Showing papers on "In vivo published in 1979"

Origin, Kinetics, and characteristics of pulmonary macrophages in the normal steady state.

Abstract: Pulmonary macrophages of mice in the steady state were isolated by lavage with PBS containing EDTA and subsequent enzymatic digestion of tissue with pronase and DNA-ase. By this method, the total pulmonary macrophage population was obtained in two cell suspensions, one with a pure population of pulmonary alveolar macrophages (PAM) and the other with a mixed population of pulmonary alveolar and pulmonary tissue macrophages (PTM). The morphological, cytochemical, and functional characteristics of both PAM and PTM were like those of mature tissue macrophages except for the presence of C3 receptors. These receptors were almost absent on PAM and present on a larger number of cells in the mixed population of PAM and PTM. The total pulmonary macrophage population of mice in the steady state is approximately equal to 2 x 10(6), of which about 93% are PAM and about 7% are PTM. In labeling experiments with 3H-thymidine, the low in vitro labeling indices (less than 3%) for both PAM and the mixture of PAM and PTM, showed that both are essentially nondividing cells. In vivo labeling studies showed an increase in the number of labeled macrophages that can only be attributed to labeled monocytes migrating into the lungs. Additional evidence was provided by a decrease in the labeling indices of pulmonary macrophages when mice were treated with hydrocortisone acetate, which causes a severe monocytopenia, thus preventing monocyte influx into the lungs. Confirmation of the bone marrow origin was obtained in mice labeled after x-irradiation with partial bone marrow shielding: labeled pulmonary macrophages were found in the exposed lungs. In all experiments, the labeling indices were identical in the two macrophage populations isolated. These results show that the influx of monocytes is the source of cell renewal for the pulmonary macrophages. No indications for an interstitial division or maturation compartment in the lung were found. Quantitation of the efflux of labeled monocytes from the blood, and the number of labeled pulmonary macrophages, showed that in the steady state about 15% of the monocytes leaving the circulation become pulmonary macrophages and that the turnover time of pulmonary macrophages is approximately equal to 27 d.

Activation of macrophages in vivo and in vitro. Correlation between hydrogen peroxide release and killing of Trypanosoma cruzi.

Abstract: As reported previously, mouse peritoneal macrophages could be activated to kill intracellular trypomastigotes of Trypanosoma cruzi, the agent of Chagas' disease, in either of two ways: by immunizing and boosting the mice (3), or by culturing resident or inflammatory macrophages in spleen cell factor(s) (SCF) in vitro (2). Macrophages activated in vivo became less trypanocidal with time in culture, and cells activated in vitro lost trypanocidal capacity when CSF was removed (2). In the present study, the ability of macrophages to release H2O2 in response to phorbol myristate acetate (PMA) could be induced in vivo and in vitro, and reversed in vitro, in a manner correlating closely with changes in trypanocidal activity. Macrophages could be activated in vitro with SCF in a time-dependent and dose-dependent fashion, so that they released as much H2O2 as macrophages activated in vivo. The sensitivity of epimastigotes and trypomastigotes to enzymatically generated H2O2 suggested that the generation of H2O2 by activated macrophages could be plausible explanation for their trypanocidal activity. Of the biochemical correlates of macrophage activation reported to date, increased ability to release H2O2 seems most closely allied to enhanced capacity to kill an intracellular pathogen.

Do natural killer cells engage in regulated reactions against self to ensure homeostasis

Abstract: Host reactivities not requiring immunization in the mouse, especially natural resistance of irradiated animals to accept grafts of normal or malignant hemopoietic cells, were compared with NK activity against the YAC-1 lymphoma. The effects of several independent variables known to influence natural resistance in vivo had a similar effect on the NK system. Figure 12 lists an impressive array of shared properties and positive correlations. In contrast, the distinctions were few and minor. Many of the positive correlations were of particular significance since the experimental variables either have opposing or no effects on conventional induced immunity. The multiplicity and pervasiveness of these correlations suggest that the cellular mechanisms underlying natural reactivities are similar or common. Cytotoxic effectors mediating natural resistance to normal cells, tumors, and cells infected with intracellular pathogens may be distinct in terms of target selectivity, yet belong to a single cell lineage subject to common regulatory influences for differentiation and function. Regulation of reactivity via suppressor cells was studied in the NK system only. The spleens of mice selected for low levels of NK activity (resulting from young age, irradiation, and treatment with the macrophage-active agents l-carrageenan or hydrocortisone acetate) contained cells capable of inhibiting the lytic function of NK effectors taken from untreated adult donors. All the suppressor cells studied were thymus-independent, as judged by their occurrence in spleens of genetically athymic mice; the suppressive function was resistant to 2000 rads of gamma-rays administered in vitro and was not restricted by the major histocompatibility complex, without exception. However, two major classes of suppressors were identified: (a) macrophagelike cells inducible by l-carrageenan or hydrocortisone acetate, and (b) nonadherent cells found in spleens of untreated infants and of irradiated adult mice. It is proposed that the suppression of NK cytolysis demonstrated in vitro was a manifestation of regulatory mechanisms modulating the level of NK activity in vivo. Macrophagelike cells that are induced, activated, or inactivated by bacteria, viruses, hormones, and other agents may act as regulators of differentiation, maturation, and function of cells belonging to the NK lineage. Nonadherent cells could be either a distinct class of suppressors or immature NK cells capable of binding but not lysing target cells. In the latter case, regulation would be achieved via competitive binding of targets by pre-NK cells presumably in dynamic equilibrium with functional (i.e. matured) NK effectors.

ATP-dependent renaturation of DNA catalyzed by the recA protein of Escherichia coli

Abstract: The product of the recA gene of Escherichia coli has been purified to near-homogeneity by a simple three-step procedure. Incubation of the recA protein with complementary single strands of DNA, Mg2+, and ATP results in the rapid formation of large DNA aggregates containing many branched structures. As judged by resistance to S1 nuclease and by electron microscopy, these aggregates contain both duplex and single-stranded regions. The renaturation and aggregation of DNA catalyzed by the recA protein is coupled to the hydrolysis of ATP. The recA protein purified from a cold-sensitive recA mutant does not catalyze DNA renaturation or aggregation at 28 degrees C, but does so at 37 degrees C, a finding which correlates with the recombination defect observed in vivo and indicates that this activity is an intrinsic function of the recA protein. These results suggest that the recA protein plays a specific role in strand transfer during recombination and possibly in postreplication repair of damaged DNA.

Interactions of Hyperthermia and Chemotherapy in Animals

Abstract: In tissue culture, the cytotoxicity of a number of commonly used chemotherapeutic drugs is greatly enhanced at elevated temperatures. However, pharmacokinetics, drug concentrations, oxygen tension, and pH in tumors in animals can all vary widely from those in cell cultures. In addition, tissue culture studies do not give vital information on the effect of combinations of drugs and hyperthermia on normal tissues or metastases. Available studies of drugs and hyperthermia in animals are reviewed, and they yield clinically useful information. One study indicated that the activity of methotrexate was not enhanced by hyperthermia in vivo . Results for alkylating agents were not conclusive. Antitumor effects of 1,3-bis(2-chloroethyl)-1-nitrosourea, bleomycin, and cis -diamminedichloroplatinum, however, were significantly potentiated by local hyperthermia. 1,3-bis(2-chloroethyl)-1-nitrosourea effects were enhanced between 41 and 42°C, and thus, it is potentially of use in the setting of systemic hyperthermia. Bleomycin, however, was enhanced significantly only near 43°, suggesting that its clinical use is more appropriate with local hyperthermia. Adriamycin and S -(2-aminoethyl)isothiouronium dihydrobromide, although potentiated in vitro , were not potentiated in vivo in doses which were clinically tolerable. Discrepancies between the in vitro and in vivo findings are likely due, at least in part, to differences in drug concentration. The combination of local primary tumor hyperthermia and chemotherapy did not adversely affect the incidence or severity of spontaneous lung metastases in KHT tumor-bearing mice. Very few studies of the pharmacology of drugs in vivo in the presence of hyperthermia have been reported. Uptake of chemotherapeutic drugs may be enhanced in hyperthermic tissue. Further in vivo studies both of effectiveness and drug pharmacology for combined hyperthermia and chemotherapy are advisable to define optimum time-dose schedules for clinical trials.

Inhibition of collagen gelation by action of the superoxide radical.

Abstract: Superoxide anion, a highly reactive free radical, was generated in vitro using enriched purified xanthine oxidase. Collagen solutions exposed to superoxide radical failed to gel normally when heated to 37 degrees C. The magnitude of the inhibition of gelation was propotional to duration of exposure and to flux of superoxide. Since inhibition of collagen gelation reflects alteration of collagen biochemistry, and/or collagen degradation, it is suggested that the action of free radicals produced in vivo by leukocytes may adversely affect the structural or functional integrity of cartilage and adjacent joint structures.

Growth of a human mammary tumour cell line in a serum-free medium

Abstract: The MCF-7 line of human mammary carcinoma cells is a well characterised line1 which has retained a number of the properties expressed by breast epithelium in vivo, making it a good model for the in vitro study of normal and neoplastic mammary cells. MCF-7 cells have been reported to possess receptors for oestrogen, androgen, progesterone, glucocorticoid2, insulin3 and L-3, 3′, 5-triiodothyronine (T3)4. These cells also show responses to prolactin5, and dome formation1. This line, like most cells in culture, requires the addition of a serum supplement to the medium for growth. The complex and undefined nature of serum adds a complicating aspect to the design and interpretation of any experiments aimed at understanding the interactions of hormones or drugs with mammary epithelium. Our laboratory has shown that it is possible to replace the serum requirement for a number of cell lines with mixtures of hormones and purified serum factors6–8. We now report that MCF-7 cells may be grown, without a lag or adaptation phase, in a serum-free medium supplemented with physiological levels of insulin, transferrin, epidermal growth factor (EGF), prostaglandin F2α (PGF2α) and cold-insoluble globulin (CIg). This medium will support a growth rate identical to that of cells in medium supplemented with an optimal concentration of fetal calf serum. The further addition of the α-1 serum protein first purified by Holmes9 results in a morphology identical to that of cells in 10% serum. Turkington has previously shown EGF effects on mouse mammary expiant cultures10, and mouse EGF has been reported to be stimulatory for human mammary tumour cells . Insulin and transferrin have been shown to be required for the continuous serum-free growth of the ZR-75-1 human mammary tumour cell line12. We believe that this is the first report of the effects of transferrin, PGF2α, Clg, EGF or the α-1 protein on the MCF-7 line.

Insulin binds to brain blood vessels in vivo

Abstract: The brain has generally been considered an insulin-independent organ, because insulin does not apparently exert a direct effect on brain glucose consumption1. Recently, however, insulin receptors have been detected throughout the central nervous system (CNS) of several species2,3. Since important insights into the functional significance of brain insulin receptors might be provided by identification of the cell type(s) possessing these receptors, we have attempted to localise them morphologically using light and electron microscope autoradiography. We report here results indicating that blood vessels throughout the CNS of the rat bind plasma insulin rapidly and with considerable specificity.

Inhibition of the Action of Nonsuppressible Insulin-Like Activity on Isolated Rat Fat Cells by Binding to its Carrier Protein

Abstract: Nonsuppressible insulin-like activity extracted and purified from human serum (NSILA-S) mimics all insulin-like effects in vitro and, after injection, in vivo in the presence of excess insulin antibodies. However, there is no evidence that it exerts acute insulin-like effects in its native form in the circulation, where it is almost completely bound to a specific large molecular weight carrier protein. In this paper we show that partially purified NSILA-S-carrier protein, devoid of endogenous insulin-like activity, inhibits the stimulatory effect of NSILA-S, but not of insulin, on 3-0-methylglucose transport and on lipogenesis from [U-(14)C]glucose in isolated rat fat cells. Concomitantly, it prevents binding of (125)I-labeled NSILA-S to the insulin receptor and to the NSILA-S-binding site. The following explanation is, therefore, offered for the absence of acute insulin-like effects of native NSILA-S in vivo: In native serum NSILA-S occurs almost exclusively as NSILA-S-carrier complex. According to recent findings the passage of this complex through blood capillaries is restricted. The present results indicate that, in addition, it is metabolically inactive, or, at least, possesses reduced metabolic activity. The well-known phenomenon that whole serum, nevertheless, exerts pronounced nonsuppressible insulin-like effects on adipose tissue in vitro seems, therefore, to be mainly caused by the presence of a large molecular weight insulin-like protein not identical to the NSILA-S-carrier complex.

Thy-1 antigen on astrocytes in long-term cultures of rat central nervous system

Abstract: THE THY-1 ANTIGEN has been exploited by immunologists as a marker for thymus-derived lymphocytes in mice1. Since its first description by Reif and Allen, it has been known to be present in equivalent amounts in brain and thymus2. However, in contrast to thymus, where adult levels of Thy-1 are present at birth, Thy-1 in mouse and rat brain increases with physiological maturation of the brain from 1–2% at birth to 100% of the adult level by 3–6 weeks of age2–5. It is widely assumed that neurones are the principal cell type which express Thy-1 and by implication that the increase in brain Thy-1 during neonatal development is related to increases in neuronal membrane as a result of dendritic arborisation5. I describe here the use of monoclonal anti-Thy-1 antiserum in combination with other recently defined neural cell markers6 to study the distribution of Thy-1 on cells grown in long-term cultures of rat central nervous system. I have found that Thy-1 appears on astrocytes as well as neurones and fibroblasts but not on oligodendrocytes, and that the rate of appearance of Thy-1 on cultured astrocytes parallels that of Thy-1 in brain in vivo. This is the first report to identify unambiguously Thy-1 on astrocytes. It settles a controversial point about the Thy-1 distribution on neural cells and clearly demonstrates that previous implications (see discussion) that neurones are the major Thy-1-positive cells in the brain is incorrect.

Rapid In Vivo Assay of Mouse Natural Killer Cell Activity

Abstract: A rapid elimination of tumor cells from some organs was detected in mice following iv injection of tumor cells labeld in vitro with [125I]5-iodo-2'-deoxyuridine. Recovery of radioactivity in different organs (spleen, liver, and lungs) was reduced in mice with high natural killer (NK) cell reactivity in their spleens, as measured in vitro by concomitant short-term 51Cr release assay. Considerable parallelism between in vitro and in vivo reactivities against two mouse lymphomas and a human myeloid cell line was found in mice of different strains and ages. Similarly, various immunophamacologic treatments had comparable effects on in vitro and in vivo reactivities. These findings are consistent with the hypothesis that rapid cytolysis of tumor cells occurred in vivo and that NK cells played a major role in their elimination.

Guinea pig prostate is a rich source of nerve growth factor.

Abstract: NERVE GROWTH FACTOR (NGF) is essential for the development of sympathetic nerve cells1. The richest known source of NGF is the submaxillary gland of the adult male mouse2, and NGF from this source has been completely purified and thoroughly characterised3. The active entity (β-subunit) is a protein comprising a dimer of identical 118-residue chains4,5. Another form of mouse NGF, the 2.5S form, has been isolated6 and shown to differ from the β entity in that some of the monomeric chains have undergone enzymatic cleavage of the amino-terminal octapeptide and carboxy-terminal arginine residues3,4,7–9. The 2.5S dimer therefore contains both 118-residue chains and shortened chains. The salivary gland of the mouse seems to be unique in that the corresponding glands of the rat, guinea pig, cow, pig, rabbit and man contain no NGF10,11. No other clearly characterised source of NGF in mammalian tissue in vivo has been reported. We now report a new, rich source of NGF–the prostate glands of the adult male guinea pig.

Thrombotic complications of heparin therapy: including six cases of heparin--induced skin necrosis.

Abstract: Thrombotic complications of heparin administration were observed in eight patients during a two year period. At sites of subcutaneous heparin injection, six patients developed areas of the skin and subcutaneous necrosis. Systemic thrombotic events and thrombocytopenia were observed in two of these patients when they received intravenous heparin and in two other patients who did not have primary skin necrosis. The complications included peripheral ischemia in three patients (two requiring amputation), myocardial infarction in two, and a cerebral infarction in one. All patients were receiving heparin for at least six days before complications occurred. Seven patients received heparin of bovine origin. Heparin-induced in vitro platelet aggregation was present in all six of the eight patients tested. (It was marked in four of these patients). It is theorized that skin necrosis and the other thrombotic complications observed are the result of heparin-induced in vivo platelet aggregation followed by intravascular thrombosis. Heparin-induced skin necrosis is a rare but serious hazard encountered with prophylactic heparin regimens. If heparin-induced thrombosis is present, the further use of heparin is contraindicated in most instances.

Cadmium: in vivo measurement in smokers and nonsmokers.

Abstract: Absolute amounts of cadmium (in milligrams) in the left kidney and concentrations of cadmium (micrograms per gram) in the liver were measured in vivo in 20 healthy adult male volunteers. Organ cadmium levels of smokers were significantly elevated above those of nonsmokers. No relationship was evident between body stores of cadmium (liver and kidney) and cadmium or beta 2-microglobulin in urine or blood. The average total body burden of cadmium in man at age 50 is estimated to be 19.3 milligrams for nonsmokers and 35.5 milligrams for smokers (38.7 pack-year smoking history). Biological half-time for the whole body was, on average, 15.7 years (10- to 33-year range). Dietary absorption was 2.7 micrograms per day. Cigarette smoking resulted in the absorption of 1.9 micrograms per pack.

Properties of coxsackievirus B3 variants which are amyocarditic or myocarditic for mice.

Abstract: Inoculation of adolescent CD-1 mice with one variant of coxsackievirus B3 (CVB3m) results in induction of readily observable myocardial lesions, whereas inoculation of siblings with a second variant (CVB3o) results in little or no myocarditis. These variants could not be distinquished from each other on the basis of replication properties in HeLa cells or cardiac tissues in vivo, sensitivity to human interferon in HeLa cells, induction of interferon in the mouse, generation of detectable levels of defective-interfering particles in HeLa cells or in cardiac tissue in vivo, stimulation of serum-neutralizing antibody titers, nor in their rate of clearance by the spleen. Infectivity of CVB3o was slightly more heat labile at 34 degrees C than CVB3m. Little if any replication of either CVB3o or CVB3m occurred in either adherent or nonadherent populations of normal murine lymphoid cells. Cardiac tissues from mice inoculated with CVB3m but not CVBo contain new antigens that can inhibit migration of sensitized lymphocytes from CVB3m-immunized mice in an in vitro cell-migration-inhibition assay. However, the CVB3o variant was shown to have the genetic capability of inducing myocarditis if the mice were treated with cyclophosphamide prior to virus inoculation. These results suggest, in agreement with our previously published work, that induction of myocarditis by CVB3 requires destruction of myocytes by virus and subsequent stimulation of cell-mediated responses to new antigens produced in the myocardium during virus replication.

Varying response to luteinizing hormone of two luteal cell types isolated from bovine corpus luteum.

Abstract: Luteal cell suspensions obtained by enzymatic digestion of pregnant cow corpus luteum were found to be heterogenous and mainly made up of two types of cells of different sizes. The large cells (37 micrometers, average diameter) could be separated from the small ones (18 micrometers, average diameter) by sedimentation at unit gravity in a gradient of Ficoll-bovine serum albumin. A comparative in-vitro study of the synthesis of progesterone by the two types of cells indicated striking differences between them. The average content and the synthesis of progesterone in the absence and presence of a saturating dose of bovine LH after incubation for 2 h were 0.07, 0.12 and 6.9 pg/cell for the small cells and 0.65, 2 and 10 pg/cell for the large ones. Moreover, the sensitivity to low concentrations of LH was 100 to 1000 times higher for the small cells than for the large ones. Oestradiol-17 beta at concentrations ranging from 5 X 10(-10) to 5 X 10(-4) mol/l exerted a dose-dependent inhibition on the stimulation of LH in both cell types. These results suggest a possible involvement of both cell types in the synthesis of progesterone in vivo with a greater contribution by the small cells to stimulation induced by LH. Moreover, it appears that small cell suspensions could be a useful model system for in-vitro studies of the control of the synthesis of progesterone in cow corpus luteum.

Time-temperature relationship th hyperthermic treatment of malignant and normal tissue in vivo

Abstract: The effect of hyperthermia on normal and tumor tissue was studied following water bath heating of a methylcholanthrene-induced fibrosarcoma (FSaI) isotransplanted into the feet of C3H mice. The time-temperature relation for the 50% tumor control dose over the temperature range of 41.5--45.5 degrees showed a log linear relationship which followed a biphasically modified Arrhenius plot. At temperatures above 43 degrees, there was a 50% reduction in heating time to obtain the 50% tumor control dose for each 1 degree increase in temperature, corresponding to an activation energy of 140 kcal/mol. At temperatures below 43 degrees, the curve was steeper, with a tendency to double the treatment time for each 0.5 degree reduction in temperature (activation energy, approximately 230kcal/mol). Normal tissue damage in the tumor-bearing foot was estimated at two levels with a 50% response dose assay. Severe normal tissue damage showed a time-temperature relationship similar to the tumor response, thus indicating no variation in therapeutic ratio at different temperatures. However, for slight tissue damage, the therapeutic ratio increased with decreasing temperatures, yielding a better therapeutic ratio at lower temperatures. The time-temperature relationship obtained in the FSaI fibrosarcoma is supported by other studies and points to a general time-temperature relationship for hyperthermic tumor destruction.

In vivo sister-chromatid exchange: a sensitive measure of DNA damage.

Abstract: A variety of chemical agents and X-irradiation were examined for their abilities to induce sister-chromatid exchanges (SCE) in vivo. In addition to demonstrating that several known mutagens and carcinogens are capable of inducing SCE in vivo, our studies indicate that the suspected carcinogen, tris-bromophosphate, can significantly elevate SCE levels. Comparison of the effects of these agents on SCE levels, chromosomal-aberration frequencies and cell-replication kinetics reveals that no consistent relationship exists between SCE levels and other indicators of cellular DNA damage. It is proposed that analysis of SCE induction in vivo may provide a useful technique for the screening of mutagenic and carcinogenic compounds.

Inhibition of specific immune responses by feeding protein antigens. IV. Evidence for tolerance and specific active suppression of cell-mediated immune responses to ovalbumin.

Abstract: We studied the effect of a single intragastric administration of ovalbumin (OVA) on the subsequent development of OVA-specific cell-mediated immune (CMI) responses in BDF1 mice. In animals fed OVA 7 days before subcutaneous sensitization with OVA-CFA, we observed a concomitant dose-dependent decrease in both the humoral and CMI responses specific for OVA. The CMI tolerance was found to be antigen-specific when assayed in vivo by ear swelling or in vitro by an antigen-induced T cell proliferation assay because OVA-fed mice responded normally to sensitization with horse γ-globulin. It was also shown that either spleen or lymph node cells, but not serum, from OVA-fed donors transferred suppression to normal recipients. The transfer was mediated by antigen-specific suppressor T cells (Ts) that appeared to inhibit the induction phase (afferent limb) of the CMI response, since the Ts were only effective when transferred before or shortly after the onset of sensitization.

Receptor-Binding Radiotracers: A Class of Potential Radiopharmaceuticals

Abstract: To date no radiopharmaceutical is routinely used to study changes in receptor concentration. Frequently changes in receptor concentration, or the appearance of receptors in tumors, indicates a specific pathologic state. With a receptor-binding radiotracer, in vivo studies of these changes will be possible. A reversible bimolecular model and in vitro tests were used to determine equilibrium constants and maximal target-to-blood ratios for new derivatives. Theoretical calculations showed that derivatives binding to the estrogen receptor, the beta adrenoceptor, or the cholinergic receptor are capable of achieving satisfactory target-to-blood ratios. Using in vitro tests, the apparent affinity constant was determined for five iodinated estrogen derivatives and five derivatives of beta blockers. Results of the in vitro study with derivatives of beta blockers. Results of the in vitro study with derivatives of beta blockers, and in vivo displacement studies using propranolol, indicated that the high heart-to-blood ratios (5 to 20) obtained with the new derivatives were not the result of a specific interaction with the receptor. In this instance factors other than receptor binding control the in vivo distribution. The in vitro assay using estrogen receptors showed that of the five derivatives, iodohexestrol and 17-alpha-iodoethynylestradiol bind to the receptor with the highest affinity.more » In vivo studies confirmed these results; iodohexestrol gave a uterus-to-blood ratio of 10 in immature rats when plasma-protein binding was blocked. With a tritiated muscarinic cholinergic blocking agent, heart-to-blood ratios near the theoretical maximum were obtained. This compound most closely follows the mechanism described by the model. Use of the theoretical model in conjunction with in vitro assays can greatly aid in the design of this new class of receptor-binding radiopharmaceuticals.« less

An Lyt differentiated thymocyte subpopulation detected by flow microfluorometry.

Abstract: DATA on the T-cell antigens, Lyt 1, 2, 3 (refs 1, 2), relating to functional T-cell subsets, suggest that some peripheral T cells express restricted Lyt phenotypes, that is, Lyt 1+23− or Lyt 1−23+ (ref. 3). Evidence has been presented showing that two major subpopulations of lymphocytes, Lyt 1+ T cells and Lyt 23+ T cells, are committed to particular lines of functional differentiation in the immune response before encountering exogenous antigen in peripheral lymphoid tissue4,5. It has been suggested that the two major subpopulations representing T-cell help (Lyt 1+) and T-cell cytotoxicity or suppression (Lyt 23+) arise in the periphery from peripheral Lyt 123+ cells6. Recent studies have concluded that as stem cells mature in the thymus, the thymic epithelium is important in determining which H–2 specificities the maturing T cells are able to recognise as self7. Previous cytotoxicity data have been interpreted as indicating that Lyt 1, 2, 3 antigens are expressed on each of most if not all, mouse thymocytes; that is, that most thymocytes are Lyt 123+ (refs 1–4, 8–10). However, the data presented here suggest that the commitment to differentiation of the Lyt 1+ or the Lyt 123+ phenotype, and thus presumably the relevant functional differentiation occurs before cell migration from the thymus. Using flow microfluorometry (FMF) and anti-Lyt antisera, we demonstrate a normal thymocyte subpopulation which is not expressing Lyt 2 or Lyt 3 antigens (Lyt 1+23−). This subpopulation represents a significant constant proportion (10%) of normal thymocytes which is markedly increased following in vivo cortisone treatment. The data also show that Lyt 1 expression, rather than being decreased on cortisone-resistant thymocytes (CRT), as would have been predicted from previous cytotoxicity data2,8, is expressed in increased amounts on CRT.

Radiosensitization of hypoxic tumor cells by cis- and trans-dichlorodiammineplatinum (II)☆

Abstract: The effects of the chemotherapeutic agent cis -dichlorodiammineplatinum (II) or its trans isomer on tumor cell lethality were evaluated following administration of the drugs, alone, or in combination with x-irradiation. The tumor latency method was employed to assay tumor cell survival under in vivo growth conditions following treatment in vivo . Radiosensitization of hypoxic tumor cells was demonstrated by combinations of either complex with high doses of radiation. The results extend an effect observed in bacterial systems and cultured mammalian cells to include tumor cells treated in situ . However, therapeutic potentiation during more clinically relevant treatment protocols in air-breathing mice is probably the result of the platinum complexes inhibiting recovery processes following irradiation.