A first report of Pseudosuccinea columella (Say, 1817), an alien intermediate host for liver fluke, in Malawi.

Starting in October 2021, quarterly malacological surveys have been undertaken in Malawi, with the sampling of 12 specified freshwater habitats throughout a calendar year. Each survey monitors the presence of aquatic intermediate snail hosts of medical and veterinary importance. In March 2023, the alien lymnaeid species Pseudosuccinea columella was encountered for the first time in the surveys, in Nsanje District. This species identity was later confirmed upon DNA analysis of mitochondrial ribosomal 16S sequences. In July 2023, P. columella was also noted at single sites within Mangochi and Chikwawa Districts, and again in Nsanje District, with an additional location observed. Of particular importance, our sampled location in Mangochi District was directly connected to Lake Malawi, which expands the species list of invasive molluscs in this lake. While P. columella is a well-known intermediate snail host for human and animal fascioliasis, screening collected snails for trematode cercariae, alongside molecular xenomonitoring, did not yield equivocal evidence of active fluke infection. However, the newly recognized presence of this alien intermediate snail host within Lake Malawi, and along the Shire River Valley, flags a new concern in altered local transmission potential for human and animal fascioliasis.

An alien intermediate snail host in Malawi - Orientogalba viridis (Quoy and Gaimard, 1832) - A new concern for schistosomiasis transmission in Africa?

The freshwater amphibious snail Orientogalba viridis commonly occurs in eastern Asia, on certain Pacific islands and more importantly has recently dispersed into Europe. Since this snail is now considered an invasive species, its distribution is of growing parasitological interest as an alien intermediate host for various trematodes, particularly liver flukes. As part of ongoing surveillance for snail-borne diseases in Malawi, a population of O. viridis was first observed in May 2023, alongside an alarming presence of a human schistosome cercaria. This snail population later underwent detailed morphological characterisation with both snail and parasite identities confirmed upon DNA barcoding. This seminal observation triggered more extensive local snail surveys, finding 3 further populations in separated rice paddies, with further field-caught snails (n = 465) screened for infection and a selection used for repeated experimental challenges with miracidia from Schistosoma haematobium and Schistosoma mattheei. Although no field-caught (and experimentally exposed) snail was seen to shed schistosome cercariae, molecular xenomonitoring for schistosomiasis provided tangible evidence of putative transmission potential. Our first report of O. viridis here in Malawi, and more broadly in Africa, flags a need for increased vigilance for this invasive species alongside local clarification(s) of its transmission potential for trematodiases of either medical and/or veterinary importance.

Antisense expression of a cell wall-associated protein kinase, WAK4, inhibits cell elongation and alters morphology.

The Arabidopsis cell wall-associated receptor-like kinase (WAK) gene family contains five highly related members whose products are suited for exchanging signals between the intracellular and extracellular compartments. WAK members are expressed in specific organs and regulated differentially by various biotic and abiotic factors. To gain further insight into how WAKs function during development, we used a glucocorticoid-inducible system to express ectopically the WAK4 antisense gene. The induced expression of the WAK4 antisense gene resulted in a significant decrease of WAK proteins. Ninety-six hours after the induction of WAK4 antisense expression, WAK proteins became undetectable. Cell elongation was impaired, and lateral root development was blocked. The level of WAK protein could be controlled by the concentration of the applied inducer, dexamethasone, and was correlated with the severity of the cell elongation inhibition phenotype. These results suggest that the WAKs serve a vital role in cell elongation and are required for plant development.

Estimation of aerobic capacity from submaximal cycle ergometry in women.

Simple, valid, and reliable methods of estimating maximal oxygen uptake (VO2max) are needed for epidemiologic studies of physical activity, to evaluate fitness for job performance, and to assist in prescription of exercise. Such estimations in women have not received due research attention. Heart rate responses to submaximal cycle ergometry and VO2max during maximal treadmill and cycle ergometer testing were measured in 37 healthy women aged 19-47 yr (X = 31.7 +/- 7.9). The submaximal test was very reliable on retest (r = 0.92), but overestimated measured treadmill VO2max (X = 2.42 vs 2.23 l.min-1; r = 0.76, SEE = 0.229). The submaximal test also greatly overestimated maximal cycle ergometer VO2max (X = 2.42 vs 2.06 l.min-1; r = 0.70, SEE = 0.340). Similar 8.5% (treadmill) and 18.5% (cycle ergometer) overestimation by the submaximal test were found for VO2max relative to body weight. A simple submaximal exercise test is highly reliable as an estimate of VO2max when used for women. It also provides a reasonably good estimate of treadmill measured VO2max.

Bone mineral content in Hawaiian, Asian, and Filipino children.

Os calcis bone mineral content (BMC) was measured by single photon absorptiometry in 86 children, ages 6 to 13 years from Hawaiian, Oriental, Caucasian, and Filipino ethnic groups. Pearson correlations indicated significant positive correlations between BMC and age, height, and weight. However, there were no significant differences in age, height or weight between ethnic groups. ANOVA revealed a significant effect of ethnic group on BMC with the Hawaiian group having a significantly higher BMC than the Asian or Caucasian groups. When age, height and weight were controlled for, ANCOVA still showed a significant effect of ethnicity on BMC. The current findings suggest that ethnic differences can develop early in life.

Comparison of treadmill exercise testing protocols for wheelchair users.

The reduced early mortality and the increased life span of persons with spinal cord injury (SCI) and other chronically disabling conditions which result in loss of use of the legs places them at increased risk of coronary heart disease, diabetes, and hypertension. Exercise testing in this population is becoming more common, but there is a need for assessment of protocols in order to determine the best method to elicit a maximal response in a reasonable time without endangering the patient. Three wheelchair treadmill protocols were compared in seven men with paraplegia aged 21-44 years (five SCI, two post-polio). Subjects repeated each protocol to estimate reliability. Protocol G consisted of increasing treadmill grade at a constant speed (4.8 km.h-1); in protocol S, the speed was increased at a constant grade (0%), and in protocol C, speed and grade were increased. Two-minute stages were used in all protocols. Peak oxygen uptake [VO2max; mean (SD): 23.6 (5.8) ml.kg-1 x min-1; 1.66 (0.37) l.min-1], VCO2 production [1.98 (0.46) l.min-1], ventilation volume [83.0 (25.6) l.min-1], respiratory exchange ratio [1.2 (0.12)], and heart rate [173 (18)] were determined. Over all trials none of the variables was significantly different among the three protocols, but all were highest in C and lowest in S. Reliability coefficients for absolute and relative VO2max ranged from 0.76 and 0.81 in G to 0.95 and 0.98 in C (all P < 0.05). These data suggest that an incremental treadmill test similar to the C protocol may be the optimal method to use when evaluating the exercise capacity of wheelchair users.

The effects of oral contraceptives on respiration.

The effect synthetic progestins found in current oral contraceptives may exert on respiratory function has not been thoroughly investigated. This study monitored potential changes in respiratory parameters 3 and 6 months subsequent to beginning administration. Static and timed spirometric maneuvers showed significant increases in only tidal volume (P = 0.01). Ventilatory response to treadmill exercise monitored the oxygen uptake, CO2 elimination (VCO2), minute ventilation (VE), and respiratory exchange ratio at each of four workloads. An analysis of the covariance (ANCOVA) for the slopes revealed no significant variation between test periods. The ANCOVA for the means showed increases in VE and VCO2. These results suggest a stimulatory role for synthetic progestins, although ventilatory performance in response to moderate exercise does not appear compromised.

On the use of oxygen to facilitate decompression.

Oxygen is widely used at elevated partial pressures to facilitate decompression, yet the optimum dosage and the magnitude of the beneficial effects are poorly known. This is because oxygen enhancements, expressed as increases in the allowed pressure reductions, are small and easily masked by individual variation. Furthermore, oxygen can also produce detrimental results, and the range from a therapeutic to a toxic dose is narrow. Berhage and McCracken recently reported two massive investigations involving 1185 rats and 60 experimental conditions. These authors suggest that the conventional concept of an "equivalent air depth" (EAD) is untenable and that oxygen must be considered in calculating the totat tissue gas tension. We find instead that the observations of Berghage and McCracken are compatible with a model in which the tensions of oxygen and carbon dioxide dissolved in tissue are taken into account, and that this model, in turn, agrees with EAD predictions of oxygen enhancements for subtoxic oxygen pressures.

Respiratory volume-time relationships during resistive loading in the cat.

The first-breath (neural) effects of graded resistive loads added separately during inspiration and expiration was studied in seven anesthetized cats before and after bilateral vagotomy. Additions of airflow resistance during inspiration reduced the volume inspired (VI) and increased inspiratory duration (TI). The duration of the ensuing unloaded expiration (TE) was unchanged. Vagotomy eliminated the TI modulation with inspiratory loads. Tracheal occlusion at the onset of inspiration yielded TI values similar to the fixed values observed following vagotomy. Resistive loads added during expiration produced similar results. Expired volume (VE) decreased and (TE) increased approaching the values obtained after vagotomy. Unlike the inspiratory resistive loads, loading during expiration results in an upward shift in the functional residual capacity (FRC). The FRC shift produces a time lag between the onset of diaphragmatic (EMG) activity and the initiation of airflow of the next (unloaded) inspiration. These studies suggest separate volume-time relationships for the inspiratory and expiratory phases of the breathing cycle. Both relationships are dependent upon vagally mediated volume feedback.