Engagement of the PD-1 immunoinhibitory receptor by a novel B7 family member leads to negative regulation of lymphocyte activation

PD-1 is an immunoinhibitory receptor expressed by activated T cells, B cells, and myeloid cells. Mice deficient in PD-1 exhibit a breakdown of peripheral tolerance and demonstrate multiple autoimmune features. We report here that the ligand of PD-1 (PD-L1) is a member of the B7 gene family. Engagement of PD-1 by PD-L1 leads to the inhibition of T cell receptor-mediated lymphocyte proliferation and cytokine secretion. In addition, PD-1 signaling can inhibit at least suboptimal levels of CD28-mediated costimulation. PD-L1 is expressed by antigen-presenting cells, including human peripheral blood monocytes stimulated with interferon gamma, and activated human and murine dendritic cells. In addition, PD-L1 is expressed in nonlymphoid tissues such as heart and lung. The relative levels of inhibitory PD-L1 and costimulatory B7-1/B7-2 signals on antigen-presenting cells may determine the extent of T cell activation and consequently the threshold between tolerance and autoimmunity. PD-L1 expression on nonlymphoid tissues and its potential interaction with PD-1 may subsequently determine the extent of immune responses at sites of inflammation.

Generation of polarized antigen-specific CD8 effector populations: reciprocal action of interleukin (IL)-4 and IL-12 in promoting type 2 versus type 1 cytokine profiles

We have generated primary effector populations from naive CD8 T cells in response to antigen and determined their patterns of cytokine secretion upon restimulation. The effect of exogenous factors on the effector generation was examined and compared with responses of antigen-specific CD4 effectors generated under comparable conditions. CD8 cells from bm1 mice were stimulated with C57BL/6 (B6) antigen presenting cells (APCs) bearing allogeneic class I and CD8 cells from female severe combined immunodeficiency (SCID) B6 mice, transgenic for a T cell receptor alpha/beta (TCR-alpha/beta) that recognizes H-Y on Db, were stimulated with APCs from male mice. In parallel, CD4 cells from bm12 mice were stimulated with alloantigen and CD4 cells from V beta 3/V alpha 11 TCR transgenics were stimulated with a peptide of pigeon cytochrome c on IEk. T cells from both transgenic mice were of naive phenotype whereas normal mice contained 10-20% memory cells. Effector CD8 populations generated were L-selectin low, CD45RB high, and CD44 high. Naive CD8 cells from SCID anti-H-Y mice made little or no cytokine immediately upon stimulation in contrast to naive CD4 which produced large amounts of interleukin 2 (IL-2). Both populations, however, generated primary effectors over 4-5 d that made substantial quantities of many cytokines upon restimulation. Both CD8 and CD4 effectors produced similar patterns of cytokines with alloantigen or specific antigen. Cytokines present during naive CD8 stimulation influenced the cytokine secretion profile of the effectors, as previously shown for CD4 cells, although secretion by CD8 effectors was generally lower than that of CD4 effectors. CD8 cells cultured with IL-2 alone made predominantly interferon gamma (IFN-gamma) and no IL-4 or IL-5, similar to CD4 cells. Priming with IFN-gamma increased IFN-gamma secretion from CD4 effectors, but had little if any effect on CD8 cells. In contrast, priming with IL-12 generated CD8 effectors, as well as CD4 effectors, producing elevated quantities of IFN-gamma, with similar levels from both the CD4 and CD8 populations. The presence of IL-4 during effector cell generation promoted synthesis of IL-4 and IL-5 from both CD8 and CD4 cells while downregulating IFN-gamma secretion. CD8 cells made only small amounts of IL-4, more than 100-fold less than CD4 cells, whereas significant levels of IL-5 were induced, only 3-10-fold lower than from CD4.(ABSTRACT TRUNCATED AT 400 WORDS)

Unequal death in T helper cell (Th)1 and Th2 effectors: Th1, but not Th2, effectors undergo rapid Fas/FasL-mediated apoptosis

T helper cell (Th) 1, but not Th2, effectors undergo rapid Fas/Fas ligand (FasL)-mediated, activation-induced cell death upon restimulation with antigen. Unequal apoptosis is also observed without restimulation, after a longer lag period. Both effectors undergo delayed apoptosis induced by a non-Fas-mediated pathway. When Th1 and Th2 effectors are co-cultured, Th2 effectors survive preferentially, suggesting the responsible factor(s) is intrinsic to each population. Both Th1 and Th2 effectors express Fas and FasL, but only Th2 effectors express high levels of FAP-1, a Fas-associated phosphatase that may act to inhibit Fas signaling. The rapid death of Th1 effectors leading to selective Th2 survival provides a novel mechanism for differential regulation of the two subsets.

Potential role of glycogen synthase kinase-3 in skeletal muscle insulin resistance of type 2 diabetes

Glycogen synthase (GS) activity is reduced in skeletal muscle of type 2 diabetes, despite normal protein expression, consistent with altered GS regulation. Glycogen synthase kinase-3 (GSK-3) is involved in regulation (phosphorylation and deactivation) of GS. To access the potential role of GSK-3 in insulin resistance and reduced GS activity in type 2 diabetes, the expression and activity of GSK-3 were studied in biopsies of vastus lateralis from type 2 and nondiabetic subjects before and after 3-h hyperinsulinemic (300 mU x m(-2) x min(-1))-euglycemic clamps. The specific activity of GSK-3alpha did not differ between nondiabetic and diabetic muscle and was decreased similarly after 3-h insulin infusion. However, protein levels of both alpha and beta isoforms of GSK-3 were elevated (approximately 30%) in diabetic muscle compared with lean (P < 0.01) and weight-matched obese nondiabetic subjects (P < 0.05) and were unchanged by insulin infusion. Thus, both basal and insulin-stimulated total GSK-3 activities were elevated by approximately twofold in diabetic muscle. GSK-3 expression was related to in vivo insulin action, as GSK-3 protein was negatively correlated with maximal insulin-stimulated glucose disposal rates. In summary, GSK-3 protein levels and total activities are 1) elevated in type 2 diabetic muscle independent of obesity and 2) inversely correlated with both GS activity and maximally insulin-stimulated glucose disposal. We conclude that increased GSK-3 expression in diabetic muscle may contribute to the impaired GS activity and skeletal muscle insulin resistance present in type 2 diabetes.

Interleukin 1 beta and corticotropin-releasing factor inhibit pain by releasing opioids from immune cells in inflamed tissue

Local analgesic effects of exogenous opioid agonists are particularly prominent in painful inflammatory conditions and are mediated by opioid receptors on peripheral sensory nerves. The endogenous ligands of these receptors, opioid peptides, have been demonstrated in resident immune cells within inflamed tissue of animals and humans. Here we examine in vivo and in vitro whether interleukin 1 beta (IL-1) or corticotropin-releasing factor (CRF) is capable of releasing these endogenous opioids and inhibiting pain. When injected into inflamed rat paws (but not intravenously), IL-1 and CRF produce antinociception, which is reversible by IL-1 receptor antagonist and alpha-helical CRF, respectively, and by the immunosuppressant cyclosporine A. In vivo administration of antibodies against opioid peptides indicates that the effects of IL-1 and CRF are mediated by beta-endorphin and, in addition, by dynorphin A and [Met]enkephalin, respectively. Correspondingly, IL-1 effects are inhibited by mu-, delta-, and kappa-opioid antagonists, whereas CRF effects are attenuated by all except a kappa-antagonist. Finally, IL-1 and CRF produce acute release of immunoreactive beta-endorphin in cell suspensions freshly prepared from inflamed lymph nodes. This effect is reversible by IL-1 receptor antagonist and alpha-helical CRF, respectively. These findings suggest that IL-1 and CRF activate their receptors on immune cells to release opioids that subsequently occupy multiple opioid receptors on sensory nerves and result in antinociception. beta-Endorphin, mu- and delta-opioid receptors play a major role, but IL-1 and CRF appear to differentially release additional opioid peptides.

Immune cell-derived beta-endorphin. Production, release, and control of inflammatory pain in rats

Localized inflammation of a rat's hindpaw elicits an accumulation of beta-endorphin-(END) containing immune cells. We investigated the production, release, and antinociceptive effects of lymphocyte-derived END in relation to cell trafficking. In normal animals, END and proopiomelanocortin mRNA were less abundant in circulating lymphocytes than in those residing in lymph nodes (LN), suggesting that a finite cell population produces END and homes to LN. Inflammation increased proopiomelanocortin mRNA in cells from noninflamed and inflamed LN. However, END content was increased only in inflamed paw tissue and noninflamed LN-immune cells. Accordingly, corticotropin-releasing factor and IL-1beta released significantly more END from noninflamed than from inflamed LN-immune cells. This secretion was receptor specific, calcium dependent, and mimicked by potassium, consistent with vesicular release. Finally, both agents, injected into the inflamed paw, induced analgesia which was blocked by the co-administration of antiserum against END. Together, these findings suggest that END-producing lymphocytes home to inflamed tissue where they secrete END to reduce pain. Afterwards they migrate to the regional LN, depleted of the peptide. Consistent with this notion, immunofluorescence studies of cell suspensions revealed that END is contained predominantly within memory-type T cells. Thus, the immune system is important for the control of inflammatory pain. This has implications for the understanding of pain in immunosuppressed conditions like cancer or AIDS.

Bacillus sporulation gene spo0H codes for sigma 30 (sigma H)

The DNA sequences of the spo0H genes from Bacillus licheniformis and B. subtilis are described, and the predicted open reading frames code for proteins of 26,097 and 25,447 daltons, respectively. The two spo0H gene products are 91% identical to one another and about 25% identical to most of the procaryotic sigma factors. The predicted proteins have a conserved 14-amino-acid sequence at their amino terminal end, typical of sigma factors. Antibodies raised against the spo0H gene product of B. licheniformis specifically react with RNA polymerase sigma factor protein, sigma 30, purified from B. subtilis. We conclude that the spo0H genes of B. licheniformis and B. subtilis code for sigma 30, now known as sigma H.

Distribution of peroxisome proliferator-activated receptors (PPARs) in human skeletal muscle and adipose tissue: relation to insulin action

AIMS/HYPOTHESIS

To evaluate the tissue distribution and possible role of the peroxisome proliferator-activated receptors (PPARs) in insulin action in fat and muscle biopsy specimens from lean, obese and subjects with Type II (non-insulin-dependent) diabetes mellitus.

METHODS

We measured PPAR alpha, PPAR beta (delta) and PPAR gamma protein expression by western blot analysis. The PPAR gamma protein was also measured in muscle before and after 3-h hyperinsulinaemic (300 mU.m-2.min-1) euglycaemic clamps.

RESULTS

The PPAR alpha protein was expressed preferentially in muscle relative to fat (more than sevenfold). The PPAR beta protein was similar in fat and muscle. The amount of PPAR gamma protein found in muscle was, on average, two-thirds of that present in fat. There was no statistically significant difference between non-diabetic and diabetic subjects in baseline (preclamp) muscle PPAR (alpha, beta or gamma) protein expression. Subgroup analysis showed, however, significantly higher PPAR gamma protein in the most insulin resistant diabetic subjects with glucose disposal rates of 3-6 mg.kg-1.min-1 compared with their age and weight matched counterparts with glucose disposal rates of 6-9 (147 +/- 23 vs 88 +/- 10 AU/microgram protein, p < or = 0.01 in diabetic and vs 94 +/- 15, p < or = 0.04 in non-diabetic subjects). Muscle PPAR gamma protein and glucose disposal rates were inversely correlated in diabetic subjects (r = -0.47, p < or = 0.05).

CONCLUSION/INTERPRETATION

All PPARs (alpha, beta or gamma) are present in skeletal muscle and adipose tissue with different relative distributions. The PPAR gamma protein is abundant in skeletal muscle as well as adipose tissue. The altered expression of skeletal muscle PPAR gamma is consistent with a role for this nuclear protein in the impaired insulin action of Type II diabetes.

Expression of corticotropin-releasing factor in inflamed tissue is required for intrinsic peripheral opioid analgesia

Immune cell-derived opioid peptides can activate opioid receptors on peripheral sensory nerves to inhibit inflammatory pain. The intrinsic mechanisms triggering this neuroimmune interaction are unknown. This study investigates the involvement of endogenous corticotropin-releasing factor (CRF) and interleukin-1beta (IL-1). A specific stress paradigm, cold water swim (CWS), produces potent opioid receptor-specific antinociception in inflamed paws of rats. This effect is dose-dependently attenuated by intraplantar but not by intravenous alpha-helical CRF. IL-1 receptor antagonist is ineffective. Similarly, local injection of antiserum against CRF, but not to IL-1, dose-dependently reverses this effect. Intravenous anti-CRF is only inhibitory at 10(4)-fold higher concentrations and intravenous CRF does not produce analgesia. Pretreatment of inflamed paws with an 18-mer 3'-3'-end inverted CRF-antisense oligodeoxynucleotide abolishes CWS-induced antinociception. The same treatment significantly reduces the amount of CRF extracted from inflamed paws and the number of CRF-immunostained cells without affecting gross inflammatory signs. A mismatch oligodeoxynucleotide alters neither the CWS effect nor CRF immunoreactivity. These findings identify locally expressed CRF as the predominant agent to trigger opioid release within inflamed tissue. Endogenous IL-1, circulating CRF or antiinflammatory effects, are not involved. Thus, an intact immune system plays an essential role in pain control, which is important for the understanding of pain in immunosuppressed patients with cancer or AIDS.

Mast cells and matrix degradation at sites of tumour invasion in rat mammary adenocarcinoma

Significant numbers of mast cells have been demonstrated histologically around the periphery of the invasive rat mammary adenocarcinoma 13672NF. The number of mast cells at microfoci along the tumour:host tissue junction was significantly greater than that found in normal mammary tissues, and few mast cells were detected within the tumour itself. Mast cell degranulation, often associated with disruption and lysis of the connective tissue matrix, was a common feature in later stages of tumour proliferation. When soluble products derived from purified rat peritoneal mast cells were added to monolayer cultures of rat stromal fibroblasts or tumour cells they stimulated a significant increase in total collagenase production, and the mast cell products were also capable of activating the latent collagenases thus produced. Histological examination indicated that degradation of local collagenous matrix was a common feature of mast cell degranulation, an observation possibly explained by the release of mast cell enzymes and/or the potential of this cell to modulate the expression of collagenolytic activity by surrounding cells. These observations suggest that, at least in some tumours, mast cells contribute to the connective tissue breakdown commonly associated with tumour invasiveness and metastatic spread.

Hallucinating symmetric protein assemblies

Deep learning generative approaches provide an opportunity to broadly explore protein structure space beyond the sequences and structures of natural proteins. Here, we use deep network hallucination to generate a wide range of symmetric protein homo-oligomers given only a specification of the number of protomers and the protomer length. Crystal structures of seven designs are very similar to the computational models (median root mean square deviation: 0.6 angstroms), as are three cryo-electron microscopy structures of giant 10-nanometer rings with up to 1550 residues and C33 symmetry; all differ considerably from previously solved structures. Our results highlight the rich diversity of new protein structures that can be generated using deep learning and pave the way for the design of increasingly complex components for nanomachines and biomaterials.

Helical (spiral) CT of the abdomen

Since its clinical introduction in the mid 1970s, techniques for CT have undergone many changes that have dramatically altered how CT scans are obtained. Helical (spiral) CT allows for faster acquisition of truly volumetric CT data than is possible with conventional scanners. Routine helical CT of the abdomen is now possible because of three major technical refinements: the development of the slip-ring gantry, improved detector efficiency, and greater tube cooling capability. This article reviews the technical principles that govern helical CT, the potential advantages and disadvantages of this technique, and initial clinical experience with helical CT of the abdomen.

Peroxisome proliferator-activated receptor (PPAR) gamma and retinoid X receptor (RXR) agonists have complementary effects on glucose and lipid metabolism in human skeletal muscle

AIMS/HYPOTHESIS

To determine the independent and potentially synergistic effects of agonists for PPAR gamma and RXR on glucose and lipid metabolism, as well as gene expression, in human skeletal muscle cell cultures.

METHODS

Fully differentiated myotubes from non-diabetic subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus were chronically (2 days) treated with LG100268 (4 mumol/l), an RXR agonist, or troglitazone (4.6 mumol/l), a PPAR gamma agonist or both, to determine the effects on glucose uptake, activity of glycogen synthase and palmitate oxidation.

RESULTS

The combination of both agents increased glucose uptake (60 +/- 9% compared to control subjects) but not either agent alone (16 +/- 9 and 26 +/- 6% for LG100268 and troglitazone, p < 0.01, respectively). The agent LG100268 alone had little effect on the activity of glycogen synthase but the effect of troglitazone increased with LG100268 (p < 0.05). With chronic exposure, LG100268 upregulated palmitate oxidation (53 +/- 12% increase, p < 0.005), in a way similar to troglitazone (68 +/- 23%, p < 0.005). Synergism was observed when both agonists were combined (146 +/- 38%, p < 0.005 vs either agent alone). Treatment with either agent led to about a twofold increase in the expression of fatty acid transporter (FAT/CD36). Troglitazone upregulated PPAR gamma protein expression, whereas LG100268 had no effect. Furthermore, neither LG100268 nor troglitazone had any effect on the protein expression of RXR isoforms or PPAR alpha.

CONCLUSION/INTERPRETATION

Co-activation of PPAR gamma and RXR results in additive or synergistic effects on glucose and lipid metabolism in skeletal muscle, but unlike troglitazone, LG100268 does not alter expression of its own receptor.

Oral cancer awareness of general medical and general dental practitioners

OBJECTIVE

To assess general medical practitioners' (GMPs') and general dental practitioners' (GDPs') awareness of prevention and early detection of oral cancer.

DESIGN

Cross-sectional questionnaire-based study.

SETTING

Primary care.

METHOD

Questionnaires were delivered to all GMPs and GDPs in Tayside, assessing oral examination habits, delivery of advice on oral cancer risk factors, knowledge of oral cancer risk factors and clinical appearance, preferred point of referral and requests for further information.

RESULTS

Response rates of 71% and 84% were obtained from GMPs and GDPs respectively. GMPs were less likely to examine patients' oral mucosa routinely, less likely to advise patients about risk factors for oral cancer, identified fewer risk factors for, and felt less confident about diagnosing oral cancer from clinical appearance than their dental counterparts. Seventy-one percent and 80% of GMPs and GDPs respectively requested further information about oral cancer.

CONCLUSION

Patients with oral lesions often present to their general medical practitioner. The incidence of oral cancer is rising in the United Kingdom, therefore the role of general medical practitioners in prevention and detection of oral cancer is becoming ever more important. This study highlights the need for improved education of general medical practitioners on oral cancer.

Supportive Care: An Indispensable Component of Modern Oncology

The advent of new cancer therapies, alongside expected growth and ageing of the population, better survival rates and associated costs of care, is uncovering a need to more clearly define and integrate supportive care services across the whole spectrum of the disease. The current focus of cancer care is on initial diagnosis and treatment, and end of life care. The Multinational Association of Supportive Care in Cancer defines supportive care as 'the prevention and management of the adverse effects of cancer and its treatment'. This encompasses the entire cancer journey, and necessitates involvement and integration of most clinical specialties. Optimal supportive care can assist in accurate diagnosis and management, and ultimately improve outcomes. A national strategy to implement supportive care is needed to acknowledge evolving oncology practice, changing disease patterns and the changing patient demographic.

Tumourigenic non-small-cell lung cancer mesenchymal circulating tumour cells: a clinical case study

BACKGROUND

Over the past decade, numerous reports describe the generation and increasing utility of non-small-cell lung cancer (NSCLC) patient-derived xenografts (PDX) from tissue biopsies. While PDX have proven useful for genetic profiling and preclinical drug testing, the requirement of a tissue biopsy limits the available patient population, particularly those with advanced oligometastatic disease. Conversely, 'liquid biopsies' such as circulating tumour cells (CTCs) are minimally invasive and easier to obtain. Here, we present a clinical case study of a NSCLC patient with advanced metastatic disease, a never smoker whose primary tumour was EGFR and ALK wild-type. We demonstrate for the first time, tumorigenicity of their CTCs to generate a patient CTC-derived eXplant (CDX).

PATIENTS AND METHODS

CTCs were enriched at diagnosis and again 2 months later during disease progression from 10 ml blood from a 48-year-old NSCLC patient and implanted into immunocompromised mice. Resultant tumours were morphologically, immunohistochemically, and genetically compared with the donor patient's diagnostic specimen. Mice were treated with cisplatin and pemetrexed to assess preclinical efficacy of the chemotherapy regimen given to the donor patient.

RESULTS

The NSCLC CDX expressed lung lineage markers TTF1 and CK7 and was unresponsive to cisplatin and pemetrexed. Examination of blood samples matched to that used for CDX generation revealed absence of CTCs using the CellSearch EpCAM-dependent platform, whereas size-based CTC enrichment revealed abundant heterogeneous CTCs of which ∼80% were mesenchymal marker vimentin positive. Molecular analysis of the CDX, mesenchymal and epithelial CTCs revealed a common somatic mutation confirming tumour origin and showed CDX RNA and protein profiles consistent with the predominantly mesenchymal phenotype.

CONCLUSIONS

This study shows that the absence of NSCLC CTCs detected by CellSearch (EpCAM(+)) does not preclude CDX generation, highlighting epithelial to mesenchymal transition and the functional importance of mesenchymal CTCs in dissemination of this disease.

Hapten-induced chronic colitis in the rat: alternatives to trinitrobenzene sulfonic acid

Hapten-induced colitis is a widely used model for the study of the intestinal inflammation and for the testing of novel therapies. However, the hapten utilized in this model, trinitrobenzene sulfonic acid, is difficult to obtain in some countries. We therefore compared this hapten to two structurally related haptens to determine if they could be substituted for trinitrobenzene sulfonic acid in terms of inducing chronic colitis in the rat. Rats received one of the three haptens intracolonically, and the severity of colonic inflammation was assessed 3 and 14 days later. Dinitrobenzene sulfonic acid produced colonic inflammation and ulceration that was indistinguishable from that induced by trinitrobenzene sulfonic acid at both time points. On the other hand, dinitrochlorobenzene produced acute colitis (3 days postadministration), but by Day 14 this inflammation had subsided. Dinitrobenzene sulfonic acid and trinitrobenzene sulfonic acid produced comparable levels of granulocyte infiltration into the colon (as measured by tissue myeloperoxidase activity and histology) at both time points. These studies suggest that for studies of up to at least 2 weeks in duration, dinitrobenzene sulfonic acid and trinitrobenzene sulfonic acid produce comparable levels of colonic inflammation. Dinitrobenzene sulfonic acid therefore offers a useful and less expensive alternative to trinitrobenzene sulfonic acid.

Tissue-selective inhibition of prostaglandin synthesis in rat by tepoxalin: anti-inflammatory without gastropathy?

BACKGROUND

Inhibition of prostaglandin synthesis is likely a primary mechanism for both the anti-inflammatory and ulcerogenic effects of nonsteroidal anti-inflammatory drugs (NSAIDs). The present study examined the mechanism underlying the ability of a novel anti-inflammatory drug, tepoxalin, to suppress prostaglandin synthesis without inducing gastric mucosal injury.

METHODS

The effects on prostaglandin synthesis by various tissues of tepoxalin, diclofenac, and indomethacin were examined in vivo and in vitro. These compounds were also studied in two inflammation models. The capacity of indomethacin and tepoxalin to induced antral ulceration in the rabbit was compared.

RESULTS

In most tissues, tepoxalin was a weaker inhibitor of prostaglandin synthesis than the two NSAIDs. However, at a site of peripheral inflammation, tepoxalin was comparable with the NSAIDs in suppressing prostaglandin synthesis and in exerting anti-inflammatory effects. Indomethacin induced penetrating antral ulcers in rabbits whereas tepoxalin produced no detectable mucosal injury.

CONCLUSIONS

The ability of tepoxalin to suppress inflammation without causing gastric mucosal injury appears to be related to its differential suppression of prostaglandin synthesis in various tissues. Compounds that selectively inhibit prostaglandin synthesis at sites of inflammation may represent a class of anti-inflammatory drugs without detrimental effects on the stomach.

Effects of the long-acting insulin analog insulin glargine on cultured human skeletal muscle cells: comparisons to insulin and IGF-I

The aim of this study was to determine whether the long-acting insulin analog, insulin glargine, behaves like human insulin for metabolic and mitogenic responses in differentiated cultured human skeletal muscle cells from nondiabetic and diabetic subjects. Human insulin and insulin glargine were equipotent in their ability to compete for [(125)I]insulin binding. Insulin glargine displaced [(125)I]IGF-I from the IGF-I-binding site with approximately 0.5% the potency of IGF-I. In nondiabetic muscle cells, all three ligands stimulated glucose uptake similarly, whereas the sensitivity of glucose uptake was greatest in response to IGF-I and lower and equal for human insulin and insulin glargine. In diabetic muscle cells, the final responsiveness of glucose uptake was greatest for IGF-I and equivalent for human insulin and insulin glargine; sensitivities were the same as those for nondiabetic cells. Thymidine uptake into DNA was stimulated foremost by IGF-I, whereas human insulin and insulin glargine showed equivalent, but greatly reduced, sensitivities and potencies (<1% IGF-I). Stimulation of Akt phosphorylation was slightly more responsive to IGF-I compared with human insulin and insulin glargine, with sensitivities similar to glucose uptake stimulation. We conclude that in human skeletal muscle cells, insulin glargine is equivalent to human insulin for metabolic responses and does not display augmented mitogenic effects.

Vaccine protection against a heterologous, non-syncytium-inducing, primary human immunodeficiency virus

Vaccine-induced protection of chimpanzees against laboratory-adapted and syncytium-inducing, multiply passaged primary human immunodeficiency virus type 1 (HIV-1) isolates, but not against non-syncytium-inducing, minimally passaged ones, has been demonstrated. Following challenge with such an isolate, HIV-15016, we obtained complete protection in one of three chimpanzees previously protected against low- and high-dose HIV-1SF2 exposures after immunization with an adenovirus-HIV-1MN gp160 priming-HIV-1SF2 gp120 boosting regimen. At challenge, the protected chimpanzee exhibited broad humoral immunity, including neutralizing antibody activity. These results demonstrate the potential of this combination vaccine strategy and suggest that vaccine protection against an HIV isolate relevant to infection of people is feasible.

Chemotactic response of rat mammary adenocarcinoma cell clones to tumor-derived cytokines

A cytokine with an apparent molecular weight of 53,000 daltons was isolated from serum-free medium conditioned by MTLn3 cells or from homogenates of MTLn3 cells, a highly metastatic variant of the rat 13762NF mammary adenocarcinoma. The chemotactic responses of MTLn3 and the low metastatic variant MTLn2 cells to this cytokine were tested in vitro using modified Boyden chambers. Both the chemotactic and chemokinetic movements of MTLn3 cells were stimulated by the MTLn3-derived cytokine. In addition, the MTLn3-derived cytokine stimulated a relatively small, but significant chemotactic migration of MTLn2 tumor cells, while these cells did not respond to medium conditioned by MTLn2 cells. MTLn3 cells themselves did not respond chemotactically to type I collagen or medium conditioned by MTLn2 cells. These results suggest that the chemotactic response may be a function of metastatic potential of the invading tumor cells. The production of tumor cytokines that enhance tumor cell motility may thus represent a phenotypic difference between 13762NF tumor cell subpopulations of high and low metastatic potential.

The Impact of Positron Range on PET Resolution, Evaluated with Phantoms and PHITS Monte Carlo Simulations for Conventional and Non-conventional Radionuclides

PURPOSE

The increasing interest and availability of non-standard positron-emitting radionuclides has heightened the relevance of radionuclide choice in the development and optimization of new positron emission tomography (PET) imaging procedures, both in preclinical research and clinical practice. Differences in achievable resolution arising from positron range can largely influence application suitability of each radionuclide, especially in small-ring preclinical PET where system blurring factors due to annihilation photon acollinearity and detector geometry are less significant. Some resolution degradation can be mitigated with appropriate range corrections implemented during image reconstruction, the quality of which is contingent on an accurate characterization of positron range.

PROCEDURES

To address this need, we have characterized the positron range of several standard and non-standard PET radionuclides (As-72, F-18, Ga-68, Mn-52, Y-86, and Zr-89) through imaging of small-animal quality control phantoms on a benchmark preclinical PET scanner. Further, the Particle and Heavy Ion Transport code System (PHITS v3.02) code was utilized for Monte Carlo modeling of positron range-dependent blurring effects.

RESULTS

Positron range kernels for each radionuclide were derived from simulation of point sources in ICRP reference tissues. PET resolution and quantitative accuracy afforded by various radionuclides in practicable imaging scenarios were characterized using a convolution-based method based on positron annihilation distributions obtained from PHITS. Our imaging and simulation results demonstrate the degradation of small animal PET resolution, and quantitative accuracy correlates with increasing positron energy; however, for a specific "benchmark" preclinical PET scanner and reconstruction workflow, these differences were observed to be minimal given radionuclides with average positron energies below ~ 400 keV.

CONCLUSION

Our measurements and simulations of the influence of positron range on PET resolution compare well with previous efforts documented in the literature and provide new data for several radionuclides in increasing clinical and preclinical use. The results will support current and future improvements in methods for positron range corrections in PET imaging.

Erythrocytes: a new cell type for the evaluation of insulin receptor defects in diabetic humans

Human erythrocytes have specific insulin receptors. When studied in an insulin radioreceptor assay, erythrocytes from adult-onset, nonobese diabetic subjects bound at least 42 percent less insulin than the normal subjects at insulin concentrations from 0.1 to 100 nanograms per milliliter. The diabetic subjects had 190 insulin receptor sites per cell as compared with the 380 insulin receptor sites per cell for the normal subjects. The deficit of insulin binding in the diabetic subject was thus associated with a fewer number of insulin binding sites per cell with little or no change in affinity. The erythrocyte is a readily available cell for the evaluation of cellular insulin receptor activity.