Chemical Peeling: A Useful Tool in the Office. / Peeling químico, una herramienta útil en la consulta.

Chemical peeling is a common treatment in cosmetic dermatology. A peel that has been used for many years is trichloroacetic acid. Its adverse effects have for a long time been a major limitation. We present a practical review of the characteristics, mechanisms of action, indications, and complications of superficial chemical peels and of peeling with trichloroacetic acid.

Thymoglobulin Induction Therapy in Deceased Donor Kidney Transplantation: Single-Center Experience in Mexico.

BACKGROUND: Induction therapy is used to reduce the incidence of graft rejection and delayed graft function. Thymoglobulin is the most used inductor agent in deceased donor kidney transplantation due to its lower rejection and delayed graft function rates. METHODS: Retrospective study of patients who underwent deceased donor kidney transplantation from 2011 to 2014. Efficacy and safety outcomes evaluated were primary graft nonfunction, delayed graft function, acute rejection episodes, the lowest leukocyte count during the induction, adverse effects, eGFR, and patient and graft survival. P < .05 was considered statistically significant. RESULTS: A total of 42 patients were registered. Of these, 51.7% were female, with a mean age of 36.4 ± 11.1 years. Mean dialysis time was 112.4 ± 365 months. Mean donor age was 33.7 ± 13.1 years. Of the registered patients, 14.3% were extended criteria donors and 23.8% high-risk. Mean thymoglobulin dose was 4.4 ± 0.8 mg/kg. Primary graft nonfunction was 2.4%. Nineteen percent presented with delayed graft function and 19% with acute rejection. Mean lowest leukocyte count was of 4.6 ± 1.5 × 10(3) cells/mm(3). Mean hospital stay was 11.3 ± 6.3 days. Adverse effects were seen in 59.5% of registered patients, whereas graft survival 1 year and 3 years after transplantation was 85.3% and 56.9%, respectively. Patient survival 1 year and 3 years after transplantation was 85.3% and 53.8%, respectively. Patients who received a higher dose (>4.4 mg/kg) had a shorter hospital stay (9.4 ± 4.6 and 8.1 ± 2.3) than those who received lower dose (13.6 ± 7.9 and 12.8 ± 7.4; P < .05). CONCLUSION: Thymoglobulin induction at doses near 5 mg/kg in deceased donor kidney transplant is efficient and secure at our center.

Induction Immunosuppressive Therapy Use in Deceased Donor Kidney Transplantation: 11-Year Experience in Veracruz, Mexico.

BACKGROUND: Induction therapy reduces the frequency of acute rejection and delayed graft function in renal transplantation. Basiliximab and Thymoglobulin are most commonly used agents for induction. METHODS: A retrospective study of two transplant centers in Veracruz, Mexico compared induction therapy in deceased donor renal transplantation from 2003 to 2014. Efficacy and safety outcomes evaluated were primary graft nonfunction, delayed graft function, acute rejection episodes and hospitalizations during first year, and patient and graft survival. P < .05 was considered statistically significant. RESULTS: Seventy deceased kidney donors (40 male) were studied. Mean donor age was 32.9 ± 14.3 years, mean donor BMI 25.6 ± 4.3 kg/m(2), and mean donor creatinine 1.13 ± 0.58 mg/dL. Main cause of death was trauma (62.9%). In total, 125 kidney transplantations were performed, with female predominance (53.6%) and mean age 33.8 ± 11.8 years. Of these, 66.4% used basiliximab and 33.6% Thymoglobulin. Thymoglobulin patients were significantly older, with lower weight and BMI, and were on dialysis longer than basiliximab patients. DGF was present in 19.3% of basiliximab patients vs 16.7% in Thymoglobulin patients, acute rejection occurred in 16.9% of basiliximab patients vs 19% Thymoglobulin patients. A total of 33.7% basiliximab patients were hospitalized during the first year vs 47.6% Thymoglobulin-induced patients (P > .05). Mean graft survival was 84.2 ± 5.3 months (73.8-94.7) basiliximab vs 32.4 ± 28.7 months (28.7-36.1) Thymoglobulin, Kaplan-Meier survival did not show statistically significant differences between groups (P = .276; CI 95%). CONCLUSION: Similar transplant outcomes were obtained using basiliximab or Thymoglobulin induction in our population.

Effectiveness of Rosmarinus officinalis essential oil as antihypotensive agent in primary hypotensive patients and its influence on health-related quality of life.

ETHNOPHARMACOLOGICAL RELEVANCE: To study Rosmarinus officinalis (Rosemary) essential oil effect on primary hypotension and its influence on both physical and psychological aspects responsible for health-related quality of life (HRQOL) of patients. METHODOLOGY: Thirty-two patients with diagnosed hypotension were recruited between March 2007 and September 2008 for a prospective study for 72 weeks in a Spanish pharmacy. Clinical evaluation was carried out through the control of systolic and diastolic blood pressure levels (SBP and DBP, respectively) according to the International Standards from the American Society of Hypertension. HRQOL data were recorded within the SF-36 Health Survey(®) questionnaire throughout the study. Statistical methods were used as the essential tools to evaluate the effectiveness of Rosemary essential oil and to assess the relationship between the two quantitative variables (SBP and DBP) and scores from physical and mental summary components (PSC and MSC) obtained from the SF-36 Health Survey. RESULTS: Both blood pressure variables of SBP and DBP reflect the clinically significant antihypotensive effect of Rosemary essential oil that was maintained throughout the treatment period. After validation of the use of the questionnaire (Cronbach's alpha coefficient>0.82), statistically significant differences have been found between pre-treatment and post-treatment values of PSC and MSC, which indicate an improvement in these parameters that is directly related to the variation in blood pressure values. CONCLUSIONS: The increase achieved in blood pressure values after administration of Rosemary essential oil is clinically significant. The results obtained from this prospective clinical trial prove the effectiveness of statistical methodology as a new approach to explain the antihypotensive effect of rosemary essential oil and its relationship with the improvement in patients' quality of life.

Rejection is a strong graft survival predictor in live donor pediatric renal transplantation using cyclosporine, mycophenolate mofetil, and steroids: 5-year outcomes in a single Mexican center.

Long-term graft function and survival are of particular importance in children assuming that they have a longer transplantation life span than most adults. Because acute rejection episodes (ARE) continue to have a serious impact on graft loss, we analyzed the effects of ARE on 5-year survival and function in our population. Fifty-seven living donor kidney transplant recipients (34 males) younger than 18 years of age (13.5 ± 2.6 years; range, 5-17) were follow up for at feast 12 months using cyclosporine, mycophenolate mofetil, and steroid therapy with or without induction treatment between February 2003 and December 2010. ARE incidence during the first 12 months following transplantation was 14%. One-, 3- and 5-year serum creatinine values were 1.24 ± 0.39, 2.16 ± 2.39, and 1.76 ± 0.9 mg/dL, respectively. Mean calculated creatinine clearances (Schwartz) at 1, 3, and 5 years were 82.5 ± 24.8, 64.7 ± 24.1, and 67 ± 27.5 mL/min*1.73 m(2), respectively. Patient/graft survival rates were 96/85%, 90/72%, and 88/65% at 1, 3, and 5 years, respectively. Patients who experienced an ARE within 12 months following transplantation displayed a reduced 5-year graft survival rate (37.5%) versus those who did not (78%; P = .005). Patients who did not have an ARE during 60 months had a higher graft survival rate (76%) than those who had ARE (33%; P = .001). Patient without basiliximab induction showed a lower 5-year graft survival rate (61% vs 100%; P = not significant [NS]). ARE is an important risk factor for graft loss in the pediatric kidney transplant population.

PM01183, a new DNA minor groove covalent binder with potent in vitro and in vivo anti-tumour activity.

BACKGROUND AND PURPOSE: PM01183 is a new synthetic tetrahydroisoquinoline alkaloid that is currently in phase I clinical development for the treatment of solid tumours. In this study we have characterized the interactions of PM01183 with selected DNA molecules of defined sequence and its in vitro and in vivo cytotoxicity. EXPERIMENTAL APPROACH: DNA binding characteristics of PM01183 were studied using electrophoretic mobility shift assays, fluorescence-based melting kinetic experiments and computational modelling methods. Its mechanism of action was investigated using flow cytometry, Western blot analysis and fluorescent microscopy. In vitro anti-tumour activity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and the in vivo activity utilized several human cancer models. KEY RESULTS: Electrophoretic mobility shift assays demonstrated that PM01183 bound to DNA. Fluorescence-based thermal denaturation experiments showed that the most favourable DNA triplets providing a central guanine for covalent adduct formation are AGC, CGG, AGG and TGG. These binding preferences could be rationalized using molecular modelling. PM01183-DNA adducts in living cells give rise to double-strand breaks, triggering S-phase accumulation and apoptosis. The potent cytotoxic activity of PM01183 was ascertained in a 23-cell line panel with a mean GI(50) value of 2.7 nM. In four murine xenograft models of human cancer, PM01183 inhibited tumour growth significantly with no weight loss of treated animals. CONCLUSIONS AND IMPLICATIONS: PM01183 is shown to bind to selected DNA sequences and promoted apoptosis by inducing double-strand breaks at nanomolar concentrations. The potent anti-tumour activity of PM01183 in several murine models of human cancer supports its development as a novel anti-neoplastic agent.

Establishment and characterisation of a human carcinoma cell line with acquired resistance to Aplidin.

Aplidin (APL) is a new antitumoral drug from marine origin currently in phase II clinical trials against a wide multiplicity of cancers. As resistance may be, as with other drugs, an important obstacle to the APL therapeutic efficacy, we have established an acquired resistance cellular model by continuous exposure of HeLa cells to the drug. The stably resistant subline generated (HeLa-APL), possessing more than 1000-fold relative resistance to APL than parental cells, did not show crossresistance to a subset of clinically relevant antitumoral agents. In addition, resistance was not related to overexpression of P-glycoprotein or differences in overall drug accumulation. Comparing to parental cells, HeLa-APL cells did not present either significant differences in the growth rate or apparent alterations in the cell cycle distribution. Aplidin induced rapid and persistent phosphorylation of both JNK and p38 MAPKs, resulting in activation of the mitochondrial apoptotic pathway in parental cells, but, notably, in HeLa-APL-resistant cells MAPKs activation only occurred in a slight and transiently manner, failing to activate the above-mentioned apoptotic machinery. These results suggest that sustained activation of JNK and p38 is essential for triggering the apoptotic programme induced by APL and that HeLa-APL cells bypass this apoptotic response by preventing the specific mechanisms that prime and sustain the long-term activation of these signalling cascades. Although far from human tumour physiology in vivo, HeLa-APL cells represent a potentially useful tool in gaining insights into the mode of action of APL, in selecting non-crossresistant APL structural analogues, as well as in investigating and developing methods to prevent resistance to this drug.

Connection topology dependence of synchronization of neural assemblies on class 1 and 2 excitability.

Two main classes of excitable neurons are analyzed in terms of connection topology and strength of the coupling in a network of neurons. In both cases, we measure the degree of synchronization and responsiveness of the neural assembly. Class 2 excitability presents a fast wave-like propagation of the activity pattern, strong frequency dependence on the connection topology and a good level of synchronization regardless of the topology. On the other hand, class 1 excitability shows a strong dependence of the wave propagation speed and the synchronization degree on the connection topology, in addition no frequency adaptation is observed. We conclude that both types of neural excitability endow the neural assembly with very different dynamical properties. Although, for simplicity reasons, no inhibition has been included in our study, the emergent properties described in this paper may help to determine the class of excitability underlying a neural assembly.

Fast response and temporal coherent oscillations in small-world networks.

We have investigated the role that different connectivity regimes play in the dynamics of a network of Hodgkin-Huxley neurons by computer simulations. The different connectivity topologies exhibit the following features: random topologies give rise to fast system response yet are unable to produce coherent oscillations in the average activity of the network; on the other hand, regular topologies give rise to coherent oscillations, but in a temporal scale that is not in accordance with fast signal processing. Finally, small-world topologies, which fall between random and regular ones, take advantage of the best features of both, giving rise to fast system response with coherent oscillations.

Dexamethasone induces lipocalin-type prostaglandin D synthase gene expression in mouse neuronal cells.

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is responsible for the production of PGD(2), the main PG in the CNS. PGD(2) is an endogenous sleep inducer, and it is involved in the control of odor and pain responses and body temperature. In addition, PGD synthase transports lipophilic molecules in the subarachnoid space and CSF. By northern and western assays we show that the synthetic glucocorticoid dexamethasone, an inhibitor of PG production in most tissues, induces L-PGDS mRNA and protein in a dose- and time-dependent fashion in mouse neuronal GT1-7 cells. Accordingly, dexamethasone increases cellular L-PGDS enzymatic activity. Dexamethasone induced L-PGDS gene transcription in run-on assays and activated the mouse L-PGDS gene promoter in transiently transfected cells. It is interesting that the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate (TPA), which induces the synthesis of PGs in many tissues, inhibited the increase in L-PGDS expression induced by dexamethasone. In contrast, neither dexamethasone nor TPA affected the expression of cyclooxygenases-1 and -2. Our data demonstrate that dexamethasone induces L-PGDS gene transcription in neuronal cells.

Retinoic acid and 1,25-dihydroxyvitamin D3 inhibit tenascin-C expression in rat glioma C6 cells.

Tenascin-C (Tn-C) is an extracellular matrix protein with growth-, invasive-, and angiogenesis-promoting activities. Tn-C is upregulated during wound healing, tumorigenesis, and other pathological conditions. Highly malignant gliomas with poor prognosis exhibit high levels of Tn-C expression. Here we demonstrate that Tn-C RNA expression in glioma C6 cells is inhibited in a dose-dependent manner by retinoic acid (RA) and 1,25-dihydroxyvitamin D3 (1,25-D3). No additive or synergistic effects were found. Inhibition is maximum 24 hr after RA or 1,25-D3 treatment, prior to a delayed cytotoxic effect starting at day 4-5 of treatment, and correlates with a reduction in the synthesis of Tn-C protein. Tn-C expression is also inhibited, but to a lesser extent by prostaglandin D2 (PGD2). Furthermore, both RA and 1,25-D3, but not PGD2 abolish the induction of Tn-C by the tumor promoter 12-O-tetradecanoyl phorbol 13-acetate. The inhibition of Tn-C expression might be relevant for the anti-cancer activity of RA and 1,25-D3.

Identification of a thyroid hormone response element in the promoter region of the rat lipocalin-type prostaglandin D synthase (beta-trace) gene.

We have previously reported that mRNA levels for the rat lipocalin-type prostaglandin (PG) D synthase/beta-trace (PGDS) gene, the enzyme responsible for the production of PGD2 in the central nervous system, are regulated by thyroid hormone in vivo. In this study, we describe the identification of a thyroid hormone (T3) response element (T3RE) in the 5'-flanking region of the rat PGDS gene. By radioimmunoprecipitation of genomic fragments using thyroid hormone receptor (TR) protein and specific anti-TR antibodies, gel-shift, foot-printing, mutational analysis, and transactivation assays we have identified a spaced four imperfect direct repeat (DR4) element, GGTTCACTTCAGGGTA (positions -586/-571), which functions as a T3RE when fused to a heterologous promoter. Our results suggest that thyroid hormone regulates the expression of the rat lipocalin-type PGDS gene through this element. Remarkably, the element identified also confers regulation by retinoic acid. Giving the important roles proposed for the PGDS enzyme and its product, PGD2, the major PG in the mammalian brain, the altered expression of the PGDS gene may contribute to the deleterious effects of hypothyroidism in the central nervous system.

Hypothyroidism alters the expression of prostaglandin D2 synthase/beta trace in specific areas of the developing rat brain.

Lipocalin-type prostaglandin D2 synthase is the enzyme responsible for the synthesis of prostaglandin D2, a major prostaglandin in the central nervous system. We analysed the effects of thyroid hormone deprivation on prostaglandin D2 synthase gene expression in the developing rat brain. By in situ hybridization, the strongest prostaglandin D2 synthase mRNA signal was detected in the leptomeninges and choroid plexus. The signal was greatly reduced in the cerebellar interlaminar meninges of hypothyroid rats aged 15 and 25 days. Immunohistochemical studies defined changes in the location of the prostaglandin D2 synthase protein. In control but not in hypothyroid animals, Cajal-Retzius neurons of cortical layer I, and pyramidal cortical plate neurons were intensely stained on postnatal day 5. Conversely, prostaglandin D2 synthase protein levels were higher in neurons of the CA1 and CA3 regions and the dentate gyrus of the hippocampus of hypothyroid animals on postnatal days 5, 15 and 25, and also in subplate neurons on postnatal days 15 and 25. In agreement with the in situ hybridization and northern blotting data, the major difference was found in the cerebellar interlaminar meninges of hypothyroid animals, where the protein was clearly down-regulated on postnatal days 15 and 25. These results show that hypothyroidism causes both age- and region-specific alterations in the expression and location of the prostaglandin D2 synthase during postnatal brain development, probably reflecting a cell-specific regulatory effect of thyroid hormone on the prostaglandin D2 synthase.

[An infection study of total parenteral nutrition catheters for Y-site drug administration]. / Estudio de la infección de catéteres de nutrición parenteral total al administrar fármacos en "Y".

When faced with the frequent use of parenteral nutrition (TPN) and the multiple problems which the maintenance of venous pathways presents, we initiated this study to try and show that the use of TPN catheters for the perfusion of drugs in "Y", does ot increase the incidence of infection. 70 patients subjected to TPN were studied, divided into 3 groups: I: TPN with exclusive use catheter (23 patients). II: TPN with a catheter through which antibiotic medication is administered in "Y" (22 patients). III: TPN with a catheter through which non-antibiotic medication is administered in "Y" (25 patients). Despite there being no extra manipulation in group I, when applying Cramer's "Y" we did not find any significant differences between the three groups as to incidence of infection. When relating the variables of infection and number of manipulations by means of chi-squared, we did not find significant differences either. There is no increase in the incidence of infection with the increase of manipulation. When we relate the variables of infection and number of days of treatment with TPN by chi-squared, we did not find significant differences either. There were no more infections of the catheters with more days of treatment. Neither did we find significant differences with respect to the number of manipulations, according to the calculation done by the Student T-rest, between groups II and III. Therefore, we have reached the conclusion that although the use of TPN for the administration of other drugs should not be used indiscriminately, it is absolutely valid for concrete cases, with a difficulty of multiple venolysis, as long as the drugs that shall be administered are stable with TPN and as a long as the norms form the correct administration and the aseptic techniques are observed.

Efecto de la inmunosupresión con azatioprina-prednisona sobre la anastomosis bronquial telescopiada en el trasplante pulmonar unilateral experimental / Effect of immunosuppresion with azatioprine-prednisone on bronchial anastomosis in experimental unilateal pulmonary transplant

El efecto de altas dosis de azatioprina - prednisona sobre la anastomosis bronquial en el transplante pulmonar fue investigada en el presente trabajo en diez perros. Se realizó un trasplante pulmonar unilateral con anastomosis realizada en forma telescopiada en todos los casos. No observamos complicaciones en el seguimiento de los animales hasta los 18 meses, a pesar de las altas dosis de inmunosupresión

Brain-specific prostaglandin D2 synthetase mRNA is dependent on thyroid hormone during rat brain development.

We have previously described several cDNA clones whose expression is affected by thyroid hormone during rat brain development. We now report the identification of one of these, the E2 clone, as the brain-specific prostaglandin D2 (PGD2) synthetase gene. Sequence comparison shows a nearly complete identity between the 356 nucleotides of the E2 clone and nucleotides 403 to 759 of PGD2 synthetase cDNA. The pattern of E2 expression corresponds to that expected for brain specific PGD2 synthetase gene, i.e. the corresponding mRNA is not detected in any other tissue analyzed apart of the brain, and it was present at different levels in all brain regions. Hypothyroidism decreased E2 mRNA concentrations in cerebral cortex and cerebellum. Control of the level of expression of PGD2 synthetase gene may contribute the complex effects of thyroid hormone on brain development and function.

[Prune belly syndrome associated with cystic adenomatoid malformation of the lung and pulmonary sequestration]. / Síndrome de "prune belly" asociado a malformación adenomatoide quística pulmonar y secuestro pulmonar.

The "prune belly" syndrome classically described in males, has also been described in female patients with a variable incidence. Associations with multiple respiratory tract malformations have been reported which together with urinary tract anomalies and renal failure are often the cause of early mortality. We report the case of a female patient with prune belly in association with cystic adenomatoid malformation of the lung and pulmonary sequestration with a favorable clinical evolution following medical and surgical treatment.

Identification and localization of a nucleolin homologue in onion nucleoli.

A protein homologous to nucleolin, a major nucleolar protein with multifunctional features involved in pre-rRNA synthesis and early processing, has been identified and localized in situ in onion root meristematic cells by different techniques, which have included the use of an antibody raised against hamster nucleolin. The protein was identified on Western blots of nucleolar proteins as a 64-kDa band, by means of the anti-nucleolin antibody, bismuth staining, and the silver staining-nucleolar organizer (Ag-NOR) method. The experiments also suggested that nucleolin could be a target of these two cytochemical stainings. Although the 64-kDa band corresponds to a major nucleolar protein, it is a minor one among total nuclear proteins. The same techniques were used in situ at the ultrastructural level, and the immunogold detection of the nucleolin homologue was quantitatively evaluated. The protein accumulates in the transition area from nucleolar fibrillar centers to the dense fibrillar component, which is considered to be the structural result of ribosomal gene transcription. Out of this transition area, the dense fibrillar component may be divided into two regions, proximal and distal with respect to fibrillar centers, which show, respectively, the significant and unsignificant presence of nucleolin; we interpret this fact as the expression of the topological arrangement of pre-rRNA processing. Fibrillar centers themselves showed a weak but significant labeling with the anti-nucleolin antibody. However, bismuth staining was absent from the interior of fibrillar centers, indicating that the nucleolin in them is not phosphorylated. Ag-NOR staining uniformly covered fibrillar centers and the dense fibrillar component (at least in its proximal region), but it did not stain condensed chromatin inclusions in heterogeneous fibrillar centers, showing that the binding of nucleolin to chromatin is associated with its decondensation. This work provides additional evidence of the high phylogenetic conservation of molecular motifs which take part in ribosome biogenesis.

Danazol therapy renders red cells resistant to osmotic lysis.

Danazol, an attenuated androgen, is useful in endometriosis, idiopathic thrombocytopenic purpura (ITP), and autoimmune hemolytic anemia (AIHA). However, its mechanism of action is unknown. We investigated the possibility that danazol affects cell membranes directly. Red cell osmotic fragility was studied in patients receiving danazol. A significant decrease in osmotic fragility was observed. Accompanying the change, peripheral blood smears showed many target cells and electron microscopy revealed extra folds in erythrocyte membranes. Twenty-two patients were studied prospectively before and after danazol. Osmotic fragility decreased significantly (P less than 0.001) in 1 month of therapy and progressed with further treatment. A rebound increase (P less than 0.01) was observed in 1 month after discontinuation of danazol among 16 patients. Incubation experiments showed that danazol-induced changes are not reversed with normal sera. Patient sera did not induce the changes in normal red cells. Danazol in vitro protected red cells from osmotic lysis at low concentrations but enhanced lysis at high concentrations. We suggest that danazol alters red cell membranes directly to increase their surface area, inducing target cell formation and increasing their resistance to osmotic lysis.

Abnormal calcium handling by platelets in thrombotic disorders.

This study presents a quantitative comparison of the free cytoplasmic calcium concentration ([Ca2+]cyt) and the free concentration in the lumen of the dense tubules of the human platelet. The former was measured by the fluorescence of the high affinity indicator quin2 and latter by the fluorescence of chlorotetracycline (CTC). The CTC technique monitors calcium-CTC complex accumulation in the lumen of dense tubules and mitochondria when washed platelets were incubated in 2 mM Ca2+. Resting cytoplasmic and dense tubular Ca2+ concentrations were studied in platelets from patients suffering from venous and arterial thrombosis. Compared with normal controls (0.40 +/- 0.10, n = 54), the values of the calcium-CTC ratios were 0.68 +/- 0.19 (n = 16, p less than 0.005) in venous thrombosis; 0.75 +/- 0.18 (n = 14, p less than 0.005) in cardiovascular accident; 0.84 +/- 0.18 (n = 6, p less than 0.005) in occlusive peripheral vascular diseases; and 0.42 +/- 0.10 (n = 21, p greater than 0.1) in patient controls. The dense tubular Ca2+ levels for both patients and controls were perfectly correlated with the cytoplasmic levels using an equation that assumes that the dense tubular free calcium concentration ([Ca2+]dt) has a second power dependence on [Ca2+]cyt. The abnormal Ca2+ handling of platelets obtained from thrombotic patients could be completely reversed by preincubation with the calcium channel blocker verapamil. These observations suggest that the primary Ca2+ handling defect is the leakage through activated channels in the plasma membrane. The defect and the elevated resting [Ca2+]cyt and [Ca2+]dt are adequate to explain the observation of increased rates of collagen-activated aggregation in the above-mentioned group of patients. The results can be explained by platelets from thrombosis patients being exposed to activating factors in the circulation, resulting in Ca2+ channel activation. Channel activation persists through the process of platelet isolation and washing and is manifested in higher measured values of [Ca2+]cyt and [Ca2+]dt in the "resting state." This would bring the platelet closer to its aggregation when aggregation-inducing agents are added. The CTC test is shown to be a useful and convenient means of detecting this abnormality.