a plasmid's ability to replicate. There are other mutations that make the or ganism dependent on chemicals that do not exist in the human gut." Bacteriophage is a DNA vector some workers prefer to use instead of plasmids. "There is [as yet] no evidence that bacteriophage carries any genetic material harmful to man," the report notes. "Large quantities of it have been ingested and shown not to survive in the human intestine. Its capacity to incorporate new genetic information is limited. This allows a stricter control over what is incorporated into the host
bacterium. Moreover, its host range is more restricted than that of plasmids." Lord Ashby's working party realizes that many throughout the world are engaged in genetic manipulation tech nique studies. "They are comparatively easy to master and do not need expen sive equipment. We hope, therefore, that there may be agreement, perhaps through the International Council of Scientific Unions, on the conditions under which the genetical manipulation of microorganisms should be carried out." DermotA. 0'Sullivan, C& Ε Ν London
New blood test can screen for lead poisoning Gaining insights relevant to communi cations is the overall aim of research on the structure and interaction of large molecules being carried out by scientists in the biophysics research di vision at Bell Telephone Laboratories. But along the way, scientists there have found as a fallout of that research a new quick and easy blood test for lead poisoning and an instrument to carry out the test. The test is based on the action of zinc protoporphyrin in blood. Concen tration of the compound increases dra matically as the level of lead in the body increases. When irradiated with blue light, the zinc protoporphyrin flu oresces, giving off red light. A practical testing fluorometer developed by scien tists at Bell Labs puts this phenome non to work. Because the test can detect quickly whether a person has absorbed undue amounts of lead, it can be used for screening to identify immediately those who should be tested further. All that's required for the test is a drop of blood from a pin-pricked finger. The drop of blood simply is placed on a glass slide in the proper spot and the slide insert ed into the fluorometer. Currently, screening tests for blood lead levels are carried out mostly by using direct analysis by atomic absorp tion spectroscopy. Although some at tempts have been made to use this technique in the field, good results re quire a laboratory analysis and the delay that that entails. Moreover, to avoid contamination, the technique re quires a relatively large sample of blood from which the lead can be ex tracted. Although lead poisoning has declined since a 1970 government restriction on lead content of paint, it is nonetheless still a serious problem. Small children can ingest paint chips and dust coming from the walls of old houses, for exam ple. City dust high in lead content as a result of auto exhaust is another poten tial source. The new test stems from work by Dr. Angelo A. Lamola and Dr. Tetsuc Yamane, chemists at Bell Labs. Lamo la began studying ^-carotene's effec tiveness in reducing sunlight sensitivi 18
C&EN Feb. 3, 1975
ty in porphyria patients. Porphyria is a pathological abnormality characterized by extreme sensitivity of the victim to light. Because of natural mechanisms that exist for inhibiting oxygen dam age, the work led to examination of the red blood cell membrane as a system. In porphyria, red cells photohemolize, making it possible to study the action of light in the chemistry involved. It had been known that with certain disorders—iron deficiency anemia and lead poisoning in addition to porphyr ia—there is an elevation of free erythro cyte protoporphyrin concentration. In deed, a number of groups had devel oped extraction procedures to study the protoporphyrin. The validity of a protoporphyrin ap proach to screening for lead poisoning had been demonstrated in a study by Dr. Sergio Piomelli of New York Uni versity Medical Center working in col laboration with the New York City De partment of Health. In fact, use of the approach recently has been approved by the U.S. Public Health Service's Center for Disease Control. However, the technique used in the study by Pi omelli employs an extraction procedure that must be carried out in a laborato ry. Lamola, working with Piomelli and with Dr. Maureen Poh of Columbia University's College of Physicians & Surgeons, began delving into a basic question: Since both lead poisoning and porphyria are characterized by ex cess protoporphyrin in the blood, why are lead poisoning victims not sensitive to light? Because of the expertise in fluDrop of blood on glass slide is all that's needed for Bell Labs1 new detector
orometry existing in Bell Labs' bio physics department, Lamola turned to that technique for an answer. A num ber of new findings resulted. Examining diluted whole blood, erythrocytes, and hemoglobin, Lamola and Yamane found that the substances from patients with anemia or lead poi soning exhibited fluorescence with maxima at 594 nm, but those from porphyria victims exhibited a maxi mum at 625 nm. In addition, the exci tation maximum of 397 nm for por phyria substances was different from the 424 nm for lead poisoning sub stances. These differences hadn't shown up on extracts from conventional acidic extraction methods. The fluorescence spectra of extracts were identical, re gardless of the source. What the experiments indicate, La mola says, is that most of the fluo rescent protoporphyrin in blood from patients with porphyria is different from that of those with lead poisoning. Various studies led to the conclusion that the fluorescent protoporphyrin of the lead poisoning type is probably not free but chelates a metal ion. Further studies pinned down zinc as the metal. Evidence gathered, Lamola says, points to zinc protoporphyrin as being bound in globin moieties, probably at heme binding sites in the hemoglobin. In porphyria, on the other hand, few vacant heme sites are available for binding of protoporphyrin as zinc pro toporphyrin. As a result, most of the protoporphyrin likely is bound as the free base at other sites. Zinc protoporphyrin occurs in lead poisoning and iron deficiency anemia, Lamola explains—in anemia, because of iron deficiency and in lead poisoning because of poisoning of the iron-inser tion enzyme by the lead. Zinc is one of the few metals that undergoes a nonen zyme chelation in aqueous solution at a high rate. Thus, it becomes incorpo rated in the molecule in preference to magnesium, which also exists in the cells. Bell Labs physicists Josef Eisinger and William E. Blumberg took the chemical findings and incorporated them into a practical testing fluo rometer. The unit uses only the single drop of blood on the glass slide. No volume measurement is needed since the sample is optically dense. As little as 5 X 10~12 gram of zinc protoporphy rin in the drop of blood can be detect ed. Lamola notes that public health per sonnel can learn to use the instrument with only a few minutes' study. With each test reading, the unit automati cally reads a blank and calibration standard. It provides a digital readout of protoporphyrin equivalence in mi crograms per 100 ml of blood. The reading is normalized automatically to take hematocrit differences into ac count. In using whole blood rather than ex-
tracts, and in measuring specifically zinc protoporphyrin, the Bell Labs test differs from the previous protoporphyrin approach. In giving an immediate reading, it enables public health personnel to take necessary action while a child being tested is still in hand. The delays inherent in laboratory analysis can make screening by that approach highly ineffective. For clinical verification of the technique, Lamola and Yamane collaborated with Dr. Morris Joselow of the New Jersey College of Medicine and Dentistry. They tested some 1000 blood specimens from children aged 1 to 5 and compared results of the fluorometer technique with those of conventional lead analysis. The correlation, Lamola says, was excellent. Bell Labs plans to make information about the technique and test equipment available to federal public health authorities. It also will make a number of test units for field evaluation. G
Drug board okays generic substitution In a turnabout move, the National Research Council's Drug Research Board says that there is "no inherent reason" for selecting an expensive brand-name drug product when a lower-cost generic equivalent will do just as well. The board urges that antisubstitution laws be amended to reflect this. Previously (early 1973), the Drug Research Board took the position that existing antisubstitution laws that prevent a pharmacist from substituting a generically equivalent drug for a brandname product were appropriate and should continue on the books. Only two states—Florida and Michigan—and the District of Columbia allow substitution by pharmacists. In reversing itself, the board engages in a little circular reasoning. It did not consider that the less expensive of two
drugs with the same chemical identity is necessarily the more desirable. But, in absence of information to the contrary, the group says, it's "unreasonable to assume that the less expensive is less desirable." The onus should now be on both the physician and the pharmacist, according to the board. For his part, a physician should be prepared to justify prescribing a brand-name product. The pharmacist, on the other hand, should be ready to defend the substitution of a less expensive drug for the one originally prescribed. Meanwhile, the Department of Health, Education & Welfare, which pays for drugs under medicare and medicaid, intends to work out a list of commonly prescribed drugs (C&EN, Nov. 11, 1974, page 8). HEW will use this to pay for drugs, but only for the lowest priced products widely available (except where physicians can demonstrate need for a more costly product). D
Technology
IITRI work focuses on chemistry of of smell smell Although odors are all-pervasive, smell remains one of the least quantified chemical phenomena. That situation is changing fast, however. As the citizenry becomes increasingly intolerant of the aroma from the local skunk works, and as vendors become ever more interested in using fragrances to persuade people to buy their products, there is a correspondingly greater impetus to bring a more systematic approach to the subject of smell. At IIT Research Institute's odor sciences center in Chicago, for example, the emphasis is on the multidisciplinary approach: melding the expertise of the analytical chemist with the psychophysical judgment of the smeller. Dr. Andrew Dravnieks, technical director of the center, points out that the IITRI investigations end at the nose. Ignored is the question of what is going on in the brain when a smell is perceived. However, he adds, many of the center's findings are helpful to electrophysiologists and others seeking answers to that question. A major part of the work at the odor sciences center consists of developing "chemical signatures" associated with odors. To do this, a sample of an odorous substance is passed through a gas chromatograph. The effluent is split. Part goes to a flame ionization detector (and associated recorder); part goes to a "sniffing port." As he watches the chromatograph printout, the analyst notes the peaks, sniffs, and marks down which of the peaks are associated with odors. Typically, Dravnieks says, only about 10 out of 50 peaks on a printout will be noted as having an odor. The human sense of smell can detect as little as 0.1 ppb in air of some com-
pounds. The gas chromatograph can't detect concentrations that low, so the sample must be enriched. Dravnieks developed a preconcentrator in which sample air is passed through a column containing a high-surface-area styrenedivinyl copolymer. Most organic compounds are adsorbed completely, but the hydrophobic organic polymer allows most of the moisture in the air to pass through. Heating the column causes desorption of the sample; about 90 to 95% can be transferred to the chromatograph. The chemical signatures are reliable enough to be used for predictive purposes. In air pollution control, for example, the technique can be used to measure the cost effectiveness of alternative means of odor control such as scrubbers, incinerators, adsorbers, and catalytic combustion devices. Although Dravnieks won't divulge details of his work for industrial clients, he notes that customers have included Tenderers, paper mills, pet food processors, and chemical plants. For government agencies, the center has worked on such problems as a bomb detection systembased on the vapors emitted by explosives—and on a project called "characterization of effluvia from cannabis." (Those clever marijuana-sniffing dogs may someday be replaced by machines.) For other clients, the center has done studies on human underarm, oral, and vaginal odors, and on the effectiveness of various deodorants. Dravnieks notes that there are four "sensory dimensions" to consider in measuring odors: detectability, intensity, character, and what he calls "the hedonic dimension"—that is, the pleasantness or unpleasantness of an
Sniffer checks one of three ports in attempt to detect odorous substance
odor. Detectability—the only dimension, so far, to be statutorily regulated— probably has received the most attention at IITRI and elsewhere. The technique of measurement is to present different dilutions of an odorous substance to a panel of sniffers, and to determine the concentration at which the sniffers aren't sure whether they smell anything or not. Thresholds vary with individuals, so the result must be treated statistically. Also, safeguards must be included to avoid bias. The present standardized detectability test, developed by the American Feb. 3, 1975 C&EN
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