Mechanisms of serotonin-induced lymphocyte proliferation inhibition

When human peripheral blood lymphocytes were stimulated with phytohemagglutinin in the presence of serotonin, inhibition of [3H]thymidine incorporation occurred, the most marked inhibition occurring at high (10(-3)M) serotonin concentrations. This effect could not be reversed by the addition of Interleukin 2 (IL-2)-containing supernatants. Cytofluorometric analysis showed that virtually all of the cells remained in the G0 phase (unactivated) at 24 hr while some of the cells entered the G1a and G1b phases of the cell cycle by 42 hr. The cellular production of IL-2 was not affected by serotonin, as supernatants of treated cultures contained essentially the same IL-2 titers as did control cultures. Serotonin seemed to primarily affect cell activation and had little or no effect on proliferating cells. This was further confirmed by the lack of effects of serotonin on a variety of established proliferating lymphocyte, macrophage, and fibroblast cell lines. By contrast, dose-dependent inhibition of IL-2-dependent CTLL cells occurred. Serotonin was not toxic even at 10(-3) M concentrations. A marked decrease in IL-2 receptors and a change in their distribution on responder cells was seen when treated cultures were examined with the anti-Tac monoclonal antibody. At 24 hr this effect was contrastingly not seen for the OKT-8 marker, although a slight decrease in OKT-4-positive cells was seen. Serotonin thus produced an inhibition of lectin-stimulated lymphocyte proliferation via a mechanism independent of IL-2 production, and caused a decrease in the expression and distribution of IL-2 receptors on the surface of responder cells.

Antitumor activity and toxicity of ACNU, 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1-nitroso urea hydrochloride, comparing two divided doses and a single dose

In order to determine whether it is possible to reduce the toxicity of the nitrosoureas, including the delayed type of hematologic toxicity, without diminishing antitumor activity by administering the drug according to a new treatment schedule other than the single high-dose treatment schedule, we examined the antitumor activity against murine tumors and toxicities to host mice of a nitrosourea derivative, 3-[(4-amino-2-methyl-5-pyrimidinyl)methyl]-1-(2-chloroethyl)-1- nitrosourea hydrochloride (ACNU), which was administered according to two divided doses schedule. Experimental results indicated that the toxicity of ACNU with respect to lethality, as well as weight loss of host mice, was alleviated by administering ACNU (IV) at one-half of LD10 (20 mg/kg) on 2 successive days. However, no impairment of the antitumor activity of ACNU in various murine tumor systems was observed in comparison with that of ACNU administered according to the single high-dose schedule. The delayed type of hematologic toxicity (leukopenia) could not be alleviated by this treatment schedule.

A Study of 11C-Benzoate as a Radiopharmaceutical for Renal Imaging

11C-benzoic acid prepared in a radiochemical purity over 90% was studied radiopharmacologically in mice and rabbits. The uptake of 11C-benzoate in ICR mice increased quickly. The ratio of kidney uptake rate to that in other organs reached values between 9 and 55 with a maximum at 10 min after i.v. injection. Gamma camera imaging of rabbits showed that uptake in the kidneys began at 2 min after injection and that activity began to appear in the bladder 4 min later. Rabbits with left renal artery ligature showed no uptake in the left kidney but the right kidney was imaged to the same extent as that of a rabbit without artery ligature. The kidney imaging of 11C-benzoic acid may be a useful method for renal diagnosis.

Cell cycle-related changes in number of T-lymphocyte receptors for glucocorticoids and insulin

Enriched human peripheral T-lymphocytes were stimulated with PHA and examined for variations in insulin and glucocorticoid (dexamethasone) receptor numbers during the early phases of the cell cycle. Cells in G0, G1a and G1b phases, where the G1a - G1b transition is an Interleukin 2 dependent event, were quantitated by flow cytometry. Few but significant numbers of glucocorticoid receptors (2700/cell) and no insulin receptors (-1/cell) were found in the resting (G0) phase. As cells entered the G1a phase the specific binding of dexamethasone increased and of insulin took place. Although the specific binding further increased as T-cells entered the G1b phase (as measured at 44 h of incubation and using hydroxyurea-treated cells), the major changes in the specific binding of dexamethasone took place during the period 16 - 20 h after stimulation. Based on these findings, it is concluded that both receptor types (cell membrane and cytoplasmic receptors) are being formed and increased at G1 phase prior to cell proliferation, indicating the importance of G1 phase in immunoregulation.

Transcription and translation dependent induction of interleukin 2 (IL-2) and IL-2 receptors

Our previous findings on the expression of Interleukin 2 (IL-2) receptors have shown that under the influence of certain drugs, it was possible to dissociate IL-2 production from the appearance of IL-2 receptors on human peripheral blood lymphocytes (PBL). Therefore, we studied whether the induction of IL-2 receptors were transcription- or translation-dependent. Actinomycin D and puromycin inhibited the appearance of IL-2 receptors as well as the production of IL-2. Furthermore, both drugs also inhibited human PBL to enter the G1 phase of the cell cycle. Thus, these data suggested that both IL-2 production and the appearance of IL-2 receptors were dependent on transcription and translation in non-resting cells.

Effect of gossypol on DNA synthesis and cell cycle progression of mammalian cells in vitro

Gossypol, a yellow phenolic compound extracted from cotton plants that is being used as a male antifertility drug, has been found to have cytotoxic effects. The objective of the present study was to determine the cause of these cytotoxic effects in cultured cells and to ascertain whether cells in certain phases of the cell cycle were more sensitive to the drug than were cells in other phases. HeLa or Chinese hamster ovary cells were exposed to various concentrations of gossypol for varying periods of time, and the effects of the drug on the growth rate, cell cycle traverse, plating efficiency, and macromolecular synthesis were measured. The results of this study indicate that gossypol is a specific inhibitor of DNA synthesis; it has no effect on RNA and protein synthesis at a concentration of 10 micrograms/ml and hence has no effect on the cell cycle traverse of cells from G2 to the beginning of S phase. In the presence of the drug, cells can enter S phase but fail to complete replication. The effects of the drug on growth rate and plating efficiency indicate that there is a threshold concentration at which gossypol becomes effective as a cytotoxic agent. Gossypol did not increase chromosome aberrations in the treated cells. Since gossypol irreversibly blocks cells in S phase, it could be useful as an antitumor drug.

Analysis of 3H-histamine interaction with lymphocytes: receptor binding or uptake?

The immunoregulatory role of histamine is presumably mediated by specific receptors on the plasma membrane of lymphocytes. However, using murine spleen cells and a whole cell assay commonly applied in hormone receptor studies, specific histamine receptors with an affinity higher than that of non-specific binding could not be identified. Nevertheless, approximately 30% of the totally bound histamine was undissociable over a range of added histamine concentrations (9 X 10(-6)-1 X 10(-2) M). Lectin stimulation of spleen cells caused an additional two-fold increase of undissociable histamine. The H1 receptor antagonist, diphenhydramine, blocked histamine uptake, whereas the H2 receptor antagonist, cimetidine, had no effect. Binding experiments carried out at 4 degrees C demonstrated that the amount of undissociable histamine was much reduced. Even at 4 degrees C, evidence for specific membrane associated histamine receptor could not be obtained. It was therefore concluded that lymphocytes take up histamine by an energy-dependent mechanism inhibitable by diphenhydramine but not cimetidine, and that the usual hormone receptor methodology did not allow the identification of specific membrane associated histamine receptors.

Enhanced production of hepatitis B surface antigen in NIH 3T3 mouse fibroblasts by using extrachromosomally replicating bovine papillomavirus vector

We have constructed a recombinant pBR322 plasmid composed of a subgenomic transforming fragment of bovine papillomavirus DNA and the hepatitis B surface antigen gene from cloned hepatitis B virus DNA and used it for transfection of NIH 3T3 mouse fibroblasts. The transformed cells retain the plasmids in extrachromosomal form with a copy number of about 50 to 100 per cell. Expression of the hepatitis B surface antigen gene linked to bovine papillomavirus DNA is independent of its orientation relative to the bovine papillomavirus vector. Cell lines continuously secreting high amounts of hepatitis B surface antigen into the medium could be established. The antigen is released into the culture medium as 22-nm particles, having the same physical properties and constituent polypeptides as those found in the serum of hepatitis B virus-infected patients.

Total synthesis of yeast alanine transfer ribonucleic acid

By a combination of chemical and enzymatic methods, small oligonucleotides with lengths varying from 2 to 8 nucleotides were synthesized from mononucleotides. The small oligonucleotides were then ligated with T4 RNA ligase into six large oligonucleotides (9 to 19 nucleotides long) which were further ligated to form two half molecules with 35 and 41 nucleotides respectively. Finally, the two synthetic half molecules were annealed and ligated to obtain the whole molecule of yeast alanine tRNA (tRNAAlay). Prior to this, two semi-syntheses were performed, i.e. ligation of the synthetic 5'-half molecule with the natural 3'-half molecule and that of the natural 5'-half molecule with the synthetic 3'-half molecule. Both the semi-synthetic tRNAAlay and the synthetic tRNAAlay occupy the same position as the natural tRNAAlay after electrophoresis on a 20% polyacrylamide gel. They have the same chemical composition (containing 9 modified nucleotides of 7 different species) and structure as the natural tRNAAlay and are biologically active, i.e. accepting and transferring alanine into proteins in a cell-free protein synthesizing system, the accepting activity of the synthetic product is 52-66% of that of the natural tRNAAlay and 91-106% of that of the reconstituted product of the two natural half molecules. The incorporation activity of alanine into proteins of the synthetic 3H-alanine tRNAAlay is 63%, corresponding to 91% of that of the natural tRNAAlay and 115% of that of the reconstituted product of the two natural half molecules. To the best of our knowledge, this is the first time that a natural RNA with biological activity is synthesized.

Acute upper gastrointestinal bleeding in the aged. A retrospective analysis of 100 cases

One hundred consecutive patients (predominantly men, aged 60 years and older), who were admitted to the Hsinhua Hospital, Shanghai, with acute bleeding from the gastrointestinal tract during a three-year period, were reviewed. The most common causes of bleeding were peptic ulcers, chronic gastritis, prolapse of gastric mucosa, and other benign conditions. In 22 patients, bleeding was either due to oesophageal varices, or was a complication of cor pulmonale. The incidence of malignant disease was 23% (higher than that reported from the United States or the United Kingdom). The mortality rate in patients with benign causes of gastrointestinal bleeding (after exclusion of patients with malignant disease, cor pulmonale, and hepatic cirrhosis) was 4.4%--much lower than the British rate, but slightly higher than that reported in an Australian study. It is hoped that, with the increasing interest in geriatrics, and closer attention to acute bleeding from the gastrointestinal tract in the aged, the mortality rate from this condition will decline.

Effects of villin on the polymerization and subunit exchange of actin

We have investigated the Ca2+ -dependent interactions of villin, a protein of the intestinal microvillar core, with actin by monitoring resonance energy transfer between fluorescently labeled actin subunits. In the presence of elevated free Ca2+ (approximately 20 microM), villin affects both the nucleation and the elongation phases of actin polymerization. Consistent with previous reports, villin stimulates the nucleation process and will form stable nuclei under depolymerization conditions. Compared to the control, the net rate of polymerization is slightly inhibited at low concentrations of villin (villin/actin approximately 1:400) but is stimulated at higher concentrations (villin/actin greater than 1:100). Villin also significantly increases the critical concentration of actin polymerization. Addition of either villin or villin-actin complexes induces depolymerization of preassembled actin filaments. This villin-induced depolymerization is reversible upon removal of free Ca2+ or upon the addition of phalloidin. The exchange of actin subunits at steady state is inhibited at low concentrations of villin (villin/actin approximately 1:200) but is stimulated at higher concentrations (villin/actin approximately 1:50). None of the above effects is observed at less than 10(-8) M free [Ca2+].

Aging and immunity: decrease in interleukin-2 production and interleukin-2-dependent RNA-synthesis in lectin-stimulated and murine spleen cells

The RNA-content of G1 cells in lectin-stimulated spleen cell cultures of young and aged NMRI mice was determined by flow cytometry. In spleen cells of aged mice a preferential decrease of G1 cells with a high RNA-content, so-called G1b cells, was found. Since, as shown in a previous report, only cells with a high RNA-content are able to proliferate and the passage of low (G1a) to high (G1b) RNA-content is interleukin-2(IL-2)-dependent, the ability of young and old spleen cells to produce IL-2 was tested. In old spleen cells a diminished production of IL-2 was found. Addition of external IL-2, however, did not increase the proliferative capacity of old spleen cells, nor did it induce more G1b cells. Thus spleens of aged mice contain cells, which can be activated by lectin, but then fail to respond to IL-2. Both decrease in IL-2 production and receptivity for IL-2 may contribute to the diminishing immune response in aging individuals.

Expression of hepatitis B surface antigen in unselected cell culture transfected with recircularized HBV DNA

Hepatitis B virus (HBV) DNA was isolated from the recombinant plasmid pA01 -HBV and recircularized . Immediately after introduction of this DNA into mouse fibroblasts (NIH 3T3) we observed increasing release of hepatitis B surface antigen (HBsAg) into the culture medium. Later production of HBsAg declined to a lower but constant level. No dominant selective marker and foreign promoter were necessary in this system, which therefore can be used for the study of regulation of HBsAg expression.

Rest and exercise hemodynamics after the Fontan procedure

Sixteen consecutive patients (12 with tricuspid atresia) underwent a Fontan procedure, with no operative deaths. There were three late deaths. Eleven of the survivors were electively catheterized 4-25 months postoperatively. Rest and exercise hemodynamics were measured in five patients, and resting hemodynamics alone were measured in three. All exercised patients were New York Heart Association class I Cardiac index was low at rest (2.3 +/- 0.61/min/m2) and during exercise (4.9 +/- 1.11/min/m2) due to a low stroke index both at rest (28 ml) and exercise (35 ml). Accordingly, mixed venous oxygen saturations were decreased (66% at rest and 31% during exercise). These values are significantly lower than those at rest and during exercise from 23 control patients of similar age and size. Heart rates, pulmonary vascular resistances, and left ventricular filling pressures appeared normal both at rest and during exercise. High right atrial pressure at rest (15 mm Hg) was associated with minimal conduit gradient (2 mm Hg). However, exercise increased the mean conduit gradient to 8 mm Hg, demonstrating significant functional conduit obstruction. As expected, the cardiovascular response to exercise is abnormal after the Fontan procedure, even in asymptomatic patients. This abnormal response may be exacerbated by conduit obstruction, and conduit obstruction may not be apparent during resting studies.

Liposomes as gene carriers: efficient transformation of mouse L cells by thymidine kinase gene

Stable transformation of mouse L cells deficient in thymidine kinase was achieved by liposome-mediated transfer of a recombinant plasmid carrying the thymidine kinase gene. Ten percent of the recipient cells expressed thymidine kinase activity. The transformed phenotype (for example, 200 out of 10(6) cells) was stable under selective and nonselective conditions. The liposome technique is compared with other methods currently used for gene transfer.

Gene transfer into mouse lyoma cells by electroporation in high electric fields

Electric impulses (8 kV/cm, 5 microseconds) were found to increase greatly the uptake of DNA into cells. When linear or circular plasmid DNA containing the herpes simplex thymidine kinase (TK) gene is added to a suspension of mouse L cells deficient in the TK gene and the cells are then exposed to electric fields, stable transformants are formed that survive in the HAT selection medium. At 20 degrees C after the application of three successive electric impulses followed by 10 min to allow DNA entry there result 95 (+/- 3) transformants per 10(6) cells and per 1.2 micrograms DNA. Compared with biochemical techniques, the electric field method of gene transfer is very simple, easily applicable, and very efficient. Because the mechanism of DNA transport through cell membranes is not known, a simple physical model for the enhanced DNA penetration into cells in high electric fields is proposed. According to this ' electroporation model' the interaction of the external electric field with the lipid dipoles of a pore configuration induces and stabilizes the permeation sites and thus enhances cross membrane transport.

Recombinant retroviral DNA yielding high expression of hepatitis B surface antigen

A genomic fragment of hepatitis B virus encoding the surface antigen (HBsAg) was inserted into the proviral genome of Moloney mouse sarcoma virus (MSV), obtained from the mouse cell line G8 -124. The recombinant DNA was introduced into NIH 3T3 mouse fibroblasts. Cells, morphologically transformed by the oncogene of MSV (v-mosM) were selected, established as cell lines and tested for expression of HBsAg. An expression level of up to 4.5 micrograms/10(7) cells/day was detected.

The pathophysiology of angina pectoris and the effect of lidoflazine

Angina pectoris results from a deficiency in myocardial oxygen supply. The rate-pressure product is an important predictor of myocardial oxygen requirements in patients with ischemic heart disease and in normal persons. The rate-pressure product at the onset of angina pectoris is reproducible under a variety of circumstances with a suitable protocol. In some patients, coronary artery spasm may reduce myocardial blood flow and contribute to the development of angina pectoris. Lidoflazine is a synthetic drug that appears to be a calcium-entry blocker and results in symptomatic improvement in patients with angina pectoris. Lidoflazine reduces the exercising rate-pressure product by its effect on heart rate and by decreasing systemic vascular resistance. It decreases coronary vascular resistance and antagonizes processes leading to an increase in coronary vasomotor tone.