After incubation with thymosin, a thymic hormone, normal bone marrow rosette-forming cells acquire T-cell characteristics, including increased sensitivity to azathioprine, anti-lymphocyte serum, and anti-theta serum. This activity of thymosin provides a new sensitive and reproducible bioassay for thymosin, and is well correlated with an in vivo graft-versus-host assay. In addition, incubation of spleen cells from adult thymectomized mice with thymosin in vitro restores to normal their diminished sensitivity to azathioprine and anti-lymphocte serum.

Animals↗

PubMed1971

Evidence for induction by cortisol in vitro of a protein inhibitor of transport and phosphorylation processes in rat thymocytes.

Studies of intact rat thymocytes incubated in vitro with cortisol, actinomycin D, puromycin, and cycloheximide indicate that distinct inhibitory effects of cortisol on transport and phosphorylation are due to an action on mRNA synthesis with consequent induction of synthesis of protein(s) with inhibitory influence. Incubation of thymocytes with cortisol results in inhibition of the rate of labeled orthophosphate incorporation into ATP and the entry of rubidium ion and hexoses into the cells. Continuing protein synthesis is required for the progressive and persistent manifestation of the inhibitory effects of the steroid. RNA synthesis is also required during the initial phase of incubation of cells with cortisol, but significant inhibitory effects of cortisol, once initiated, are evident for at least 60-120 min after addition of actinomycin D. In contrast, addition of cycloheximide some time after cortisol results in prevention or reversal of the effects of the steroid. In the absence of cortisol, the antibiotics exert relatively little effect on orthophosphate incorporation and on the transport processes studied. It is suggested that the sequence of events leading to dissolution of thymocytes exposed to cortisol is initiated by the synthesis of mRNA coding for inhibitory protein(s) with more rapid turnover rates than that of the mRNA, and that these events are modulated by the relative sensitivity of different cellular processes to the protein inhibitor(s).

Adenosine Triphosphate↗

PubMed1971

Quantitative nasal culture: a tool in antibiotic research.

The use of the quantitative nasal culture was investigated as a means of evaluation of new antimicrobial drugs in man. Cyclacillin was somewhat more active in vitro than penicillin G against penicillin G-resistant organisms. Cyclacillin was highly effective in suppressing staphylococci susceptible to penicillin G in nasal carriers but did not suppress staphylococci resistant to penicillin G. Although in previous studies by others cyclacillin was effective in treating mice infected with penicillin G-resistant staphylococci, in the present studies cyclacillin was not effective in suppressing nasal penicillin G-resistant staphylococci in man at doses which markedly suppressed penicillin G-sensitive organisms.

Administration, Oral↗

PubMed1971

Inactivated eastern equine encephalomyelitis vaccines prepared in monolayer and concentrated suspension chick embryo cultures.

Eastern equine encephalomyelitis vaccines were prepared with virus propagated in stationary monolayer cultures and in concentrated suspension cultures of primary chick embryo cells. Virus pools for vaccine preparation were inactivated by three different methods: 0.05% formalin, 41 C heat, and 0.16% beta-propiolactone. Heat-and beta-propiolactone-inactivated vaccines maintained high hemagglutinating titers in the fluid state for at least 10 months, whereas formalin-inactivated vaccines lost their hemagglutinating activity within a few hours after treatment. The hemagglutinin of beta-propiolactone-inactivated virus particles was more dense than the hemagglutinin of the parent virus particles, as determined by sucrose density gradient centrifugation. The increase in density may be due to the degradation or removal of the lipid from the virus envelope. When administered to guinea pigs, all three vaccines stimulated hemagglutination-inhibiting, complement-fixing, and neutralizing antibodies and afforded protection against a live virus challenge. Test results showed that vaccines prepared with virus propagated in concentrated suspension cultures were more immunogenic and stimulated greater serologic responses in guinea pigs than vaccines derived from monolayer-propagated virus. The beta-propiolactone-inactivated vaccine was most protective, the heat-inactivated (41 C) vaccine next, and the formalin-inactivated vaccine least potent.

Animals↗

PubMed1971

Histamine release in the dog after leukocyte lysate injection.

Mixed leukocyte suspensions, containing 10(6) leukocytes per ml, were prepared from dog peripheral blood by dextran sedimentation. Lysates of these suspensions, prepared by sonification, were administered intravenously to the autologous dogs. The plasma histamine levels were increased to an average value 320% above the control values (P < 0.001). The individual elements in the mixed leukocyte suspensions were separated by sucrose gradient and glass bead column fractionation procedures, and purified suspensions of platelets (no other formed elements present), lymphocytes (95 to 100%), and granulocytes (90 to 98%) were obtained. Lysates of these suspensions all had significant histamine-releasing activity when administered intravenously to dogs. Although leukocytes and platelets from other species are known to harbor mediators of histamine release, this study provides the first demonstration of the histamine-releasing activity of dog leukocytes and platelets. Many of the studies of leukocyte and platelet histamine-releasing factors have employed in vitro systems leaving the in vivo role of these factors in doubt. The present studies provide evidence that leukocyte and platelet histamine-releasing factors have in vivo activity.

Animals↗

PubMed1971

Mediators of histamine release from human platelets, lymphocytes, and granulocytes.

Lysates of mixed human leukocyte suspensions released histamine from intact human leukocytes in vitro. Microgram quantities of leukocyte lysate protein released up to 90% of the total available histamine. The mixed leukocyte lysates were separated by differential centrifugation into nuclear (800 g pellet), lysosomal (25,000 g pellet), and postlysosomal supernatant (25,000 g supernatant) fractions. The degree of separation of the lysosomal from the other two fractions was assessed by measuring the relative activities of four lysosomal enzymes. The average distribution of enzyme activity was 11 +/-2% (mean +/-1 SD), 72 +/-10%, and 17 +/-8% for the nuclear, lysosomal, and supernatant fractions respectively. The histamine-releasing activity was equally distributed between the lysosomal and supernatant fractions, each of which had 5-fold greater activity than the nuclear fraction. Purified suspensions of platelets, lymphocytes, and granulocytes were prepared, and the lysates of these suspensions all had histamine-releasing activity. Centrifugation at 100,000 g for 18 hr sedimented the histamine-releasing activity from all three types of lysate. After 20% ethanol fractionation for the preparation of cationic protein, only the activity from the platelet lysates was found in the 20% ethanol insoluble fraction. These mediators of histamine release from human platelets, lymphocytes, and granulocytes may play a role in the development of the vasodilation and increased vascular permeability which characterize the acute inflammatory response.

Acid Phosphatase↗

PubMed1971