Jefferson Longitudinal Study database and psychosocial data obtained from a questionnaire completed during the first-year orientation. Students who completed the Honors Program in pathology had scored higher on the physical science section of the Medical College Admission Test (MCAT) and had obtained higher first-year grade point averages than students in both of the other groups. Subsequently, they attained higher second-year grade point averages and scored higher on Step 1 and Step 2 of the United States Medical Licensing Examination (USMLE), compared with their peers in the other groups. There were no significant differences in psychosocial measures between honor students and the rest of the cohort (group 3). However, students in the top 20% of the class who declined the invitation to participate in the Honors Program (group 2) showed higher scores on the Taylor Manifest Anxiety Scale and the Eysenck Emotional Instability (Neuroticism) Scale than did their classmates. Despite these differences, students who completed the Honors Program (group 1) and eligible students who declined participation (group 2) selected similar pathways of postgraduate residency training: both groups preferred internal medicine to family practice, and both were more likely than the rest of the cohort to begin residency training at a top-ranked academic/research medical center. Voluntary participation in an Honors Program is a self-selection system that identifies students who are most likely to succeed academically at the highest levels. Residency selection committees may wish to pay dose attention to student involvement in similar programs, because this information may provide insights into student personality and general aptitude.

The camptothecin-resistant topoisomerase I mutant F361S is cross-resistant to antitumor rebeccamycin derivatives. A model for topoisomerase I inhibition by indolocarbazoles

DNA topoisomerase I is a major cellular target for antitumor indolocarbazole derivatives (IND) such as the antibiotic rebeccamycin and the synthetic analogue NB-506 which is undergoing phase I clinical trials. We have investigated the mechanism of topoisomerase I inhibition by a rebeccamycin analogue, R-3, using the wild-type human topoisomerase I and a well-characterized recombinant enzyme, F361S. The catalytic activity of this mutant remains fully intact, but the enzyme is resistant to inhibition by camptothecin (CPT). Here we show that the mutated enzyme is cross-resistant to the rebeccamycin analogue. Despite their profound structural differences, CPT and R-3 interfere similarly with the activity of the wild-type and mutant topoisomerase I enzymes, and the drug-induced cleavable complexes are equally sensitive to the NaCl concentration. CPT and IND likely recognize identical structural elements of the topoisomerase I-DNA covalent complex; however, differences do exist in terms of sequence-specificity of topoisomerase I-mediated DNA cleavage. For the first time, a molecular model showing that CPT and IND share common steric and electronic features is proposed. The model helps to identify a specific pharmacophore for topoisomerase I inhibitors.

Phase I clinical and pharmacologic study of 13-cis-retinoic acid, interferon alfa, and paclitaxel in patients with prostate cancer and other advanced malignancies

PURPOSE

Recent studies demonstrate that retinoids decrease expression of the anti-apoptotic protein bcl-2, enhance the effect of chemotherapy, and act synergistically with interferon alfa (IFNalpha) to inhibit tumor cell growth in vitro. A phase I trial of 13-cis-retinoic acid (CRA), IFNalpha, and paclitaxel (TAX) was conducted to determine the toxicity and recommended phase II dose of this combination. Pharmacodynamic studies were performed to determine whether CRA and IFNalpha could modulate bcl-2 expression in vitro and in patients.

PATIENTS AND METHODS

Twenty-two patients with prostate cancer or other advanced malignancies were treated with CRA/IFNalpha and escalating doses of TAX. The effect of CRA/IFNalpha on TAX pharmacokinetics was analyzed in both patients and human liver microsomes. The effect of CRA/IFNalpha on bcl-2 expression was assessed in vitro and in peripheral-blood mononuclear cells (PBMCs) by immunoblotting.

RESULTS

CRA 1 mg/kg on days 1 to 4, IFNalpha 6 MU/m(2) subcutaneously on days 1 to 4, and TAX 175 mg/m(2) on day 3 was well tolerated. Pharmacokinetic studies demonstrated that CRA/IFNalpha caused a 33% decrease in TAX clearance and a 23% decrease in the area under the concentration-time curve values of the TAX metabolite 6-alfa-hydroxytaxol (6-HT). CRA alone reduced conversion of TAX to 6-HT by 41% in human liver microsomes. CRA/IFNalpha decreased bcl-2 expression in vitro and in PBMCs.

CONCLUSION

CRA/IFNalpha and TAX is a well-tolerated regimen. CRA/IFNalpha increases TAX area under the concentration-time curve through an inhibitory effect of CRA on the metabolism of TAX to 6-HT. CRA/IFNalpha can modulate bcl-2 expression in vitro and demonstrates similar biologic activity in patients. Further studies will determine the activity of CRA/IFNalpha/TAX and validate the assessment of bcl-2 in PBMCs as a marker of tumor response.

Stomatocytosis is absent in "stomatin"-deficient murine red blood cells

To examine the relationship between erythrocyte membrane protein 7. 2b deficiency and the hemolytic anemia of human hereditary stomatocytosis, we created 7.2b knock-out mice by standard gene targeting approaches. Immunoblots showed that homozygous knock-out mice completely lacked erythrocyte protein 7.2b. Despite the absence of protein 7.2b, there was no hemolytic anemia and mouse red blood cells (RBCs) were normal in morphology, cell indices, hydration status, monovalent cation content, and ability to translocate lipids. The absence of the phenotype of hereditary stomatocytosis implies that protein 7.2b deficiency plays no direct role in the etiology of this disorder and casts doubt on the previously proposed role of this protein as a mediator of cation transport in RBC.