Expression of glyceraldehyde-3-phosphate dehydrogenase during differentiation of HD3 cells

The chicken erythroblast cell line HD3, which is infected with a temperature-sensitive avian erythroleukemia virus, becomes committed to differentiate to an erythrocyte upon temperature shift in the presence of inducers (hemin and butyric acid). The activity of glyceraldehyde-3-phosphate dehydrogenase (GAD), a key enzyme in the glycolytic pathway, was examined. Upon induction of differentiation the following changes in glyceraldehyde-3-phosphate dehydrogenase activity and the corresponding mRNA level occurred. Twenty-four hours post-induction the glyceraldehyde-3-phosphate dehydrogenase message decreased and virtually disappeared within 48 h. Glyceraldehyde-3-phosphate dehydrogenase activity did not follow the mRNA level and increased within 48 h post-induction and then started to fall. The discrepancy between glyceraldehyde-3-phosphate dehydrogenase activity and the mRNA level is likely due to a difference in GAD protein and mRNA half-lives. The results also suggest that enzyme activity could be regulated by post-translational events. Chicken erythrocytes expressed reduced levels of glyceraldehyde-3-phosphate dehydrogenase activity. Thus the low level of GAD found in chicken erythrocytes is associated with a turn off of GAD gene expression upon induction of erythroid differentiation.

Characterization of the avian GLUT1 glucose transporter: differential regulation of GLUT1 and GLUT3 in chicken embryo fibroblasts

Vertebrate cells that are transformed by oncogenes such as v-src or are stimulated by mitogens have increased rates of glucose uptake. In rodent cells, the mechanisms whereby glucose transport is up-regulated are well understood. Stimulation of glucose transport involves an elevation in mRNA encoding the GLUT1 glucose transporter that is controlled at the levels of both transcription and mRNA stability. Cloning and sequencing of chicken GLUT1 cDNA showed that it shares 95% amino acid sequence similarity to mammalian GLUT1s. Nevertheless, unlike mammalian GLUT1 mRNA, it was not induced by v-src, serum addition, or treatment with the tumor promoter 12-O-tetradecanoylphorbol 13-acetate in chicken embryo fibroblasts. Rather, the induction of glucose transport in chicken embryo fibroblasts by v-src, serum, and 12-O-tetradecanoylphorbol 13-acetate was associated with induction of GLUT3 mRNA level and GLUT3 transcription. Rat fibroblasts were also found to express both GLUT1 and GLUT3 isoforms, but v-src induced GLUT1 and not GLUT3. This suggests that animal cells require both a basal and an upregulatable glucose transporter and that these functions have been subsumed by different GLUT isoforms in avian and mammalian cells.

Loss of glucose transporters is an early event in differentiation of HD3 cells

The HD3 cell, a chicken erythroblast cell line infected with a temperature-sensitive avian erythroblastosis virus, becomes committed to differentiate to an erythrocyte upon temperature shift in presence of inducers. Before induction, the HD3 cell transports glucose and 2-deoxyglucose (2-DG). 3-O-methylglucose is poorly taken up. Upon induction of differentiation, glucose and 2-DG transport activity fall. Twenty-four hours postinduction, up to 75% of the glucose transport activity may disappear. By use of cDNA probes for chicken glucose transporters, two species of mRNA of 3.1 and 1.7 kb (equivalent to mammalian GLUT1 and GLUT3 mRNA, respectively) are detected. Both messages virtually disappear within 48 h after induction. Run-on assays show the cessation of synthesis of the corresponding RNAs parallel to the loss of glucose transport. In contrast to the glucose transporters, the nucleoside transporter level increases after induction of hematopoiesis. This developmental pattern is consistent with earlier studies showing that mature chicken erythrocytes have little glucose transport activity but retain appreciable levels of the nucleoside transporter and that nucleosides and glutamine provide major sources of oxidizable carbon compounds to sustain metabolism in circulating chicken erythrocytes.

Comparative analysis of the sequence and structure of two Drosophila melanogaster genes encoding vitelline membrane proteins

Two Drosophila melanogaster vitelline membrane protein-encoding genes (VM), located at polytene band positions 26A and 34C, have been cloned and comparatively characterized at the nucleotide level. Sequence analysis of genomic and cDNA clones for the two genes, VM26A.1 and VM34C.1, indicates that both are similarly organized with a central highly conserved domain [Scherer et al., Dev. Biol. 130 (1988) 786-788] which is flanked by unrelated regions, and that both genes lack introns. Comparison of the upstream regions reveals that both VM genes contain a hepatmeric element identical to one associated with the D. melanogaster yolk protein-encoding genes (YP). This heptamer occurs in the specific 5' flanking region responsible for ovarian temporal- and tissue-specific control in both VM and YP genes. A putative chorion transcription factor 2 site is also associated with an upstream control element of VM26A.1, but not with any sequenced portion of VM34C.1.

Retroviral infection can abrogate the factor-dependency of hematopoietic cells by autocrine and non-autocrine mechanisms depending on the presence of a functional viral oncogene

The mechanisms responsible for abrogation of the growth factor-dependency of a hematopoietic cell line were investigated. FDC-P1 cells were infected with retroviral constructs containing the neo gene and either a wild-type or a temperature-sensitive v-src oncogene. v-srcwt abrogated the factor-dependency of these cells since each G418r colony gave rise to factor-independent cells and no autocrine growth factor activity was detected. Moreover, the vast majority (< 99%) of cells infected with the v-srcts mutant gave rise to conditional factor-independent cells. Therefore a functional v-src gene product was required for growth factor-independence which occurred by a non-autocrine mechanism. A minority of factor-independent cells which arose after v-srcts infection, grew at the non-permissive temperature and one-half secreted granulocyte/macrophage-colony stimulating factor (GM-CSF) which supports the growth of the parental cells. Since the v-srcts viral stock contained a helper virus, Murine Leukemia Virus (MuLV), the ability of this virus to relieve factor-dependency was examined. A low frequency of factor-independent transformants was recovered after MuLV infection and one-half secreted GM-CSF. Therefore, retroviruses such as MuLV which lack an oncogene, can transform cells by stimulating autocrine growth factor secretion. Subsequent experiments performed with helper-free v-src preparations indicated that they could abrogate factor-dependency directly by a non-autocrine mechanism. These results demonstrate that a hematopoietic cell line can be transformed by two different mechanisms after retroviral infection and may be relevant for understanding hematopoietic cell transformation after persistent viral infection.

The expression of an adhesion-related protein by clam hemocytes

Molluscs have circulating cells in the hemolymph which are both adherent and phagocytic. Mya arenaria, the soft-shell clam, is particularly interesting because it develops a leukemia detected first in the hemolymph and, as the disease progresses, in solid tissue. We have previously described a leukemia-specific protein (Miosky et al., 1989) identified by murine monoclonal antibodies generated to pure populations of leukemia cells. In the following work, a monoclonal antibody was generated to normal hemocytes of Mya. The antibody, designated 2A4, was evaluated by ELISA, immunocytochemistry, Western blotting, and flow cytometry. The 2A4 antigen was detected on 87% normal adherent cells. However, 2A4 was lost as leukemia cells proliferated. The mature leukemia cell, which is nonadherent, neither expresses 2A4 nor can 2A4 be detected in the leukemia cell lystate. Western blot analyses reveal that 2A4 reacts with a 130-kDa protein. Our data suggest that p130 may be involved in the regulation of cell adhesion.

Differential regulation of glucose transporter isoforms by the src oncogene in chicken embryo fibroblasts

The increase in glucose transport that occurs when chicken embryo fibroblasts (CEFs) are transformed by src is associated with an increase in the amount of type 1 glucose transporter protein, and we have previously shown that this effect is due to a decrease in the degradation rate of this protein. The rate of CEF type 1 glucose transporter biosynthesis and the level of its mRNA are unaffected by src transformation. To study the molecular basis of this phenomenon, we have been isolating chicken glucose transporter cDNAs by hybridization to a rat type 1 glucose transporter probe at low stringency. Surprisingly, these clones corresponded to a message encoding a protein which has most sequence similarity to the human type 3 glucose transporter and which we refer to as CEF-GT3. CEF-GT3 is clearly distinct from the CEF type 1 transporter that we have previously described. Northern (RNA) analysis of CEF RNA with CEF-GT3 cDNA revealed two messages of 1.7 and 3.3 kb which were both greatly induced by src transformation. When the CEF-GT3 cDNA was expressed in rat fibroblasts, a three-to fourfold enhancement of 2-deoxyglucose uptake was observed, indicating that CEF-GT3 is a functional glucose transporter. Northern analyses using a CEF-GT3 and a rat type 1 probe demonstrated that there is no hybridization between different isoforms but that there is cross-species hybridization between the rat type 1 probe and the chicken homolog. Southern blot analyses confirmed that the chicken genomic type 1 and type 3 transporters are encoded by distinct genes. We conclude that CEFs express two types of transporter, type 1 (which we have previously reported to be regulated posttranslationally by src) and a novel type 3 isoform which, unlike type 1, shows mRNA induction upon src transformation. We conclude that src regulates glucose transport in CEFs simultaneously by two different mechanisms.

The effectiveness of ice- and Freon-based personal cooling systems during work in fully encapsulating suits in the heat

The use of cooling garments in conjunction with fully encapsulating suits offers the potential for reducing the heat strain for workers at hazardous waste sites and chemical emergencies. This study examined the use of ice- and Freon-based cooling garments during exercise in the heat while wearing a U.S. Coast Guard chemical response suit (CRS), a fully encapsulating, Teflon-coated, Nomex suit. Responses of nine healthy men (mean age 28.8 yr) were measured during moderate exercise at 30% of their maximal oxygen consumption in an environmental chamber maintained at 33.9 degrees C (93 degrees F) and 82% relative humidity. The four randomly assigned experimental conditions were (1) the CONTROL, consisting of a self-contained breathing apparatus (SCBA) worn in conjunction with shorts, shirt, helmet, and shoes; (2) the CRS, consisting of the Coast Guard CRS worn with shorts, shirt, SCBA, helmet, gloves, and boots; (3) the ICE, which was identical to the CRS ensemble, with the addition of an ice and water cooling system; and (4) the FREON, which was also identical to the CRS ensemble, with the addition of a Freon-based cooling system. To the author's knowledge, this paper is the first to quantify and compare a Freon-based system with a circulating ice water system. The subjects performed repeated rest/work intervals for 45 min, followed by a 10-min recovery period. Measured physiological responses, including heart rate, skin, rectal, and axillary temperatures, were recorded at 1-min intervals during the tests.(ABSTRACT TRUNCATED AT 250 WORDS)

The src oncogene can regulate a human glucose transporter expressed in chicken embryo fibroblasts

When fibroblasts are transformed by the src oncogene, there is a two- to fivefold increase in glucose transport and in the level of immunoprecipitable glucose transporter protein. In chicken embryo fibroblasts (CEFs), this increase is correlated with a comparable reduction in the rate at which the glucose transporter protein is turned over. In contrast, in mammalian fibroblasts glucose transporter biosynthesis is increased by src, but there is little or no change in its turnover. To further understand the action of src on transporter turnover, we investigated whether a mammalian transporter can be stabilized by src in a chicken cell environment. The human type 1 glucose transporter protein (hGT), originally cloned from HepG2 cells, was expressed in CEFs or Rat-1 fibroblasts by using a retroviral vector. In CEFs transformed by a temperature-sensitive src mutant, tsNY68, turnover of hGT was lower at the permissive temperature (36 degrees C) than at the nonpermissive temperature (42 degrees C). When this protein was expressed in CEFs transformed by wild-type src, no difference in turnover was observed at the two temperatures. In the case of Rat-1 cells transformed by the temperature-sensitive src mutant tsLA29, turnover of hGT was the same at the permissive temperature (35 degrees C) as at the nonpermissive temperature (39.5 degrees C). These data demonstrate that a heterologous glucose transporter behaves in the same way in chicken and rat cells as the respective endogenous transporter, i.e., when src is active, the protein is stablilized against turnover in chicken cells but not in rat cells.

Physiological and subjective responses to working in disposable protective coveralls and respirators commonly used by the asbestos abatement industry

The physiological and subjective effects of working with different respirators while wearing lightweight disposable (Tyvek 1412 polyolefin) coveralls commonly used by the asbestos abatement industry were studied. Nine healthy men (mean age = 27.3 yr, weight = 76.9 kg) each performed a series of four exercise tests with four different respirator ensembles in counterbalanced order. Treadmill work was performed at a set walking speed of 4 kph (2.5 mph), 0 percent elevation (220 kcal/hr), a controlled environmental temperature of 33.9 degrees C, and 50% relative humidity. Each test continued up to 120 min, with repeated work/rest intervals of 26 min of work and 4 min of rest. Tyvek disposable coveralls and hoods were worn with each of these four different respirator ensembles: (1) control--a lightweight, low resistance mask; (2) HEPA--an air purifying, full facepiece respirator with dual high efficiency filters; (3) SAR--a supplied-air, pressure-demand respirator with escape filter; (4) SCBA--an open circuit, pressure-demand, self-contained breathing apparatus. Physiological measurements obtained every minute during each test included heart rate and skin and rectal temperatures. Subjective evaluations of clothing, respirator, and facepiece comfort, ease of breathing, temperature and perspiration in the mask and clothing, and respirator load also were measured at the end of the test. Data were analyzed using an analysis of variance. Results indicated that heart rate at the end of the test differed by less than 8 BPM between the control condition and the SCBA (heaviest) condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Physiological responses to the wearing of fire fighter's turnout gear with neoprene and GORE-TEX barrier liners

This study examined the physiological effects of performing moderate and high intensity work while wearing fire fighter's turnout gear with either a neoprene or GORE-TEX barrier liner. Eight healthy men, experienced with the use of respirators and protective clothing, each performed moderate and high intensity treadmill exercise (44% and 71% of maximum work capacity) in a double-blind study at 27.6 degrees C (50% RH) while wearing complete fire fighter's turnout gear (weighing 23 kg) with either a neoprene or GORE-TEX barrier liner. Physiological measurements obtained included minute ventilation, heart rate, skin temperature, rectal temperature and sweat rate. Subjective evaluations of perceived exertion, comfort, clothing breathability, temperature and perspiration also were obtained. Tests were terminated (tolerance time) when objective or subjective signs of near maximal stress were observed (i.e., 90% of the maximum heart rate, rectal temperature of 39 degrees C, dizziness, etc.). Mean tolerance times for the moderate intensity exercise were 27.4 (+/- 7.3 S.D.) and 30.9 (+/- 7.9) min, respectively, for the neoprene and GORE-TEX barrier liners and at the high intensity were 7.2 (+/- 2.1) and 7.5 (+/- 2.3) min, respectively. Analysis of variance indicated that significant differences caused by liner were observed in skin temperature (0.6 degrees C higher with the neoprene ensemble). No significant differences caused by liner were seen in tolerance time, heart rate, sweat rate or subjective ratings.(ABSTRACT TRUNCATED AT 250 WORDS)

Optimal positive end-expiratory pressure therapy in infants and children with acute respiratory failure

Positive end-expiratory pressure (PEEP) has become a mainstay in the treatment of hypoxemic acute respiratory failure (ARF). Whereas PEEP improves arterial oxygen tension by decreasing intrapulmonary shunting, it may also impair cardiac output and hence decrease systemic oxygen transport. Inasmuch as optimizing oxygen transport is a goal of therapy in ARF, we sought to determine if the level of PEEP that results in maximal oxygen transport could be estimated from measurements of compliance of the respiratory system (Crs) or PaO2. We studied the effects of PEEP application on cardiorespiratory parameters in 15 children who required mechanical ventilation for ARF. Static Crs, PaO2, central venous and arterial blood pressures, indicator dilution cardiac index (CI), and oxygen transport were determined at 0, 3, 6, 9, 12, and 15 cm H2O PEEP. PaO2 increased significantly at PEEP levels greater than or equal to 9 cm H2O (p less than 0.001), while CI fell by 15% between 0 and 15 cm end-expiratory pressure (p less than 0.02). Crs and oxygen transport did not change significantly with increasing levels of PEEP. The level of PEEP resulting in maximal oxygen transport ranged from 0 to 15 cm H2O, and in all patients it corresponded to PEEP of best CI. At levels of PEEP above that associated with maximal oxygen transport, CI and oxygen transport fell significantly, while PaO2 continued to rise. No relationship between Crs and oxygen transport was observed. In our normovolemic patients with ARF, neither PaO2 nor Crs predicted PEEP of maximal oxygen transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Transformation by the src oncogene alters glucose transport into rat and chicken cells by different mechanisms

Transformation of both rat and chicken fibroblasts by the src oncogene leads to a four- to fivefold increase in the rate of glucose transport and in the level of the glucose transporter protein. We have previously shown that, with chicken embryo fibroblasts, transformation leads to a reduction in the rate of degradation of the transporter, with little or no increase in the rate of its biosynthesis. We now show that, with the rat-1 cell line, the opposite result was obtained. src-induced transformation led to an increase in transporter biosynthesis, with little effect on turnover. A src-induced increase in transporter mRNA entirely accounted for the increase in biosynthesis of the protein. By contrast, in chicken embryo fibroblasts, the level of transporter mRNA was low and was not induced to rise by src transformation. Thus, src induced an increase in the level of the glucose transport protein by fundamentally different mechanisms in chicken embryo fibroblasts and rat-1 cells. To test whether this difference was due to rat-1 cells being an immortalized cell line, we measured transporter mRNA levels in primary fibroblast cultures from rat embryos and in parallel cultures transformed by src. Transporter mRNA was inducible by src in these cells. Thus, the difference in mRNA inducibility between chicken and rat cells is not due to immortalization.

Degradation and biosynthesis of the glucose transporter protein in chicken embryo fibroblasts transformed by the src oncogene

The rate of glucose transport in cultured fibroblasts is regulated to a number of physiological variables, including malignant transformation by src, glucose starvation, and stimulation with mitogens. Much of this transport regulation can be accounted for by variations in the amount of transporter protein in the cells. To determine the mechanisms by which levels of the transporter are regulated, we measured the rates of synthesis and degradation of the transporter by pulse-chase experiments and immunoprecipitation of the transporter. We found that transformation by the src oncogene results in a large decrease in the rate at which the transporter protein is degraded but that it does not appreciably increase the rate of transporter biosynthesis. On the other hand, glucose starvation and mitogen stimulation increase the rate of transporter biosynthesis, although a role for control of degradation is possible in these circumstances also. Variations in the rate of glucose transport or the amount of the transporter are not associated with phosphorylation of the transporter protein.

Reduced work tolerance associated with wearing protective clothing and respirators

This study examined worker tolerance and physiological responses to two levels of work while subjects wore various types of protective clothing and respirators. Nine healthy men (mean age = 24.8 years, weight = 75.3 kg, max VO2 = 44.6 mL/kg/min), experienced with the use of respirators, each performed a randomized series of eight experimental tests, each test scheduled to last 180 min. Work was performed on a motor-driven treadmill at a set walking speed and elevation indicative of either 30% (low work intensity) or 60% (high work intensity) of maximum work capacity for each individual. Four protective clothing ensembles were examined: light work clothing (LIGHT), light work clothing with SCBA (SCBA), firefighter's turnout gear with SCBA (FF) and chemical protective clothing with SCBA (CHEM). Physiological measurements included heart rate, skin and rectal temperature, and minute ventilation. Measurements were obtained every 2.5 min until test termination (tolerance time). If less than 180 min, tolerance time was defined by subjective or objective signs of near maximal stress. Mean tolerance times at the low work intensity were 167, 130, 26 and 73 min, respectively, for the LIGHT, SCBA, FF and CHEM ensembles. At the high intensity, mean tolerance times were 91, 23, 4 and 13 min, respectively. At the low work intensity, heart rate with SCBA rose very slowly during the tests and remained approximately 15 beats/min higher than the heart rate for subjects wearing the LIGHT ensemble. In contrast, heart rate with the FF and CHEM ensembles rose sharply and did not approach steady-state values.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydrogen sulfide and the probabilities of 'inhalation' through a tympanic membrane defect

We conclude that workers with tympanic membrane defects (perforated eardrums) should not be excluded from working in atmospheres containing concentrations of hydrogen sulfide (H2S). Several existing requirements and recommendations exclude workers with perforated eardrums from working in or around H2S. Such protective measures stem from the belief that H2S can enter the body through the perforation in sufficient measure to compromise the wearer's respiratory protection. However, based on calculations of anticipated leakage of H2S for a variety of eustachian tube conditions and in the absence of either medical literature or personal reports documenting H2S poisoning due to eardrum perforation, the recommendation for excluding workers with such a condition from working in or around H2S is not supported. The anatomy, physiology, and pathology of the eustachian tube are discussed, including the effects such devices as tympanomaxillary shunts might have on contaminant leakage. The National Institute for Occupational Safety and Health (NIOSH) criteria for respirator tests and sources of respirator leakage are examined and NIOSH recommendations for respiratory protection against H2S are outlined.

The effects of exercise on the bones of postmenopausal women

The effects of walking and aerobic dancing on the bones of 73 recently postmenopausal women have been compared by photon absorptiometry of the distal radius with a control group who did not exercise. The period of observation was six months. Results showed that the control group and the walking group lost statistically significant amounts of bone mineral content (1.6%, and 1.7% respectively), but that the dancing group did not (0.8%). The control group did not show a significant increase in the bone width (0.9%), but both the dancing (1.3%) and walking (1.6%) groups did. Changes in the cross-sectional moment of inertia of the radius were estimated for each subject based on bone mineral content and bone width values. Both exercise groups experienced significant increases in this variable, while the control group did not. Plasma oestrogen levels were not influenced by exercise. The results support the hypothesis that mechanical loading due to exercise may be effective in preventing postmenopausal osteoporosis.

Alterations induced by glucose deprivation and tunicamycin in the kinetic parameters of hexose transport in hybrid cells

Matched pairs of malignant and non-malignant hybrid cells were compared in their response to glucose deprivation and to tunicamycin. Glucose deprivation induced an increase in the maximum velocity in the malignant cells, but not in the non-malignant cells. The Michaelis constant of hexose uptake was largely unchanged by glucose deprivation except in the case of one melanoma derivative, PG19 G-, which showed a large increase in Michaelis constant when deprived of glucose. Tunicamycin increased the Michaelis constant of hexose uptake in both malignant and non-malignant cell lines. It is therefore possible that the Michaelis constant of hexose uptake is affected by the extent of glycosylation of one or more of the cell membrane glycoproteins.

Association of an integral membrane protein with glucose transport and with anion transport

A monoclonal antibody that recognizes a cell-surface glycoprotein associated with glucose transport was reported previously. Additional information about the function and intracellular distribution of the antigen recognized by this antibody is presented. The monoclonal antibody recognizes a cell-surface and a cytoplasmic determinant. The density of the cell-surface determinant is heterogeneous within the cell population. The subpopulation of cells that carry the cell-surface determinant at high density correspond with a subset of cells that incorporate 2-deoxy-D-[3H]glucose more rapidly than the population as a whole. The monoclonal antibody is used, with cell-affinity chromatography, to isolate this subset of cells. The cytoplasmic determinant, to which the antibody binds, is associated with the cytoplasmic microfilaments but the antibody is not absorbed by actin. The cell-surface and cytoplasmic components are not identical since the apparent affinity of the antibody for each site is different. The portion of the antigen in the membrane behaves as an integral membrane protein while the remainder is tightly associated with the detergent-insoluble cytoskeleton. The expression of the antigen on the cell surface is modified by covalent attachment of an inhibitor of anion transport, 4,4′-diisothiocyano-2,2′-disulphonic stilbene. The possible interaction of the anion/lactate transporter with the glucose transporter is discussed.

Kinetic parameters of neutral amino acid transport in hybrids between malignant and non-malignant cells

The kinetics of neutral amino acid transport were examined in isogeneic matched pairs of hybrid cells, one member of each pair being tumorigenic, the other not. The L system of transport, which is sodium-independent, was measured by the uptake of leucine, and the A system, which is sodium-dependent, by the uptake of methylaminoisobutyric acid. Although there was variation from one cell type to another in both Km and Vmax for the transport of these amino acids, no systematic change was found to be associated with tumorigenicity. This is in marked contrast with hexose uptake where tumorigenicity was invariably found to be associated with a reduction in Km. It thus appears that whatever molecular change is responsible for the alteration in the kinetics of hexose transport, it is specific, at least to the extent that it does not affect either sodium-dependent or sodium-independent transport of neutral amino acids.

Kinetic parameters of hexose transport in hybrids between malignant and nonmalignant cells

Matched pairs of isogeneic hybrid cells, in which one member of the pair was malignant and the other not, were used to examine the linkage between malignancy and functional alterations in hexose transport. The kinetic parameters of uptake of 2-deoxy-D-glucose were measured in a range of such hybrids, both human and murine. Some other malignant cell lines were also examined and were compared with non-tumorigenic derivatives of tumour cells selected by exposure to the lectin, wheat-germ agglutinin. In every case, malignancy, as defined by the ability of cells to grow progressively in vivo, was found to be linked to a decrease in the Michaelis constant of hexose uptake. Independent measurement of the transport and phosphorylation reactions involved in hexose uptake revealed that this decrease was determined by the membrane transport system. The difference in Michaelis constant between malignant and non-malignant cells was observed with 3-O-methylglucose, a hexose that is transported into the cell but not further metabolized. The activity of hexokinase in cell homogenates was higher than the level that would be required to cope with transport and showed no correlation with tumorigenicity. Measurement of the uptake of D-glucose itself, by a rapid filtration centrifugation method, gave results similar to those obtained with 2-deoxy-D-glucose.

Hexose transport in hybrids between malignant and normal cells

The kinetic parameters of hexose uptake were measured in matched pairs of hybrids between malignant and normal cells. Each pair consisted of a hybrid in which malignancy was initially suppressed and a segregant tumour derived from it. Comparisons were also made between tumour cells and non-tumorigenic derivatives selected from the tumour cell populations in vitro. Without exception, malignancy, as defined by the ability of the cell to grow progressively in vivo, was found to be linked to a systematic decrease in the Michaelis constant of the hexose transport system.

Intrauterine device termination rates and the menstrual cycle day of insertion

World-wide clinicians apparently prefer to insert the intrauterine device (IUD) during the bleeding phase of the menstrual cycle. To examine the benefits and risks of inserting IUDs at various times during the menstrual cycle, data on over 9000 women having copper T-200 IUD insertions were analyzed. During the first 2 months after IUD insertion: 1) rates of IUD expulsion are lower the later in the menstrual cycle ;he IUD is inserted; 2) rates of IUD removal for pain and bleeding and rates of accidental pregnancy, are higher the later in the menstrual cycle IUD is inserted, particularly after day 17. The present analysis suggests that the above are probably causal associations. It is estimated that 1000 insertions before day 11 will result in 9 more terminations of IUD use for expulsion, pain and bleeding, and accidental pregnancy than if the insertions are done after day 11. Furthermore, the copper T-200 IUD can be inserted with relative safety on the day it is requested if the woman's history indicates that she is unlikely to be pregnant. There is no justification for a blanket policy of inserting IUDs only during the menses.

Complementation analysis of eleven tryptophanase mutations in Escherichia coli

Nine independent mutants deficient in tryptophanase activity were isolated. Each mutation was transferred to a specialized transducing phage that carries the tryptophanase region of the Escherichia coli chromosome. The nine phages thus produced, and a tenth carrying a previously characterized tryptophanase mutation, were used to lysogenize a bacterial strain harbouring a mutation in the tryptophanase structural gene and also a suppressor of polarity. In no case was complementation observed; we conclude that there is no closely linked positive regulatory gene for tryptophanase.

A case-control study of uterine perforations documented at laparoscopy

A case-control analysis was done of 19 cases of uterine perforations which occurred during laparoscopic sterilization at Gardy Memorial Hospital in Atlanta, between February 1, 1974, and January 31, 1976. The over-all perforation rate, 30.4 per 1,000 procedures, is three to 30 times that commonly reported for dilatation and suction or sharp curettage (D&C) of the uterus. Case women were 10.4 times more likely than control women to combine two of the following three characteristics: age greater than 34, parity greater than 4, and obesity greater than 20 per cent above the ideal body weight for height. Surgeons with fewer months of formal Ob/Gyn training were no more likely than their relatively more experienced colleagues to perforate the uterus. No other risk factors were delineated. It is believed that the perforation rate, higher in this study than in earlier ones, reflects better ascertainment of perforations. The bleeding site was always visualized with the laparoscope in this series.