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Biomedical subjects

P P Lin

Publications and source records attributed to P P Lin.

33 records · Page 2Linked to original sources
PubMed1988

Growth factors and hyperthermia. II. Viability of Chinese hamster ovary HA-1 cells during serum starvation and hyperthermia.

We tested the possibility that hyperthermia kills HA-1 cells in a manner analogous to growth factor deprivation. HA-1 cells were inactivated by serum starvation when incubated in Eagle's MEM at a density of 40 cells/cm2 or less. Cells became resistant to the absence of serum when the cell density was greater than 400 cells/cm2 or when lethally irradiated HA-1 feeder cells were present. The feeder cells exerted their effect through a diffusible factor. In addition, a 1:1 mixture of Eagle's MEM and Ham's F-12 enabled HA-1 cells to remain viable without serum. Ten days growth in Eagle's MEM + Ham's F-12 without serum resulted in the formation of microcolonies of cells. This indicated that growth factor deprivation was not lethal to HA-1 cells, and it suggested that they may have been partially transformed. The presence of the growth factors insulin, transferrin, and fibroblast growth factor (FGF) reduced cell killing by a small amount during conditions of serum starvation. After hyperthermia, the presence of growth factors again diminished cell killing by a modest amount (approximately twofold). Feeder cells also improved cell survival after hyperthermia. The effect of feeder cells was greatest when cells were trypsinized immediately after hyperthermia. When cells were not trypsinized after heating, feeder cells increased survival less than twofold. In summary, the absence of growth factors was not lethal to HA-1 cells, and therefore the cytotoxic effects of hyperthermia could not be explained fully by the failure to bind growth factors. HA-1 feeder cells secreted undefined, growth-promoting substances, but feeder cells exerted only a small positive effect on cell survival after hyperthermia when cells were not trypsinized after heating.

Animals↗
PubMed1988

Growth factors and hyperthermia. I. The relationship between hyperthermic cell killing and the mitogenic response to serum and growth factors.

Chinese hamster ovary HA-1 cells were tested for their ability to respond to mitogenic stimulation after hyperthermia at 45 degrees C. Cells were arrested by 24 h incubation in serum-free Eagle's MEM. Heating of arrested cells in serum-free medium did not alter heat sensitivity compared to exponentially growing cells heated in serum-containing medium. After hyperthermia cells exhibited a delay in the ability to undergo mitogenesis. Recovery of the capacity for mitogenesis occurred during the 24 h following heating and was able to take place in the absence of serum. After recovery in serum-free medium, cells were simultaneously assayed for survival and mitogenesis as measured by [3H]Thy uptake. With increasing heating time, surviving fraction and mitogenesis decreased. The reduction in survival was similar to the reduction in [3H]Thy incorporation. The relationship between mitogenesis and cell death was studied in more detail with flow cytometry. At a relatively mild heat dose of 30 min at 45 degrees C (survival = 30%), a small population of cells (9%) was found to be clonogenically dead yet capable of being stimulated to progress from G1 to G2-M. At a more severe heat dose of 40 min at 45 degrees C (survival = 3%), stimulation of dead cells could not be detected. Therefore, hyperthermia impairs mitogenic ability, but at low heat doses, a subpopulation of killed cells can still be stimulated to progress through the cell cycle.

Animals↗
PubMed1984

Polyamine metabolism and its relation to response of the aleurone layers of barley seeds to gibberellic Acid.

Polyamine metabolism and its relation to the induction of alpha-amylase formation in the aleurone layers of barley seeds (Hordeum vulgare cv Himalaya) in response to gibberellic acid (GA(3)) has been investigated. A high-performance liquid chromatographic system has been employed for qualitative and quantitative analyses of putrescine (Put), cadaverine (Cad), spermidine (Spd), spermine (Spm), and agmatine (Agm).Active polyamine metabolism occurs in the aleurone cells of deembryonate barley half seeds during imbibition. The aleurone layers isolated from fully imbibed half seeds contain about 880 nanomoles of Put, 920 nanomoles of Spd, and 610 nanomoles of Spm as free form per gram tissue dry weight while the levels of Cad and Agm are relatively low. The polyamine levels do not change significantly in the aleurone layers in response to added GA(3) (1.5 micromolar) during the 8-hour lag period of the growth substance-induced formation of alpha-amylase. Also, the polyamine levels are not altered by the presence of abscisic acid (3 micromolar) which inhibits the enzyme induction by GA(3). Kinetic studies show that both applied [U-(14)C]ornithine and [U-(14)C]arginine are primarily incorporated into Put during 2 hours of incubation, but the incorporation is not significantly affected by added GA(3). Additionally, added GA(3) does not affect the uptake and turnover of [1,4-(14)C]Put, nor does it affect the conversion of Put --> Spd or Spd --> Spm. Treatment of the aleurone layers with GA(3) for 2 hours results in no significant changes in the total activities or the specific activities of ornithine decarboxylase and arginine decarboxylase.Experiments with polyamine synthesis inhibitors demonstrate that the level of Spd in the aleurone layers could be substantially reduced by the presence of methylglyoxal-bis(guanylhydrazone) (MGBG) during imbibition. MGBG treatment does not affect in vivo incorporation of [8-(14)C] adenosine into ATP. The lower the level of Spd the less alpha-amylase formation is induced by added GA(3). The reduction of GA(3)-induced alpha-amylase formation by MGBG treatment can be either completely or partially overcome by added Spd, depending upon the concentration of MGBG used in the imbibition medium. The results indicate that the early action of GA(3), with respect to induction of alpha-amylase formation in barley aleurone layers, appears to be not on polyamine metabolism. However, polyamines, particularly Spd, may be involved in regulation of the growth substance-dependent enzyme induction.

Journal Article↗
PubMed1984

Polyamine Titer in the Embryonic Axis and Cotyledons of Glycine max (L.) during Seed Growth and Maturation.

Active polyamine metabolism occurs in Glycine max (L.) seeds during development. Most (>/=97%) of putrescine (Put), spermidine (Spd), spermine (Spm), and cadaverine (Cad) are present as free forms in the growing embryo. In the cotyledon or embryonic axis, Put decreases to a nearly undetectable level, while Spd level sharply increases as seed dry weight accumulation progresses. Spm level in the axis also increases along with the Spd level. There is little change in Spm level in the cotyledons. Maturation and dehydration results in a slight reduction of Spd level in the cotyledons. Cad is present in relatively large quantities (5.5-12 micromoles per gram dry weight) in the axes of mature soybean seeds. Only traces of Cad, as expressed on a dry weight basis, are found in the developing or mature cotyledons. The synthesis and accumulation of Cad in the axis begins at the time when the axis or the seed accumulates 30 to 50% of its maximum dry weight. The Cad accumulation (0.8 nanomole per axis per day) proceeds until the later stages of dehydration. When soybean plants are subjected to complete defoliation and shade during the midpoint of seed maturation, Cad accumulation in the axis and seed dry weight accumulation ceased almost immediately. The treatment, however, does not affect the viability of soybean seeds.

Journal Article↗
PubMed1984

Polyamine Anabolism in Germinating Glycine max (L.) Seeds : Dynamics of Cadaverine and Putrescine Formation in the Embryonic Axis.

Active polyamine biosynthesis occurs in the embryonic axis, but not in the cotyledons, during germination of Glycine max (L.) cv Williams seeds and subsequent growth of the young seedlings. The hypocotyl and radicle synthesize and accumulate considerable amounts of cadaverine (Cad) and putrescine (Put) during the early stages of growth. Most of the amino acid precursors for the diamines are supplied from breakdown of the cotyledonary protein.In the axis, Cad synthesis which is catalyzed by l-lysine decarboxylase precedes the onset of growth (dry weight accumulation) of the axis and its accumulation continues as the growth progresses. After 2 days of imbibition, Cad is synthesized and accumulated at 37.4 nanomoles per axis per hour for at least 6 days. The rate then gradually decreases as the supply of free l-lysine from the cotyledons diminishes. Approximately 40 to 50% of the lysine resulting from breakdown of the cotyledonary protein ends up in Cad in the hypocotyl and radicle. Cad represents about 3.5% of the axis nitrogen derived from the cotyledons, which is equivalent to about 50% of the lysine content ( approximately 7%) of the seed protein.The synthesis and accumulation of Put in the axis also precedes the onset of growth of the axis. Both l-arginine decarboxylase and l-ornithine decarboxylase are involved in catalyzing the Put formation. The increased content of spermidine (Spd), but not spermine (Spm), parallels growth of the axis. Spm is maintained at a nearly undetectable level. After 2-day imbibition, Put and Spd are synthesized and accumulated at 0.94 and 0.17 nanomoles per axis per hour, respectively. The rate of Put accumulation, like that of Cad, decreases about 8 days after imbibition. The hypocotyl and radicle contain millimolar concentrations of Cad and Put which are primarily associated with the elongated zones. In contrast, Spd level or the molar ratio of Spd:Put appears to decrease as cell differentiation or elongation progresses.

Journal Article↗
PubMed1980

Histone Kinase from Soybean Hypocotyls: PURIFICATION, PROPERTIES, AND SUBSTRATE SPECIFICITIES.

A histone-type protein kinase (EC 2.7.1.37) has been partially purified (320-fold) from the crude extracts of soybean hypocotyls by means of a combination of gel filtration and anion exchange procedures. The purified enzyme fraction is devoid of the activities of phosphoprotein phosphatase (EC 3.1.3.16), histone protease, and casein (or phosvitin)-type kinase. The soybean histone kinase uses ATP to phosphorylate specifically lysine-rich histone H1 from either pea seedlings or calf thymus.The histone kinase requires free sulfhydryl group(s) for activity, but not stability. The pH optimum is around 9 to 10. The apparent K(m) values for histone H1 of pea seedlings and calf thymus are 0.4 and 0.9 micromolar, respectively. The K(m) values for ATP are 40 nanomolar with the optimal concentration of Mn(2+) (50 nanomolar) and 0.4 micromolar with that of Mg(2+) (5 millimolar). The estimated molecular weight of the kinase is 52,000 by gel filtration or 48,600 by sedimentation constant (3.2 S). cAMP does not alter the sedimentation velocity of the kinase. The enzyme activity is unaffected by cyclic nucleoside monophosphates and plant growth substances. Like arginine-rich histones, a variety of divalent cations and polycations (polyamines) are inhibitory.This cAMP-independent soybean histone kinase is not associated with the isolated ribosomes but shows highest specific activity in the nuclearchromatin fraction, suggesting that it may function in the regulation of histone H1 phosphorylation in the soybean hypocotyl.

Journal Article↗
PubMed1980

Phosphoprotein Phosphatase of Soybean Hypocotyls: PURIFICATION, PROPERTIES, AND SUBSTRATE SPECIFICITIES .

A soybean histone-type protein kinase was used to prepare (32)P-labeled histone H1 as substrate for purification and characterization of a phosphoprotein phosphatase (EC 3.1.3.16) from soybean hypocotyls. The phosphatase has been purified 169-fold by ammonium sulfate fractionation, ethanol precipitation, and chromatography on Sephadex G-150, DEAE-Sephadex A-25 and Sephadex G-100. The activity of the phosphoprotein phosphatase is distinct from that of acid and alkaline phosphatases (EC 3.1.3.1) as well as from that of nucleotidases. The final enzyme preparation does not contain histone protease activity, although it can be detected during the early stages of purification. The protease(s) apparently can attack phosphorylated histone H1, indicating that phosphorylation does not protect the protein against proteolytic degradation.The amounts of (32)P released from [(32)P]histone H1 are proportionally recovered as [(32)P]Pi, indicating that the dephosphorylation is due to the action of phosphoprotein phosphatase. The enzyme shows maximal activity at pH 7 to 8 and has a specific activity of 19 nanomoles of [(32)P]Pi released from [(32)P]histone H1 per minute per milligram of protein. The apparent K(m) for phosphohistone H1 is 4.0 +/- 0.4 micromolar. The estimated molecular weight of the enzyme is approximately 30,000 by gel filtration. The enzyme activity does not depend upon the addition of reducing agent and metal ion. Zn(2+), Co(2+), NaF, pyrophosphate, or ATP at 1 millimolar, however, inhibits the enzyme activity by about 70%. The enzyme activity is unaffected by cyclic nucleotides and plant growth substances but is inhibited by polyamines. All the phosphorylated histone species and protamine, not low molecular weight phosphoesters, act as competitive inhibitors for the dephosphorylation of [(32)P]histone H1.Besides its action on phosphohistone H1, the soybean enzyme also catalyzes the dephosphorylation of other phosphohistone species (H2A, H2B, H3, and H4), degraded phosphohistone H1, and possibly phosphorylated casein and phosvitin. All these results indicate that the enzyme is a nonspecific phosphoprotein phosphatase.

Journal Article↗
PubMed1978

Dose reduction in mammography.

The Min-R system is more than a satisfactory substitute for xerography. At equal distances, the images obtained are equivalent. Radiation exposure was 25 per cent of xerography, a significant reduction in exposure. By using a long cone and improving geometry, superior images were obtained in 4 per cent of 400 comparison patients. If mammography is to be used as an early detection device in patients with carcinoma of the breast, modalities with lower exposure requirements must be used. Min-R, a new film screen system, fulfills the requirement of reduced patient exposure without loss of diagnostic accuracy.

Female↗
PubMed1976

Studies on morphological characteristics of Japanese strain of Schistosoma japonicum in rabbits.

The present investigation was undertaken to determine some morphological characteristics of Japanese strain of Schistosoma japonicum, the results are summarized as follows: (1) The pattern of testes in male worms can be divided into two types: the tandem (37.6%) and non-tandem (62.4%). (2) The number of testes varied from 1 to 13. The percentage of specimens with 7 testes was much higher than of others with both in tandem (70% against 30%) and non-tandem (86% against 14%) arrangement. (3) The unusual/irregular sets of testes including 2-3 additional sets were found in 158 (or 4.5%) of 3,498 male worms. Specimens with 7 testes in the unusual/irregular location numbered the highest (69.6%); the next with 8 (14.6%) and 6 (12%); and the lowest with 5 (3.8%). (4) Forty or 2.8% of 1,417 male worms were found to have 2-4 cecal loops. The cecal union located in 71-80% of worm bodys from the anterior end of male worm was found in highest number; the next in 61-70%; and the lowest in 51-60% and 81-90%. The location of united ceca in female worms was found all in the posterior part of body. (5) The ovary in all 125 females was located in the posterior portion of worm body except in 4 specimens. (6) The number of eggs in the uterus of female worms varied from 50 to 300. The mean number was 103.

Animals↗
PubMedDate not supplied

Dose reduction in mammography.

Two mammographic imaging systems (Xerox and Kodak Min-R) were evaluated. Three hundred consecutive mammographic examinations were performed utilizing both imaging systems. Results of these studies indicated equivalency of image detail at identical source-to-image receptor distance (SID). Patient exposure as measured by the thermoluminescent dose meter for Kodak Min-R system was approximately 25% that of Xeromammography system. Due to reduced power requirement, it is possible to increase the SID when Min-R system is employed for imaging. Improved geometric arrangement provided superior diagnostic images in 5.5% of 200 comparison cases.

Female↗