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Protoplasts of complementing auxotrophs of Candida albicans can fuse in the presence of polyethylene glycol and generate prototrophic cells. The yields of prototrophs from fusion mixtures depend greatly on the particular combinations of auxotrophies involved but not on other features of the strain backgrounds of protoplasts. The initial cellular products of fusions isolated on selective media are heterokaryons which replicate slowly but also segregate single parental nuclei into blastospores in high frequency. Karyogamy within heterokaryons produces hybrid nuclei which, on segregation, give rise to rapidly growing, uninucleate substrains. Analyses of the substrains show that hybrid nuclei either stabilize as diploid or undergo random loss of chromosomes to stabilize at various levels of aneuploidy prior to segregation. Chromosome losses and radiation induced mitotic crossing-over can effect recombination for parental auxotrophic markers in hybrids; patterns of recombination for ader and arg markers provide the first documented example of chromosomal linkage in C. albicans. Thus, protoplast fusions offer opportunities otherwise unavailable for applying the incisive tools of genetic recombination to analysis of this important, asexual yeast.

Interpretation of drug testing results is a challenging and complex task, particularly when the interpretation can result in establishing legitimate use of a drug or illicit use with all of its attendant complications (i.e., loss of job, criminal prosecution, etc.). One of the more challenging drugs to interpret is methamphetamine. While methamphetamine is a schedule II controlled substance, the l-enantiomer of methamphetamine is found in the Vick's Inhaler, which is a product exempted from control. For this reason, while identification of methamphetamine and amphetamine in the urine of an individual can clearly establish the use of methamphetamine, it does not prove the use of a controlled substance. Use of racemic methamphetamine can make the interpretation even more difficult because of the different metabolism and excretion of l- and d-methamphetamine. Enantiomeric characterization of methamphetamine may not give unequivocal results. Evaluation of experimentally derived and published data from urine samples containing l- and d,l-methamphetamine indicates that use of the enantiomeric distribution of amphetamine affords unambiguous interpretation. Because the l-enantiomer is the only possible finding in an individual who is using the Vick's Inhaler, detection of the d-enantiomer or a mixture of the d- and l-enantiomers clearly establishes the use of a controlled substance. Without a prescription from appropriate medical personnel, this detection would indicate the illicit use of a controlled substance.

A variety of chemical agents were evaluated to determine their effects on fluorescence polarization immunoassays for drugs of abuse. Sixteen different agents, at concentrations up to 10%, were tested against urine assays for cannabinoids, cocaine (metabolite), amphetamines, opiates, phencyclidine (PCP), and barbiturates. The potential to cause both false positive and false negative results was evaluated, and assays were performed one and seven days after sample adulteration to simulate different collection/testing formats. All six drug assays were susceptible to one or more adulterating agents, but the degree varied considerably between assays. The cannabinoid assay was most susceptible to adulterant-induced false negative results, and the barbiturate assay was most susceptible to false positive results. The remaining assays demonstrated relatively few, but characteristic effects, some of which were attributable to drug degradation and others to assay interference. Although the results of pH measurement on adulterated samples verified its utility in identifying some samples adulterated with interfering agents, other adulterants that cause substantial effects would not be identified by pH measurements alone.

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