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Biomedical subjects

H Rubin

Publications and source records attributed to H Rubin.

At least 19 recordsLinked to original sources
PubMed2005

Walter Elsasser, prophet of biological complexity, seeker of simplifying rules.

Walter Elsasser was an eminent theoretical physicist who devoted much of his spare time for over half a century (approximately 1935-1987) to the development of a holistic theory of organisms. The three basic principles of his biological theory are a) order in the large which dominates heterogeneity in the small; b) creative selection of the relatively small number of cells and organisms in nature as compared with the immense number of potential molecular states allowed by quantum mechanics, based on the number of atoms, molecules and chemical bonds in a cell, and c) holistic memory in reproduction of cells and organisms, a process which is supplementary to, and fundamentally different in type from the information stored in DNA. His ideas have either been coolly received or ignored by biologists, at least partly because of their purely formal character, although that is considered the sine qua non for theories in physical science. I cite a variety of experiments at the cellular level that illustrate his principles. Those experiments add a concrete dimension to his abstractions that hopefully will promote a dialog between theory and practice to facilitate development of a non-reductionist biology.

Animals↗
PubMed2005

The membrane, magnesium, mitosis (MMM) model of cell proliferation control.

The proliferation of cells in culture requires the presence of growth factors in the medium, provided either by serum or purified proteins. Cells are made quiescent by contact inhibition and sharply diminishing the concentration of growth factors overnight; they are then stimulated by restoring the original high concentration of the growth factors. The addition activates a coordinated group of biochemical responses within minutes, that is followed in 5-12 hr by the onset of DNA synthesis and then mitosis. The most critical of the early responses for the later onset of DNA synthesis is an increase in the rate of protein synthesis, which must be maintained by the continued presence of the growth factors throughout the G1 period. Lowering the Mg2+ concentration of the medium and therefore within the cells, reduces all the early reactions of the coordinate response including protein synthesis, which is followed by a disproportionately large reduction in the rate of DNA synthesis. Stimulation in the presence of physiological concentration of Mg2+ raises the total Mg and the free Mg2+ of the cells for extended periods. Mg2+ in the form of MgATP2- is required for all the phosphorylation reactions of the cell. These and related observations are imaged in the membrane, magnesium, mitosis (MMM) model of cell proliferation control, which postulates that growth factors act by combining with membrane receptors to increase intracellular free Mg2+ levels and generate the coordinate response that leads ultimately to mitosis. The MMM model also proposes that the increased Mg2+ activates phosphorylation of two proteins by mTOR, a key reaction of the PI-3K pathway. Those two proteins directly regulate the initiation of protein synthesis, the driving force of the process.

Cell Membrane↗
PubMed2004

Neuropsychological assessment of patients with late onset GM2 gangliosidosis.

OBJECTIVE: To characterize cognitive status in a sample of individuals with late-onset GM2 gangliosidosis (commonly referred to as late-onset Tay-Sachs disease). METHODS: Seventeen subjects (13 men, 4 women) diagnosed with GM2 gangliosidosis were evaluated. Subjects ranged in age from 18 to 56 years and were in various stages of disease progression. Subjects underwent comprehensive neuropsychological assessment. Impairment was defined as performance more than 1.6 SD below the normative mean. RESULTS: Group mean performance was within the denoted normal range on all measures except on a task assessing visual sequencing and set shifting. Approximately one-half of the sample scored in the impaired range on measures of processing speed, visual sequencing, and set shifting. One-third of the sample also scored in the impaired range on measures of delayed verbal recall. Impairment tended to be restricted to a subset of the sample, as 5 of the 14 subjects able to undergo formal testing accounted for 70% of the total number of impaired scores. If the three subjects unable to participate in formal testing are also considered impaired, 47% of the current sample exhibited significant cognitive impairment in at least one cognitive domain. CONCLUSION: In late-onset GM2 gangliosidosis, there is a risk of impairment in executive functioning and memory as well as cerebellar dysfunction. Dementia was not present in any subjects in the current sample.

Adolescent↗
PubMed2001

Selected cell and selective microenvironment in neoplastic development.

Recent analysis of genetic alterations in human cancer points to a major role for selection in neoplastic development but provides few details about the dynamics of the process. Many such details, however, have emerged from quantitative studies of spontaneous transformation among mammalian cells in culture. The chief insight of these studies is that there is a continuous generation of variants in proliferative potential among growing cells that provides the substratum for progressive development to a frankly neoplastic state when selective growth conditions are persistently applied. Much of the selection occurs before the cells are capable of producing discrete neoplastic foci. The varied observations in cell culture draw attention to analogous features of carcinogenesis in experimental animals and the development of human cancer.

Animals↗
PubMed2001

The role of selection in progressive neoplastic transformation.

Mathematical modeling indicates that selective growth of cells with biallelic mutations in tumor suppressor genes is the driving force in the development of most human tumors, and that increased mutation rate is not required. Spontaneous neoplastic transformation of cells in culture offers the opportunity for quantitative analysis of all stages of neoplastic progression, the cellular variation that underlies it, and the selective conditions that promote it. Most of the early work on spontaneous transformation was done in primary cultures of mouse embryo cells, but established mouse cell lines have been used more in recent years. The main criteria for transformation have been tumorigenesis in mice, increase in saturation density, and production of discrete, multilayered foci in confluent cell cultures. Spontaneous transformation in NIH 3T3 mouse fibroblasts is efficiently evoked by progressive selection under prolonged contact inhibition at high population density or during multiplication at low population density in suboptimal concentrations or types of serum. In general, it is a multistep process with some stages of progression occurring before there is any visible sign of transformed foci. There is a high degree of heritable heterogeneity in the original NIH 3T3 cell population for susceptibility to transformation. Isolation and expansion of minority susceptible clones from a relatively refractory population exhibit transformation long before the polyclonal parental population does because of the increased proportion of susceptible cells in these clones. There are indications that the selective conditions induce selectable variants. Tumor development in animals and man shares important characteristics with spontaneous transformation in culture, including a major role for selection, but the selective conditions for clonal expansion probably vary with the dynamics of differentiation in each tissue. These considerations support a role for an altered microenvironment (as in the aging process) in selective growth of rogue clones.

Animals↗
PubMed2001

Feasibility of in situ NAPL-contaminated aquifer bioremediation by biodegradable nutrient-surfactant mix.

Entrapped non-aqueous liquid phase (NAPL) pollutants (e.g., fuels) constitute one of the biggest current problems in the bioremediation efforts of contaminated soil and aquifers worldwide. On site, in situ surfactant-enhanced bioremediation, in the presence of sufficient nutrients and dissolved oxygen, has the potential of becoming the remediation method of choice in terms of both technological and economical feasibility. This approach was applied in our lab-scale column-based flow system with the aid of which an optimized, below CMC, of biodegradable surfactant-nutrient surfactant mix has been established for the best solubilization/ mobilization of NAPL (hexane, toluene, kerosene and their mixtures as "representatives") in sandy matrix. For kerosene, the highest f values (the enhancement factors) were obtained for the systems containing either the amphoteric cocoamphodiacetate or the anionic linear dodecylbenzene sulfonate (0.1-0.3 g/L) with one or both the nutrient-surfactants L and B (0.05 g/L).

Biodegradation, Environmental↗
PubMed2001

Feasibility of on-site bioremediation of loam soil contaminated by diesel oil.

This study originated from an accidental event of diesel oil contamination in a loam soil area of 7,000 m2. Approximately a volume of 1,300 m3 of diesel oil was released into the environment. Reclamation of the contaminated soil by on-site bioremediation was selected as the most appropriate treatment method. A major concern was associated with the nature of the local loam soil. Loam has a very low hydraulic conductivity and very quickly becomes impermeable after its contact with water. The bioremediation approach incorporated excavation of the contaminated soil, mixing it with an agent, which increased its permeability. Following this preliminary treatment came the construction of bioreactors as a suitable environment of nutrients, moisture, dissolved oxygen, and enriched culture of microorganisms, which enabled breakdown of the diesel oil. This case study indicated that the target of 99% of diesel oil clean up could be achieved by using the technology of on-site bioremediation. The selected treatment method was found to be technologically and economically feasible. However, some improvement in the application of the basic treatment approach might increase the bioremediation efficiency.

Biodegradation, Environmental↗
PubMed2001

Synergistic mechanisms in carcinogenesis by polycyclic aromatic hydrocarbons and by tobacco smoke: a bio-historical perspective with updates.

B[a]P (benzo[a]pyrene) has been used as a prototype carcinogenic PAH since its isolation from coal tar in the 1930's. One of its diol epoxides, BPDE-2, is considered its ultimate carcinogen on the basis of its binding to DNA, mutagenicity and extreme pulmonary carcinogenicity in newborn mice. However, BPDE-1 has a similar binding to DNA and mutagenicity but it is not carcinogenic. In addition, BPDE-2 is a weak carcinogen relative to B[a]P when repeatedly applied to mouse skin, the conventional assay site. Its carcinogenicity is increased when applied once as an initiator followed repeatedly by a promoter. This indicates a major role for promotion in carcinogenesis by PAHs. Promotion itself is a 2-stage process, the second of which is selective propagation of the initiated cells. Persistent hyperplasia underlies selection by promoters. The non-carcinogenicity of BPDE-1 has yet to be resolved. PAHs have long been considered the main carcinogens of cigarette smoke but their concentration in the condensate is far too low to account by themselves for the production of skin tumors. The phenolic fraction does however have strong promotional activity when repeatedly applied to initiated mouse skin. Several constituents of cigarette smoke are co-carcinogenic when applied simultaneously with repeated applications of PAHs. Catechol is co-carcinogenic at concentrations found in the condensate. Since cigarette smoking involves protracted exposure to all the smoke constituents, co-carcinogenesis simulates its effects. Both procedures, however, indicate a major role for selection in carcinogenesis by cigarette smoke. That selection may operate on endogenous mutations as well as those induced by PAHs. There are indications that the nicotine-derived NNK which is a specific pulmonary carcinogen in animals contributes to smoking-induced lung cancer in man. Lung adenoma development by inhalation has been induced in mice by the gas phase of cigarette smoke. The role of selection has not been evaluated in either of these cases.

Animals↗
PubMed2001

Developing and implementing measures of quality of care in the intensive care unit.

As consumers, payers, and regulatory agencies require evidence regarding quality of care, the demand for intensive care unit (ICU) quality measures will likely grow. ICU providers and professional societies may need to partner with experts in quality measurement to develop and implement quality measures. This essay outlines the steps for developing and implementing quality measures and provides examples of potential ICU quality indicators. Outcome measures, in particular mortality rates, require risk adjustment, making data collection burdensome and broad implementation unlikely. On the other hand, structure and process measures may be feasible to implement broadly. Given the steps for developing quality measures outlined in this essay and the growing evidence in the literature regarding the impact of ICU care, the future should realize the development and implementation of ICU quality indicators that are rigorously developed and provide insights into opportunities to improve the quality of ICU care.

Humans↗
PubMed2001

Characterization of the cydAB-encoded cytochrome bd oxidase from Mycobacterium smegmatis.

The cydAB genes from Mycobacterium smegmatis have been cloned and characterized. The cydA and cydB genes encode the two subunits of a cytochrome bd oxidase belonging to the widely distributed family of quinol oxidases found in prokaryotes. The cydD and cydC genes located immediately downstream of cydB encode a putative ATP-binding cassette-type transporter. At room temperature, reduced minus oxidized difference spectra of membranes purified from wild-type M. smegmatis displayed spectral features that are characteristic of the gamma-proteobacterial type cytochrome bd oxidase. Inactivation of cydA or cydB by insertion of a kanamycin resistance marker resulted in loss of d-heme absorbance at 631 nm. The d-heme could be restored by transformation of the M. smegmatis cyd mutants with a replicating plasmid carrying the highly homologous cydABDC gene cluster from Mycobacterium tuberculosis. Inactivation of cydA had no effect on the ability of M. smegmatis to exit from stationary phase at 37 or 42 degrees C. The growth rate of the cydA mutant was tested under oxystatic conditions. Although no discernible growth defect was observed under moderately aerobic conditions (9.2 to 37.5 x 10(2) Pa of pO(2) or 5 to 21% air saturation), the mutant displayed a significant growth disadvantage when cocultured with the wild type under extreme microaerophilia (0.8 to 1.7 x 10(2) Pa of pO(2) or 0.5 to 1% air saturation). These observations were in accordance with the two- to threefold increase in cydAB gene expression observed upon reduction of the pO(2) of the growth medium from 21 to 0.5% air saturation and with the concomitant increase in d-heme absorbance in spectra of membranes isolated from wild-type M. smegmatis cultured at 1% air saturation. Finally, the cydA mutant displayed a competitive growth disadvantage in the presence of the terminal oxidase inhibitor, cyanide, when cocultured with wild type at 21% air saturation in an oxystat. In conjunction with these findings, our results suggest that cytochrome bd is an important terminal oxidase in M. smegmatis.

Atmospheric Pressure↗
PubMed2001

Multistage carcinogenesis in cell culture.

Rodent fibroblasts explanted from embryos to culture undergo a period of declining growth rate in serial passages leading to crisis, followed by the appearance of variants which can multiply indefinitely. If the "immortal" cell line was established by low density passage, i.e., 3T3 cells, it has a low saturation density and is non-tumorigenic. If it was established by high density passage, it has a high saturation density and is tumorigenic. The establishment of cells goes through successive stages, including increased capacity to multiply in low serum concentration, growth to high saturation density, growth in suspension, assisted tumour formation in susceptible hosts and unassisted tumour formation. Chromosome aberrations and aneuploidy occur long before the capacity to produce tumours appears. Contrary to conventional belief, human fibroblast populations also undergo a continuous loss of capacity to multiply from the time of explantation, with only the longest surviving clone reaching the Hayflick limit. Neoplastic transformation of rodent cells is strongly favoured by maintaining them in a quiescent state at confluence for prolonged periods, which results in genetic damage to the cells. It also produces a large variety of chromosomal aberrations in human cells and extends their replicative lifespan. Individual clones are more susceptible to spontaneous transformation than their heterogeneous parental cultures. The implications of these results for tumour development in vivo are that oncogenic genetic changes may be common under stressful conditions which restrict replication, and that such changes are maximized when a rogue clone reaches a critical size that reduces stabilizing interactions with neighbouring clones. An alternative explanation, described in the Addendum, which we retrospectively favor is that the easily transformed clones are a minority in the uncloned parental population. The reason they transform before the parental population is that when they are expanded, they have more transformable cells available under the selective condition of confluence than the uncloned parental population from which they are derived.

Cell Culture Techniques↗
PubMed2000

Clonal selection versus genetic instability as the driving force in neoplastic transformation.

Recent clonal studies of spontaneous neoplastic transformation in cell culture indicate that it develops at confluence in a small minority of individual clonal populations before it does in the uncloned parental culture. Either preferential selection of spontaneous variants or genetic destabilization in clones can be inferred to explain the result. In the present experiments, using a subline of NIH 3T3 cells that is relatively refractory to transformation, we demonstrate unequivocally that transformed foci appear under selective conditions in some clones long before there is any sign of neoplastic change in the polyclonal culture from which they were derived. Because the transformed cells that appear in the susceptible clones are not inhibited in the size or number of foci formed on a confluent background of the uncloned parental population, the genetic events underlying transformation must occur much less frequently in the latter. This disparity can be accounted for by the much larger number of selectable cells in the susceptible clones at confluence than in the parental culture, where such cells are a minority. The preferential transformation exhibited by experimental isolation and expansion of susceptible clones accords with evidence from various sources that neoplastic transformation in culture is a multistep process dependent primarily on selection of spontaneously occurring genetic variants. There is no necessity to posit a significant role for genetic destabilization in neoplastic transformation. These considerations bolster computer models of human cancer that implicate selective expansion of rogue clones rather than genetic instability as the driving force in the origin of most tumors. Both the genetics of the selected clone and the epigenetics of the selective environment would then contribute to tumor development.

3T3 Cells↗
PubMed2000

Differential regulation of opposing RelMtb activities by the aminoacylation state of a tRNA.ribosome.mRNA.RelMtb complex.

Rel(Mtb) of Mycobacterium tuberculosis is responsible for the intracellular regulation of (p)ppGpp and the consequent ability of the organism to survive long-term starvation, indicating a possible role in the pathogenesis of tuberculosis. Purified Rel(Mtb) is a dual-function enzyme carrying out ATP: GTP/GDP/ITP 3'-pyrophosphoryltransferase and (p)ppGpp 3'-pyrophosphohydrolase reactions. Here we show that in the absence of biological regulators, Rel(Mtb) simultaneously catalyzes both transferase and hydrolysis at the maximal rate for each reaction, indicating the existence of two distinct active sites. The differential regulation of the opposing activities of Rel(Mtb) is dependent on the ratio of uncharged to charged tRNA and the association of Rel(Mtb) with a complex containing tRNA, ribosomes, and mRNA. A 20-fold increase in the k(cat) and a 4-fold decrease in K(ATP) and K(GTP) from basal levels for transferase activity occur when Rel(Mtb) binds to a complex containing uncharged tRNA, ribosomes, and mRNA (Rel(Mtb) activating complex or RAC). The k(cat) for hydrolysis, however, is reduced 2-fold and K(m) for pppGpp increased 2-fold from basal levels in the presence of the Rel(Mtb) activating complex. The addition of charged tRNA to this complex has the opposite effect by inhibiting transferase activity and activating hydrolysis activity. Differential control of Rel(Mtb) gives the Mtb ribosomal complex a new regulatory role in controlling cellular metabolism in response to stringent growth conditions that may be present in the dormant Mtb lesion.

Acylation↗
PubMed2000

Conformational change and intermediates in the unfolding of alpha 1-antichymotrypsin.

Serpins are the prototypical members of the conformational disease family, a group of proteins that undergoes a change in shape that subsequently leads to tissue deposition. One specific example is alpha(1)-antichymotrypsin (ACT), which undergoes misfolding and aggregation that has been implicated in emphysema and Alzheimer's disease. In this study we have used guanidine hydrochloride (GdnHCl)-induced denaturation to investigate the conformational changes involved in the folding and unfolding of ACT. When the reaction was followed by circular dichroism spectroscopy, one stable intermediate was observed in 1.5 m GdnHCl. The same experiment monitored by fluorescence revealed a second intermediate formed in 2.5 m GdnHCl. Both these intermediates bound the hydrophobic dye ANS. These data suggest a four-state model for ACT folding N <--> I(1) <--> I(2) <--> U. I(1) and I(2) both have a similar loss of secondary structure (20%) compared with the native state. In I(2), however, there is a significant loss of tertiary interactions as revealed by changes in fluorescence emission maximum and intensity. Kinetic analysis of the unfolding reaction indicated that the native state is unstable with a fast rate of unfolding in water of 0.4 s(-1). The implications of these data for both ACT function and associated diseases are discussed.

Protein Conformation↗
PubMed2000

Coculturing diverse clonal populations prevents the early-stage neoplastic progression that occurs in the separate clones.

Most human cancers are of monoclonal origin and display many genetic alterations. In an effort to determine whether clonal expansion itself could account for the large number of genetic alterations, we compared spontaneous transformation in cloned and uncloned populations of NIH 3T3 cells. We have reported that progressive transformation of these cells, which is driven by the stress of prolonged contact inhibition at confluence, occurs far more frequently in cultures of recent monoclonal origin than in their uncloned progenitors. In the present work we asked how coculturing six clones at early and late stages of progression would affect the dynamics of transformation in repeated rounds of confluence. When coculture started with clones in early stages of transformation, marked by light focus formation, there was a strong inhibition of the progression to the dense focus formation that occurred in separate cultures of the individual clones. In contrast, when coculture started after the individual clones had progressed to dense focus formation, there was selection of transformants from the clone producing the largest and densest foci. Mixing the cells of a single clone with a large excess of uncloned cells from a subline that was refractory to transformation markedly decreased the size of dense foci from clones in transit from light to dense focus formation, but had much less effect on foci from clones with an established capacity for dense focus formation. The major finding of protection against progression by coculturing clones in early stages of transformation suggests that the expansion of a rogue clone in vivo increasingly isolates many of its cells from genetically stabilizing interactions with surrounding clones. Such clonal isolation might account for the increase in mutation rates associated with the dysplasia in colorectal adenomas that signifies the transition between benign and malignant growth.

3T3 Cells↗
PubMed2000

Armadillo exposure and Hansen's disease: an epidemiologic survey in southern Texas.

BACKGROUND: Naturally occurring leprosy has been demonstrated in wild nine-banded armadillos (Dasypus novemcinctus ). This suggests a possible mode of transmission of human leprosy in regions where armadillo contact is prevalent. OBJECTIVE: Our purpose was to study the possible relationship between armadillo exposure and Hansen's disease. METHOD: One hundred one patients (67 men, 34 women) with established Hansen's disease seen in the Hansen's Disease Clinic in Houston, Texas, were questioned about their exposure to armadillos. These patients were divided into two groups: Asian (n = 32) and non-Asian (n = 69). RESULTS: Seventy-one percent of the non-Asian patients surveyed reported either direct or indirect armadillo exposure. None of the Asian patients reported armadillo exposure (P <.001). Of the non-Asian patients, 75.4% had lepromatous disease versus 50.0% of the Asian patients (P <.001). The average age at diagnosis for the non-Asian group with Hansen's disease in this study was 51 versus 38 years for the Asian group (P <.001). CONCLUSION: Although it is yet to be determined whether direct transmission from the armadillo to human occurs, it is likely based on the high incidence of armadillo exposure in non-Asian patients with Hansen's disease in our study population that this animal acts as a reservoir for human disease. However, the Asian patients reporting no known armadillo exposure likely obtained the disease from person-to-person contact in their respective countries of origin where Hansen's disease has a much higher prevalence.

Adolescent↗
PubMed2000

Intensive care unit telemedicine: alternate paradigm for providing continuous intensivist care.

OBJECTIVE: Intensive care units (ICUs) account for an increasing percentage of hospital admissions and resource consumption. Adverse events are common in ICU patients and contribute to high mortality rates and costs. Although evidence demonstrates reduced complications and mortality when intensivists manage ICU patients, a dramatic national shortage of these specialists precludes most hospitals from implementing an around-the-clock, on-site intensivist care model. Alternate strategies are needed to bring expertise and proactive, continuous care to the critically ill. We evaluated the feasibility of using telemedicine as a means of achieving 24-hr intensivist oversight and improved clinical outcomes. DESIGN: Observational time series triple cohort study. SETTING: A ten-bed surgical ICU in an academic-affiliated community hospital. PATIENTS: All patients whose entire ICU stay occurred within the study periods. INTERVENTIONS: A 16-wk program of continuous intensivist oversight was instituted in a surgical ICU, where before the intervention, intensivist consultation was available but there were no on-site intensivists. Intensivists provided management during the intervention using remote monitoring methodologies (video conferencing and computer-based data transmission) to obtain clinical information and to communicate with on-site personnel. To assess the benefit of the remote management program, clinical and economic performance during the intervention were compared with two 16-wk periods within the year before the intervention. MEASUREMENTS AND MAIN RESULTS: ICU and hospital mortality (observed and Acute Physiology and Chronic Health Evaluation III, severity-adjusted), ICU complications, ICU and hospital length-of-stay, and ICU and hospital costs were measured during the 3 study periods. Severity-adjusted ICU mortality decreased during the intervention period by 68% and 46%, compared with baseline periods one and two, respectively. Severity-adjusted hospital mortality decreased by 33% and 30%, and the incidence of ICU complications was decreased by 44% and 50%. ICU length of stay decreased by 34% and 30%, and ICU costs decreased by 33% and 36%, respectively. The cost savings were associated with a lower incidence of complications. CONCLUSIONS: Technology-enabled remote care can be used to provide continuous ICU patient management and to achieve improved clinical and economic outcomes. This intervention's success suggests that remote care programs may provide a means of improving quality of care and reducing costs when on-site intensivist coverage is not available.

APACHE↗