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Biomedical subjects

H Rubin

Publications and source records attributed to H Rubin.

At least 145 records · Page 8Linked to original sources
PubMed1989

Reaction of human skin chymotrypsin-like proteinase chymase with plasma proteinase inhibitors.

The ability of plasma proteinase inhibitors to inactivate human chymase, a chymotrypsin-like proteinase stored within mast cell secretory granules, was investigated. Incubation with plasma resulted in over 80% inhibition of chymase hydrolytic activity for small substrates, suggesting that inhibitors other than alpha 2-macroglobulin were primarily responsible for chymase inactivation. Depletion of specific inhibitors from plasma by immunoadsorption using antisera against individual inhibitors established that alpha 1-antichymotrypsin (alpha 1-AC) and alpha 1-proteinase inhibitor (alpha 1-PI) were responsible for the inactivation. Characterization of the reaction between chymase and each inhibitor demonstrated in both cases the presence of two concurrent reactions proceeding at fixed relative rates. One reaction, which led to inhibitor inactivation, was about 3.5 and 4.0-fold faster than the other, which led to chymase inactivation. This was demonstrated in linear titrations of proteinase activity which exhibited endpoint stoichiometries of 4.5 (alpha 1-AC) and 5.0 (alpha 1-PI) instead of unity, and SDS gels of reaction products which exhibited a banding pattern indicative of both an SDS-stable proteinase-inhibitor complex and two lower Mr inhibitor degradation products which appear to have formed by hydrolysis within the reactive loop of each inhibitor. At inhibitor concentrations approaching those in plasma where inhibitor to chymase concentration ratios were in far excess of 4.5 and 5.0, the rate of chymase inactivation by both serpin inhibitors appeared to follow pseudo-first order kinetics. The "apparent" second order rate constants of inactivation determined from these data were about 3000-fold lower than the rate constants reported for human neutrophil cathepsin G and elastase with alpha 1-AC and alpha 1-PI, respectively. This suggests that chymase would be inhibited about 650-fold more slowly than these proteinases when released into plasma. These studies demonstrate that although chymase is inactivated by serpin inhibitors of plasma, both inhibitors are better substrates for the proteinase than they are inhibitors. This finding along with the slow rates of inactivation indicates that regulation of human chymase activity may not be a primary function of plasma.

Chymases↗
PubMed1989

Evidence for the progressive and adaptive nature of spontaneous transformation in the NIH 3T3 cell line.

The NIH 3T3 mouse cell line is widely used as a recipient of DNA from tumors to demonstrate the presence of transforming oncogenes. We show that these cells produce transformed foci spontaneously if kept in the confluent state for more than 10 days. The formation of foci depends on the type and concentration of bovine serum used in the medium and passage history of the cells. Cells maintained in continuous exponential multiplication in the subconfluent state by transfer every 2-3 days in medium with 10% calf serum failed to develop the capacity to produce foci in 2% calf serum, but those transferred the same way in 2% calf serum or in 10% fetal bovine serum, which is a less potent growth stimulant, did develop that capacity to an increasing degree over time. The number of transformed cells increased sharply with the time that a culture remained in the confluent state. There are several morphological types and degrees of transformation, which indicates that the underlying changes are varied and the process is progressive. The results also suggest that transformation occurs in a fraction of an entire cell population that is undergoing a physiological adaptation to moderate constraints on its growth.

Animals↗
PubMed1989

Vesicular Jarisch-Herxheimer reaction.

The Jarisch-Herxheimer reaction is a self-limited, febrile episode that may occur following antibiotic therapy for syphilis. We report four cases of a heretofore unrecognized vesicular variant of the Jarisch-Herxheimer reaction. It is important to distinguish this phenomenon from an allergic drug eruption.

Adult↗
PubMed1989

Cerebellar tumor causing hypertensive crisis and simulating pheochromocytoma and Cushing's syndrome.

We describe a case of posterior fossa medulloblastoma in which the initial symptom was severe hypertension that evolved into a hypertensive crisis. Initial diagnostic evaluation was suggestive of both pheochromocytoma and Cushing's syndrome: elevated plasma norepinephrine and urine VMA, normal ACTH level with elevated plasma and urine cortisol, and lack of suppressibility with dexamethasone. CAT scan and cerebral angiogram subsequently revealed the presence of an intracranial mass. After surgical removal of the tumor, blood pressure pattern and endocrine abnormalities reverted to normal.

Adrenal Gland Neoplasms↗
PubMed1988

Etiology of AIDS.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Uniqueness of each spontaneous transformant from a clone of BALB/c 3T3 cells.

Seeding 2 X 10(4) cells from a clone of BALB/c 3T3 cells in agar led to the formation of about 100 small colonies (approximate diameter, 0.2 mm) and two large colonies (1-mm diameter). Seven of the former and both of the latter were isolated, and the morphology and growth properties of their cells were observed in repeated weekly passages. The seven subclones derived from the smaller agar colonies spread out on the dish and multiplied more slowly than the parental clone on plastic, but six of them produced more colonies in agar than the parental clone. The two subclones derived from the larger agar colonies had a fully transformed morphology, multiplied much faster than the parental clone on plastic, and produced a high percentage of large colonies in agar. Each of the subclones could be distinguished morphologically from the others and from the parental clone, and most of them could be distinguished on the basis of their colony-forming efficiency in agar. Most of the secondary subclones derived from an early passage on plastic of one of the two large agar clones, died out on the second passage after their isolation. Secondary subclones derived from the same subclone five weeks later had a wide range of fluctuating growth rates, but did not die out on passage. The two rapidly growing subclones derived from large agar colonies initiated fast-growing tumors in nude mice. None of the other subclones produced any visible growth in nude mice over a 3-month period. Large agar colonies of fast growing, morphologically transformed cells appeared once during further passage of the parental clone and two of the subclones. The results reveal a surprising degree of heritable diversity in morphology and growth characteristics of the progeny from a clonal line of nontransformed cells. They also indicate that, in this cell line, only those cells that have a high efficiency (greater than 20%) of large colony formation in agar have the capacity to form tumors in nude mice.

Agar↗
PubMed1988

Quantitative studies of amino acid and growth factor requirements of transformed and nontransformed cells in high concentrations of serum or lymph.

The growth rate of spontaneously transformed BALB/3T3 cells is proportional to glutamine concentration between 50 and 400 microM, with little or no growth occurring in less than 50 microM glutamine. By contrast, nontransformed BALB/3T3 cells multiply, although slowly, with as little as 20 microM glutamine. Neither cell type depletes the medium of glutamine at the low concentrations. Cystine requirements of both cell types increase with serum concentration, probably due to the binding of half-cystine residues by the serum. Calf serum is a much more potent stimulator of cell multiplication than calf lymph, especially for the nontransformed cells. The rate of cell multiplication can be reduced by lowering the concentration of essential amino acids to the physiologic level found in body fluids, but the growth limitations can be fully compensated by simply raising the serum concentration. Growth factors may act by enhancing the utilization of amino acids, particularly of glutamine which is a required substrate for the first and chief regulatory steps of purine and pyrimidine synthesis. Lymph, which is coextensive with interstitial fluid in vivo, is poor in growth factors for the nontransformed BALB/3T3 cells as well as for recently explanted mouse embryo cells, which raises questions of how normal cell growth is maintained in the body.

Amino Acids↗
PubMed1988

Direct wet mounts versus concentration for routine parasitological examination: are both necessary?

The authors evaluated the usefulness of direct wet mount microscopic examination of stool samples for routine parasitologic diagnosis compared with formalin-ethyl acetate concentration detection. Over a three-year period, there were no instances in which an intestinal parasite was detected only by the direct wet mount examination. Elimination of routine direct wet mount examinations can reduce laboratory cost and save significant technologist time without decreasing the sensitivity of microscopic examinations for common parasitic agents.

Costs and Cost Analysis↗
PubMed1988

Maintenance of multiplication rate stability by cell populations in the face of heterogeneity among individual cells.

We addressed the question of how a population of cells can maintain a constant multiplication rate given the heterogeneity of its individual members. Using the NIH 3T3 line of mouse embryo cells, comparisons were made of multiplication rates between offspring subclones and the parental clones from which the subclones were derived. Parents at all levels of multiplication rate produced offspring with a wide range of multiplication rates. Offspring from parent cells with the highest growth rates rarely exceeded their parents in rate of multiplication. Offspring from slow-growing parents, however, often exceeded the parents. It is concluded that the multiplication of NIH 3T3 populations represents constant diversification in multiplication rate: heterogeneous parents producing heterogeneous offspring. Population growth rates can remain stable because the fastest-growing parents generally produce offspring that multiply slower than the parents while the slowest parents often produce offspring that multiply faster than the parents.

Animals↗
PubMed1987

Use of lymph in cell culture to model hormonal and nutritional constraints on tumor growth in vivo.

Transformed BALB/3T3 cells, which proliferate without restraint in culture, consistently produce rapidly growing sarcomas when 10(5) or more cells are inoculated into nude mice but produce sarcomas, of widely varying latent periods and growth rates, or negatives when 10(4) or fewer cells are inoculated. In an attempt to simulate the in vivo constraints on tumor development, these cells were cultured on plastic surfaces in concentrations of lymph up to 100%. Calf lymph was less effective in supporting multiplication than calf serum at all concentrations up to about 50%. The rate of cell multiplication progressively decreased with increasing concentrations of both fluids above 50%. Nonetheless, rapid multiplication could be achieved even in 100% serum or lymph by supplementing them with the high concentrations of nutrients used in the synthetic medium MCDB 402. Supplementation of cystine and glutamine was essential for the growth-enhancing effects of the other nutrients. When the cells were suspended in agar, lymph was much less effective than serum in promoting colony formation even when both were supplemented with cystine and glutamine, or with all the constituents of the synthetic medium. We conclude that part of the low efficiency of tumor production and reduced growth rate of the transformed cells in mice resulted from a combination of (a) the paucity of growth factors in interstitial fluid, (b) the marked reduction in concentration of essential amino acids encountered by the cells in passing from culture into mice, and (c) the fact that cells multiplying in s.c. space do so without benefit of attachment to a solid substratum. Other factors, such as the growth inhibiting effects of direct contact with quiescent muscle and connective tissue cells, remain to be evaluated.

Amino Acids↗
PubMed1987

Selection and adaptation for rapid growth in culture of cells from delayed sarcomas in nude mice.

More than 1000 cells of a spontaneously transformed line of BALB/3T3 cells are required to initiate tumors in half the nude mice inoculated s.c., although the cells clone with an efficiency approaching 100% in culture. The cells of two tumors with prolonged latent periods, initiated by 2 X 10(4) and 5 X 10(3) cells, were chosen for detailed clonal analysis in culture. The cells from the tumors grew very poorly in culture in the first passages, but with increasing speed and efficiency in later passages. Cells derived directly from the two tumors cloned in agar with an efficiency of 0.01 and 0.002%. The growth rates on plastic of the rare successful clones derived from agar were generally low but extremely varied. Some clones lost the capacity for multiplication in a few passages, while others persisted but fluctuated unpredictably in growth rate in the early passages. The graded increase in growth rate of the uncloned tumor cell populations was probably the result of selection of the more rapidly growing clones. One of the slower-growing clones was subcloned. About half of the subclones grew at a slower rate than the parental clone. These, however, increased progressively in growth rate over six successive weekly passages, suggesting the occurrence of a gradual physiological adaptation. We conclude that selection of fast-growing clones contributes a major part of the gradually improving growth of tumor cell populations in culture, but that a physiological adaptation extending over many cell generations makes a significant contribution. The mechanism in either case is unknown, and indeed there may not be a unique mechanism in the scientifically rigorous sense.

Animals↗
PubMed1987

The sources of heritable variation in cellular growth capacities.

Diverse genetic and epigenetic changes occur in cells in response to unfavorable environments. Most of these changes do not directly cause the malignant transformation. An occasional, rare change can lead to cancer, although it may be expressed only in the environmental context that gave rise to it. The variety of such changes is so enormous that it is impossible to derive unique, cellular mechanisms. A set of rules is derived for describing the interactions between cell and its surround which result in malignancy. It has often been said that 'nature is simple'--illusion! It is our mind which looks for simplicity to avoid effort. L. Brillouin, Scientific Uncertainty and Information 1964.

Adaptation, Physiological↗
PubMed1986

Perturbation of red cell membrane structure during intracellular maturation of Plasmodium falciparum.

An experimental approach, which in this study was applied to the malarial system, can be used to analyze the molecular structure and organization of individual phospholipids in a wide variety of biological membranes. Electron spin resonance spectroscopy was used to investigate the structural modifications of the major red cell phospholipids that occur in erythrocyte membranes infected with the human malarial parasite, Plasmodium falciparum. These modifications were correlated with the intracellular developmental stage of the parasite. Phosphatidylcholine, phosphatidylethanolamine, and phosphatidylserine were increasingly disordered (fluidized) as infection progressed. This disordering occurred at different rates and to varying extents.

Animals↗
PubMed1986

Tumor progression in nude mice and its representation in cell culture.

Varying dilutions containing from 10(6) to 10(3) spontaneously transformed Balb/3T3 cells were inoculated into nude mice [N:NIH(S)II]. Less than half the mice inoculated with 10(3) cells developed tumors. The higher concentrations of cells produced visible tumors in all mice within 2-3 weeks, and these tumors grew rapidly to large sizes. Some tumors initiated by the lower concentrations of cells arose quickly, but others were greatly delayed in onset, then grew slowly, if at all, for several weeks before a rapid acceleration. The delayed acceleration can be considered a form of tumor progression. When first explanted into culture, cells from the early tumors multiplied somewhat more slowly than the parental cells that initiated the tumors, but narrowed the gap in a few weekly passages. By contrast, only a small fraction (less than or equal to 0.001) of cells from the longest delayed tumors could sustain multiplication in culture, although flow cytometry revealed them to have been a rapidly multiplying population when explanted. A relatively large fraction of these explanted tumor cells incorporated a 1-hour pulse of [3H]thymidine into DNA, although at a low rate. The shift to culture apparently slowed progress through the S-period of the cell cycle. The multiplication rate of cell populations from the delayed tumors increased in successive passages in culture. There was great heterogeneity in growth capacity among clones of the tumor cells. The growth rates of some clones declined to the point of extinction, those of others remained constant for several weeks, while those of still others steadily increased in growth rate. The low initial cloning efficiency of cells from the delayed tumors and the heterogeneity of growth rates among the clonable cells indicate that selection plays a major role in the increase of the growth capacity of the cell population. The steady increase in growth rates within clones suggests that physiological adaptation also contributes to the progressive growth of the tumor populations in culture. The results constitute a rationale for using the progressive growth of cells in culture as a model system for discriminating the types of cellular changes that underlie tumor progression.

Animals↗