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The possible risks of infection associated with the practice of licking envelopes, stamps and labels were investigated. Although pathogenic bacteria and viruses were not isolated from sample envelopes obtained from various sources, the gums used in manufacture were found to exert a protective effect against death from desiccation on the bacteria and viruses which had been introduced into them.Staph. aureus and Salm. paratyphi Bremained viable for several months in dried films of two out of four gums tested. An echovirus could be recovered from similar films for up to 30 days, and an adenovirus for up to 10 days.Bacterial multiplication occurred in the gum used for the manufacture of postage stamps. The comparison is drawn between the possible consequences of minimal contamination of this gum and of cans of corned beef in the light of recent studies.

BOSTON having often been accused of robbing New York City of its medical talent, it is good to note that municipal health services are in such capable hands as those of Drs. Bellin and Kavaler and Mr. Alexander. Considered as a whole, the three papers are a tribute to their dedication and resourcefulness. At the same time, the three papers constitute a forceful indictment of Medicaid as a mechanism to solve the problem of delivering health services to indigent and medically indigent persons. It is well to recall that New York City has had almost 300 years of providing public medical care to the poor; for the last 130 years, the city has made continuous payment for services rendered to city "charges" by voluntary hospitals as well. Medicaid in New York City is not, then, a new development. Mr. Alexander's excellent paper contains a few minor errors of fact. For example, he states that at the inception of the Medicaid program the New York City Health Department had no structure for standard setting or evaluation, and that these were under welfare jurisdiction. The Health Department's Bureau of Handicapped Children has been engaged in standard setting for many years. Moreover, the Inter-Departmental Health Council has developed a mechanism for the establishment of standards of care for all persons receiving services at city expense in such fields as: the care of amputees, and cardiac, thoracic, and neurological surgery. Hospitals, unable or unwilling to comply with the standards, were not reimbursed for care in these specialty areas. In addition, the Medical Welfare Administrator established general standards for hospital outpatient departments and authorized higher per visit payments for those hospitals that met them. In respect to evaluation, the Department of Health established a unit under Dr. Paul Densen which carried out evaluation studies in the Departments of Health, Hospitals, and Welfare. Mr. Alexander states that both public and professionals unfortunately thought of Medicaid as welfare. However, the public and professionals are right. Title XIX of P.L. 89-97 provides for the consolidation and expansion of welfare medical care by "making medical assistance available to all individuals receiving aid or assistance under . . . Titles I, IV, X, XIV, and XVI," the public assistance title of the Social Security Act (Section 1902 (a) (10) Title XIX, P.L. 89-97). Moreover, Section 1902 (a) (5) requires that the determination of eligibility for medical assistance be made by the state or local public welfare agency. Medicaid is medical welfare. Mr. Alexander's generally unfavorable comparisons of Welfare Department Administration to Health Department Administration fail to mention the less than inspired direction given to Medicaid by the New York State Department of Health. Dr. Bellin's paper contains an excel

are essential, with. the former more related to specificity and the latter to stability. The interaction of nucleotides and nucleoside triphosphates with r(C)0 and r(U)n was reported in the second and third papers of this series." 4 This same system has also been studied by laboratories at the National Institutes of Health, with different emphasis.5-7 In. the present paper, the cause of mispairing anid intercalation in. niucleic acid interaction. has been investigated. M11aterials.---Solutions of r(U)n (Miles Laboratories, Elkhart, Indiana) at a concentration of 10 mag/ml were dialyzed against 0.01 ll Tris buffer, pH 7.0, for 1.2 hr in a cold room before use. The exaet concentration of uridine units in solution was deternmined fromn. optical density mneasurement at 259 my by using the molar extincti-on coefficient of 9.2 X 10'. Adenosine, guanosine, and cytidine were A grade preparations from Sigma Chemical Company, St. Louis, Missouri. and were used. without further purification. Caffine was purchased from Eastman Organic Chemicals, Rochester, New York, and was dried at 120? for 24 hr 'before use. C '4-adenosine, H3-caffeine, and HI-BP were obtained from Nuclear-Chicago Corporation, Des Plaines, Illinois, and H3-cytidine and H3-guanosine were o'btained from Schwarz BioResearch, Orangeburg, New York. Before being used, HI-guanosine was checked by paper chromatography for possible contamination of adenosine. Methods.--Equilibrium dialysis: The experimental procedure of this technique was described in our previous paper.' Solutions of r(U)n (1.5 X 10-' 11f) were dialyzed against an invariant concentration of H'-guanosine (1.17 X 10 -111,I; 1.1 X 10 pl/m mI), HI-caffeine (1.2 X 10 -' 1I; 3.52 X 101 cpm /mMV), or HI-cytidine (1.13 X 1.0--l ll1; I X 107 cpm/mM) together with varying amounts of C'4-adenosine (cone. rangedl from, 1.10-' lIf to 2.5 X 1_0-2 1il; 8.7 X 103 cpm/mM) in 0.4 211 NaCl, 0.01. i Tris buffer, pH 7.0, at 50 for 1.0 days. At the end of the equilibrium dialysis period, the distribution of nucleoside inside and outside the dialysis tubing was assayed by a double-counting procedure in a Nuclear-Chicago ambient temperature liquid-scintillation counter model no. 722. The concentration of the nucleosides outside the dialysis tubing was considered to be the concentration of the free nucleosides. The difference in radioactivity between the inside and the outside of the dialysis tubing divided by the total radioactivity (summation of radioactivity from both inside and outside the tubing) gave the percenttage

SUMMARYIn view of recent food-borne outbreaks of salmonella infection in which cooked-meat slicing machines have been implicated in the spread of organisms from contaminated meat products to other meats, experiments have been made to provide laboratory evidence that a contaminated slicing machine will easily cross-contaminate other products passing through it. Chopped pork inoculated with coagulase-positive staphylococci was cut on a slicing machine; staphylococci were isolated up to the 41st slice of various cooked meats cut on the same machine. The experiments were repeated withSalmonella oranienburg; this serotype was isolated up to the 31st slice of various cooked meats cut on the same machine, and from pieces of damp cloth wiped over the gravity feed, knife centre disk and cutting blade.The importance of efficient and regular cleaning of slicing machines with hot water containing detergent/disinfectant, or detergent followed by disinfectant, applied with clean cloths or preferably disposable paper, is stressed.I thank Dr Betty C. Hobbs, Director of the Food Hygiene Laboratory, and Dr J. C. Kelsey, Administrative Director of the Central Public Health Laboratory, for their help throughout the work and the compilation of the paper.

Although the amino acid sequences of two subtilisins' do not resemble those of the pancreatic proteinases chymotrypsin2 and trypsin,3' 4 the two groups of enzymes are similar in that they are both inhibited by reaction with diisopropylfluorophosphate at a single specific serine residue.5 Further, a specific histidine residue has been identified in the active sites of trypsin and chymotrypsin by reaction with the specific alkylating agents TLCKI6 I and TPCK.8 Although these reagents do not inhibit the subtilisins,9 kinetic data do suggest involvement of an un-ionized histidine residue in the active sites of these enzymes.10 Shaw and Ruscicall have found that the increased reactivity of the bromomethyl ketone of carbobenzoxy-L-phenylalanine (ZPBK) is sufficient to inhibit the subtilisins. There is close agreement between the loss of activity, incorporation of tritium from 3H-ZPBK, and loss of histidine with subtilisin BPN'. The reagent is stereospecific with only the L-form being reactive with the enzyme. That the reactive histidine must be involved in the enzymic activity is demonstrated by the finding that subtilisin BPN' treated with ZPBK no longer reacts with diisopropylfluorophosphate. After performic acid oxidation, 3-carboxymethylhistidine was identified. We wish to report on the identification of the active-site histidine residue in the subtilisins with the use of ZPBK. Materials and Methods.-Chemicals: Subtilisin Carlsberg was obtained from Novo Pharmaceutical Company, Copenhagen, Denmark (batch 60420), and subtilisin BPN' (as Nagarse) from Biddle Sawyer Corp., New York. ZPBK and 3H-ZPBK were synthesized by the method of Shaw and Ruscica."1 Radioactivity measurements: Radioactivity of the tritium-labeled protein or peptides was measured in a Packard (model 3003) liquid scintillation spectrometer. Liquid samples of 20-100 ,ud (usually 50 ,ul) were counted in 10.0 ml of Bray's solution,'2 with corrections for background but not for differences in efficiencies with the different solvents or different sized aliquots. To locate radioactive peptides after preparative chromatography or electrophoresis, guide strips that had been sprayed with ninhydrin or the Pauly reagent'3 were cut into small pieces and counted as described above in 10.0 ml of a scintillation solvent that contained 6 gm of PPO and 0.3 gm of dimethyl POPOP in 1 liter of toluene. In later stages of the work, a Beckman solubilizer BBS-3 was added to the toluene scintillation solvent'4 to improve the counting efficiency. Peptide separation: Peptides were separated either by gel filtration on Sephadex G-75 or G-25 in formic acid-propanol-water (30:20:50 by volume) and detected with ninhydrin after alkaline hydrolysis.'5 Paper chromatography in n-butanol-acetic acid-water (200:30:75 by volume) (BAW) and paper electrophoresis at pH 1.9 were used preparatively. Peptides were eluted from paper with 35% acetic acid and, unless otherwise specified, were dried on a rotary evaporator. Peptide maps were run with electrophoresis at pH 1.9 and chromatography in BAW. Amino acid analysis: Samples were hydrolyzed at 1100 for 24 hr in evacuated glass tubes with 6 N HCI containing a drop of 5% phenol in water. Analyses were performed with the Spinco automatic amino acid analyzer model 120 B with an accelerated system.'6 17 Results.-Reaction of 3H-ZPBK wvith subtilisin Carlsberg: M\1ost of the work

Since the occurrence of cytokinin' activity has been limited mainly to 6-substituted purine derivatives,2 -4 it was of special interest to determine the origin of the kinetin-like growth-promoting activity of the 1-substituted adenines, 1(-y, y-dimethylallyl)adenine (I, tautomeric forms shown), and 1-benzyladenine, which were made5 and tested6 in these laboratories. While consideration has been given to the possibility that the 1-substituted adenines might be active as such, our interpretation of the results previously reported has been that the development of activity was the consequence of chemical change to the N6-isomeric or other active N6-substituted compounds."t 6 Accordingly, our experiments have been directed toward determining the conditions under which 1to N6-isomer conversion will occur. First, it was necessary to ascertain that we could obtain pure 1-(Q,yy-dimethylallyl)adenine (I), free from any of the isomeric 6-(y,-y-dimethylallylamino)purine ("N6-2-isopentenyladenine") (II), the highly active cytokinin4 7-9 which was originally obtained synthetically5"0 and has been found more recently to be naturally occurring."1-'4 The 1-(y,y-dimethylallyl)adenine was prepared by the procedure previously reported:' alkylation of adenosine with -y,Y-dimethylallyl bromide in dimethylformamide at room temperature followed sequentially by hydrochloric acid hydrolysis in ethanol, cautious neutralization in ethanol with potassium carbonate to pH 6.8, and isolation of the initial product by an evaporative procedure during which the solution was kept below 35?. The product was recrystallized 10-12 times from ethanol. Cellulose column chromatography of both the crystals and the mother liquor from the last recrystallizations did not show the presence of any impurity. Thus, we could conclude that the level of impurity was less than 0.1 per cent since the chromatography of an artificially prepared mixture of 500 mg of 1-(y,y-dimethylallyl)adenine and 0.5 mg of 6-(y,y-dimethylallylamino)purine permitted easy detection of the latter by ultraviolet spectra of the eluted fractions. The pure compound I was characterized by the following properties: XEtOH9 mp 237-238?,5 Rf 0.55 (butanol, water, acetic acid -'75:20:5); X Hax 273 m,u (e 12,300), Xmin 246 (3900); Xmax (acidic) 260 (13,400), Xmin 233 (3,900); Xmax (basic) 274 (15,200), 268 (15,000, dual peak), 300 (sh) (4,100), Xmin 242 (4,500). Next, it was necessary to minimize chemical change of the 1-(y,'y-dimethylallyl)adenine in the test for cytokinin activity. The procedures and media employed were essentially those of Murashige and Skoog'5 using tobacco callus tissue (Nicotiniana tabacum var. Wis. #38) as described earlier.6 Solutions of pure 1(-,yy-dimethylallyl)adenine were sterilized by filtration and added to the medium

The mechanisms responsible for the genetic control of the variability and the specificity of immunoglobulins are not understood. The problem has not been clarified by the recent finding that this variability is restricted to one portion of the molecule and within that "variable portion" is restricted to certain sites (see review in ref. 1). It appeared important to attempt the synthesis of an immunoglobulin of recognized specificity in a cell-free system under conditions where the various factors involved in that synthesis could be modified independently. In such a cell-free system the synthesis of entire immunoglobulin chains, from the Nto the C-terminal amino acid, is expected to be a rare event. The method chosen for the analysis of the product should therefore not rely on finished polypeptide chains only, since these chains will be labeled mainly, if not exclusively, in their C-terminal (or "constant") part. The N-terminal (or "variable") portion of immunoglobulins synthesized in the cell-free state will mainly appear as unfinished chains which must therefore be included in the analysis of the cell-free product. Furthermore, immunological methods of detection, except those based on the principle of immunoabsorption, give unprecise results when applied to crude tissues extracts. For these reasons, we have chosen to identify the product synthesized by the cell-free synthesis by a chemical analysis of its tryptic peptides. Several reports of cell-free incorporation of amino acids into proteins by spleen or lymph node systems have been published.2-5 Because of the known heterogeneity of the immunoglobulins produced by these tissues, the specificity of the cell-free product made in these systems cannot be characterized chemically. This report describes a cell-free system obtained from plasmocytoma tumors of mice. It is capable of active protein synthesis: when a plasmocytoma producing a given immunoglobulin molecule is used as source of cell extracts, it can be shown that peptides identical to those of that particular immunoglobulin are synthesized in the cell-free system. Materials and Methods.-Plasmocytomatumors IV and 41, both L-chain producers and both growing on Balb/c mice, were obtained from Dr. G. Lespinat, Villejuif, France, and Dr. M. Potter, Bethesda, U.S.A., respectively. Tumor 5563, an IgG producer growing on C3H mice, was obtained from Dr. J. L. Fahey, Bethesda, U.S.A. Freshly excised tissues were homogenized at 0-2?C in 4 vol of medium A (0.05 M Tris pH 7.5; 0.025 M KC1; 0.005 M MgCl2; 0.006 M ,-mercaptoethanol; 4 jg/ml polyvinyl-sulphate) containing 0.88 M sucrose, first with 5 strokes in a loosely fitted Potter homogenizer, and then with 3 strokes in a Dounce glass homogenizer. After a first centrifugation at 20,000 X g for 20 min, the supernatant was spun for 60 min at 105,000 X g (bottom of the tube). The pellet ("microsome") was suspended gently in medium A containing 0.35 M sucrose. The supernatant was diluted 1/1 with medium A without sucrose and spun for 90 min at 105,000 X g (middle of tube). A high-speed supernatant and a "ribosomal" pellet were obtained.