PubMed Health⌕ Search

Biomedical subjects

S K Beckner

Publications and source records attributed to S K Beckner.

At least 19 recordsLinked to original sources
PubMed2000

Effect of menstrual cycle on HIV-1 levels in the peripheral blood and genital tract. WHS 001 Study Team.

OBJECTIVE: To assess the variation in HIV-1 over the menstrual cycle, including RNA levels in the female genital tract, plasma HIV-1-RNA levels, CD4 cell counts, and culturable virus. DESIGN: A prospective analysis of 55 HIV-1-infected women. METHODS: Blood and genital tract specimens were collected weekly over 8 weeks, spanning two complete menstrual cycles. Applying repeated-measures models that used menses as the reference level, the variation in viral RNA levels was compared in endocervical canal fluid and cells (collected by Sno-strips and cytobrush, respectively) and ectocervicovaginal lavage (CVL) fluid. Repeated-measures models were also used to assess the variation in plasma CD4 cell counts and viral load. RESULTS: Shedding patterns differed among the three sampling methods, independent of genital tract co-infections. Genital tract HIV-1-RNA levels from CVL fluid and endocervical canal cytobrush specimens were highest during menses and lowest immediately thereafter (P = 0.001 and P = 0.04). The HIV-1-RNA level in endocervical canal fluid was highest in the week preceding menses (P = 0.003). The menstrual cycle had no effect on blood levels of RNA (P = 0.62), culturable virus (P = 0.34), or CD4 cell counts (P = 0.55). HIV-1-RNA levels were higher in endocervical canal fluid than in peripheral blood plasma during the late luteal phase (P = 0.03). CONCLUSION: HIV-1-RNA levels vary with the menstrual cycle in the female genital tract but not the blood compartment. HIV-1-RNA levels are higher in endocervical canal fluid than in blood plasma. These findings may have important implications for sex-specific pathogenesis, heterosexual transmission, and contraceptive hormone interventions in HIV-1-infected women.

Adult↗
PubMed1992

A colorimetric method for detection of specific ligand binding.

The binding of IL-2 and IL-3 to the factor-dependent cell lines CTB6 and 32D, respectively, was determined using biotinylated ligand detected by the addition of a streptavidin/alkaline phosphatase conjugate and amplified with a phosphatase amplification system. Binding of both ligands was detectable after incubation with as little as 20 fmol of ligand and could be inhibited with a 10-fold molar excess of nonbiotinylated ligand. No binding was observed when biotinylated ligand was incubated with a receptor negative cell line (PC-12) and IL-2 was unable to compete with biotinylated IL-3 binding to 32D cells, further demonstrating specificity. These studies indicate that biotinylated ligands can be used as a nonradioactive method to detect specific, high-affinity cell surface receptors.

Alkaline Phosphatase↗
PubMed1990

Intraperitoneal lymphokine-activated killer-cell and interleukin-2 therapy for malignancies limited to the peritoneal cavity.

Autologous lymphokine-activated killer (LAK) cells and recombinant human interleukin-2 (rIL-2) were administered intraperitoneally (IP) to 24 patients with malignancies limited to the peritoneal space. Ten patients had ovarian cancer, 12 had colorectal cancer, and one patient each had endometrial carcinoma and primary small-bowel adenocarcinoma. All ovarian cancer patients, three of twelve colorectal cancer patients, and one patient with endometrial carcinoma had received prior therapy. Patients received IL-2 100,000 U/kg every 8 hours intravenously (IV) for 3 days, and 2 days later underwent daily leukapheresis for 5 days. LAK cells were generated in vitro by incubating the peripheral blood mononuclear cells in IL-2 for 7 days and were then administered IP daily for 5 days through a Tenckhoff catheter (Davol, Inc, Cranston, RI) together with IL-2 25,000 U/kg IP every 8 hours. All but one patient completed at least one cycle of therapy. Toxic side effects included minor to moderate hypotension, fever, chills, rash, nausea, vomiting, abdominal pain and distension, diarrhea, oliguria, fluid retention, thrombocytopenia, and minor elevations of liver function tests; all of these rapidly improved after discontinuation of IL-2. One patient had a grand mal seizure, and one suffered a colonic perforation; these were felt to be treatment-related. IP fibrosis developed in 14 patients and limited repeated cyclic administration of this therapy in five patients. Two of 10 (20%) ovarian cancer patients and five of 12 (42%) colorectal cancer patients had laparoscopy- or laparotomy-documented partial responses. We conclude that LAK cells and rIL-2 can be administered IP to cancer patients, resulting in moderate to severe short-term toxicity and modest therapeutic efficacy. Further investigation of this form of adoptive immunotherapy modified to address the problem of IP fibrosis and with lower IP IL-2 doses is justified by these initial results.

Adult↗
PubMed1989

Cytokine gene expression during the generation of human lymphokine-activated killer cells: early induction of interleukin 1 beta by interleukin 2.

Culture of human peripheral blood leukocytes with interleukin 2 (IL-2) stimulates their differentiation into lymphokine-activated killer (LAK) cells, with a broad range of cytotoxicity against fresh tumor cells and tumor cell lines (Grimm et al., J. Exp. Med., 155: 1823-1841, 1982). We chose to utilize a molecular approach to determine whether IL-2 stimulates the expression of cytokine genes by the mixed cell population which may be involved in the generation or regulation of lytic activity. Northern blot analysis performed with total cellular RNA from LAK cells cultured for varying periods of time with IL-2 revealed that the genes which code for cytokines [interleukin 1 (IL-1)alpha and beta, gamma-interferon, tumor necrosis factor alpha, and lymphotoxin] were not spontaneously expressed. As soon as 2 h after IL-2 treatment, IL-1 alpha and IL-1 beta mRNAs were expressed. Both nonadherent and adherent populations of LAK cells express IL-1 beta mRNA; however, the adherent population produced more IL-1 beta mRNA and maintained its expression for a prolonged period of time. Other cytokine mRNAs (gamma-interferon, tumor necrosis factor alpha, and lymphotoxin) were expressed later than the IL-1 mRNAs with maximal levels between Days 2 through 7. Our results indicate that LAK cell populations can generate a variety of cytokines which may be involved in the generation of lytic activity.

Cell Separation↗
PubMed1988

Potentiation of lymphokine-activated killer cell differentiation and lymphocyte proliferation by stimulation of protein kinase C or inhibition of adenylate cyclase.

Interleukin 2 (IL-2) stimulated the differentiation of human peripheral blood leukocytes into lymphokine-activated killer cells, as well as DNA synthesis of human T lymphocytes. Both effects of IL-2 could be inhibited by prostaglandin E2, a potent stimulator of adenylate cyclase; however, the inhibitory effect of prostaglandin E2 could be overcome by increased concentrations of IL-2. The opposite effects of IL-2 and prostaglandin E2 were paralleled by their respective abilities to inhibit and stimulate cAMP production in intact cells. Other agents, which inhibit adenylate cyclase directly (somatostatin, beta-endorphin, UK 14.3041) or indirectly by activation of protein kinase C (phenylephrine), could stimulate both differentiation and proliferation. None of these agents alone or in combination were as effective as maximal concentrations of IL-2. However, all agents potentiated differentiation and proliferation induced by submaximal and maximal concentrations of IL-2. Additionally, combinations of agents which stimulated protein kinase C with those that inhibited adenylate cyclase were additive in the potentiation of IL-2-induced differentiation. Neither inhibition nor potentiation of IL-2-induced lymphokine-activated killer cell differentiation was accompanied by changes in Tac expression or gamma-interferon production. The data indicate that the stimulation of lymphokine-activated killer cell differentiation and lymphocyte proliferation in human cells share a common initial biochemical signal. Although the inhibition of adenylate cyclase is not sufficient to maximally stimulate either process and cannot bypass the requirement for IL-2, modulation of this enzyme complex, positively or negatively, can regulate the ultimate physiologic response to IL-2.

Adenylyl Cyclase Inhibitors↗
PubMed1987

Lymphokine-activated killer cells: culture conditions for the generation of maximal in vitro cytotoxicity in cells from normal donors.

The current method for generating lymphokine-activated killer (LAK) cells for use in human clinical trials is both labor intensive and expensive. Therefore, we altered cell culture conditions to determine whether LAK cells with enhanced lytic activity could be generated. Culture of normal human peripheral blood leukocytes for 7 days generated LAK cells with 4-fold more lytic activity than culture for 3 days. Although cell viability over this 7-day period dropped from 94% on Day 3 to 73% by Day 7, the recovery of cells from culture increased from 61 to 106%. If cells were exposed to CO2, lytic activity was further enhanced by up to 30-fold. Culture at a density of 1 or 2.5 X 10(6) cells/ml caused no difference in cell viability, recovery, or LAK activity when cells were cultured for up to 4 days; however, when cells were cultured for longer times, an initial density of 1 X 10(6) cells/ml yielded maximal LAK activity. Several commercially available serum-free defined media as well as human serum albumin supported LAK cell activation comparable to serum-containing media over a 4-day culture period. One defined medium, AIM V, supported LAK cell activation over a 7-day period even when cells were cultured at a density twice as high (2 X 10(6) cells/ml) as cells cultured in serum-containing medium. The results demonstrate that simple manipulation of human LAK cell culture conditions generates cells with greatly enhanced lytic activity and that serum-containing medium may not be necessary for generating LAK cells under the current clinical protocols.

Cells, Cultured↗
PubMed1987

Inhibition of adenylate cyclase by IL 2 in human T lymphocytes is mediated by protein kinase C.

Interleukin 2 (IL 2) inhibited basal as well as PGE2, isoproterenol and forskolin stimulated cAMP production in human T lymphocytes. Although the stimulation of adenylate cyclase by activators of the enzyme was evident in lymphocyte membrane preparations, the inhibitory effect of IL 2 was observed only if cells were pretreated with IL 2 and the membranes activated with Ca++ and ATP. Additionally, when purified protein kinase C was reconstituted into untreated membranes and activated with Ca++ and ATP, both receptor and non-receptor stimulated adenylate cyclase was inhibited. These results suggest that the inhibition of adenylate cyclase in human T lymphocytes by IL 2 is mediated by protein kinase C.

Adenosine Triphosphate↗
PubMed1987

Induction of glucagon sensitivity in a transformed kidney cell line by prostaglandin E2 and its inhibition by epidermal growth factor.

A model system using a transformed dog kidney cell line (Madin-Darby canine kidney), has been established for studying the process of differentiation. Glucagon responsiveness can be restored to these transformed cells by various differentiation inducers, including prostaglandin E2. Glucagon response was measured in terms of the ability of glucagon to stimulate cAMP production. Induction of glucagon sensitivity seems to be mediated by cAMP. The ability of various prostaglandin analogs to elevate the cAMP level correlates closely with their ability to induce glucagon sensitivity. In fact, 8-Br-cAMP is also a potent inducer. To define the nature of this cAMP-mediated process, we identified several inhibitors of this induction process. These differentiation inhibitors include serum, phorbol ester, and epidermal growth factor. These inhibitors do not have a direct effect on cAMP production by cells in the presence or absence of hormones. Furthermore, induction by 8-Br-cAMP is also inhibited by these agents. Therefore, the site of inhibition is located beyond the point of cAMP production. Possible interaction between cAMP- and epidermal growth factor-dependent phosphorylations is discussed.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Decreased potency of glucagon on transformed-induced MDCK cells does not reflect an alteration of adenylate cyclase components.

The selective loss of glucagon sensitivity of transformed MDCK cells can be restored by differentiation inducers, a process which requires RNA and protein synthesis and glycosylation. Although the glucagon dose-response curve of normal MDCK cells resembled that of liver and kidney (Kact = 10 nM), the transformed-induced cells were 10-fold less sensitive to the hormone [activation constant (Kact) = 100 nM]. Additionally, the stimulation of cAMP synthesis by a glucagon fragment (glucagon) in transformed-induced cells was greatly reduced compared to normal cells. The adenylate cyclase regulatory components of transformed-induced MDCK cell membranes seemed unaltered compared to the parental line. Both contained equivalent amounts of cholera and pertussis toxin substrates, and soluble extracts were equally capable of reconstituting isoproterenol responsiveness of S49 cyc- membranes. However, membrane fusion studies demonstrated that the glucagon sensitivity of transformed-induced membranes could not be reconstituted with heterologous membranes. When donor transformed-induced membranes (with inactivated adenylate cyclase) were fused with acceptor HeLa membranes (normally unresponsive to glucagon and prostaglandin E), such hybrids were unresponsive to glucagon, although responsiveness to prostaglandin E was evident. Parallel hybrids with normal MDCK membranes were responsive to both glucagon and prostaglandin E. This difference could not be explained by an inhibitory effect of transformed-induced membranes on receptor-adenylate cyclase coupling under the fusion conditions: the ability of these membranes to serve as an acceptor for the reconstitution of vasoactive intestinal peptide responsiveness was identical to that of normal MDCK cells. The data suggest that the glucagon sensitivity induced in transformed MDCK cells differs significantly from that of the parental line. However, these differences cannot be explained by alterations of transformed-induced membrane components relevant to the coupling of hormone receptors to adenylate cyclase.

Adenylyl Cyclases↗
PubMed1986

Interleukin 2 modulation of adenylate cyclase. Potential role of protein kinase C.

Interleukin 2 (IL 2) stimulated DNA synthesis of murine T lymphocytes (CT6) in a concentration-dependent manner, over a range of 1-1000 units/ml. This proliferative effect of IL 2 was attenuated by simultaneous exposure to prostaglandin E2 (PGE)2. In intact cells, IL 2 inhibited both basal and PGE2-stimulated cAMP production; the amount of cAMP generated was dependent upon the relative concentrations of IL 2 and PGE2. The effect of IL 2 on CT6 cell proliferation and cAMP production was mimicked by the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), which, like IL 2, causes a translocation and activation of protein kinase C. While PGE2 stimulated adenylate cyclase activity in membrane preparations, neither IL 2 nor TPA inhibited either basal or stimulated membrane adenylate cyclase activity. However, when CT6 cells were pretreated with IL 2 or TPA and membranes incubated with calcium and ATP, both basal and PGE2-and NaF-stimulated membrane adenylate cyclase activity was inhibited. This inhibition of adenylate cyclase activity was also observed if membranes from untreated cells were incubated with protein kinase C purified from CT6 lymphocytes in the presence of calcium and ATP. The data suggest that the decreased cAMP production which accompanies CT6 cell proliferation results from an inhibition of adenylate cyclase activity mediated by protein kinase C and that these two distinct protein phosphorylating systems interact to modulate the physiological response to IL 2.

Adenylyl Cyclases↗
PubMed1986

The effect of viral transformation on prostaglandin production depends on cell type.

The role of prostaglandins in cellular differentiation and transformation has been widely studied. We have found previously that prostaglandin E2 production was greatly diminished in dog kidney cells (MDCK) after transformation by Harvey murine sarcoma virus. In the present study, we have shown that viral transformation can have differing effects in the ability to modify the production of prostaglandin in cultured cells. For example, the prostaglandin E2 production in rat kidney cells (NRK) is decreased after transformation by Rous sarcoma virus, while production in 3T3 cells is increased markedly after transformation by the same virus. Similarly, SV40 transformation increases prostaglandin E2 production of 3T3 cells and decreases the production in rat thyroid cells (FRTL). These results indicate that the biosynthetic pathway for prostaglandin production has varying susceptibility following viral transformation and the effect of transformation depends more on the type of cell than virus. Taking advantage of the well-defined transforming proteins encoded by polyomavirus, we have further studied the relationship between prostaglandin production in cells and the expression of T antigens in transformed cells. We showed that the expression of middle T antigen, which is associated with a protein kinase and is responsible for phenotype of transformed cells, is required for the change in prostaglandin production in cells. How these changes of prostaglandin production relate to the progression of viral transformation remains to be explored.

Animals↗
PubMed1985

Expression of glucagon sensitivity by transformed MDCK cells normally unresponsive to glucagon: early commitment to differentiation.

A cloned line of canine kidney cells (MDCK) transformed with Harvey murine sarcoma virus, in contrast to the parental, untransformed line, expressed glucagon sensitivity only under controlled culture conditions. The glucagon sensitivity of transformed MDCK cells appeared after 10 days of culture if plated at less than 100,000 cells/dish or after 3 days if cells were plated at greater than 300,000 cells/dish. As there was no effect of conditioned medium from glucagon-sensitive cells on insensitive cells, media components seemed not to be involved in this phenomenon. Glucagon sensitivity appeared more readily in defined as opposed to serum-containing medium. In fact, as little as 2% fetal bovine serum inhibited the expression of glucagon sensitivity when included in defined medium over the course of the experiment. Furthermore, when transformed MDCK cells were exposed to serum for only the first 24 hr of culture, glucagon sensitivity on day 11 was identical to that of cells exposed to serum throughout the entire experiment. In contrast, exposure to serum later in culture (days 4-8) had no inhibitory effect on the expression of glucagon sensitivity on day 11. The data suggest that differentiation, or glucagon sensitivity, occurs when transformed, glucagon-insensitive cells achieve a critical high density and that differentiation is sensitive to inhibition by serum only during the first 24 hr of culture.

Animals↗
PubMed1984

Decreased adenylate cyclase responsiveness of transformed cells correlates with the presence of a viral transforming protein.

The adenylate cyclase responsiveness of transformed fibroblastic and epithelial cell lines to forskolin, fluoride, guanine nucleotides and cholera toxin was reduced compared to their parental counterparts. This phenomenon was observed in lines transformed by either RNA or DNA tumor viruses, and in the case of polyoma virus, coincided with the expression of middle T antigen. The data suggest that decreased responsiveness of adenylate cyclase to non-hormone activators is a general consequence of viral transformation and may be related to viral regulation of protein kinase activity.

Adenylyl Cyclases↗