Need to reconsider national quality standards for red cell components: Evidence from a retrospective observational analysis.

Background & objectives Red cell concentrates (RCCs) must comply with applicable quality control (QC) standards to achieve the desired therapeutic effect in the recipient. In this study, we assessed the effect of change in the component preparation process on the quality of RCCs and their compliance with different QC standards. Methods A retrospective analysis of data for QC testing of RCCs over a period of 10 years, (from 2009 to 2019), was undertaken. QC testing parameters [volume, haematocrit (Hct), haemoglobin (Hb) content, white blood cell (WBC) content and percentage (%) haemolysis] were used to assess compliance with three national and three international QC standards. Linear regression analysis was done to assess the influence of donor variables. Results Data from 5,218 RCC units was included in the analysis. A majority (>50%) of RCCs prepared did not meet the three national QC standards either for volume or for Hct. The criteria for volume, Hct and Hb content, as defined in different international standards, were fulfilled by a majority (>75%) of RCCs evaluated. RCCs prepared by the buffy coat method had overall better compliance with QC standards compared to the platelet-rich plasma (PRP) method. The method of component preparation was found to influence Hb content, WBC content and percentage haemolysis. Male gender was associated with better Hb content. Interpretation & conclusions RCC prepared at our centre was found to have better compliance with international QC criteria compared to national standards. There is a need to reconsider the current national QC criteria for red cells with due consideration to the volume of whole blood collected and the method used for RCC preparation.

A comparative account of phototoxicity of anthracene and pyrene in the tadpoles of the anuran amphibian Fejervarya limnocharis using multiple toxicological end points.

Anthracene (Anth) and pyrene (Pyr), two of the priority polycyclic aromatic hydrocarbons (PAHs), being lipophilic in nature, not only accumulate in animals, but also settle in the sediment of water bodies leading to continuous exposure for animals. Anth and Pyr when exposed to sunlight can be photoactivated and have harmful effects on aquatic organisms. A comparative analysis was carried out to assess the acute, sub-chronic, genetic and biochemical toxicity of Anth and Pyr in F. limnocharis tadpoles following short exposures to sunlight on a daily basis. In the bioaccumulation studies, it was found that both Anth and Pyr accumulated in the tadpole tissues in a concentration and time dependent manner. The LC50 values for Anth (under 15 min of daily sunlight exposure) were found to be 2.87, 2.59, 2.28, 1.80 mg/L at 24, 48, 72 and 96 h of the exposures. The corresponding LC50 values for Pyr were 1.03, 0.80, 0.62, 0.42 mg/L. Sublethal exposure of Anth and Pyr affected the survivality, time to metamorphosis as well as morphometric parameters under sunlight exposure. In the genotoxicity assessment studies, particularly the micronucleus test and comet assay, it was found that Pyr led to a higher incidence of micronucleus formation and DNA damage in comparison to Anth. The exposure to PAHs resulted in significant changes in the activity of antioxidant-mediated protective response, specifically the SOD activity, which varied between the groups treated with Anth and Pyr. On the other hand, Pyr treated group showed a higher level of GSH as compared to Anth treated groups. Moreover, the elevation in MDA level in the Anth and Pyr treated groups suggests an increase in lipid peroxidation. Future research should focus on understanding the ecotoxicological risk faced by anuran amphibia due to PAHs that frequently occur in aquatic environments and developing strategies to mitigate these risks.

Geostatistical approach for management of soil nutrients with special emphasis on different forms of potassium considering their spatial variation in intensive cropping system of West Bengal, India.

A large part of precision agriculture research in the developing countries is devoted towards precision nutrient management aspects. This has led to better economics and efficiency of nutrient use with off-farm advantages of environmental security. The keystone of precision nutrient management is analysis and interpretation of spatial variability of soils by establishing management zones. In this study, spatial variability of major soil nutrient contents was evaluated in the Ghoragacha village of North 24 Parganas district of West Bengal, India. Surface soil samples from 100 locations, covering different cropping systems of the village, was collected from 0 to 15 cm depth using 100×100 m grid system and analyzed in the laboratory to determine organic carbon (OC), available nitrogen (N), phosphorus (P), and potassium (K) contents of the soil as well as its water-soluble K (KWS), exchangeable K (KEX), and non-exchangeable forms of K (KNEX). Geostatistical analyses were performed to determine the spatial variation structure of each nutrient content within the village, followed by the generation of surface maps through kriging. Four commonly used semivariogram models, i.e., spherical, exponential, Gaussian, and linear models were fitted to each soil property, and the best one was used to prepare surface maps through krigging. Spherical model was found the best for available N and P contents, while linear and exponential model was the best for OC and available K, and for KWS and KNEK, Gausian model was the best. Surface maps of nutrient contents showed that N content (129-195 kg ha(-1)) was the most limiting factor throughout the village, while P status was generally very high ( 10-678 kg ha(-1)) in the soils of the present village. Among the different soil K fractions, KWS registered the maximum variability (CV 75%), while the remaining soil K fractions showed moderate to high variation. Interestingly, KNEX content also showed high variability, which essentially indicates reserve native K exploitation under intensive cultivation. These maps highlight the necessity of estimating the other soil K fractions as well for better understanding of soil K supplying capacity and K fertilization strategy rather than the current recommendations, based on the plant-available K alone. In conclusion, the present study revealed that the variability of nutrient distribution was a consequence of complex interactions between the cropping system, nutrient application rates, and the native soil characteristics, and such interactions could be utilized to develop the nutrient management strategies for intensive small-holder system.

Effects of changed water regime on the toxicity of silver nanoparticles (AgNPs) in tadpoles of Fejervarya limnocharis.

Climate change is viewed as one of the important causes of the amphibian population decline. Aspects of climate change like increase in water temperature and drying up of habitats have been underrepresented. The expanding production and usage of metal nanoparticles like silver nanoparticles (AgNPs) make them likely to end up in aquatic ecosystems. To arrive at a realistic assessment of the impact of AgNPs in a warming world, we have investigated the effects of temperature on the acute toxicity of AgNPs in tadpoles of Fejervarya limnocharis at 24, 48, 72 and 96 h of exposure. The various aspects of sub-lethal toxicities of AgNPs with increase in temperature were also investigated. Besides, the effects of habitat desiccation on the sub-lethal toxicities of AgNPs in the tadpoles were analysed. The LC50 values of AgNPs at four different time points were found to be significantly different between the two different temperatures. Alterations in survival pattern, life history traits, amplifications in genotoxic potential and oxidative stress were observed with increased water temperature following AgNP exposure. The phenomenon of habitat desiccation was also found to significantly affect the toxicity of AgNPs with respect to alterations in mortality rate, time to metamorphosis and morphometric parameters of metamorphosed tadpoles. The findings suggest that changed water regime such as increased water temperature as well as reduction in water level accelerated the toxic effects of AgNPs in F. limnocharis tadpoles which is likely to affect their natural populations.

Toxic effects of fenvalerate in tadpoles of Fejervarya limnocharis: a multiparametric study.

Pyrethroids are among the most widely used insecticides. Fenvalerate (FEN), a synthetic pyrethroid, is frequently used in domestic and agricultural settings to control insects which ultimately find its way into the aquatic ecosystems. The larval stages of amphibians, which are experiencing a rapid population decline, are spent in aquatic habitats, thus making them vulnerable to FEN exposure. The potential toxic effects of pyrethoids in general and FEN in particular are not well understood. The present study was carried out to assess the toxicity of FEN in tadpoles of Fejervarya limnocharis. FEN at different concentrations (0, 4, 5, 6, 7, and 8 mg/L) induced substantial lethal effects. The estimated LC50 values were 8.54, 6.73, 5.44, and 4.44 mg/L at 24, 48, 72, and 96 h respectively. Exposure to environmentally relevant sub-lethal concentrations delayed metamorphosis and reduced survivality. FEN was found to be genotoxic in erythrocyte micronucleus and comet assay. Further, sub-lethal concentrations of FEN adversely affected the antioxidant defense mechanism of the exposed individuals with parallel increase oxidative damage to membrane lipids. The swimming behavior in the form of startle response, swirl response, and total movements was decreased with a concomitant decrease in AChE activity. In addition, FEN exhibited significant cardiotoxicity by decreasing the cardiac rate of the exposed individuals. The present findings clearly indicate that FEN can cause significant toxicity to the tadpoles of F. limnocharis affecting their survival and fitness in the natural environment.

Effect of donor parameters and cell separators on yield of apheresis platelet and their impact on corrected count increment in aplastic anemia patients.

BACKGROUND: The new cell separators make it simple to collect single donor platelets (SDP), although the platelet yield may vary depending on the cell separator used and donor-related clinical and laboratory variables. AIMS: This study aims to study the factors affecting SDP yield and corrected count increment (CCI). MATERIALS AND METHODS: This retrospective study was carried out at a tertiary care facility in northern India, over 4 years (May 2017-April 2020), data were retrieved and analyzed. STATISTICAL ANALYSIS: Categorical variables were presented as proportions, while continuous variables were presented as mean with standard deviation, P < 0.05 was considered significant. RESULTS: We found a positive correlation between predonation platelet count and yield (r = 0.243, P = 0.000). No such significant correlation was found with Hb concentration (r = 0.025, P = 0.720), age (r = 0.016, P = 0.820), sex (r = -0.038, P = 0.584), and weight (r = -0.025, P = 0.714). Maximum platelet yield and minimum time were seen with Trima. Only 39.3% (33/84) meet the 24 h CCI. The majority of patients did not meet the desired CCI could be due to the patients' clinical condition. On logistic regression, we found a significant association of 24 h CCI with product yield (odds ratio [OR] = 0.168, P = 0.015) and posttransfusion platelet count (OR = 0.454, P < 0.05). CONCLUSION: The only donor-related factor that influences yield is predonation platelet count, whereas 24 h CCI may depend on the clinical status of the patient and yield.

Hypocoagulability in Children With Decompensated Chronic Liver Disease and Sepsis: Assessment by Thromboelastography.

Objective: To evaluate the coagulation status of children with decompensated chronic liver disease (DCLD) and infection and factors affecting it using thromboelastography (TEG). Methods: Coagulation status of children admitted with DCLD and infection was assessed by international normalized ratio (INR), platelet count, and TEG [reaction time (R), kinetic time (K), α-angle (AA), maximum amplitude (MA), coagulation index (CI), and lysis index (LY30)] at admission and at 7-14 days after treatment. CI < -3 represents hypocoagulable state. Clinical profile including systemic inflammatory response syndrome (SIRS), infection severity, bleeding, treatment response, and outcome were noted. Results: Thirty children (21 boys, median (IQR) age 78 [15.7-180] months) were studied prospectively. At admission, 29 (96.7%) had prolonged INR, 24 (80%) had thrombocytopenia, and 17 (56.6%) were hypocoagulable by TEG. Nine of 30 (30%) had normal TEG but deranged INR and platelets. Nineteen (63.3%) cases had SIRS, 11 (36.6%) had severe sepsis, and 8 (26.6%) had bleeding. Hypocoagulable state was common in severe sepsis than sepsis/infection (81.1% versus 42.1%; P = 0.05) and persistent (n = 4) versus recovered SIRS (n = 15, 100% versus 33%; P = 0.03). Bleeders had prolonged R-time (7.8 versus 5.4 min; P = 0.03), smaller MA (30.2 versus 47 mm; P = 0.05), and α-angle (40.4 versus 62.9; P = 0.03) but similar INR and platelets than nonbleeders. Six patients (20%) had poor in-hospital outcomes; R-time ≥8.5 min predicted mortality with high sensitivity (83%) and specificity (100%). Conclusions: Fifth-seven percent of children with DCLD and infection were hypocoagulable by TEG. Severe sepsis and persistent SIRS worsened the coagulation status. TEG identifies bleeders better than INR and platelet count. R-time ≥8.5 min predicts a poor hospital outcome.

Enhanced clearance of Abeta in brain by sustaining the plasmin proteolysis cascade.

The amyloid hypothesis states that a variety of neurotoxic beta-amyloid (Abeta) species contribute to the pathogenesis of Alzheimer's disease. Accordingly, a key determinant of disease onset and progression is the appropriate balance between Abeta production and clearance. Enzymes responsible for the degradation of Abeta are not well understood, and, thus far, it has not been possible to enhance Abeta catabolism by pharmacological manipulation. We provide evidence that Abeta catabolism is increased after inhibition of plasminogen activator inhibitor-1 (PAI-1) and may constitute a viable therapeutic approach for lowering brain Abeta levels. PAI-1 inhibits the activity of tissue plasminogen activator (tPA), an enzyme that cleaves plasminogen to generate plasmin, a protease that degrades Abeta oligomers and monomers. Because tPA, plasminogen and PAI-1 are expressed in the brain, we tested the hypothesis that inhibitors of PAI-1 will enhance the proteolytic clearance of brain Abeta. Our data demonstrate that PAI-1 inhibitors augment the activity of tPA and plasmin in hippocampus, significantly lower plasma and brain Abeta levels, restore long-term potentiation deficits in hippocampal slices from transgenic Abeta-producing mice, and reverse cognitive deficits in these mice.

Replacing winter rice in non-traditional areas by strawberry reduces arsenic bioaccumulation, and improves water productivity and profitability.

Use of huge amount (1450-1650 mm) of arsenic contaminated (14.0-24.5 mg l-1) ground water to irrigate winter rice resulted in high deposition of arsenic (As) in the topsoil and in rice grains, posing a serious threat to soil and human health of the Bengal basin. Strawberry (Fragaria × ananassa Duch.) requires 250 mm irrigation and fetches 3.5 times more net return over the winter rice, and can be grown as an alternate crop in place of winter rice to save the environment. In comparison to rice As load in edible parts of strawberry reduced from 865 to 39 µg kg-1. Deficit irrigation (0.8 and 0.6 crop evapotranspiration, ETc) to strawberry further reduced total as well as different As species load in fruits. Jute and straw mulches recorded lower As in fruits over other mulches. Drip irrigation to recharge full or 80% of ETc loss and use of jute agrotextile surface mulch maximized root growth and yield in strawberry, benefit:cost ratio, and energy efficiency and productivity. Results demonstrate that strawberry cultivation in non-traditional winter rice growing areas of Bengal basin can potentially benefit millions of people by reducing As load in food chains, ensuring higher returns, and aid in reviving the local jute agrotextile industry.

A study of spectrum of pulmonary pathology and expression of thyroid transcription factor-1 during neonatal period.

CONTEXT: Neonatal period is the single most hazardous period of life. The major causes of neonatal death are prematurity and respiratory distress syndrome. We report a series of neonatal autopsies in our Neonatal Intensive Care Unit with special emphasis on pulmonary pathology. The spectrum of pathological changes in the lungs and thyroid transcription factor-1 (TTF-1) expression was studied in detail with reference to its spatial distribution. AIMS: This study aims to analyze the causes of neonatal death with special attention to pulmonary pathology along with associated histopathological changes in lungs. We also evaluated the expression of TTF-1 at different levels of the airway. MATERIALS AND METHODS: After taking consent and anthropometric measurements, autopsy was performed. Weights of all organs were taken, and histological sections were examined under hematoxylin and eosin stain. TTF-1 immunostaining was done on lung sections. Localization of TTF-1 was evaluated at the intrapulmonary level of terminal bronchioles (TBs), distal bronchioles, and alveoli. RESULTS: We performed a series of 25 autopsies in neonates. In our series, most of the neonates were preterm (64%), had low birth weight (44%), and died within the first 7 days of life (80%). Majority (60%) of the neonates died due to pulmonary causes, followed by septicemia (24%), congenital anomalies (12%), and birth injury (4%). Among the respiratory causes, hyaline membrane disease (HMD) was diagnosed in maximum number of cases (32%), followed by pneumonia (12%) and pulmonary hemorrhage (12%). The TTF-1 expression in TBs, distal airways, and alveoli was significantly reduced or absent in cases of HMD compared to the control group. CONCLUSIONS: In this study, we observed that HMD is the most common cause of perinatal death among respiratory disorders, and in this disease, the expression of TTF-1 is significantly reduced in TBs, distal airways, and alveoli compared to the control group.

A Rare Case of Hemangioendothelioma of Urinary Bladder.

Hemangioendothelioma is a vascular tumor of endothelial nature of intermediate grade. It most commonly arises from soft tissue of upper and lower extremities. We report a rare case of epithelioid hemangioendothelioma of the urinary bladder. Histologically, it was a vascular tumor formed by smaller capillaries lined by plump epithelioid cells having eosinophilic cytoplasm. Diagnosis was confirmed by immunohistochemistry, as the tumor cells were positive for CD34 and smooth muscle actin.

FNAC aided diagnosis of clear cell sarcoma of kidney: Report of two cases in infants.

Clear cell sarcoma of kidney (CCSK) is a rare aggressive malignant renal neoplasm with a high metastatic potential. Its outcome has however, improved with the advent of doxorubicin based neoadjuvant chemotherapy. Here, we present two cases of CCSK in infants diagnosed on cytology followed by nephrectomy. The first case presented in the neonatal period and had the unusual histological finding of islands of cartilage. The second case presented at the age of eight months. The possibility of CCSK should, therefore, be considered in the differential diagnoses of renal masses in infants as well as neonates. Diagn. Cytopathol. 2017;45:761-765. © 2017 Wiley Periodicals, Inc.

VEGF Expression to Support Targeted Therapy in Ovarian Surface Epithelial Neoplasms.

INTRODUCTION: Vascular Endothelial Growth Factor (VEGF), a promoter of angiogenesis, is a promising target for anti-angiogenic therapy in ovarian cancer. In our study, we examined the expression of VEGF in the spectrum of epithelial ovarian neoplasms (benign, borderline and malignant) by Immunohistochemistry (IHC). AIM: Diagnosing ovarian epithelial neoplasms, examining the expression of VEGF in benign, borderline and malignant neoplasms and correlating it with histological grade and stage of malignant cases. MATERIALS AND METHODS: This is a cross-sectional, observational study where, total of 50 cases of surface epithelial ovarian neoplasms were examined for expression of VEGF by IHC. Scoring for VEGF expression was done for each case. RESULTS: A total of 42 of the 50 cases (84%) showed VEGF expression. Out of the 42 positive cases, 19 were high VEGF expressors and 23 were low VEGF expressors. VEGF expression was significantly higher in carcinomas as compared to benign and borderline neoplasms (p=<0.001). All neoplasms of serous morphology were positive for VEGF. High VEGF expression was significantly associated with high grade (p=0.003) and stage (p=0.001) of disease. CONCLUSION: Ovarian surface epithelial neoplasms significantly express VEGF. Though, some VEGF expression was noted in benign and some borderline neoplasms, high VEGF expression was noted only in carcinomas and one case of borderline serous papillary tumour. Thus, these results suggest that epithelial ovarian tumours are candidates for VEGF targeting therapy as most of them are dependent on VEGF for progression.

Fibrosarcomatous change in the background of dermatofibrosarcoma protuberans in male breast: Study of a rare case and review of the entity.

Dermatofibrosarcoma protuberans is a cutaneous soft tissue neoplasm with potential for local recurrence but distant metastasis is rare. Trunk and extremities are most commonly involved. This case presented as left-sided breast lump in a male patient. The patient underwent left-sided modified radical mastectomy. Tissues were subjected to histopathological and immunohistochemical test subsequently. The tumor cells showed storiform arrangement with nuclear pleomorphism and increased mitotic figures at places. They were reactive to CD34 and non-reactive to S-100, smooth muscle actin, desmin, cytokeratin and epithelial membrane antigen. The diagnosis of dermatofibrosarcoma protuberans with areas of fibrosarcomatous change was given. Though trunk is a common site for this tumor but its presentation as male breast lump has made the case unique.

De novo myeloid sarcoma involving mandible in a child: Report of a rare occurrence.

Myeloid sarcoma (MS) is a rare malignant disease defined as extramedullary infiltration of immature myeloid cells. We reporte a 2-year-old male of isolated MS who presented with swelling over the left side of the body of the mandible. Proper histological examination and adequate panels of immunohistochemical stain led to the accurate diagnosis. Early intervention with systemic chemotherapy regimens based on cytarabine is the treatment of choice. The role of chromosomal aberrations and genetic abnormality related to prognosis remain uncertain.

Primary central nervous system teratoma with sarcomatous transformation in a young girl: Report of a rare case.

A 13-year-old girl presented with chief complaints of severe headache and vomiting followed by hemiparesis. Radiological examination suggested a space occupying lesion in the right parietal lobe. Craniotomy and debulking of the tumor mass were done. Histopathological and subsequent immunohistochemical examination showed a tumor composed of fascicle of atypical spindle cells which revealed reactivity to vimentin with interspersed areas of well-differentiated cartilage tissue. Hence, the diagnosis of teratoma with sarcomatous transformation was given. Detailed discussion including review of literature has been made regarding different aspect of the tumor.

Primary Merkel cell carcinoma of the oral mucosa in a young adult male: report of a rare case.

Merkel cell carcinoma (MCC) is a highly aggressive neoplasm of skin with neuroendocrine differentiation. Primary MCC of the oral mucosa is exceedingly rare and even more unresponsive to therapy. A 15-year-old male presents with gradually increasing painless swelling in right side of the floor of mouth for 6 weeks. Computed tomography of head and neck region showed globular mass (4.6 cm × 1.7 cm) involving right side of the floor of mouth. Fine-needle aspiration from the upper deep cervical node suggested small round cell tumor. A trucut biopsy showed mass composed of trabeculae and nests of tumor cells with high N:C ratio, granular speckled chromatin, scanty to moderate amount of clear vacuolated cytoplasm. Cells were immunoreactive for cytokeratin-20, CD56, c-kit, CD99 and negative for p63, thyroid-transcription factor-1, CDX2, synaptophysin, neuron-specific enolase. Patient was started on chemotherapy with cyclophosphamide, doxorubicin and vincristine. The mass regressed in size and patient underwent wide local excision with pull-through approach. Patient is currently under combined chemoradiation regime and doing well.

Comparative study of cytology and immunocytochemistry with trucut biopsy and immunohistochemistry in diagnosis of localized lung lesions: A prospective study.

BACKGROUND: Percutaneous lung biopsy is now a common procedure in pulmonary medicine, and several different techniques are in use. The most common has been the use of a fine needle under computed tomography (CT) guidance combined with the trucut needle for histology. AIM: To evaluate the efficacy of fine needle aspiration cytology (FNAC) and immunocytochemistry in comparison with trucut biopsy and immunohistochemistry in patients with localized intrathoracic lesions suspicious for malignancy. MATERIALS AND METHODS: Eighty patients with localized mass lesions in the lung on imaging (chest radiograph/CT) were selected for this study over a period of 1 year. FNAC was carried out by a 22 G spinal needle after localization of the mass in the CT scan followed by guided trucut biopsy. Immunocytochemistry and immunohistochemistry were performed as and when required. RESULTS: The mean age of our study population was 57.6 years and the M:F ratio was 4.2:1. Majority of the lesions were peripheral and in the right lung. Adenocarcinoma was most prevalent (49%), followed by squamous cell carcinoma and small cell carcinoma. Cyto-histopathological concordance was seen in 60 cases (75%). The highest rate of concordance was seen in small cell carcinoma (83.3%). The overall sensitivity of FNAC in distinguishing malignant lung lesions from benign lesions was 84.2% and the specificity was 100%. The sensitivity of cytology in diagnosing small cell carcinoma was 83.3% and of non-small cell carcinoma was 65.38%. Immunocytochemistry was carried out in 34 cases, all of which were followed by immunohistochemistry. Cyto-histopathological concordance was noted in 31 of these cases (91.2%). We used the standard panel of four markers (cytokeratin-7, thyroid transcription factor-1, p63 and CD56) for all selected cases. CONCLUSION: Cytology along with immunocytochemistry is highly effective in diagnosing and categorizing lung neoplasms, producing comparable results to trucut biopsy and immunohistochemistry.

A Rare Case of Cytokeratin-Positive Interstitial Reticulum Cell Sarcoma and Review of the Entity.

The tumors of dendritic/reticulum cells constitutes the rarest tumors affecting the lymphoid tissues. Among them tumors derived from fibroblastic reticular cells (FBRCs) are very rare, and those of cytokeratin (CK)-positive interstitial reticulum cells (CIRCs) origin are even more rare. These tumors can be easily misdiagnosed as tumors of other dendritic cells, myofibroblastic tumors or even metastatic poorly differentiated carcinomas. Less than twenty such cases have been reported in the literature till date. We present such a rare case of CIRC sarcoma in cervical lymph node of a 64-year-old man.

Notch signaling in primary endothelial cells.

The Notch family of cell-surface receptors has been proposed to regulate cell-fate decisions by modulating the ability of each cell to respond to environmental cues. In vertebrates, gain-of-function and loss-of-function studies have demonstrated a requirement for Notch signaling for proper patterning of the vasculature during embryogenesis. To examine the molecular mechanisms by which Notch regulates vascular development, we analyzed changes in gene expression in response to Notch signaling. Notch signal transduction and function were assessed in primary human endothelial cells isolated from the dermal microvasculature of neonates, HMVECd. We demonstrate that HMVECd cells express a heterodimeric form of endogenous Notch4 on their cell surface. Using an in vitro coculture assay, we found that Delta4 can function as a ligand for Notch4 in HMVECd cells. Moreover, ectopic expression of an activated allele of Notch4 upregulated the expression of Delta4, suggesting that there may be a regulatory loop between Notch4 and its ligand, Delta4. Notch4 activation also induced the expression of the transcriptional repressors, HES1, HERP1, and HERP2, as well as ephrinB2, an angiogenic factor proposed to be involved in arterial/venous endothelial cell specification.