Wide volume versus helical acquisition using 320-detector row computed tomography for computed tomography urography in adults.

PURPOSE: To evaluate the best collimation used in wide volume (WV) mode to cover the abdomen in computed tomography (CT) urography in terms of radiation dose and image quality. MATERIALS AND METHODS: This study was performed on a 320×0.5mm detector row CT unit. The first part identified the lowest volume CT dose index (CTDIvol) by using the topograms data of 25 medium size patients (13 men and 12 women; mean age: 52±9 [SD] years; age range: 46-68 years) using different collimations on WV from 6cm to 16cm and the one of the helical mode for the same coverage length. The second part consisted of a clinical evaluation of this result including 45 medium size patients (32 men and 13 women; mean age: 68±14 [SD] years; age range: 45-72 years). The qualitative evaluation included several items based on a 5-point Likert scale. RESULTS: The first part of the study indicated that a collimation of 10cm (200×0.5mm) in WV mode with 5 volumes had the lowest CTDIvol (2.78±0.35mGy; range: 2.35-3.21mGy) compared to helical mode (4.38±0.48mGy, range: 3.75-4.95mGy). In the second part, the mean radiation dose reduction by comparison with helical mode was 44.03%±0.36% (P<0.001) and 51.16%±1.22% (P<0.005) for CTDIvol and DLP, respectively. CONCLUSION: Wide volume mode of the abdomen can be performed with a significant radiation dose reduction with a collimation of 10cm (200×0.5mm) and five volumes.

[Temporary localized alopecia following neuroradiological procedures: 18 cases]. / Alopécie circonscrite temporaire après neuroradiologie interventionnelle : une série de 18 cas.

BACKGROUND: The treatment of cerebral lesions using endovascular radiological procedures is becoming a standard of care. Radiation-induced alopecia, a type of acute radiodermatitis, is a frequent complication. Between 2009 and 2010, a number of patients reported hair loss after embolization of a cerebral arteriovenous malformation at the Neuroradiology Department of the Strasbourg University Hospital. We therefore retrospectively investigated 18 cases to better delineate the circumstances and the risk factors associated with radiation-induced alopecia. PATIENTS AND METHODS: We reviewed the records of 35 patients reporting hair loss among the 347 patients undergoing embolization of cerebral arteriovenous malformations between January 2008 and May 2010. Only patients with photographically documented complete circumscribed alopecia were included. Patients were examined and interviewed by a dermatologist and/or a radiologist at the time of hair loss and at a later point. The cumulative dose of radiation delivered to the skin in the 3 months preceding onset of alopecia, then over the entire period 2008-2010, was calculated. These doses included the diagnostic (angiography) and therapeutic (embolization) procedures. RESULTS: Definite circumscribed alopecia was noted in 18 patients. Alopecia occurred between two and four weeks after embolization; it was complete and in no cases cicatricial. Complete recovery as attested by examination or photography was observed in 12 patients. The cumulative dose over the preceding three months was between 2.5 Gy and 12.3 Gy (mean: 5 Gy). The total cumulative dose since January 2008 was between 3.2 and 17 Gy (mean: 7 Gy). DISCUSSION: We describe a series of 18 patients with radio-induced alopecia occurring after diagnostic and therapeutic procedures for cerebral arteriovenous malformations. This series is particularly interesting because it includes the largest patient sample reported to date with an uncommon large area of alopecia, and also because we were able to calculate the cumulative dose of radiation delivered to the skin. In addition, we underline the importance of the cumulative dose in interventional radiology since radio-induced alopecia probably results from the number of interventional procedures during a given time period. Moreover, analysis of these doses provided us with a new perspective on the radiobiology of the hair growth cycle. Indeed, whereas previously reported data considered alopecia as definitive where doses higher than 7 Gy were delivered, we noticed regrowth of hair with doses of up to 12 Gy. CONCLUSION: These observations underline the specific findings of radiation-induced alopecia and underline the importance of the cumulative radiation dose delivered during the 3 months preceding alopecia.

What is biocompatibility?: a new definition based on the latest technology.

Biomaterials have been evolving for a number of decades, and it is about time that better categorizations of biocompatibility were devised to describe them. At least that is the view of Buddy Ratner, professor of bioengineering and chemical engineering, and Michael L. and Myrna Darland Endowed Chair in Technology Commercialization at the University of Washington, as well as director of University of Washington Engineered Biomaterials (UWEB), the university's engineered biomaterials program.

Biocompatible medical devices: raise the bar for health care.

From pacemakers to hip replacements, sophisticated sensors to catheters, medical devices are helping millions of patients live far better and even much longer lives. The possibilities are nearly endless, provided the new devices are biocompatible. In other words, they must not have harmful consequences for the patient, but they must also play some role and function well within the immensely complicated and not completely understood human body.

Multifaceted biomaterials extend to multiple uses: new developments in biocompatibility.

In research laboratories around the world, scientists and engineers are taking newly reported insights about how the human body works, contributing new insights themselves, and then combining that new knowledge with innovative approaches to materials development. The result is a collection of biomaterials that promise to make a vast range of medical devices biocompatible and to increase the level of biocompatibility of those devices that are already considered biocompatible.

A view from the outside in.

This paper discusses the use of imaging modalities such as CT, MRI and ultrasound imaging in intervention therapy, surgery and drug delivery. The paper points how these image-guided therapies are quickly becoming a foundation of medical care.

Genetic structure, introgression, and a narrow hybrid zone between northern and California spotted owls (Strix occidentalis).

The northern spotted owl (Strix occidentalis caurina) is a threatened subspecies and the California spotted owl (Strix occidentalis occidentalis) is a subspecies of special concern in the western United States. Concern for their continued viability has arisen because of habitat loss caused by timber harvesting. The taxonomic status of the northern subspecies has been the subject of continuing controversy. We investigated the phylogeographical and population genetic structure of northern and California spotted owls with special reference to their region of contact. Mitochondrial DNA (mtDNA) control region sequences confirmed the existence of two well-differentiated lineages connected by a narrow hybrid zone in a region of low population density in north central California. Maximum-likelihood estimates indicated bidirectional gene flow between the lineages but limited introgression outside the region of contact. The lengths of both the mtDNA hybrid zone and the reduced density patch were similar and slightly exceeded estimates of natal dispersal distances. This suggests that the two subspecies were in secondary contact in a hybrid zone trapped by a population density trough. Consequently, the zone of interaction is expected to be geographically stable. We discovered a third, rare clade of haplotypes, which we interpreted to be a result of incomplete lineage sorting; those haplotypes result in a paraphyletic northern spotted owl with respect to the California spotted owl. A congeneric species, the barred owl (Strix varia), occasionally hybridizes with spotted owls; our results indicated an upper bound for the frequency of barred owl mtDNA haplotypes in northern spotted owl populations of 3%.

Evaluation of the use of six diagnostic X-ray spectra computer codes.

A knowledge of photon energy spectra emitted from X-ray tubes in radiology is crucial for many research domains in the medical field. Since spectrometry is difficult because of high photon fluence rates, a convenient solution is to use computational models. This paper describes the use of six computer codes based on semiempirical or empirical models. The use of the codes was assessed, notably by comparing theoretical half value layers and air kerma with measurements on five different X-ray tubes used in a research hospital. It was found that three out of the six computer codes give relative spectra very close to those produced by X-ray units equipped with constant potential generators: the mean difference between measured and modelled half value layer was less than 3% with a standard deviation of 3.6% whatever the tube and the applied voltage. Absolute output is less accurate: for four computer codes, the mean difference between the measured and modelled air kerma was between 18% and 36%, with a standard deviation of 9% whatever the tube (except for the single phase generator) and the applied voltage. One of the codes gives a good output and beam quality for X-ray units equipped with 100% ripple voltage generators. The use of computational codes as described in this paper provides a means of modelling relative diagnostic X-ray spectra, the usefulness of the tube output data depending on the accuracy required by the end user.

Feasibility of a semiconductor dosimeter to monitor skin dose in interventional radiology.

The design and preliminary test results of a semiconductor silicon dosimeter are presented in this article. Use of this dosimeter is foreseen for real-time skin dose control in interventional radiology. The strong energy dependence of this kind of radiation detector is well overcome by filtering the silicon diode. Here, the optimal filter features have been calculated by numerical Monte Carlo simulations. A prototype has been built and tested in a radiological facility. The first experimental results show a good match between the filtered semiconductor diode response and an ionization chamber response, within 2% fluctuation in a 2.2 to 4.1 mm Al half-value layer (HVL) energy range. Moreover, the semiconductor sensor response is linear from 0.02 Gy/min to at least 6.5 Gy/min, covering the whole dose rate range found in interventional radiology. The results show that a semiconductor dosimeter could be used to monitor skin dose during the majority of procedures using x-rays below 150 keV. The use of this device may assist in avoiding radiation-induced skin injuries and lower radiation levels during interventional procedures.

Paper-based archiving of mammalian and plant samples for RNA analysis.

The ability to archive biological samples for subsequent nucleic acid analysis is essential for tissue specimens and forensic samples. FTA Card is a chemically treated filter paper designed for the collection and room temperature storage of biological samples for subsequent DNA analysis. Its usefulness for the preservation of biological samples for subsequent RNA analysis was tested. Here, we demonstrate that RNA in biological samples stored on FTA Cards is stable and can be used successfully for RT-PCR and northern blot analysis. RNA stability depends on the storage temperature and the type of biological specimen. RNA in mammalian cells stored on FTA Cards is stable for over one year at temperatures at or below -20 degrees C and for two to three months in samples stored at room temperature. For plant leaf, longer storage times (> 5 days) require temperatures at or below -70 degrees C following sample application. FTA Cards may constitute a method not only for convenient collection and storage of biological samples but also for rapid RT-PCR analysis of tissue and cell samples.

Intrarater and interrater reliability of the MS functional composite outcome measure.

OBJECTIVE: To assess practice effects, and intrarater and interrater reliability of the MS functional composite (MSFC) outcome measure. BACKGROUND: To address the poor reliability and insensitivity to change of available MS clinical rating scales, the National MS Society's Clinical Outcomes Assessment Task Force developed the MSFC, a multidimensional quantitative clinical outcome measure that includes tests of leg function/ambulation (Timed 25-Foot Walk), arm function (Nine-Hole Peg Test), and cognitive function (Paced Auditory Serial Addition Test). METHODS: Ten patients with secondary progressive MS underwent six testing sessions over a 2-week period. The MSFC was administered by the same examining technician in the first five sessions and by the other technician in the sixth. Patients were reassessed by both technicians after 6 months (sessions 7 and 8). The MSFC score was calculated as the mean of the Z scores of the three components. A pooled dataset derived from secondary progressive MS patients in the placebo arms of previous clinical trials and natural history studies served as the reference population to standardize scores. RESULTS: Practice effects were evident initially but stabilized by the fourth administration. The intraclass correlation coefficient (ICC) was 0.97 for the MSFC for session 4 versus session 5 (intrarater reliability). The ICC was 0.95 for session 5 versus session 6 (interrater reliability), and was 0.96 for session 7 versus session 8 when patients were reassessed 6 months later. CONCLUSIONS: The MS functional composite (MSFC) outcome measure had excellent intrarater and interrater reliability when standardized procedures were used to train examining technicians and to assess patients. Prebaseline testing sessions should be included in clinical trials employing the MSFC to compensate for practice effects.

[Subareolar injection of 99m-Tc sulfur colloid for sentinel nodes identification in multifocal invasive breast cancer]. / Injection sous-aréolaire de sulfocolloïdes technétiés pour l'identification des ganglions sentinelles dans les cancers du sein invasifs à foyers multiples.

The objective were to study the relevance of the subareolar injection for sentinel node [SN] detection in multiple foci breast cancer. Seventy-nine patients with infiltrative breast carcinoma (diagnosed pre-operatively by core biopsy) and a mean age of 55 (31-78) years were enrolled. All patients were free of previous homolateral surgery, chemotherapy, locoregional radiotherapy or prevalent axillary lymph node. Using four 0.1 ml injections of 1.8 MBq, the technetium-99m 100 nm filtered sulfur colloid was injected by subareolar way (group I) in 16 cases of radiologically cancer with multiple invasive foci and 31 cases of radiologically unifocal cancer, and by peritumoral way (group II) in 32 cases of radiologically unifocal cancer. Scintigrams were obtained 2 to 4 hours after the injections and radioactive nodes were detected peroperatively 18 hours after the injection by intraoperative detection probe. Individual removal of all radioactive nodes was followed by axillary dissection at levels I and II of Berg including Rotter area control. All sentinel nodes were submitted to standard histopathological analysis on serial sections at 500 mu intervals completed by immunohistochemistry for cytokeratin on negative SN. SN were detected by scintigrams in 85% and 88% of the cases of group I and group II respectively, but in 98% and 97% of the cases of respectively both groups by intraoperative probe. Group I was composed of 69% ductal, 22% lobular and 9% tubular carcinomas, and group II of 87% ductal, 10% lobular and 3% tubular carcinomas. Seven and 5 radiologically unifocal tumors were in fact with multiple invasive foci at histology in groups I and II respectively. The complete scintigraphic procedure permitted the detection of a mean number of 2.7 (1-7) SN in group I and 2.3 (1-4) in group II (NS). In group I, the SN were metastatic in 22 patients (48%), 15 of them with the metastases being restricted to the SN, whereas in group II, the SN were metastatic in 9 patients (28%), 5 of them with the positivity restricted to the SN. No false negative result (SN negative and other axillary nodes positive) was observed in group I and only one false negative result in group II which was related to a cancer with histological multiple invasive foci. Sensitivities were 100% and 90%, and negative predictive values were 100% and 95%, for groups I and II respectively. Subareolar injection of radiocolloid allows identification of SN in cases of unifocal and multiple cancer. The mean number of SN detected by the subareolar method is not significantly different, although higher, to that detected by peritumoral injection.

Hepatitis-associated aplastic anemia and acute parvovirus B19 infection: a report of two cases and a review of the literature.

Hepatitis-associated aplastic anemia is rare in general, but occurs in up to 28% of patients receiving liver transplantation for fulminant non-A, non-B hepatitis. Cases are commonly young men with mild hepatitis but severe aplastic anemia. Although cases have been reported in association with hepatitis A, B, and C, most appear to be due to a non-A-B-C virus. We report two cases of acute hepatitis subsequently complicated by marrow hypoplasia in patients with acute parvovirus B19 infection. Hepatic manifestations of parvovirus B19 infection range from liver chemistry abnormalities to fulminant hepatic failure and aplastic anemia. Our cases demonstrate a less severe form of hepatitis-associated aplastic anemia, and together with other data, suggest that parvovirus B19 is at least one cause of hepatitis-associated aplastic anemia, and may be a heretofore underrecognized hepatotrophic virus.

Myocardial perfusion and function imaging at rest with simultaneous thallium-201 and technetium-99m blood-pool dual-isotope gated SPECT.

UNLABELLED: We present a simultaneous gated SPECT (G-SPECT) dual-isotope technique using 201Tl for perfusion and 99mTc blood-pool labeling for function imaging. METHODS: Seventeen patients (13 with previous myocardial infarction, MI) and a control group of three normal volunteers were investigated. They received, 15 min after a 201Tl stress/redistribution protocol with reinjection, 900-950 MBq 99mTc-HSA for blood-pool labeling. Eight frames per R-R interval were recorded in the G-SPECT mode with three windows: window A with 20% centered at 71 keV for 201Tl, window B with 10% centered at 105 keV for Tc scatter contamination and window C centered at 140 keV with 20% for 99mTc. Nongated, crosstalk-corrected 201Tl SPECT perfusion images were reconstructed according to normalized projection-by-projection subtraction from data from windows A and B. G-SPECT data from window C were reconstructed with the same reconstruction limits to allow topographic correlations of left ventricular perfusion and wall motion abnormalities. Polar maps of perfusion and function were used to divide the myocardium into 20 segments. Perfusion was expressed as the percentage of thallium uptake and function corresponding to diastolic to systolic shortening normalized by end diastolic volume. RESULTS: Segmental comparison of uncontaminated-to-contaminated and corrected 201Tl patient images demonstrated an overall agreement score of 93%, with a kappa statistic of 0.76 +/- 0.06 when normal perfused segments were excluded. Segmental matching of perfusion against function at rest showed no correlation for the 10 patients with preserved ejection fraction of 59% +/- 8% nor for the control group. For the remaining seven patients with an ejection fraction of 34% +/- 10%, there was linear correlation between perfusion and function (r2 = 0.61). CONCLUSIONS: The feasibility of dual TI-Tc G-SPECT was examined at rest and suggests low perfusion hypokinesis that matches linear dependence for CAD patients with low ejection fraction.

Pilot study of antithymocyte globulin in systemic sclerosis.

OBJECTIVE: Between June 1, 1992 and August 31, 1994 we conducted an open pilot study of antithymocyte globulin (ATGAM; Upjohn, Kalamazoo, MI) in 10 patients with early systemic sclerosis (SSc) to assess whether this agent might prevent the progression of cutaneous and pulmonary involvement in this disease. METHODS: Adult patients with early SSc (< 3 years) and evidence of progressive skin and pulmonary disease were enrolled. All patients were hospitalized and received a single course of intravenous ATGAM, at a dosage of 10 mg/kg over 4 hours, on 5 consecutive days. Patients were followed up at weeks 1, 2, 3, and 4, and months 2, 4, 6, and 12. Patients were considered to be improved if the Rodnan skin score decreased > or = 25%, to be worse if the skin score increased > or = 25%, and to be not improved if the skin score was within 25% of baseline. For pulmonary involvement, patients were considered to be improved if either the diffusing capacity for carbon monoxide or the forced vital capacity was increased > or = 10%, worse if decreased by > or = 10%, and stable if within 10% of baseline. RESULTS: Most patients tolerated the treatment well, although 1 patient developed an allergic reaction necessitating discontinuation of treatment, 1 developed a serum sickness reaction after completion of therapy, and 1 developed a central venous access-related axillary vein thrombosis. Two patients died of SSc-related complications during the followup period. At 12 months, only 2 patients showed improvement in both skin and pulmonary function measures, whereas 5 patients were worse and 3 were stable. CONCLUSION: At the dosage administered in this study, ATGAM appears ineffective in improving the skin and pulmonary features of SSc.

[Interventional MRI. Value of low field strength and very fast 3D steady state imaging sequences for the guidance of a "non" ferromagnetic needle]. / IRM interventionnelle. Intérêt du bas champ magnétique et des séquences ultrarapides d'équilibre dynamique 3D pour le suivi d'une aiguille "non" ferro-magnétique.

PURPOSE: The excellent tissue differenciation provided by MRI in the three directions and the lack of ionizing radiations make it ideal for interventional procedures. Many problems must still be solved: the access to the patient, the size of the artefact produced by interventional instruments and the acquisition time. In this study, we evaluated the influence of field strength for standard imaging sequences on the MRI artefact of a non ferro-magnetic biopsy needle. Then, we developed very fast sequences on a opened 0.1 T dedicated magnet to test in vitro and ex vivo the potential ability of this system in the guidance of the needle. MATERIAL AND METHODS: The biopsy needle was a new stainless steel needle made of 49% Nickel. The needle artefact's size measurements were made at 0.1 T, 0.5 T and 1 T on a bicompartmental phantom (one compartment with a long T1 and another with a long T2), with standard gradient echo (400/12/90 degrees) and spin echo (500/25) sequences. At 0.1 T, we optimized very fast steady state 3D FAST (T1 weighted) and 3D CE-FAST (T2 weighted) sequences to reduce the acquisition time, preserving good image contrasts for a field of view reaching 38 mm and 48 x 64 or 24 x 32 matrix. RESULTS: The larger needle artefact observed on gradient echo images varied from 3.6 mm at 0.1 T to 8.6 mm at 1 T. The shortest acquisition time for 4 contiguous slices of 2mm with a 1.2 mm/pixel resolution and a 24 x 32 matrix was 1.5 s for the 3D FAST (16/9/65 degrees) sequence and 3 s for the 3D CE-FAST (29/22/65 degrees) sequence. We realized a complete MRI guided abdominal puncture on a cat cadaver with 4 series of 15 s 3D FAST images (16/9/65 degrees, 4 slices, 5 excitations, 1.2 mm/pixel, FOV = 77 mm). Besides the cat positioning and the image reconstruction time, the whole puncture lasted 1 min (4 x 15 s). CONCLUSION: Low field MRI (0.1 T) combined with very fast 3D steady state sequences is adapted for the real time guidance of biopsy needles.

Steroid sparing activity of tenidap in patients with polymyalgia rheumatica: a multicenter double blind randomized placebo controlled study.

OBJECTIVE: To determine whether tenidap treatment would allow reduction or replacement of systemic corticosteroid treatment in patients with polymyalgia rheumatica (PMR). METHODS: A 15-week double blind, randomized, multicenter, placebo-controlled study of tenidap sodium (120 mg/day) in patients with symptomatically controlled PMR receiving 10 mg/day prednisone was conducted. After receiving study drug for 3 weeks, prednisone dose was reduced by 2.5 mg/day every 3 weeks. The lowest clinically effective dose of prednisone was recorded as 10, 7.5, 5, 2.5 or 0 mg/day. RESULTS: Thirty-two patients were randomized to tenidap or placebo. As prednisone was reduced more placebo patients experienced an exacerbation of PMR symptoms, elevation of erythrocyte sedimentation rate and increased serum C-reactive protein. Twice as many placebo patients (10 of 16) as tenidap patients (5 of 16) discontinued due to lack of efficacy. The lowest effective dose of prednisone could be determined in 27 of the 32 patients, 11 receiving tenidap and 16 placebo. A significantly (p = 0.027) greater proportion of patients receiving tenidap (5 of 11) than placebo (1 of 16) were able to discontinue prednisone without experiencing a symptomatic flare. CONCLUSION: As prednisone was reduced, symptoms of PMR were controlled better by tenidap than by placebo. Forty-five percent of evaluable patients receiving tenidap were able to discontinue prednisone without a disease flare compared to 6% for placebo.

Homologous down-regulation of gonadotropin-releasing hormone receptor sites and messenger ribonucleic acid transcripts in alpha T3-1 cells.

GnRH is known to down-regulate its pituitary receptors by mechanisms that include endocytosis of the agonist-receptor complex. To evaluate the extent to which changes in receptor synthesis contribute to this process, the effects of GnRH and its analogs on GnRH receptor number and messenger RNA (mRNA) levels were analyzed in the alpha T3-1 gonadotroph cell line. Treatment with GnRH or its potent agonist analog, des-Gly10-[D-Ala6]GnRH N-ethylamide, reduced GnRH receptor number in a time- and dose-dependent manner, with a half-maximal decrease in response to 10(-6) M GnRH or agonist analog by 75 min. The maximum decrease in receptor number (to 31% of the control value) was sustained for up to 72 h. In alpha T3-1 cells incubated with 10(-8) M GnRH or agonist analog, the GnRH receptors fell by 28% and 46% after 2 h, respectively; no change in receptors occurred after treatment with 10(-8) M GnRH antagonist ([D-pGlu1,D-Phe2,D-Trp3,6]GnRH). Time- and dose-dependent reductions in the level of receptor mRNA were also observed after treatment of alpha T3-1 cells with GnRH and the agonist analog. However, the maximal reduction in mRNA levels (to 60-70% of the control value) was consistently less than the decline in receptor number. These results indicate that the mechanism of GnRH receptor down-regulation in alpha T3-1 gonadotrophs includes reduction of receptor synthesis secondary to decreases in receptor mRNA levels. The finding that reductions in mRNA levels were relatively less than the decreases in receptor number is consistent with the involvement of additional mechanisms, including endocytosis and degradation, in down-regulation of the GnRH receptor.

Nucleotide imbalance and polymerase chain reaction: effects on DNA amplification and synthesis of high specific activity radiolabeled DNA probes.

Synthesis of radiolabeled DNA probes via polymerase chain reaction (PCR) is a convenient alternative to the more conventional methods of random primer-labeling and nick translation. PCR requires less template and allows the synthesis of radiolabeled probes from specific sequences contained within cloning vectors and genomic DNA. Under nucleotide imbalance conditions where the concentration of the radiolabeled nucleotide was 0.825 microM and the other dNTPs were each > 25 microM, amplification by Taq DNA polymerase was inhibited. Reducing the concentrations of the unlabeled dNTPs resulted in greater yields of amplification product with maximal yield obtained when the concentration of three unlabeled nucleotides was two- to eightfold higher than that of the limiting labeled nucleotide. When we utilized this amplification method for synthesis of an 800-bp glyceraldehyde-3-phosphate (GAPDH) dehydrogenase probe, 87% of the added [32P]dCTP was incorporated into amplification product. Application of this method for synthesis of high specific activity probes ( > 4 x 10(9) cpm/micrograms) up to 2.6 kb in length is demonstrated and utility of the 800-bp GAPDH probe for hybridization to Northern blots for detection of GAPDH mRNA is presented.

Involvement of carboxyl groups in the divalent cation permeability of rat parotid gland basolateral plasma membrane.

Divalent cation permeability of rat parotid gland basolateral plasma membranes was examined in dispersed parotid acini (by Ca2+ or Mn2+ entry) and in isolated basolateral plasma membrane vesicles (BLMV, by 45Ca2+ influx). Mn2+ entry (fura2 quenching) was about 1.6 fold higher in internal Ca2+ pool-depleted acini (Ca(2+)-depl acini) than in unstimulated cells. Mn2+ entry into Ca(2+)-depl acini was increased at external pH > 7.4 and decreased at pH < 7.4. Pretreatment of Ca(2+)-depl acini with the relatively hydrophobic carboxylic group reagent, N,N'-dicyclohexylcarbodiimide (DCCD, 50 microM for 30 min) resulted in the inhibition of Mn2+ entry into Ca(2+)-depl acini to unstimulated levels. Another hydrophobic carboxyl group reagent, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) and the relatively hydrophilic carboxyl group reagents, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and 1-cyclohexyl-3-(2-morpholinoethyl)carbodiimide (CMCD) did not affect Mn2+ entry. Similar to the effects in intact acini, Ca2+ influx into BLMV was decreased when the external pH was lowered below 7.4. Also DCCD (5 mM, 30 min), but not EEDQ, decreased (40%) Ca2+ influx in BLMV. However, unlike in acini, the hydrophilic reagents, EDC, EAC, and CMCD decreased Ca2+ permeability in BLMV and the effects were nonadditive with the decrease induced by DCCD. The aggregate effects of carboxyl group reagents on the Ca2+ and Mn2+ permeability in BLMV and intact acini, respectively, suggest that a critical carboxyl group (most likely accessible from the cytoplasmic side of the plasma membrane) is involved in divalent cation flux in rat parotid acinar cells.