Occupational balance as a component in weight loss interventions

BACKGROUND

Obesity can limit occupational participation because of physical and mental barriers. Weight loss programmes emphasizing dietary and physical activity may lower body weight; however, mental barriers and sustainable weight loss seemed to be challenged. Weight loss influences daily patterns and structure of occupations and finding a balance in daily life during the weight loss process might improve sustainable weight loss.

AIM

To explore if and how health professionals conducting weight loss programmes in Danish municipalities address elements related to occupational balance in the daily life of citizens with obesity.

MATERIAL AND METHODS

Twenty individual interviews with health professionals from Danish municipalities were conducted and analysed.

RESULTS

(1) Helping participants find the time and energy to lose weight, (2) Emphasizing small steps for sustainable changes and (3) Utilizing the citizen's life experience for direction.

CONCLUSION

Elements of occupational balance might be addressed by the participants, however values and meaningfulness regarding occupations seem to be missing. Integrating occupational balance in weight loss programmes could enable health professionals to understand and address sustainable weight loss.

SIGNIFICANCE

Occupational therapists may be ideally suited to support citizens with obesity to sustain weight loss by supporting a balanced life focussing on meaningfulness and values in occupations.

Estimating wetland connectivity to streams in the Prairie Pothole Region: an isotopic and remote sensing approach

Understanding hydrologic connectivity between wetlands and perennial streams is critical to understanding the reliance of stream flow on inputs from wetlands. We used the isotopic evaporation signal in water and remote sensing to examine wetland-stream hydrologic connectivity within the Pipestem Creek watershed, North Dakota, a watershed dominated by prairie-pothole wetlands. Pipestem Creek exhibited an evaporated-water signal that had approximately half the isotopic-enrichment signal found in most evaporatively enriched prairie-pothole wetlands. Groundwater adjacent to Pipestem Creek had isotopic values that indicated recharge from winter precipitation and had no significant evaporative enrichment, indicating that enriched surface water did not contribute significantly to groundwater discharging into Pipestem Creek. The estimated surface-water area necessary to generate the evaporation signal within Pipestem Creek was highly dynamic, varied primarily with the amount of discharge, and was typically greater than the immediate Pipestem Creek surface-water area, indicating that surficial flow from wetlands contributed to stream flow throughout the summer. We propose a dynamic range of spilling thresholds for prairie-pothole wetlands across the watershed allowing for wetland inputs even during low flow periods. Combining Landsat estimates with the isotopic approach allowed determination of potential (Landsat) and actual (isotope) contributing areas in wetland-dominated systems. This combined approach can give insights into the changes in location and magnitude of surface water and groundwater pathways over time. This approach can be used in other areas where evaporation from wetlands results in a sufficient evaporative isotopic signal.

Integrated T-cell receptor and costimulatory signals determine TGF-β-dependent differentiation and maintenance of Foxp3+ regulatory T cells

Foxp3-expressing Tregs play a non-redundant role in protecting against immune pathologies. Foxp3(+) Tregs can arise intra- and extra-thymically, however, the signals directing their differentiation and maintenance in the periphery are not well understood. We show that stimulation of mouse naïve CD4(+) T cells in vitro with optimal doses of anti-CD3/anti-CD28 resulted in high frequencies of Foxp3(+) T cells via a TGF-β-dependent mechanism. Addition of TGF-β and retinoic acid overcame the inhibition of Foxp3 expression observed during high-strength anti-CD3/anti-CD28 stimulation. Reducing the strength of TCR or costimulatory signals with inhibitors of mammalian target of rapamycin (mTOR) or MEK/ERK signalling also enhanced expression of Foxp3 in a TGF-β-dependent manner. Addition of TGF-β was further required to maintain Foxp3 expression in ex vivo derived Foxp3(+) Tregs upon prolonged anti-CD3/anti-CD28 signalling. Thus, induction/maintenance of Foxp3 expression by TGF-β is modulated by the integrated strength of TCR/costimulatory signals.

Unaltered neuronal and glial counts in animal models of magnetic seizure therapy and electroconvulsive therapy

Anatomical evidence of brain damage from electroconvulsive therapy (ECT) is lacking; but there are no modern stereological studies in primates documenting its safety. Magnetic seizure therapy (MST) is under development as a less invasive form of convulsive therapy, and there is only one prior report on its anatomical effects. We discerned no histological lesions in the brains of higher mammals subjected to electroconvulsive shock (ECS) or MST, under conditions that model closely those used in humans. We sought to extend these findings by determining whether these interventions affected the number of neurons or glia in the frontal cortex or hippocampus. Twenty-four animals received 6 weeks of ECS, MST, or anesthesia alone, 4 days per week. After perfusion fixation, numbers of neurons and glia in frontal cortex and hippocampus were determined by unbiased stereological methods. We found no effect of either intervention on volumes or total number or numerical density of neurons or glia in hippocampus, frontal cortex, or subregions of these structures. Induction of seizures in a rigorous model of human ECT and MST therapy does not cause a change in the number of neurons or glia in potentially vulnerable regions of brain. This study, while limited to young, healthy, adult subjects, provides further evidence that ECT and MST, when appropriately applied, do not cause structural damage to the brain.

Differential induction of CD94 and NKG2 in CD4 helper T cells. A consequence of influenza virus infection and interferon-gamma?

Influenza A virus causes worldwide epidemics and pandemics and the investigation of memory T helper (Th) cells that help maintain serological memory following infection is important for vaccine design. In this study we investigated CD94 and NKG2 gene expression in memory CD4 T-cell clones established from the spleens of C57BL/10 (H-2(b)) and BALB/c (H-2(d)) mice infected with influenza A virus (H3N2). CD94 and NKG2A/C/E proteins form heterodimeric membrane receptors that are involved in virus recognition. CD94 and NKG2 expression have been well characterized in natural killer (NK) and cytotoxic T cells. Despite CD94 being potentially an important marker for Th1 cells involved in virus infection, however, there has been little investigation of its expression or function in the CD4 T-cell lineage and no studies have looked at in-vivo-generated Th cells or memory cells. We show in this study that in-vivo-generated CD4 Th1 cells, but not Th2 cells, exhibited full-length CD94 and NKG2A gene expression following activation with viral peptide. For NKG2A, a novel 'short' (possibly redundant) truncated isoform was detectable in a Th2 cell clone. Another member of the NK receptor family, NKG2D, but not NKG2C or E, was also differentially expressed in Th1 cells. We show here that CD94 and NKG2A may exist as multiple isoforms with the potential to distinguish helper T-cell subsets.

Hippocampal neuron and glial cell numbers in Parkinson's disease--a stereological study

Hippocampal atrophy and neuron loss are early and reproducible findings in Alzheimer's disease, and recent magnetic resonance imaging studies indicate that hippocampal atrophy may also be present in Parkinson's disease (PD). To determine whether or not cell loss occurs in PD, we estimated the total neuron and glial cell numbers as well as the total volume unilaterally in the hippocampi of eight demented PD patients and eight control subjects. Cell numbers were estimated in the neuron-containing layers of CA1, CA2-(3), CA4, the dentate gyrus, and subiculum using the optical-fractionator technique. The Cavalieri method was used to estimate the volume of the total hippocampus and its subregions. We did not find significant differences in cell numbers or volumes in PD brains when compared with control subjects. Our results thus indicate that hippocampal atrophy and cell loss are not necessarily involved in the memory impairment and dementia observed in PD.

Identification of a Macrophage-Specific Chromatin Signature in the IL-10 Locus

The molecular mechanisms that regulate expression of the immunosuppressive cytokine IL-10 remain poorly understood. In this study, by measuring sensitivity to DNase I digestion, we show that production of IL-10 by primary mouse bone marrow-derived macrophages stimulated through pattern recognition receptors was associated with chromatin remodeling of the IL-10 locus. We also demonstrate that the IL-10 locus is remodeled in primary Th2 cells and IL-10-producing regulatory T cells that have been differentiated in vitro. Strikingly, a novel DNase I-hypersensitive site (HSS-4.5) was identified in stimulated macrophages, but not in T cells. We show that hyperacetylated histones were recruited to this site in stimulated macrophages. Furthermore, HSS-4.5 is highly conserved and contains a putative NF-kappaB binding site. In support of a function for this site, NF-kappaB p65/RelA was recruited to HSS-4.5 in vivo and its activation was required for optimal IL-10 gene expression in LPS-stimulated macrophages.

IL-10-Secreting Regulatory T Cells Do Not Express Foxp3 but Have Comparable Regulatory Function to Naturally Occurring CD4+CD25+ Regulatory T Cells

Regulatory T cells (T(Reg)) control immune responses to self and nonself Ags. The relationship between Ag-driven IL-10-secreting T(Reg) (IL-10-T(Reg)) and naturally occurring CD4(+)CD25(+) T(Reg) is as yet unclear. We show that mouse IL-10-T(Reg) obtained using either in vitro or in vivo regimens of antigenic stimulation did not express the CD4(+)CD25(+) T(Reg)-associated transcription factor Foxp3. However, despite the absence of Foxp3 expression, homogeneous populations of IL-10-T(Reg) inhibited the in vitro proliferation of CD4(+)CD25(-) T cells with a similar efficiency to that of CD4(+)CD25(+) T(Reg). This inhibition of T cell proliferation by IL-10-T(Reg) was achieved through an IL-10-independent mechanism as seen for CD4(+)CD25(+) T(Reg) and was overcome by exogenous IL-2. Both IL-10-T(Reg) and CD4(+)CD25(+) T(Reg) were similar in that they produced little to no IL-2. These data show that Foxp3 expression is not a prerequisite for IL-10-T(Reg) activity in vitro or in vivo, and suggest that IL-10-T(Reg) and naturally occurring CD4(+)CD25(+) T(Reg) may have distinct origins.

Neurons of a limited subthalamic area mediate elevations in cortical cerebral blood flow evoked by hypoxia and excitation of neurons of the rostral ventrolateral medulla

Sympathoexcitatory reticulospinal neurons of the rostral ventrolateral medulla (RVLM) are oxygen detectors excited by hypoxia to globally elevate regional cerebral blood flow (rCBF). The projection, which accounts for >50% of hypoxic cerebral vasodilation, relays through the medullary vasodilator area (MCVA). However, there are no direct cortical projections from the RVLM/MCVA, suggesting a relay that diffusely innervates cortex and possibly originates in thalamic nuclei. Systematic mapping by electrical microstimulation of the thalamus and subthalamus revealed that elevations in rCBF were elicited only from a limited area, which encompassed medial pole of zona incerta, Forel's field, and prerubral zone. Stimulation (10 sec train) at an active site increased rCBF by 25 +/- 6%. Excitation of local neurons with kainic acid mimicked effects of electrical stimulation by increasing rCBF. Stimulation of the subthalamic cerebrovasodilator area (SVA) with single pulses (0.5 msec; 80 microA) triggered cortical EEG burst-CBF wave complexes with latency 24 +/- 5 msec, which were similar in shape to complexes evoked from the MCVA. Selective bilateral lesioning of the SVA neurons (ibotenic acid, 2 microg, 200 nl) blocked the vasodilation elicited from the MCVA and attenuated hypoxic cerebrovasodilation by 52 +/- 12% (p < 0.05), whereas hypercarbic vasodilation remained preserved. Lesioning of the vasodilator site in the basal forebrain failed to modify SVA-evoked rCBF increase. We conclude that (1) excitation of intrinsic neurons of functionally restricted region of subthalamus elevates rCBF, (2) these neurons relay signals from the MCVA, which elevate rCBF in response to hypoxia, and (3) the SVA is a functionally important site conveying vasodilator signal from the medulla to the telencephalon.

The medullary cerebrovascular vasodilator area mediates cerebrovascular vasodilation and electroencephalogram synchronization elicited from cerebellar fastigial nucleus in Sprague-Dawley rats

We investigated whether the medullary cerebrovasodilator area (MCVA), a region of ventral medulla mediating elevations of regional cerebral blood flow (rCBF) and electroencephalogram (EEG) synchronization elicited in cerebral cortex from stimulation of reticulospinal neurons of rostral ventrolateral medulla (RVLM), also mediates comparable responses from the cerebellar fastigial nucleus (FN). In spinalized rats, electrical stimulation of MCVA, RVLM or FN elevated rCBF and synchronized the EEG. The FN-evoked responses were significantly attenuated or blocked by bilateral lesions of MCVA. The MCVA is a novel region of medullary reticular formation mediating actions of medullary and cerebellar centers on rCBF and EEG to link visceral centers of brainstem and cerebral cortex.

Process and product development in the manufacturing of molecular therapeutics

In the development of molecular therapies, a great deal of attention has focused on tissue targets, gene delivery vectors, and expression cassettes. In order to become an approved therapy, however, a molecular therapeutic has to pass down the same product registration pathway as any other biological product. Moving from research into industrial production requires careful attention to regulatory, manufacturing and quality concerns. Early work on developing and characterizing robust and scaleable manufacturing processes will ultimately be rewarded by ease of implementation as the product is successful in clinical trials. Regulatory agencies require solid process and product characterization studies to demonstrate control and understanding of the molecular therapeutic. As the gene therapy industry matures, standards will continue to rise, creating an industry that is capable of producing safe, high-quality and effective therapies for many of the world's most difficult disease targets.

Process and product development in the manufacturing of molecular therapeutics

In the development of molecular therapies, a great deal of attention has focused on tissue targets, gene delivery vectors, and expression cassettes. In order to become an approved therapy, however, a molecular therapeutic has to pass down the same product registration pathway as any other biological product. Moving from research into industrial production requires careful attention to regulatory, manufacturing and quality concerns. Early work on developing and characterizing robust and scaleable manufacturing processes will ultimately be rewarded by ease of implementation as the product is successful in clinical trials. Regulatory agencies require solid process and product characterization studies to demonstrate control and understanding of the molecular therapeutic. As the gene therapy industry matures, standards will continue to rise, creating an industry that is capable of producing safe, high-quality and effective therapies for many of the world's most difficult disease targets.

Characteristics and outcomes of a home and community-based neurorehabilitation programme

The potential clinical and financial advantages of providing neurorehabilitation directly in patients' homes and communities have recently been discussed. However, the specific characteristics and outcomes of a coordinated, interdisciplinary, home-based programme does not currently exist in the rehabilitation literature. The present paper presents patient demographics, type and intensity of services provided, satisfaction measures, and clinical outcomes for 77 brain injured individuals in an attempt to begin to define and evaluate this new level of care. Additionally, the challenges of conducting home-based rehabilitation, and needs for further research are discussed.

Consequences of the delayed diagnosis of ataxia-telangiectasia

OBJECTIVES

Ataxia-telangiectasia (AT) is a rare, autosomal recessive neurodegenerative disorder in which the diagnosis is obvious when ataxia and telangiectasia are both present. However, the diagnosis can be made upon the onset of ataxia and before the appearance of telangiectasia if confirmed by laboratory tests. Early diagnosis is important for genetic counseling, appropriate care, and avoidance of unnecessary tests. The purpose of this study is to identify factors responsible for delays in the diagnosis of AT.

DESIGN

The records of all patients seen at the Ataxia-Telangiectasia Clinical Center from July 1, 1995 to April 1, 1997 were reviewed to determine age of onset of gait abnormality, recognition of telangiectasia, and diagnosis.

RESULTS

In 48 patients with AT, who were the index cases in their respective families, the median age of diagnosis (78 months) occurred after the onset of gait abnormalities (15 months) and closely corresponded to the development of telangiectasia (72 months). In the majority of cases (34/48), telangiectasia appeared before the diagnosis was established. The most common misdiagnosis was cerebral palsy (29/48 cases). Twenty-one children (4 with AT) were born after the start of symptoms in the index case, but before the establishment of a diagnosis.

CONCLUSIONS

The term AT, although a concise and memorable label for the disorder, is also a barrier to early diagnosis. We recommend the use of routine serum alpha-fetoprotein testing for all children with persistent ataxia.

Regional and temporal differences in real-time dopamine efflux in the nucleus accumbens during free-choice novelty

To assess dopamine efflux during novelty-seeking behavior in rats, fast-scan cyclic voltammetry in the nucleus accumbens was combined with free-choice entry into a novel environment. Cyclic voltammograms, confirmed by in vitro testing, revealed that entry into novel, but not familiar, surroundings increased dopamine efflux in a regionally and temporally distinct pattern. Whereas dopamine failed to change in the core region of the accumbens and overlying neostriatum, an abrupt increase occurred in accumbal shell, a limbic-related area implicated in goal-directed behavior. Although the dopamine response was confined to the brief period of entry into novelty (approximately 8 s duration), a less rapid and more persistent dopamine change (> 20 s duration) occurred in the shell-core transition zone, the so-called shore. These results suggest that novelty mimics other positively reinforcing stimuli in enhancing dopamine transmission in the nucleus accumbens, but the regional and temporal heterogeneity of this effect may represent different aspects of accumbal dopamine function.

Real-time measurement of electrically evoked extracellular dopamine in the striatum of freely moving rats

The real-time measurement of electrically evoked dopamine was established in brain extracellular fluid of freely moving rats. Dopamine was monitored by fast-scan cyclic voltammetry at carbon fiber microelectrodes lowered into the striatum by means of a detachable micromanipulator. A stimulating electrode, previously implanted in the substantia nigra, was used to evoke striatal dopamine efflux. Evoked extracellular dopamine was both current and frequency dependent. When low current intensities (+/-125 microA) and frequencies (10-20 Hz) were applied, detectable levels of dopamine were elicited without a perceptible behavioral response. Reproducible concentrations of extracellular dopamine could be evoked in the same rat for at least 2 months. These concentrations, moreover, were significantly higher in freely moving rats compared with rats anesthetized with Equithesin. Analysis of measured curves for dopamine uptake and release rates revealed that anesthesia inhibits release but does not affect uptake. It is concluded that (a) fast-scan cyclic voltammetry at carbon fiber microelectrodes is a viable technique for the measurement of electrically evoked dopamine in brain extracellular fluid of freely moving rats, (b) it is possible to determine in situ rate constants for dopamine release and uptake from these temporally and spatially resolved measurements of levels of dopamine, and (c) transient changes in extracellular dopamine levels elicited by electrical stimulation are affected by anesthesia.

Chloroquine augments the binding of insulin to its receptor

The effect of chloroquine on the interaction of insulin with its receptor has been investigated under both equilibrium and non-equilibrium conditions. Chloroquine was found to augment insulin binding in a pH-dependent manner between pH 6.0 and pH 8.5, with the maximum occurring at approximately pH 7.0. Analysis of the equilibrium binding data in terms of independent binding sites gave equivocal results but suggested an increase in the high-affinity component. Analysis using the negative co-operativity binding model of De Meyts, Bianco and Roth [J. Biol. Chem. (1976) 251, 1877-1888] suggested that the affinity at both high and low occupancy was increased equally. The kinetics of association of insulin with the plasma-membrane receptor indicated that, although the net rate of association increased in the presence of chloroquine, this was due to a reduction in the dissociation rate rather than an increase in the association rate. This was confirmed by direct measurement of the rates of dissociation. Dissociation was found to be distinctly biphasic, with fast and slow components. Curve fitting suggested that the decrease in dissociation rate in the presence of chloroquine was not due to a decrease in either of the two dissociation rate constants, but rather to an increase in the amount of insulin dissociating by the slow component. It was also found that the increase in dissociation rate in the presence of excess insulin, ascribed to negative co-operativity, could be accounted for by an increase in the amount of insulin dissociating by the faster pathway, rather than by an increase in the dissociation rate constant. Thus chloroquine appears to have the opposite effect to excess insulin, and evidence was found for the induction of positive co-operativity in the insulin-receptor interaction at high chloroquine concentrations. Evidence was also found for the presence of low-affinity chloroquine binding sites with binding parameters similar to the concentration dependence of the chloroquine-induced augmentation of insulin binding.

Amphetamine, cocaine, and dizocilpine enhance performance on a lever-release, conditioned avoidance response task in rats

A lever-release version of the conditioned avoidance response (CAR) task was used to assess the behavioral effects of several psychomotor stimulants in rats. The indirect dopamine agonists, d-amphetamine (0.1 and 0.25 mg/kg) and cocaine (7.5 and 15 mg/kg), enhanced performance on this task. Both drugs increased percent avoidance responses and decreased avoidance latency. A higher dose of amphetamine (0.5 mg/kg) also decreased avoidance latency but failed to improve percent avoidance. Similar effects were seen at low (0.01 and 0.025 mg/kg) and high (0.05 mg/kg) doses of dizocilpine (MK-801), a stimulant that acts as a noncompetitive antagonist of N-methyl-d-aspartate (NMDA) glutamate receptors. When combined with haloperidol (0.1 mg/kg), a dopamine antagonist, amphetamine (0.25 mg/kg) and dizocilpine (0.025 mg/kg) had differential effects on the lever-release CAR task. Thus, amphetamine-haloperidol was significantly better than haloperidol alone on percent avoidance but not on avoidance latency, whereas dizocilpine-haloperidol had the opposite effect: significantly better than haloperidol alone on avoidance latency but not on percent avoidance. Taken together, these results provide further support for dopaminergic mechanisms in CAR performance but suggest an opposing glutamatergic influence.

Enamel pretreatment with sodium hypochlorite to enhance bonding in hypocalcified amelogenesis imperfecta: case report and SEM analysis

Bonding composite resin to enamel of teeth affected by amelogenesis imperfecta (AI) is often problematic, especially in cases with poorly mineralized, friable enamel. Difficulty in bonding hypomineralized enamel can significantly limit the restorative and orthodontic treatment options for AI patients. In this report, we document a novel approach to bonding AI enamel by pretreating the tooth surface with 5% sodium hypochlorite (NaOCl), resulting in improved bonding of an orthodontic bracket to a previously impacted maxillary canine.

A model of insulin distribution and uptake in the perfused rat liver

Indicator dilution curves of 51Cr-EDTA and 125I-insulin injected into perfusate entering the rat liver in vivo are used as a basis for developing a mathematical model of insulin distribution and uptake within the organ. EDTA is not taken up by liver cells and therefore serves as a "volume marker" whose dilution curve reflects the characteristics of perfusate flow through the organ and through the cannulae. These two components are modelled separately but the same approach is used in each case, that is, the minimum number of delayed exponential terms sufficient to reproduce the dilution curves is determined and used as the basis for modelling. This allows the cannula, vascular and sinusoidal volumes to be identified and described as corresponding compartmental configurations. The shape of the insulin dilution curve is additionally influenced by binding to, and uptake by, liver cells. Binding of insulin to receptors on hepatocyte plasma membranes and subsequent internalization of the insulin-receptor complex is modelled by the introduction of additional compartments but this is found to be insufficient unless non-specific binding is also taken into account. The accuracy of determination of the rate constants for insulin-receptor dissociation and for endocytosis is improved by a sudden reduction in the pH of the perfusate about 100 sec after injection of the insulin bolus. This releases any residual receptor bound insulin and is modelled by a sudden shift in the insulin-receptor dissociation rate constant. Matching of the complete model to individual pairs of 51Cr-EDTA and 125I-insulin dilution curves allows vascular and sinusoidal volumes to be determined together with the binding and endocytic rate constants. Use of the model to investigate the effect of substances that modify these rate constants is briefly illustrated in the case where the liver is preperfused with 5 mM indomethacin. The model can also be used to simulate the internal distribution and uptake of insulin with any nominated input function and any set of parameters; this is illustrated by comparing the impulse response in the normal case and that in which indomethacin has been preperfused. Although the present study is confined to insulin, the model and methodology that is developed should be applicable to other ligands for which the hepatocyte carries specific receptors.

Indomethacin inhibits endocytosis and degradation of insulin

Indomethacin inhibits autophosphorylation of the insulin receptor. The lack of a consensus as to whether phosphorylation of the insulin receptor is necessary for its endocytosis prompted an investigation into the effects of indomethacin on the uptake and subcellular processing of insulin in the perfused rat liver. Indomethacin did not affect total uptake of insulin by the liver, but there was a concentration dependent inhibition of transfer from the plasma membrane to the endosomes (1mM, 32% inhibition; 5mM, 90% inhibition). Compartmental analysis showed the endocytic rate constant to be inhibited by 82% at 5mM indomethacin (0.0084 to 0.0015 sec-1). The similarity between the level of inhibition of autophosphorylation and the inhibition of endocytosis suggest that phosphorylation of the receptor is necessary for endocytosis. Indomethacin at 5mM completely abolished efflux of insulin degradation products from the perfused liver, suggesting that internalisation is an absolute requirement for degradation.

Developmental approach to pediatric neurogenic dysphagia

The approach to children with neurogenic dysphagia is unique due to their development, growth, and behavior. Multiple streams of development (cognitive, oral-motor, fine and gross motor) have direct and indirect effects on feeding. Provision of an appropriate feeding program requires that the multiple needs, abilities, and disabilities of each child be assessed and managed appropriately.

Hepatic processing of insulin. Characterization of differential inhibition by weak bases

The effect of selected weak bases on the subcellular distribution and processing of internalized insulin by the liver has been studied. The effect of these bases on both the degradation products formed and on the kinetics of degradation have also been studied. 1. Methylamine, ammonium chloride and dansyl cadaverine but not chloroquine reduce the total amount of insulin endocytosed. 2. Ammonium chloride, dansyl cadaverine and chloroquine but not methylamine inhibit subsequent degradation and/or translocation of degradation products. 3. None of the weak bases changed the species of the degradation products found within the endocytic vesicles. 4. Kinetic analysis of intravesicular degradation indicates that dissociation from the receptor is the rate-limiting process in degradation. 5. Chloroquine and dansyl cadaverine but not methylamine or ammonium chloride showed specific inhibition of insulin degradation in isolated endocytic vesicles. 6. The effect of chloroquine and dansyl cadaverine on the kinetics of degradation suggest that they are acting by switching the receptor into a tight-binding conformation thereby slowing dissociation.

Ultraviolet light induces different spectra of lacI sequence changes in vegetative and conjugating cells of Escherichia coli

We have analyzed the nucleotide sequence changes responsible for mutations from lacIs to lacI- induced in ultraviolet light-irradiated, excision-deficient cells. Irradiated cells were either used as donors in the conjugational transfer of an F' lacIs plasmid to SOS-induced, excision-deficient recipients or allowed to continue vegetative growth. Although the types and proportions of premutagenic lesions are likely to have been very similar in these two circumstances, analysis of the sequence data shows that different spectra of mutations were induced. In vegetative cells there were about equal numbers of transitions and transversions, but transitions outnumbered transversions by about three to one in exconjugants. About 90% of the single nucleotide substitutions could be assigned to a bipyrimidine target sequence in both sets of data, but they differed with respect to the location of the substitution: more or less equal numbers were found at the 3' and 5' sites of the probable bipyrimidine target in vegetative cells, but in exconjugants over 80% were at the 3' site. It is also possible that mutations were targeted more commonly at T-C sequences in exconjugants than in vegetative cells, but the evidence for this is less secure. We conclude that these results reflect some dissimilarity between vegetative cells and exconjugants in the way damaged DNA is replicated or lesions tolerated, but the particular features of these processes responsible for the different mutational spectra have not yet been identified.

UmuC function is not essential for the production of all targeted lacI mutations induced by ultraviolet light

Up to a quarter or more of the normal yield of lacI- mutations could be induced by ultraviolet light in a uvrA6 umuC122:: Tn5 strain if they were detected by plating on 5-bromo-4-chloro-3-indolyl-beta-D-galactoside medium, where all surviving cells can form colonies. Using phenyl beta-D-galactoside selection, which curtails post-irradiation growth, only low yields of mutations were induced. Nucleotide sequence analysis of 134 spontaneous and 145 ultraviolet light-induced mutations shows that broadly similar kinds of mutations were induced in the umuC mutant and its uvrA6 umuC+ counterpart. In particular, these data offer no reason for believing that most of the mutations induced in the umuC mutant were other than normal, targeted events. We conclude that UmuC function, rather than being essential, facilitates recovery and specifically, following the model of Bridges & Woodgate, that it facilitates the prompt resumption of chain elongation.

Specific inhibition of tyrosine kinase activity by an antibody to the v-ros oncogene product

Antibodies present in two peritoneal exudates of rats bearing abdominal tumors induced by UR2-transformed rat cells were characterized. The ability to immunoprecipitate p68gag-ros and to inhibit the protein and phospholipid kinase activities of this protein was investigated. One of the exudates specifically inhibited tyrosyl phosphorylation by p68gag-ros but not the activity of other known tyrosyl kinases, such as p150gag-fps of UR1 avian sarcoma virus, p60src, and the insulin receptor. It precipitated p68gag-ros but not Pr76 or other gag-related proteins from UR2-infected cells. Phosphorylation of phosphatidylinositol was not affected by this exudate, suggesting that this activity is not intrinsic to p68gag-ros. Another exudate precipitated p68gag-ros but not gag-related proteins from UR2-infected cells or p140gag-fps from Fujinami sarcoma virus-infected cells. These results demonstrated that the antibodies in these exudates recognized epitopes present in the ros portion of the fused protein p68gag-ros, but only one of the two exudates inhibited the intrinsic tyrosyl kinase of p68gag-ros.

Transfection and recombination with molecularly cloned derivatives of avian sarcoma virus UR2

A cloned version of avian sarcoma virus UR2, plasmid pKD6, which includes the full, nonpermuted proviral sequence between two LTR regions, has been prepared. The plasmid is biologically active in transfection experiments, even when intact. Two transformation-defective mutants with nonoverlapping deletions within the transforming gene ros were constructed from pKD6. These mutants recombine to produce transforming virus when mixed DNA from both is used to transfect chick embryo fibroblasts along with helper virus DNA. However, recombination was not readily detected when cells were coinfected with fluids harvested from cultures separately transfected with DNA from each mutant. This, and marker rescue experiments with a temperature-sensitive mutant of UR2 defective in transformation but able to replicate, suggest that deletion mutants of UR2 do not propagate efficiently.

T1 pip: a mutant which affects packaging initiation and processive packaging of T1 DNA

The pip mutation of phage T1 is located between the tar (gene 2.5) and am6 (gene 3) mutations in the region of the T1 genome which codes for early functions. The tar and pip mutations are additive in increasing the efficiency of transduction by T1. When T1 carries the pip mutation the initiation of DNA packaging by the phage at the non-T1, esp-lambda site is more efficient than when the phage is pip+; the small average burst size of 8 to 10 by T1pip suggests that pip causes a reduction in the efficiency with which T1 utilizes pac, the normal packaging initiation site of the phage. The presence of the BglII-D fragment (cut at one end at pac and the other by BglII) after digestion of T1pip DNA by BglII shows that T1pip continues to initiate DNA packaging at pac. The increased molarity of BglII-D coupled with the absence of the BglII-C fragment (which contains DNA on both sides of pac and can only be cut from processively packaged genomes) shows that T1pip packages only genomes which are initiated at pac and is defective in processive packaging.

Untargeted mutagenesis induced by UV in the lacI gene of Escherichia coli

Using a nonselective method, we have estimated the proportion of untargeted mutations in the lacI gene of E. coli by transferring either irradiated or unirradiated F' pro lac plasmids from an excision deficient donor to an excision deficient pro lac deleted recipient that had been irradiated and allowed to induce recA dependent functions for 30 min. We find that about 10 percent of the mutations induced by either 3.5 Jm-2 or 7 Jm-2 UV are untargeted.

Conjugation-dependent enhancement of induced and spontaneous mutation in the lacI gene of E. coli

The frequency of lac mutations induced in an F'lacIS plasmid, transferred by conjugation from UV-irradiated, excision-deficient donors to excision-deficient, delta pro lac recipients, is 2-3 fold higher than that typical of nonmating cells which contain the plasmid. These additional induced mutations can probably be ascribed to errors made during the first, or repliconation, synthesis that takes place in the recipient during the course of plasmid transfer. We also find that spontaneous mutation rates are enhanced in conjugating cells, indicating that fewer errors are corrected, or more made, during transfer replication.

Identity of the photoproduct that causes lacI mutations in UV-irradiated Escherichia coli

Estimates of the capacity of photoreactivation to act specifically on premutational lesions were obtained by conjugational transfer of an F' lac plasmid from a UV-irradiated, photoreactivated donor to a delta (pro-lac) recipient that had been UV irradiated and allowed to induce SOS functions for 30 min. This treatment reduced the frequency of induced lacI mutations by 70 to 80%, indicating that cyclobutane dimers cause most mutations in this system.

Characterization of insulin uptake into subcellular fractions of perfused rat liver using two different iodinated tracers

The binding and uptake of insulin in perfused rat liver has been investigated with specifically labelled 125I-A14-tyrosyl insulin as a tracer and compared with a commercially available iodo-insulin preparation. The commercial preparation did not show saturation uptake kinetics and the clearance from the perfusate remained low and constant throughout a wide concentration range. A14 labelled insulin showed saturation kinetics and high clearance at low carrier concentration, falling rapidly with increasing carrier concentration and reaching a steady state value of 1 ml/min. These results emphasize the importance of using specifically labelled insulin in physiological and biochemical studies of hepatic insulin metabolism. Perfusion with A14 tyrosine-labelled insulin at 4 degrees C showed apparent saturation with binding to the plasma membrane fraction. Perfusion at 37 degrees C also showed apparent saturation with uptake predominantly to the ligandosome fraction. These results implicate the plasma membrane-ligandosome pathway in the hepatic uptake of insulin at both physiological and pharmacological concentrations of the hormone.

Requirement for protein synthesis for survival of unmodified bacteriophage T1 in a restricting host

At high multiplication of infection, a substantial fraction of restricting cells (P1 lysogens) could be productively infected by unmodified coliphage T1 (T1.0) provided that protein synthesis was uninhibited during the first 5 min of infection. Successful infection under restricting conditions was accompanied by more genetic recombination than was seen under nonrestricting host, the recombination frequency declined for markers on T1.0 genomes; no effect was seen on recombination between markers on modified (T1.P) genomes. This suggested that recombination between unmodified genomes may be essential for their survival under conditions of host restriction. In a restricting host, genetic markers on T1.0 could recombine with T1.P even when the rescuing phage was added 6 min after T1.0 infection. However, even marker rescue recombination was diminished when protein synthesis was inhibited during early infection. Since DNA restriction is an early event, protein synthesis may be required soon after infection of a restricting host by T1.0 in order to preserve restriction-damaged DNA in a form that can participate in recombination. Experiments are also described that rule out some possibilities for the role of such a protein(s).

Studies on recombination in heterologous crosses of Rous sarcoma virus

Ts mutants in src from the Prague and Schmidt-Ruppin strains of Rous sarcoma virus (RSV) were used to superinfect chicken and quail cells chronically infected with the Bryan strain of RSV. No wild-type recombinants and few double-defective virions were produced. These results indicate that genetic recombination does not occur with high frequency in these heterologous crosses even if all infectious virus is derived from doubly infected cells.

Genes of coliphage T1 whose products promote general recombination

The RecE bacterial recombination pathway, expressed in strains carrying a sbcA mutation, can substitute for the function of gene 4 of phage T1. RecE will also substitute for the function of a newly discovered phage gene, 3.5. Like mutants in gene 4, gene 3.5 mutants have a DA (DNA synthesis arrest) phenotype under nonpermissive conditions. In addition to their effects on DNA synthesis, mutations in genes 3.5 and 4 profoundly depress recombination in T1. Inhibition of DNA synthesis by nalidixic acid does not effect the frequency of recombinants among the small population of progeny phage that are produced. Isolation of T1 mutants dependent on the RecE function has yielded additional mutants specifically in genes 3.5 and 4. Together, these results are interpreted to mean that these two phage genes encode components of a general recombination system, referred to as T1 Grn. During replication of T1 in conventional hosts the essential function of this system is to provide for the formation, via recombination, of concatameric DNA molecules, which are the substrates for the packaging of DNA into T1 heads.

Exclusion of bacteriophage T1 by bacteriophage lambda. II. Synthesis of T1-specific macromolecules under N-mediated excluding conditions

The results of experiments investigating T1 macromolecular synthesis under N-mediated excluding conditions failed to demonstrate a substantial alteration in the T1 mRNA production in excluding cultures at any stage in the T1 infectious cycle. The number of T1 DNA sequences in the excluding culture was found to be one-third to one-half that found in T1-infected cultures. The most severe reduction in T1-specific macromolecules was seen in protein synthesis. Total incorporation of labeled amino acids was reduced sixfold, and gel experiments confirmed that the T1-specific proteins capable of detection are reduced in excluding cells.

Recombination in bacteriophage T1 in the presence of host restriction

When unmodified phage T1 infects restricting host cells at high multiplicities of infection, there is an increase in recombination frequency in all regions of the T1 map compared to the level of recombination in standard crosses when short distances are examined. The enhancement of recombination frequency is not uniform for all regions but is greatest for markers near the center of the map and not so great for markers near the ends. Crosses between markers at the extremities of the map show that there is no increase in recombination frequency under restriction conditions. An examination of phage T1 heterozygotes suggests that an increase of ends created by the process of P1 restriction increases recombination. When T1 crosses are done in the absence of host restriction, recombination defects in the host have no effect on phage recombination and we conclude that phage T1 codes for its own recombination genes. Host recombination functions are also dispensable for the recombination occurring during infection of restricting host cells by unmodified phage at high multiplicities of infection.

Transduction of bacteriophage lambda by bacteriophage T1

When bacteriophage T1 was grown on bacteriophage lambda-lysogenic cells, phenotypically mixed particles were formed which had the serum sensitivity, host range, and density of T1 but which gave rise to lambda phage. T1 packaged lambda genomes more efficiently both when the length of the prophage was less than that of wild-type lambda and when the host cell was polylysogenic. Expression of the red genes of lambda or the recE system of Escherichia coli during T1 growth enhanced pickup of lambda by T1, whereas packaging was reduced in recB cells. If donors were singly lysogenic, the expression of transduced lambda genomes as a PFU required lambda-specified excisive recombination, whereas lambda genomes transduced from polylysogens required only lambda- or E. coli-specified general recombination to give a productive infection.

Exclusion of bacteriophage T1 by bacteriophage lambda. I. Early exclusion requires lambda N gene product and host factors involved in N gene expression

Two modes of exclusion of T1 by lambda are distinguished. "Early" exclusion depends on gene N, but not on gene Q. It is at least partially ineffective against T1am23. "Late" exclusion depends on gene Q and effects T1am23 as well as T1+. Early exclusion is a direct effect of N gene product, rather than N gene being required for the expression of some other lambda gene. Three host mutations, groN, nusA, and nusB, known to interfere with lambda replication by affecting N gene expression, also interfere with the ability of lambda to exclude T1.

Red system of bacteriophage lambda complements the growth of a bacteriophage T1 gene 4 mutant

The ability of phage lambda to complement the growth of T1am23, a T1 gene 4 mutant with a DNA arrest phenotype, has been shown to require both lambda Red functions, redX and redB. lambdagam function, however, is not required. Therefore, the lambda Red function can substitute for T1 gene 4 function. However, T1+ does not substitute for lambda Red in allowing lambda to grow in a polA host.

Physiological study of cooperative infection by restricted bacteriophage T1

The ability of certain phages to successfully infect a restricting host at a high multiplicity of infection is known as cooperative infection or cooperation. We have examined the ability of unmodified T1 (T1.0) to participate in cooperative infection in cells possessing the P1 restriction system. We have found that cooperation is dependent upon protein synthesis during the first few minutes after phage infection. However, we have been unable to attribute the necessary protein to a known T1 cistron. Degradation of the restricted T1 genome is approximately equally extensive whether cooperative infection occurs or whether it is blocked by chloramphenicol. It is postulated that an inducible host repair mechanism may be responsible for the phenomenon of cooperative infection.

Interactions between the vegetative states of phages lambda and T1

Bacteria containing phage lambda in the vegetative state were produced either by induction of lambda lysogens or by infection of sensitive cells with lambda. These cells were superinfected with T1, and assayed for the production of lambda, T1, or both. Although most of the cells produced only lambda or T1, approximately 10% of the infectious centers were dual yielders. Examination of the progeny phage produced by the population of mixedly-infected cells showed that there was little, if any, phenotypic mixing, as determined by adsorption phenotype. T1am mutants in a variety of T1 genes were tested for their ability to exclude lambda, but none were defective in this ability. One gene of T1, gene 4, can be complemented by lambda.