ODP109 PARATHYROID HORMONE AND 25 OH VITAMINA D IN PREGNANCY: DATA FROM AN ARGENTINEAN COHORT SUPPORTING SUPPLEMENTATION

 

Vitamin D (Vit D) deficiency has become a global health care issue, as it affects a great number of women during pregnancy and lactation. Vit D levels are critical during pregnancy, being the mother the only source of them for the developing fetus; an enzymatic system for conversion of 25OH VitD into 1-25(OH) 2 VitD is present in the placenta, thus reinforcing the importance of VitD during gestation. VitD deficiency has been associated with obstetric complications and adverse outcomes in offspring, affecting skeletal, immunological and respiratory systems. It is known that prenatal supplements available do not contain enough VitD to fulfil requirements. It is generally accepted that elevated PTH is an indicator of VitD deficiency, and Hysaj O et al (2021) showed that 25OH VitD is a statistically significant determinant of PTH levels in early and late pregnancy.

Aim

To evaluateVitD status and its relationship to parathyroid hormone (PTH) in a cohort of pregnant women representative of multiple Argentinian regions.

Subjects and Methods

Data from samples of 423 pregnant women in 1st and 2nd trimester were collected between 2016 and 2021. VitD was measured in different platforms: DiaSorin Liaison CLIA (n=184), Roche COBAS ECLIA (n=166), Abbott ARCHITECT CMIA (n=33), Biomérieux VIDAS ELFA (n=18) and Siemens CENTAUR CLIA (n=16). PTH (ng/L) was measured in 162 samples by SIEMENS IMMULITE CLIA and Roche COBAS ECLIA. As VitD is light-exposure dependent, we considered warm and high light-exposure season period from December to March and cold and low light season from April to September. VITD (ng/L) levels were classified as Deficient (<20), Insufficient (between 21 and 29) and Sufficient (>30) (Endocrine Society, 2014).

Results

From 423 data collected, 102 were excluded because of lacking information on VitD supplementation. From the remaining non supplemented 321 samples, 48% resulted insufficient, 30% deficient and 22% sufficient for VitD (groups comparison: p< 0. 05, Kruskal Wallis-Dunn test). The seasonal period and pregnancy trimester distributions didn't show significant differences. Similar results of VitD insufficiency were found in the major used platforms, regardless the seasonal period considered. PTH results expressed as median and interquartile range were (ng/L): 32. 0 (13.7-169. 0) in Deficient pregnancies (N=92), 23.7(13.3-88. 0) in Insufficient (n=50) and 18.7 (9.8-55.7) in Sufficient (n=20).

Conclusions

This study shows VitD inadequate levels in 78% in non-supplemented pregnancies, regardless season or measurement platform. Relative elevated levels of PTH were associated to pregnancies with VitD deficiency, evidenciating a regulatory role according to published data. To improve VitD status during pregnancy it would be advisable to pose new strategies for prenatal supplements developed by a multidisciplinary professional team.

Presentation: No date and time listed

The influence of anastomotic techniques on postoperative anastomotic complications: Results of the Oesophago-Gastric Anastomosis Audit

BACKGROUND

The optimal anastomotic techniques in esophagectomy to minimize rates of anastomotic leakage and conduit necrosis are not known. The aim of this study was to assess whether the anastomotic technique was associated with anastomotic failure after esophagectomy in the international Oesophago-Gastric Anastomosis Audit cohort.

METHODS

This prospective observational multicenter cohort study included patients undergoing esophagectomy for esophageal cancer over 9 months during 2018. The primary exposure was the anastomotic technique, classified as handsewn, linear stapled, or circular stapled. The primary outcome was anastomotic failure, namely a composite of anastomotic leakage and conduit necrosis, as defined by the Esophageal Complications Consensus Group. Multivariable logistic regression modeling was used to identify the association between anastomotic techniques and anastomotic failure, after adjustment for confounders.

RESULTS

Of the 2238 esophagectomies, the anastomosis was handsewn in 27.1%, linear stapled in 21.0%, and circular stapled in 51.9%. Anastomotic techniques differed significantly by the anastomosis sites (P < .001), with the majority of neck anastomoses being handsewn (69.9%), whereas most chest anastomoses were stapled (66.3% circular stapled and 19.3% linear stapled). Rates of anastomotic failure differed significantly among the anastomotic techniques (P < .001), from 19.3% in handsewn anastomoses, to 14.0% in linear stapled anastomoses, and 12.1% in circular stapled anastomoses. This effect remained significant after adjustment for confounding factors on multivariable analysis, with an odds ratio of 0.63 (95% CI, 0.46-0.86; P = .004) for circular stapled versus handsewn anastomosis. However, subgroup analysis by anastomosis site suggested that this effect was predominantly present in neck anastomoses, with anastomotic failure rates of 23.2% versus 14.6% versus 5.9% for handsewn versus linear stapled anastomoses versus circular stapled neck anastomoses, compared with 13.7% versus 13.8% versus 12.2% for chest anastomoses.

CONCLUSIONS

Handsewn anastomoses appear to be independently associated with higher rates of anastomotic failure compared with stapled anastomoses. However, this effect seems to be largely confined to neck anastomoses, with minimal differences between techniques observed for chest anastomoses. Further research into standardization of anastomotic approach and techniques may further improve outcomes.

Textbook outcome following oesophagectomy for cancer: international cohort study

Background

Textbook outcome has been proposed as a tool for the assessment of oncological surgical care. However, an international assessment in patients undergoing oesophagectomy for oesophageal cancer has not been reported. This study aimed to assess textbook outcome in an international setting.

Methods

Patients undergoing curative resection for oesophageal cancer were identified from the international Oesophagogastric Anastomosis Audit (OGAA) from April 2018 to December 2018. Textbook outcome was defined as the percentage of patients who underwent a complete tumour resection with at least 15 lymph nodes in the resected specimen and an uneventful postoperative course, without hospital readmission. A multivariable binary logistic regression model was used to identify factors independently associated with textbook outcome, and results are presented as odds ratio (OR) and 95 per cent confidence intervals (95 per cent c.i.).

Results

Of 2159 patients with oesophageal cancer, 39.7 per cent achieved a textbook outcome. The outcome parameter ‘no major postoperative complication’ had the greatest negative impact on a textbook outcome for patients with oesophageal cancer, compared to other textbook outcome parameters. Multivariable analysis identified male gender and increasing Charlson comorbidity index with a significantly lower likelihood of textbook outcome. Presence of 24-hour on-call rota for oesophageal surgeons (OR 2.05, 95 per cent c.i. 1.30 to 3.22; P = 0.002) and radiology (OR 1.54, 95 per cent c.i. 1.05 to 2.24; P = 0.027), total minimally invasive oesophagectomies (OR 1.63, 95 per cent c.i. 1.27 to 2.08; P &lt; 0.001), and chest anastomosis above azygous (OR 2.17, 95 per cent c.i. 1.58 to 2.98; P &lt; 0.001) were independently associated with a significantly increased likelihood of textbook outcome.

Conclusion

Textbook outcome is achieved in less than 40 per cent of patients having oesophagectomy for cancer. Improvements in centralization, hospital resources, access to minimal access surgery, and adoption of newer techniques for improving lymph node yield could improve textbook outcome.

Textbook outcome following oesophagectomy for cancer: international cohort study

BACKGROUND

Textbook outcome has been proposed as a tool for the assessment of oncological surgical care. However, an international assessment in patients undergoing oesophagectomy for oesophageal cancer has not been reported. This study aimed to assess textbook outcome in an international setting.

METHODS

Patients undergoing curative resection for oesophageal cancer were identified from the international Oesophagogastric Anastomosis Audit (OGAA) from April 2018 to December 2018. Textbook outcome was defined as the percentage of patients who underwent a complete tumour resection with at least 15 lymph nodes in the resected specimen and an uneventful postoperative course, without hospital readmission. A multivariable binary logistic regression model was used to identify factors independently associated with textbook outcome, and results are presented as odds ratio (OR) and 95 per cent confidence intervals (95 per cent c.i.).

RESULTS

Of 2159 patients with oesophageal cancer, 39.7 per cent achieved a textbook outcome. The outcome parameter 'no major postoperative complication' had the greatest negative impact on a textbook outcome for patients with oesophageal cancer, compared to other textbook outcome parameters. Multivariable analysis identified male gender and increasing Charlson comorbidity index with a significantly lower likelihood of textbook outcome. Presence of 24-hour on-call rota for oesophageal surgeons (OR 2.05, 95 per cent c.i. 1.30 to 3.22; P = 0.002) and radiology (OR 1.54, 95 per cent c.i. 1.05 to 2.24; P = 0.027), total minimally invasive oesophagectomies (OR 1.63, 95 per cent c.i. 1.27 to 2.08; P < 0.001), and chest anastomosis above azygous (OR 2.17, 95 per cent c.i. 1.58 to 2.98; P < 0.001) were independently associated with a significantly increased likelihood of textbook outcome.

CONCLUSION

Textbook outcome is achieved in less than 40 per cent of patients having oesophagectomy for cancer. Improvements in centralization, hospital resources, access to minimal access surgery, and adoption of newer techniques for improving lymph node yield could improve textbook outcome.

Registro Nacional de Síndrome Coronario Agudo en Paraguay (RENASCA-PY)

Objetivo:

Determinar el tratamiento inicial y la mortalidad intrahospitalaria de pacientes con síndrome coronario agudo que acudieron a centros hospitalarios de referencia de Paraguay.

Método:

Estudio observacional y multicéntrico en pacientes mayores de 18 años con diagnóstico confirmado de síndrome coronario agudo.

Resultados:

Se incluyó a 780 pacientes desde mayo de 2015 hasta febrero de 2016; la edad media fue de 64.1 ± 12.3 años y el género masculino representó el 64.1%. La presentación clínica fue la de síndrome coronario agudo con elevación del ST en 40.1% y sin elevación del ST en 59.9%. En pacientes con elevación del ST se observó un alto porcentaje de consultas tardías, mayor de 12 h de evolución en 49.8%; en aquéllos con menos de 12 h de evolución se indicó la reperfusión en 52.2%, el 36.3% recibió fibrinolíticos y 15.9% intervención coronaria percutánea primaria. La mortalidad hospitalaria del síndrome coronario agudo fue de 10.3%, con elevación del segmento ST en 12.8% y sin elevación del segmento ST en 8.6%.

Conclusiones:

El tratamiento del síndrome coronario agudo en el Paraguay requiere un abordaje integral, que promueva consultas más tempranas y aumente la institución de tratamientos de reperfusión en la red de servicios de salud; el objetivo es mejorar los índices de respuesta terapéutica y disminuir la mortalidad hospitalaria.

Postoperative outcomes in oesophagectomy with trainee involvement

BACKGROUND

The complexity of oesophageal surgery and the significant risk of morbidity necessitates that oesophagectomy is predominantly performed by a consultant surgeon, or a senior trainee under their supervision. The aim of this study was to determine the impact of trainee involvement in oesophagectomy on postoperative outcomes in an international multicentre setting.

METHODS

Data from the multicentre Oesophago-Gastric Anastomosis Study Group (OGAA) cohort study were analysed, which comprised prospectively collected data from patients undergoing oesophagectomy for oesophageal cancer between April 2018 and December 2018. Procedures were grouped by the level of trainee involvement, and univariable and multivariable analyses were performed to compare patient outcomes across groups.

RESULTS

Of 2232 oesophagectomies from 137 centres in 41 countries, trainees were involved in 29.1 per cent of them (n = 650), performing only the abdominal phase in 230, only the chest and/or neck phases in 130, and all phases in 315 procedures. For procedures with a chest anastomosis, those with trainee involvement had similar 90-day mortality, complication and reoperation rates to consultant-performed oesophagectomies (P = 0.451, P = 0.318, and P = 0.382, respectively), while anastomotic leak rates were significantly lower in the trainee groups (P = 0.030). Procedures with a neck anastomosis had equivalent complication, anastomotic leak, and reoperation rates (P = 0.150, P = 0.430, and P = 0.632, respectively) in trainee-involved versus consultant-performed oesophagectomies, with significantly lower 90-day mortality in the trainee groups (P = 0.005).

CONCLUSION

Trainee involvement was not found to be associated with significantly inferior postoperative outcomes for selected patients undergoing oesophagectomy. The results support continued supervised trainee involvement in oesophageal cancer surgery.

Mortality from esophagectomy for esophageal cancer across low, middle, and high-income countries: An international cohort study

BACKGROUND

No evidence currently exists characterising global outcomes following major cancer surgery, including esophageal cancer. Therefore, this study aimed to characterise impact of high income countries (HIC) versus low and middle income countries (LMIC) on the outcomes following esophagectomy for esophageal cancer.

METHOD

This international multi-center prospective study across 137 hospitals in 41 countries included patients who underwent an esophagectomy for esophageal cancer, with 90-day follow-up. The main explanatory variable was country income, defined according to the World Bank Data classification. The primary outcome was 90-day postoperative mortality, and secondary outcomes were composite leaks (anastomotic leak or conduit necrosis) and major complications (Clavien-Dindo Grade III - V). Multivariable generalized estimating equation models were used to produce adjusted odds ratios (ORs) and 95% confidence intervals (CI95%).

RESULTS

Between April 2018 to December 2018, 2247 patients were included. Patients from HIC were more significantly older, with higher ASA grade, and more advanced tumors. Patients from LMIC had almost three-fold increase in 90-day mortality, compared to HIC (9.4% vs 3.7%, p < 0.001). On adjusted analysis, LMIC were independently associated with higher 90-day mortality (OR: 2.31, CI95%: 1.17-4.55, p = 0.015). However, LMIC were not independently associated with higher rates of anastomotic leaks (OR: 1.06, CI95%: 0.57-1.99, p = 0.9) or major complications (OR: 0.85, CI95%: 0.54-1.32, p = 0.5), compared to HIC.

CONCLUSION

Resections in LMIC were independently associated with higher 90-day postoperative mortality, likely reflecting a failure to rescue of these patients following esophagectomy, despite similar composite anastomotic leaks and major complication rates to HIC. These findings warrant further research, to identify potential issues and solutions to improve global outcomes following esophagectomy for cancer.

Comparison of short-term outcomes from the International Oesophago-Gastric Anastomosis Audit (OGAA), the Esophagectomy Complications Consensus Group (ECCG), and the Dutch Upper Gastrointestinal Cancer Audit (DUCA)

BACKGROUND

The Esophagectomy Complications Consensus Group (ECCG) and the Dutch Upper Gastrointestinal Cancer Audit (DUCA) have set standards in reporting outcomes after oesophagectomy. Reporting outcomes from selected high-volume centres or centralized national cancer programmes may not, however, be reflective of the true global prevalence of complications. This study aimed to compare complication rates after oesophagectomy from these existing sources with those of an unselected international cohort from the Oesophago-Gastric Anastomosis Audit (OGAA).

METHODS

The OGAA was a prospective multicentre cohort study coordinated by the West Midlands Research Collaborative, and included patients undergoing oesophagectomy for oesophageal cancer between April and December 2018, with 90 days of follow-up.

RESULTS

The OGAA study included 2247 oesophagectomies across 137 hospitals in 41 countries. Comparisons with the ECCG and DUCA found differences in baseline demographics between the three cohorts, including age, ASA grade, and rates of chronic pulmonary disease. The OGAA had the lowest rates of neoadjuvant treatment (OGAA 75.1 per cent, ECCG 78.9 per cent, DUCA 93.5 per cent; P < 0.001). DUCA exhibited the highest rates of minimally invasive surgery (OGAA 57.2 per cent, ECCG 47.9 per cent, DUCA 85.8 per cent; P < 0.001). Overall complication rates were similar in the three cohorts (OGAA 63.6 per cent, ECCG 59.0 per cent, DUCA 62.2 per cent), with no statistically significant difference in Clavien-Dindo grades (P = 0.752). However, a significant difference in 30-day mortality was observed, with DUCA reporting the lowest rate (OGAA 3.2 per cent, ECCG 2.4 per cent, DUCA 1.7 per cent; P = 0.013).

CONCLUSION

Despite differences in rates of co-morbidities, oncological treatment strategies, and access to minimal-access surgery, overall complication rates were similar in the three cohorts.

Initial clinical experience with a powered circular stapler for colorectal anastomosis

BACKGROUND

The Echelon circular™ powered stapler (ECP stapler) obviates the need for manual firing of conventional circular staplers during the construction of a colorectal anastomosis, but has not been evaluated clinically. The aim of this study was to perform a clinical evaluation of this stapler.

METHODS

A retrospective review of the initial clinical experience of a single surgeon using the ECP stapler for left-sided colorectal anastomosis construction during elective colorectal resections for benign and malignant disease was conducted by analyzing results from a prospectively maintained study database. Additionally, four attending colorectal and/or general surgeons who had performed ≥ 5 colorectal operations with the ECP stapler were invited to complete an anonymous online survey to subjectively assess the user experience with the device. Statistical analysis was conducted using Microsoft Excel Version 15.33.

RESULTS

Seventeen patients underwent left-sided anastomotic reconstruction using the ECP stapler. All donuts (proximal and distal) were intact. Anastomotic integrity was evaluated using the air-leak test utilizing flexible video sigmoidoscopy. No leaks were observed, although one patient (5.9%) developed a postoperative pelvic abscess. The anonymous survey was completed by all four surgeons. Subjective evaluation of the ECP stapler suggests that the overall stapling quality, overall device ease-of-use, and the overall perception of anastomotic quality as above average when compared to manual 'end-to-end anastomosis' (EEA) stapling devices.

CONCLUSIONS

In an initial clinical evaluation of the ECP stapler, the safety and ease-of-use of the device appears to be satisfactory. Powered stapling and the design of '3D stapling' may provide advantages over manual systems, and may improve the construction quality of left-sided colorectal anastomosis.

Use of pulp mill inorganic wastes as alternative liming materials

A laboratory aerobic incubation study was performed during 18 weeks under controlled conditions to assess the effects of applying different doses of pulp mill inorganic wastes on the physical-chemical properties of an acid Dystric Cambissol. Three different inorganic wastes were tested - wood ash, dregs and grits, and an agriculture limestone was used as reference. Results showed that increasing the dose applied of the different inorganic wastes tested always led to significant raises of soil pH at different incubation times demonstrating that its use as alternative-liming materials could be a valid and less expensive option to the use of commercial agricultural limestone. Moreover, no immediate concerns seem to be expected related to soil exchangeable sodium (Na) content, at least for the doses needed to increase soil pH until the targeted value 6.5. Particularly for wood ash a pronounced increase on soil extractable potassium and phosphorous was observed, indicating that besides the liming effect this waste can contribute to improve soil fertility by supplying significant available amounts of these nutrients. Finally, metals do not seem to be a limiting factor for the application to land of these by-products.

Short-term effects on soil properties and wheat production from secondary paper sludge application on two Mediterranean agricultural soils

This study was conducted under greenhouse conditions to evaluate the potential use of SPS as a fertilizer, amendment and/or liming agent for wheat (Triticum aestivum L.). Two representative Mediterranean agricultural soils, a Cambic Arenosol (cmAR) and a Cromic Cambisol (crCM) were used. Treatments included four sludge rates ranging from 0 to 40 g kg(-1) (equivalent of 0, 38, 88 and 120 Mg ha(-1)). A significant increment in soil pH, organic carbon, N total, available P and exchangeable K were observed in both soils. Sludge application significantly increased N and decreased Zn, Mn and Cu concentrations in wheat. Wheat grain yields were reduced by 33% and 37% when 120 Mg SPS ha(-1) was applied to cmAR and crCM soils, respectively, due apparently to unavailability of Mg. However, straw yields, with much lower Mg requirements, increased significantly with SPS rates. Secondary pulp mill sludge seems to be a potential source of organic matter, N, P, K and a potential soil amendment liming agent for acid soils, when appropriate supplemental fertilizer was provided. For grain crops grown in these soils, addition of Mg is required for proper nutrient balance.

Evaluation of a compost obtained from forestry wastes and solid phase of pig slurry as a substrate for seedlings production

A composted material obtained from forestry wastes and solid phase of pig slurry was evaluated as a substrate component for the production of tomato and lettuce seedlings. Four different substrates were tested: compost (100C), a mixture of 75% compost and 25% peat substrate (75C), a mixture of 50% compost and 50% peat substrate (50C), and peat-based substrate (control). Compost increased the pH of the substrate from 6.3 (control) to 6.9 (100C) but did not affect the electrical conductivity (0.26 and 0.27 mScm(-1), respectively, for control and 100C). Germination and growth of lettuce seedlings were not affected by the substrate type, contrasting with tomato seedlings where the highest growth occurred at 100C substrate. Increasing compost percentage on substrate increased nitrogen, calcium and magnesium availability and, consequently, the concentration of these elements in plant tissues increased. On the contrary, potassium and manganese concentration decreased. Results from the study suggest that the compost studied is a good alternative to peat-based substrates for the production of vegetable seedlings.

Study of biochemical and microbiological parameters during composting of pine and eucalyptus bark

To study the possibility of some residues from pulp and paper industry being used as substrates to produce seedlings in containers, three composting experiments were carried out using eucalyptus bark, pine bark and a mixture (60:40, v:v) of pine bark+eucalyptus bark. Biochemical parameters studied were: acid and alkaline phosphatases, lipase (C10), protease, urease, beta-glucosidase and total cellulases. The microbiological populations of total aerobic bacteria, total fungi, actinomycetes, nitrifying bacteria, cellulolytic bacteria and fungi were also evaluated. At the end of the process physicochemical characterization of composts was also performed. Results showed in general that the highest microbiological populations as well as for enzymatic activities occurred during the thermophilic phase (>40 degrees C) of the process. On the other hand and according to the physicochemical characteristics of composts pine bark is the most appropriate material to be used in the formulation of substrates to produce plants in containers.

Revertants of a Chinese hamster ovary cell mutant with an altered beta-tubulin: evidence that the altered tubulin confers both colcemid resistance and temperature sensitivity on the cell

We recently described the isolation of a mutant Chinese hamster ovary cell (Cmd 4) resistant to the cytotoxic effects of colcemid (Cabral et al., Cell 20:29-36, 1980). This mutant carries an altered beta-tubulin but still grows normally at 37 degrees C. In the present study we found that Cmd 4 is temperature sensitive for growth at 40.3 degrees C. A class of revertants selected for temperature resistance had simultaneously lost colcemid resistance and the altered beta-tubulin. In addition, we isolated a temperature-resistant revertant which carries a further alteration in the mutant beta-tubulin polypeptide. This second alteration appears to make the mutant beta-tubulin incompetent to assemble into microtubules, resulting in a strain which is again colcemid sensitive. These revertant cell lines provide strong evidence that a mutation in beta-tubulin can confer both colcemid resistance and temperature sensitivity on a mammalian cell line. Cellular microtubules studied by indirect immunofluorescence in both mutant and revertant cell lines had an apparently normal distribution at permissive and nonpermissive temperatures, yet mitosis appears to be abnormal in the mutant cell line. We conclude from these studies that incorporation of the altered beta-tubulin into microtubules does not affect their distribution but may affect their function during mitosis.

Organizing a public-sector vasectomy program in Brazil

Although models of high-quality family planning services for men exist in Latin America, few if any have been organized within the complex and resource-constrained national public health systems. This study provides evidence from the Santa Barbara project in southern Brazil showing how vasectomy was introduced into the municipal health system. It demonstrates that once the necessary operational and quality-of-care improvements were in place, and sufficient political and technical support existed to proceed, it was possible to establish low-cost, well-used, and sustainable vasectomy services free of charge. The findings show that careful attention to the development of strong technical competence and an informed choice process resulted in high user satisfaction. Focus-group discussions with men who underwent vasectomy indicate that they had no objection to being served in the context of a women's health center and that they act as opinion leaders who draw an increasing clientele to the service.

Antitumor efficacy of 26-fluoroepothilone B against human prostate cancer xenografts

BACKGROUND

Epothilone compounds (e.g. epothilones A and B) represent a new structural class of microtubule inhibitors with the remarkable ability to inhibit tumor growth of multidrug-resistant cell lines at low nanomolar or even subnanomolar concentrations. Unfortunately, this therapeutic efficacy has only been achieved to date with a narrow therapeutic window. Hence, other structural analogs of compounds such as epothilone B are currently being synthesized in the hope that they will demonstrate equivalent antitumor efficacy with reduced systemic toxicity.

PURPOSE

To evaluate the relative efficacy and toxicity of selectively modified epothilone compounds.

METHODS

Compounds were initially screened for relative cytotoxicity against the human prostate cancer cell lines PC3, LNCaP, MDA PCa 2a and MDA PCa 2b. Growth inhibitory IC50 values of 0.5 to 4 nM were obtained. From this initial screen, one epothilone compound, 26-fluoroepothilone B, was chosen for further evaluation against the growth of s.c.-implanted MDA PCa 2b- and PC3-derived prostate tumors in athymic nude mice. The compound was administered intravenously at 2, 5 and 10 mg/kg after the tumors had reached 300 mm3. Two control groups were used: paclitaxel (40 mg/kg) and saline.

RESULTS

Following treatment with 10 mg 26-fluoroepothilone B/kg, there was a sustained decrease in tumor size for 30 days reaching a maximal reduction of 80% when compared with tumor growth in the saline control group. Sustained suppression (> 20 days) of tumor growth was observed following the second drug injection. Although a maximal body weight loss of 30% occurred after the second injection, all mice completely regained their initial body weight in 20 days. A lower dose (2 mg/kg) produced a 58% maximal reduction in tumor size and a 20% body weight loss. Minimal inhibition of tumor growth, however, was obtained with paclitaxel at a maximally tolerated dose (40 mg/kg). Other epothilones tested were either less effective and/or more toxic than 26-fluoroepothilone B. This new fluorinated epothilone compound supports the growth of paclitaxel-dependent Tax-18 mutant CHO cells and produces microtubule bundles similar to those produced by paclitaxel, indicating that the two drugs share a similar mechanism of action.

CONCLUSION

A new fluorinated epothilone compound, 26-fluoroepothilone B, has been described that stabilizes microtubule structures based on its support of growth of a mutant paclitaxel-dependent CHO cell line. Its antitumor activity against human prostate cancer in nude mice is superior to that of paclitaxel at equivalent toxic doses. Further research is required to determine optimal dosing strategies and to fully assess the compound's activity against other malignant diseases.

Effects of orally active taxanes on P-glycoprotein modulation and colon and breast carcinoma drug resistance

BACKGROUND

The taxane paclitaxel (Taxol) is often of limited efficacy in chemotherapeutic regimens because some cancer cells express high levels of the efflux pump, P-glycoprotein (Pgp), which removes the drug from the cells. The orally active paclitaxel analog IDN-5109 has been reported to overcome Pgp-mediated drug resistance. We tested whether IDN-5109 acts by modulating Pgp activity.

METHODS

Human MDA435/LCC6mdr1 and MDA435/LCC6 breast carcinoma cells, which express and do not express Pgp, respectively, were incubated with [3H]IDN-5109 and paclitaxel to determine intracellular drug accumulation. Flow cytometry was used to analyze intracellular retention of two Pgp substrates, rhodamine 123 (Rh-123) and doxorubicin, in both breast carcinoma cell lines and in human colon carcinoma cells (SW-620, DLD1, and HCT-15, whose Pgp levels vary) treated with different taxanes. The effects of IDN-5109 and paclitaxel on tumor growth in vivo were studied with the use of tumors established through xenografts of Pgp-expressing SW-620 and DLD1 cells in severe combined immunodeficiency mice. All statistical tests were two-sided.

RESULTS

Pgp-expressing cells treated with IDN-5109 or with the taxane-based drug resistance reversal agent tRA96023, which blocks Pgp activity, retained 8.1- and 9.4-fold more Rh-123 (P =.0001), respectively, and 1.7- and 1.9-fold more doxorubicin (P =.001), respectively, than cells treated with paclitaxel. Non-Pgp-expressing cells treated similarly demonstrated no increased retention of either substrate. MDA435/LCC6mdr1 cells retained 5.3-fold more [3H]IDN-5109 than [3H]paclitaxel after 2 hours (P =.01). IDN-5109 showed statistically significantly higher tumor growth inhibition than paclitaxel against the SW-620 xenograft (P =.003).

CONCLUSIONS

IDN-5109 modulates Pgp activity, resulting in superior tumor growth inhibition against Pgp-expressing tumors as compared with paclitaxel. IDN-5109 may broaden the spectrum of taxane use to include colon tumors.

Factors determining cellular mechanisms of resistance to antimitotic drugs

With the rapidly expanding use of paclitaxel and related taxanes to treat malignant diseases, comes the realization that development of resistance to this class of agents will become an increasingly significant clinical problem. Studies have indicated that acquisition of resistance to the cytotoxic action of these drugs can occur by limiting the drug's ability to accumulate in cells, altering the stability of cellular microtubules, diminishing the drug's ability to bind tubulin, or varying the expression of specific tubulin genes. This review will critically evaluate the selection methods used to generate drug resistant mutants in tissue culture and focus on the various factors that determine which resistance mechanisms are most likely to be encountered. It is anticipated that clinical drug resistance will be complicated by pharmacokinetic considerations and variability among individuals, but that underlying genetic mechanisms will be similar to those found in culture.

A beta-tubulin leucine cluster involved in microtubule assembly and paclitaxel resistance

Analysis of beta-tubulin alleles from nine paclitaxel-resistant Chinese hamster ovary cell lines revealed an unexpected cluster of mutations affecting Leu-215, Leu-217, and Leu-228. Six of the mutant alleles encode a His, Arg, or Phe substitution at Leu-215; another mutant allele has an Arg substitution at Leu-217; and the final two mutant alleles have substitutions of His or Phe at Leu-228. Using plasmids that allow tetracycline regulated expression, the L215H, L217R, and L228F mutations were introduced into a hemagglutinin antigen-tagged beta-tubulin cDNA and transfected into wild-type Chinese hamster ovary cells. In all three cases, low to moderate expression of the transfected mutant gene conferred paclitaxel resistance. Higher levels of expression caused disruption of microtubule assembly, cell cycle arrest at mitosis, and failure to proliferate. Consistent with reduced microtubule stability, cells expressing mutant hemagglutinin beta-tubulin had fewer acetylated microtubules than nonexpressing cells in the same population. These data, together with previous studies showing that the paclitaxel-resistant mutant cell lines have less stable microtubules, indicate that the leucine cluster represents an important structural motif for microtubule assembly.

Vinblastine induces an interaction between FtsZ and tubulin in mammalian cells

The Escherichia coli cell division protein FtsZ was expressed in Chinese hamster ovary cells, where it formed a striking array of dots that were independent of the mammalian cytoskeleton. Although FtsZ appears to be a bacterial homolog of tubulin, its expression had no detectable effects on the microtubule network or cell growth. However, treatment of the cells with vinblastine at concentrations that caused microtubule disassembly rapidly induced a network of FtsZ filaments that grew from and connected the dots, suggesting that the dots are an active storage form of FtsZ. Cells producing FtsZ also exhibited vinblastine- and calcium-resistant tubulin polymers that colocalized with the FtsZ network. The FtsZ polymers could be selectively disassembled, indicating that the two proteins were not copolymerized. The vinblastine effects were readily reversible by washing out the drug or by treating the cells with the vinblastine competitor, maytansine. These results demonstrate that FtsZ assembly can occur in the absence of bacterial chaperones or cofactors, that FtsZ and tubulin do not copolymerize, and that tubulin-vinblastine complexes have an enhanced ability to interact with FtsZ.

Overexpression of class I, II or IVb beta-tubulin isotypes in CHO cells is insufficient to confer resistance to paclitaxel

Recent studies have suggested a correlation between increased expression of specific beta-tubulin isotypes and paclitaxel resistance in drug-selected cell lines. In an attempt to establish a causal link, we have transfected Chinese hamster ovary cells with cDNAs encoding epitope-tagged class I, II, and IVb beta-tubulins, as well as a class I beta-tubulin with a mutation previously characterized in a paclitaxel resistant mutant. To eliminate possible toxicity that might be associated with overexpression of non-native tubulin, each of the cDNAs was placed under the control of a tetracycline regulated promoter. All transfected cDNAs produced assembly competent tubulin whose synthesis could be turned off or on by the presence or absence of tetracycline. Production of betaI, betaII, or betaIVb tubulin had no effect on the sensitivity of the cells to paclitaxel, but production of the mutant betaI-tubulin conferred clear resistance to the drug. We conclude from these experiments that simple overexpression of class I, II, or IVb isoforms of beta-tubulin is insufficient to confer resistance to paclitaxel.

Future directions with taxane therapy

The potential biochemical and genetic mechanisms by which a cell might experience a decreased sensitivity to taxanes and other drugs of this class are discussed in the first part of this article. The use of taxanes in the current gynecologic-oncologic clinical setting is reviewed with special consideration given to the pharmacokinetics of taxane in relation to dose intensity and length of administration.

Complete regression of well-established tumors using a novel water-soluble poly(L-glutamic acid)-paclitaxel conjugate

Despite an intensive search, few water-soluble paclitaxel derivatives have been shown to have a therapeutic index superior to paclitaxel itself. We now report a water-soluble poly(L-glutamic acid)-paclitaxel conjugate (PG-TXL) that produces striking antitumor effects with diminished toxicity. A single i.v. injection of PG-TXL at its maximum tolerated dose (defined as that dose that produces a maximum 12-15% body weight loss within 2 weeks after a single i.v. injection) equivalent to 60 mg of paclitaxel/kg and at even a lower dose equivalent to 40 mg of paclitaxel/kg resulted in the disappearance of an established implanted 13762F mammary adenocarcinoma (mean size, 2000 mm3) in rats. (An equivalent dose of PG-TXL is the amount of conjugate that contains the stated amount of paclitaxel.) Similarly, mice bearing syngeneic OCA-1 ovarian carcinoma (mean size, 500 mm3) were tumor-free within 2 weeks after a single i.v. injection of the conjugate at a dose equivalent to 160 mg of paclitaxel/kg. The conjugate has little if any intrinsic tubulin polymerization activity in vitro and is >20 times less potent in supporting the growth of a paclitaxel-dependent CHO mutant cell line. PG-TXL has a prolonged half-life in plasma and greater uptake in tumor as compared with paclitaxel. Furthermore, only a small amount of total radioactivity from PG-[3H]TXL was recovered as free [3H]paclitaxel in either the plasma or the tumor tissue within 144 h after drug injection. Histological studies of tumor tissues obtained from mice treated with PG-TXL show fewer apoptotic cells but more extensive tumor necrosis as compared with paclitaxel treatment. These data suggest that in addition to its role as a carrier for selective delivery of paclitaxel to the tumor, PG-TXL exerts distinct pharmacological actions of its own that may contribute to its remarkable antitumor efficacy.

alpha-Tubulin limits its own synthesis: evidence for a mechanism involving translational repression

A Chinese hamster alpha-tubulin cDNA was modified to encode an 11-amino acid carboxyl-terminal extension containing the immunodominant epitope from influenza hemagglutinin antigen (to create HA alpha 1-tubulin) and was cloned into a vector for expression in mammalian cells. 12 stable CHO cell lines expressing this HA alpha 1-tubulin were isolated and characterized. HA alpha 1-tubulin incorporated into all classes of microtubules, assembled to the same extent as the endogenous tubulin, and did not perturb the growth of the cells in which it was expressed. However, overexpression of HA alpha 1-tubulin strongly repressed the synthesis of endogenous alpha-tubulin while having little or no effect on the synthesis of beta-tubulin. Treatment of transfected cells with sodium butyrate to induce even greater expression of HA alpha 1-tubulin led to a further decrease in synthesis of endogenous alpha-tubulin that was fully reversible upon removal of the inducer. Decreased synthesis of alpha-tubulin in transfected cells did not result from decreased levels of alpha-tubulin mRNA, as demonstrated by ribonuclease protection assays. On the other hand, colchicine, a drug previously shown to destabilize the tubulin message, caused a clear reduction in both protein synthesis and mRNA levels for transfected HA alpha 1-tubulin and endogenous alpha-tubulin, thus indicating that the decreased alpha-tubulin synthesis observed as a result of HA alpha 1-tubulin overexpression is distinct from the previously described autoregulation of tubulin. The results are consistent with a mechanism in which free alpha-tubulin inhibits the translation of its own message as a way of ensuring stoichiometric synthesis of alpha- and beta-tubulin.

Inhibition of Cholesteatoma Migration in vitro with all-Trans Retinoic Acid

Retinoids have recently become of interest to clinicians because of their ability to inhibit migration and proliferation of premalignant squamous cells while enhancing growth and proliferation of normal cells. An in vitro investigation was undertaken to determine whether retinoic acid exhibits similar inhibitory effects on cholesteatoma cells. Cholesteatoma specimens were obtained intraoperatively from 10 patients undergoing mastoidectomy or revision mastoidectomy for chronic ear disease. Cholesteatoma explant growth and en mass migration were observed daily, and topographic maps were constructed at various time intervals to quantify rate and direction of expiant migration in the presence or absence of all- trans retinoic acid. Before all- trans retinoic acid administration, explants migrated very rapidly (1 to 2 mm/day). A maximum threefold inhibition of migratory rate occurred, with explants exposed to 0.1 μmol/L retinoic acid when compared with controls. A sixfold maximum inhibition was observed at higher retinoic acid concentrations (5 μmol/L). On removal of all- trans retinoic acid, twofold and fourfold increases in migratory rates were observed. The direction of explant migration varied significantly for long periods of time and appeared not to be affected by retinoic acid. This investigation suggests that all- trans retinoic acid has an inhibitory effect on cholesteatoma cell migration. Retinoids may have a role in controlling cholesteatoma disease in the future.

Significant divergence in nucleotide sequences for beta-tubulin from different laboratory strains of Chinese hamster ovary cells

The nucleotide sequences for isotype 1 beta-tubulin cDNAs cloned from different laboratory strains of Chinese hamster ovary (CHO) cells were compared and found to contain an unexpected number of sequence differences in both translated and untranslated regions of the gene. The results indicate significant changes in the DNA, but not protein, sequence while the cells have been in culture and reveal sequences in the 5' and 3' untranslated regions that have resisted these changes.

Overexpression of an epitope-tagged beta-tubulin in Chinese hamster ovary cells causes an increase in endogenous alpha-tubulin synthesis

A Chinese hamster beta-tubulin cDNA, engineered to express a 9 amino acid epitope from the influenza hemagglutinin antigen (HA), was transfected into Chinese hamster ovary (CHO) cells. The recombinant protein (HA beta 1-tubulin) appeared to behave normally by the following criteria: immunofluorescence indicated that HA beta 1-tubulin incorporated into all classes of interphase and spindle microtubules as well as microtubule organizing centers. The sensitivity of the cells expressing HA beta 1-tubulin to Colcemid and taxol was unchanged. A 210 kD microtubule associated protein (MAP) remained associated with microtubules that incorporate HA beta 1-tubulin. The synthesis of both endogenous beta-tubulin and HA beta 1-tubulin was repressed by colchicine. The HA beta 1-tubulin incorporated into microtubules to the same extent as the endogenous beta-tubulin, and the overall extent of microtubule assembly in transfected cells was unchanged. Finally, transfected cells had normal growth rates and morphologies. When effects on endogenous tubulin production were measured, it was found that expression of the HA beta 1-tubulin reduced the synthesis of endogenous wild-type beta-tubulin but increased the synthesis of alpha-tubulin. At steady state, a small increase in total tubulin consistent with the increased synthesis of alpha-tubulin was found. The results indicate that expression of excess exogenous beta-tubulin perturbs the synthesis of endogenous alpha-tubulin in a manner that is not easily explained by current models of tubulin regulation. The changes in tubulin synthesis along with degradation of excess tubulin subunits may reflect mechanisms that exist to ensure coordinate levels of alpha- and beta-tubulin for assembly.

[Chronic phase of Chagas disease. Clinical aspects and course of the disease]

PURPOSE

To evaluate the clinical and evolutive aspects of chronic chagasic patients.

METHODS

Three hundred chronic chagasic patients, 180 females, with age ranging from 19 to 81 years (55.6 +/- 13.1) were retrospectively studied. Patients were divided according to the following clinical types: indeterminated, cardiac (with the subtypes: arrhythmogenic, dilated and mixed), digestive isolated and digestive plus cardiac involvement. The following variables were analysed: prevalence of each clinical forms, symptoms, electrocardiographic pattern and clinical outcome.

RESULTS

At the start of the study, 73 (24.3%) patients were in indetermined type, 106 (35.3%) in cardiac arrhythmogenic, 95 (31.6%) in mixed, 7 (2.3%) in dilated, 16 (5.3%) in digestive plus cardiac type and 3 (1%) in the pure digestive type. The most prevalent symptoms were dyspnea on efforts (57%), palpitations (41.33%) and chest pain (33%). The most frequent electrocardiographic pattern was right bundle branch block plus antero-superior fascicular block, in 30% of the patients. The average follow-up time was 7.8 +/- 6.1 years and the outcome was considered good in 20 patients (6.6%), stable in 214 (71.3%) and bad in 66 (23%). At the end of the follow-up, 9 patients have evaluated from the indeterminated to the cardiac and digestive types, and 19 (17.92%), from the arrhythmogenic to mixed cardiac subtype. The follow-up was lost in 79 patients (26.3%), most of them, probably dead.

CONCLUSION

With a mean time of 7.8 years, 12.3% of the patients in the indeterminated type evolved to the cardiac and/or digestive type; right brundle branch block with antero-superior fascicular block was the most prevalent electrocardiographic pattern; the outcome was stable or good in the majority of these patients.

Stable expression of heterologous microtubule-associated proteins (MAPs) in Chinese hamster ovary cells: evidence for differing roles of MAPs in microtubule organization

To study the effects of microtubule-associated proteins (MAPs) on in vivo microtubule assembly, cDNAs containing the complete coding sequences of a Drosophila 205-kD heat stable MAP, human MAP 4, and human tau were stably transfected into CHO cells. Constitutive expression of the transfected genes was low in most cases and had no obvious effects on the viability of the transfected cell lines. High levels of expression, as judged by Western blots, immunofluorescence, and Northern blots, could be induced by treating cells with sodium butyrate. High levels of MAPs were maintained for at least 24-48 h after removal of the sodium butyrate. Immunofluorescence analysis indicated that all three MAPs bound to cellular microtubules, but only the transfected tau caused a rearrangement of microtubules into bundles. Despite high levels of expression of these exogenous MAPs and the bundling of microtubules in cells expressing tau, transfected cells had normal levels of assembled and unassembled tubulin. With the exception of the tau-induced bundles, microtubules in transfected cells showed the same sensitivity as control cells to microtubule depolymerization by Colcemid. Further, all three MAPs were ineffective in reversing the taxol-dependent phenotype of a CHO mutant cell line. The absence of a quantitative effect of any of these heterologous proteins on the assembly of tubulin suggests that these MAPs may have different roles in vivo from those inferred previously from in vitro experiments.

Estramustine depolymerizes microtubules by binding to tubulin

To investigate the mechanism of action of the antineoplastic drug estramustine, we compared its effects on human prostate cancer cells with those of vinblastine. At their respective concentrations that result in 50% inhibition of clonogenic growth, both drugs caused an accumulation of cells blocked at mitosis and similar dose- and time-dependent depolymerization of interphase microtubules. Also, colcemid-resistant and colcemid-hypersensitive Chinese hamster ovary cells with tubulin mutations were collaterally cross-resistant or -sensitive to estramustine. Thus, the cytotoxicity of estramustine is due to its microtubule depolymerization properties. This could be caused by interaction with tubulin and/or with microtubule-associated proteins (MAPs). Previous investigations have shown that high concentrations of estramustine phosphate can inhibit microtubule polymerization in vitro by binding to MAPs. However, estramustine phosphate is the clinical prodrug to estramustine, the intracellular active compound. In this study, we investigated the effects of estramustine on the binding of MAPs to taxol-stabilized microtubules in vivo. In contrast to previous reports, no effect of estramustine on the binding of MAPs to microtubules was found. Furthermore, we found that polymerization of purified tubulin could be inhibited by estramustine in vitro. Taken together, these results demonstrate that estramustine causes depolymerization of microtubules by direct interaction with tubulin.

Use and environmental implications of pulp-mill sludge as an organic fertilizer

Pulp-mill sludge is an industrial by-product with a high level of organic matter, which is eventually biodegradable. Since there are few alternatives for its practical use, its utilization as an agricultural fertilizer is proposed. An experiment was carried out during 2 years, with yellow lupin plants (Lupinus luteus L.), in order to define the critical application levels of this material. Biodegradability of the sludge in the soil was also evaluated, as well as its pollutant effects. Results obtained in the first year of the experiment showed that an application rate larger than 50 t ha(-1) of pulp-mill sludge, has a depressive effect on yield. Yet, this effect is completely dissipated in the second year. Finally, it is concluded that, if the use of this organic waste as an agricultural fertilizer is adequately monitored, soil pollution problems should not occur.

[Civil aviation and cardiology. Admission rules and follow-up of the technical flying personnel of TAP-Air Portugal]

The authors, based in European and American rules, consensus positions of Clinical Aerospace Congresses and their own experience, marked admission and follow-up rules of conduct for TAP Air Portugal aircrew. They stressed the importance of modern technology in arterial pressure ambulatory diagnosis and pointed the necessity of arterial pressure treatment in the other cardiovascular risk factors context. They relief ischemic myocardial disease because it is incompatible with flying safety, even in those submitted to coronary angioplasty or bypass graft surgery. For those with arrhythmias, valvular heart disease, myocarditis, cardiomyopathy and adult life congenital heart disease, we emphasize admission and follow-up rules.

Resistance to antimitotic agents as genetic probes of microtubule structure and function

Much of our knowledge about microtubules has come from detailed morphological, biochemical, and cell biological studies. As more is learned about these organelles, questions regarding the in vivo regulation of their expression and function become increasingly important. Genetics provides an approach to address these more subtle questions in the living cell. Mammalian mutants with microtubule alterations have been isolated using selections for resistance to the cytotoxic effects of a number of antimitotic drugs. A subset of these mutants have clearly defined alterations in alpha- or in beta-tubulin, and these have been used to explore the mechanisms by which mammalian cells acquire resistance to this class of drugs. In addition, the mutants are providing valuable insights into how tubulin expression is regulated, into what factors determine the extent of microtubule assembly in living cells, into the domains of tubulin that are involved in assembly, and into the role of microtubules in essential cellular processes.

Resistance to antimitotic drugs in Chinese hamster ovary cells correlates with changes in the level of polymerized tubulin

A sensitive and reproducible method to measure relative levels of polymerized and soluble tubulin in cells has been developed. This method involves metabolically labeling cells with radioactive amino acids followed by lysis in a microtubule-stabilizing buffer, centrifugation to separate soluble from polymerized tubulin, resolution of the proteins in each fraction by two-dimensional gel electrophoresis, and quantitation of the tubulin by liquid scintillation counting of spots excised from the gel. Several buffers were evaluated for their reproducibility and efficacy in preserving the state of in vivo microtubule assembly at the time of cell lysis, and the ability of the technique to measure drug-induced changes in tubulin polymerization was determined. Results using this method indicate that Chinese hamster ovary cells maintain approximately 40% of the cellular tubulin in an assembled form. Dose-dependent decreases in tubulin polymerization could be measured in Colcemid-treated cells, while dose-dependent increases in assembly were measured in taxol-treated cells. The results with taxol indicate that, following the increase in microtubule polymerization, there is a time-dependent bundling of microtubules that occurs without further increases in the extent of tubulin assembly. Examination of drug-resistant Chinese hamster ovary cells reveals that Colcemid-resistant mutants maintain more tubulin in the polymerized state (approximately 50%), while taxol-resistant mutants maintain less assembled tubulin (about 28%). Similar changes occur regardless of whether the mutant cells have an alteration in alpha- or in beta-tubulin. A model to explain these results is discussed.

Alterations in microtubule assembly caused by the microtubule-active drug LY195448

LY195448 is an experimental drug that blocks cells at metaphase (Boder et al.: Microtubules and Microtubule Inhibitors 1985: 353-361, 1985). A 4 hour exposure of NRK cells to a drug concentration of 46 microM (15 micrograms/ml) increased the number of mitotic cells in the population from 4.9% to 18.5%. Examination of treated cells by immunofluorescence showed increased numbers of cells blocked at prometaphase, with short microtubules extending from the spindle pole to the kinetochores. The cytoskeleton of interphase cells remained intact at these concentrations. However, the number of microtubules appeared to be reduced, and those that remained appeared kinkier and curled, particularly toward the periphery of the cells. When cytoskeletal microtubules of NRK cells were depolymerized with nocodazole, they reassembled within minutes of transfer to drug-free media. However, nocodazole-treated cells transferred to fresh media containing 15 micrograms/ml of LY195448 required 2-3 times longer to reassemble cytoplasmic microtubules. Previously isolated Chinese hamster ovary cell microtubule mutants resistant to either taxol or Colcemid were tested for cross-resistance to this drug. Cell lines resistant to the depolymerizing drug Colcemid exhibited increased resistance to LY195448 compared to wild-type cells, whereas taxol resistant cell lines were more sensitive. Of eleven newly isolated mutant CHO cell lines selected for increased resistance to LY195448, seven exhibited an altered beta-tubulin protein by two-dimensional polyacrylamide gel electrophoresis. These 11 cell lines also showed a heterogenous pattern of resistance to several microtubule-active drugs. These data demonstrate that LY195448 is cytotoxic to mammalian cells because it inhibits microtubule assembly, most likely through a direct interaction with tubulin.

Identification of methionine-containing tryptic peptides of unstable beta-tubulin separated by reverse-phase high-performance liquid chromatography

Methods for examining altered regions in unstable mutant proteins are described. The strategy is illustrated using assembly defective Chinese hamster beta-tubulin subunits that are rapidly degraded in the cell. These unstable proteins are metabolically labeled to high specific activity and isolated as spots on two-dimensional gels. Conditions for the generation of tryptic peptides from gel pieces containing beta-tubulin and their subsequent resolution by HPLC have been worked out. Through a combination of dual labeling with various tritiated amino acids and [35S]methionine as well as partial sequence analysis, the identification of several HPLC peaks with the known sequence of beta-tubulin has been accomplished. This technique should greatly aid attempts to map the sites of mutational alterations in beta-tubulin polypeptides, and the general strategy should be readily applicable to other mutant proteins.

Mechanisms by which mammalian cells acquire resistance to drugs that affect microtubule assembly

The development of resistance in mammalian cells to toxic drugs is a significant clinical problem, especially in cancer chemotherapy where drug-resistant tumor cells often prove to be refractory to treatment. In this article, we review some of the basic mechanisms of drug resistance from the perspective of a single cell bathed in medium containing the drug. These mechanisms may be categorized according to changes in the cell that affect the ability of the drug to accumulate intracellularly, changes in enzymes that are required for drug toxicity, alterations in trapping of the drug or detoxification of the drug, alterations in binding to an intracellular target, or alterations in cellular processes that compensate for the action of the drug. This latter mechanism is illustrated in some depth by discussing mutants of Chinese hamster ovary cells that are resistant to the effects of drugs that interfere with microtubule assembly.

Expression and function of beta-tubulin isotypes in Chinese hamster ovary cells

The availability of isotype-specific antisera for beta-tubulin, coupled with genetic and biochemical analysis, has allowed the determination of beta-tubulin isotype expression and distribution in Chinese hamster ovary (CHO) cells. Using genetic manipulations involving selection for colcemid resistance followed by reversion and reselection for drug resistance, we have succeeded in isolating cell lines that exhibit three major and one minor beta-tubulin spots by two-dimensional gel electrophoresis. In concert with isotype-specific antibodies, analysis of these mutants demonstrates that CHO cells express two copies of isotype I, at least one copy of isotype IV, and very small amounts of isotype V. All three isotypes assemble into both cytoplasmic and spindle microtubules and are similar in their responses to cold, colcemid, and calcium-induced depolymerization. They have comparable turnover rates and are equally sensitive to depression of synthesis upon colchicine treatment. These results suggest that beta-tubulin isotypes are used interchangeably to assemble microtubule structures in CHO cells. However, of 18 colcemid-resistant mutants with a demonstrable alteration in beta-tubulin, all were found to have the alteration in isotype I, thus leaving open the possibility that subtle differences in isotype properties may exist.

Elimination of permeability mutants from selections for drug resistance in mammalian cells

Chinese hamster ovary (CHO) cells exhibit increased sensitivity to a wide variety of microtubule inhibitory drugs when verapamil is present in the growth medium. The extent of this increased sensitivity is drug specific: some drugs such as taxol and vinblastine respond greatly to the presence of verapamil, whereas other drugs such as griseofulvin respond very poorly. For the majority of drugs examined, however, a 2- to 10-fold increase in drug sensitivity is observed in the presence of verapamil at 5 micrograms/ml. The effects of verapamil are even more dramatic when drug-resistant mutant cells with a presumed alteration in membrane permeability are examined. In the presence of appropriate levels of verapamil, these mutants demonstrate a level of drug sensitivity comparable to that of the wild-type parental cells. Drug-resistant cells from similar selections but with well-defined alterations in alpha- or beta-tubulin and no evidence of alterations in membrane permeability, however, continue to exhibit increased resistance to the selecting drug even in the presence of verapamil. These studies support the conclusion that verapamil affects the membrane permeability to or transport of a wide variety of hydrophobic drugs. In addition, we have used this information to devise selections that virtually eliminate the isolation of drug-resistant permeability mutants. This methodology should be generally applicable to genetic studies of drug action that are complicated by the isolation of large numbers of mutants with permeability alterations.

Contact sensitivity to oak moss

Oak moss allergy was the principle allergen in contact sensitivity to perfumes (45%); 31 patients reacting to oak moss were studied. The sensitivity was attributed to contact with perfumes in 20, lichens in 7 and unknown in 4. Atranorin was the most frequent allergen, followed by usnic, evernic and fumarprotocetraric acids. Concomitant allergy occurred to several lichen acids and also to balsam of Peru, colophony and other fragrance components.

Mutations affecting assembly of beta-tubulin localize to a region near the carboxyl terminus

The generation of Chinese hamster ovary cell lines that express assembly defective forms of beta-tubulin were isolated using selections based on reversion of conditional lethal or drug resistance phenotypes. Two such cell lines, D2 and 6H3, were chosen for further characterization because they contain beta-tubulin polypeptides that exhibit decreases in apparent molecular weight on two-dimensional gel electrophoresis. Analysis of the nucleic acid from these cell lines using both Southern and Northern procedures suggests a deletion in one of the beta-tubulin genes in each cell line. Localization of the missing sequence in D2 was first determined by tryptic peptide mapping by high performance liquid chromatography. Subsequently, the assignment was confirmed by constructing appropriate subclones of a wild type Chinese hamster ovary beta-tubulin cDNA for Southern analysis to demonstrate a failure to recognize characteristic hybridization patterns of the mutant tubulin gene. In the other revertant, 6H3, the deletion was detected on a Northern blot by differential hybridization of a 3' fragment of the cDNA to the beta-tubulin messages. The results indicate that D2 has an internal deletion whose approximate limits extend from amino acid residues 250 through 345. Cell line 6H3 has a deletion that begins near amino acid residue 330 and extends into the 3'-untranslated region of the gene.