The axonemal microtubules of the Chlamydomonas flagellum differ in tubulin isoform content

Little is known of the molecular basis for the diversity of microtubule structure and function found within the eukaryotic flagellum. Antibodies that discriminate between tyrosinated alpha tubulin and post-translationally detyrosinated alpha tubulin were used to localize these complementary tubulin isoforms in flagella of the single-celled green alga Chlamydomonas reinhardtii. Immunofluorescence analysis of intact axonemes detected both isoforms along most of the lengths of flagella; however, each had a short distal zone rich in tyrosinated tubulin. Localizations on splayed axonemes revealed that the microtubules of the central-pair apparatus were rich in tyrosinated tubulin, while outer doublets contained a mixture of both isoforms. Immunoelectron analysis of individual outer doublets revealed that while tyrosinated tubulin was present in both A and B tubules, detyrosinated tubulin was largely confined to the wall of the B hemi-tubules. The absence of detyrosinated tubulin from the A tubules of the outer doublets and the microtubules of the central pair, both of which extend past the B hemi-tubules of the outer doublets in the flagellar tip, explained the appearance of a tyrosinated tubulin-rich distal zone on intact axonemes. Localizations performed on cells regenerating flagella revealed that flagellar assembly used tyrosinated tubulin; detyrosination of the B tubule occurred during later stages of regeneration, well after microtubule polymerization. The developmental timing of detyrosination, which occurs over a period during which the regrowing flagella begin to beat more effectively, suggests that post-translational modification of the B tubule surface may enhance dynein/B tubule interactions that power flagellar beating.

Arabidopsis thaliana responses to mechanical stimulation do not require ETR1 or EIN2

Plants exposed to repetitive touch or wind are generally shorter and stockier than sheltered plants. These mechanostimulus-induced developmental changes are termed thigmomorphogenesis and may confer resistance to subsequent stresses. An early response of Arabidopsis thaliana to touch or wind is the up-regulation of TCH (touch) gene expression. The signal transduction pathway that leads to mechanostimulus responses is not well defined. A role for ethylene has been proposed based on the observation that mechanostimulation of plants leads to ethylene evolution and exogenous ethylene leads to thigmomorphogenetic-like changes. To determine whether ethylene has a role in plant responses to mechanostimulation, we assessed the ability of two ethylene-insensitive mutants, etr1-3 and ein2-1, to undergo thigmomorphogenesis and TCH gene up-regulation of expression. The ethylene-insensitive mutants responded to wind similarly to the wild type, with a delay in flowering, decrease in inflorescence elongation rate, shorter mature primary inflorescences, more rosette paraclades, and appropriate TCH gene expression changes. Also, wild-type and mutant Arabidopsis responded to vibrational stimulation, with an increase in hypocotyl elongation and up-regulation of TCH gene expression. We conclude that the ETR1 and EIN2 protein functions are not required for the developmental and molecular responses to mechanical stimulation.

Alternating site mechanism of the kinesin ATPase

The processivity of the microtubule-kinesin ATPase has been investigated using stopped-flow kinetic methods to measure the binding of each motor domain of the dimeric kinesin (K401) to the microtubule and the release of the fluorescent ADP analog, 2'(3')-O-(N-methylanthraniloyl)adenosine 5'-diphosphate (mantADP) from the active site of the motor domain. The results show that the release of two molecules of ADP from dimeric kinesin (K401) after the binding of kinesin ADP to the microtubule is a sequential process leading to biphasic kinetics. The maximum rate of release of mantADP from the first motor domain of K401 or monomeric K341 is fast (300 s-1) and independent of added nucleotide. The rate of mantADP release from the second motor domain of K401 is slow in the absence of added nucleotide (0.4 s-1) and reaches a maximum rate of 300 s-1 at saturating concentrations of ATP. High concentrations of ADP stimulate mantADP release from the second head to a maximum rate of 3.8 s-1. The nonhydrolyzable analog AMP-PNP and ATP-gamma S also stimulate ADP release from the second head (maximum rate of 30 s-1), suggesting that ATP hydrolysis is not necessary to stimulate the ADP release. These experiments establish an alternating site mechanism for dimeric kinesin whereby ATP binding to one kinesin active site stimulates the release of ADP from the second site such that the reactions occurring at the active sites of the two monomer units are kept out of phase from each other by interactions between the heads. These results define the steps of the ATPase pathway that lead to the efficient coupling of ATP hydrolysis to force production in a processive reaction whereby force production in forming a tight microtubule complex by one head is coupled to the rate-limiting release of the other head from the microtubule.

Pathway of ATP hydrolysis by monomeric and dimeric kinesin

The ATPase mechanism for a monomeric Drosophila kinesin construct, K341, was determined by pre-steady-state kinetic methods and compared to dimeric kinesin, K401. We directly measured the kinetics of binding mantATP (a fluorescent ATP analog) to the microtubule K341 complex, the dissociation of K341 from the microtubule, and release of phosphate and ADP from K341. Measurements of phosphate release kinetics at low salt concentration show that K341 hydrolyzes 18 molecules of ATP per kinesin monomer prior to release from the microtubule. At a higher salt concentration the amplitude of the pre-steady-state burst of phosphate release was reduced to 8 molecules per kinesin monomer. The maximum rate of dissociation of K341 from the microtubule following the addition of ATP was 22 s-1. The rate of mantADP release from the M.K341.mantADP complex increased as a function of tubulin concentration with a second-order rate constant of 11 microM-1 s-1 for K341 binding to the microtubule and reached a maximum rate of mantADP release of 303 s-1. ADP release kinetics were also determined by monitoring the binding of mantATP to K341.ADP and K401.ADP after mixing with microtubules. We show that monomeric kinesin remains associated with the microtubule through multiple rounds of ATP hydrolysis. This apparent processivity implies that one of the functions of the cooperative interaction between the two kinesin heads in dimeric kinesin is for the reactions occurring on one kinesin head to facilitate the release of the adjacent head from the microtubule.

Alcohol dependence in adult children of alcoholics: longitudinal evidence of early risk

This study investigates familial alcoholism effects and the comparative probability of risk for alcohol dependence in adult children of alcoholics (ACAs) with a control group of non-ACAs. A cohort of 12,686 young adults from the National Longitudinal Survey of Youth (NLSY) is examined over a five-year period and conventional and lineal intergenerational models of alcoholism transmission are assessed. The results of multivariate logistic regression analyses indicate that the risk is relatively greater for male ACAs; sons of alcoholics drink significantly more heavily, experience problems earlier, and develop alcohol dependence more extensively than female ACAs or non-ACAs of either gender. The extent of dependence found in subjects with a lineal history of alcoholism on the father's side of the family, as well as heavy drinking, cigarette smoking and drinking onset in adolescence should be considered as critical predisposing factors of high risk for dependence at later ages. These observations corroborate clinical studies and support a growing body of biopsychosocial research literature.

RNA secondary structure switching during DNA synthesis catalyzed by HIV-1 reverse transcriptase

Changes in RNA secondary structure have been found to play important roles in translational regulation, protein synthesis, and mRNA splicing. In studies utilizing a 66 nucleotide RNA template with a stable hairpin structure, we have examined the effects of RNA secondary structure on HIV-1 reverse transcriptase activity. We identify several pause sites in the stem of the hairpin and show that these pause sites are correlated with the free energy of melting the next base pair in the stem. We also identify a pause site appearing in the loop of the hairpin and show that this is due to the rapid formation of a new hairpin structure occurring during the progress of DNA polymerization through the hairpin. The rapid change in RNA secondary structure to form the new hairpin selectively destabilizes the major hairpin and thereby accelerates the rate at which reverse transcriptase reads through RNA secondary structure.

Reversible cerebral hypoperfusion in Lyme encephalopathy

Lyme encephalopathy (LE) presents with subtle neuropsychiatric symptoms months to years after onset of infection with Borrelia burgdorferi. Brain magnetic resonance images are usually normal. We asked whether quantitative single photon emission computed tomography (SPECT) is a useful method to diagnose LE, to measure the response to antibiotic therapy, and to determine its neuroanatomic basis. In 13 patients with objective evidence of LE, SPECT demonstrated reduced cerebral perfusion (mean perfusion defect index [PDI] = 255), particularly in frontal subcortical and cortical regions. Six months after treatment with 1 month of intravenous ceftriaxone, perfusion significantly improved in all 13 patients (mean PDI = 188). In nine patients with neuropsychiatric symptoms following Lyme disease, but without objective abnormalities (e.g., possible LE), perfusion was similar to that of the treated LE group (mean PDI = 198); six possible LE patients (67%) had already received ceftriaxone prior to our evaluation. Perfusion was significantly lower in patients with LE and possible LE than in 26 normal subjects (mean PDI = 136), but 4 normal subjects (15%) had low perfusion in the LE range. We conclude that LE patients have hypoperfusion of frontal subcortical and cortical structures that is partially reversed after ceftriaxone therapy. However, SPECT cannot be used alone to diagnose LE or determine the presence of active CNS infection.

A hexameric helicase encircles one DNA strand and excludes the other during DNA unwinding

The bacteriophage T7 DNA helicase/primase (gene 4 protein) is a ring-like hexamer that encircles ssDNA and requires forked DNA to catalyze DNA unwinding. We report that optimal rates of unwinding of forked DNA require ssDNA tails of 55 nucleotides on the 5'-to-3' strand and 15 nucleotides on the 3'-to-5' strand. Surprisingly, streptavidin bound to a biotinylated 3'-end fully substitutes for the 3'-to-5' ssDNA tail. This suggests that excluding the 3'-to-5' DNA strand from the center of the helicase is an essential aspect of the mechanism of hexameric helicase-catalyzed DNA unwinding. We also report that streptavidin bound to a biotinylated dT within the 5'-to-3' strand of the duplexed region abolishes DNA unwinding; whereas, streptavidin bound to a biotinylated dT within the duplexed region of the other strand has no effect. These results unambiguously demonstrate that the T7 gene 4 protein is a 5'-to-3' helicase and imply that during DNA unwinding the 5'-to-3' strand transverses the center of the ring while the 3'-to-5' strand is excluded from the center of the ring. Implications for collisions between a helicase and other protein-DNA complexes are discussed.

Increase of 5HT and VIP immunoreactivity within the hamster (Mesocricetus auratus) SCN during chronic MAOI treatment

The effects of chronic treatment with the monoamine oxidase inhibitor (MAOI), clorgyline (CLG; 2 mg/kg per day) on serotonin (5HT) and vasoactive intestinal peptide (VIP) immunoreactivity (IR) within the hamster suprachiasmatic nucleus (SCN) were examined. Optical densities of 5HT IR and VIP IR were increased by MAOI treatment. VIP IR was increased in both the ventrolateral and dorsal regions of the SCN, suggesting that VIP content was increased within both perikarya and terminals of VIP neurons. The results suggest that previously described effects of MAOIs on the mammalian circadian system may be mediated in part, by their effects on serotonergic input to VIP neurons within the SCN.

Effect of RNA secondary structure on RNA cleavage catalyzed by HIV-1 reverse transcriptase

Using a synthetic 66 nucleotide RNA template containing a stable hairpin structure derived from the HIV-1 genome, six predominant RNA cleavage products are found during DNA synthesis catalyzed by HIV-1 RT. These major RNA cleavage sites correlate well with the pause sites seen during primer elongation [Suo, Z., & Johnson, K. A. (1997) Biochemistry (manuscript submitted for publication)]. Thus, the RNase H and polymerase activities of RT are coupled as RT reads through the RNA secondary structure. The distance between the two active sites of HIV-1 RT is 19-20 base pairs of DNA/RNA heteroduplex when the next template base is not paired. The heteroduplex region was enlarged by 2-3 base pairs once RT encounters the template hairpin. A model for this change is presented. At the pause sites, the burst amplitudes of RNA cleavage are larger than the corresponding reaction amplitudes of next nucleotide incorporation at the polymerase site. Measurement of the steady state rates of RNA cleavage confirms that all substrates dissociate slowly from RT. These results suggest that while substrates are bound nonproductively at the polymerase site, they are still bound productively at the RNase H active site of RT. Characterization of an RNase H-deficient RT mutant (D443N) shows that RNase H activity is not critical for RT to read through the RNA secondary structure. HIV-1 nucleocapsid does not increase the processivity of HIV-1 RT but inhibits DNA elongation by blocking the binding of RT to DNA substrates.

Effect of RNA secondary structure on the kinetics of DNA synthesis catalyzed by HIV-1 reverse transcriptase

The effect of RNA secondary structure on the kinetics of DNA synthesis catalyzed by HIV-1 RT was determined using a 66 nucleotide RNA template containing a stable 12 base pair hairpin structure. Prior to reaching the hairpin structure, the primer elongation by RT was fast and the kinetics of polymerization was not affected by the presence of the secondary structure. Once within the regions of template secondary structure, polymerization was much slower and RT paused at five distinct sites [Suo, Z., & Johnson, K. A. (1997) Biochemistry (manuscript submitted for publication)]. Kinetic analysis of single nucleotide incorporation at the pause sites showed polymerization occurred by both a fast phase (54-76 s-1) and a slow phase (0.07-0.4 s-1) during a single binding event. The biphasic kinetics suggests that the DNA substrates are initially bound in both productive and nonproductive states at the polymerase site of RT. The nonproductively bound DNA is slowly converted into a productive state without dissociation from the enzyme. At the pause sites, the enzyme amplitudes of the fast phase are small (4.0-15%) while the amplitudes of the slow phase are large (11-40%). In contrast, only the reaction at the fast phase was observed at the nonpause sites and the enzyme amplitudes were large (63-66%) although the nucleotide incorporation rates (62-78 s-1) are similar to the fast phase rates at the pause sites. These indicate that DNA substrates were bound predominantly nonproductively at pause sites and productively at nonpause sites. However, the overall binding affinity of DNA substrates was measured by the nitrocellulose-DEAE double filter binding assay, binding affinity at both pause sites and nonpause sites was similar (9-38 nM). This indicates that substrates are bound tightly at the large binding cleft of HIV-1, although they may not be productively bound at the polymerase active site. These results and those reported elsewhere [Suo, Z., & Johnson, K. A. (1997) Biochemistry (manuscript submitted for publication)] are consistent with a model in which, at pause sites, HIV-1 RT remains bound to DNA substrates waiting for the melting of the next stem base pair of template secondary structure. Upon melting of the stem base pair, polymerization to fill the open template site is fast and largely irreversible, allowing RT to read through the stable hairpin structures.

Synovial fluid interleukin 6, tumor necrosis factor, and nitric oxide values in dogs with osteoarthritis secondary to cranial cruciate ligament rupture

OBJECTIVE

To measure and compare values of interleukin 6 (IL-6), tumor necrosis factor (TNF), and nitric oxide (NO) metabolites in synovial fluid from canine joints with osteoarthritis (OA) secondary to naturally acquired cranial cruciate ligament (CCL) rupture and experimental CCL transection.

ANIMALS

57 dogs (clinical group) with OA secondary to CCL rupture; 5 dogs (experimental group) with OA secondary to CCL transection; 19 control dogs with normal joints.

PROCEDURE

Joints were radiographed and graded for seventy of OA. Synovial fluid was collected from dogs: at surgery from the clinical group, at 90 days after surgery from the experimental group, and at necropsy from the control group. Activities of IL-6 and TNF, as well as concentration of the NO metabolites (NO2-/NO3-) were measured, and results were reported as mean +/- SEM.

RESULTS

IL-6 activity in dogs of the clinical (290 +/- 40 U/ml) and experimental (494 +/- 165 U/ml) groups was greater than that in control dogs (6 +/- 1.6 U/ml; P < 0.05). The TNF values in dogs of the clinical (3.0 +/- 0.5 pg/ml) and experimental (2.0 +/- 0.9 pg/ml) groups were lower than those in control dogs (8.6 +/- 2.3 pg/ml; P < 0.05). The IL-6 values were negatively associated with radiographic score of OA and were positively associated with age (R2 = 26.5%, P < 0.05).

CONCLUSION

Dogs with OA secondary to naturally acquired CCL rupture and experimental CCL transection had significantly different alterations in synovial fluid IL-6 and TNF values. The decrease in IL-6 activity with advancing OA was independent of the increase in IL-6 activity with aging.

CLINICAL RELEVANCE

IL-6 and TNF may be involved in pathogenesis of OA secondary to naturally acquired and experimentally induced CCL rupture.

Resilience to drinking vulnerability in women with alcoholic parents: the moderating effects of dyadic cohesion in marital communication

Data from a subsample of women (N = 4,235) in two waves of the National Longitudinal Surveys of Youth (NLSY) are used to examine the relationship between parental alcoholism and alcohol use in adult life. Dyadic cohesion in marital communication (frequency of interaction and agreement on substantive issues that affect couples) is investigated as a resilience factor that could potentially mitigate adverse drinking outcomes in adult children of alcoholics (ACAs). A moderated mediation model is estimated using a Two-Stage Least Squares (2SLS) regression analysis. The results indicated that an imputed transmission of risk for drinking vulnerability in women ACAs, controlling for nonACA status, was effectively moderated by positive dyadic interaction.

Movement-related potentials in Parkinson's disease. Motor imagery and movement preparation

Movement-related potentials (MRPs) associated with voluntary movements reflect cortical activity associated with processes of movement preparation and movement execution. Early-stage pre-movement activity is reduced in amplitude in Parkinson's disease. However, it is unclear whether this neurophysiological deficit relates to preparatory or execution-related activity, since previous studies have not been able to separate different functional components of MRPs. Motor imagery is thought to involve mainly processes of movement preparation, with reduced involvement of end-stage movement execution-related processes. Therefore, MRP components relating to movement preparation and execution may be examined separately by comparing MRPs associated with imagined and actual movements. In this study, MRPs were recorded from 14 subjects with Parkinson's disease and 10 age-matched control subjects while they performed a sequential button-pressing task, and while they imagined performance of the same task. Early-stage pre-movement activity was present in both Parkinson's disease patients and control subjects when they imagined movement, but was reduced in amplitude compared with that for actual movement. Movement execution-related components, arising predominantly from the primary motor cortex, were relatively unaffected in Parkinson's disease subjects. However, motor preparatory processes, probably involving the supplementary motor area, were reduced in amplitude overall and abnormally prolonged, indicating impaired termination following the motor response. Further, this impaired termination of preparatory-phase activity was observed only in patients with more severe parkinsonian symptoms, and not in early-stage Parkinson's disease.

Therapeutic effect of liposomal superoxide dismutase in an animal model of retinopathy of prematurity

A newborn rat model of retinopathy of prematurity was used to test the hypothesis that a lack of superoxide dismutase contributes to the retinal vaso-attenuation seen during exposure of the animals to hyperoxic conditions. To determine the endogenous superoxide dismutase activity of the retina under hyperoxic conditions, litters of albino rats were placed in either constant 80% ambient oxygen (constant hyperoxia), or placed in 21% oxygen (room air) immediately after birth. Every other day, for 14 days, several rat pups were sacrificed and their retinas removed for the determination of total superoxide dismutase (SOD) activity and manganese-associated SOD activity. An attempt was made to increase retinal SOD activity by intraperitoneal administration of exogenous SOD encapsulated in polyethylene glycol-modified liposomes. Additional litters were exposed to the same oxygen treatments and supplemented twice daily with either liposome-encapsulated superoxide dismutase in saline or liposomes containing saline without SOD. Animals were sacrificed at various time points for the determination of total superoxide dismutase activity and computer-assisted analysis of vessel density and avascular area. Animals raised in an atmosphere of constant 80% oxygen had significantly reduced levels of retinal superoxide dismutase activity through 6 days of life when compared to their room air-raised littermates. At 6 days of age, daily supplementation with liposome-encapsulated SOD had significantly increased retinal superoxide dismutase activity and reduced oxygen-induced vaso-attenuation as evidenced by increased vessel density and decreased avascular area, when compared to littermates exposed to constant hyperoxia that received control liposomes. Superoxide dismutase had no adverse effects on any of the animals regardless of treatment. Tracing experiments demonstrated that liposomes entered the retina and were found in cells morphologically resembling microglia. Delivery of SOD to the retina via long-circulating liposomes proved beneficial, suggesting that restoration and/or supplementation of endogenous antioxidants in oxygen-damaged retinal tissue is a potentially valuable therapeutic strategy.

Preparation of peptide and protein powders for inhalation

Innovations in biotechnology and recombinant techniques have led to a large increase in the number of macromolecule drugs developed over the last several years. These molecules are enabling new therapies for many previously untreated or poorly treated diseases. Due to poor oral absorption, most biopharmaceuticals are delivered by injection. Medical science, health care providers and consumers have been searching for alternative methods of delivering macromolecule drugs. Animal and human clinical studies have demonstrated that pharmacological doses of bioactive peptides and proteins pass, by a natural biological process, from the lungs into the bloodstream or local tissue. New macromolecule drugs are also being developed for treatment of respiratory diseases such as cystic fibrosis, adult and infant respiratory distress syndromes, asthma and emphysema. This paper reviews formulations for delivering therapeutic aerosols to the lungs. Particular emphasis will be placed on preparing fine powders containing macromolecule drugs.

H. M.'s medial temporal lobe lesion: findings from magnetic resonance imaging

Although neuropsychological studies of the amnesic patient H. M. provide compelling evidence that normal memory function depends on the medial temporal lobe, the full extent of his surgical resection has not been elucidated. We conducted magnetic resonance imaging studies to specify precisely the extent of his bilateral resection and to document any other brain abnormalities. The MRI studies indicated that the lesion was bilaterally symmetrical and included the medial temporal polar cortex, most of the amygdaloid complex, most or all of the entorhinal cortex, and approximately half of the rostrocaudal extent of the intraventricular portion of the hippocampal formation (dentate gyrus, hippocampus, and subicular complex). The collateral sulcus was visible throughout much of the temporal lobe, indicating that portions of the ventral perirhinal cortex, located on the banks of the sulcus, were spared; the parahippocampal cortex (areas TF and TH) was largely intact. The rostrocaudal extent of the ablation was approximately 5.4 cm (left) and 5.1 cm (right). The caudal 2 cm, approximately, of the hippocampus body (normal length, approximately 4 cm) was intact, although atrophic. The temporal stem was intact. Outside the temporal lobes, the cerebellum demonstrated marked atrophy, and the mammillary nuclei were shrunken. The lateral temporal, frontal, parietal, and occipital lobe cortices appeared normal for age 66 years. The mediodorsal thalamic nuclei showed no obvious radiological changes. These findings reinforce the view that lesions of the hippocampal formation and adjacent cortical structures can produce global and enduring amnesia and can exacerbate amnesia beyond that seen after more selective hippocampal lesions.

Late-gestation treatment of pregnant cows with trenbolone acetate does not increase subsequent growth of heifer calves

Fifty crossbred cows (38 multiparous and 12 nulliparous) were used to evaluate in utero androgenization of heifer calves with trenbolone acetate. Three 200-mg trenbolone acetate (Finaplix-H) implants were implanted in the ear of treated cows (n = 24) on d 214 +/- 11 of gestation; the remaining animals (n = 26) were used as controls. Cows' rate of gain, serum levels of trenbolone acetate, gestation length, degree of dystocia, percentage bred back, days until conception, and 24-h milk production were evaluated. Fourteen-day weigh periods until parturition indicated that trenbolone acetate-treated dams had an increased (P < .05) average daily gain (1.05 +/- .1 kg) compared with control cows (.55 +/- .1 kg). Serum concentrations of trenbolone acetate were higher (P < .01) in treated cows with a peak at 9 d after implantation and returned to basal concentrations by d 77. Treatment did not affect degree of dystocia among all cows (P > .05) but seemed to increase (P < .01) the incidence of dystocia in nulliparous cows compared with nulliparous control cows. Gestation length and subsequent fertility were not affected by treatment (P > .05). Similarly, there was no difference in 24-h milk production (P > .05) between treated and control cows. Calf birth weight, phenotypic measurements at birth, vigor, average daily gain, carcass characteristics, and heifer reproductive tract and ovarian weights did not differ with treatment (P > .05). These data showed that late-gestation treatment with 600 mg of trenbolone acetate significantly increased weight gain of dams without demonstrating any androgenizing effects on the growth or physical characteristics of heifer calves.

Therapeutic effect of liposomal superoxide dismutase in an animal model of retinopathy of prematurity

A newborn rat model of retinopathy of prematurity was used to test the hypothesis that a lack of superoxide dismutase contributes to the retinal vaso-attenuation seen during exposure of the animals to hyperoxic conditions. To determine the endogenous superoxide dismutase activity of the retina under hyperoxic conditions, litters of albino rats were placed in either constant 80% ambient oxygen (constant hyperoxia), or placed in 21% oxygen (room air) immediately after birth. Every other day, for 14 days, several rat pups were sacrificed and their retinas removed for the determination of total superoxide dismutase (SOD) activity and manganese-associated SOD activity. An attempt was made to increase retinal SOD activity by intraperitoneal administration of exogenous SOD encapsulated in polyethylene glycol-modified liposomes. Additional litters were exposed to the same oxygen treatments and supplemented twice daily with either liposome-encapsulated superoxide dismutase in saline or liposomes containing saline without SOD. Animals were sacrificed at various time points for the determination of total superoxide dismutase activity and computer-assisted analysis of vessel density and avascular area. Animals raised in an atmosphere of constant 80% oxygen had significantly reduced levels of retinal superoxide dismutase activity through 6 days of life when compared to their room air-raised littermates. At 6 days of age, daily supplementation with liposome-encapsulated SOD had significantly increased retinal superoxide dismutase activity and reduced oxygen-induced vaso-attenuation as evidenced by increased vessel density and decreased avascular area, when compared to littermates exposed to constant hyperoxia that received control liposomes. Superoxide dismutase had no adverse effects on any of the animals regardless of treatment. Tracing experiments demonstrated that liposomes entered the retina and were found in cells morphologically resembling microglia. Delivery of SOD to the retina via long-circulating liposomes proved beneficial, suggesting that restoration and/or supplementation of endogenous antioxidants in oxygen-damaged retinal tissue is a potentially valuable therapeutic strategy.

Repair of propanodeoxyguanosine by nucleotide excision repair in vivo and in vitro

Repair of the exocyclic DNA adduct propanodeoxyguanosine (PdG) was assessed in both in vivo and in vitro assays. PdG was site-specifically incorporated at position 6256 of M13MB102 DNA, and the adducted viral genome was electroporated into repair-proficient and repair-deficient Escherichia coli strains. Comparable frequencies of PdG --> T and PdG --> A mutations at position 6256 were detected following replication of the adducted genomes in wild-type E. coli strains. A 4-fold increase in the frequencies of transversions and transitions was observed in E. coli strains deficient in Uvr(A)BC-dependent nucleotide excision repair. A similar increase in the replication of the adduct containing strand was observed in the repair-deficient strains. No change in the frequency of targeted mutations was observed in strains deficient in one or both of the genes coding for 3-methyladenine glycosylase. Incubation of purified E. coli Uvr(A)BC proteins with a duplex 156-mer containing a single PdG adduct resulted in removal of a 12-base oligonucleotide containing the adduct. Incubation of the same adducted duplex with Chinese hamster ovary cell-free extracts also resulted in removal of the adduct. PdG was a better substrate for repair by the mammalian nucleotide excision repair complex than the bacterial repair complex and was approximately equal to a thymine-thymine dimer as a substrate for the former. The results of these in vivo and in vitro experiments indicate that PdG, a homolog of several endogenously produced DNA adducts, is repaired by the nucleotide excision repair pathway.

Stability of gamma-glutamyltransferase activity in calf sera after refrigerated or frozen storage

OBJECTIVES

To examine stability of -glutamyltransferase (GGT) activity in stored serum from neonatal calves.

ANIMALS

10 commercial beef calves between 36 and 60 hours old.

PROCEDURE

Serum samples were obtained from the calves, and each sample was divided into 8 aliquots. Serum GGT activity was measured on day 0 (fresh) and days 1, 2, 3, and 4 of refrigerated storage (4 C) and weeks 1, 2, and 3 of frozen storage (-20 C).

RESULTS

Serum GGT activities for each of the refrigerated aliquots did not significantly differ from day zero, with serum GGT activity (expressed as a percentage of initial activity) > 99% on all 4 days. Serum GGT activity in frozen aliquots decreased significantly after 1 and 2 weeks of frozen storage, 97 and 98%, respectively; however, this decrease in GGT activity was not biologically significant. The observed GGT activity did not decrease significantly in the samples stored frozen for 3 weeks; these samples retained 99% of initial activity.

CONCLUSION

The observed stability of serum GGT activity indicates that serum may be obtained, stored, and batch processed at a later time. This stability during storage is important to the success of a bovine passive transfer monitoring program based on GGT activity.

Characterization of the mouse gene encoding phospholipid transfer protein

The mouse gene encoding phospholipid transfer protein (PLTP) was cloned from 129/SvJ lambdaFIX(R) II library and characterized for the first time. It is comprised of 16 exons separated by 15 introns. Its gene organization strikingly resembles that encoding the human PLTP; the exon-intron junctions in these two genes are completely conserved. Sequencing analysis reveals that the putative promoter of mouse PLTP gene consists of a TATA-box, a high GC region, and several consensus sequences for the binding of transcription factors. Within the first 200 bp of the 5'-flanking region, the mouse and human PLTP genes share 81.1% identity of nt sequences and contain the consensus sequences for the transcription factors AP-2 and Sp1 at the same locations.

Evaluation of a novel assay of potential toxicity/neurotoxicity of carpet emissions (VOCs) in mice

A private testing laboratory utilizing the whole-body plethysmograph/head-only exposure apparatus outlined in the respiratory irritation assay ASTM E981-84, along with a novel exposure regimen, has reported neurotoxic effects and mortality in mice exposed to relatively low levels of volatile organic compounds (VOCs) emitted from a number of consumer products. This methodology was evaluated by exposing groups of mice, including unrestrained and sham-treated animals, to VOCs generated from a sample of carpet reported to be neurotoxic using the modified assay. General toxicological (haematological measurements, organ weights, gross pathology, histopathology) and specific neurotoxicity (functional observations, body temperature, histopathology of nervous tissues) parameters were evaluated. No effects related to exposure to carpet VOCs were observed in the mice. However, despite careful handling, a number of effects were observed which were attributed to the repeated restraint of mice in the ASTM E981 apparatus. These included a number of minor physical injuries, decreased body weights, altered thymus weights, compression damage to the liver and haemorrhage of the pituitary gland. It was concluded that the modification of the original ASTM E981 methodology may result in physical injuries and stress which may significantly affect any evaluation of toxicity and neurotoxicity in treated animals and result in inaccurate conclusions.

Resorbable and non-resorbable augmentation devices for tenorrhaphy of xenografts in extensor tendon deficits: 12 week study

Resorbable (poly-L-lactide) and non-resorbable (polyethylene terephathalate) tendon augmentation devices (TAD) in conjunction with a pericardial adhesion barrier, were designed to strengthen tenorrhaphies and were evaluated in an ovine extensor tendon deficit model in a short term study. Fifteen centimetres of tendon were resected and replaced with kangaroo tail tendon xenografts that had been cross-linked with 0.075% glutaraldehyde (GA) at 4 degrees C for one or seven days. Compared with tenorrhaphies performed with Kessler sutures alone, both types of TAD were more effective at preventing tenorrhaphy dehiscence, and thus maintaining tendon function. Furthermore, tensile strength of TAD tenorrhaphies increased significantly between zero and twelve weeks. For xenografts cross-linked in GA for one day, the tensile strength of tenorrhaphies with the resorbable TAD rose from 38 +/- 9 N at time zero, to 116 +/- 46 N at twelve weeks, while non-resorbable TAD tenorrhaphy strength at time zero was 42 +/- 16 N and 99 +/- 27 N at twelve weeks. For xenografts cross-linked with GA for seven days, similar increases in tensile strength of tenorrhaphies, with the two types of TAD were found. As there was no significant difference in mechanical performance or tissue response between the two TAD types in the first 12 weeks, use of the resorbable poly-L-lactide device may be advantageous clinically. Tensile strengths of midsections of the tendon xenograft cross-linked for 7 days was not significantly diminished 12 weeks after implantation and these xenografts were partially remodelled around the periphery. However, the tensile strength of xenografts cross-linked for one day declined significantly between time zero (319 +/- 80 N) and twelve weeks (239 +/- 92 N), suggesting that this degree of cross-linking was inadequate for maintenance of mechanical strength. Evaluation of the performance of tenorrhaphy augmentation devices with xenografts, over a longer implantation period, is required to further understand their usefulness for reconstruction of traumatic tendon injuries.

Comparative modeling of the three-dimensional structure of the calmodulin-related TCH2 protein from Arabidopsis

Plants adapt to various stresses by developmental alterations that render them less easily damaged. Expression of the TCH2 gene of Arabidopsis is strongly induced by stimuli such as touch and wind. The gene product, TCH2, belongs to the calmodulin (CaM) family of proteins and contains four highly conserved Ca(2+)-binding EF-hands. We describe here the structure of TCH2 in the fully Ca(2+)-saturated form, constructed using comparative molecular modeling, based on the x-ray structure of paramecium CaM. Like known CaMs, the overall structure consists of two globular domains separated by a linker helix. However, the linker region has added flexibility due to the presence of 5 glycines within a span of 6 residues. In addition, TCH2 is enriched in Lys and Arg residues relative to other CaMs, suggesting a preference for targets which are more negatively charged. Finally, a pair of Cys residues in the C-terminal domain, Cys126 and Cys131, are sufficiently close in space to form a disulfide bridge. These predictions serve to direct future biochemical and structural studies with the overall aim of understanding the role of TCH2 in the cellular response of Arabidopsis to environmental stimuli.

Fine mapping of an imprinted gene for familial nonchromaffin paragangliomas, on chromosome 11q23

Hereditary nonchromaffin paragangliomas (PGL; glomus tumors; MIM 168000) are mostly benign, slow-growing tumors of the head and neck region, inherited from carrier fathers in an autosomal dominant fashion subject to genomic imprinting. Genetic linkage analysis in two large, unrelated Dutch families assigned PGL loci to two regions of chromosome 11, at 11q23 (PGL1) and 11q13.1 (PGL2). We ascertained a total of 11 North American PGL families and confirmed maternal imprinting (inactivation). In three of six families, linkage analysis provided evidence of linkage to the PGL1 locus at 11q23. Recombinants narrowed the critical region to an approximately 4.5-Mb interval flanked by markers D11S1647 and D11S622. Partial allelic loss of strictly maternal origin was detected in 5 of 19 tumors. The greatest degree of imbalance was detected at 11q23, distal to D11S1327 and proximal to CD3D. Age at onset of symptoms was significantly different between fathers and children (Wilcoxon rank-sum test, P < .002). Affected children had an earlier age at onset of symptoms in 39 of 57 father-child pairs (chi2 = 7.74, P < .006). However, a more conservative comparison of the number of pairs in which a child had > or = 5 years earlier age at onset (n = 33) vis-a-vis that of complementary pairs (n = 24) revealed no significant difference (chi2 = 1.42, P > .2). Whether these data represent genetic anticipation or ascertainment bias can be addressed only by analysis of a larger number of father-child pairs.

Conformational coupling in DNA polymerase information transfer

The extraordinary fidelity of DNA replication during forward polymerization and exonuclease error correction is largely a function of a conformational change that occurs in response to a correct dNTP binding to properly base-paired duplex DNA. The conformational change serves as a kinetic barrier to effect the rapid incorporation of correct bases while minimizing the rate of polymerization with incorrect bases and allowing for selective removal of mismatches. However, in spite of the number of attractive features to the conformational change model, the evidence in support of such a rate-limiting step is still subject to significant uncertainty. It is the challenge of further work on DNA polymerases as well as many other enzyme systems to devise new methods to define the transient state of the enzyme during catalysis and to relate the kinetic and thermodynamic parameters to the enzyme structure.

Plant responses to environmental stress: regulation and functions of the Arabidopsis TCH genes

Expression of the Arabidopsis TCH genes is markedly upregulated in response to a variety of environmental stimuli including the seemingly innocuous stimulus of touch. Understanding the mechanism(s) and factors that control TCH gene regulation will shed light on the signaling pathways that enable plants to respond to environmental conditions. The TCH proteins include calmodulin, calmodulin-related proteins and a xyloglucan endotransglycosylase. Expression analyses and localization of protein accumulation indicates that the potential sites of TCH protein function include expanding cells and tissues under mechanical strain. We hypothesize that at least a subset of the TCH proteins may collaborate in cell wall biogenesis.

Comparative pharmacokinetics of [14C]metosulam (N-[2,6-dichloro-3-methylphenyl]-5,7-dimethoxy-1,2,4- triazolo[1,5a]-pyrimidine-2-sulfonamide) in rats, mice and dogs

This study was conducted to provide data on the pharmacokinetics of [14C]metosulam (N-[2,6-dichloro-3-methylphenyl]-5,7-dimethoxy-1,2,4-triazolo-[1,5a]- pyrimidine-2-sulfonamide). Groups of male Sprague-Dawley rats, CD-1 mice and Beagle dogs were given a single oral gavage dose of 100 mg [14C]metosulam kg-1 body weight and blood, urine, feces and selected tissue specimens were collected up to 168 h for rats and mice and 216 h post-dosing for dogs. Two of these dogs received a second oral dose of 100 mg kg-1 and were humanely euthanized at 12 h post-dosing and selected tissues were collected. The third dog was administered an intravenous dose of 1 mg kg-1 and plasma, urine and feces were collected for 72 h post-dosing. Specified tissue specimens were analyzed for 14C activity and selected tissues were evaluated for localization of 14C activity by histoautoradiography. Selected urine and plasma specimens were also profiled for metabolites by high-performance liquid chromatography. [14C]Metosulam was absorbed rapidly (t1/2 < 1 h) in all three species. Mice and dogs absorbed ca. 20% of the orally administered dose of [14C]metosulam, compared to > 70% absorption in the rat. Analysis of 14C activity and histoautoradiography of the dog eyes indicated that the retina, a target for toxicity in the dog, did exhibit affinity for the radiotracer. There was no evidence of 14C localization in the kidneys of dogs or in the eyes of rats. In rats and mice the 14C plasma time-course was fit to a two-compartment pharmacokinetic model, whereas the dog was fit to a one-compartment model. The half-lives for the rapid initial (alpha) and slower terminal phases (beta) were 9 h and 60 h for the rat and 20 h and 155 h for mice, respectively. The dog had an elimination t1/2 of 73 h. In all three species, [14C]metosulam and metabolites were excreted in the urine and quantitatively the relative amount of [14C]metosulam metabolism followed the pattern of mice > rats > dogs. These data suggest that the observed ocular lesion in dogs is due to metosulam and may in part be due to its selective affinity for the dog retina.

Life in a changing world: TCH gene regulation of expression and responses to environmental signals

The Arabidopsis TCH genes were discovered as a consequence of their marked upregulation of expression in response to seemingly innocuous stimuli such as touch. Further analyses have indicated that these genes are upregulated by a variety of diverse stimuli. Understanding the mechanism(s) and factors that control TCH gene regulation will shed light on the signaling pathways that enable plants to respond to changing environmental conditions. The TCH proteins include calmodulin, calmodulin-related proteins and a xyloglucan endotransglycosylase. Expression analyses and localization of protein accumulation indicate that the potential sites of TCH protein function include expanding cells and tissues under mechanical strain. We hypothesize that the TCH proteins may collaborate in cell wall biogenesis.

Birth outcomes in pregnant women taking fluoxetine

BACKGROUND

Although fluoxetine is the most frequently prescribed antidepressant drug in the United States, its safety in pregnant women has not been established.

METHODS

From 1989 through 1995, we prospectively identified 228 pregnant women taking fluoxetine. We compared the outcomes of their pregnancies with those of 254 women identified in a similar manner who were not taking fluoxetine.

RESULTS

The rate of spontaneous pregnancy loss did not differ significantly between the women treated with fluoxetine and the control women (10.5 percent and 9.1 percent, respectively), nor was the rate of major structural anomalies significantly different (5.5 percent vs. 4.0 percent). Among the 97 infants exposed to fluoxetine who were evaluated for minor anomalies, the incidence of three or more minor anomalies was significantly higher than among 153 similarly examined control infants (15.5 percent vs. 6.5 percent, P=0.03). As compared with the 101 infants exposed to fluoxetine only during the first and second trimesters, the 73 infants exposed during the third trimester had higher rates of premature delivery (relative risk, 4.8; 95 percent confidence interval, 1.1 to 20.8), admission to special-care nurseries (relative risk, 2.6; 95 percent confidence interval, 1.1 to 6.9), and poor neonatal adaptation, including respiratory difficulty, cyanosis on feeding, and jitteriness (relative risk, 8.7; 95 percent confidence interval, 2.9 to 26.6). Birth weight was also lower and birth length shorter in infants exposed fluoxetine late in gestation.

CONCLUSION

Women who take fluoxetine during pregnancy do not have an increased risk of spontaneous pregnancy loss or major fetal anomalies, but women who take fluoxetine in the third trimester are at increased risk for perinatal complications.

Chronic dietary toxicity/oncogenicity studies on 2,4-dichlorophenoxyacetic acid in rodents

Forms of 2,4-dichlorophenoxyacetic acid (collectively known as 2,4-D) are herbicides used to control a wide variety of broadleaf and woody plants. Doses in the 2-year chronic/oncogenicity rat study were 0, 5, 75, and 150 mg/kg/day. The chronic toxicity paralleled subchronic findings, and a NOEL of 5 mg/kg/day was established. A slight increase in astrocytomas observed (in males only) at 45 mg/kg/day in a previously conducted chronic rat study was not confirmed in the present study at the high dose of 150 mg/kg/ day. Doses in the 2-year mouse oncogenicity studies were 0, 5, 150, and 300 mg/kg/day for females and 0, 5, 62.5, and 125 mg/ kg/day for males. No oncogenic effect was noted in the study. In summary, the findings of these studies indicate low chronic toxicity of 2,4-D and the lack of oncogenic response to 2,4-D following chronic dietary exposure of 2,4-D in the rat and mouse.

Interlocking intramedullary nail stabilization of a femoral fracture in a dog with osteomyelitis

Complications developed in a dog that underwent intramedullary pin and cerclage wire fixation of a comminuted femoral fracture. The fracture was unstable, the intramedullary pin protruded through the skin over the hip, and Staphylococcus sp was isolated from the fracture site. The loose pin was removed, and the fracture was restabilized with a 6.0-mm interlocking intramedullary nail and 3 interlocking screws. Cephalexin was given orally for 6 weeks. Eight weeks after the second surgery, the fracture was healed radiographically. Seventeen months later, the dog had a persistent mild lameness that was associated with low-grade osteomyelitis. The lameness resolved after the implants were removed, and antibiotics were administered. In human beings, interlocking intramedullary nail stabilization is an accepted treatment for open and contaminated fractures. Chronic infection of bone may be attributable to bacteria in biofilm surrounding implants, necessitating implant removal for resolution.

4-Phenylcyclohexene: 2-week inhalation toxicity and neurotoxicity studies in Swiss-Webster mice

4-Phenylcyclohexene (4-PCH) is a by-product formed during the polymerization of styrene-butadiene latex used in carpet backing. Limited reports suggest that exposure to very low levels of 4-PCH or other emission products following new carpet installation may result in health complaints. Significantly, it has been claimed that Swiss-Webster mice held in neck restraints and exposed head-only to approximately 0.4 ppm 4-PCH for a few hours suffered severe toxicity including death. A 2-wk inhalation and neurotoxicity study was therefore conducted in Swiss-Webster mice using standard methods of toxicity testing. Groups of 40 mice were exposed to 0, 7, 18 or 71 ppm (near-saturated atmosphere) 4-PCH vapour, 6 hr/day for 9 consecutive days. Data were collected on a wide variety of clinical, neurological and histopathological parameters including extensive neurohistopathology. All animals survived the exposures, and there were no treatment-related effects. Because of the occurrence of spontaneous lesions in two high-dose group mice, 40 additional males were exposed to 0 ppm or a near-saturated atmosphere of 4-PCH under the same exposure regimen. No treatment-related lesions were observed in the follow-up study, confirming the conclusions of the original study. These findings, consistent with the reported lack of toxicity of inhaled 4-PCH in rats, do not suggest a direct, organic, association between low-level 4-PCH exposure and human complaints. Further, the results of this study suggest that positive findings in mice may have been due to methodological problems and not to exposure to 4-PCH.

Force-plate analysis of gait before and after surgical excision of calcified lesions of the supraspinatus tendon in two dogs

Two dogs with supraspinatus calcifying tendinopathy were lame in their forelimbs and were treated by the surgical excision of the calcified lesion. The lameness in both dogs improved after surgery without additional medical treatment, as evidenced by force-plate analysis of their gait.

Methylmethacrylate and bone screw repair of seventh lumbar vertebral fracture-luxations in dogs

Fracture-luxations of the seventh lumbar vertebrae in two large dogs were stabilised with bone screws and methylmethacrylate. Screws inserted bilaterally into the bodies of the lumbar vertebrae and ilial wings were left protruding by about 2 cm, and embedded in methylmethacrylate bone cement. Implant failure occurred in one dog six days after surgery, necessitating a revision of the fixation. Fracture healing and return of normal ambulation occurred in both dogs. Implants were removed in one dog because of screw loosening and discomfort.

Subchronic toxicity of ingested 1,3-dichloropropene in rats and mice

Male and female Fischer 344 rats and B6C3F1 mice (10/sex/ dose group) were given 0, 5, 15, 50, or 100 mg/kg/day (rats) or 0, 15, 50, 100, or 175 (mice) mg/kg/day racemic 1,3-dichloropropene (1,3-D), respectively, via their diets for 13 weeks. Satellite groups of rats (recovery = 10 rats/sex/group) ingesting 0 or 100 mg/kg/ day 1,3-D were provided control feed for an additional 4 weeks to examine recovery. The test material was stabilized in the feed by microencapsulation in a starch/sucrose matrix (80/20). The body weights of male and female rats ingesting > or = 5 and > or = 15 mg/kg/ day, respectively, and of all treatment groups of mice were decreased relative to controls. The terminal body weights of high dose group rats and mice were decreased approximately 13-16%. A number of changes in serum biochemical parameters and decreases in organ weights accompanied the depressed body weights of these animals. Histologically, the only treatment-related change observed was a slight degree of basal cell hyperplasia and hyperkeratosis in the nonglandular portion of the stomachs of a majority of male and female rats ingesting > or = mg/kg/day. After the 4-week recovery period, most treatment-related changes were noted to be reversible in nature. No treatment-related histopathological changes were observed in the tissues of treated mice. Based upon relatively slight depressions in body weights at the lowest dosages tested, the no-observed-adverse-effect levels for male rats and both sexes of mice were determined to be 5 mg/kg/day and 15 mg/kg/ day, respectively. A no-observed-effect level of 5 mg/kg/day was established for female rats.

A polysomnographic study of sleep disturbance in community elderly with self-reported environmental chemical odor intolerance

Subjective sleep complaints and food intolerances, especially to milk products, are frequent symptoms of individuals who also report intolerance for low-level odors of various environmental chemicals. The purpose of the present study was to evaluate the objective nature of nocturnal sleep patterns during different diets, using polysomnography in community older adults with self-reported illness from chemical odors. Those high in chemical odor intolerance (n = 15) exhibited significantly lower sleep efficiency (p = .005) and lower rapid-eye-movement (REM) sleep percent (p = .04), with a trend toward longer latency to REM sleep (p = .07), than did those low in chemical intolerance (n = 15), especially on dairy-containing as compared with nondairy (soy) diets. The arousal pattern of the chemical odor intolerant group differed from the polysomnographic features of major depression, classical organophosphate toxicity, and subjective insomnia without objective findings. The findings suggest that community elderly with moderate chemical odor intolerance and minimal sleep complaints exhibit objectively poorer sleep than do their normal peers. Individual differences in underlying brain function may help generate these observations. The data support the need for similar studies in clinical populations with chemical odor intolerance, such as multiple chemical sensitivity patients and perhaps certain veterans with "Persian Gulf Syndrome."

Time-dependent sensitization of plasma beta-endorphin in community elderly with self-reported environmental chemical odor intolerance

This study examined plasma beta-endorphin as a marker of the physiological stress response in community elderly who were either high (n = 15) or low (n = 15) in self-rated frequency of illness from environmental chemical odors. Individuals who report nonatopic multiple sensitivities to or intolerances for low levels of environmental chemicals also claim high rates of comorbid food sensitivities or intolerances. Subjects gave 9 AM blood samples for plasma beta-endorphin 90 min after ingesting either 1% fat cow's milk or a soy-based nondairy drink, on six different mornings in the laboratory after all-night sleep recordings. The six sessions-were divided into three sets of two successive days each, with each set [involving baseline (ad lib milk), nondairy (soy-based), and dairy diets] separated from the next by 3 weeks. In the chemically tolerant subjects, stably lower beta-endorphin levels suggested that milk may have been a physiologically less stressful beverage than was the soy drink. In contrast, the chemical odor intolerant group exhibited a) increased levels of plasma beta-endorphin averaged over the 6 days (p = .02); and b) marked fluctuations in endorphin from one laboratory day to the next (Group x Diet x Day interaction, p = .005). The findings were consistent with time-dependent, context-dependent sensitization of beta-endorphin in the chemical odor intolerant individuals.

Mechanism of NO-induced oxidation of myoglobin and hemoglobin

Nitric oxide (NO) has been implicated as mediator in a variety of physiological functions, including neurotransmission, platelet aggregation, macrophage function, and vasodilation. The consumption of NO by extracellular hemoglobin and subsequent vasoconstriction have been suggested to be the cause of the mild hypertensive events reported during in vivo trials of hemoglobin-based O2 carriers. The depletion of NO from endothelial cells is most likely due to the oxidative reaction of NO with oxyhemoglobin in arterioles and surrounding tissue. In order to determine the mechanism of this key reaction, we have measured the kinetics of NO-induced oxidation of a variety of different recombinant sperm whale myoglobins (Mb) and human hemoglobins (Hb). The observed rates depend linearly on [NO] but show no dependence on [O2]. The bimolecular rate constants for NO-induced oxidation of MbO2 and HbO2 are large (k.ox,NO = 30-50 microM-1 s-1 for the wild-type proteins) and similar to those for simple nitric oxide binding to deoxygenated Mb and Hb. Both reversible NO binding and NO-induced oxidation occur in two steps: (1) bimolecular entry of nitric oxide into the distal portion of the heme pocket and (2) rapid reaction of noncovalently bound nitric oxide with the iron atom to produce Fe(2+)-N=O or with Fe(2+)-O-O delta- to produce Fe(3+)-OH2 and nitrate. Both the oxidation and binding rate constants for sperm whale Mb were increased when His(E7) was replaced by aliphatic residues. These mutants lack polar interactions in the distal pocket which normally hinder NO entry into the protein. Decreasing the volume of the distal pocket by replacing Leu(B10) and Val(E11) with aromatic amino acids markedly inhibits NO-induced oxidation of MbO2. The latter results provide a protein engineering strategy for reducing hypertensive events caused by extracellular hemoglobin-based O2 carriers. This approach has been explored by examining the effects of Phe(B10) and Phe(E11) substitutions on the rates of NO-induced oxidation of the alpha and beta subunits in recombinant human hemoglobin.

Expression of the APC tumor suppressor protein in oligodendroglia

Mutations of the adenomatous polyposis coli (APC) tumor suppressor gene have been linked to familial polyposis, an inherited predisposition to colon cancer, and a high percentage of sporadic colon adenomas. Although this gene is best known for its role in development of bowel neoplasms, in recent studies we have found that APC mRNA levels are greatly enriched in brain compared with peripheral tissues. To help define its role in the nervous system, in this study we have determined its cellular localization immunohistochemically in adult rat brain sections and have detected intense APC immunoreactivity in oligodendrocytes. Since prominent APC immunostaining is detected in cell bodies of mature oligodendrocytes, these antibodies may provide a useful addition to available oligodendrocyte markers. Although the cellular function of APC remains undefined, previous biochemical studies have demonstrated that APC is associated with catenins, cytoplasmic proteins involved in regulating cell-cell adhesion. We propose that, in addition to its critical role in ensuring normal maturation of colonic epithelial cells, the APC tumor suppressor protein also regulates the adhesive properties of oligodendrocytes.

Purification and characterization of two monomeric kinesin constructs

Steady-state and pre-steady-state kinetic methods were used to analyze two shorter Drosophila kinesin constructs (K341 and K366) in comparison to K401. K341, K366, and K401 represent the kinesin motor domains containing the N-terminal 341, 366, or 401 amino acids, respectively. K401 is dimeric (Kd = 37 +/- 17 nM) whereas both K366 and K341 are monomeric [Correia et al. (1995) Biochemistry 34, 4898-4907]. Like native kinesin and K401, K341 and K366 demonstrate low ATPase activity in the absence of microtubules (0.03 and 0.01 s-1, respectively), and ADP release is rate-limiting during steady-state turnover. Microtubules activate the steady-state ATPase to 84 s-1 for K341 (K(m),ATP = 100 microM; K0.5,MT = 3.2 microM tubulin) and 64 s-1 for K366 (K(m),ATP = 65 microM; K0.5,MT = 2.5 microM tubulin) in comparison to K401 at 20 s-1 (K(m)ATP = 60 microM; K0.5,MT = 1 microM tubulin). The rapid quench experiments for all three constructs show a burst of product formation during the first turnover, indicating the rate-limiting step for the microtubule-activated ATPase occurs after ATP hydrolysis. The interaction of K341 and K366 with the microtubule was analyzed by electron microscopy. The results show that K341 and K366, like K401, bind to the microtubule with an 8 nm axial periodicity. However, the addition of K366 to microtubules resulted in significant aggregation of microtubules. The pre-steady-state kinetic results show that K341 retains the kinetic and structural properties necessary to compare directly the kinetic properties of monomeric and dimeric kinesins, although the microtubule-activated ATPase is significantly faster for the monomeric constructs, suggesting possible interactions in the dimer which inhibit ATP turnover as part of the coupling to force production.

Ultrasound imaging of the appendix testis and appendix epididymis

The appendix testis and epididymis are well visualized on ultrasound examination. It is important to recognize the normal anatomy of the appendages to exclude them as a cause of pathology and confirm their presence as normal structures. We describe the appearances of the appendices testis and epididymis in fifty-one consecutive patients presenting to the Southampton Radiology Department. The appendix testis was identified on 80% of testes examined by ultrasound and the appendix epididymis on 6% of testes.

Metabolic rate, organ mass, and mitochondrial proton leak variations in lean and obese rats

The purpose of this study was to determine if differences in metabolic rate between lean and obese strains of rats were associated with differences in proton leak across the inner mitochondrial membrane. Metabolic rates were determined for each of five obese Zucker, Sprague-Dawley, and Fisher 344 rats and three lean Zucker rats by 24-hour indirect respiration calorimetry measurements. Feed intakes were different (P < 0.05) among all strains, with the obese Zucker rats having the greatest intakes. Adjusted to a common dietary intake, the obese Zucker rats had at least 21% lower heat productions than the lean strains of rats. Following the calorimetry measurements, the rats were sacrificed, internal organs were removed and weighed and mitochondria were isolated from the liver. Internal organs composed a larger proportion of lean body mass in obese compared to lean rats. Respiration rates and membrane potentials of the mitochondria were then determined. Proton leak kinetics were visualized by plotting proton leak (calculated from respiration rate) against membrane potential. The lean rats had a 2-3-fold higher proton leak rate than the obese Zucker rats at the same membrane potential. A low mitochondrial proton leak rate may explain part of the abnormal heat productions and bioenergetic efficiencies in the obese Zucker rat.