Coordinate regulation of residual bone marrow function by paracrine trafficking of AML exosomes

We recently demonstrated that acute myeloid leukemia (AML) cell lines and patient-derived blasts release exosomes that carry RNA and protein; following an in vitro transfer, AML exosomes produce proangiogenic changes in bystander cells. We reasoned that paracrine exosome trafficking may have a broader role in shaping the leukemic niche. In a series of in vitro studies and murine xenografts, we demonstrate that AML exosomes downregulate critical retention factors (Scf, Cxcl12) in stromal cells, leading to hematopoietic stem and progenitor cell (HSPC) mobilization from the bone marrow. Exosome trafficking also regulates HSPC directly, and we demonstrate declining clonogenicity, loss of CXCR4 and c-Kit expression, and the consistent repression of several hematopoietic transcription factors, including c-Myb, Cebp-β and Hoxa-9. Additional experiments using a model of extramedullary AML or direct intrafemoral injection of purified exosomes reveal that the erosion of HSPC function can occur independent of direct cell-cell contact with leukemia cells. Finally, using a novel multiplex proteomics technique, we identified candidate pathways involved in the direct exosome-mediated modulation of HSPC function. In aggregate, this work suggests that AML exosomes participate in the suppression of residual hematopoietic function that precedes widespread leukemic invasion of the bone marrow directly and indirectly via stromal components.

Mitochondrial fission triggered by hyperglycemia is mediated by ROCK1 activation in podocytes and endothelial cells

Several lines of evidence suggest that mitochondrial dysfunction plays a critical role in the pathogenesis of microvascular complications of diabetes, including diabetic nephropathy. However, the signaling pathways by which hyperglycemia leads to mitochondrial dysfunction are not fully understood. Here we examined the role of Rho-associated coiled coil-containing protein kinase 1 (ROCK1) on mitochondrial dynamics by generating two diabetic mouse models with targeted deletions of ROCK1 and an inducible podocyte-specific knockin mouse expressing a constitutively active (cA) mutant of ROCK1. Our findings suggest that ROCK1 mediates hyperglycemia-induced mitochondrial fission by promoting dynamin-related protein-1 (Drp1) recruitment to the mitochondria. Deletion of ROCK1 in diabetic mice prevented mitochondrial fission, whereas podocyte-specific cA-ROCK1 mice exhibited increased mitochondrial fission. Importantly, we found that ROCK1 triggers mitochondrial fission by phosphorylating Drp1 at serine 600 residue. These findings provide insights into the unexpected role of ROCK1 in a signaling cascade that regulates mitochondrial dynamics.

Peptide nanofibers preconditioned with stem cell secretome are renoprotective

Stem cells may contribute to renal recovery following acute kidney injury, and this may occur through their secretion of cytokines, chemokines, and growth factors. Here, we developed an acellular, nanofiber-based preparation of self-assembled peptides to deliver the secretome of embryonic stem cells (ESCs). Using an integrated in vitro and in vivo approach, we found that nanofibers preconditioned with ESCs could reverse cell hyperpermeability and apoptosis in vitro and protect against lipopolysaccharide-induced acute kidney injury in vivo. The renoprotective effect of preconditioned nanofibers associated with an attenuation of Rho kinase activation. We also observed that the combined presence of follistatin, adiponectin, and secretory leukoprotease during preconditioning was essential to the renoprotective properties of the nanofibers. In summary, we developed a designer-peptide nanofiber that can serve as a delivery platform for the beneficial effects of stem cells without the problems of teratoma formation or limited cell engraftment and viability.

Chromosomes with delayed replication timing lead to checkpoint activation, delayed recruitment of Aurora B and chromosome instability

Certain chromosome rearrangements display a significant delay in chromosome replication timing (DRT) that is associated with a subsequent delay in mitotic chromosome condensation (DMC). DRT/DMC chromosomes are common in tumor cells in vitro and in vivo and occur frequently in cells exposed to ionizing radiation. A hallmark for these chromosomes is the delayed phosphorylation of serine 10 of histone H3 during mitosis. The chromosome passenger complex, consisting of multiple proteins including Aurora B kinase and INCENP is thought to be responsible for H3 phosphorylation, chromosome condensation and the subsequent segregation of chromosomes. In this report, we show that chromosomes with DRT/DMC contain phosphorylated Chk1, consistent with activation of the S-M phase checkpoint. Furthermore, we show that INCENP is recruited to the DRT/DMC chromosomes during all phases of mitosis. In contrast, Aurora B kinase is absent on DRT/DMC chromosomes when these chromosomes lack serine 10 phosphorylation of H3. We also show that mitotic arrest deficient 2 (Mad2), a member of the spindle assembly checkpoint, is present on DRT/DMC chromosomes at a time when the normally condensed chromosomes show no Mad2 staining, indicating that DRT/DMC activates the spindle assembly checkpoint. Finally, cells with DRT/DMC chromosomes have centrosome amplification, abnormal spindle assembly, endoreduplication and significant chromosome instability.

Religion and mental health among women veterans with sexual assault experience

OBJECTIVE

Religion has been shown to have a positive impact on well-being and to play an important role in coping with stressful life events. However, the buffering effect of religiosity on mental health, after a particularly stressful life event such as sexual assault, has not been studied. In this study we examined the buffering effect of religion on mental health and depression for women who report experiencing sexual assault while in the military.

METHOD

The sample includes a nationally representative sample of 3,543 women veterans who use VA ambulatory care. Two dimensions of religiosity were used: organizational (frequency of religious service attendance) and subjective (the extent religious beliefs are a source of strength/comfort). Mental health was measured by the mental component summary (MCS) from the SF36 and depressive symptoms were measured by the Center for Epidemiologic Studies-Depression (CES-D) scale.

RESULTS

Women veterans who reported experiencing sexual assault while in the military had lower mental health scores and higher levels of depression. Linear regression analysis indicated that these negative impacts diminished with increased frequency of religious service attendance, supporting the buffering effect of organizational religiosity on mental health and depression. Although the buffering effect of subjective religiosity was not evident, subjective religiosity was shown to be positively associated with better mental health in both groups of women with and without sexual assault experience in the military.

CONCLUSIONS

Frequent religious service attendance buffers the negative impacts of sexual assault on mental health and depression of women veterans. The potential of integrating religiosity in designing interventions is discussed.

A DnaJ protein, apobec-1-binding protein-2, modulates apolipoprotein B mRNA editing

Mammalian homologues of DnaJ proteins, also known as Hsp40 proteins, are co-chaperonins that complement Hsp70 chaperone function. Using the yeast two-hybrid system, we cloned an apolipoprotein (apo) B mRNA editing complementation protein, called apobec-1-binding protein-2 (ABBP-2), and found that it is a Class II DnaJ homologue. ABBP-2 binds to apobec-1, the mammalian apoB mRNA editase, via its J domain and neighboring G/F domain. It is a ubiquitously expressed protein, and, by transfection analysis of GFP-ABBP-2, we found that the protein is located in both the nucleus and cytosol of transfected cells, with predominance in the nucleus. Down-regulation of ABBP-2 expression in cultured cells inhibits endogenous apobec-1-mediated apoB mRNA editing. Like other Hsp40 proteins, ABBP-2 binds to Hsp70 and has ATPase-stimulating activity. Apobec-1-mediated apoB mRNA editing activity of in vitro tissue extracts requires the presence of Hsp70/ABBP-2. Although exogenously added ATP is not required for editing activity, removal of the endogenous ATP present in these extracts, which disrupts ABBP-2-Hsp70 interaction, completely inhibits editing. ABBP-2 differs from previously described auxiliary proteins (ABBP-1, ACF, and GRY-RBP) in that it does not contain any RNA recognition motifs. Not only is ABBP-2 required for efficient apoB mRNA editing, this newly discovered apobec-1-binding protein may help determine the subcellular distribution and trafficking of apobec-1 via its interaction with the chaperonin Hsp70.

Meta-analysis of binary data: which within study variance estimate to use?

We applied a mixed effects model to investigate between- and within-study variation in improvement rates of 180 schizophrenia outcome studies. The between-study variation was explained by the fixed study characteristics and an additional random study effect. Both rate difference and logit models were used. For a binary proportion outcome p(i) with sample size n(i) in the ith study, (circumflexp(i)(1-circumflexp(i))n)(-1) is the usual estimate of the within-study variance sigma(i)(2) in the logit model, where circumflexpi) is the sample mean of the binary outcome for subjects in study i. This estimate can be highly correlated with logit(circumflexp(i)). We used (macronp(i)(1-macronp)n(i))(-1) as an alternative estimate of sigma(i)(2), where macronp is the weighted mean of circumflexp(i)'s. We estimated regression coefficients (beta) of the fixed effects and the variance (tau(2)) of the random study effect using a quasi-likelihood estimating equations approach. Using the schizophrenia meta-analysis data, we demonstrated how the choice of the estimate of sigma(2)(i) affects the resulting estimates of beta and tau(2). We also conducted a simulation study to evaluate the performance of the two estimates of sigma(2)(i) in different conditions, where the conditions vary by number of studies and study size. Using the schizophrenia meta-analysis data, the estimates of beta and tau(2) were quite different when different estimates of sigma(2)(i) were used in the logit model. The simulation study showed that the estimates of beta and tau(2) were less biased, and the 95 per cent CI coverage was closer to 95 per cent when the estimate of sigma(2)(i) was (macronp(1-macronp)n(i))(-1) rather than (circumflexp(i)(1-circumflexp)n(i))(-1). Finally, we showed that a simple regression analysis is not appropriate unless tau(2) is much larger than sigma(2)(i), or a robust variance is used.

Risk adjustment for measuring health outcomes: an application in VA long-term care

An empirically derived risk adjustment model is useful in distinguishing among facilities in their quality of care. We used Veterans Affairs (VA) administrative databases to develop and validate a risk adjustment model to predict decline in functional status, an important outcome measure in long-term care, among patients residing in VA long-term care facilities. This model was used to compare facilities on adjusted and unadjusted rates of decline. Predictors of decline included age, time between assessments, baseline functional status, terminal illness, pressure ulcers, pulmonary disease, cancer, arthritis, congestive heart failure, substance-related disorders, and various neurologic disorders. The model performed well in the development and validation databases (c statistics, 0.70 and 0.68, respectively). Risk-adjusted rates and rankings of facilities differed from unadjusted ratings. We conclude that judgments of facility performance depend on whether risk-adjusted or unadjusted decline rates are used. Valid risk adjustment models are therefore necessary when comparing facilities on outcomes.

Calcium/calmodulin-dependent protein kinase II inhibitor protein: localization of isoforms in rat brain

A second isoform of Ca2+/calmodulin-dependent-kinase II inhibitor protein (CaM-KIIN) has been identified using the yeast two-hybrid screen. The 1.8kb message encodes a 78 residue CaM-KIINalpha that is 65% identical in its putative open-reading frame and 95% identical in its inhibitory domain to the previously characterized CaM-KIINbeta. CaM-KIINalpha exhibits inhibitory properties towards recombinant mouse CaM-kinase IIalpha indistinguishable from CaM-KIINbeta. The 27 amino acid inhibitory peptide (CaM-KIINtide) derived from CaM-KIIN has the ability to inhibit brain CaM-kinase II activity from multiple organisms including rat, Drosophila and goldfish. Northern analysis of various rat tissues indicates that CaM-KIINalpha is specific to brain whereas CaM-KIINbeta message is also present in testis. In situ hybridization shows a general distribution of both isoforms in rat brain with stronger localization of CaM-KIINbeta in cerebellum and hindbrain and CaM-KIINalpha in frontal cortex, hippocampus and inferior colliculus. An antibody that recognizes both isoforms shows a distribution of CaM-KIIN in rat brain that correlates with immunoreactivity of CaM-kinase II. In cultured mature hippocampal neurons, CaM-KIIN is present in cell bodies and dendrites but, unlike CaM-kinase II, does not display punctate staining at synapses. These results suggest a localized function for CaM-KIIN in inhibiting specialized pools of CaM-kinase II.

Two-Hybrid Cloning Identifies an RNA-Binding Protein, GRY-RBP, as a Component of apobec-1 Editosome

ApoB mRNA editing is mediated by an editosome complex with apobec-1 as its catalytic component. By yeast two-hybrid cloning using apobec-1 as bait we identified a 69.6-kDa RNA binding protein, GRY-RBP, that contains 3 RNA-recognition motifs (RRMs) as a novel apobec-1 associating protein. GRY-RBP may be an alternatively spliced species of NASP1, a protein of known function. GRY-RBP was shown to bind to apobec-1, the catalytic component of apoB mRNA editosome, in vivo and in vitro. Immunodepletion using a monospecific rabbit antibody abolished editing in apobec-1 expressing HepG2 S-100 extracts. GRY-RBD interacted with apobec-1 through its C-terminus. It contains three RRM (RNA recognition motifs) domains that are homologous to those found in human ACF (apobec-1 complementation factor). Phylogeny analysis of the RRM domain-containing proteins indicates that GRY-RBP clusters with hnRNP-R, ACF, and ABBP-1 (another apobec-1 binding protein). In addition to its involvement with apobec-1 editosome, the suggested cellular functions of GRY-RBD and its structural homologues include RNA transport and RNA secondary structure stabilization.

Apolipoprotein B: from editosome to proteasome

Apolipoprotein (apo) B, the protein component of low-density lipoproteins (LDLs), has been under intense investigation for the last three decades. During the first decade after its initial description, most reports dealt with the physical-chemical characterization of apoB in its natural environment (i.e., intact LDL particles). A few studies dealing with attempts to elucidate the primary structure of apoB were published at this time (Deutsch et al., 1978; Bradley et al., 1980). However, most of these, in retrospect, represented heroic efforts that were doomed to failure because of the huge size and insoluble nature of apoB, once it is separated from its lipid environment. Indeed, during the 1970s, there was no universal agreement on the true molecular weight of the protein, which was not established until sometime into the second decade of apoB research (Yang et al., 1986b). The next 10 years were punctuated by breakthroughs on three different fronts in our understanding of apoB. The first exciting discovery was that apoB exists in two forms, apoB-100 and apoB-48 (Kane et al., 1980; Elovson et al., 1981). The next breakthrough was the elucidation of the primary structure of apoB-100 by a combination of cDNA cloning (Chen et al., 1986; Knott et al., 1986; Yang et al., 1986a) and direct peptide sequencing (Yang et al., 1986a, 1989). This decade of renaissance in apoB research was concluded by the elucidation of the structure of apoB-48. More important in terms of basic cellular molecular biology was the discovery of RNA editing, when apoB-48 was found to be the translation product of an edited apoB mRNA (Chen et al., 1987; Powell et al., 1987). RNA editing had just been described for a kinetoplastid protozoa the year before (Benne et al., 1986). ApoB mRNA editing was the first instance of RNA editing described in a higher eukaryote (Chan and Seeburg, 1995; Grosjean and Benne. 1998). The last decade, which brings us to the present, has been marked by studies that benefited from the breakthroughs of the 1980s. which enabled many different laboratories to examine various aspects of apoB structure, function, and expression. The function of apoB in vivo was analyzed in different animal models (e.g., transgenic animals that overexpress apoB) (Linton et al., 1993; Callow and Rubin, 1995; Veniant et al., 1997) and in knockout animals that have no functional apoB (Farese et al., 1995,1996; Huang et al., 1995,1996). Furthermore, the structure-function relationship of apoB has been investigated in mice that express site-specific apoB mutants (Callow and Rubin, 1995; Veniant et al., 1997: Borén et al., 1998). A breakthrough in a related area led to the identification and cloning of microsomal triglyceride transfer protein (MTP) (Wetterau and Zilversmitt, 1984: Wetterau et al., 1992; Sharp et al., 1993) and the demonstration that MTP is essential for apoB production (Gordon et al., 1994; Leiper et al., 1994). The absence of MTP was found to lead to the complete degradation of apoB, which harks back to an observation in 1987 that, even in the presence of MTP, a substantial proportion of newly synthesized apoB-100 undergoes intracellular degradation before secretion (Borchardt and Davis, 1987). Indeed, the intracellular degradation of apoB-100 is the major determinant of its production rate from the liver, since the transcription of apoB appears to be constitutive and not subject to much regulation (Pullinger et al., 1989). It was in 1996, almost a decade after the first description of apoB's destruction inside the cell, that the proteasome-ubiquitin pathway was found to be the major mechanism for the intracellular degradation of apoB-100 (Yeung et al., 1996). Another important development within the last decade was the cloning of APOBEC-1, the catalytic subunit of the apoB mRNA editing complex (editosome) (Teng et al., 1993). This chapter will review some of the major landmarks in apoB research in the last 10 to 15 years, concentrating mainl

Absence of perilipin results in leanness and reverses obesity in Lepr(db/db) mice

Obesity is a disorder of energy balance. Hormone-sensitive lipase (HSL) mediates the hydrolysis of triacylglycerol, the major form of stored energy in the body. Perilipin (encoded by the gene Plin), an adipocyte protein, has been postulated to modulate HSL activity. We show here that targeted disruption of Plin results in healthy mice that have constitutively activated fat-cell HSL. Plin -/- mice consume more food than control mice, but have normal body weight. They are much leaner and more muscular than controls, have 62% smaller white adipocytes, show elevated basal lipolysis that is resistant to beta-adrenergic agonist stimulation, and are cold-sensitive except when fed. They are also resistant to diet-induced obesity. Breeding the Plin -/- alleles into Leprdb/db mice reverses the obesity by ncreasing the metabolic rate of the mice. Our results demonstrate a role for perilipin in reining in basal HSL activity and regulating lipolysis and energy balance; thus, agents that inactivate perilipin may prove useful as anti-obesity medications.

Analyzing data with clumping at zero. An example demonstration

This article demonstrates the use of two approaches to analyzing the relationship of multiple covariates to an outcome which has a high proportion of zero values. One approach is to categorize the continuous outcome (including the zero category) and then fit a proportional odds model. Another approach is to use logistic regression to model the probability of a zero response and ordinary least squares linear regression to model the non-zero continuous responses. The use of these two approaches was demonstrated using outcomes data on hours of care received from the Springfield Elder Project. A crude linear model including both zero and non-zero values was also used for comparison. We conclude that the choice of approaches for analysis depends on the data. If the proportional odds assumption is valid, then it appears to be the method of choice; otherwise, the combination of logistic regression and a linear model is preferable.

Does diagnostic information contribute to predicting functional decline in long-term care?

BACKGROUND

Compared with the acute-care setting, use of risk-adjusted outcomes in long-term care is relatively new. With the recent development of administrative databases in long-term care, such uses are likely to increase.

OBJECTIVES

The objective of this study was to determine the contribution of ICD-9-CM diagnosis codes from administrative data in predicting functional decline in long-term care.

RESEARCH DESIGN

We used a retrospective sample of 15,693 long-term care residents in VA facilities in 1996.

METHODS

We defined functional decline as an increase of > or =2 in the activities of daily living (ADL) summary score from baseline to semiannual assessment. A base regression model was compared to a full model enhanced with ICD-9-CM codes. We calculated validated measures of model performance in an independent cohort.

RESULTS

The full model fit the data significantly better than the base model as indicated by the likelihood ratio test (chi2 = 179, df = 11, P <0.001). The full model predicted decline more accurately than the base model (R2 = 0.06 and 0.05, respectively) and discriminated better (c statistics were 0.70 and 0.68). Observed and predicted risks of decline were similar within deciles between the 2 models, suggesting good calibration. Validated R2 statistics were 0.05 and 0.04 for the full and base models; validated c statistics were 0.68 and 0.66.

CONCLUSIONS

Adding specific diagnostic variables to administrative data modestly improves the prediction of functional decline in long-term care residents. Diagnostic information from administrative databases may present a cost-effective alternative to chart abstraction in providing the data necessary for accurate risk adjustment.

Successful resection of cecal hepatic metastasis extending into the right side of the heart under cardiopulmonary bypass

Resection is the best hope for the cure of colorectal metastasis to the liver. However, surgery is indicated for only a few patients, especially those who have major vascular involvement. We report a 55-year-old woman with a liver metastasis from the cecum that showed a tumor thrombus in the right side of the heart. She had undergone laparoscopic right hemicolectomy for cecal cancer 6 months before, and presented with a palpable mass in the epigastrium. Abdominal ultrasonography, computed tomography, hepatic angiogram, and echocardiography showed a huge mass on the left lobe of the liver, with a tumor thrombus which extended to the right ventricle through the left hepatic vein and inferior vena cava. Tumor thrombectomy, through a right atriotomy, was success-fully performed under cardiopulmonary bypass, followed by left hepatic lobectomy. The patient's postoperative course was uneventful.

Eye examinations for VA patients with diabetes: standardizing performance measures

OBJECTIVE

To demonstrate the potential of the Health Plan Employer Data and Information Set (HEDIS) for the calculation of a performance measure for eye exams in the diabetic population using Veterans Health Administration (VA) administrative data.

DESIGN

We calculated a 1-year HEDIS-defined patient denominator and three alternative denominators that considered coding factors in identifying a VA patient as diabetic. We calculated the HEDIS-defined numerator, along with alternative specifications that captured other types of eye exams. Finally, we supplemented national data with VA pharmacy and Medicare claims data to identify all VA diabetic patients at 14 selected VA facilities and to establish a more accurate picture of non-VA health care utilization.

RESULTS

The national average annual HEDIS-defined eye exam rate in the VA was 26% in fiscal 1997 compared with 39% for managed care organizations. Medicare utilization raised this by 15 percentage points at 14 northeastern VA hospitals. Over 2 years, at least two-thirds of diabetic VA patients had some type of eye exam through VA or Medicare.

CONCLUSION

A HEDIS measure of eye exams for VA patients with diabetes can be calculated using VA administrative data only. However, the question remains to what extent the denominator and numerator accurately and completely identify all diabetic patients using VA services and all appropriate eye exams. We recommend caution in interpreting the results of performance measurement across different health care sectors based on what we currently know are data system limitations.

High polymorphism at the human melanocortin 1 receptor locus

Variation in human skin/hair pigmentation is due to varied amounts of eumelanin (brown/black melanins) and phaeomelanin (red/yellow melanins) produced by the melanocytes. The melanocortin 1 receptor (MC1R) is a regulator of eu- and phaeomelanin production in the melanocytes, and MC1R mutations causing coat color changes are known in many mammals. We have sequenced the MC1R gene in 121 individuals sampled from world populations with an emphasis on Asian populations. We found variation at five nonsynonymous sites (resulting in the variants Arg67Gln, Asp84Glu, Val92Met, Arg151Cys, and Arg163Gln), but at only one synonymous site (A942G). Interestingly, the human consensus protein sequence is observed in all 25 African individuals studied, but at lower frequencies in the other populations examined, especially in East and Southeast Asians. The Arg163Gln variant is absent in the Africans studied, almost absent in Europeans, and at a low frequency (7%) in Indians, but is at an exceptionally high frequency (70%) in East and Southeast Asians. The MC1R gene in common and pygmy chimpanzees, gorilla, orangutan, and baboon was sequenced to study the evolution of MC1R. The ancestral human MC1R sequence is identical to the human consensus protein sequence, while MC1R varies considerably among higher primates. A comparison of the rates of substitution in genes in the melanocortin receptor family indicates that MC1R has evolved the fastest. In addition, the nucleotide diversity at the MC1R locus is shown to be several times higher than the average nucleotide diversity in human populations, possibly due to diversifying selection.

Liver-specific inactivation of the abetalipoproteinemia gene completely abrogates very low density lipoprotein/low density lipoprotein production in a viable conditional knockout mouse

Conventional knockout of the microsomal triglyceride transfer protein large subunit (lMTP) gene is embryonic lethal in the homozygous state in mice. We have produced a conditional lMTP knockout mouse by inserting loxP sequences flanking exons 5 and 6 by gene targeting. Homozygous floxed mice were born live with normal plasma lipids. Intravenous injection of an adenovirus harboring Cre recombinase (AdCre1) produced deletion of exons 5 and 6 and disappearance of lMTP mRNA and immunoreactive protein in a liver-specific manner. There was also disappearance of plasma apolipoprotein (apo) B-100 and marked reduction in apoB-48 levels. Wild-type mice showed no response, and heterozygous mice, an intermediate response, to AdCre1. Wild-type mice doubled their plasma cholesterol level following a high cholesterol diet. This hypercholesterolemia was abolished in AdCre1-treated lMTP-/- mice, the result of a complete absence of very low/intermediate/low density lipoproteins and a slight reduction in high density lipoprotein. Heterozygous mice showed an intermediate lipoprotein phenotype. The rate of accumulation of plasma triglyceride following Triton WR1339 treatment in lMTP-/- mice was <10% that in wild-type animals, indicating a failure of triglyceride-rich lipoprotein production. Pulse-chase experiments using hepatocytes isolated from wild-type and lMTP-/- mice revealed a failure of apoB secretion in lMTP-/- animals. Therefore, the liver-specific inactivation of the lMTP gene completely abrogates apoB-100 and very low/intermediate/low density lipoprotein production. These conditional knockout mice are a useful in vivo model for studying the role of MTP in apoB biosynthesis and the biogenesis of apoB-containing lipoproteins.

Contributors to and mediators of psychological well-being for informal caregivers

This article explores the relationships between caregiving stressors and caregiver well-being in a representative community sample of disabled elders and their informal caregivers. The direct and indirect effects of stressors and potential mediators on the outcome of caregiver psychological well-being, as measured by depression, were examined using path analysis. Potential mediators of the primary stressors on depression included mastery, emotional support; quality of relationship between the caregiver and the care recipient, formal service use and role overload. Findings indicate that the caregiving stressors (needs for care) led to caregiver depression indirectly through their effect on hours of care provided and the resulting caregiver perception of role overload. Quality of the caregiver/care recipient relationship mediated the relationship of the caregiving stressors and caregiver overload and depression. Finally, regardless of the level of primary stressors, caregivers with high levels of mastery or emotional support were at lower risk of depression. These findings can be used to inform the design of proactive caregiver interventions.

Ca2+/calmodulin-dependent kinase II mediates simultaneous enhancement of gap-junctional conductance and glutamatergic transmission

While chemical synapses are very plastic and modifiable by defined activity patterns, gap junctions, which mediate electrical transmission, have been classically perceived as passive intercellular channels. Excitatory transmission between auditory afferents and the goldfish Mauthner cell is mediated by coexisting gap junctions and glutamatergic synapses. Although an increased intracellular Ca2+ concentration is expected to reduce gap junctional conductance, both components of the synaptic response were instead enhanced by postsynaptic increases in Ca2+ concentration, produced by patterned synaptic activity or intradendritic Ca2+ injections. The synaptically induced potentiations were blocked by intradendritic injection of KN-93, a Ca2+/calmodulin-dependent kinase (CaM-K) inhibitor, or CaM-KIINtide, a potent and specific peptide inhibitor of CaM-KII, whereas the responses were potentiated by injection of an activated form of CaM-KII. The striking similarities of the mechanisms reported here with those proposed for long-term potentiation of mammalian glutamatergic synapses suggest that gap junctions are also similarly regulated and indicate a primary role for CaM-KII in shaping and regulating interneuronal communication, regardless of its modality.

Characterization of a calmodulin kinase II inhibitor protein in brain

Ca2+/calmodulin-dependent protein kinase II (CaM-KII) regulates numerous physiological functions, including neuronal synaptic plasticity through the phosphorylation of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors. To identify proteins that may interact with and modulate CaM-KII function, a yeast two-hybrid screen was performed by using a rat brain cDNA library. This screen identified a unique clone of 1.4 kb, which encoded a 79-aa brain-specific protein that bound the catalytic domain of CaM-KII alpha and beta and potently inhibited kinase activity with an IC50 of 50 nM. The inhibitory protein (CaM-KIIN), and a 28-residue peptide derived from it (CaM-KIINtide), was highly selective for inhibition of CaM-KII with little effect on CaM-KI, CaM-KIV, CaM-KK, protein kinase A, or protein kinase C. CaM-KIIN interacted only with activated CaM-KII (i. e., in the presence of Ca2+/CaM or after autophosphorylation) by using glutathione S-transferase/CaM-KIIN precipitations as well as coimmunoprecipitations from rat brain extracts or from HEK293 cells cotransfected with both constructs. Colocalization of CaM-KIIN with activated CaM-KII was demonstrated in COS-7 cells transfected with green fluorescent protein fused to CaM-KIIN. In COS-7 cells phosphorylation of transfected alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors by CaM-KII, but not by protein kinase C, was blocked upon cotransfection with CaM-KIIN. These results characterize a potent and specific cellular inhibitor of CaM-KII that may have an important role in the physiological regulation of this key protein kinase.

The role of religion/spirituality in coping with caregiving for disabled elders

This study examined how religious/spiritual coping was related to specific conditions of caregiving and psychological distress among 127 informal caregivers to community-residing disabled elders. Support was found for the hypothesis that religious/spiritual coping influences caregiver distress indirectly through the quality of the relationship between caregiver and care recipient. Caregivers who used religious or spiritual beliefs to cope with caregiving had a better relationship with care recipients, which was associated with lower levels of depression and role submersion.

Self-reported characterization of seventh-grade students' fights

PURPOSE

To determine the characteristics of recent fights among seventh-grade students at public middle schools in three dissimilar U.S. communities.

METHODS

The study sample was composed of 289 seventh-grade students at public middle schools in three U.S. communities who participated in fights during the previous 6 months. Students at each site completed a self-administered two-part questionnaire (developed for this study) in May or October 1991. Pearson Chi-square test was performed to determine the association among characteristics of the fights, weapon use, and injury severity.

RESULTS

One or more weapons were present at 43% of the fights, weapons were used to threaten or injure in 23%, and stab or gunshot wounds were reported in 10%. Fights with five or more participants or with participants who were intoxicated or gang members involved more weapon use and more severe injury (p < 0.02). There was more frequent weapon use occurring away from home and school (p < 0.01). Spectators were present at 87% of the fights, and when they attempted to mediate or end the fighting, injury severity was lower. Students who often carry a weapon were much more likely to report involvement in fights in which weapons were used and to suffer more severe injuries (p < 0.02).

CONCLUSIONS

Seventh-graders' fights frequently involve the threat and actual use of weapons. The large number of participants and spectators at many of the fights with the most severely injurious outcomes implies that social factors and not exclusively poor conflict resolution skills are important factors precipitating fights among seventh-grade students.

Fighting and weapon-carrying among seventh-grade students in Massachusetts and Louisiana

PURPOSE

The purpose of this study was to compare attitudes toward violence and weapon-carrying among seventh-grade students in three dissimilar U.S. communities. A second focus was to determine students' understanding of their parents' violence-related guidance and behavior.

METHODS

Five hundred sixty-seven seventh-grade students (48% male, 46% white, 35% African-American, 13% Latino) completed a self-administered questionnaire in May or October 1991.

RESULTS

Thirty-four percent of the students had fought at least once, and 7% more than four times during the previous month. Also, within that period, 5% had skipped school owing to fear of violence. Students whose parents used nonviolent disciplinary techniques fought less frequently than those whose parents relied on hitting and more violent disciplinary methods (p < 0.001). Fighting was significantly more common among students who believe their parents want them to fight if insulted (p = 0.001). Students who reported that they try to stay out of fights usually succeeded (p = 0.001). Those students who more frequently participated in and observed fighting were more likely to carry a weapon (p = 0.001).

CONCLUSIONS

Fighting is a frequent occurrence in the lives of seventh-grade students. Students' understanding of their parents' attitudes and behavior correlate strongly with violent behavior. While many students feel that weapons confer safety, those students who actually carry weapons are much more likely to fight.

Evolutionary analysis of RNA editing enzymes

This article focuses on the evolution of apolipoprotein B (apoB) mRNA editing. We review the tools commonly used in homology search and phylogenetic analysis and demonstrate their use in the analysis of RNA-editing enzymes. The ultimate goal is to apply these tools to answer two questions: How did apoB mRNA editing come about? How might it be related to other base substitution editing in the course of evolution.

The relative contribution of ethnicity versus socioeconomic status in explaining differences in disability and receipt of informal care

Data from a comparative study of 1975 African American, Puerto Rican, and non-Hispanic White persons age 60 and older in a large Northeastern city were used to investigate the relative contribution of ethnicity and socioeconomic status (SES) to explaining differences in the need for and receipt of informal care. It was hypothesized that differences in disability would be related largely to SES, whereas ethnicity would account for most of the differences in the amount of informal care. The results of a path analysis argue in favor of a cultural rather than a socioeconomic explanation for between-group differences. SES had no direct effect on disability when controlling for ethnicity. Ethnicity did explain between-group differences in the amount of care. Even when controlling for disability, elders in the two minority groups received more informal care than did older White persons. The findings illuminate the important role played by ethnicity in explaining an older person's need for and receipt of long-term care assistance.

Sequence variation in ZFX introns in human populations

DNA variation in human populations was studied by examining the last intron of the ZFX gene (about 1, 151 bp) with a worldwide sample of 29 individuals. Only one polymorphic site was found, which is located in an Alu sequence. This polymorphism is present at an intermediate frequency in all populations studied, and could be a shared polymorphism or due to migration among populations in Asia, Europe, and Africa. The nucleotide diversity is 0.04%, supporting the view that the level of nucleotide variation in nuclear DNA is very low in humans. From the sequence data, the age (T) of the most recent common ancestor of the sampled sequences is estimated: the mode of T is about 306,000 years, and the 95% confidence interval of T is 162,000-952,000 years. This mode estimate is considerably older than the estimates from Y-linked sequences.

Mutation pattern variation among regions of the primate genome

We sequenced three argininosuccinate-synthetase-processed pseudogenes (PsiAS-A1, PsiAS-A3, PsiAS-3) and their noncoding flanking sequences in human, orangutan, baboon, and colobus. Our data showed that these pseudogenes were incorporated into the genome of the Old World monkeys after the divergence of the Old World and New World monkey lineages. These pseudogene flanking regions show variable mutation rates and patterns. The variation in the G/C to A/T mutation rate (u) can account for the unequal GC contents at equilibrium: 34.9, 36.9, and 41.7% in the pseudogene PsiAS-A1, PsiAS-A3, and PsiAS-3 flanking regions, respectively. The A/T to G/C mutation rate (v) seems stable and the u/v ratios equal 1.9, 1.7, and 1.4 in the flanking regions of PsiAS-A1, PsiAS-A3, and PsiAS-3, respectively. These "regional" variations of the mutation rate affect the evolution of the pseudogenes, too. The ratio u/v being greater than 1.0 in each case, the overall mutation rate in the GC-rich pseudogenes is, as expected, higher than in their GC-poor flanking regions. Moreover, a "sequence effect" has been found. In the three cases examined u and v are higher (at least 20%) in the pseudogene than in its flanking region-i.e., the pseudogene appears as mutation "hot" spots embedded in "cold" regions. This observation could be partly linked to the fact that the pseudogene flanking regions are long-standing unconstrained DNA sequences, whereas the pseudogenes were relieved of selection on their coding functions only around 30-40 million years ago. We suspect that relatively more mutable sites maintained unchanged during the evolution of the argininosuccinate gene are able to change in the pseudogenes, such sites being eliminated or rare in the flanking regions which have been void of strong selective constraints over a much longer period. Our results shed light on (1) the multiplicity of factors that tune the spontaneous mutation rate and (2) the impact of the genomic position of a sequence on its evolution.

Elevated CD8+DR+ lymphocytes in HIV-exposed infants with early positive HIV cultures: a possible early marker of intrauterine transmission. Women and Infants Transmission Study Group

The associations among timing of maternal-fetal human immunodeficiency virus (HIV) transmission, infant age at first positive HIV culture, and CD8+ lymphocyte activation were examined for 74 perinatally infected infants. Nineteen of the infected infants had positive HIV cultures at < or =7 days of life, and 55 had negative HIV cultures at < or =7 days but were positive later. Of the infants with early positive HIV-1 cultures, 15 of the 17 tested with DNA polymerase chain reaction methods had concordant results. The percentage of CD8+ and HLA-DR+ lymphocytes (CD8+DR+%) during the first week of life was significantly higher in infants with early compared with late positive cultures (median CD8+DR+% of 5.0% versus 2.0%, p = 0.0006). The CD8+DR+% was similar between uninfected infants and infants with late positive cultures during the first week of life (median 2%) but increased in infants with late positive cultures to 6% by 1 month. The CD4+% during the first 6 months of life was not different between infants with early or with late positive cultures, but infants with the highest CD8+DR+% at < or =7 days of life had significantly lower CD4+% at < or =7 days and at 1, 2, and 4 months of age. These data show that early CD8+ lymphocyte activation is associated with early positive HIV cultures and lower CD4+ percentages during early infancy and are consistent with the hypothesis that early positive cultures positivity may indicate in utero HIV infection.

Sex differences in mutation rate in higher primates estimated from AMG intron sequences

To study sex differences in mutation rate in primates, we sequenced the third introns of the AMGX and AMGY genes from humans, orangutans, and squirrel monkeys and estimated that the male-to-female ratio of mutation rate is alpha = 5.14 with the 95% confidence interval (2.42, 16.6). Combining this data set and the data sets from ZFX/ZFY and SMCX/SMCY introns, we obtained an estimate of alpha = 5.06 with the 95% confidence interval reduced to (3.24, 8.79). The alpha value is significantly higher in higher primates than in rodents.

Apobec-1 and apolipoprotein B mRNA editing

Apolipoprotein (apo)B mRNA editing is a novel mechanism for the post-transcriptional regulation of gene expression in mammals. It consists of a C-->U conversion of the first base of the codon CAA, encoding glutamine-2153, to UAA, an in-frame stop codon, in apoB mRNA. Since its initial description in 1987, substantial progress has been made in the last few years on the mechanism of editing. Apobec-1, the catalytic component of the apoB mRNA editing enzyme complex, has been cloned. This article begins with an overview of the general biology of apoB mRNA editing. It then provides an in-depth analysis of the structure, evolution and possible mechanism of action of apobec-1. ApoB mRNA editing is the prototype of RNA editing in mammals. What we learn from apoB mRNA editing will be useful in our understanding of other examples of RNA editing in vertebrates which are being described with increasing frequency.

Vaginal colonization or infection with Candida albicans in human immunodeficiency virus-infected women during pregnancy and during the postpartum period. Women and Infants Transmission Study Group

We evaluated the relationship between immunologic status and vaginal colonization or infection with Candida albicans for 605 women enrolled in a multicenter, prospective cohort study of mother-to-infant transmission of human immunodeficiency virus type 1 (HIV-1). A low CD4+ lymphocyte level (< 14% vs. > or = 14%, which corresponds to an absolute count of approximately 200 x 10(6)/L) was associated with a two- to fivefold increased likelihood of vaginal colonization (odds ratio [OR], 2.28; 95% confidence interval [CI], 1.01-5.19) and vaginal candidiasis (OR, 3.08; 95% CI, 1.21-7.71) during pregnancy and during the postpartum period (OR, 2.98; 95% CI, 1.51-5.88 and OR, 5.45; 95% CI, 1.73-16.6, respectively). These associations persisted in multivariate logistic regression analyses. No associations with CD8+ lymphocyte levels or CD8+ CD38+ or other lymphocyte subset levels were found after adjustment for CD4+ cell level and other covariates. However, postpartum (but not antepartum) antibiotic use and pregnancy were also associated with vaginal colonization and candidiasis (P < or = .001 for each). Vaginal candidiasis was not associated with an increased risk of mother-to-infant transmission of HIV-1; however, a related, more inclusive variable, clinical vaginitis or vaginosis of any etiology at the last antepartum visit, was associated with mother-to-infant transmission (OR, 1.92; 95% CI, 1.07-3.43). These findings emphasize the complex, multifactorial nature of vaginal candidiasis and highlight the need for safe and effective treatment and prevention strategies for women with advanced HIV infection.

Large-Scale Synthesis of Aligned Carbon Nanotubes

Large-scale synthesis of aligned carbon nanotubes was achieved by using a method based on chemical vapor deposition catalyzed by iron nanoparticles embedded in mesoporous silica. Scanning electron microscope images show that the nanotubes are approximately perpendicular to the surface of the silica and form an aligned array of isolated tubes with spacings between the tubes of about 100 nanometers. The tubes are up to about 50 micrometers long and well graphitized. The growth direction of the nanotubes may be controlled by the pores from which the nanotubes grow.

Complete phenotypic characterization of apobec-1 knockout mice with a wild-type genetic background and a human apolipoprotein B transgenic background, and restoration of apolipoprotein B mRNA editing by somatic gene transfer of Apobec-1

We have produced gene knockout mice by targeted disruption of the apobec-1 gene. As recently reported by Hirano et al. (Hirano, K.-I., Young, S. G., Farese, R. V., Jr., Ng, J., Sande, E., Warburton, C., Powell-Braxton, L. M., and Davidson, N. O. (1996) J. Biol. Chem. 271, 9887-9890), these animals do not edit apolipoprotein (apo) B mRNA or produce apoB-48. In this study we have performed a detailed analysis of the lipoprotein phenotypic effects of apobec-1 gene disruption that were not examined in the previous study. We first analyzed the plasma lipoproteins in knockout animals with a wild-type genetic background. Although there was no difference in plasma cholesterol between apobec-1(-/-), +/-, or +/+ mice, there was a marked (176%) increase in plasma apoB-100, from 1.8 +/- 1.2 mg/dl in apobec-1(+/+) mice to 2.7 +/- 0.6 mg/dl in apobec-1(+/-) and 5.0 +/- 1.4 mg/dl in apobec-1(-/-) mice. Plasma apoE was similar in these animals. By fast protein liquid chromatography (FPLC) analysis, there was a significant decrease in plasma high density lipoprotein (HDL) cholesterol in apobec-1(-/-) mice. We further fractionated the plasma lipoproteins into d < 1.006, 1.006-1.02, 1.02-1.05, 1.05-1.08, 1.08-1.10, and 1.10-1.21 g/ml classes, and found a marked (30-40%) reduction in the cholesterol and protein content in the (d 1.08-1.10 and 1.10-1.21) HDL fractions, corroborating the FPLC data. SDS-gel analysis revealed an absence of apoB-48, an increase in apoB-100 in the very low density lipoprotein (VLDL) and low density lipoprotein (LDL) fractions, and a small decrease in apoA-I in the HDL fractions in the apobec-1(-/-) samples. We next raised the basal plasma apoB levels in the apobec-1(-/-) animals by cross-breeding them with human apoB transgenic (TgB) mice. The plasma apoB-100 was 3-fold higher in apobec-1(-/-)/TgB+/- mice (26.6 +/- 18.3 mg/dl) than in apobec-1(+/+)/TgB+/- mice (9.8 +/- 3.9 mg/dl, p < 0.05). The apobec-1(-/-)/TgB+/- mice had a plasma cholesterol levels of 170 +/- 28 mg/dl and triglyceride levels of 106 +/- 31 mg/dl, which are 80% and 58% higher, respectively, than the corresponding values of 94 +/- 21 mg/dl and 67 +/- 11 mg/dl in apobec+/+/TgB+/- mice. By FPLC, the apobec-1(-/-)/TgB+/- animals developed markedly elevated plasma LDL cholesterol (518.5 +/- 329.5 microg/ml) that is 373% that of apobec1(+/+)/TgB+/- mice (139.0 +/- 87.0 microg/ml) (p < 0.05). The elevated plasma triglyceride was accounted for mainly by a 97% increase in VLDL triglyceride in the apobec1(-/-)/TgB+/- mice. We conclude that apobec-1(-/-) animals have a distinctive lipoprotein phenotype characterized by significant hyperapoB-100 and HDL deficiency in mice with a wild-type genetic background. Furthermore, the abolition of apoB mRNA editing elevates plasma total cholesterol and LDL cholesterol in apobec-1(-/-) animals with a TgB background. Finally, to exclude the possibility that absence of apoB mRNA editing was a secondary effect of chronic Apobec-1 deficiency, we treated apobec-1(-/-) mice with a replication-defective mouse Apobec-1 adenoviral vector and found that we could acutely restore apoB mRNA editing in the liver. These experiments indicate that Apobec-1 is an essential component of the apoB mRNA editing machinery and absence of editing in the knockout animals is a direct consequence of the absence of functional Apobec-1.

Early detection of human immunodeficiency virus on dried blood spot specimens: sensitivity across serial specimens. Women and Infants Transmission Study Group

OBJECTIVE

To evaluate the use of dried blood spot (DBS) specimens and the early diagnostic value of the polymerase chain reaction (PCR) for detection of the human immunodeficiency virus (HIV) in DBS specimens collected at predefined age intervals from a large cohort of U.S. infants at risk of congenital or perinatal HIV infection.

DESIGN

We assayed available DBS specimens (n = 272) obtained during the first 4 months of life from 144 infants (41 infected, 103 uninfected) born to HIV-infected mothers enrolled in the Women and Infants Transmission Study. The DBS PCR results were compared with infant HIV infection status, PCR on liquid blood, and viral culture results. Analyses also included sensitivity and specificity of assay as related to the age of the infant when the specimen was obtained.

RESULTS

The DBS specimen PCR results were concordant with results from liquid blood specimens and with results from viral culture. The DBS PCR was highly specific for all age groups. Sensitivity in detecting HIV infection status rapidly increased during the first month of life, from 19% (5/26) by 1 week to 96% (25/26) by 1 month of age. Specimens obtained on the day of birth or the next day were the least likely to have detectable HIV DNA.

CONCLUSIONS

The PCR assay of DBS specimens is a reliable tool for the early diagnosis of HIV infection and has important advantage over that of liquid blood DNA PCR and viral culture. These advantages include a lower volume of blood required for testing, increased safety, and ease of storage or transport of specimens. Thus DBS PCR is a useful test for clinical and epidemiologic tracking of infants at risk of HIV infection.

Mouse microsomal triglyceride transfer protein large subunit: cDNA cloning, tissue-specific expression and chromosomal localization

Microsomal triglyceride transfer protein (MTP) catalyzes the transfer of triglyceride, cholesteryl ester, and phospholipid between membranes. It is essential for the secretion of apolipoprotein B from the cell. Mutations in MTP are a major cause of abetalipoproteinemia. The mouse is a popular animal model for lipoprotein metabolism. We have cloned and sequenced mouse MTP cDNA. The DNA-deduced amino acid sequence indicates that mouse MTP contains 894 amino acids; the mouse protein shows 93, 86, and 83% sequence identity to the hamster, human, and bovine sequences, respectively. Northern blot analysis indicates that mouse MTP mRNA is expressed at high levels in the small intestine and at substantially lower levels in the liver and that it is not detectable in six other tissues examined. The mouse MTP gene has been localized to the distal region of chromosome 3 by Southern blots of interspecific backcross panels using progeny derived from matings of (C57BL/6J x SPRET/Ei)F1 x SPRET/Ei. Comparison of MTP sequences from human, bovine, hamster, and mouse indicates that the C-terminal region of MTP is better conserved than its N-terminal region.

Association of maternal drug use during pregnancy with maternal HIV culture positivity and perinatal HIV transmission

OBJECTIVE

To evaluate the relationship of drug use with maternal HIV culture positivity at delivery and perinatal HIV transmission.

DESIGN

Multicenter prospective cohort study.

SETTING

Obstetric and pediatric clinics in five cities in the United States.

PARTICIPANTS

Five hundred and thirty HIV-infected pregnant women and their infants.

MAIN OUTCOME MEASURES

Multivariate logistic regression was used to evaluate the association of 'hard drug' use (one or more of the following: cocaine, heroin/opiates, methadone, injecting drug use) assessed by self-report and urine toxicology with positive maternal HIV culture at delivery and perinatal HIV transmission.

RESULTS

Forty-two per cent of women used hard drugs during pregnancy. Increased probability of a positive maternal delivery HIV culture was significantly associated with prenatal hard drug use [odds ratio (OR), 3.08] and maternal cocaine use (OR, 2.98) among HIV-infected women with > 29% CD4+ lymphocytes. After adjusting for maternal culture positivity at delivery, CD4+ lymphocyte percentage and gestational age, significantly greater transmission risk was observed with hard drug use among women with membrane rupture > 4 h.

CONCLUSIONS

On the basis of self-report and urine toxicology, overall maternal hard drug use and cocaine use in the WITS cohort were associated with maternal HIV culture positivity at delivery, and maternal hard drug use was associated with perinatal transmission.

Rates of nucleotide substitution in primates and rodents and the generation-time effect hypothesis

DNA sequence data from introns, flanking regions, and the eta globin pseudogene region all show a significantly higher rate of nucleotide substitution in the Old World monkey lineage than in the human lineage after the separation of the two lineages, or, in other words, the data support the hominoid rate-slowdown hypothesis. Data from both protein sequences and DNA sequences show that the rate of evolution is significantly higher in the rodent lineage than in the primate lineage. Furthermore, DNA sequences from introns show that the rate of nucleotide substitution is at least two times higher in rodents than in higher primates. The male-to-female ratio of mutation rate is estimated to be between 3 and 6 in higher primates, whereas it is only 2 in mice and rats. These ratios are similar to the corresponding male-to-female ratios of germ cell divisions in higher primates and in rodents, suggesting that errors in DNA replication during germ cell division are the primary source of mutation, or, in other words, mutation is largely DNA replication-dependent. This conclusion provides further support for the generation-time effect hypothesis.

Identification in the calcineurin A subunit of the domain that binds the regulatory B subunit

Calcineurin (CaN) is the serine/threonine protein phosphatase (phosphatase 2B) that is activated by binding of Ca2+ to its B subunit and to calmodulin (CaM). This paper identifies residues between the catalytic region and the CaM-binding domain of the A subunit as the domain that binds the regulatory B subunit. A purified fusion protein containing residues 328-390 of the A subunit 1) binds CaN B subunit, and 2) inhibits (IC50 = 0.1 microM) the in vitro stimulation of CaN A phosphatase activity by purified CaN B subunit. A synthetic peptide corresponding to residues 341-360 blocked the binding of CaN B to residues 328-390 in the fusion protein, so 4 hydrophobic residues within this region (Val349-Phe350 and Phe356-Val357) were mutated to either Glu (E mutant) or Gln (Q mutant). The wild-type and mutant A subunits were expressed individually or coexpressed with B subunit in Sf9 cells, purified and characterized. The mutant A subunits were similar to wild-type A subunit in terms of basal phosphatase activity (1-3 nmol/min/mg) and activation by Mn2+/CaM. Addition of purified B subunit to purified wild-type A subunit at a 1:1 molar ratio gave a 40-fold increase in phosphatase activity whereas addition of B subunit to either of the mutant A subunits had no effect on phosphatase activity, even at a 3:1 molar excess of B subunit. Furthermore, when wild-type or mutant A subunits were coexpressed with B subunit and purified on CaM-Sepharose, the B subunit co-eluted with the wild-type A subunit but not with either mutant A subunit. These results demonstrate that residues 328-390 in the A subunit bind B subunit and that the mutated hydrophobic residues are essential.

Estimating the intensity of male-driven evolution in rodents by using X-linked and Y-linked Ube 1 genes and pseudogenes

Using sequence data from the last introns of ZFX and ZFY genes, we previously estimated the male-to-female ratio (alpha) of mutation rate to be close to 6 in higher primates and 1.8 in rodents. As the mutation rate may vary among different regions of the mammalian genome, it is interesting to see whether sequence data from other regions will give similar estimates. In this study, we have determined the partial genomic sequences of the ubiquitin-activating enzyme E1 genes (Ube 1x and Ube 1y for the X-linked and Y-linked homologues, respectively) of mice and rats and two mouse Ube 1y pseudogenes. From the intron sequences of the Ube 1 genes, we calculated the divergence of the Y-linked genes (Y = 0.161) and that of the X-linked genes (X = 0.107) between mouse and rat, and found the Y/X ratio to be 1.50. This ratio led to an estimate of alpha = 2.0 with a 95% confidence interval of (1.0, 3.9). Similar estimates of alpha were obtained if mouse Ube 1y pseudogenes were used instead of the mouse Ube 1y functional gene. These estimates are consistent with our previous estimate for rodents and suggest that the sex ratio of mutation rate in rodents is approximately only one-third of that in higher primates. Our estimate of the divergence time between Ube 1x and Ube 1y supports the view that the two genes separated before the eutherian radiation.

Contrasting rates of nucleotide substitution in the X-linked and Y-linked zinc finger genes

We have sequenced the entire exon (approximately 1.180 bp) encoding the zinc finger domain of the X-linked and Y-linked zinc finger genes (ZFX and ZFY, respectively) in the orangutan, the baboon, the squirrel monkey, and the rat; a total of 9,442 bp were sequenced. The ratio of the rates of synonymous substitution in the ZFY and ZFX genes is estimated to be 2.1 in primates. This is close to the ratio of 2.3 estimated from primate ZFY and ZFX intron sequences and supports the view that the male-to-female ratio of mutation rate in humans in considerably higher than 1 but not extremely large. The ratio of synonymous substitution rates in ZFY and ZFX is estimated to be 1.3 in the rat lineage but 4.2 in the mouse lineage. The former is close to the estimate (1.4) from introns. The much higher ratio in the mouse lineage (not statistically significant) might have arisen from relaxation of selective constraints. The synonymous divergence between mouse and rat ZFX is considerably lower than that between mouse and rat autosomal genes, agreeing with previous observations and providing some evidence for stronger selective constraints on synonymous changes in X-linked genes than in autosomal genes. At the protein level ZFX has been highly conserved in all placental mammals studied while ZFY has been well conserved in primates and foxes but has evolved rapidly in mice and rats, possibly due to relaxation of functional constraints as a result of the development of X-inactivation of ZFX in rodents. The long persistence of the ZFY-ZFX gene pair in mammals provides some insight into the process of degeneration of Y-linked genes.

Intronic gene conversion in the evolution of human X-linked color vision genes

Human red and green visual pigment genes are X-linked duplicate genes. To study their evolutionary history, introns 2 and 4 (1,987 and 1,552 bp, respectively) of human red and green pigment genes were sequenced. Surprisingly, we found that intron 4 sequences of these two genes are identical and that the intron 2 sequences differ by only 0.3%. The low divergences are unexpected because the duplication event producing the two genes is believed to have occurred before the separation of the human and Old World monkey (OWM) lineages. Indeed, the divergences in the two introns are significantly lower than both the synonymous divergence (3.2% +/- 1.1%) and the nonsynonymous divergence (2.0% +/- 0.5%) in the coding sequences (exons 1-6). A comparison of partial sequences of exons 4 and 5 of human and OWM red and green pigment genes supports the hypothesis that the gene duplication occurred before the human-OWM split. In conclusion, the high similarities in the two intron sequences might be due to very recent gene conversion, probably during evolution of the human lineage.

Weak male-driven molecular evolution in rodents

In humans and rodents the male-to-female ratio of mutation rate (alpha m) has been suggested to be extremely large, so that the process of nucleotide substitution is almost completely male-driven. However, our sequence data from the last intron of the X chromosome-linked (Zfx) and Y chromosome-linked (Zfy) zinc finger protein genes suggest that alpha m is only approximately 2 in rodents with a 95% confidence interval from 1 to 3. Moreover, from published data on oogenesis and spermatogenesis we estimate the male-to-female ratio of the number of germ cell divisions per generation to be approximately 2 in rodents, confirming our estimate of alpha m and suggesting that errors in DNA replication are the primary source of mutation. As the estimated alpha m for rodents is only one-third of our previous estimate of approximately 6 for higher primates, there appear to be generation-time effects--i.e., alpha m decreases with decreasing generation time.

The essential mitotic target of calmodulin is the 110-kilodalton component of the spindle pole body in Saccharomyces cerevisiae

Two independent methods identified the spindle pole body component Nuf1p/Spc110p as the essential mitotic target of calmodulin. Extragenic suppressors of cmd1-1 were isolated and found to define three loci, XCM1, XCM2, and XCM3 (extragenic suppressor of cmd1-1). The gene encoding a dominant suppressor allele of XCM1 was cloned. On the basis of DNA sequence analysis, genetic cosegregation, and mutational analysis, XCM1 was identified as NUF1/SPC110. Independently, a C-terminal portion of Nuf1p/Spc110p, amino acid residues 828 to 944, was isolated as a calmodulin-binding protein by the two-hybrid system. As assayed by the two-hybrid system, Nuf1p/Spc110p interacts with wild-type calmodulin and triple-mutant calmodulins defective in binding Ca2+ but not with two mutant calmodulins that confer a temperature-sensitive phenotype. Deletion analysis by the two-hybrid system mapped the calmodulin-binding site of Nuf1p/Spc110p to amino acid residues 900 to 927. Direct binding between calmodulin and Nuf1p/Spc110p was demonstrated by a modified gel overlay assay. Furthermore, indirect immunofluorescence with fixation procedures known to aid visualization of spindle pole body components localized calmodulin to the spindle pole body. Sequence analysis of five suppressor alleles of NUF1/SPC110 indicated that suppression of cmd1-1 occurs by C-terminal truncation of Nuf1p/Spc110p at amino acid residues 856, 863, or 881, thereby removing the calmodulin-binding site.

Potential problems in estimating the male-to-female mutation rate ratio from DNA sequence data

It is commonly believed that the rate of mutation is much higher in males than in females because the number of germ-cell divisions per generation is much larger in males than in females. However, the precise magnitude of the male-to-female mutation rate ratio (alpha m) remains unknown. Recently there have been efforts to estimate alpha m by using DNA sequence data from different species. We have studied the potential problems in such an approach. We found that the rate of synonymous substitution varies about fivefold among X-linked genes, as large as the variation among autosomal genes. This large variation makes the assumption of selective neutrality of synonymous changes dubious, so one should be cautious in using the synonymous rates in X-linked and autosomal genes to estimate alpha m. A similar difficulty was also observed in using nonhomologous intron sequences to estimate alpha m. Contrary to the expectation that X-linked sequences should evolve more slowly than autosomal sequences, the Alu repeat in the last intron of the X-linked zinc finger gene has evolved faster than the four autosomal Alu repeats used in this study. It appears that the best way to estimate alpha m is to use homologous sequences. However, such sequences may be involved in gene conversion events. In fact, we found evidence that the Y-linked and X-linked zinc finger genes have been involved in multiple conversion events during primate evolution. Thus, the possibility of gene conversion should be considered when using homologous sequences to estimate alpha m.

Male-driven evolution of DNA sequences

It is commonly believed that the mutation rate is much higher in the human male germ line than in the female germ line because the number of germ-cell divisions per generation is much larger in males than in females. But direct estimation of mutation rates is difficult, relying mainly on sex-linked genetic diseases, so the ratio (alpha m) of male to female mutation rates is not clear. It has been noted that if alpha m is very large, then the rate of synonymous substitution in X-linked genes should be only 2/3 of that in autosomal genes, and comparison of human and rodent genes supported this prediction. As the number of X-linked genes used in the study was small and the X-linked and autosomal sequences were non-homologous, and given that the synonymous rate varies among genes, we sequenced the last intron (approximately 1 kb) of the Y-linked and X-linked zinc-finger-protein genes (ZFY and ZFX) in humans, orang-utans, baboons and squirrel monkeys. The ratio Y/X of the substitution rate in the Y-linked intron to that in the X-linked intron is approximately 2.3, which is close to that estimated from synonymous rates in the ZFY and ZFX genes and implies alpha m approximately 6. This estimate of alpha m supports the view that the evolution of DNA sequences in higher primates is male-driven. It is, however, much lower than the previous estimate and therefore raises a number of issues.

A new method for making interstate comparisons of highway fatality rates

Highway fatality rates vary significantly among jurisdictions. Before attributing these variations to policy differences, it is important to account for exogenous factors (e.g. weather) that are beyond the control of policy makers. A new method is developed to identify states that are doing better or worse than expected. The method is applied to the 48 contiguous American states using highway fatality data for the years 1975 to 1986. A fixed effects linear model is used to estimate the fatality rate for each state, taking into account exogenous factors. Results indicate that many states have higher or lower fatality rates than is expected based on a ranking of states according to crude fatality rates. Policy implications are discussed.

The cost of medical care for injuries to children

STUDY OBJECTIVES

To estimate the mean cost of initial medical treatment for a variety of injury types and injury causes and project the national cost of initial medical care for injuries to children.

DESIGN

We combined injury incidence data from the Massachusetts Statewide Childhood Injury Prevention Project (SCIPP) with a claims data set (1987 charges) from the Health Data Institute, Lexington, Massachusetts.

SETTING AND STUDY POPULATION

SCIPP incidence data were obtained from hospital emergency department and inpatient facilities for a population of 87,000 Massachusetts children 0 to 19 years old between 1979 and 1982. Health Data Institute charge data for children were derived from insurance claims for 3% of all privately insured patients throughout the United States.

RESULTS

The estimated mean cost of initial hospitalization for injury was $5,094, while ED care was $171. Projected annual cost for initial medical care of injury to children for the nation was $5.1 billion, which was about equally divided between cases seen in EDs and those requiring inpatient care. Although there was little difference in mean cost between the genders, mean cost increased with age. Because of both a higher injury incidence and a greater mean cost per injury, the projected initial cost of injuries to teenagers 15 to 19 years old was much higher than that of younger children.

CONCLUSION

Expenditures for medical care of injured children, particularly adolescents, are great. The prevention of childhood injuries should become a higher priority in the United States. To improve the quality of national estimates of the incidence and cost of injury, a national surveillance system for nonfatal injuries should be developed. Such a system should include information on the major causes of injury and their costs.