Critical comparison between modified Monier-Williams and electrochemical methods to determine sulfite in aqueous solutions.

In the present work, known concentration of sulfite aqueous solutions in the presence and absence of gallic acid was measured to corroborate the validity of modified Monier-Williams method. Free and bound-sulfite was estimated by differential pulse voltammetry. To our surprise, the modified Monier-Williams method (also known as aspiration method) showed to be very inaccurate for free-sulfite, although suitable for bound-sulfite determination. The differential pulse approach, using the standard addition method and a correction coefficient, proved to be swift, cheap, and very precise and accurate.

Gallium nitrate inhibits calcium resorption from bone and is effective treatment for cancer-related hypercalcemia.

Approximately two-thirds of patients who receive the anticancer drug gallium nitrate develop mild hypocalcemia. To evaluate the mechanism of drug-induced hypocalcemia, we tested the effects of gallium nitrate upon in vitro release of 45Ca++ from explanted fetal rat bones. The drug significantly inhibited 45Ca++ release in response to stimulation with both parathyroid hormone and a lymphokine preparation with osteoclast activating factor activity. The inhibitory effects on bone resorption were both time- and dose-dependent. Later, in a pilot study, we treated 10 patients who had cancer-related hypercalcemia with gallium nitrate administered by continuous infusion. All patients responded by a reduction of total serum calcium to normal or subnormal concentrations (13.8 +/- 1.05 mg/dl, mean +/- SD pretreatment, to 8.03 +/- 1.03 mg/dl, mean posttreatment nadir). Our results indicate that gallium nitrate effectively treats cancer-related hypercalcemia and that it probably acts by inhibiting calcium release from bone.

Erythropoietin stimulates serine kinase activity in erythropoietin-dependent cells.

Protein phosphorylation is an early event that follows the interaction of erythropoietin (Epo) with its receptor, even though this receptor lacks a kinase domain. To further define the role of protein kinases in Epo-mediated signal transduction, the effect of Epo on serine-threonine kinase activity was examined in the Epo-dependent cell line, HCD-57, using a kinase renaturation assay. In HCD-57 cells synchronized in G0 phase by centrifugal elutriation, multiple serine-threonine kinases were constitutively active, and exposure to Epo was associated with an increase in the activity of kinases with apparent molecular masses of 170, 120, and 90-95 kD. Phosphoamino acid analysis established the covalent incorporation of 32P into serine and threonine for constitutively active kinases and into serine alone for the 90-95 kD kinase. Reelectrophoresis experiments established that 32P incorporation represented kinase autophosphorylation as opposed to protein substrate phosphorylation. Epo-associated serine kinase autophosphorylation was both hormone concentration and time dependent as well as restricted to the G0, G1, and S phases of the cell cycle. Cell fractionation studies localized the activity of the 90-95 kD serine kinase to the plasma membrane.

Protein kinases and phosphatases are involved in erythropoietin-mediated signal transduction.

To study the role of protein phosphorylation in erythropoietin (EPO)-mediated signal transduction, we examined the effects of tyrosine phosphatase and tyrosine and serine-threonine kinase inhibitors as well as activators of serine kinases on DNA synthesis and cell proliferation in the murine EPO-dependent cell line HCD-57. HCD-57 cells were obtained synchronized in G0 by centrifugal elutriation, and DNA synthesis was measured by incorporation of labeled thymidine into DNA. Half-maximal DNA synthesis was stimulated by 0.001 U/ml of EPO. Sodium orthovanadate (Na3VO4), a tyrosine phosphatase inhibitor, at 5 microM potentiated a subsaturating concentration of EPO. Na3VO4 alone stimulated HCD-57 DNA synthesis at concentrations of 0.1-20 microM. Zinc chloride, another tyrosine phosphatase inhibitor, also stimulated HCD-57 DNA synthesis at concentrations of 50-100 microM. Genistein, a tyrosine kinase inhibitor, blocked the effect of EPO at a concentration of 5 micrograms/ml. Bryostatin, a protein kinase C (PKC) activator, stimulated DNA synthesis in HCD-57 cells at concentrations of 10(-9)-10(-10) M, whereas the phorbol ester, phorbol 12,13-dibutyrate (PDBu), was stimulatory only at a concentration of 10(-11) M. Staurosporine, a PKC inhibitor, blocked the effect of EPO at a concentration of 10(-7) M, and H-7, a nonspecific protein kinase inhibitor, was not inhibitory. These agents also had similar effects on the in vitro proliferation of HCD-57 cells. Taken together, the data indicate that the EPO-mediated transition from G0 to S phase in HCD-57 cells involves the activation of both tyrosine and serine-threonine kinases and is modulated by tyrosine phosphatase activity.

Cell cycle-specific behavior of erythropoietin.

The murine erythropoietin-dependent erythroleukemia cell line, HCD-57, was employed to study the cell cycle-specific behavior of erythropoietin. Cell cycle duration for HCD-57 cells was approximately 12 hours and was uninfluenced by erythropoietin. Populations of HCD-57 cells synchronized in G1 by centrifugal elutriation were able to pass through one complete cell cycle in the absence of erythropoietin but, thereafter, arrested in G1 as identified by propidium iodide staining and flow cytometry. Analysis of cell cycle behavior using the metachromic dye acridine orange, however, revealed that HCD-57 cells pass through a G0 cell cycle phase and, like serum-deprived 3T3 cells, actually arrest in G0 when deprived of erythropoietin. Expression of the cell cycle regulatory protein p34cdc2 was invariant throughout the cell cycle in HCD-57 cells. p34cdc2 was constitutively phosphorylated in G0 cells, and this effect was not modified by erythropoietin. Erythropoietin receptor distribution was log normal in HCD-57 cells in each phase of the cell cycle. The affinity of these surface receptors for erythropoietin was essentially invariant throughout the cell cycle, but receptor expression was upregulated in G2M cells as compared with cells in G1 or S phase. Taken together, these data indicate that erythropoietin has an important role in the G0-G1 to S phase transition but, based on receptor expression, is involved in other phases of the cell cycle as well.

Plasmodesmata-located protein overexpression negatively impacts the manifestation of systemic acquired resistance and the long-distance movement of Defective in Induced Resistance1 in Arabidopsis.

Systemic acquired resistance (SAR) is a plant defence response that provides immunity to distant uninfected leaves after an initial localised infection. The lipid transfer protein (LTP) Defective in Induced Resistance1 (DIR1) is an essential component of SAR that moves from induced to distant leaves following a SAR-inducing local infection. To understand how DIR1 is transported to distant leaves during SAR, we analysed DIR1 movement in transgenic Arabidopsis lines with reduced cell-to-cell movement caused by the overexpression of Plasmodesmata-Located Proteins PDLP1 and PDLP5. These PDLP-overexpressing lines were defective for SAR, and DIR1 antibody signals were not observed in phloem sap-enriched petiole exudates collected from distant leaves. Our data support the idea that cell-to-cell movement of DIR1 through plasmodesmata is important during long-distance SAR signalling in Arabidopsis.

Induction of profound hypouricemia by a non-sedating thiobarbiturate.

5-[N-phenylcarboxamido]-2-thiobarbituric acid (merbarone) is a non-sedating derivative of thiobarbituric acid originally developed for anticancer use. In the initial clinical study, a profound reduction in serum uric acid was observed. In 20 patients who received five daily doses of merbarone ranging from 100 to 750 mg/m2, serum uric acid concentration was reduced from a mean pretreatment value of 5.7 +/- 1.6 mg/dL to a mean lowest value of 1.3 +/- 0.5 mg/dL. In most patients, the onset of the effect occurred with 24 hours and was maximal by 48 to 72 hours. Metabolic studies in two patients showed an increase in urinary uric acid excretion within 24 hours after initiation of drug treatment. A marked increase in fractional excretion of uric acid was sustained throughout the period of drug treatment. Urinary excretion of total oxypurines (xanthine and hypoxanthine) was increased twofold to threefold relative to baseline levels. Ultrafiltration studies showed that merbarone did not significantly displace binding of urate from albumin. When merbarone was incubated with xanthine oxidase in vitro, several reaction products were observed, including 2-oxo-2-desthio-merbarone and a compound with retention time similar to 4'-OH-merbarone. Both of these compounds have been described previously as metabolites of merbarone in human subjects. The parent drug and both metabolites were found to inhibit xanthine oxidase (Ki = 41, 36, and 240 mumols/L, respectively). However, this inhibitory effect was substantially less potent than allopurinol (Ki = 0.025 mumols/L). This study indicates that merbarone induces profound hypouricemia primarily by increasing uric acid excretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Carboplatin-based chemotherapy with pharmacokinetic analysis for patients with hemodialysis-dependent renal insufficiency.

Three patients with renal insufficiency requiring hemodialysis were treated with carboplatin at 100 mg/m2 in combination with etoposide for advanced germ-cell tumor (GCT, two cases) or Adriamycin + vinblastine for a transitional-cell carcinoma of the ureter (one case). Hemodialysis was performed 24 h after the administration of carboplatin. Both patients with GCT achieved a complete response, and the patient with transitional-cell carcinoma of the ureter was inevaluable for response but his disease has not progressed. The dose of carboplatin was increased in one patient as renal function improved on therapy. In two patients, the pharmacokinetics of carboplatin were determined; the pre-dialysis half-lives, AUC, and total body clearances of free carboplatin-derived platinum were estimated to be 32 and 18.3 h, 4.93 and 6.17 mg ml-1 min, and 18.2 and 18.7 ml/min, respectively. The dialysis elimination half-lives (t1/2 beta) of 2 and 3 h, respectively, for these two patients were markedly lower than the predialysis values, indicating that carboplatin was dialyzed. In summary, carboplatin can be given to patients with severe renal insufficiency. Adequate AUCs were achieved and dialysis limited systemic exposure to free carboplatin.

A sampling device for septum-sealed blood containers.

The device described replaces the sampling probe of any automatic diluter. It enables septum-sealed blood vials to be sampled without exposing the blood to the atmosphere, and dispenses the blood into sealed reaction vials. The advantages are that loss of volatiles in the sample and exposure of operators to open blood containers are eliminated.

Stereotyping by children of the effects of drinking on adults.

Responses on a semantic differential questionnaire indicated that 12-year-olds had formed stereotypes about the effects of alcohol on adults and that these stereotypes were generally negative.

College students' expectations of the results of drinking.

Social drinkers, when drinking, are expected to feel better and to be kinder, more fun to be with and more energetic and active than they would be if they were not drinking; inebriated alcoholics are expected to be meaner, less fun to be with and more lethargic than they would be if they were not inebriated.

In vitro effects of thawing fresh-frozen plasma at various temperatures.

Thawing fresh-frozen plasma (FFP) in South Africa is uncontrolled because the plasma is issued frozen from the blood bank and thawing techniques and temperatures are at the discretion of the clinician. Following anecdotal reports of disseminated intravascular coagulation (DIC) developing in patients who received FFP thawed in an uncontrolled manner, the effects of various thawing temperatures on coagulation parameters were studied. Fifteen adult units of FFP were each divided into 4 satellite units by the South African Blood Transfusion Service before freezing at -25 degrees C. These bags were then defrosted in a waterbath at 22 degrees C, 37 degrees C, 45 degrees C and 60 degrees C, respectively, and removed as soon as they had thawed. Samples were collected for measurement of International Normalized Ratio (INR), prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and D-dimers. These tests were done according to standard operating procedures. FFP samples were also used in place of agonist in platelet aggregation studies to assess whether the FFP could induce platelet aggregation. Results were analyzed with the percentage similarity model. Using this method the percentage similarity (%sim) of each bag thawed at each temperature with the same donor's bag thawed at 37 degrees C was calculated. The mean, standard deviation, and percentage coefficient of variation of the percentage similarities were then derived. Data sets were also compared using the Wilcoxon test. The fibrinogen values remained stable at 22-45 degrees C (%sim = 97-99%) while there was a significant decrease in fibrinogen levels at 60 degrees C compared with 37 degrees C (p<0.001, %sim = 75%). INR and PTT values were highest in the bags thawed at 60 degrees C (%sim = 114% and 110%, respectively) with the difference between the INR levels at 60 degrees C compared with 37 degrees C showing statistical significance (p<0.05). D-dimers were high at all temperatures tested with widely ranging results at each temperature. The FFP did not induce platelet aggregation at any of the thawing temperatures. In summary, INR and PTT values increase at a thawing temperature of 60 degrees C compared with 37 degrees C. D-dimers are elevated in thawed FFP. Fibrinogen levels are markedly decreased in FFP thawed at 60 degrees C compared with that thawed at 37 degrees C. FFP should be thawed at 37 degrees C in a strictly controlled environment.

Guideline for the diagnosis and management of multiple sclerosis: a Southern African perspective.

Before making a diagnosis of multiple sclerosis (MS), it is imperative that alternative diagnoses are considered and excluded. This is particularly important in South Africa, which is a moderate prevalence MS area, has a high burden of neurological infections and where the majority of the people are black - an ethnic group that has a very low frequency of MS. Before applying diagnostic criteria, there should be no better explanation for the patient's presentation. This guideline, written on behalf of the Multiple Sclerosis Society of South Africa, aims to assist in the diagnosis and treatment of MS in Southern Africa.