A tunable topological insulator in the spin helical Dirac transport regime

Helical Dirac fermions-charge carriers that behave as massless relativistic particles with an intrinsic angular momentum (spin) locked to its translational momentum-are proposed to be the key to realizing fundamentally new phenomena in condensed matter physics. Prominent examples include the anomalous quantization of magneto-electric coupling, half-fermion states that are their own antiparticle, and charge fractionalization in a Bose-Einstein condensate, all of which are not possible with conventional Dirac fermions of the graphene variety. Helical Dirac fermions have so far remained elusive owing to the lack of necessary spin-sensitive measurements and because such fermions are forbidden to exist in conventional materials harbouring relativistic electrons, such as graphene or bismuth. It has recently been proposed that helical Dirac fermions may exist at the edges of certain types of topologically ordered insulators-materials with a bulk insulating gap of spin-orbit origin and surface states protected against scattering by time-reversal symmetry-and that their peculiar properties may be accessed provided the insulator is tuned into the so-called topological transport regime. However, helical Dirac fermions have not been observed in existing topological insulators. Here we report the realization and characterization of a tunable topological insulator in a bismuth-based class of material by combining spin-imaging and momentum-resolved spectroscopies, bulk charge compensation, Hall transport measurements and surface quantum control. Our results reveal a spin-momentum locked Dirac cone carrying a non-trivial Berry's phase that is nearly 100 per cent spin-polarized, which exhibits a tunable topological fermion density in the vicinity of the Kramers point and can be driven to the long-sought topological spin transport regime. The observed topological nodal state is shown to be protected even up to 300 K. Our demonstration of room-temperature topological order and non-trivial spin-texture in stoichiometric Bi(2)Se(3).M(x) (M(x) indicates surface doping or gating control) paves the way for future graphene-like studies of topological insulators, and applications of the observed spin-polarized edge channels in spintronic and computing technologies possibly at room temperature.

Observation of time-reversal-protected single-dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3

We show that the strongly spin-orbit coupled materials Bi2Te3 and Sb2Te3 and their derivatives belong to the Z2 topological-insulator class. Using a combination of first-principles theoretical calculations and photoemission spectroscopy, we directly show that Bi2Te3 is a large spin-orbit-induced indirect bulk band gap (delta approximately 150 meV) semiconductor whose surface is characterized by a single topological spin-Dirac cone. The electronic structure of self-doped Sb2Te3 exhibits similar Z2 topological properties. We demonstrate that the dynamics of spin-Dirac fermions can be controlled through systematic Mn doping, making these materials classes potentially suitable for topological device applications.

T cell antigen receptor signal transduction

The T cell antigen receptor (TCR) initiates signal transduction by activating multiple cytoplasmic protein tyrosine kinases (PTKs). Considerable progress in the field of TCR signal transduction has been made in three areas recently: first, in understanding the structure and function of the PTK ZAP-70; second, in the elucidation of the function of the substrates and pathways downstream of the PTKs; and third, in the identification of molecules that negatively regulate TCR signalling.

Tyrosine phosphorylation of Pyk2 is selectively regulated by Fyn during TCR signaling

The Src family protein tyrosine kinases (PTKs), Lck and Fyn, are coexpressed in T cells and perform crucial functions involved in the initiation of T cell antigen receptor (TCR) signal transduction. However, the mechanisms by which Lck and Fyn regulate TCR signaling are still not completely understood. One important question is whether Lck and Fyn have specific targets or only provide functional redundancy during TCR signaling. We have previously shown that Lck plays a major role in the tyrosine phosphorylation of the TCR-zeta chain and the ZAP-70 PTK. In an effort to identify the targets that are specifically regulated by Fyn, we have studied the tyrosine phosphorylation of Pyk2, a recently discovered new member of the focal adhesion kinase family PTK. We demonstrated that Pyk2 was rapidly tyrosine phosphorylated following TCR stimulation. TCR-induced tyrosine phosphorylation of Pyk2 was selectively dependent on Fyn but not Lck. Moreover, in heterologous COS-7 cells, coexpression of Pyk2 with Fyn but not Lck resulted in substantial increases in Pyk2 tyrosine phosphorylation. The selective regulation of Pyk2 tyrosine phosphorylation by Fyn in vivo correlated with the preferential phosphorylation of Pyk2 by Fyn in vitro. Our results demonstrate that Pyk2 is a specific target regulated by Fyn during TCR signaling.

Is Aeromonas hydrophila the dominant motile Aeromonas species that causes disease outbreaks in aquaculture production in the Zhejiang Province of China?

The significance of Aeromonas hydrophila in association with disease outbreaks in aquaculture production in the Zhejiang province of China was investigated. Bacteriological examination of moribund fish and crabs resulted in 95 bacterial isolates: 88 bacterial isolates from fish and 7 isolates from crabs. PCR and traditional biochemical methods were used for identification of A. hydrophila. Out of 69 motile aeromonads, 35 isolates were identified as A. hydrophila by biochemical tests. However, 6 of those were not identified as A. hydrophila by a species specific PCR method. Serotyping revealed 2 dominant serotypes (O9 and O97) among A. hydrophila isolates. The data presented show that approximately 42% of the motile aeromonads isolated from disease outbreaks among various fish species were A. hydrophila. It is noteworthy that A. hydrophila accounted for more than 50% of the isolated aeromonands isolated from crucian carp Carassius carassius and Wuchang bream Megalobrama amblycephala with haemorrhagic septicaemia. Although this species was the most frequently isolated organism from internal organs of diseased fish and crabs in the present study, other motile Aeromonas spp. were also found. The PCR assay was useful in preventing misidentification of A. hydrophila, which may occur when only phenotypic tests are employed.

Phase I study of the histone deacetylase inhibitor entinostat in combination with 13-cis retinoic acid in patients with solid tumours

BACKGROUND

Preclinical studies suggest that histone deacetylase (HDAC) inhibitors may restore tumour sensitivity to retinoids. The objective of this study was to determine the safety, tolerability, and the pharmacokinetic (PK)/pharmacodynamic (PD) profiles of the HDAC inhibitor entinostat in combination with 13-cis retinoic acid (CRA) in patients with solid tumours.

METHODS

Patients with advanced solid tumours were treated with entinostat orally once weekly and with CRA orally twice daily × 3 weeks every 4 weeks. The starting dose for entinostat was 4 mg m(-2) with a fixed dose of CRA at 1 mg kg(-1) per day. Entinostat dose was escalated by 1 mg m(-2) increments. Pharmacokinetic concentrations of entinostat and CRA were determined by LC/MS/MS. Western blot analysis of peripheral blood mononuclear cells and tumour samples were performed to evaluate target inhibition.

RESULTS

A total of 19 patients were enroled. The maximum tolerated dose (MTD) was exceeded at the entinostat 5 mg m(-2) dose level (G3 hyponatremia, neutropenia, and anaemia). Fatigue (G1 or G2) was a common side effect. Entinostat exhibited substantial variability in clearance (147%) and exposure. CRA trough concentrations were consistent with prior reports. No objective responses were observed, however, prolonged stable disease occurred in patients with prostate, pancreatic, and kidney cancer. Data further showed increased tumour histone acetylation and decreased phosphorylated ERK protein expression.

CONCLUSION

The combination of entinostat with CRA was reasonably well tolerated. The recommended phase II doses are entinostat 4 mg m(-2) once weekly and CRA 1 mg kg(-1) per day. Although no tumour responses were seen, further evaluation of this combination is warranted.

Clinical correlates of interferon gamma production in patients with tuberculosis

To determine if the capacity to produce interferon (IFN) gamma is related to the clinical manifestations of tuberculosis, we correlated Mycobacterium tuberculosis-induced IFN-gamma production by peripheral blood mononuclear cells (PBMCs) with clinical, radiographic, and laboratory variables for 63 human immunodeficiency virus (HIV)-negative patients and 43 HIV-positive patients with tuberculosis. For HIV-negative patients whose chest radiographs showed moderately advanced disease, the mean IFN-gamma concentration +/- SD was 1,639 +/- 388 pg/mL, whereas that for patients with far-advanced disease was 327 +/- 100 pg/mL (P = .0001). For HIV-infected patients who had only pleuropulmonary disease, the mean IFN-gamma concentration was 1,002 +/- 257 pg/mL, whereas that for patients with disease outside the lungs and pleura was 149 +/- 55 pg/mL (P = .0004). Multivariate analysis confirmed that the radiographic extent of disease and the site of disease were the only independent predictors of IFN-gamma production in HIV-negative and HIV-infected patients (P < or = .001). We conclude that reduced IFN-gamma production by PBMCs is a marker of severe tuberculosis in both HIV-negative and HIV-infected patients with tuberculosis.

Anergic T-lymphocyte clones have altered inositol phosphate, calcium, and tyrosine kinase signaling pathways

Full activation of TH1 helper T lymphocytes requires ligation of the specific T-cell antigen receptor (TCR) and a second signal provided by costimulator molecule(s) expressed on particular antigen-presenting cells. Stimulation via the TCR complex alone generates a subsequent unresponsive state characterized by an inability to produce interleukin 2. We report here that such anergic cells exhibit multiple alterations in TCR-associated signaling. The basal levels of intracellular free calcium and phosphatidylinositol 1,4,5-trisphosphate are elevated in anergic cells, and the levels fail to increase significantly upon subsequent restimulation. Examination of phospholipase C-gamma 1 reveals evidence for post-translational modification, correlating with increased tyrosine phosphorylation of the molecule. Tyrosine phosphorylation of additional substrates identified from whole-cell lysates also is altered compared to untreated cells, suggesting a modification in net tyrosine kinase activity. Although the level of kinase activity present in TCR/CD3 or Lck immunoprecipitates is modestly altered after induction of anergy, there is a dramatic increase in specific Fyn-associated tyrosine kinase activity in anergic cells and increased phosphorylation of a 110-kDa protein that is coimmunoprecipitated with Fyn. These results are consistent with a model in which anergic TH1 lymphocytes display a fundamental alteration in TCR-mediated tyrosine kinase activity, associated with changes in phospholipase C-gamma 1, inositol phosphates, and intracellular free calcium.

A Nck-Pak1 signaling module is required for T-cell receptor-mediated activation of NFAT, but not of JNK

The T-cell antigen receptor (TCR) triggers a signaling cascade initiated by the tyrosine kinase Lck and requiring the proto-oncogene p95(vav). Vav is activated by Lck and can function as a guanine nucleotide exchange factor for the Rho-family GTPases, Rac1 and Cdc42. To investigate the involvement of these GTPases in TCR signaling, we focused on their well characterized effector, Pak1. This serine/threonine kinase is activated by GTP-bound Rac1 or Cdc42. However, its role in mediating downstream signaling events is controversial. We observed rapid, TCR-dependent activation of Pak1 and TCR-inducible association of Pak1 with Nck, which was tyrosine phosphorylated following stimulation. Pak1 activation occurred independently of Ras activation or calcium flux, but was dependent on the Lck tyrosine kinase, and was downstream of Vav and Cdc42. Dominant negative Pak1 or Nck specifically inhibited TCR-mediated activation of the nuclear factor of activated T cells (NFAT) transcription factor. TCR-mediated activation of Erk2 was also inhibited by dominant negative Pak. However, Pak1 activation was neither necessary nor sufficient for TCR-dependent c-Jun N-terminal kinase (JNK) activation. Therefore, Pak1 acts downstream of Vav and is required for activation of Erk2 and NFAT by a JNK-independent pathway. This is the first demonstration of a requirement for Pak to mediate the regulation of gene expression by an extracellular ligand.

Effect of supplementary antioxidant vitamin intake on carotid arterial wall intima-media thickness in a controlled clinical trial of cholesterol lowering

BACKGROUND

There is accumulating experimental, epidemiological, and clinical evidence of an association between anti-oxidant vitamin intake and reduced risk of coronary heart disease. Using data from the Cholesterol Lowering Atherosclerosis Study (CLAS), we explored the association of self-selected supplementary antioxidant vitamin intake on the rate of progression of early preintrusive atherosclerosis.

METHODS AND RESULTS

CLAS was an arterial imaging trial in which nonsmoking 40- to 59-year-old men with previous coronary artery bypass graft surgery were randomized to colestipol/niacin plus diet or placebo plus diet. The rate of progression of early preintrusive atherosclerosis was determined in 146 subjects using high-resolution B-mode ultrasound quantification of the distal common carotid artery far wall intima-media thickness (IMT). From the nutritional supplement database, 22 subjects had an on-trial average supplementary vitamin E intake of > or = 100 IU per day (high users) and 29 subjects had an average on-trial supplementary vitamin C intake of > or = 250 mg per day (high users). Within the placebo group, less carotid IMT progression was found for high supplementary vitamin E users when compared with low vitamin E users (0.008 versus 0.023 mm/y, P = .03). No effect of vitamin E within the drug group was found. No effect of vitamin C within the drug or placebo group was found.

CONCLUSIONS

Supplementary vitamin E intake appears to be effective in reducing the progression of atherosclerosis in subjects not treated with lipid-lowering drugs while the process is still confined to the arterial wall (early preintrusive atherosclerosis).

In-situ transmission electron microscopy studies of polymer-carbon nanotube composite deformation

This paper demonstrates the viability of in-situ transmission electron microscopy for studying the deformation mechanisms of polymer nano-composites. In-situ straining studies are performed on carbon multiwalled nanotube (MWNT)-polystyrene composite films. The experiments show that load transfer across the nanotube-polystyrene interface is operative well into the plastic deformation regime of the composite film. The MWNTs are observed to bridge cracks propagating through the polystyrene, providing closure stresses across the crack wake. Although some MWNTs fracture by either a sword-in-sheath mechanism or transverse shear fracture, most of the MWNTs eventually debond at the MWNT-polymer interface and subsequently pull out of the matrix.

Elevated blood pressure in subjects with lipodystrophy

OBJECTIVES

To assess the prevalence of elevated blood pressure in patients with lipodystrophy.

DESIGN

Case-control study.

PARTICIPANTS

Forty-two patients with abnormal body fat (100%) and serum lipids (86%) (HIV-positive cohort) were matched by age and sex to 42 HIV-positive controls without previously diagnosed lipodystrophy and to 13 HIV-negative controls.

SETTING

Tertiary care, university-based, fully dedicated HIV clinic.

MAIN OUTCOME MEASURES

Frequency and magnitude of elevated blood pressure during highly active antiretroviral therapy.

RESULTS

There were 23 +/- 16 and 22 +/- 12 blood pressure measurements recorded per subject over 21 +/- 11 and 22 +/- 11 months for the HIV-positive cohort and HIV-positive controls, respectively. Three or more elevated readings occurred in 74% of the cohort and in 48% of the HIV-positive controls (P = 0.01) and accounted for 38 +/- 25% versus 22 +/- 26% (P = 0.01) of the total readings, respectively. The average of the three highest systolic readings (153 +/- 17 versus 144 +/- 15 mmHg; P = 0.01) and diastolic readings (92 +/- 10 versus 87 +/- 9 mmHg; P = 0.01) was greater for the cohort than for the HIV-positive controls. Family history of hypertension was more common in the cohort than in the controls but accounted for only 13% of the log odds ratio value for elevated blood pressure in the cohort. Systolic blood pressure was correlated with waist-to-hip ratios in the cohort (r = 0.45; P = 0.003) but not in the HIV controls (r = 0.06; P = 0.68) and tended to be related to fasting triglycerides (r = 0.34; P = 0.052) in subjects with HIV.

CONCLUSIONS

Elevated blood pressure may be linked to the metabolic disorders occurring in patients with HIV, as in the dysmetabolic syndrome.

Dominant-negative zeta-associated protein 70 inhibits T cell antigen receptor signaling

Zeta-associated protein (ZAP)-70 is a cytoplasmic protein tyrosine required for T cell antigen receptor (TCR) signaling and development. Mutations in ZAP-70 result in severe combined immunodeficiency in humans. ZAP-70 interacts with the TCR by binding to tyrosine-phosphorylated immunoreceptor tyrosine-based activation motifs (ITAMs) present in the invariant subunits of the TCR complex. Here we report that two ZAP-70 mutants devoid of kinase activity, generated either by a point mutation in the kinase domain to create an inactive kinase, or by truncation of the entire kinase domain (SH2[N+C]), functioned as dominant-negative mutants to specifically suppress TCR-mediated activation of NFAT, a nuclear factor essential for inducible interleukin 2 gene expression. Biochemical studies with the SH2(N+C) mutant showed that it also blocked early TCR signaling events, such as p95vav tyrosine phosphorylation, extracellular signal-regulated kinase 2 activation, and the association of a number of tyrosine-phosphorylated proteins with growth factor receptor-binding protein 2 (GRB2). The inhibitory effects of the SH2(N+C) mutant revealed that it requires an intact phosphotyrosine-binding site in its COOH-terminal SH2 domain. Using a CD8-zeta chimeric receptor to analyze the interaction of the SH2(N+C) mutant with ITAMs of TCR-zeta, we found that this mutant was constitutively bound to the hyperphosphorylated CD8-zeta chimera. These results indicate that tyrosine-phosphorylated ITAM is the target for the action of this dominant-negative mutant, suggesting that the assembly of a functional receptor signaling complex on ITAMs is a critical proximal TCR signaling event leading to downstream activation.

A pilot randomized, controlled trial of the effect of iron depletion on long-term response to alpha-interferon in patients with chronic hepatitis C

BACKGROUND/AIMS

Some studies have suggested that hepatic iron may influence the response to interferon therapy in chronic hepatitis C patients. We conducted this randomized, controlled trial to evaluate the effect of iron depletion on: (1) aminotransferase activity and hepatitis C RNA levels; and (2) response to interferon therapy in 38 patients with elevated alanine aminotransferase levels and who were HCV RNA positive.

METHODS

Seventeen patients underwent a 500-ml phlebotomy every 2 weeks until iron deficiency was achieved. Patients were then started on a 6-month course of alpha-interferon 2b (3 mu tiw). Controls were 21 patients who were monitored for a 6- to 8-week period without phlebotomy prior to interferon therapy. Response to interferon was defined as loss of serum HCV RNA by reverse transcriptase-polymerase chain reaction. Serum HCV RNA was quantitated by bDNA technique.

RESULTS

Alanine aminotransferase levels decreased in 15/17 patients after phlebotomy. Mean alanine aminotransferase fell from 156.8 to 89.7 U/l (p=0.008). Changes in iron indices and alanine aminotransferase after phlebotomy were not accompanied by changes in HCV RNA levels. In control patients, neither alanine aminotransferase nor HCV RNA levels changed during the observation period. At the end of 24 weeks of interferon therapy, 7/17 phlebotomized patients had a response, compared to 6/21 control patients (p=ns). After 6 months of follow-up, 5/17 phlebotomized patients remained HCV RNA negative, in contrast to only 1/21 controls (p=0.07).

CONCLUSIONS

Iron depletion led to a reduction in aminotransferase levels; this was not accompanied by changes in levels of hepatitis C RNA. There may be an improvement in the sustained response to interferon therapy, but this requires confirmation.

Influence of quantity of lymph-vascular space invasion on the risk of nodal metastases in women with early-stage squamous cancer of the cervix

OBJECTIVE

To determine if the quantity of lymph-vascular space invasion influences the risk of pelvic nodal metastases in women with early-stage cervical squamous carcinoma.

METHODS

Between 1991 and 1997, 105 women with stages IA2, Ib, and IIa squamous carcinoma of the cervix underwent radical hysterectomy and pelvic lymphadenectomy. The histopathology slides were prospectively reviewed. If lymph-vascular space invasion (LVSI) was present, the amount was quantified in four ways: percentage of cervical histopathologic sections containing LVSI, percentage of sections with tumor containing LVSI, total number of foci of LVSI, and maximal number of foci of LVSI in 10 high-powered fields. These measures of LVSI were correlated with the risk of nodal metastases.

RESULTS

Seventy-three (70%) women had tumors with LVSI. Of these, 23 had pelvic nodal metastases. All women with nodal metastases had tumors with LVSI. Using logistic regession, independent predictors of nodal metastases were depth of cervical stromal invasion (P = 0.01) and tumor size (P = 0.04). LVSI was also a significant predictor of nodal metastases based on the Mantel-Haenszel test (P = 0.01). In women whose tumors contained LVSI, logistic regression identified tumor size (P = 0.004) and LVSI in > 45% of all cervical histopathologic sections (P = 0.002) as significant predictors of nodal metastases.

CONCLUSION

The quantity of LVSI, as defined by the percentage of all cervical histopathologic sections containing LVSI, correlates significantly with the risk of nodal metastases in women with early-stage squamous carcinoma of the cervix.

Associations of food-cobalamin malabsorption with ethnic origin, age, Helicobacter pylori infection, and serum markers of gastritis

OBJECTIVES

Food-cobalamin malabsorption is common in patients with low cobalamin levels. However, characterization of affected subjects has been limited. The aim of this study was to analyze demographic and gastric data in a large study population.

METHODS

Data were collected prospectively in 202 subjects (43 volunteers and 159 patients) who underwent the egg yolk-cobalamin absorption test (EYCAT). H. pylori status was determined in 167 of the subjects, serum gastrin and antiparietal cell antibody in 158 and pepsinogen (PG) I and PG II levels in 133.

RESULTS

Latin American and black patients had lower EYCAT results than did white or Asian-American ones (p = 0.0001) and had severe food-cobalamin malabsorption (EYCAT < 1%) more often (p = 0.0001). Age correlated inversely with EYCAT results (p = 0.02). H. pylori infection was associated with food-cobalamin malabsorption (p = 0.0001), especially with severe malabsorption where 29/37 subjects (78.4%) were infected. Malabsorption was also associated with higher gastrin levels (p = 0.0001) and lower PG I levels (p = 0.01) and PG I:PG II ratios (p = 0.0001). Multivariate analysis showed that ethnic origin, gastrin levels, H. pylori infection and, to a lesser extent, age were independently associated with the EYCAT results.

CONCLUSIONS

Latin American and black patients have food-cobalamin malabsorption more often than do white and Asian-American patients. This association is independent of the malabsorption's association with H. pylori infection, markers of gastritis, such as gastrin, and older age. The patterns of gastric tests suggest that malabsorption may be due to diverse mechanisms, not just atrophic gastritis. The possible role of H. pylori infection in many cases of severe food-cobalamin malabsorption also suggests avenues of treatment and prevention.

Extra small virus-like particles (XSV) and nodavirus associated with whitish muscle disease in the giant freshwater prawn, Macrobrachium rosenbergii

A disease of Macrobrachium rosenbergii, the giant freshwater prawn, farmed in China was recently recorded in Zhejiang, Jiangsu, Shanghai, Guangxi and Guangdong provinces. The clinical sign of the disease, which develops in post-larvae (PL), is a whitish appearance of the muscles, particularly noticeable in the abdomen. Mortalities may reach 100% in some hatcheries. Investigations by transmission electron microscopy after negative staining of diseased PL homogenates showed the presence of two types of viral particles: one, unenveloped, icosahedral in shape, 26-27 nm in diameter, the second, much smaller, about 14-16 nm in diameter, designated extra small virus particle (XSV). The large virus has a genome with two pieces of ssRNA (RNA-1 and RNA-2), of 3 and 1.2 kb, respectively. Hybridization tests confirmed that this large virus is closely related to M. rosenbergii nodavirus (MrNV) which was isolated from diseased prawns in a hatchery in the French West Indies. Its very small size and hypothesized biochemical and biological characteristics suggest XSV is a new type of crustacean virus. As XSV has always been found associated with the larger virus (nodavirus) and is located in muscle and connective cells of diseased animals, it could be an autonomous virus, a helper-type virus or a satellite-like virus.

CD4 cell counts in human immunodeficiency virus-negative patients with tuberculosis

We evaluated 85 human immunodeficiency virus (HIV)-negative patients with tuberculosis for clinical features and CD4 cell counts. Thirty-seven patients had low CD4 cell counts (mean +/- SD, 341 +/- 116 cells/microL), and 48 patients had normal CD4 cell counts (mean +/- SD, 830 +/- 254 cells/microL). CD4 cell counts were most strongly correlated with total lymphocyte counts (r = 0.84). If total lymphocyte count was excluded, depressed CD4 cell counts were significantly associated with low serum albumin levels, extensive pulmonary disease, low body-mass index, and low hematocrit. Of these four variables, multivariate linear discriminant analysis revealed that the serum albumin level was the best single predictor of low CD4 cell counts and that the other three variables did not improve predictive value. Because these four variables are markers of severe tuberculosis, these findings suggest that disease severity is associated with greater depression of the total lymphocyte and CD4 cell counts. The CD4 cell counts returned to normal levels in most patients after 1 month of therapy.

The gamma chain of the high-affinity receptor for IgE is a major functional subunit of the T-cell antigen receptor complex in gamma delta T lymphocytes

T-cell activation is a consequence of the clonotypic T-cell antigen receptor (TCR) binding to an antigen followed by signal transduction via the invariant subunits of the TCR/CD3 complex. gamma delta TCR cells are a small subset of T cells that populate both the epithelial and lymphoid tissues and have unique antigen specificity and function. However, the composition of invariant chains within the gamma delta TCR/CD3 complex has not been well characterized. Here we report that, unlike the majority of alpha beta T cell, gamma delta T cells isolated from spleen and intestinal epithelial tissue express high levels of the gamma chain of the high-affinity receptor for IgE (Fc epsilon RI gamma) as one invariant subunit of their TCR/CD3 complex. Fc epsilon RI gamma exists as both a homodimer and a heterodimer associated with the TCR zeta chain. Moreover, stimulation of the gamma delta TCR results in rapid tyrosine phosphorylation of Fc epsilon RI gamma. Our results suggest that utilization of distinct receptor signaling components may enable the coupling of antigen stimulation to the activation of different signal transduction pathways in alpha beta and gamma delta T cells.

Prospective evaluation of the effect of initiating indinavir-based therapy on insulin sensitivity and B-cell function in HIV-infected patients

OBJECTIVE

To determine whether initiation of antiretroviral therapy that includes the protease inhibitor indinavir causes insulin resistance or abnormal B-cell function in study subjects with HIV infection.

METHODS

Nonwasted, HIV-infected study subjects who did not have concurrent diabetes were prospectively evaluated by oral and intravenous glucose tolerance testing at baseline, at 2 weeks after starting indinavir monotherapy, and at another 6 weeks after initiating indinavir-based triple-therapy.

RESULTS

Mean CD4 count at entry was 282 cells/microl and median HIV RNA was 33,000 copies/ml; all experienced a virologic response. Fasting glucose increased from 83.2 +/- 3.7 mg/dl at baseline to 86.8 +/- 3.2 at week 2 and 91.7 +/- 3.5 at week 8 (p =.003). Insulin sensitivity by minimal model analysis decreased by 30.5% over 8 weeks, from 3.83 +/- 0.63 min-1 per microU/ml x 10-4 to 3.09 +/- 0.53 at week 2 and 2.66 +/- 0.35 at week 8 (p =.01). Insulin secretion by the acute insulin response to intravenous glucose did not change (baseline 822 +/- 283 microU/ml x min, week 8 880 +/- 289; p = 0.4), and the insulin response to oral glucose (30 minute insulin:glucose ratio) fell from 1.69 +/- 0.54 microU/ml per mg/dl at baseline to 1.18 +/- 0.34 at week 8 (p =.05).

CONCLUSION

During 8 weeks of indinavir-based therapy, fasting glucose increased and insulin sensitivity decreased, without a compensatory increase in insulin release. This combination of insulin resistance without augmented B-cell response may explain the hyperglycemia and other metabolic abnormalities seen in some protease inhibitor-treated patients.

Risk of residual invasive disease in women with microinvasive squamous cancer in a conization specimen

OBJECTIVE

To quantify the risk of residual invasion when cervical conization reveals microinvasive squamous carcinoma and to determine whether any factors affect this risk.

METHODS

We reviewed the charts and histopathology slides of 87 women who underwent a conization that contained microinvasive squamous carcinoma, followed by either a repeat conization or hysterectomy. Depth of invasion, number of invasive foci, and status of the internal margin and post-conization endocervical curettage (ECC) were assessed. The findings were correlated with the presence of residual invasion.

RESULTS

Significant predictors of residual invasion included status of the internal margin (residual invasion present in 22% of women with an involved margin versus 3% with a negative margin; P < .03) and the combined status of the internal margin and post-conization ECC (residual invasion in 4% of patients if both negative, 13% if one positive, and 33% if both positive; P < .015). Depth of invasion and number of invasive foci in the conization specimen were not significant. The power of this study to detect a 25% difference in the risk of residual invasion was 73% for depth of invasion and 75% for number of invasive foci.

CONCLUSION

Women with microinvasive squamous carcinoma in a conization specimen in which both the internal conization margin and post-conization ECC are negative have a low risk of residual invasion and are candidates for follow-up or simple hysterectomy. If either the internal margin or the post-conization ECC contains dysplasia or carcinoma, the risk of residual invasion is high and warrants repeat conization before definitive treatment planning.