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Biomedical subjects

E W Gerner

Publications and source records attributed to E W Gerner.

At least 109 records · Page 6Linked to original sources
PubMed1977

Cytoplasmic and nuclear protein kinases during the cell cycle.

Nuclear and cytoplasmic protein kinases were measured during the traverse of synchronous CHO cultures through G1 into S phase. Cells were synchronized by selective detachment of cells blocked in metaphase using colcemid. Nuclei were isolated and the protein kinases extracted from the nuclear preparation with 0.6 M NaCl. This procedure solubilized greater than 90% of the total protein kinase activity present in the nuclear preparation. DEAE chromatography of this extract showed 5 apparently different ionic forms of nuclear protein kinases. The nuclear protein kinases preferred casein and phosvitin to histone as substrates and were cyclic AMP-independent. Nuclear protein kinase activities increased greater than two-fold, when expressed as units of activity per cell nucleus, during G1 phase traverse, concomitant with a 70% increase in nuclear non-histone proteins (those soluble in 0.6 M NaCl). This resulted in only a 40% increase in the specific activities (units/microgram protein in 0.6 M NaCl extractable nuclear fraction) of these enzymes as cells progressed through G1 into S phase. This was in contrast to cytoplasmic cyclic AMP-dependent protein kinase activities which also increased two-fold during progression through G1 phase while total cellular protein increased less than 20%. Activation of, as well as synthesis of, cyclic AMP-dependent cytoplasmic protein kinases during G1 phase suggests a regulatory mechanism for precise temporal phosphorylation, whereas the constant specific activity in nuclear kinases during cell cycle is more compatible with the maintenance of bulk phosphorylation processes in the nucleus.

Cell Cycle↗
PubMed1977

Hyperthermic potentiation: biological aspects and applications to radiation therapy.

Experimental studies have provided evidence that hyperthermia may be an effective agent, either alone or in combination with ionizing radiation, in the treatment of cancer. Results have shown that temperatures in the range of 42 degrees to 45 degrees C: 1) are cytotoxic, with cell lethality showing little or no dependence on levels of oxygenation; 2) inhibit the recovery of cells from sub-lethal and potentially lethal radiation damage while enhancing the levels of lethal damage; and 3) may be combined with x-irradiation in a manner to improve therapeutic ratios. The observed interaction between hyperthermia and x-rays may in part be due to differences in the Age Response Functions and reassortment of cycling cells to these two agents. Hyperthermia may also greatly change repopulation and re-oxygenation parameters in irradiated tumor and normal tissue volumes. An overall consideration of these and other factors is essential in the design of optimal schedules of combined hyperthermia and x-irradiation treatments in the management of malignant disease.

Animals↗
PubMed1977

Prospects for hyperthermia in human cancer therapy. Part II: implications of biological and physical data for applications of hyperthermia to man.

Laboratory data from studies of hyperthermia as a potential antitumor agent indicate that: (a) tumor cells may be more sensitive to heat than normal tissue; (b) hyperthermia enhances response to irradiation and can increase the therapeutic ratio; (c) cells are most sensitive to hyperthermia during the S-phase, when they are resistant to ionizing radiations; (d) the oxygen effect is absent for hyperthermic cell killing, and radiation effects are less oxygen-dependent when potentiated by heat treatment; and (e) biological damage changes more rapidly at temperatures above 43 degrees C. Methods of heat production and dosimetry need to be refined further before these findings can be put to practical use in tumor therapy.

Animals↗
PubMed1977

The relationship between polyamine accumulation and DNA replication in synchronized Chinese hamster ovary cells after heat shock.

The relationship of polyamine accumulation and semiconservative DNA replication was studied in synchronous Chinese hamster ovary cultures, progressing through the cell cycle either normally at 37 degrees or after hyperthermic exposure (43 degrees for 1 hr) during G1 or S phase. In control cultures, intracellular polyamine levels decreased as cells divided and then reaccumulated as cells exited G1 and proceeded through the S and G2 phases. Immediately after cultures were exposed to 43 degrees heat for 1 hr in G1 phase, intracellular levels of spermidine and spermine were reduced compared to controls. Coordinate with the depletion of the intracellular levels of these polyamines following exposure at 43 degrees, extracellular levels of spermidine and spermine were increased. The ratio of intracellular to extracellular amounts of both these polyamines changed from 1 to 1.5 to approximately 0.2 to 0.3 after hyperthermic exposure. These cultures exposed to 43 degrees heat during G1 initially showed depressed levels of replicated DNA, but near-control rates of DNA replication were atained in a temporally related manner with the reaccumulation of intracellular spermidine and spermine levels. When cultures were exposed to 43 degrees heat in S phase, intracellular amounts of spermidine and spermine were again reduced and increased extracellular levels of these polyamines were observed. In these S-phase-treated cultures, cells were able to continue replicating their DNA but at a much reduced rate compared to controls. These results and other show that: (a) exposure of cells at 43 degrees causes a depletion of intracellular levels of spermidine and spermine, suggesting that an immediate aspect of thermal damage is a membrane defect that markedly affects the transport of these molecules across cell membranes; (b) exposure of either G1- or S-phase cultures to 43 degrees heat caused a depression of bulk DNA-synthetic rates resulting in a prolongation of S phase, and (c) the intracellular reaccumulation of spermidine and spermine following exposure of G1 cells to a 43 degrees heat shock is temporally related to the recovery of near-normal DNA synthetic rates in these cells.

Biological Transport↗
PubMed1976

Cell cycle-specific activity of type I and type II cyclic adenosine 3':5'-monophosphate-dependent protein kinases in Chinese hamster ovary cells.

Types I and II cyclic adenosine 3':5'-monophosphate (cAMP)-dependent protein kinases have been studied during the cell cycle of Chinese hamster ovary cells. Chinese hamster ovary cells were synchronized by selective detachment of mitotic cells from monolayer cultures. Protein kinases were separated by DEAE-cellulose chromatography and were similar to the types of cAMP-dependent protein kinases studied in skeletal muscle and in heart extracts. The total amount of protein kinases activity per cell was substantial, both in mitosis and at the G1/S boundary. During mitosis, the relatively high activity of protein kinase was due to a predominance of type I protein kinase. During early G1, the activity of type I protein kinase decreased and there was little detectable type II activity. A rapid increase in the activity of type II was evident at the G1/S boundary. The administration of puromycin (50 mug/ml) from 1 to 5 hours after selective detachment of mitotic cells abolished the activity of type II cAMP-dependent protein kinase seen at the G1/S border, but had no observable effect on the activity of type I protein kinase. The data presented demonstrate cell cycle-specific activity patterns of type I and type II protein kinase Type I protein kinase activity is high in mitosis and is constant throughout the cell cycle. Increased type II protein kinase activity seems to be related to the initiation of DNA synthesis in S phase. The data suggest a translational control of type II cAMP-dependent protein kinase activity.

Cell Division↗
PubMed1976

G1 specific increases in cyclic AMP levels and protein kinase activity in Chinese hamster ovary cells.

Chinese hamster ovary cells were synchronized by selective detachment of cells in mitosis. The adenosine 3':5'-cyclic monophosphate (cyclic AMP) intracellular concentrations and cyclic AMP-dependent protein kinase activities were measured as these cells traversed G1 phase and entered S phase. Protein kinase activity, assayed in the presence or absence of saturating exogenous cyclic AMP in the reaction mixture, was lowest in early G1 phase (2 h after mitosis), increased 2-fold (plus exogenous cyclic AMP in reaction mixture) or 3.5-fold (minus cyclic AMP in reaction mixture) to maximum values in mid to late G1 phase (4-5 h after mitosis), and then decreased as cells entered S phase. Intracellular cyclic AMP concentrations were minimal 1 h after mitosis, increased 5-fold to maximum levels at 4-6 after mitosis, and decreased as cells entered S phase. Similar to the fluctuations in intracellular cyclic AMP, the cyclic AMP-dependent protein kinase activity ratio increased more than 40% in late G1 or early S phase. Puromycin (either 10 mug/ml or 50 mug/ml) administered 1 h after mitosis inhibited cyclic AMP-dependent protein kinase activity up to 50% by 5 h after mitosis, while similar treatment (10 mug/ml) had no effect on the increase in cyclic AMP formation. These data demonstrate that: (1) total protein kinase activity changed during G1 phase and this increase was dependent on new protein synthesis; (2) the increased intracellular concentrations of cyclic AMP were not dependent on new protein synthesis; and (3) the activation of cyclic AMP-dependent protein kinase was temporally coordinated with increased intracellular concentration of cycli AMP as Chinese hamster ovary cells traversed G1 phase and entered S phase. These results suggest that cyclic AMP acts during G1 phase to regulate the activation of cyclic AMP-dependent protein kinase.

Cell Line↗
PubMed1976

Non-histone protein synthesis during G1 phase and its relation to DNA replication.

The kinetics of non-histone chromosomal protein (NHCP) synthesis were studied in Chinese hamster ovary (CHO) plateau phase cells stimulated to proliferate and were compared to NHCP synthesis kinetics in two populations of synchronous G1 traversing cells. In all cases, NHCP synthesis rates increase 3- to 5-fold as cells traversed G1 and attained maximum values one hour before semi-conservative DNA replication began. Similar to results in synchronous G1 cells, the molecular weight distributions of the NHCP fraction from stimulated plateau phase cells underwent only minor changes, measured by sodium dodecylsulfate (SDS) polyacrylamide gel electrophoresis, as these cells moved toward S phase. Yet, during this progression after plateau phase and in the transition from early G1 to late G1 in synchronous cells, the total NHCP fraction increased significantly (1.5-2-fold) in amount per cell. These data indicate that plateau phase cells are similar to early G1 cells both in terms of their amounts of non-histone per cell and in their subsequent NHCP synthesis kinetics as they move toward S phase. These results extend previous findings which suggested that NHCP synthesis was coupled to DNA replication and demonstrate that the increased NHCP synthesis and accumulation in chromatin may be a biochemical marker for G1 progression.

Cell Division↗
PubMed1976

Mammalian cell survival response following irradiation with 4 MeV X rays or accelerated helium ions combined with hyperthermia.

The effects of hyperthermia on Chinese hamster ovary cell radioresponse were studied using either 4 MeV x rays or accelerated helium ions. Both pre-and postirradiation hyperthermic doses act to decrease the slope of the x-irradiation survival curve in a temperature-dependent manner, while the extrapolation number does not change appreciably. Pre-irradiation hyperthermic treatment has only a slightly greater dose-modifying effect than similar postirradiation hyperthermia. For cells irradiated with helium, pre-irradiation at 43 degrees C (1 hr.) changes the radiation survival curve slope and also the extrapolation number, implying that hyperthermia may act more readily to enhance lethal x-ray damage than lethal helium damage, while having a similar effect on the accumulation of sublethal damage for both of these radiations.

Animals↗
PubMed1976

A transient thermotolerant survival response produced by single thermal doses in HeLa cells.

Continuous exposure of HeLa cells in culture to elevated temperatures (41-45 degrees) results in cell killing which increases exponentially as the time at the elevated temperature increases linearly. When cells are returned to 37 degrees after an initial thermal dose, cellular sensitivity to subsequent hyperthermic doses is reduced. Cell inactivation rates for cultures previously treated with 44 degrees for either 0.5 or 1 hr followed by incubation at 37 degrees for 2 hr, showed D0's of 1.1 and 1.5 hr, respectively, for subsequent thermal treatments at 44 degrees. Cultures receiving no prior hyperthermic dose had a D0 of 0.5 hr for treatments at 44 degrees for up to 3.5 hr. The viable progeny of cells treated with 44 degrees for 1 hr, however, had the same sensitivity to thermal doses at 44 degrees as did previously unheated cells. These results and others demonstrate that (a) single thermal dose produce a state of thermotolerance in HeLa cells to subsequent hyperthermic doses; (b) the degree of thermotolerance produced is dependent on the magnitude (i.e., temperature and time at the elevated temperature) of the first thermal dose; (cy thermotolerance does not develop at the elevated temperature but requires a return of culture temperatures to 37 degrees; (d) cellular acquisition of thermal tolerance is dependent on cell metabolism, as demonstrated by an inhibition of the effect at 0 degrees; and (e) this effect is a transient phenomenon which is lost as cells divide following the first thermal dose.

Cell Division↗
PubMed1975

Ross' syndrome (tonic pupil plus).

Two cases of tonic pupil, hyporeflexia, and segmental hypohidrosis (Ross' syndrome) are reported. The relationship of this syndrome to other autonomic dysfunction is discussed. Those symptoms (emotional instability, loss of sweating, orthostatic hypotensive symptoms, and signs of bilaterality of the tonic pupil) which should alert the clinician to more extensive disease states are noted. It is suggested that these conditions may represent a continuum or spectrum of disorders with a widespread degree of severity and progression.

Adie Syndrome↗
PubMed1975

The potential of localized heating as a adjunct to radiation therapy.

Experimental studies have shown that (a) tumor cells may be more sensitive to heat than normal cells; (b) hyperthermia inactivates cellular repair mechanisms for radiation damage; and (c) heat may lower the OER for ionizing radiation (anoxic cells are at least as sensitive to hyperthermia as oxygenated cells). Localized hyperthemia produced by localized current fields in the range of 100 kHz-10 MHz by direct contact electrodes offers two major advantages: the eletrode configurations may be manipulated to obtain desired thermal dose distributions, and, since the mode of heating is essentially instantaneous, accurate temperature control can be maintained during treatment.

Adolescent↗