Right bundle branch block pattern after uncomplicated right ventricular outflow tract pacing in a patient with a left sided superior vena cava and corrected tetralogy of Fallot

Usually an electrocardiogram after right ventricular (RV) pacing should yield left bundle branch block (LBBB) pattern. However, the presence of right bundle branch block (RBBB) pattern after pacemaker implantation should alert the physician to a malposition of lead. We report a case of 18-year-old female who underwent dual chamber pacemaker implantation and had RBBB pattern post implantation. Detailed evaluation revealed an uncomplicated right ventricular outflow tract pacing. The possible causes of this abnormal pattern after an uncomplicated RV pacing are also reviewed.     

IRTKS (BAIAP2L1) Elongates Epithelial Microvilli Using EPS8-Dependent and Independent Mechanisms

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Detection of different adenosine triphosphatases in human placental brush border membranes

The microvillous membrane of human placental syncytiotrophoblast cells contains a high ATPase activity. The purpose of this study was to characterize this activity and to investigate the presence of vacuolar type H⁺ ATPase in this membrane. Intact brush border membrane vesicles strongly hydrolyzed ATP, reflecting the presence of ATPase on the external side of the membrane. The ATPase activity was entirely Mg²⁺ dependent and increased with pH. At pH 7.5, Vmax was 31.0 ± 1.7 mol/mg/20 min and Km 0.18 ± 0.03 mm ATP. Hydrolysis of ATP was not influenced by the presence of bicarbonate or alkaline phosphatase inhibitors, but at pH 8 it decreased by half following addition of 100 m dicyclohexylcarbodiimide (DCCD). At pH 7.5, 1 mm N-ethylmaleimide (NEM) depressed this activity by less than 5%. Opening the membrane vesicles with 0.1% desoxycholate (DOC) or Triton-X neither revealed any additional ATPase activity nor altered the low sensitivity to NEM. Treatment of these membranes with 1% cholate decreased the ATPase activity by more than 70% and did not enhance the sensitivity of ATP hydrolysis to NEM. 10^–7 m Bafilomycin, which reduced by 56 ± 9% the ATPase activity in dog kidney brash border membranes treated with 0.1% DOC, had no effect on placental brush border membranes subjected to the same procedure. Finally, neither immunocytochemical staining using monoclonal antibody to the Mr 31000 subunit of V-type H⁺ ATPase, nor electron microscopic examination detected the presence of H⁺ ATPase in placental membranes.In conclusion, the placental brush border membrane is the site of a strong ecto ATPase activity which is partially DCCD sensitive. However, our results did not detect the presence of any vacuolar type H⁺ ATPase activity in these membranes.This study was supported by the MRC grant N MA 9565 and by an extramural grant from Baxter Health Care Corporation. The authors are indepted to Dr. Patrick Vinay for this help in providing Bafilomycin and dog kidney membranes, as well as for his insightful discussion.     

Scanning electron microscope observations on the pathological changes of Malpighian tubules in the worker honeybee,Apis mellifera,infected by Malpighamoeba mellificae

A mixed population of cysts, immature cysts, and trophozoites was observed in the lumen of Malpighian tubules of Apis mellifera infected with Malpighamoeba mellificae. The most distinct pathological change in the infected tubules was swelling of the brush border of epithelial cells. In some areas the brush border was broken down into pieces, and in some cases it was completely engulfed by the parasites. The microvilli of the brush border were long and slender in noninfected tubules. Nuclei were not found in the infected tubules, but were frequently observed in the non-infected tubules. Numerous secretion globules were observed in the cytoplasm of epithelial cells of noninfected Malpighian tubules, but not in the cells of infected tubules. Epithelial cells in the infected tubules were destroyed and consumed by the trophozoites of M. mellificae. Trophozoites possessed protrusions and pits on their surfaces; many also had pseudopodia and apparently consumed the host cell by a mechanism of phagocytosis or endocytosis.     

Effects on intestinal nutrient uptake and brush border membrane enzymes in response to atherogenic diet in rhesus monkeys

Transport of nutrients and kinetic parameters (Vmax and Km) of brush border membrane (BBM) enzymes were studied in duodenum, jejunum, and ileum from atherogenic diet-fed monkeys. The Km remained unaltered while feeding of atherogenic diet resulted in higher Vmax of sucrase, maltase, and alkaline phosphatase and lower Vmax of gamma-glutamyltranspeptidase and leucine-aminopeptidase compared to controls. Na+-dependent D-glucose transport was higher in duodenum and jejunum and unaltered in ileum. In contrast to D-glucose transport, the transport of amino acids was decreased in all three intestinal segments from atherogenic diet-fed monkeys.