Mass screening

The outlook for patients who are treated at an early age is favorable. Affected babies are normal at birth but almost all will be impaired unless they receive dietary restriction by age 3 months. Mass screening has largely eliminated the untreated PKU phenotype of eczema, poor growth, irritability, musty odor (caused by phenylacetic acid) and tendency to self-mutilation. Progressive motor dysfunction has been described in children with longterm hyperphenylalaninemia. 

Sieves are used in screen, or sieve, analysis. This is an inexpensive and reliable method for classifying larger particles based on size and mass. Screen analyses are generally used for quality control and analytical work and find use in a wide variety of industries. They are not suitable for emulsions, sprays, or very fine powders (<0.05 mm in diameter). 

The steps in the development of anticancer drugs from (marine) organisms are schematically shown in Fig. 7. The most important step in the selection process is initial mass screening. The screening methods can either be simple, such as tumor cell line or enzymatic (e.g., topoisomerase inhibition, microtubule as-sembly/dissassembly) tests, or more complex, such as an animal tumor in vivo. 

Schuster et al. (21) identified cotton plant resistance to the two-spotted spider mite (Tetranycus urtlca Koch) by mass screening seedlings. Later Schuster and Lane (22) were able to show that high tannin lines, particularly TX-1055, showed resistance to this arachnid and the bollworm. 

Iwata S, Sukegawa K, Sasaki T, Kokuryu M, Yamasita S, Noma A, Iwasa S, Kondo N, Orii T (1997) Mass screening test for mucopolysaccharidoses using the 1,9-dimethylene blue method positive interference from paper diapers. Clin Chim Acta 264 245-250... 

When taking samples for the determination of enantiomeric purity in a kinetic resolution, it is mandatory to choose the proper time window, e. g., when conversion is between 20% and 80%. If the process of directed evolution leads to enzyme variants differing widely in activity, mass screening needs to be time-resolved, i.e., several samples of a given reaction should be taken as a function of time. 

Can be used for single sample analysis or for mass screening. Screening potential is as high as 3000 samples per day per person. 

If microreactors, either as components or integrated systems, will run in parallel as an array, new solutions for feeding or dispensing systems have to be developed. This is also true for the process control of a large number of product streams which will be a challenge for realization. Tomorrow s answers to these questions will determine which type of microreactor will be favored and will specify the major applications, either simulation of processes, synthetic production or mass screening. 

The activities are at present related to two major topics, namely chemical production and mass screening [3, 8, 25]. While miniaturization in the first field focuses on new process regimes due to enhanced heat and mass transfer, the second field of application results in an increase of reaction and detection units per reactor volume. Thus, miniaturization - the reduction of characteristic dimensions - directly influences the process performance in the first case, while in the last case this is only indirect by an increase in flexibility and multiplicity. 

Chemical activities in the field of mass screening are often related to combinatorial chemistry [51,52]. One major goal, especially in the field of solid phase chemistry involving polymers like DNA or peptides, aims at the increase in the number of compounds per reactor volume and time. Commercially available microtiter plates are established as reactors in this case whereby robotic feed systems fit perfectly to their dimensions. A drastic reduction of reaction volume and increase in number of reaction vessels ( wells ) leads to the so-called nanotiter plates (e.g. with 3456 wells). Microfabrication methods such as the LIGA process are ideal means for the cost effective fabrication of nano-titer plates in polymeric materials by embossing or injection molding techniques so that inexpensive one-way tools are realized. 

Llorens, O., Perez, J.J., and Villar, H.O., Toward the design of chemical libraries for mass screening biased against mutagenic compounds, J. Med. Chem., 44, 2793-2804, 2001. 

During the past 20 years, neonatal screening programs using the Guthrie test for inborn errors of metabolism such as phenylketonuria have become more widely used. The characteristics of diseases in which mass screening is... 

Table 9 lists various congenital disorders and the immunoassay methods recommended for their mass screening. Most of the substances listed in Table 9 have been measured by radioimmunoassay, but a nonisotopic immunoassay such as enzyme immunoassay is now recommended. Sections 7.1 and 7.2 describe examples of mass screening by enzyme immunoassay. 

Because the irreversible mental retardation caused by neonatal hypothyroidism can be prevented by early treatment with thyroid hormone, the importance of early diagnosis of this disease has been emphasized. The difficulty of its early diagnosis by clinical features alone and its relatively high incidence have prompted the organization of various mass screening programs that include measuring thyroxine (T4) (D5) or TSH (13, Mil) by radioimmunoassay. 

Table 10 gives a list of enzyme immunoassays of substances related to neonatal hypothyroid screening. The methods for measuring substances in dried blood can be used for mass screening and those for tests on serum can be used for babies who are recalled. 

One is a competitive double-antibody solid-phase method using perox-idase/TSH conjugates, which was reported by Kato et al. (K3). Their pilot study on mass screening for neonatal hypothyroidism has been successful. 

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