E. Grunberg

Fluorescent labeling of proteins. A new methodology.

Abstract A new reagent, 2-methoxy-2,4-diphenyl-3(2 H )-furanone (MDPF) has been utilized for the fluorescent labeling of proteins. MDPF, which is nonfluorescent, reacts with primary amino groups to form fluorescent N -substituted 3,5-diphenyl-5-hydroxy-2-pyrrolin-4-ones. Antibodies labeled with MDPF afford intense immunofluorescent staining.

A Comparative Study of the Antitumor and Antiviral Activity of 1-β-D-Arabinofuranosyl-5-fluorocytosine (FCA) and 1-β-D-Arabinofuranosylcytosine (CA)

Summary FCA was similar or slightly superior in activity to CA with regard to antitumor effects when tested against the following experimental tumors: ascitic leukemia L-1210, sarcoma-180, Ehrlich solid carcinoma and mammary adenocarcinoma EO 771. FCA was appreciably more active on a mg/kg basis than CA with regard to its effect against the solid forms of leukemia L-1210 in both semi-isologous BDF1 and homologous albino mice, as well as against Walker carcinosarcoma 256. Both substances were without effect against the Flexner-Jobling carcinoma in rats. FCA and CA exerted similar degrees of antiviral activity against herpes simplex keratitis in the rabbit and vaccinia virus in rhesus monkey kidney cell cultures. Both substances were inactive in vivo and in vitro against the following RNA-containing viruses: Columbia SK, Coxsackie virus B1 (GP), and influenza A (PR8).

EXPERIMENTAL APPROACH TO TOPICAL ANTIBACTERIAL THERAPY

Research to find substances effective as topical antibacterial agents is not a new field of endeavor. Interest in this area has, moreover, increased in recent years since the bacterial strains most commonly causing primary and secondary superficial infections have shown a steady increase in resistance to modern-day chemotherapeutic The majority of laboratory techniques used for estimating the potency of antibacterial agents have been in vitro tests.s Although it is not our intention to belittle such tests, which in recent years have led to the discovery of clinically useful topical agents, the validity of in vitro tests for the chemotherapy of infectious diseases has always been questionable. When the search for chemical agents acting on pathogenic microorganisms began, investigators were confronted by the following interesting phenomena. (1) Compounds of high activity in vitro were completely inactive in vivo. Examples of this lack of correlation are the disappointing results that Robert Koch and Emil von Behring obtained when they tried to influence the diphtheria infection of guinea pigs with phenol or mercuric chloride, the best-known disinfectants of that time, and Koch’s unsuccessful attempts to use aurothiocyanate, a powerful in vitro agent, against tuberculosis in guinea pigs.6 (2) Compounds of high activity in vivo have little or no activity in vitro. Although there is a large number of compounds of different chemical composition that fall into this category, well-known examples of this are the arsonic acids and arsenobenzenes which are active in vitro only in their oxidized forms as arsenoso compounds. Among the antibacterial drugs that belong in this group are the sulfonamides, which exert their effect predominantly in vivo while the activity in vitro can be demonstrated only under special conditions and in media in which the presence of inhibitory substances is carefully avoided? An example that encompasses both of the above-mentioned phenomena is the observation by Morgenroth et a1.8 that high in vitro activity in a series of acridine derivatives was represented by little or no local activity in vivo, and vice versa. It is apparent, of course, that in many instances, particularly in the case of modern antibiotics such as penicillin and streptomycin, activity in vitro can be used as a lead for activity in vivo. However, no concrete evidence seems available that the activities in vitro and in vivo are due to the same mechanism. This fact is not surprising because the biological conditions that prevail in the infected tissues, the sensitive equilibrium of the natural defense mechanism of the host, and the invasiveness of the organism are much more complicated than the conditions that exist in an in vitro test even though it may not be true, necessarily, that the latter test is based on a biologically simple system. Therefore, the problem for the experimental approach to topical antibacterial therapy is to find a satisfactory test by which the reaction of the infecting organism to a chemical agent can be studied in the presence of tissues. I t must be a technique adapted to the facilities of the average laboratory and sufficiently

α-Chloromethyl-2-methyl-5-nitro-1-imidazoleethanol (Ro 7-0207), a substance exhibiting antiparasitic activity against amebae, trichomonads and pinworms.

Summary α-Chloromethyl-2-methyl-5-nitro-1-imidazoleethanol was found to exert marked chemotherapeutic effects against experimentally induced infections of rodents with Endamoeba histolytica, Trichomonas vaginalis, Trichomonas foetus, and against a natural pinworm infection of mice produced by Syphacia obvelata. The substance was also highly active in vitro against anaerobic bacteria but not against facultative or aerobic microorganisms. Except for a slight effect noted in the case of the sarcoma-180 tumor, this 5-nitroimidazole derivative was inactive in all other experimental models tested in vivo including bacteria, fungi, and viruses.

EXPERIMENTAL METHODOLOGY AND THE SEARCH FOR EFFECTIVE ANTIVIRAL AGENTS

Chemotherapeutic research i n the f i e l d of virology is not a new endeavor. There is no doubt that the i n t e r e s t , practical as w e l l a s t heo re t i ca l , i n successful ly combatting v i r u s diseases of animals and plants , has increased considerably s ince the l a s t conference on a n t i v i r a l agents. Consequently, i n t e r e s t i n experimental t e s t i n g methods which allow f o r the se l ec t ion of ac t ive compounds has a l s o increased.