HISTOCHEMICAL DEMONSTRATION OF MUSCLE LIPASE

A method which is an advance over the existing methods for the histochemical demonstration of lipase activity in muscle, using "Tween 85' as substrate and alizarin red S as stain for the calcium soap formed, is described. Lipase has been localized in the mitochondria of the fish trunk and pigeon breast muscles.

FURTHER STUDIES ON A LABILE IMMUNOGENIC PARTICULATE SUBSTANCE ISOLATED FROM MYCOBACTERIUM TUBERCULOSIS

Youmans, Anne S. (Northwestern University Medical School, Chicago, Ill.), and Guy P. Youmans. Further studies on a labile immunogenic particulate substance isolated from Mycobacterium tuberculosis. J. Bacteriol. 87:278-285. 1964.-A particulate fraction which was highly immunogenic for mice was collected by ultracentrifugation from mycobacteria disrupted in 0.25 m sucrose buffer. The active immunogenic material was present in the gelatinous pellet obtained after centrifugation at 40,000 rev/min (144,000 x g) for 3 hr. This active material could be prepared free from whole cells and cell walls. This was done either by several centrifugations at lower speeds, or by filtering the supernatant fluid from the 10,000 rev/min centrifugation through a Millipore filter (porosity 0.5 mu). No microorganisms were found on slides or in cultures made from these filtrates. The immunogenic moiety in the particulate fraction was found to be very labile. Temperatures higher than 0 to 4 C inactivated the immunogenic activity. There was an irreversible linear decrease in activity as the temperature increased. If fractions were frozen or lyophilized, the activity remained as high as the original material for 4 weeks, and then rapidly decreased. The immunogenic material also was very sensitive to the hydrogen-ion concentration; the optimal activity was found at pH 6.8 to 7.0. The activity decreased rapidly at more acid or alkaline pH values. Also, particulate fraction prepared in sucrose buffer at pH 7.3 and 7.6 was much less active than that prepared in sucrose buffer at pH 7.0. Immunogenic activity was decreased if the particulate fraction was dialyzed overnight against 0.01 m phosphate buffer or distilled water at 4 C. The detergent sodium lauryl sulfate inactivated immunogenic activity. Moreover, the use of a Waring Blendor to blend the ruptured cell mass before centrifugation decreased the activity. Finally, a markedly lower activity resulted if both the 20,000 and 40,000 rev/min centrifugations were done the day after the rupture of the cells. Some refinements in technique which are used now in the preparation of the particulate fraction are detailed.

DEOXYRIBONUCLEIC ACID BASE COMPOSITION OF SOME MEMBERS OF THE SUBGENERA BETABACTERIUM AND STREPTOBACTERIUM

The base composition of deoxyribonucleic acid (DNA) prepared from four Betabacterium strains and four Streptobacterium strains was determined. Per cent GC values (guanine + cytosine/total bases) of the DNA were evaluated from the "melting-temperatures" (Tm) of the nucleic acids. For the Betabacterium strains, these values ranged from 44 to 51.5% GC, and those for the Streptobacterium strains ranged from 43 to 47.5% GC. The taxonomic division into these two subgenera is not, therefore, supported by these findings.

GUANINE-DEAMINASE ACTIVITY IN RAT BRAIN AND LIVER

1. Guanine deaminase in rat brain and liver was distributed among all the subcellular fractions: nuclei, ;heavy' mitochondria, ;light' mitochondria, microsomes and the supernatant fluid. The greater part of the activity passed into the soluble fraction. Among the particulate components, the ;light' mitochondria constituted the richest fraction. 2. The sum of the enzymic activities of the component fractions obtained on differential centrifugation was considerably greater than the activity of guanine deaminase in the whole homogenate. 3. The ;heavy'-mitochondrial fraction had a powerful inhibitory effect on the guanine-deaminase activity of the supernatant fraction. 4. All the sedimented fractions, except the microsomes, gave rise to higher guanine-deaminase activity on treatment with Triton X-100. 5. The inhibitory capacity of the ;heavy' mitochondria increased on treatment with Triton X-100; the detergent-treated nuclear fraction also brought about inhibition of the 5000g supernatant. 6. Guanine-deaminase inhibitor from the ;heavy' mitochondria was solubilized by high-speed grinding of the particles, followed by treatment with Triton X-100. The inhibitor appeared to be protein in nature, since it was precipitated by trichloroacetic acid and by half-saturation with ammonium sulphate, and was non-diffusible. It was inactivated by heating at 50 degrees for 5min. 7. It is possible that the guanine deaminase associated with particles differs from the soluble enzyme in its response to inhibitor.

A RESPIROMETER TECHNIQUE FOR ESTIMATING GERMICIDAL ACTIVITY ON SKIN

1. A technique for measuring the antibacterial activity of germicides on pig skin in micro-respirometers has been described.

2. Using this technique the activity of the following germicides has been estimated: 2,2-dihydroxy, 3,5,6,3′,5′,6′-hexachlorodiphenylmethane, 3,4,4′-trichlorocarbanilide, 3,5,4′tribromosalicylanilide, 2,2′-thiobis (4,6-dichlorophenol), Irgasan CF3*, 3,5,3′,4′-tetrachlorosalicylanilide.

3. The results obtained have been discussed in relation to hand-washing test results (Hurstet al.1960).

CONVULSIVE SYNDROME IN RABBITS INJECTED WITH FAT EMULSION AND HEPARIN

Functionally hepatectomized rabbits showed convulsions and coma within 2 hours after the intravenous injection of fat emulsion and heparin. Intravenous injection of the detergent triton prevented this syndrome, if given before the fat emulsion and heparin, and reversed it if given subsequently. Extremely high plasma non-esterified fatty acid levels were noted in rabbits showing the convulsive syndrome, but not in animals that received the detergent. The mechanism of the convulsions probably includes the toxicity of high amounts of non-esterified fatty acids.