Rapid and non-destructive identification of Anopheles gambiae and Anopheles arabiensis mosquito species using Raman spectroscopy via machine learning classification models.

BACKGROUND: Identification of malaria vectors is an important exercise that can result in the deployment of targeted control measures and monitoring the susceptibility of the vectors to control strategies. Although known to possess distinct biting behaviours and habitats, the African malaria vectors Anopheles gambiae and Anopheles arabiensis are morphologically indistinguishable and are known to be discriminated by molecular techniques. In this paper, Raman spectroscopy is proposed to complement the tedious and time-consuming Polymerase Chain Reaction (PCR) method for the rapid screening of mosquito identity. METHODS: A dispersive Raman microscope was used to record spectra from the legs (femurs and tibiae) of fresh anaesthetized laboratory-bred mosquitoes. The scattered Raman intensity signal peaks observed were predominantly centered at approximately 1400 cm-1, 1590 cm-1, and 2067 cm-1. These peaks, which are characteristic signatures of melanin pigment found in the insect cuticle, were important in the discrimination of the two mosquito species. Principal Component Analysis (PCA) was used for dimension reduction. Four classification models were built using the following techniques: Linear Discriminant Analysis (LDA), Logistic Regression (LR), Quadratic Discriminant Analysis (QDA), and Quadratic Support Vector Machine (QSVM). RESULTS: PCA extracted twenty-one features accounting for 95% of the variation in the data. Using the twenty-one principal components, LDA, LR, QDA, and QSVM discriminated and classified the two cryptic species with 86%, 85%, 89%, and 93% accuracy, respectively on cross-validation and 79%, 82%, 81% and 93% respectively on the test data set. CONCLUSION: Raman spectroscopy in combination with machine learning tools is an effective, rapid and non-destructive method for discriminating and classifying two cryptic mosquito species, Anopheles gambiae and Anopheles arabiensis belonging to the Anopheles gambiae complex.

Fasting plasma glucose and risk factor assessment: Comparing sensitivity and specificity in identifying gestational diabetes in urban black African women.

BACKGROUND: Identifying women with gestational diabetes mellitus (GDM) allows interventions to improve perinatal outcomes. A fasting plasma glucose (FPG) level ≥5.1 mmol/L is 100% specific for a diagnosis of GDM. The International Association of Diabetes and Pregnancy Study Groups acknowledges that FPG <4.5 mmol/L is associated with a low probability of GDM. OBJECTIVES: The validity of selective screening based on the presence of risk factors was compared with the universal application of FPG ≥4.5 mmol/L to identify women with GDM. FPG ≥4.5 mmol/L or the presence of one or more risk factors was assumed to indicate an intermediate to high risk of GDM and therefore the need for an oral glucose tolerance test (OGTT). METHODS: Consecutive black South African (SA) women were recruited to a 2-hour 75 g OGTT at 24 - 28 weeks' gestation in an urban community health clinic. Of 969 women recruited, 666 underwent an OGTT, and of these 589 were eligible for analysis. The glucose oxidase laboratory method was used to measure plasma glucose concentrations. The World Health Organization GDM diagnostic criteria were applied. All participants underwent a risk factor assessment. The χ2 test was used to determine associations between risk factors and a positive diagnosis of GDM. The sensitivity and specificity of a positive diagnosis of GDM were calculated for FPG ≥4.5 mmol/L, FPG ≥5.1 mmol/L, and the presence of one or more risk factors. RESULTS: The prevalence of overt diabetes mellitus and GDM was 0.5% and 7.0%, respectively. Risk factor-based selective screening indicated that 204/589 (34.6%) of participants needed an OGTT, but 18/41 (43.9%) of positive GDM diagnoses were missed. Universal screening using the FPG threshold of ≥4.5 mmol/L indicated that 152/589 (25.8%) of participants needed an OGTT, and 1/41 (2.4%) of positive diagnoses were missed. An FPG of ≥5.1 mmol/L identified 36/41 (87.8%) of GDM-positive participants. The sensitivity and specificity of the presence of one or more risk factors were 56% and 67%, respectively. The sensitivity and specificity of FPG ≥4.5 mmol/L were 98% and 80%, respectively. CONCLUSIONS: Universal screening using FPG ≥4.5 mmol/L had greater sensitivity and specificity in identifying GDM-affected women and required fewer women to undergo a resource-intensive diagnostic OGTT than risk factor-based selective screening. A universal screening strategy using FPG ≥4.5 mmol/L may be more efficient and cost-effective than risk factor-based selective screening for GDM in black SA women.

The occurrence of cardiac abnormalities in canine steroid-responsive meningitis arteritis.

OBJECTIVES: To document the prevalence of cardiac abnormalities in dogs with steroid-responsive meningitis arteritis and to assess resolution of these abnormalities following corticosteroid therapy. MATERIALS AND METHODS: Steroid-responsive meningitis arteritis was diagnosed based on signalment, physical examination findings, complete blood count, biochemistry and CSF analysis. Echocardiography, C-reactive protein and cardiac troponin I were measured in all cases before and 10 to 14 days after commencing corticosteroid therapy. Fibrinogen was also measured in a proportion of dogs. RESULTS: Fourteen dogs were prospectively enrolled. Increased cardiac troponin I was identified in five of 14 dogs and echocardiographic abnormalities were detected in 12 of 14 dogs, including spontaneous echo contrast (12 of 14), mild pericardial effusion (five of 14) and mildly decreased fractional shortening (five of 14). All dogs had increased C-reactive protein and fibrinogen was increased in 11 of 12. Corticosteroid treatment was associated with clinical improvement and normalisation of C-reactive protein in all dogs. The cardiac troponin I levels normalised in four of five and fibrinogen had normalised in all five dogs which were retested. Spontaneous echo contrast improved or completely resolved in 12 of 12 and pericardial effusion resolved in five of five dogs. Fractional shortening normalised in two of five dogs. CLINICAL SIGNIFICANCE: Cardiac changes are common in dogs with steroid-responsive meningitis arteritis and most resolve with therapy. Further investigation into the cause and significance of these changes is necessary in determining whether antithrombotic therapy or positive inotropic therapy is indicated.

Application of principal component analysis to multispectral-multimodal optical image analysis for malaria diagnostics.

BACKGROUND: Multispectral imaging microscopy is a novel microscopic technique that integrates spectroscopy with optical imaging to record both spectral and spatial information of a specimen. This enables acquisition of a large and more informative dataset than is achievable in conventional optical microscopy. However, such data are characterized by high signal correlation and are difficult to interpret using univariate data analysis techniques. METHODS: In this work, the development and application of a novel method which uses principal component analysis (PCA) in the processing of spectral images obtained from a simple multispectral-multimodal imaging microscope to detect Plasmodium parasites in unstained thin blood smear for malaria diagnostics is reported. The optical microscope used in this work has been modified by replacing the broadband light source (tungsten halogen lamp) with a set of light emitting diodes (LEDs) emitting thirteen different wavelengths of monochromatic light in the UV-vis-NIR range. The LEDs are activated sequentially to illuminate same spot of the unstained thin blood smears on glass slides, and grey level images are recorded at each wavelength. PCA was used to perform data dimensionality reduction and to enhance score images for visualization as well as for feature extraction through clusters in score space. RESULTS: Using this approach, haemozoin was uniquely distinguished from haemoglobin in unstained thin blood smears on glass slides and the 590-700 spectral range identified as an important band for optical imaging of haemozoin as a biomarker for malaria diagnosis. CONCLUSION: This work is of great significance in reducing the time spent on staining malaria specimens and thus drastically reducing diagnosis time duration. The approach has the potential of replacing a trained human eye with a trained computerized vision system for malaria parasite blood screening.

Local breast cancer recurrence after mastectomy and immediate breast reconstruction for invasive cancer: a meta-analysis.

BACKGROUND: The main priorities in the surgical treatment of patients with breast cancer are to achieve cure, local control and prevent recurrence. It is increasingly important to address quality of life and self-image with women undergoing surgical intervention for breast cancer. There is a lack of consensus as to the oncologic safety of immediate breast reconstruction (IBR). The purpose of this paper is to systematically review the literature and compare the frequency of recurrence in patients with and without IBR following mastectomy for breast cancer. METHODS: Two independent investigators searched PubMed, Embase, and the Cochrane database using predefined search terms. After application of inclusion and exclusion criteria, 10 articles remained. Each article was assessed for quality. Relevant data was collected including recurrence rates, cancer stage, type of mastectomy and reconstruction, adjuvant treatments, and duration of follow-up. RESULTS: Inter-rater reliability was good at 74% (95% CI: 0, 93%). There was no evidence of study heterogeneity (p for Q-statistic=0.34 and I(2)=12%). The OR ratio for recurrence of breast cancer for mastectomy with IBR as compared to mastectomy alone was 0.98 (95% CI: 0.62, 1.54). CONCLUSION: This meta-analysis demonstrated no evidence for increased frequency of local breast cancer recurrence with IBR compared with mastectomy alone.

Acute psychiatric disorders in foreign domestic workers in Hong Kong: a pilot study.

AIM: To explore the psychopathology of foreign domestic workers (FDWs) who had an acute psychiatric disorder in Hong Kong. METHOD: This was a retrospective chart review. Demographic and clinical data were extracted from case records of FDWs who were admitted for the first time as inpatients for psychiatric treatment to three regional hospitals of the same catchment area in Hong Kong between 2000 and 2004. Relevant socio-demographic data on local FDWs and the general population of Hong Kong were obtained from local government departments. RESULTS: Twenty-seven Filipino and 14 Indonesian FDWs presenting with their first and so far only psychiatric admission were identified. There were significantly more FDWs who were single or never married in the sample. Filipino FDWs tended to fall ill after 4 years of service in Hong Kong while the corresponding figure for Indonesian FDWs was 2 years. Indonesian FDWs were older and had less access to social and medical services than their Filipino counterparts. Home sickness and marital problems were more commonly identified as stressors rather than work-related difficulties. Acute and Transient Psychotic Disorder (ICD-10) was diagnosed in over 60% of the subjects, making FDWs two times more vulnerable than local women of similar age for this illness. CONCLUSIONS: FDWs constitute a vulnerable group in terms of psychiatric morbidity. Concerted political, social and psychological efforts would be require to alleviate the distress faced by this particularly disadvantaged subset of female expatriates.

Fatty acid and phorbol ester-mediated interference of mitogenic signaling via novel protein kinase C isoforms in pancreatic beta-cells (INS-1).

It is possible that activation of protein kinase C (PKC) isoforms by free fatty acids (FFA) plays a role in the failure of pancreatic beta-cell mass expansion to compensate for peripheral insulin resistance in the pathogenesis of type-2 diabetes. The effect of lipid moieties on activation of conventional (PKC-alpha and -beta1), novel (PKC-delta) and atypical (PKC-zeta) PKC isoforms was evaluated in an in vitro assay, using biotinylated neurogranin as a substrate. Oleoyl-Coenzyme A (CoA) and palmitoyl-CoA, but not unesterified FFA, significantly increased the activity of all PKC isoforms (P< or =0.05), particularly that for PKC-delta. It was found that FFA (0.4 mM oleate/complexed to 0.5% bovine serum albumin) inhibited IGF-I-induced activation of protein kinase B (PKB) in the pancreatic beta-cell line (INS-1), but this was alleviated in the presence of the general PKC inhibitor (Gö6850; 1 microM). To further investigate whether conventional or novel PKC isoforms adversely affect beta-cell proliferation, the effect of phorbol ester (phorbol 12-myristate 13-acetate; PMA)-mediated activation of these PKC isoforms on glucose/IGF-I-induced INS-1 cell mitogenesis, and insulin receptor substrate (IRS)-mediated signal transduction was investigated. PMA-mediated activation of PKC (100 nM; 4 h) reduced glucose/IGF-I mediated beta-cell mitogenesis (>50%; P< or =0.05), which was reversible by the general PKC inhibitor Gö6850 (1 microM), indicating an effect of PKC and not due to a non-specific PMA toxicity. PMA inhibited IGF-I-induced activation of PKB, correlating with inhibition of IGF-I-induced association of IRS-2 with the p85 regulatory subunit of phosphatidylinositol-3 kinase. However, in contrast, PMA activated the mitogen-activated protein kinases, Erk1/2. Titration inhibition analysis using PKC isoform inhibitors indicated that these PMA-induced effects were via novel PKC isoforms. Thus, FFA/PMA-induced activation of novel PKC isoforms can inhibit glucose/IGF-I-mediated beta-cell mitogenesis, in part by decreasing PKB activation, despite an upregulation of Erk1/2. Thus, activation of novel PKC isoforms by long-chain acyl-CoA may well contribute to decreasing beta-cell mass in the pathogenesis of type-2 diabetes, similar to their inhibition of insulin signal transduction which causes insulin resistance.

Retrotransposition of a yeast group II intron occurs by reverse splicing directly into ectopic DNA sites.

Group II introns, the presumed ancestors of nuclear pre-mRNA introns, are site-specific retroelements. In addition to "homing" to unoccupied sites in intronless alleles, group II introns transpose at low frequency to ectopic sites that resemble the normal homing site. Two general mechanisms have been proposed for group II intron transposition, one involving reverse splicing of the intron RNA directly into an ectopic DNA site, and the other involving reverse splicing into a site in RNA followed by reverse transcription and integration of the resulting cDNA by homologous recombination. Here, by using an "inverted-site" strategy, we show that the yeast mtDNA group II intron aI1 retrotransposes by reverse splicing directly into an ectopic DNA site. This same mechanism could account for other previously described ectopic transposition events in fungi and bacteria and may have contributed to the dispersal of group II introns into different genes.

Early detection of maedi-visna (ovine progressive pneumonia) virus seroconversion in field sheep samples.

The aim of this work was to investigate whether an enzyme-linked immunosorbent assay (ELISA) was useful for early detection of maedi-visna virus (MVV) infection in sheep under field conditions. An ELISA based on p25 recombinant protein and a gp46 synthetic peptide was used. Sequentially obtained serum samples (n = 1,941) were studied for 4 years. ELISA results were compared with those of the agar gel immunodiffusion (AGID) test, and results of both tests were compared with a reference result established using consensus scores for at least 2 of 3 serologic techniques (AGID, ELISA, and western blotting, which was used to resolve result discrepancies between the other 2 techniques). A total of 247 discrepancies were observed between ELISA and AGID. Of these, 131 were due to an earlier detection of 120 sera by the ELISA and 11 sera by AGID. The remaining discrepancies (116) were due to the presence of false reactions in both tests. Fewer false-negative results were found by ELISA than with AGID (6 vs. 69 sera, respectively), whereas the number of false-positive results was virtually the same for ELISA and AGID (21 vs. 20, respectively). In relation to the reference result, ELISA sensitivity and specificity were 97.8% and 98.2%, respectively, whereas values for AGID were 76.3% and 98.3%, respectively. The agreement between ELISA and the reference result was higher than that between AGID and the reference result (K value: 0.96 and 0.77, respectively). A variation in the ELISA signal (based on optical density) was observed during the study period, suggesting different antibody levels throughout the animal's life. The ELISA was useful for detecting MVV-infected sheep in field conditions and has potential for use in control and eradication programs.

Differential activation of protein kinase B and p70(S6)K by glucose and insulin-like growth factor 1 in pancreatic beta-cells (INS-1).

It has been shown that IGF-1-induced pancreatic beta-cell proliferation is glucose-dependent; however, the mechanisms responsible for this glucose dependence are not known. Adenoviral mediated expression of constitutively active phosphatidylinositol 3-kinase (PI3K) in the pancreatic beta-cells, INS-1, suggested that PI3K was not necessary for glucose-induced beta-cell proliferation but was required for IGF-1-induced mitogenesis. Examination of the signaling components downstream of PI3K, 3-phosphoinositide-dependent kinase 1, protein kinase B (PKB), glycogen synthase kinase-3, and p70-kDa-S6-kinase (p70(S6K)), suggested that a major part of glucose-dependent beta-cell proliferation requires activation of mammalian target of rapamycin/p70(S6K), independent of phosphoinositide-dependent kinase 1/PKB activation. Adenoviral expression of the kinase-dead form of PKB in INS-1 cells decreased IGF-1-induced beta-cell proliferation. However, a surprisingly similar decrease was also observed in adenoviral wild type and constitutively active PKB-infected cells. Upon analysis of extracellular signal-regulated protein kinase 1 and 2 (ERK1/ERK2), an increase in ERK1/ERK2 phosphorylation activation by glucose and IGF-1 was observed in kinase-dead PKB-infected cells, but this phosphorylation activation was inhibited in the constitutively active PKB-infected cells. Hence, there is a requirement for the activation of both ERK1/ERK2 and mammalian target of rapamycin/p70(S6K) signal transduction pathways for a full commitment to glucose-induced pancreatic beta-cell mitogenesis. However, for IGF-1-induced activation, these pathways must be carefully balanced, because chronic activation of one (PI3K/PKB) can lead to dampening of the other (ERK1/2), reducing the mitogenic response.

Multiple homing pathways used by yeast mitochondrial group II introns.

The yeast mitochondrial DNA group II introns aI1 and aI2 are retroelements that insert site specifically into intronless alleles by a process called homing. Here, we used patterns of flanking marker coconversion in crosses with wild-type and mutant aI2 introns to distinguish three coexisting homing pathways: two that were reverse transcriptase (RT) dependent (retrohoming) and one that was RT independent. All three pathways are initiated by cleavage of the recipient DNA target site by the intron-encoded endonuclease, with the sense strand cleaved by partial or complete reverse splicing, and the antisense strand cleaved by the intron-encoded protein. The major retrohoming pathway in standard crosses leads to insertion of the intron with unidirectional coconversion of upstream exon sequences. This pattern of coconversion suggests that the major retrohoming pathway is initiated by target DNA-primed reverse transcription of the reverse-spliced intron RNA and completed by double-strand break repair (DSBR) recombination with the donor allele. The RT-independent pathway leads to insertion of the intron with bidirectional coconversion and presumably occurs by a conventional DSBR recombination mechanism initiated by cleavage of the recipient DNA target site by the intron-encoded endonuclease, as for group I intron homing. Finally, some mutant DNA target sites shift up to 43% of retrohoming to another pathway not previously detected for aI2 in which there is no coconversion of flanking exon sequences. This new pathway presumably involves synthesis of a full-length cDNA copy of the inserted intron RNA, with completion by a repair process independent of homologous recombination, as found for the Lactococcus lactis Ll.LtrB intron. Our results show that group II intron mobility can occur by multiple pathways, the ratios of which depend on the characteristics of both the intron and the DNA target site. This remarkable flexibility enables group II introns to use different recombination and repair enzymes in different host cells.

Gas chromatographic-mass spectrometric determination of sulfolane in wetland vegetation exposed to sour gas-contaminated groundwater.

Described is a GC-MS method for the determination of the levels of sulfolane (tetrahydrothiophene 1,1-dioxide, C4H8O2S; a water miscible chemical used in the sweetening of sour gas) in wetland vegetation (roots, shoots, berries, seeds, grasses, and leaves). The technique was developed to provide positive detection of sulfolane in a variety of wetland vegetation and to determine the extent to which sulfolane may translocate within the plants. Vegetation samples collected at a sour gas processing facility were extracted using a two-stage process which utilized a back extraction of a water extract with toluene. The main advantages of this procedure were: good extraction efficiency (recovery of 80+/-12%), exclusion of most of the highly polar co-extractives during the toluene back extraction step, and a final extract well suited to routine GC-MS selected ion monitoring of sulfolane with a detection limit of 90 ng g(-1) (wet mass). In general, the method was rugged, based on a study period of 18 months in which over 175 runs were conducted.

mRNA translation in yeast during entry into stationary phase.

The expression of some Saccharomyces cerevisiae genes is induced as cells enter stationary phase. Their mRNAs are translated during a period in the growth cycle when the translational apparatus is relatively inert, thereby raising the possibility that these mRNAs compete effectively for a limiting pool of translation factors. To test this idea, the translation of mRNAs carrying different 5'-leaders was compared during exponential growth and after entry into stationary phase upon glucose starvation. Closely related sets of lacZ mRNAs, carrying 5'-leaders from the PYK1, PGK1, RpL3, Rp29, HSP12, HSP26 or THI4 mRNAs, were studied. These mRNAs displayed differing translational efficiencies during exponential growth, but their relative translatabilities were not significantly affected by entry into stationary phase, indicating that they compete just as effectively under these conditions. Polysome analysis revealed that the wild-type PYK1, ACT1 and HSP26 mRNAs are all translated efficiently during stationary phase, when the translational apparatus is relatively inert. Also, significant levels of the translation initiation factors eIF-2alpha, eIF-4E and eIF-4A were maintained during the growth cycle. These data are consistent with the idea that, while translational activity decreases dramatically during entry into stationary phase, yeast cells maintain excess translational capacity under these conditions.

Neonatal alloimmune thrombocytopenia due to anti-HPA-1b (PLA2)(Zwb). A case report and review.

BACKGROUND: Neonatal alloimmune thrombocytopenia is a rare condition due to passively acquired maternal antibodies directed against paternal platelet antigens inherited by the infant. Only 5 cases have been reported due to antibodies against HPA-1b (PLA2) (Zwb). CASE REPORT: We report a case of neonatal alloimmune thrombocytopenia due to anti-HPA-1b in the second pregnancy of a 26-year-old Caucasian female. The male infant was treated with a 5-day course of intravenous immunoglobulin without complications. We report the HLA phenotype of the infant's mother and summarize the previous case reports due to anti-HPA-1b. CONCLUSION: Based on this case and a review of the literature, intravenous immunoglobulin as well as random donor exchange transfusion and random donor platelet transfusions are effective in the treatment of neonatal alloimmune thrombocytopenia due to anti-HPA-1b. Obvious associations between HLA alleles and sensitization to HPA-1b have not been elucidated.

Understanding iron absorption and metabolism, aided by studies of hemochromatosis.

Duodenal iron absorption from food is selectively blocked to prevent iron intoxication. The prime example of pathologic increase in intestinal iron absorption is seen in patients with hemochromatosis. They suffer iron damage to the heart, liver, and other tissues resulting in premature death if the iron is not removed by vigorous phlebotomy. Examples of overcoming the intestinal barrier to iron are alcohol consumption, vitamin preparations with vitamin C, and iron consumed by individuals without anemia. Endogenous generation of excess iron by hemolysis, owing to abnormal hemoglobin or many transfusions, are not controlled by the intestinal barrier.

Noise level analysis of commercially available toys.

There have been several isolated reports of hearing loss due to noise levels from toys. Guidelines for noise production by toys is regulated by the Voluntary Product Standards PS 72-76: Toy Safety Act of 1969. To determine the current risk of noise induced hearing loss from toys currently on the market, 25 toys were purchased at a national toy store chain and sound levels were measured at distances approximating ear level (2.5 cm) and a child's arm length (25 cm) from the surface of the toy. Testing revealed peak sound levels ranging from 81 to 126 dBA at 2.5 cm and 80 to 115 dBA at 25 cm from the surface of the toy.

Automated entry of hospital infection surveillance data.

OBJECTIVE: To assess the accuracy of an automated data entry system employing optical scanning technology and to provide an analysis of its costs as compared to manual data entry. DESIGN: The accuracy and cost of automated data entry of 100 surgical-wound infection surveillance questionnaires was compared to manual entry. SETTING: The Surgical Directorate, The Royal Hospitals, Belfast, Northern Ireland. RESULTS: The use of optical scanning technology greatly improved the speed and accuracy of data entry. The time spent by the keyboard operator on data entry was reduced substantially. For each surgical-wound infection questionnaire automatically processed, there was a saving in clerical time equivalent to $0.63. The automated data entry process resulted in a 22-fold productivity increase compared to manual data entry with validation. After validation, an error rate of < 0.2 errors per 1,000 responses was detected in automatically entered data compared to a rate of 12.4 errors per 1,000 responses for manually entered data. The automated system, including validation, provided a seven-fold productivity increase compared to "quick-and-dirty" manual data entry without validation. CONCLUSION: Hospital information technology systems may achieve total integration of data management, but realistically this would appear to be very much in the future. Until then, in view of the accuracy and substantial savings in time and money, we recommend the use of automated data entry technology. This system would be especially useful where data are transported from outlying hospitals to a central receiving center for collation and analysis.

Intermediate steps in cellular iron uptake from transferrin. II. A cytoplasmic pool of iron is released from cultured cells via temperature-dependent mechanical wounding.

A previous study described a cytoplasmic, transferrin (Tf)-free, iron (Fe) pool that was detected only when cells were mechanically detached from the culture substratum at 4 degrees C, after initial incubation with 59Fe-125I-Tf at 37 degrees C (Richardson and Baker, 1992a). The release of this internalized 59Fe could be markedly reduced if the cells were treated with proteases or incubated at 37 degrees C prior to detachment. The present study was designed to characterize this Fe pool and understand the mechanism of its release. The results show that cellular 59Fe release increased linearly as a function of preincubation time with 59Fe-Tf subsequent to mechanical detachment at 4 degrees C using a spatula. These data suggest that the 59Fe release was largely composed of end product(s) and was not an "intermediate Fe pool." When the Fe(II) chelator, dipyridyl (DP), was incubated with 59Fe-Tf and the cells, it prevented the accumulation of 59Fe that was released following mechanical detachment at 4 degrees C. Other chelators had much less effect on the proportion of 59Fe released. Examination of the 59Fe released showed that after a 4-h preincubation with 59Fe-Tf, approximately 50% of the 59Fe was present in ferritin. These data indicate that mechanical detachment of cells at 4 degrees C resulted in membrane disruptions that allow the release of high M(r), molecules. Moreover, electron microscopy studies showed that detachment of cells from the substratum at 4 degrees C resulted in pronounced membrane damage. In contrast, when cells were detached at 37 degrees C, or at 4 degrees C after treatment with pronase, membrane damage was minimal or not apparent. These results may imply that temperature-dependent processes prevent the release of intracellular contents on membrane wounding, or alternatively, prevent wounding at 37 degrees C. The evidence also indicates that caution is required when interpreting data from experiments where cells have been mechanically detached at 4 degrees C.

A decrease in glucose 6-phosphate dehydrogenase activity and mRNA is an early event in phorbol ester-induced differentiation of thp-1 promonocytic leukemia cells.

Redox modification of regulatory proteins implicates the glutathione redox system (GRS) in the control of gene expression. Glucose-6-phosphate dehydrogenase (G6PD) provides reducing equivalents for the GRS, and it has been suggested that high levels of G6PD in preneoplastic lesions are directly related to neoplastic transformation. We have used THP-1 human promonocytic leukemia cells, an established model of induced macrophage differentiation, to test an important corollary of this hypothesis, viz., that a decrease in G6PD activity should accompany the loss of the transformed phenotype. Phorbol 12-myristate 13-acetate (PMA) arrests the constitutive cycling of THP-1 and induces a phenotype that approaches normalcy. We measured the specific activities of the GRS enzymes, G6PD, glutathione peroxidase, and glutathione reductase during the early stages of phorbol ester-induced differentiation of THP-1 cells. We observed an 80% decrease in G6PD activity and an increase in the apparent KM for glucose 6-phosphate. In contrast, glutathione peroxidase (GPX) activity increased, while glutathione reductase (GR) activity remained essentially constant. The reduction in G6PD activity, preceding the loss of the transformed phenotype, is accompanied by a fourfold decrease in steady-state levels of G6PD mRNA. These findings are consistent with the hypothesis that high levels of G6PD are causally related to neoplastic transformations.