Cardiovascular effects of odors

Several occupational and residential settings can expose both normal and sensitive human subjects to odors and irritants. These settings include intensive agricultural operations housing swine and poultry, cigarette-smoke-filled bars, landfills and manufacturing processes. The literature suggests that adverse sensory reactions to strong odors and irritants may lead to the release of catecholamines and stress hormones. Physiological and biochemical measurements related to cardiovascular risk, e.g., blood pressure, heart rate, high-density lipoprotein (HDL) cholesterol level and serum triglyceride level, may be altered as a result of exposure to odor and irritant-induced release of catecholamines. Further work in the form of field studies and chamber exposure protocols is required to determine whether the physiological and biochemical changes observed to date represent an increase in cardiovascular risk, or are reversible changes within the normal homeostatic range.

6-Methoxy-7-methyl-8-oxoguanine, an unusual purine from the ascidian Symplegma rubra

A new purine derivative, 6-methoxy-7-methyl-8-oxoguanine (1), along with 8-oxoadenine (2) and the human metabolite 3-methylxanthine (3), has been isolated from the ascidian Symplegma rubra collected on the southeastern coastline of Brazil. The structures of the three purines were established by analysis of spectroscopic data.

Transposition genes of the Bacteroides mobilizable transposon Tn4555: role of a novel targeting gene

Conjugative transposons have been identified in several bacterial species, most notably the Gram-positive Enterococci and the Gram-negative Bacteroides. In Bacteroides species, these elements encode a complete conjugative machinery, which mediates their own intercellular transfer, and they can mobilize in trans co-resident elements. One such mobilizable element is the antibiotic resistance transposon, Tn4555, which was previously found to integrate into a specific genome target site via a site-specific recombination mechanism. In this work, we demonstrate that three Tn4555 genes were involved in integration of the element. These were int encoding a lambda-type integrase, which was absolutely required for integration of the transposon, and two accessory genes, which increased the frequency of integration. Interestingly, one of these accessory gene products, TnpA, directed the insertion of Tn4555 into the genome target site; in the absence of tnpA, the insertion pattern was essentially random. This is the first example of a site-specific recombinase that uses a specific targeting protein.

Role of the alkyl hydroperoxide reductase (ahpCF) gene in oxidative stress defense of the obligate Anaerobe bacteroides fragilis

In this study we report the identification and role of the alkyl hydroperoxide reductase (ahp) gene in Bacteroides fragilis. The two components of ahp, ahpC, and ahpF, are organized in an operon, and the deduced amino acid sequences revealed that B. fragilis AhpCF shares approximately 60% identity to orthologues in other gram-positive and gram-negative bacteria. Northern blot hybridization analysis of total RNA showed that the ahpCF genes were transcribed as a polycistronic 2.4-kb mRNA and that ahpC also was present as a 0.6-kb monocistronic mRNA. ahpC and ahpCF mRNAs were induced approximately 60-fold following H(2)O(2) treatment or oxygen exposure of the parent strain but were constitutive in a peroxide-resistant strain. Further investigation using an ahpCF'::beta-xylosidase gene transcriptional fusion confirmed that ahpCF had lost normal regulation in the peroxide-resistant strain compared to the parent. The ahpCF mutant was more sensitive to growth inhibition and mutagenesis by organic peroxides than the parent strain, as determined by disk inhibition assays and the frequency of mutation to fusidic acid resistance. This finding suggests that the ahp genes play an important role in peroxide resistance in B. fragilis. Under anaerobic conditions, we observed increases in the number of spontaneous fusidic acid-resistant mutants of five- and sevenfold in ahpCF and ahpF strain backgrounds, respectively, and eightfold in the ahpCF katB double mutant strain compared to the parent and katB strains. In addition, ahpCF, ahpF, and ahpCF katB mutants were slightly more sensitive to oxygen exposure than the parent strain. Moreover, the isolation of a strain with enhanced aerotolerance and high-level resistance to alkyl hydroperoxides from an ahpCF katB parent suggests that the physiological responses to peroxide toxicity and to the toxic effects of molecular oxygen are overlapping and complex in this obligate anaerobe.

Clathrin: anatomy of a coat protein

Clathrin is a vesicle coat protein involved in the assembly of membrane and cargo into transport vesicles at the plasma membrane and on certain intracellular organelles. Recently, crystal structures of two separate parts of the clathrin heavy chain, a fragment of the proximal leg and the N-terminal domain, have been analysed, providing the first high-resolution data for a vesicle coat protein. Viewing these structures in the context of a hexagonal barrel coat, recently determined to 21 A by cryo-electron microscopy, provides new insights into the assembly of clathrin coats.

GnRH action on luteal steroidogenesis during pregnancy

The results of our study presented here establishes that gonadotropin-releasing hormone (GnRH) acts directly on the corpus luteum, leading to suppressed production and release of progesterone and thus disrupting pregnancy. A GnRH-agonist (GnRH-Ag) treatment suppressed the luteal and serum progesterone levels. This suppression is neither mediated by a fall in ovarian testosterone production nor its conversion to estradiol. Although the treatment suppressed the nuclear estradiol-receptor content and binding sites for LH in the corpus luteum, it had no effect on the luteal binding sites for GnRH and prolactin within 24 h. GnRH-Ag augmented the plasma levels of luteinizing hormone, decreased the magnitude of nocturnal surges of prolactin, and had no effect on luteal cyclic adenosine 5'-monotriphosphate levels. Yet, the treatment had no effect on the luteal content of free cholesterol. We have also demonstrated, for the first time, the presence of steroidogenic acute regulatory protein and peripheral benzodiazepine receptor in the rat corpus luteum, and the suppression of these proteins by GnRH-Ag leads to reduced steroidogenesis by the corpus luteum. Concomitantly, P450 side-chain cleavage enzyme, its activity, and its mRNA content and 3beta-hydroxy-steroid dehydrogenase content in the corpus luteum decreased. The treatment suppressed the plasma levels of pregnenolone and 20alpha-dihydroprogesterone. These data suggest that the suppression of luteal steroidogenesis by GnRH-Ag may be due to its inhibitory effect on the cholesterol transport and/or on the enzymes involved in the steroidogenic pathway. Furthermore, based on other observations made in our laboratory, we propose a hypothesis that an endogenous GnRH is present in the corpus luteum/ovary during pregnancy in the rat and that this GnRH may play a physiological role in the regulation, maintenance, and/or termination of pregnancy.

Genetic epidemiological study of maternal and paternal transmission of Alzheimer's disease

Recent evidence for mitochondrial mutations associated with Alzheimers disease (AD) suggests the possibility of maternal transmission of this illness. We investigated this hypothesis by examining, in a variety of ways, the risk of a primary progressive dementia (PPD) in the parents (n = 650) and siblings (n = 1,220) of 325 AD probands. The results did not support maternal transmission in AD: The mothers of AD probands were not at greater risk of PPD than the fathers or the sisters of AD probands; the offspring of affected mothers were not at greater risk than the offspring of affected fathers or families with no affected parent; and, after selecting those proband families with evidence for increased familial loading, such families did not more frequently have affected mothers than fathers. In contrast, the cumulative risk of PPD in fathers of AD probands, while similar to that of mothers, was significantly increased over the brothers of AD probands. In addition, the cumulative risk curve of PPD in the offspring of affected fathers was significantly higher than the offspring of no affected parents. While no evidence for maternal transmission in AD was observed, unexpectedly, we did find evidence of increased paternal transmission.

Enhanced release of prostaglandins contributes to flow-induced arteriolar dilation in eNOS knockout mice

Nitric oxide and prostaglandins were shown to contribute to the endothelial mediation of flow-induced dilation of skeletal muscle arterioles of rats. Thus, we hypothesized that flow-induced dilation and its mediation are altered in gracilis muscle arterioles of mice deficient in the gene for endothelial nitric oxide synthase (eNOS-KO) compared with control wild-type (WT) mice. Gracilis muscle arterioles ( approximately 80 micrometer) of male mice were isolated, then cannulated and pressurized in a vessel chamber. The increases in diameter elicited by increases in perfusate flow from 0 to 10 microq/min were similar in arterioles from eNOS-KO (n=28) and WT (n=22) mice ( approximately 20 micrometer at 10 microL/min flow). Removal of the endothelium eliminated flow-induced dilations in vessels of both strains of mice. N(omega)-nitro-L-arginine (L-NNA, 10(-4) mol/L) significantly inhibited flow-induced dilation in arterioles of WT mice by approximately 51% but had no effect on responses of arterioles from eNOS-KO mice. Indomethacin (INDO, 10(-5) mol/L) inhibited flow-induced dilation of WT mice by approximately 49%, whereas it completely abolished this response in arterioles of eNOS-KO mice. Simultaneous administration of INDO and L-NNA eliminated flow-induced responses in arterioles of WT mice. Dilations to carbaprostacyclin were similar at concentrations of 10(-8) and 3x10(-8) mol/L but decreased significantly at 10(-7) mol/L in arterioles of eNOS-KO compared with those of WT mice. These findings demonstrate that, despite the lack of nitric oxide mediation, flow-induced dilation is close to normal in arterioles of eNOS-KO mice because of an enhanced release of endothelial dilator prostaglandins and suggest that this vascular adaptation may contribute to the regulation of peripheral resistance in eNOS-KO mice.

Genetic structure and transcriptional analysis of a mobilizable, antibiotic resistance transposon from Bacteroides

Tn4555 is a 12.1-kb Bacteroides antibiotic resistance transposon representative of a novel class of transmissible genetic elements that can be transferred by resident conjugative tetracycline resistance transposons (Tc(r)-elements) but are not capable of self-transfer. Previously it was shown that Tn4555 transposes by a site-specific recombination mechanism that utilizes a circular intermediate. This circular form is induced by tetracycline and it also is the substrate for conjugation. To better understand the mechanism of transposition, the entire nucleotide sequence of Tn4555 was determined and a set of genes potentially involved in transposition was identified. The transposon was 12,105 bp including a variable 6-bp coupling sequence associated with one of the transposon termini. The element had a 44.3% G + C composition and nine potential protein coding regions were observed, eight of which were encoded on the forward strand. Two putative transposition genes were found. The int gene product had significant C-terminal homology to the lambda family of integrases and the xis gene product was similar to several excisionase proteins encoded by both plasmids and conjugative transposons. The mobA mobilization gene and cfxA beta-lactamase gene of Tn4555 had been previously identified, and the remaining five open reading frames had no significant matches with sequences in the available databases. Northern hybridization analysis revealed that all Tn4555 genes except for orf-9 were expressed and two sets of genes, tnpA, int and xis, orf-5, orf-6 were organized in operons. None of the genes seemed to be induced significantly by the addition of tetracycline to cultures. Although a small 0.4-kb xis-specific transcript appeared in tetracycline-treated cultures it was not clear if this was due to an induction or if it was a specific degradation product.

Reduced coronary NO production in conscious dogs after the development of alloxan-induced diabetes

The role of nitric oxide (NO) in the control of coronary blood flow (CBF) during the development of diabetes is unknown. To study this, mongrel dogs were chronically instrumented using sterile techniques for measurements of systemic hemodynamics and CBF. With heart rate controlled (150 beats/min), veratrine (1-10 micrograms/kg) caused dose-dependent increases in CBF; e.g., 5 mirograms/kg of veratrine increased CBF by 57 +/- 7% from 41 +/- 1.3 ml/min (P < 0.05). The dogs developed diabetes 4-5 wk after injection of alloxan (40-60 mg/kg iv, blood glucose levels were 384 +/- 18 mg/dl). After diabetes the same doses of veratrine caused smaller increases in CBF; i.e., 5 micrograms/kg of veratrine increased CBF by 32 +/- 2% (P < 0.05 compared with control) from 28 +/- 4 ml/min. ACh- and adenosine-induced coronary vasodilation were reduced after diabetes as well. In anesthetized dogs after diabetes, vagal stimulation caused smaller increases in CBF. ACh and bradykinin caused smaller increases in NO(-)(2) production in coronary microvessels from diabetic dogs. Furthermore, despite the fact that mRNA for endothelial cell NO synthase from the aorta was increased twofold with the use of Northern blotting, the protein for aortic endothelial constitutive NO synthase was reduced by 66% after diabetes, as determined by Western blotting. Our results indicate that the NO-dependent coronary vasodilation by the Bezold-Jarisch reflex is impaired in conscious dogs after diabetes. The mechanism responsible for the impaired endothelium-dependent coronary vasodilation is most likely the decreased release of NO from the endothelium.

Functional organization of clathrin in coats: combining electron cryomicroscopy and X-ray crystallography

The sorting of specific proteins into clathrin-coated pits and the mechanics of membrane invagination are determined by assembly of the clathrin lattice. Recent structures of a six-fold barrel clathrin coat at 21 A resolution by electron cryomicroscopy and of the clathrin terminal domain and linker at 2.6 A by X-ray crystallography together show how domains of clathrin interact and orient within the coat and reveal the strongly puckered shape and conformational variability of individual triskelions. The beta propeller of the terminal domain faces the membrane so that recognition segments from adaptor proteins can extend along its lateral grooves. Clathrin legs adapt to different coat environments in the barrel by flexing along a segment at the knee that is free of contacts with other molecules.

Genetic antecedents of dopamine dysfunction in schizophrenia

BACKGROUND

Relatives of schizophrenic probands frequently manifest attenuated features of this illness including the negative symptoms and the milder positive psychotic symptoms. These two symptom dimensions are hypothesized to be associated with decreased and increased brain dopamine (DA) functions, respectively, raising the possibility that DA abnormalities may be present in the relatives of schizophrenic probands.

METHODS

Plasma homovanillic acid (HVA), the major DA metabolite and an indicator of brain DA activity, was measured in nonpsychotic, physically healthy first-degree relatives (n = 55) of schizophrenic probands and in normal subjects (n = 20) without a family history of schizophrenia.

RESULTS

Plasma HVA inversely correlated with negative symptoms and positively correlated with attenuated positive symptoms. Also, relatives had decreased plasma HVA compared to normal subjects, consistent with the fact that these relatives are characterized by negative symptoms. These findings were not related to major peripheral factors that could affect plasma HVA suggesting that the findings may reflect changes in brain DA activity.

CONCLUSIONS

Negative symptoms indicating a genetic diathesis to schizophrenia in relatives may have a biologic basis in reduced DA activity and the DA dysfunction of schizophrenia may have genetic antecedents. This opens an important new avenue for further study of DA in this illness.

Endogenous endothelial nitric oxide synthase-derived nitric oxide is a physiological regulator of myocardial oxygen consumption

Our objective was to determine the precise role of endothelial nitric oxide synthase (eNOS) as a modulator of cardiac O2 consumption and to further examine the role of nitric oxide (NO) in the control of mitochondrial respiration. Left ventricle O2 consumption in mice with defects in the expression of eNOS [eNOS (-/-)] and inducible NOS [iNOS (-/-)] was measured with a Clark-type O2 electrode. The rate of decreases in O2 concentration was expressed as a percentage of the baseline. Baseline O2 consumption was not significantly different between groups of mice. Bradykinin (10(-4) mol/L) induced significant decreases in O2 consumption in tissues taken from iNOS (-/-) (-28+/-4%), wild-type eNOS (+/+) (-22+/-4%), and heterozygous eNOS(+/-) (-22+/-5%) but not homozygous eNOS (-/-) (-3+/-4%) mice. Responses to bradykinin in iNOS (-/-) and both wild-type and heterozygous eNOS mice were attenuated after NOS blockade with N-nitro-L-arginine methyl ester (L-NAME) (-2+/-5%, -3+/-2%, and -6+/-5%, respectively, P<0.05). In contrast, S-nitroso-N-acetyl-penicillamine (SNAP, 10(-4) mol/L), which releases NO spontaneously, induced decreases in myocardial O2 consumption in all groups of mice, and such responses were not affected by L-NAME. In addition, pretreatment with bacterial endotoxin elicited a reduction in basal O2 consumption in tissues taken from normal but not iNOS (-/-)-deficient mice. Our results indicate that the pivotal role of eNOS in the control of myocardial O2 consumption and modulation of mitochondrial respiration by NO may have an important role in pathological conditions such as endotoxemia in which the production of NO is altered.

Mutant yields and mutational spectra of the heterocyclic amines MeIQ and PhIP at the S1 locus of human-hamster AL cells with activation by chick embryo liver (CELC) co-cultures

Cooking meat and fish at high temperature creates heterocyclic amines (HA) including 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Several HA are mutagens in the Ames' S9/Salmonella assay. While PhIP is a substantial Ames' test mutagen, it is 1000-fold less active than the extraordinarily potent MeIQ. In contrast, MeIQ is significantly less mutagenic than PhIP in several mammalian cell assays, especially in repair-deficient Chinese hamster ovary (CHO) cells. HA are suspect human carcinogens on the basis of (i) epidemiological evidence, (ii) induction of tumors in rodents and monkeys, (iii) DNA adduct formation and (iv) mutagenic capacity. In this study, MeIQ and PhIP were significant mutagens at the S1 locus of co-cultivated human/hamster hybrid AL cells following metabolic activation by beta-napthoflavone (betaNF)-induced chick embryonic liver cultures (CELC). MeIQ was more mutagenic than PhIP in the CELC+AL cell assay. The mutant response curves increase with dose and then plateau (PhIP), or decrease (MeIQ). The inflections in these response curves coincide with dose-dependent decreases in cytochrome CYP1A1 activity. Molecular analysis of S1- mutants indicates that a substantial fraction, >65%, of the mutations induced by PhIP are deletions of 4.2 to 133 (Mbp); half are larger than 21 Mbp. Mutations induced by MeIQ were smaller, most (56%) being less than 5.7 Mbp. When appropriate metabolic activation is combined with a target locus, which can detect both small and large chromosomal mutations, both MeIQ and PhIP are significant mutagens and clastogens in repair proficient mammalian cells.

Identifying families with likely genetic protective factors against Alzheimer disease

Elderly individuals who lived beyond the age of 90 years without dementia were hypothesized to have increased concentrations of genetic protective factors against Alzheimer disease (AD), conferring a reduced liability for this disease relative to less-aged nondemented elderly. However, testing this hypothesis is complicated by having to distinguish such a group from those who may lack genetic risk factors for AD, have had protective environmental exposures, or have escaped dementia for other reasons. Probands carrying genetic protective factors, however, should have relatives with lower illness rates not only for earlier-onset disease, when genetic risk factors are a strong contributing factor to the incidence of AD, but also for later-onset disease, when the role of these factors appears to be markedly diminished. AD dementia was assessed through family informants in 6,660 first-degree relatives of 1,049 nondemented probands aged 60-102 years. The probands were grouped by age (60-74, 75-89, and 90-102 years), and the cumulative survival from AD and 10-year-age-interval hazard rates of AD were calculated in their first-degree relatives. Cumulative survival from AD was significantly greater in the relatives of the oldest proband group (aged 90-102 years) than it was in the two younger groups. In addition, the reduction in the rate of illness for this group was relatively constant across the entire late life span. The results suggest that genetic factors conferring a lifelong reduced liability of AD may be more highly concentrated among nondemented probands aged >/=90 years and their relatives. Efforts to identify protective allele-bearing genes that are associated with very late-onset AD should target the families of nonagenarians and centenarians.

Outcome of primary radiocephalic fistula for haemodialysis

BACKGROUND

Patient characteristics may help select the most appropriate type of permanent vascular access for haemodialysis. The aim of this study was to assess the influence of patient-related variables on the outcome of radiocephalic fistulas.

METHODS

Over 3 years 107 consecutive patients underwent formation of a radiocephalic fistula for permanent haemodialysis access. Patients receiving prosthetic, ulnar, brachial or secondary fistulas were excluded. Patients were followed prospectively until access failure, transplantation or death, or for a minimum of 6 months (median follow-up 24 months).

RESULTS

Primary patency was 69 per cent at 12 months and 56 per cent at 24 months. Endovascular and surgical intervention led to limited improvement in secondary patency to 63 per cent at 24 months. Regression analysis showed that fistula failure was more common in women (P = 0.02), diabetics (P = 0.03) and young patients (P = 0.02). By life-table analysis, primary and secondary patency were significantly better (P = 0.01) for men and non-diabetics, while the outcome was similar for all age groups.

CONCLUSION

One-third of radiocephalic fistulas fail irreversibly within 2 years. Failure is more likely in women and diabetic patients.

The necessary role of the autopsy in cardiovascular epidemiology

The autopsy rate in the United States today is remarkably low, with proportionally fewer autopsies for natural causes of death. Consequently, most cardiovascular epidemiology studies do not use autopsy data and rely on death certificates, medical records, questionnaires, and family interviews as sources of mortality information. These practices introduce a high degree of variability and uncertainty regarding cause of death. This review illustrates the necessity for increased use of autopsies in cardiovascular epidemiology by critically evaluating other measures of cardiovascular disease (CVD) incidence. We evaluated the literature regarding CVD as cause of death and conducted discussions with cardiologists, pathologists, and epidemiologists. No attempt was made for meta-analysis. This review shows the limited reliability of death certificates, medical records, and interviews as sources of mortality statistics. In addition, the autopsy's role in clearly indicating the presence of CVD is illustrated. The autopsy used in conjunction with medical records is the only reliable means for establishing cause of death from CVD. There is an urgent need to reassess the current dependence of statistical mortality data on death certificates and other inadequate sources of CVD incidence. Death certificates, in general, are inadequately monitored for quality control and appropriate administrative oversight. With an increase in the number of hospitals performing no autopsies to investigate cause of death, a uniform national autopsy database is needed.

Characterization of a peroxide-resistant mutant of the anaerobic Bacterium bacteroides fragilis

A Bacteroides fragilis mutant resistant to hydrogen peroxide and alkyl peroxide was isolated by enrichment in increasing concentrations of hydrogen peroxide. The mutant strain was constitutively resistant to 100 mM H2O2 and 5 mM cumene hydroperoxide (15-min exposure). In contrast, the parent strain was protected against <10 mM H2O2 when the peroxide response was induced with a sublethal concentration of H2O2, and no protection was observed in untreated cells. In addition, catalase activity in the mutant strain was not repressed in anaerobic cultures as reported previously for the parent strain. Comparison of the protein profile of crude extracts of the B. fragilis strains revealed that at least three oxidative stress-induced proteins in the parent strain were constitutively expressed in the mutant as detected by nondenaturing polyacrylamide gel electrophoresis. N-terminal amino acid sequence of these overexpressed proteins confirmed the presence of a deregulated catalase (KatB), an alkyl hydroperoxidase reductase subunit C (AhpC), and a Dps/PexB homologue. Northern blot analysis and katB::cat transcriptional fusion studies revealed that in the mutant, katB was deregulated compared to the parent and that katB was controlled by a trans-acting regulatory mechanism. Moreover, constitutive expression of KatB and of the AhpC and Dps homologues in the H2O2-resistant mutant suggests that these proteins may share a common oxidative stress transcriptional regulator and may be involved in B. fragilis peroxide resistance.

Pharmacological analysis of cyclooxygenase-1 in inflammation

The enzymes cyclooxygenase-1 and cyclooxygenase-2 (COX-1 and COX-2) catalyze the conversion of arachidonic acid to prostaglandin (PG) H2, the precursor of PGs and thromboxane. These lipid mediators play important roles in inflammation and pain and in normal physiological functions. While there are abundant data indicating that the inducible isoform, COX-2, is important in inflammation and pain, the constitutively expressed isoform, COX-1, has also been suggested to play a role in inflammatory processes. To address the latter question pharmacologically, we used a highly selective COX-1 inhibitor, SC-560 (COX-1 IC50 = 0.009 microM; COX-2 IC50 = 6.3 microM). SC-560 inhibited COX-1-derived platelet thromboxane B2, gastric PGE2, and dermal PGE2 production, indicating that it was orally active, but did not inhibit COX-2-derived PGs in the lipopolysaccharide-induced rat air pouch. Therapeutic or prophylactic administration of SC-560 in the rat carrageenan footpad model did not affect acute inflammation or hyperalgesia at doses that markedly inhibited in vivo COX-1 activity. By contrast, celecoxib, a selective COX-2 inhibitor, was anti-inflammatory and analgesic in this model. Paradoxically, both SC-560 and celecoxib reduced paw PGs to equivalent levels. Increased levels of PGs were found in the cerebrospinal fluid after carrageenan injection and were markedly reduced by celecoxib, but were not affected by SC-560. These results suggest that, in addition to the role of peripherally produced PGs, there is a critical, centrally mediated neurological component to inflammatory pain that is mediated at least in part by COX-2.

Clathrin coats at 21 A resolution: a cellular assembly designed to recycle multiple membrane receptors

We present a map at 21 A resolution of clathrin assembled into cages with the endocytic adaptor complex, AP-2. The map was obtained by cryo-electron microscopy and single-particle reconstruction. It reveals details of the packing of entire clathrin molecules as they interact to form a cage with two nested polyhedral layers. The proximal domains of each triskelion leg depart from a cage vertex in a skewed orientation, forming a slightly twisted bundle with three other leg domains. Thus, each triskelion contributes to two connecting edges of the polyhedral cage. The clathrin heavy chains continue inwards under the vertices with local 3-fold symmetry, the terminal domains contributing to 'hook-like' features which form an intermediate network making possible contacts with the surface presented by the inner adaptor shell. A node of density projecting inwards from the vertex may correspond to the C-termini of clathrin heavy chains which form a protrusion on free triskelions at the vertex. The inter-subunit interactions visible in this map provide a structural basis for considering the assembly of clathrin coats on a membrane and show the contacts which will need to be disrupted during disassembly.

Response of effluent-irrigated Eucalyptus grandis and Pinus radiata to salinity and vapor pressure deficits

Effects of high vapor pressure deficit (VPD) and soil salinity on growth and physiology of Pinus radiata D. Don and Eucalyptus grandis Hill ex Maiden were studied in a five-year-old plantation irrigated with salt-enhanced effluent (2.2 dS m(-1)) or freshwater (0.2 dS m(-1)) for 14 weeks during spring and summer. Salt was then rapidly leached by over-irrigation with low-salinity effluent. Soil water and salinity, tree water stress, sap flux, substrate carbon conversion efficiency, foliage and stem growth, and foliar cations and chloride were monitored throughout the study. An average of 9 and 1 Mg ha(-1) of salt with an average hydraulic load of 660 and 780 mm was applied to the salt and control plots, respectively. Maximum soil salinity in the root zone was 5.8 and 6.8 dS m(-1) in the eucalypt and pine plots, respectively. Predawn water potential was more than twice as sensitive to increasing salinity in E. grandis as in P. radiata. The salt treatment reduced rates of leaf and stem growth of the eucalypts by 60 to 70% but had no effect on leaf and stem growth of the pines. In the eucalypts, salinity decreased mean leaf area by 26% and increased specific leaf area by 12% compared with control values, indicating less biomass per unit leaf area in the salt treatment. Salinity had no effects on these two parameters in pine. The salt treatment significantly increased mean foliar concentrations of Na and Cl in both species, and of K in the pines. Foliar Na concentration was 6-10 times higher in the eucalypts than in the pines. Lowered water potential and increased Na concentration in the eucalypts in response to salinity resulted in about a 50% reduction in the efficiency of conversion of carbon into biomass; however, three weeks after leaching the salt, there was no significant difference in efficiency of conversion of carbon into biomass between the treatments. Salinity had no effect on water use by eucalypts, but caused a nonsignificant decrease (7%) in water use by pines. As evaporative demand increased, crop factor (transpiration divided by pan evaporation) declined by up to 50 and 60% in the pines and eucalypts, respectively. We conclude that stomatal response to high VPD, not soil salinity, accounts for most of the reduction in summertime water use.

Downregulation of right ventricular phosphodiesterase PDE-3A mRNA and protein before the development of canine heart failure

Phosphodiesterase III (PDE-3) inhibitors are inotropes used to treat congestive heart failure (HF). Previous studies showed PDE-3A mRNA levels were reduced in the left ventricle (LV) in dogs subjected to pacing-induced HF. The present study evaluated a time-course for RV-specific changes in PDE-3A mRNAs and proteins after pacing for 3 wk (n = 4) or in HF (4-5 wk; n = 4-6). Total RNA from LV/RV tissues was isolated for Northern analyses; cytosolic and microsomal proteins were prepared for PDE-3A immunoblots. PDE-3A mRNAs (7-8 and 10 kb) were normalized against glyceraldehyde-3-phosphodehydrogenase (GAPDH) or ribosomal 18s with similar results. PDE-3A/GAPDH ratios in 3 wk were unchanged in LV, but significantly (p < 0.05) reduced by 48% in RV vs unpaced controls (n = 8). In contrast, PDE-3A (7-8 kb)/GAPDH ratios were significantly reduced in HF by 50-59% in both ventricles. Consistent with mRNA levels, significant reductions in microsomal 135 kDa (93-96%) and cytosolic 120 kDa PDE-3A (57-69%) were seen in both ventricles in HF or in the RV at 3 wk; an LV-specific reduction (50%) in cytosolic 80 kDa PDE-3A in HF was also detected. In summary, RV-specific downregulation of PDE-3A mRNA/protein(s) at 3 wk suggests that hemodynamic rather than humoral mechanisms are responsible, and provides a molecular basis for the limited efficacy of milrinone in the progression of HF.

Modernization and health care in contemporary China

This paper provides an analysis of the changes that have occurred in the Chinese health care system in the reform era, post-1978. The economic reforms have brought significant benefits to many Chinese people, but the benefits have not been distributed evenly throughout Chinese society. The paper evaluates some of the evidence indicating deterioration in both the quality and quantity of health care services in the reform era. There is some alarming evidence that rural women, especially those living in the country's poorest regions, have been experiencing lower levels of accessibility to health care, and increasing levels of both morbidity and mortality. It is also evident that during the reform era the gap between service levels in rural areas and the cities has widened, and that chronic poverty still exists in large parts of the countryside. It is important to stress that these inequalities were not created by the economic reforms--in fact they were first observed during the supposedly egalitarian era associated with Mao Zedong. The economic reforms and the widespread implementation of market socialism in Chinese society, have, in general, been associated with improved health status and greater access to health care. It is also apparent, however, that pre-existing inequalities have not been eradicated by the reforms, and, particularly along the lines of gender and geography, the evidence points to a widening of inequality.

Separation of polycyclic aromatic hydrocarbon metabolites by gamma-cyclodextrin-modified micellar electrokinetic chromatography with laser-induced fluorescence detection

Using a modified micellar buffer consisting of gamma-cyclodextrin (gamma-CD) and sodium dodecyl sulfate (SDS), we have obtained separations of hydroxy-polycyclic aromatic hydrocarbons (hydroxyPAHs). These compounds are oxidative products of mammalian PAH metabolism. The analytes were detected with a commercial laser-induced fluorescence (LIF) detector. A number of hydroxyPAH isomers could be separated by changes in gamma-CD concentration. Baseline resolution of 12 hydroxyPAHs was obtained using 30 mM borate, 60 mM SDS and 40 mM gamma-CD. The particular site substitution of the hydroxy group can produce changes in the hydroxyPAH fluorescence spectrum, and the effect of optical filter selection was studied for the LIF detection. The mass detection limits were in the (0.08-0.5) x 10(-15) mol range. To our knowledge, this is the first report of the separation of metabolic products of PAHs (and several positional isomers) using gamma-CD and micellar electrokinetic chromatography.

Dietary calcium and blood pressure in a Native American population

OBJECTIVE

To assess the relationship between dietary calcium and blood pressure.

METHODS

Cross-sectional study of 404 adult Pima Indians of Arizona. Dietary variables were assessed by the 24-hour recall. Hypertension (HTN) was defined as systolic blood pressure (SBP) > or = mmHg or diastolic blood pressure (DBP) > or = 90 mmHg or drug treatment.

RESULTS

Controlled for age and sex, dietary calcium intake was higher in subjects with HTN than in those without (p < 0.01), and higher dietary calcium was associated with a higher prevalence of HTN (odds ratio comparing highest with lowest tertile group of calcium = 2.6, 95% CI 1.4-4.8). Age-sex-adjusted men DBP in low, middle and high tertiles of calcium was 74, 76, and 79 mmHg, respectively (p < 0.001). SBP was not significantly different in the three tertiles (p = 0.07). Multiple regression analyses that controlled for age, sex, body mass index, sodium, potassium and alcohol also suggested a positive association between DBP and dietary calcium (p < 0.01), an association which was stronger at higher glucose concentrations (p < 0.01 for the calcium-glucose interaction).

CONCLUSION

In Pima Indians, a population with a high incidence of diabetes, the inverse association between dietary calcium and blood pressure reported in other populations was not found.

Lateral ventricular enlargement in schizophrenic probands and their siblings with schizophrenia-related disorders

BACKGROUND

To investigate possible genetic determinants of ventricular enlargement in schizophrenia, we compared lateral ventricle/brain ratios (VBRs) in schizophrenic patients with their own siblings, some with and some without other schizophrenia-related disorders [e.g., schizotypal personality disorder (SPD)], as well as with a group of unrelated normal controls.

METHODS

VBRs, measured by computed tomography, were compared in both groupwise and within-sibship analyses, the latter method providing a measure of control over familial/genetic factors related to VBR, but unrelated to schizophrenia.

RESULTS

The VBRs were significantly different across the groups, but the only significant pairwise group comparison was between the schizophrenia and no-SRD family member groups. In the within-sibship analyses, however, the VBRs of those with SPD and schizophrenia were similar, and both groups had significantly larger VBRs than their own siblings without SRD. In addition, siblings with a negative family history for SRD had larger VBRs than family history positive siblings.

CONCLUSIONS

The results suggest that specific schizophrenia-related genetic factors may help determine ventricular enlargement in familial schizophrenia. The larger VBRs in family history negative siblings might be attributable to genetic factors not specifically associated with schizophrenia, but which nevertheless increase its susceptibility.

The transfer origin for Bacteroides mobilizable transposon Tn4555 is related to a plasmid family from gram-positive bacteria

Conjugal transfer of Bacteroides mobilizable transposon Tn4555 was examined with an Escherichia coli-based assay system. It was shown that mobilization required the cis-acting oriT(Tn) region and that the Tn4555 mobA(Tn) gene and RK231 must be present in trans. With alkaline agarose gel electrophoresis and filter blot hybridizations, it was shown that at oriT(Tn) there was a site- and strand-specific cleavage event that was dependent on mobA(Tn). The 5' end of this cleavage site was mapped by primer extension, and the nucleotide sequence surrounding the site had homology to a family of oriT nick sites found in mobilizable plasmids of gram-positive bacteria. Removal of the nick site by deletion of 18 bp surrounding the site resulted in a significant loss of transfer activity.

Nitrate leaching from a Riverine clay soil under cereal rotation

Leaching of nitrate from a Red earth (Red Kandasol) at Wagga Wagga was measured during the wheat and lucerne phase of a crop rotation. Wheat was grown in 1993, and the site was sown to lucerne in 1994, a drought year. The paddock was re-sown to lucerne on 3 June 1995. In 1993, the soil water content in the 0·25-0 ·90 m layer had been maintained near its drained limit from previous harvest until the autumn break. With these initial conditions, current season rainfall displaced the resident soil water. Drainage measured at 0·25 m was 120 mm and produced 97 mm of drainage at 0·9 m. In contrast, the soil water storage in the 0·25-0· 90 m layer at the autumn break in 1995 was about 70 mm below the drained limit because of the drought in the preceding year. Under these conditions, drainage response differed from 1993 in that 112 mm of drainage at 0·90 m was generated by a much higher drainage of 178 mm at 0·25 m. These differences emphasise a need for appreciable soil water deficits in the subsoil in order to minimise drainage from the root-zone. Infiltration of rainfall, water redistribution, drainage, and transfer of NO-3-N within the soil profile were modelled using the Richard"s equation. The model gave acceptable predictions of evapotranspiration and its partitioning for transpiration, soil N transformations, and NO-3-N redistribution and leaching under wheat and lucerne. Nitrate leached below 0·25 m was 31 and 77 kg N/ha in 1993 and 1995, but only 4·2 and 12 kg N/ha leached beyond the root-zone, respectively. Root growth into the subsoil and uptake was effective in reducing the downward movement of NO-3-N. Leaching of NO-3-N below 0· 25 m produced 2·2 kmol H+ /ha in 1993 and 5·5 kmol H+ /ha in 1995. Corresponding values for net acidity production in 0-0·9 m layer were 0·3 and 0·9 kmol H+ /ha. It would appear from both measurements and simulations that management systems, either current or projected, cannot prevent the movement of NO-3-N from its zone of production. Acidification of upper soil layers is the inevitable consequence of such export, leading to the need for added alkalinity whenever the biomass is not returned to the soil.

A repeatable method for determination of carboxyhemoglobin levels in smokers

Fourteen male smokers participated in ten afternoon test sessions to determine the daily variation in expired breath carbon monoxide (CO), and whole blood percent carboxyhemoglobin (%COHb), hemoglobin and hematocrit levels. Each individual's test session was conducted at approximately the same time of day to estimate CO-related measures under relatively stable conditions. Subjects smoked ad libitum prior to testing. The 'usual brand' cigarette was smoked during the first measurement week (sessions 1-5 held on Monday through Friday) and a research cigarette prototype which primarily heats rather than burns tobacco (TOB-HT) was smoked by 12 of the 14 subjects for 3 weeks prior to and during the second measurement week (sessions 6-9 held on Tuesday through Friday). Following the last 'usual brand' measurement session, subjects completed 21 days of ad libitum smoking of the TOB-HT cigarette before starting sessions 6-9 to allow acclimation to the TOB-HT research cigarette. Following session 9, 11 of the 14 subjects continued to smoke the TOB-HT cigarette for an additional 3 weeks and then participated in an additional test session (session 10). The data indicate that daily measurements of afternoon %COHb and expired breath CO values for an individual are reproducible when using this protocol. Carboxyhemoglobin and expired breath CO levels were elevated by 24.4 and 30.6%, respectively, after switching to the TOB-HT cigarette. This increase was not due to an increase in the number of cigarettes consumed since the subjects smoked an average of 21 cigarettes prior to the measurement session when smoking either their 'usual brand' or the TOB-HT cigarette.

Development of decompensated dilated cardiomyopathy is associated with decreased gene expression and activity of the milrinone-sensitive cAMP phosphodiesterase PDE3A

BACKGROUND

Phosphodiesterase III (PDE3) inhibitors are inotropic agents used to treat congestive heart failure (CHF) and are less effective in patients with severe CHF. Little is known about relative changes in PDE3 activity or gene expression during the evolution of cardiomyopathy.

METHODS AND RESULTS

In the present study, we evaluated temporal changes in PDE3A gene expression before and after pacing-induced CHF in nine mongrel dogs. Three weeks of left ventricular (LV) pacing produced LV end-diastolic pressures of 15+/-1.7 mm Hg, whereas overt CHF at 4 to 5 weeks was associated with LV end-diastolic pressures of 24+/-1.7 mm Hg; prepacing values were 6.6+/-0.6 mm Hg. Total RNA isolated from LV tissues was analyzed on Northern blots; 10 unpaced normal hearts served as tissue controls. Signals for PDE3A mRNAs (7, 8, and 10 kb) or PDE4D (7.6 kb) were normalized against glyceraldehyde-3-phosphate dehydrogenase (GAPDH) or ribosomal 18S RNA. Before the onset of CHF, PDE3A/GAPDH ratios were not different between the control and 3-week paced groups. In contrast, all PDE3A/GAPDH ratios were selectively reduced by 52%, and PDE3A/18S was reduced by 70% (P<.05) in CHF; PDE4D/GAPDH (or 18S) was unchanged. LV tissues from four control and four CHF dogs were also processed to isolate cytosolic and microsomal membrane protein for cAMP PDE3 activity assays. CHF was associated with a significant 54% reduction (P<.05) in microsomal but not cytosolic PDE3 activity.

CONCLUSIONS

Selective downregulation of PDE3A may account in part for the ineffectiveness of milrinone in the treatment of severe CHF.

Regulation of Bacteriodes fragilis katB mRNA by oxidative stress and carbon limitation

Regulation of the katB catalase gene in the anaerobic bacterium Bacteroides fragilis was studied. Northern blot hybridization analyses revealed that katB was transcribed as an approximately 1.6-kb monocistronic mRNA. The levels of katB mRNA increased > 15-fold when anaerobic, mid-logarithmic-phase cultures were exposed to O2, O2 with paraquat, or hydrogen peroxide. Under anaerobic conditions, the low levels of katB mRNA increased in a growth-dependent manner, reaching maximum expression at late logarithmic or early stationary phase, followed by a decrease in stationary phase. Under anaerobic conditions, the expression of katB mRNA was strongly repressed by glucose and to a lesser extent by xylose. However, glucose repression was completely abolished upon exposure to oxygen. The nonfermentable carbon sources fumarate, succinate, acetate, and pyruvate did not significantly affect expression. Phosphate, nitrogen, and hemin limitation did not affect the expression of katB mRNA, suggesting that the nutritional control of katB expression is restricted to carbon and energy sources and not other forms of nutrient limitation. Primer extension analysis revealed that during both oxidative stress and carbon or energy limitation, katB utilized the same promoter region but transcription initiation occurred at two different nucleotides separated by 3 or 4 bases. Interestingly, a 6-bp inverted repeat sequence present in the katB regulatory region was also observed upstream of the B. fragilis superoxide dismutase gene sod. It is possible that this is a recognition site for a DNA binding protein involved in the regulation of oxidative stress genes in this organism.

QSAR treatment of multiple toxicities: the mutagenicity and cytotoxicity of quinolines

A series of 15 quinoline congeners were assayed for mutagenicity and cytotoxicity in the Ames test using strain TA100 bacteria. Statistical analysis of the data allowed simultaneous determination of the mutagenicity and cytotoxicity of each quinoline. These data were used to develop three quantitative structure-activity relationships (QSAR). In all three QSAR, the strength of the relationship between hydrophobicity (as measured by log P) and biological activity was similar as h was near 1 in all three cases. For the mutagenicity of these quinolines, both hydrophobic and steric interactions appear to be important. In contrast, the cytotoxicity is mainly affected by increasing hydrophobicity and by the addition of electron withdrawing substituents to the quinoline ring. Comparison to other QSAR from our laboratory and others lends support to these findings. Both simultaneous consideration of different biological activities and the comparison of newly developed QSAR with previous data for the purpose of lateral validation should be encouraged in future QSAR studies.

An international literature survey of "IARC Group I carcinogens" reported in mainstream cigarette smoke

The International Agency for Research on Cancer (IARC) currently lists 44 individual chemical agents, 12 groups or mixtures of chemicals and 13 exposure circumstances as "Group 1 human carcinogens". A comprehensive search of the published literature revealed that nine of the 44 chemical agents classified as "Group I carcinogens" by IARC have been reported to occur in mainstream cigarette smoke. The other 35 have never been reported to occur in cigarette smoke. The nine agents reported are benzene, cadmium, arsenic, nickel, chromium, 2-naphthyl-amine, vinyl chloride, 4-aminobiphenyl and beryllium. The reported yields of each of these nine agents in mainstream smoke varies widely. The range of yields reported for a given compound is influenced by the type of cigarette tested and when the analysis was conducted. In micrograms/cigarette, the ranges that have been reported for each of the nine compounds are: benzene (0.05-104), cadmium (0-6.67), arsenic (0-1.4), nickel (0-0.51), chromium (0.0002-0.5), 2-naphthylamine (0.0002-0.022), vinyl chloride (0.0013-0.0158), 4-aminobiphenyl (0.00019-0.005) and beryllium (0-0.0005). Although some of the variation in reported yields may be due to differences in analytical methodology, several correlations between the yield of a particular chemical in mainstream smoke and certain cigarette characteristics were observed. For example, charcoal filtration was associated with reduced vinyl chloride, and the concentration of sodium nitrate in the tobacco was positively correlated with the mainstream yield of both 2-naphthylamine and 4-aminobiphenyl. Benzene yield in mainstream cigarette smoke was correlated with the amount of tobacco burned and with the 'tar' level. Agronomic factors such as production practices and soil characteristics, and environmental conditions such as rainfall, reportedly influence the accumulation of metals, for example, cadmium, beryllium, chromium, nickel and arsenic, in the leaf. The use of fertilizers low in nitrate and heavy metals would be expected to substantially reduce the yields of most of the "IARC Group 1 carcinogens" reported to occur in mainstream cigarette smoke. Additionally, modifications in cigarette design, for instance, the use of enhanced charcoal filters or heated instead of burned tobacco, would also be expected to reduce the yields of several of these agents.

Usefulness of cytopathology and histology in the evaluation of Barrett's esophagus in a community hospital

BACKGROUND

Brush cytology and histology have been found to be complementary in the evaluation of Barrett's esophagus at a referral medical center. This study evaluated the usefulness of brush cytology and histology in a community hospital setting.

METHODS

One hundred consecutive patients with Barrett's esophagus underwent esophagogastroscopy performed by four staff gastroenterologists. Four quadrant biopsy specimens for histopathology at 3-cm intervals throughout the Barrett's segment and one brushing for cytology were obtained. All specimens were interpreted by four board-certified staff pathologists in a blinded fashion.

RESULTS

Histologic diagnosis included three adenocarcinomas, one high-grade dysplasia, six low-grade dysplasias, and one indeterminate dysplasia. Cytology diagnosed the same three adenocarcinomas, no high-grade dysplasia, three low-grade dysplasia, and two indeterminate dysplasias. The case of high-grade dysplasia on histology was diagnosed as normal by cytology. The six patients found to have low-grade dysplasia by histology were found to have low-grade dysplasia (3), indeterminate dysplasia (2), and no abnormality (1) by cytology. In no case was a higher grade of dysplasia diagnosed by cytology than by histology.

CONCLUSION

Adding brush cytology to histology increased the cost but not the diagnostic yield in the evaluation of Barrett's esophagus in a community hospital setting.

Plakinidine D, a new pyrroloacridine alkaloid from two ascidians of the genus Didemnum

A previously undescribed red Didemnum sp. collected in Indonesia contained a novel pyrroloacridine, plakinidine D (4), along with the known compounds 3,5-diiodo-4-methoxyphenethylamine (5) and ascididemin (6), both of which had previously been isolated from ascidians of the genus Didemnum. Plakinidine D (4) and 3,5-diiodo-4-methoxyphenethylamine (5) were also isolated from Didemnum rubeum from the Republic of Palau. Interestingly, a collection of D. rubeum from Indonesia did not contain plakinidine D (4), but instead contained 3,5-diiodo-4-methoxyphenethylamine (5) and ascididemin (6). The structure of plakinidine D (4) was elucidated by analysis of its spectral data. Plakinidine D (4) is closely related to plakinidines A-C (1-3), previously isolated from the sponge Plakortis sp.

In vitro and in vivo characterization of novel water-soluble dithio-bisphosphine 99mTc complexes

The water-soluble dithio-bis(hydroxymethyl)phosphine ligands (HOH2C)2P(CH2)2 S(CH2)3S(CH2)2P(CH2OH)2 and (HOH2C)2P(CH2)3S(CH2)3S(CH2)3P(CH2OH)2 were complexed with 99mTc. The 99mTc-P2S2 complexes were formed in high radiochemical purity by simple mixing of 99mTcO-4 with the ligands or by transchelation from 99mTc-citrate. The 99mTc-P2S2 complexes were stable over a wide range of pHs and did not undergo in vitro decomposition for < or = 24 h. High performance liquid chromatographic analysis indicated the formation of singular chemical species. Retention times for each of the new 99mTc-P2S2 complexes are identical to those of corresponding Re(V) complexes, suggesting similar chemical species at the tracer level. Results of this study suggest that the combination of thioether and (hydroxymethyl)phosphine donor centers in new, multidentate ligand frameworks might aid in the development of new bifunctional chelating agents for the use of radiolabeling specific biomolecules.

Phosphodiesterase inhibition improves agonist-induced relaxation of hypertensive pulmonary arteries

Pulmonary artery (PA) relaxation in response to vasodilators is significantly attenuated in models of hypoxia-induced pulmonary hypertension (HPH). The activity of phosphodiesterases (PDE) which hydrolyze vasodilatory second messengers may be increased by HPH, which thereby contributes to attenuated vasodilatory responses. The purpose of this study was to determine the effect of PDE inhibition on agonist-induced relaxation of PA from normal rats and rats with HPH (F(IO2), 0.1 for 14 days). Isolated PA rings were suspended in baths containing Krebs-Henseliet salt solution and contracted with U46619 in the presence or absence of a PDE3 (milrinone) or PDE4 (rolipram) inhibitor. Isoproterenol and forskolin induced concentration-dependent relaxation of PA rings from normal rats and rats with HPH, but the degree of relaxation was significantly less (*P < .05; n = 4) in PA from rats with HPH. Treatment with either PDE inhibitor significantly improved (*P < .05; n = 4) the magnitude of agonist-induced relaxation in PA rings from normal rats and rats with HPH. Additionally, PDE3A transcripts (8 and 10 kb) were increased (3.8 +/- 1.6-fold and 3.9 +/- 1.2-fold; n = 3, respectively) in PAs from rats with HPH compared with normal controls. These data show that inhibition of PDE3 and PDE4 activity can significantly improve PA relaxation in HPH and that expression of PDE3A mRNA is increased during HPH. These findings suggest that PDEs play an important role in the development and maintenance of HPH.

Immunoglobulin E levels and anticollagen antibodies in patients with postburn hypertrophic scars

Immunoglobulin E (IgE) levels and eosinophil counts were measured in 18 former patients with burn injuries attending an outpatient clinic for hypertrophic scarring. In 15 of these 18 former patients with burns, IgG anticollagen antibodies were also measured. Earlier reports in the literature have suggested that a local immune reaction against collagen might play a role in enhancing inflammation, thereby increasing scar formation. In addition, we have previously reported an increase in allergic symptoms in patients with keloids and hypertrophic scars. Antibodies to the following collagen types were measured: human type I, human type III, bovine type I, and bovine type III. IgG anticollagen antibody levels were correlated with percentage third-degree burn, number of weeks after burn injury, and the patient's age. An increase in percentage third-degree burn and in number of weeks after burn injury was statistically significantly associated with an increase in serum anticollagen antibody level. Six of the 18 patients had higher than normal IgE levels (p value = 0.0002).

Validity of the family history method for identifying schizophrenia-related disorders

We examined the family history method's validity for identifying schizophrenia related disorders (SRD) by comparing family history and family study derived diagnoses. First degree relatives (n = 284) of 48 psychiatrically disordered probands, predominantly with schizophrenia, were diagnosed using the Family History RDC (FH-RDC) which include three psychotic schizophrenia related disorders (P-SRD): schizophrenia, chronic SAD and chronic unspecified functional psychosis (CUFP). Supplementary criteria for schizophrenia related personality disorders (SRP), derived to identify schizotypal and paranoid personality disorders (PD), were also assessed. About two thirds of these relatives (n = 196; 69.0%) were independently diagnosed by RDC and DSM-III-R on both axis I and axis II in a family study. The specificity was 1.0 (178/178) and the sensitivity of the family history derived diagnosis for P-SRD was 0.72 (13/18). Sensitivity for P-SRD was improved, however, by inclusion of SRP which captured three of the five false negative relatives. The sensitivity of SRP for schizotypal or paranoid PD was 0.39 (15/38) and the specificity was 0.92 (127/138). The FH-RDC have moderately good sensitivity and excellent specificity for the psychotic schizophrenia related disorders. While family history criteria for SRP are not a good proxy for schizotypal or paranoid PD, they can enhance the family history method's sensitivity for SRD.

Conformational properties of the prion octa-repeat and hydrophobic sequences

We have used circular dichroism to study synthetic peptides from two important regions of the prion protein: the N-terminal octa-repeat domain and a highly conserved hydrophobic section. Our results show that the octa-repeat sequence in free solution can adopt a non-random, extended conformation with properties similar to the poly-L-proline type II left-handed helix. We also show that the conformation can be changed by temperature, organic solvents (e.g. acetonitrile) and on binding to phospholipid vesicles. We compared CD data from two peptides corresponding to the hydrophobic region between residues 106 and 136 which contained either methionine or valine at position 129. This variation represents a common polymorphism in humans which has been shown to influence predisposition towards iatrogenic and sporadic CJD. There was no detectable difference between the CD spectra of these peptides irrespective of the solvent conditions we used.

The Bacteroides mobilizable transposon Tn4555 integrates by a site-specific recombination mechanism similar to that of the gram-positive bacterial element Tn916

The Bacteroides mobilizable transposon Tn4555 is a 12.2-kb molecule that encodes resistance to cefoxitin. Conjugal transposition is hypothesized to occur via a circular intermediate and is stimulated by coresident tetracycline resistance elements and low levels of tetracycline. In this work, the ends of the transposon were identified and found to consist of 12-bp imperfect inverted repeats, with an extra base at one end. In the circular form, the ends were separated by a 6-bp "coupling sequence" which was associated with either the left or the right transposon terminus when the transposon was inserted into the chromosome. Tn4555 does not duplicate its target site upon insertion. Using a conjugation-based transposition assay, we showed that the coupling sequence originated from 6 bases of genomic DNA flanking either side of the transposon prior to excision. Tn4555 preferentially transposed into a 589-bp genomic locus containing a 207-bp direct repeat. Integration occurred before or after the repeated sequence, with one integration site between the two repeats. These observations are consistent with a transposition model based on site-specific recombination. In the bacteriophage lambda model for site-specific recombination, the bacteriophage recombines with the Escherichia coli chromosome via a 7-bp "crossover" region. We propose that the coupling sequence of Tn4555 is analogous in function to the crossover region of lambda but that unlike the situation in lambda, recombination occurs between regions of nonhomologous DNA. This ability to recombine into divergent target sites is also a feature of the gram-positive bacterial transposon Tn916.

Eye tracking, attention, and schizotypal symptoms in nonpsychotic relatives of patients with schizophrenia

BACKGROUND

Biological relatives of patients with schizophrenia demonstrate an increased prevalence of schizotypal personality disorder symptoms, eye tracking deficits, and attentional disturbances. We investigated whether these hypothesized components of a schizophrenia-related phenotype are associated with one another or are independent in nonpsychotic relatives of patients with schizophrenia.

METHODS

Eighty-three nonpsychotic first-degree relatives of 38 patients with schizophrenia and 45 control subjects without a psychiatric diagnosis underwent clinical evaluation, eye tracking evaluation, and the Continuous Performance Test (CPT) of visual attention.

RESULTS

Eye tracking qualitative rating was more powerful than quantitative eye tracking measures or CPT measures in discriminating relatives of patients with schizophrenia from control subjects. Correlations between neurocognitive variables and DSM-III-R schizotypal personality disorder symptom clusters suggested that CPT errors of omission are associated with positive schizotypal symptoms. Eye tracking measures were not significantly correlated with schizotypal symptoms or CPT errors in relatives of patients with schizophrenia.

CONCLUSIONS

Eye tracking deficits in the relatives of patients with schizophrenia are unrelated to CPT deficits and schizotypal symptoms. Eye tracking deficits and disturbances in visual attention may be separate components of a schizophrenia-related phenotype and should be considered as independent factors in genetic studies of schizophrenia.

Oxidative stress response in an anaerobe, Bacteroides fragilis: a role for catalase in protection against hydrogen peroxide

Survival of Bacteroides fragilis in the presence of oxygen was dependent on the ability of bacteria to synthesize new proteins, as determined by the inhibition of protein synthesis after oxygen exposure. The B. fragilis protein profile was significantly altered after either a shift from anaerobic to aerobic conditions with or without paraquat or the addition of exogenous hydrogen peroxide. As determined by autoradiography after two-dimensional gel electrophoresis, approximately 28 newly synthesized proteins were detected in response to oxidative conditions. These proteins were found to have a broad range of pI values (from 5.1 to 7.2) and molecular weights (from 12,000 to 79,000). The hydrogen peroxide- and paraquat-inducible responses were similar but not identical to that induced by oxygen as seen by two-dimensional gel protein profile. Eleven of the oxidative response proteins were closely related, with pI values and molecular weights from 5.1 to 5.8 and from 17,000 to 23,000, respectively. As a first step to understanding the resistance to oxygen, a catalase-deficient mutant was constructed by allelic gene exchange. The katB mutant was found to be more sensitive to the lethal effects of hydrogen peroxide than was the parent strain when the ferrous iron chelator bipyridyl was added to culture media. This suggests that the presence of ferrous iron in anaerobic culture media exacerbates the toxicity of hydrogen peroxide and that the presence of a functional catalase is important for survival in the presence of hydrogen peroxide. Further, the treatment of cultures with a sublethal concentration of hydrogen peroxide was necessary to induce resistance to higher concentrations of hydrogen peroxide in the parent strain, suggesting that this was an inducible response. This was confirmed when the bacterial culture, treated with chloramphenicol before the cells were exposed to a sublethal concentration of peroxide, completely lost viability. In contrast, cell viability was greatly preserved when protein synthesis inhibition occurred after peroxide induction. Complementation of catalase activity in the mutant restored the ability of the mutant strain to survive in the presence of hydrogen peroxide, showing that the catalase (KatB) may play a role in oxidative stress resistance in aerotolerant anaerobic bacteria.

Effects of cysteine-to-serine mutations on structural and functional properties of prostaglandin endoperoxide synthase

Previous studies have demonstrated that mutation in prostaglandin endoperoxide synthase-1 of Cys313 or Cys540 to Ser residues reduces cyclooxygenase and peroxidase activities by 80-90%. In the present work, we investigated the effect of these Cys-to-Ser mutations on the sensitivity of the enzyme to inhibition by cyclooxygenase inhibitors, the ability of the enzyme to form homodimers, the extent of glycosylation of the enzyme, and the sensitivity of the enzyme to maleimide enzyme inhibitors. No significant differences were observed between native and mutant enzymes in any of these parameters. The results suggest that the loss of activity observed in the mutant enzymes is not due to major differences in protein folding or aggregation. Most surprising was the finding that the sensitivity of prostaglandin H synthase-1 to maleimide-containing inhibitors was not affected by mutating any of the Cys to Ser. This indicates that the inhibition of cyclooxygenase activity affected by N-ethylmaleimide and N-carboxyheptylmaleimide is not due to modification of a cysteine residue.