Some mathematical aspects of chemotherapy—II: The distribution of a drug in the body

In a previous paper (Bellman, Jacquez, and Kalaba,Bull. Math. Biophysics,22: 181–198, 1960) a model of the processes occurring in the exchange of a drug between capillary plasma, extracellular space and intracellular space was developed. This included the possibility of a reaction between the drug and a component of the intracellular space. The equations developed thus describe the events within a capillary bed. In the present paper, a simplified model of the body is set up. Each organ is treated as a single capillary bed and is linked to other organs via the circulation, in the parallel and/or series arrangements found in the body. Mixing in the circulation is included at the simplest possible level. The concentration of drug entering any one capillary bed is determined by the concentrations leaving all other capillary beds, the time lags, and mixing involved in the circulation. The equations describing these processes in conjunction with the equations of the processes occurring within each capillary bed lead to a large set of differential-difference equations.     

COMPARISON OF DAYLENGTH AND TEMPERATURE RESPONSES IN NICOTIANA AND ITS TAXONOMIC SECTIONS

Steinberg , Robert A. (U.S.D.A., Beltsville, Md.) Comparison of daylength and temperature responses in Nicotiana and its taxonomic sections. Amer. Jour. Bot. 46(4): 261–268. Illus. 1959.—Fifty-seven of the sixty species of Nicotiana were grown in the greenhouse under long- and short-day regimes. Supplemental tungsten light of about 30 ft.-c. (bench) was used to extend natural illumination to 16 hr. daily. Short-day controls received natural illumination for 9.5–12 hr. daily from about September to March. Two temperature levels were also employed—one with temperature held uniformly at about 25°C. and the other with a day temperature of about 20°C. and a night temperature of about 10°C. Daylength behavior of the species ranged from long-day to day-neutral to short-day. All species were brought into flower and all, except N. acaulis and N. ameghinoi, formed viable seed in at least 1 of the 4 environments. A modified classification of photoperiodic flowering responses based on rapidity and not ability to flower was adopted to permit quantitative comparison of species responses to both daylength and temperature. Very few species flowered equally rapidly (day-neutral) in both the 10- and 16-hr. day-lengths. Temperature level caused modifications in response from long-day to day-neutral and vice versa, and from short-day to day-neutral and vice versa. Data for N. glauca and some other species would indicate that a greater spread between temperature levels could possibly lead to opposite classifications at upper and lower temperatures. Excellent agreement was found between daylength responses of the species and the 14 taxonomic sections of Goodspeed for the genus Nicotiana. Only 2 of the sections (Paniculatae and Undulatae) were heterogeneous in that both included short- and long-day species in the same section. The native habitat of all short-day species was South America. Certain of the species gave a compensatory response to variations in light duration and low temperature similar to that given by sugarbeets and other biennials. This phenomenon may therefore be of general occurrence. Use of a quantitative expression for photoperiodic flowering responses is proposed to avoid ambiguity. It is the quotient of days from sowing to first blossom on short-days divided by that on long-days. The value 0.6₂₀°C. (9–12) would read short-day at 20°C. with 9–12 hr. daylengths. Close agreement was found in daylength flowering ratios in successive tests in the greenhouse. The ratios alter under cold treatment with species susceptible to low-temperature stimulation or inhibition of blossoming.     

ORBITAL AND PERIORBITAL TUMORS—Indications for Exenteration

The anatomical location of the orbit, its relationship to surrounding structures and the vital concern to preserve sight, create special problems in the treatment of orbital and periorbital tumors.Specific diagnosis of orbital tumors can be made only by biopsy. Frozen section technique is very helpful when available. Roentgenographic visualization of the orbital bones is a valuable adjunctive method of determining the extent and type of tumor.The three most common forms of lacrymal gland tumors are benign “mixed tumors,” adenoid cystic carcinomas (cylindromas), and adenocarcinomas.A method of therapy for the treatment of orbital and periorbital tumors is described and the indications for exenteration are discussed.     

Clostridium perfringens in Meat and Meat Products

A total of 262 specimens of meat and meat dishes were examined for the presence of Clostridium perfringens. Of this total, 161 were raw, unprocessed beef, veal, lamb, pork, or chicken; 101 were processed meats and meat dishes. C. perfringens was isolated from 113 (43.1%) of these specimens. The highest percentage of contamination (82%) was found in veal cuts, and the lowest (4.7%) in sliced sandwich meats and spreads. Only 2 of the 113 isolates were shown to produce heat-resistant spores, which indicates a very low incidence (0.8%) of contamination. These findings indicate that outbreaks of C. perfringens food-borne disease in the Cincinnati area are caused principally by the contamination of the food with vegetative cells or spores of the organism after cooking. Studies of the effects of various holding temperatures on the growth of C. perfringens indicated that, in the range of 5 to 15 C, no multiplication would occur, but that viable cells would still be present at the end of a 5-day holding period. Extremely rapid growth occurred at temperatures around 45 C, and complete inhibition of growth was accomplished between 49 and 52 C.