Total Body Potassium in Long-Term Frusemide Therapy: Is Potassium Supplementation Necessary?

Measurements of total body potassium (T.B.K.) were made by whole-body counting in four groups of patients receiving oral frusemide for one year. Patients in group 1 had essential hypertension and normal renal function and received 40 mg frusemide daily without potassium supplements. Patients in group 2 were similar but received oral potassium supplements for the first four months of treatment. Patients in group 3 had hypertension associated with renal disease and received 120 mg frusemide daily without potassium supplements. Patients in group 4 also had hypertension and renal impairment and in addition to 120 mg frusemide daily they received oral potassium supplements for four months. No evidence of depletion of T.B.K. was found in any of the groups after continuous treatment with frusemide for one year. It is questioned whether potassium supplementation in long term diuretic therapy with frusemide is necessary unless there is evidence of pre-existing potassium depletion or of some other factor such as cardiac failure, cirrhosis of the liver, or the nephrotic syndrome.     

Studies on the Thermal Destruction of Escherichia coli in Milk and Milk Products

Escherichia coli (ATCC no. 9637) was shown to have mean D values (slope of destruction rate curve) of 28.2, 5.1, 1.3, 0.00195, 0.00100, 0.00055, 0.00029, and 0.00016 min in milk at temperatures of 125, 130, 135, 168, 170, 172, 174, and 176 F, respectively. The mean D values for this organism in chocolate milk were 32.2, 10.4, 2.6, 0.00265, 0.00133, 0.00069, 0.00035, and 0.00028 min at respective temperatures of 125, 130, 135, 168, 170, 172, 174, and 176 F. Mean D values of 34.4, 10.0, 3.5, 0.00093, 0.00080, 0.00068, 0.00043, and 0.00036 min were found in cream for respective temperatures of 125, 130, 135, 168, 170, 172, 174, and 176 F. In ice cream mix the organism was found to have mean D values of 39.3, 15.2, 5.1, 0.00147, 0.00120, 0.00078, 0.00070, and 0.00053 min for temperatures of 125, 130, 135, 170, 172, 174, 176, and 178 F, respectively. The slopes of the thermal death time curves were found to be 10.2, 10.2, 10.0, and 10.3 F for this organism in milk, chocolate milk, 40% fat cream, and ice cream mix, respectively.     

Sulfadoxine resistance in the human malaria parasite Plasmodium falciparum is determined by mutations in dihydropteroate synthetase and an additional factor associated with folate utilization

Sulfadoxine/pyrimethamine (Fansidar) is widely used in Africa for treating chloroquine-resistant falciparum malaria. To clarify how parasite resistance to this combination arises, various lines of Plasmodium falciparum were used to investigate the role of naturally occurring mutations in the target enzyme, dihydropteroate synthetase (DHPS), in the parasite response to sulfadoxine inhibition. An improved drug assay was employed to identify a clear correlation between sulfadoxine-resistance levels and the number of DHPS mutations. Moreover, tight linkage was observed between DHPS mutations and high-level resistance in the 16 progeny of a genetic cross between sulfadoxine-sensitive (HB3) and sulfadoxine-resistant (Dd2) parents. However, we also demonstrate a profound influence of exogenous folate on IC₅₀ values, which, under physiological conditions, may have a major role in determining resistance levels. Importantly, this phenotype does not segregate with dhps genotypes in the cross, but shows complete linkage to the two alleles of the dihydrofolate reductase ( dhfr ) gene inherited from the parental lines. However, in unrelated lines, this folate effect correlates less well with DHFR sequence, indicating that the gene responsible may be closely linked to dhfr , rather than dhfr itself. These results have major implications for the acquisition of Fansidar resistance by malaria parasites.     

In vitro shoot proliferation of 5-leaf aralia explants from field grown plants and forced dormant stems

A. Sieboldianus (5-leaf aralia) is recalcitrant for micropropagation, but has very good landscaping potential. This research was conducted with the following objectives: (1) to study effects of BA, TDZ, CPPU, 2iP, kinetin and zeatin in woody plant medium on the performance of softwood shoot nodal explants produced by field grown 5-leaf aralia plants; (2) to investigate influences of BA or TDZ in the forcing solution on subsequentin vitro shoot initiation of nodal explants taken from forced softwood growth. Shoot initiation of softwood nodal explants from field-grown plants was promoted by adding BA, TDZ or CPPU to the culture medium. Kinetin, zeatin and 2iP were ineffective for micropropagation ofA. Sieboldianus. The forced softwood growth for use as explants was “primed” by forcing dormant stems in solution containing 200 mg 8-HQC per liter plus 2% sucrose, 44.4, 222, or 444 μM BA, or 45.4, 227, or 454 μM TDZ. BA and TDZ in the forcing solution enhanced subsequentin vitro axillary shoot initiation of nodal explants taken from forced stems by doubling the number of shoots produced per explant to 3.3 from 1.65 shoots per explant taken from field grown plants. This forcing solution technique also reduced the time needed from culture initiation to potted plants to half of the time needed for the conventional micropropagation method (12 to 14 vs. 25 to 27 weeks), thus expediting the micropropagation ofA. Sieboldianus.     

Brachydactyly and Mental Retardation: An Albright Hereditary Osteodystrophy–like Syndrome Localized to 2q37

We report five patients with a combination of brachymetaphalangia and mental retardation, similar to that observed in Albright hereditary osteodystrophy (AHO). Four patients had cytogenetically visible de novo deletions of chromosome 2q37. The fifth patient was cytogenetically normal and had normal bioactivity of the α subunit of Gs (Gsα), the protein that is defective in AHO. In this patient, we have used a combination of highly polymorphic molecular markers and FISH to demonstrate a microdeletion at 2q37. The common region of deletion overlap involves the most telomeric 2q marker, D2S125, and extends proximally for a maximum distance of 17.6 cM. We suggest this represents a consistent phenotype associated with some deletions at 2q37 and that genes important for skeletal and neurodevelopment lie within this region. Screening for deletions at this locus should be considered in individuals with brachymetaphalangia and mental retardation. Furthermore, 2q37 represents a candidate region for type E brachydactyly.     

Calcium Channel Activity during Pollen Tube Growth and Reorientation

We have shown previously that the inhibition of pollen tube growth and its subsequent reorientation in Agapanthus umbellatus are preceded by an increase in cytosolic free calcium ([Ca2+]c), suggesting a role for Ca2+ in signaling these processes. In this study, a novel procedure was used to measure Ca2+ channel activity in living pollen tubes subjected to various growth reorienting treatments (electrical fields and ionophoretic microinjection). The method involves adding extracellular Mn2+ to quench the fluorescence of intracellular Indo-1 at its ca2+-insensitive wavelength (isosbestic point). The spatial and temporal kinetics of Ca2+ channel activity correlated well with measurements of [Ca2+]c dynamics obtained by fluorescence ratio imaging of Indo-1. Tip-focused gradients in Ca2+ channel activity and [Ca2+]c were observed and quantified in growing pollen tubes and in swollen pollen tubes before reoriented growth. In nongrowing pollen tubes, Ca2+ channel activity was very low and [Ca2+]c gradients were absent. Measurements of membrane potential indicated that the growth reorienting treatments induced a depolarization of the plasma membrane, suggesting that voltage-gated Ca2+ channels might be activated.     

Analysis of whole-cell fatty acid profiles of verotoxigenic Escherichia coli and Salmonella enteritidis with the microbial identification system.

Differentiation of strains within bacterial species, based on gas chromatographic analysis of whole-cell fatty acid profiles, was assessed with 115 strains of verotoxigenic Escherichia coli and 315 strains of Salmonella enteritidis. Fatty acid-based subgroups within each of the two species were generated. Variability of fatty acid profiles observed in repeat preparations from the same strain approached that observed between subgroups, limiting the usefulness of using fatty acid profiles to subgroup verotoxigenic E. coli and S. enteritidis strains.     

A sensitive solid phase enzymeimmunoassay for testosterone in plasma and saliva.

A sensitive, solid phase enzymeimmunoassay suitable for determining testosterone concentrations in samll aliquots of plasma (20 microliter) and saliva (200 microliter) has been developed. A solid phase antiserum raised against a testosterone-11 alpha-hemisuccinate/bovine serum albumin conjugate was prepared by coupling to cyanogen bromide activated cellulose. The "enzyme label" was a covalently linked testosterone/horseradish peroxidase conjugate. The assay had a lower limit of sensitivity of 4pg/assay tube and satisfied accepted criteria of specificity and precision. Testosterone concentrations determined by enzyme-immunoassay were in excellent agreement not only with a gas liquid chromatography/mass spectrometry procedure (r=0.96, n=12) but also with the radioimmunoassay in routine use (r=0.95, n=12). The EIA can therefore replace RIA in both the small clinical laboratory and high throughput service centres for determining plasma and salivary testosterone concentrations. In normal males salivary testosterone concentrations reflected circulating steroid levels and indicated the possibility of assaying saliva rather than plasma in clinical studies.