Modifications to United States Environmental Protection Agency Methods 1622 and 1623 for Detection of Cryptosporidium Oocysts and Giardia Cysts in Water

Collaborative and in-house laboratory trials were conducted to evaluate Cryptosporidium oocyst and Giardia cyst recoveries from source and finished-water samples by utilizing the Filta-Max system and U.S. Environmental Protection Agency (EPA) methods 1622 and 1623. Collaborative trials with the Filta-Max system were conducted in accordance with manufacturer protocols for sample collection and processing. The mean oocyst recovery from seeded, filtered tap water was 48.4% ± 11.8%, while the mean cyst recovery was 57.1% ± 10.9%. Recovery percentages from raw source water samples ranged from 19.5 to 54.5% for oocysts and from 46.7 to 70.0% for cysts. When modifications were made in the elution and concentration steps to streamline the Filta-Max procedure, the mean percentages of recovery from filtered tap water were 40.2% ± 16.3% for oocysts and 49.4% ± 12.3% for cysts by the modified procedures, while matrix spike oocyst recovery percentages ranged from 2.1 to 36.5% and cyst recovery percentages ranged from 22.7 to 68.3%. Blinded matrix spike samples were analyzed quarterly as part of voluntary participation in the U.S. EPA protozoan performance evaluation program. A total of 15 blind samples were analyzed by using the Filta-Max system. The mean oocyst recovery percentages was 50.2% ± 13.8%, while the mean cyst recovery percentages was 41.2% ± 9.9%. As part of the quality assurance objectives of methods 1622 and 1623, reagent water samples were seeded with a predetermined number of Cryptosporidium oocysts and Giardia cysts. Mean recovery percentages of 45.4% ± 11.1% and 61.3% ± 3.8% were obtained for Cryptosporidium oocysts and Giardia cysts, respectively. These studies demonstrated that the Filta-Max system meets the acceptance criteria described in U.S. EPA methods 1622 and 1623.     

Regulation of principal cell pH by Na/H exchange in rabbit cortical collecting tubule

Summary Changes in intracellular pH (pH _i ) were measured using the pH indicator, BCECF, in principal cells from split opened cortical collecting tubules (CCTs) derived from rabbits maintained on a normal diet. This monolayer preparation has the advantage of allowing us to visualize the morphological differences in the two major cell types in this nephron segment under transmitted light. The visual identification of the cell types was verified using emission measurements taken from single principal and intercalated cells in the opened tubule which had been exposed to fluorescein isothiocyanate (FITC)-labeled peanut lectin. We confirmed the existence of an amiloride-sensitive Na/H exchange process activated during intracellular acidosis in principal cells. In addition, the exchanger was active under basal conditions and over a wide range of pH _i . Because the exchanger was active under basal conditions we tested the hypothesis that changes in intracellular Na (Na _i ) would alter pH _i in a predictable way. Maneuvers designed to alter Na _i were without significant effects within a 10-min time frame. Specifically, addition of 100 m ouabain to increase Na _i or exposure of the tubules to 10^–5 m amiloride to decrease luminal Na entry and reduce Na _i did not have an effect on pH _i . In some experiments we did observe however, after a 30-min exposure to ouabain, a small decrease in pH _i . These results suggest that Na/H exchange is a major regulator of pH _i in principal cells. However, regulation of Na transport by changes in pH _i in principal cells of rabbit CCT via the activity of a Na/H exchanger do not seem to contribute to the feedback control of Na transport.This work was supported by U.S. Public Health Service grants DK27847 to L.G. Palmer and DK11489 to E.E. Windhager.     

Effect of neurotensin on pancreatic function in man

The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.     

Effect of Metalaxyl on the incidence and severity of Pearl millet downy mildew disease in Northern Nigeria

Pearl millet downy mildew (DM) incidence, severity and yield losses of two pearl millet varieties (local and improved) due to the disease were determined in the field. Significant differences in the disease incidence and severity were recorded in the plots sown with metalaxyl-treated seeds and those sown with non-treated seeds, indicating the efficacy of the fungicide on the fungus. Yield losses due to non-treatment of seeds with metalaxyl was 40.88 and 45.39% in a local variety and 43.00 and 18.60% in an improved variety in the 2000 and 2001 cropping seasons respectively. Significant differences between plots sown with metalaxyl-treated and those sown with non-treated seeds were obtained for other yield components such as 1000-grains weight, panicle length and weight.     

Signaling of Ankle Joint Position by Receptors in Different Muscles

Plots were made of multiunit activity versus ankle joint position for receptors in each of the 12 muscles crossing the cat ankle joint, except peroneus tertius, by recording from populations of afferent fibers in muscle nerves. The discharge was measured 15 or 30 sec after terminating the movements that altered the position of the joint. These recordings were dominated by large-spike activity that would be expected to originate mainly from primary spindle endings. Seven of the 12 muscles also cross other joints. Their responses at a given ankle joint position were so altered by changes in the position of the knee or toe joints that they could not reliably signal the position of the ankle joint. As judged from multiunit recording, receptors in each of the five muscles specific to the ankle joint were influenced by more than one axis of ankle joint displacement.

Single-unit recording from dorsal root filaments was used to determine whether primary or secondary spindle receptors in soleus and tibialis anterior could selectively signal one axis of ankle joint rotation. Individual soleus receptors were tested both on the flexion extension axis and with a combined adduction–eversion movement.

For 38 of the 70 soleus receptors examined (54%), firm adduction–eversion produced a level of activity greater than that caused by 10° of flexion, and for 77% the level of activity was greater than that caused by 5° of flexion. For 168 of the 184 tibialis anterior receptors studied (91%), firm abduction inversion produced a level of activity greater than that caused by 10° of extension. Thus few receptors were found that responded exclusively to one axis of rotation.

One way in which the position of the ankle joint could be specified in the face of multiaxial receptor activity is by examining the receptor discharge from more than one muscle. A suggestion for how the nervous system might do this is given in the discussion.     

Efficiency of Cell-Free and Cell-Associated Virus in Mucosal Transmission of Human Immunodeficiency Virus Type 1 and Simian Immunodeficiency Virus

Effective strategies are needed to block mucosal transmission of human immunodeficiency virus type 1 (HIV-1). Here, we address a crucial question in HIV-1 pathogenesis: whether infected donor mononuclear cells or cell-free virus plays the more important role in initiating mucosal infection by HIV-1. This distinction is critical, as effective strategies for blocking cell-free and cell-associated virus transmission may be different. We describe a novel ex vivo model system that utilizes sealed human colonic mucosa explants and demonstrate in both the ex vivo model and in vivo using the rectal challenge model in rhesus monkeys that HIV-1-infected lymphocytes can transmit infection across the mucosa more efficiently than cell-free virus. These findings may have significant implications for our understanding of the pathogenesis of mucosal transmission of HIV-1 and for the development of strategies to prevent HIV-1 transmission.