The prevalence of domestic violence in pregnant women

OBJECTIVE

To determine the prevalence of domestic violence in a population of pregnant women.

DESIGN

Questionnaire survey.

SETTING

Antenatal booking clinic in a north of England hospital.

POPULATION

Five hundred consecutive women were included.

METHODS

Anonymous confidential questionnaire to women who were not accompanied by their partners.

MAIN OUTCOME MEASURES

Disclosure of a past history of physical, emotional or sexual abuse.

RESULTS

Four hundred and seventy-five questionnaires were returned (95% response rate). The prevalence of domestic violence was 17%. Domestic violence was highest in the age group 26-30 years and boyfriends were the main perpetrators. Punching and slapping were the most common pattern of violence, and 10% of women experiencing domestic violence had had forced sexual activity.

CONCLUSIONS

The prevalence of domestic violence in a cohort of pregnant women in the north of England was 17%. Consideration should be given for routine screening for domestic violence in pregnancy to institute effective intervention strategies.

A potential role for phenylalanine hydroxylase in mosquito immune responses

In mosquitoes the melanotic encapsulation immune response is an important resistance mechanism against filarial worms and malaria parasites. The rate limiting substrate for melanin production is tyrosine that is hydroxylated by phenoloxidase (PO) to produce 3, 4-dihydroxyphenylalanine. The single pathway for endogenous production of tyrosine is by hydroxylation of phenylalanine by phenylalanine hydroxylase (PAH). In this study we describe a potential role for PAH in melanotic immune responses in the yellow fever mosquito, Aedes aegypti. A 1.6 kb A. aegypti PAH cDNA, encoding a 51 kDa protein, was isolated and subsequently expressed in an Escherichia coli expression system. In developing mosquitoes, PAH transcript is present in all stages and it is differentially expressed in adult tissues. Following an immune-challenge with Dirofilaria immitis microfilariae (mf) or bacteria, PAH transcript is up-regulated in hemocytes. Likewise, western analysis of hemocytes collected from immune-activated mosquitoes show an increase in gene product over control samples. Like PO, ultrastructure observations provide verification that PAH is located in oenocytoid and granulocyte hemocytes. Our results offer the first data that suggest PAH is used in mosquito melanin synthesis and defense responses.

Auditory event-related potentials during target detection are abnormal in mild cognitive impairment

OBJECTIVE

To define brain activity and behavioral changes in mild cognitive impairment (MCI), an isolated memory deficit in the elderly that is a major risk factor for Alzheimer's disease.

METHODS

Brain potentials and reaction time were examined in elderly controls (n=12) and MCI (n=15) using a target detection paradigm. Subjects listened to a sequence of tones and responded to high-pitched target tones (P=0.20) that were randomly mixed with low-pitched tones (P=0.80). Measures were a pre-stimulus readiness potential (RP), post-stimulus potentials (P50, N100, P200, N200, P300), and reaction time.

RESULTS

Accuracy was equivalent between groups, but there was a trend for longer reaction times in MCI (P=0.08). Two potentials differed between groups: (1) P50 amplitude and latency were significantly increased in MCI, and (2) P300 latency was significantly longer in MCI. Results from two MCI subjects that converted to Alzheimer's disease are also discussed.

CONCLUSIONS

Brain potentials in MCI subjects during target detection have certain features similar to healthy aging (RP, N100, P200, N200), and other features similar to Alzheimer's disease (delayed P300 latency, slower reaction time). P50 differences in MCI may reflect pathophysiological changes in the modulation of auditory cortex by association cortical regions having neuropathological changes in early Alzheimer's disease.

Oxidation of Abeta and plaque biogenesis in Alzheimer's disease and Down syndrome

The processes involved with beta-amyloid (Abeta) degradation and clearance in human brain are not well understood. We hypothesized that the distribution of oxidatively modified Abeta, as determined by an affinity-purified antibody in the entorhinal and frontal cortices of Alzheimer's disease (AD), Down syndrome (DS), nondemented elderly control cases, and canine brain, would provide insight into the mechanisms of Abeta accumulation. Based upon plaque counts, oxidized Abeta was present within 46-48% of diffuse and primitive plaques and 98% of cored plaques. Dense punctate deposits of oxidized Abeta were distributed throughout the neuropil in AD and DS brains but were also present within controls with mild neuropathology and isolated cognitive impairments. Confocal studies indicate that punctate oxidized Abeta deposits were within activated microglia. Oxidatively modified Abeta may reflect the efforts of microglial cells to take up and degrade Abeta. Oxidative modification of Abeta may be an early event in Abeta pathogenesis and may be important for plaque biogenesis.

Cloning and characterization of a dopachrome conversion enzyme from the yellow fever mosquito, Aedes aegypti

In this study we describe the purification and molecular cloning of a dopachrome conversion enzyme (DCE) from the yellow fever mosquito, Aedes aegypti. DCE catalyzes the conversion of L-dopachrome to 5,6-dihydroxyindole in the melanization pathway. Melanin biosynthesis is involved with crucial protective phenomena in mosquitoes, including egg chorion and cuticular tanning, wound healing, and the melanotic encapsulation immune response. The enzyme was purified to homogeneity by various chromatographic techniques from A. aegypti larvae and has a relative molecular mass of 51 kDa as-revealed by SDS-PAGE analysis. Physiochemical analysis of DCE revealed a pH optimum of 7.5-8.0 and substrate activity for L-dopachrome and aminochromes generated from dopa methyl ester, alpha-methyl dopa and dopamine. Trypsin digestion of the isolated DCE and subsequent reverse-phase separation resulted in the isolation of several polypeptide fragments, from which two partial internal amino acid sequences were obtained by Edman degradation. PCR amplification, using a degenerate primer based on one internal amino acid sequence and an oligo-dT primer, produced a 650 bp DNA fragment. Subsequent screening of an A. aegypti pupal cDNA library resulted in the isolation of a 1.6 kb clone containing coding sequence for both internal DCE amino acid sequences, thereby confirming the identity of the isolated gene product (pAaDce1) as DCE. Northern analysis revealed the constitutive expression of DCE message in developmental stages and adults, with the majority of transcript localized in the fat body and ovaries of adult females. AaDce1 mRNA increased in abundance above constitutive levels in adult females when a melanotic encapsulation immune response was initiated by the intrathoracic inoculation of Dirofilaria immitis microfilariae.

Sensory cortical interactions in aging, mild cognitive impairment, and Alzheimer's disease

Progressive declines in memory function accompany normal aging, mild cognitive impairment (MCI), and Alzheimer's disease (AD). Neuropathological studies suggest that damage to neurons providing connections between cortical areas may contribute to memory impairments in AD. Because AD develops slowly, similar neuropathological changes, to a lesser degree, may be present in MCI and some asymptomatic elderly subjects. In this study we tested the hypothesis that corticocortical interactions between sensory regions are impaired in aging, MCI, and AD, as compared with young subjects. When sensory cortical evoked potentials are elicited by pairs of stimuli the amplitudes of potentials to the second stimulus are attenuated. Corticocortical interactions were assessed by presenting stimulus pairs in different modalities (auditory/visual). There were significant group differences in the degree that a visual stimulus attenuated subsequent auditory potentials (young > healthy elderly > MCI > AD). Control experiments indicated equivalent amplitude reductions for all groups to the second stimulus for stimulus pairs having the same modality. These findings are compatible with progressive declines in corticocortical processing in aging, MCI, and AD.

Factors associated with HIV-infected women's use or intention to use AZT during pregnancy

Despite the effectiveness of the antiviral drug AZT (zidovudine) in reducing perinatal transmission, many HIV-infected women continue to have reservations about taking the medication during pregnancy. To examine the factors influencing HIV-infected women's willingness to take AZT during pregnancy, focused interviews were conducted with 51 HIV-infected women of reproductive age living in New York City. Nearly all the women held reservations about taking it during pregnancy. Barriers to their use of AZT during pregnancy included (a) fear of toxic effects on baby, (b) fear of toxic effects for themselves, (c) fear of drug resistance, (d) belief that AZT is unnecessary among "healthy" women, and (e) previous birth to a healthy baby without using AZT. However, several factors also positively increased women's willingness to take AZT during pregnancy: (a) belief that they owe it to the baby to take AZT, (b) positive relationships with their physician, (c) peers or friends have taken AZT during pregnancy, and (d) previous experience taking AZT during pregnancy. These findings suggest significant areas for intervention to increase the use of AZT during pregnancy, thereby reducing perinatal transmission.

Testing between-family associations in within-family comparisons

Using behaviorally discordant siblings to test for gene-behavior associations is a common tool in molecular genetics, because the within-family contrast offers a research design that avoids confounds inevitable in all between-family comparisons of unrelated individuals. We propose a similar strategy to assess the behavior-behavior associations on which much of psychological science is built. Between-family correlations of personality test scores (e.g., sensation seeking) and behavioral outcomes (e.g., substance use) may be mediated by variables that differ between families (e.g., social class or religiosity) and correlate with both personality and outcome. Contrasting twin and nontwin siblings who were highly discordant for behavioral correlates of substance use, we tested whether between-family behavioral correlations replicated within families. Some, but not all, did. Within-family analyses of behaviorally discordant siblings may find wide application in efforts to clarify the meaning of correlational research data.

Sensory evoked potentials in SIV-infected monkeys with rapidly and slowly progressing disease

Human immunodeficiency virus (HIV-1) infects the central nervous system (CNS) early in the course of disease progression and leads to some form of neurological disease in 40-60% of cases. Both symptomatic and asymptomatic HIV-infected subjects also show abnormalities in evoked potentials. As part of an effort to further validate an animal model of the neurological disease associated with lentiviral infection, we recorded multimodal sensory evoked potentials (EPs) from nine rhesus macaques infected with passaged strains of SIVmac (R71/E17), prior to and at 1 month intervals following inoculation. The latencies of forelimb and hindlimb somatosensory evoked potentials (SEP) and flash visual evoked potentials (VEP) were measured. Within 14 weeks of inoculation, all but two animals had progressed to end-stage disease (rapid progressors). The two animals with slowly progressing disease (AQ15 and AQ94) had postinoculation life spans of 109 and 87 weeks, respectively. No significant changes were observed in evoked potentials recorded during the control period or at any time in the animals with slowly progressing disease. However, all of the monkeys with rapidly progressing disease exhibited increases in latency for at least one evoked potential type. The overall mean increases in somatosensory and visual evoked potential peak latencies for the rapid progressors were 22.4 and 25.3%, respectively. For comparison, the changes in slow progressors were not significant (1.8 and -1.9%, respectively). These results, coupled with our previous finding of slowed motor evoked potentials in the same cohort of macaques (Raymond et al.: J Neurovirol 1999;5:217-231), demonstrate a broad and somewhat variable pattern of viral injury to both sensory and motor system structures, resembling the findings in HIV-infected humans. These results coupled with our earlier work demonstrating cognitive and motor behavioral impairments in the same monkeys support the use of the SIVmac-infected rhesus macaque as a model of AIDS-related neurological disease.

Use of the Personality Assessment Inventory to assess psychopathy in offender populations

The authors investigated the validity of the Antisocial Features (ANT) scale of the Personality Assessment Inventory (PAI; L. C. Morey, 1991) with respect to assessments of psychopathy in 2 offender samples. Study 1 included 46 forensic psychiatric inpatients who were administered the Screening Version of the Hare Psychopathy Checklist (PCL:SV; S. D. Hart, D. N. Cox, & R. D. Hare, 1995). In Study 2, 55 sex offenders were administered the Hare Psychopathy Checklist--Revised (PCL-R; R. D. Hare, 1991). ANT scores correlated highly with the PCL:SV total score (r = .54) and moderately with the PCL-R total score (r = .40). ANT tapped primarily behavioral symptoms of psychopathy rather than interpersonal and affective symptoms. Also, ANT had low to moderate diagnostic efficiency regarding diagnoses of psychopathy, suggesting that it may be better used as a dimensional rather than categorical measure of this construct.

Use of the Personality Assessment Inventory to assess psychopathy in offender populations

The authors investigated the validity of the Antisocial Features (ANT) scale of the Personality Assessment Inventory (PAI; L. C. Morey, 1991) with respect to assessments of psychopathy in 2 offender samples. Study 1 included 46 forensic psychiatric inpatients who were administered the Screening Version of the Hare Psychopathy Checklist (PCL:SV; S. D. Hart, D. N. Cox, & R. D. Hare, 1995). In Study 2, 55 sex offenders were administered the Hare Psychopathy Checklist--Revised (PCL-R; R. D. Hare, 1991). ANT scores correlated highly with the PCL:SV total score (r = .54) and moderately with the PCL-R total score (r = .40). ANT tapped primarily behavioral symptoms of psychopathy rather than interpersonal and affective symptoms. Also, ANT had low to moderate diagnostic efficiency regarding diagnoses of psychopathy, suggesting that it may be better used as a dimensional rather than categorical measure of this construct.

Clinical and pathological evidence for a frontal variant of Alzheimer disease

OBJECTIVE

To evaluate the clinical and pathological features of a subgroup of patients with Alzheimer disease (AD) who exhibited early and disproportionately severe impairments on tests of frontal lobe functioning. We hypothesized that these patients would exhibit a greater degree of either neurofibrillary tangle (NFT) or senile plaque pathology in the frontal lobes than would patients with typical AD.

DESIGN AND OUTCOME MEASURES

We examined the neuropsychological profiles and senile plaque and NFT accumulation in the frontal, entorhinal, temporal, and parietal cortices in 3 patients with AD who exhibited disproportionate frontal impairments during early stages of dementia (frontal AD) and 3 matched patients with typical AD (typical AD).

RESULTS

Compared with the typical AD group, the frontal AD group performed significantly worse on 2 tests of frontal lobe functioning and on the Wechsler Adult Intelligence Scale-Revised Block Design test. No significant group differences were found on other tests. Analysis of brain tissue samples demonstrated that, despite comparable entorhinal, temporal, and parietal NFT loads, the frontal AD group showed a significantly higher NFT load in the frontal cortex than the typical AD group. Senile plaque pathology in the frontal and entorhinal cortices did not differentiate the 2 groups.

CONCLUSIONS

We identified a subgroup of patients with pathologically confirmed AD who presented in the early stages of dementia with disproportionate impairments on tests of frontal lobe functioning and had a greater-than-expected degree of NFT pathology in the frontal lobes, suggesting the existence of a frontal variant of AD that has distinctive clinical and pathological features.

Detecting symmetric patterns in EEG data: a new method of analysis

Theoretical models of higher cognitive function predict that cortical activity will exhibit families of spatial-temporal patterns of activity whose individual members are related to each other by specific symmetry transformations. In the trion model, it is suggested that these inherent symmetries play a vital role in how we think and reason. We have developed a method of analysis (SYMMETRIC analysis), which detects families of patterns in EEG data, and characterizes the symmetry relationships between members of those pattern families. Using this analysis, significant symmetry families have been found in EEG and single unit spike train data. If symmetry is a crucial aspect of brain function, it is possible that different pathologies are associated with specific types of symmetry relationships in brain activity that could be detected in EEG data by a SYMMETRIC analysis.

Calcinosis cutis associated with systemic blastomycosis in three dogs

Three dogs treated for systemic blastomycosis with intravenous amphotericin B (one case) or amphotericin B lipid complex (two cases) developed mild to severe calcinosis cutis two to six weeks after the initiation of treatment. Abnormalities in serum calcium and phosphorus during treatment for blastomycosis or at the time of diagnosis of calcinosis cutis were slight or absent. The calcification was not associated with lesions of cutaneous blastomycosis. Calcification was limited to the skin in two cases and may have also involved the kidneys in one. The calcinosis cutis resolved completely in all three dogs with no (two cases) or only palliative (one case) therapy.

Enhancement of spatial-temporal reasoning after a Mozart listening condition in Alzheimer's disease: a case study

Several recent studies have investigated the effectiveness of various behavioral interventions on the cognitive performance of subjects with Alzheimer's disease (AD). Simulations of Shaw's structured model of the cortex led to the predictions that music might enhance spatial-temporal reasoning. A subsequent behavioral study in college students documented an improvement in scores on a spatial-temporal task after listening to a Mozart piano sonata. In this study, we investigated the enhancement of scores on a spatial-temporal task after a Mozart listening condition in a set of twins who are discordant for AD. After listening to an excerpt from a Mozart piano sonata, the AD twin showed considerable improvement on the spatial-temporal task when compared with pretest scores. Furthermore, no enhancement of scores was seen following either of the control conditions (i.e., silence or 1930s popular tunes). This finding suggests that music may be used as a tool to investigate functional plasticity in Alzheimer's disease and to better understand the underlying pathophysiology.

Initiation and propagation stages of beta-amyloid are associated with distinctive apolipoprotein E, age, and gender profiles

Several recent studies have defined a relationship between apo-lipoprotein E (apoE) genotype and the risk of various neurodegenerative disorders. However, few studies have examined the influence of apoE on quantitative measures of beta-amyloid (Abeta) accumulation in a large population of autopsy cases. Using a multi-level analysis model, the interrelationships among apoE genotype, gender, age, and Abeta accumulation were investigated. In the population of these cases, there was a strong relationship between the presence of an epsilon4 allele and extent of Abeta in the frontal and entorhinal cortex. That is, when evaluating the presence or absence of significant Abeta (>1% Abeta load), subjects with one and two epsilon4 alleles were 1.9 and 3.5 times more likely to have significant Abeta accumulation than those with no epsilon4 alleles. These risks increased by a multiplicative factor of 1.014 for each year of age (at the time of death). In the subset of cases with significant Abeta (>1% Abeta load), the degree of Abeta load was best predicted by the presence of an epsilon2 allele and gender; females with no epsilon2 alleles had the highest Abeta loads (mean=12.3%), while males with one epsilon2 allele had the lowest amount of Abeta accumulation (mean=8.6%). Our results suggest that the presence of an epsilon4 allele predicts an earlier onset of Abeta deposition that is independent of gender. In contrast, once Abeta deposition has been initiated, the presence of an epsilon2 allele is associated with slower rates of accumulation, with males benefiting from the protective effect more than females.

Early generation of glia in the intermediate zone of the developing cerebral cortex

Radial glia are present at the earliest stage of cerebral cortical development, and later they transform into astrocytes. Other glial cells including astrocytes and oligodendrocytes are thought to appear only after neuron generation is complete and the cortical layers are formed. Little is known of when and where microglia enter the central nervous system and proliferate. We addressed the question of the origin of these three glial cell types in the developing ferret cerebral cortex. We assessed the temporal pattern of glial cell division by administering [3H]thymidine to label cells in S phase, and by using survival periods of 1-2 h to label dividing cells in situ. Labeled cells were identified in the developing intermediate zone of the ferret cerebral wall. These cells were present at E28, and reached a maximum number at P1. Double labeling experiments identified these cells as astrocytes, oligodendrocytes or microglia. None of the dividing cells expressed neuronal markers. These data show that all three types of glia are generated in the developing subcortical white matter, and that glial progenitors are present in the intermediate zone as soon as it becomes a recognizable structure. These data also show that the period of glial generation overlaps extensively with the period of neuron generation, since neuron generation is not complete until the end of the second postnatal week in the ferret.

A transient phase of cell death in the developing medial forebrain of the perinatal ferret

A transient bilateral population of cells immediately rostral to the ferret corpus callosum was examined at weekly intervals between embryonic day 28 and postnatal day 7. This region is tentatively identified as the medial forebrain apoptosis zone (MFAZ) because of the specific nature of cell death, and the limited area or zone in which it was observed. No other region within the brain or retina exhibited a similar pattern or amount of cell death. Only scattered apoptotic cells were found throughout the remainder of the brain-including the cerebral cortical plate, subplate, and white matter-with the exception of the ventricular zone of the lateral ventricles which contained a significant population of apoptotic cells. This study addressed three questions about apoptosis in the MFAZ: (1) does apoptotic cell death in this region signal the appearance of phagocytic macrophages, (2) does cell degeneration and phagocytosis in this region lead to the formation of an extracellular space analogous to the cavum septi pellucidi of rodents, and (3) what is the duration of degeneration, or clearance rate, of cell death in this defined region. The MFAZ was first found to contain apoptotic nuclei and macrophages late in gestation, at E34. Numbers of apoptotic nuclei and macrophages peaked one week later at birth in this area, but disappeared early in postnatal life. During this period, formation of a space rostral to the corpus callosum due to the removal of apoptotic cells was not observed. Finally, presence of apoptotic cells in the MFAZ over a period of > or = 9 days suggests a clearance rate of many hours. The close spatiotemporal correlation of the distribution of apoptotic cells and their removal by macrophages suggests that these are interrelated, and perhaps interdependent events.

Distribution of calcium-binding proteins within the parallel visual pathways of a primate (Galago crassicaudatus)

Bush babies possess three distinct parallel pathways to striate cortex (V1 or area 17). The calcium-binding proteins parvalbumin (PV) and calbindin (CB) typically show complementary regional distributions in the brain, often associated with specific aspects of functionally related groups of cells. We asked whether PV+ and CB+ immunoreactivity differentiate central visual parallel pathways in this species. Results show that PV and CB cell and neuropil staining is strongly complementary in the lateral geniculate nucleus (LGN) and is associated with separate parallel pathways. CB+ immunoreactivity is dense, but cytochrome oxidase (CO) staining is light in the paired koniocellular layers. PV+ and CO+ immunoreactivity is most dense in the parvocellular and magnocellular layers. Combined analyses of cell size, retrograde labeling, and double labeling have confirmed that all PV+ and CB+ LGN cells are geniculocortical relay cells; none was found to be gamma-aminobutyric acid (GABA)ergic. In V1, dense PV+ neuropil closely matches the expression of CO in layer 4 and in the blobs of layer 3. CB+ staining is most dense in layers 2 and 3A and is not strongly expressed within the CO interblobs. Finally, PV and CB are not found in related parallel pathway components in the LGN and V1 (e.g., in V1, CO blobs exhibit dense PV+ neuropil, yet they are targets of the small K geniculocortical relay cells that are CB+ in the LGN). Our findings support the view that three functionally distinct visual pathways project to V1 from the LGN. However, the differences in the patterns of localization of PV and CB in the LGN and in V1 suggest that these proteins may be utilized in different ways in these two visual areas.

Neuropeptide Y receptor distribution and regulation in the suprachiasmatic nucleus of the Syrian hamster (Mesocricetus auratus)

The suprachiasmatic nucleus (SCN) receives a direct photic projection from the retina, the retinohypothalamic tract (RHT), and an indirect photic projection from the intergeniculate leaflet of the thalamus, the geniculohypothalamic tract (GHT). The primary neurochemical signal in the GHT appears to be neuropeptide Y (NPY), and several lines of evidence indicate that NPY may be involved in determining the response of the SCN to light. The purpose of the present study was (i) to localize NPY binding sites in the hamster SCN and to compare the distribution of these binding sites with the terminal field of the RHT and (ii) to determine if SCN levels of NPY binding change during the day. RHT fibers, defined using the carbocyanine dye DiI, were localized primarily within the ventrolateral region of the SCN. The distribution of NPY receptors, as visualized by 125I-peptide YY (PYY) binding, overlapped the projection field of the RHT. Specific binding of 125I-PYY was significantly greater in the ventrolateral SCN than in the medial SCN. To determine whether NPY binding changes during the day, the levels of 125I-PYY in the SCN were determined 4 h before the onset of darkness, 1 h before the onset of darkness and 2 h after the onset of darkness in hamsters housed in a 14:10 light-dark cycle. The levels of binding at 4 and 1 h before dark onset were significantly lower than 2 h after the onset of darkness. In contrast, no significant differences were observed in 125I-PYY binding over these same sampling intervals in either the medial preoptic area or the lateral hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

Computed tomography detection of a cerebral calcific embolus following coronary catheterization

A 77-year-old man underwent coronary artery angiography quite well. However, several attempts were required to pass the pigtail catheter across a calcified stenotic aortic valve. On return to the floor, motor aphasia and right hemiparesis developed and improved steadily within a few days. Computed tomography (CT) of the head revealed a calcific density in the left middle cerebral artery. The authors believe the calcific plaque originated from the calcified aorta and aortic valve. The patient was discharged within 48 hours with minimal neurological signs. Spontaneous calcified emboli to cranial vessels from calcific aortic stenosis or other sources are rare. CT detection of a calcific plaque in a cranial vessel following coronary vessel catheterization is well documented in this patient.

Molecular basis of the medium-chain fatty acyl-CoA dehydrogenase-catalyzed "oxidase" reaction: pH-dependent distribution of intermediary enzyme species during catalysis

In a previous paper, we demonstrated that the medium-chain fatty acyl-CoA dehydrogenase-catalyzed (MCAD-catalyzed) reductive half-reaction of indolepropionyl-CoA proceeds via formation of a chromophoric intermediary species "X" (absorption maximum = 400 nm) and proposed that the decay of this species might limit the overall rate of the "oxidase" reaction [Johnson, J. K., & Srivastava, D. K. (1993) Biochemistry 32, 8004-8013]. During this latter reaction, the buffer-dissolved O2 served as an electron acceptor [Johnson, J. K., Wang, Z. X., & Srivastava, D. K. (1992) Biochemistry 31, 10564-10575]. To ascertain whether the intrinsic stability of X influences the oxidase activity, we undertook a detailed kinetic investigation of this enzyme at different pH values. The time-resolved spectra for the reductive half-reaction (obtained via the rapid-scanning stopped-flow method) at different pH values reveal that the amplitude of the intermediary (X) spectral band is more pronounced at a lower pH (pH 6.4) than at a higher pH (pH 9.0). Single-wavelength transient kinetic data for the reductive half-reaction (in both the forward and the reverse direction) at all pH values are consistent with fast (1/tau 1) and slow (1/tau 2) relaxation rate constants. Of these, whereas the fast relaxation rate constant for the reaction in the forward direction (1/tau 1f) decreases with an increase in pH, the corresponding slow relaxation rate constant (1/tau 2f) increases with an increase in pH. The pH-dependent steady-state kinetic data reveal that, like 1/tau 2f, kcat for the MCAD-catalyzed oxidase reaction increases with an increase in the pH of the buffer media.(ABSTRACT TRUNCATED AT 250 WORDS)

Peptides associated with monensin resistance in sporozoites of Eimeria tenella (Coccidia)

Resistance to monensin in the sporozoites of a laboratory strain (WIS) of Eimeria tenella was amplified by treating free sporozoites with increased monensin levels in vitro, followed by propagation of these treated sporozoites in chickens. The parent strain of WIS and its subsequent lines developed from the treatment of monensin at 1, 5, or 25 micrograms/ml were designated as WIS(0), WIS(1), WIS(5), or WIS(25), respectively. The penetration rate of sporozoites into primary chicken kidney cell cultures showed that the sensitivity of sporozoites to the treatment of monensin at 1 and 5 micrograms/ml was significantly reduced in the WIS(25) line in comparison with the WIS(0) line. When native polyacrylamide gel electrophoresis (PAGE) was conducted, a change in the relative mobility of a protein band was found in the protein samples of these coccidial lines. Sodium dodecyl sulfate PAGE revealed that 2 peptides with molecular weights of approximately 50.0 and 31.4 kDa were present in the sporozoites of resistant lines but undetectable in their WIS-parent sporozoites. Derivation of the resistant lines from a drug-sensitive parent line gave strong support to a link between the appearance of the peptides and resistance to ionophores in this strain of E. tenella.