Methodological and Reporting Quality of Noninferiority Randomized Controlled Trials Comparing Antiretroviral Therapies: A Systematic Review

BACKGROUND

It is unclear whether the reporting quality of antiretroviral (ARV) noninferiority (NI) randomized controlled trials (RCTs) has improved since the CONSORT guideline release in 2006. The primary objective of this systematic review was assessing the methodological and reporting quality of ARV NI-RCTs. We also assessed reporting quality by funding source and publication year.

METHODS

We searched Medline, Embase, and Cochrane Central from inception to 14 November 2022. We included NI-RCTs comparing ≥2 ARV regimens used for human immunodeficiency virus treatment or prophylaxis. We used the Cochrane Risk of Bias 2.0 tool to assess risk of bias. Screening and data extraction were performed blinded and in duplicate. Descriptive statistics were used to summarize data; statistical tests were 2 sided, with significance defined as P < .05. The systematic review was prospectively registered (PROSPERO CRD42022328586), and not funded.

RESULTS

We included 160 articles reporting 171 trials. Of these articles, 101 (63.1%) did not justify the NI margin used, and 28 (17.5%) did not provide sufficient information for sample size calculation. Eighty-nine of 160 (55.6%) reported both intention-to-treat and per-protocol analyses, while 118 (73.8%) described missing data handling. Ten of 171 trials (5.9%) reported potentially misleading results. Pharmaceutical industry-funded trials were more likely to be double-blinded (28.1% vs 10.3%; P = .03) and to describe missing data handling (78.5% vs 59.0%; P = .02). The overall risk of bias was low in 96 of 160 studies (60.0%).

CONCLUSIONS

ARV NI-RCTs should improve NI margin justification, reporting of intention-to-treat and per-protocol analyses, and missing data handling to increase CONSORT adherence.

Establishment of a Novel Rat Model of Gram-Negative Periprosthetic Joint Infection Using Cementless Hip Hemiarthroplasty

BACKGROUND

Gram-negative periprosthetic joint infections (GN-PJIs) present unique challenges. Our aim was to establish a clinically representative GN-PJI model that recapitulates biofilm formation in vivo. We also hypothesized that biofilm formation on the implant surface would affect its ability to osseointegrate.

METHODS

Three-dimensionally-printed medical-grade titanium hip implants were used to replace the femoral heads of male Sprague-Dawley rats. GN-PJI was induced using 2 bioluminescent Pseudomonas aeruginosa strains: a reference strain (PA14-lux) and a mutant biofilm-defective strain (ΔflgK-lux). Infection was monitored in real time using an in vivo imaging system (IVIS) and magnetic resonance imaging (MRI). Bacterial loads were quantified utilizing the viable colony count. Biofilm formation at the bone-implant interface was visualized using field-emission scanning electron microscopy (FE-SEM). Implant stability, as an outcome, was directly assessed by quantifying osseointegration using microcomputed tomography, and indirectly assessed by identifying gait-pattern changes.

RESULTS

Bioluminescence detected by the IVIS was focused on the hip region and demonstrated localized infection, with greater ability of PA14-lux to persist in the model compared with the ΔflgK-lux strain, which is defective in biofilm formation. This was corroborated by MRI, as PA14-lux induced relatively larger implant-related abscesses. Biofilm formation at the bone-implant interface induced by PA14-lux was visualized using FE-SEM versus defective-biofilm formation by ΔflgK-lux. Quantitatively, the average viable colony count of the sonicated implants, in colony-forming units/mL, was 3.77 × 108 for PA14-lux versus 3.65 × 103 for ΔflgK-lux, with a 95% confidence interval around the difference of 1.45 × 108 to 6.08 × 108 (p = 0.0025). This difference in the ability to persist in the model was reflected significantly on implant osseointegration, with a mean intersection surface of 4.1 × 106 ± 1.99 × 106 μm2 for PA14-lux versus 6.44 × 106 ± 2.53 × 106 μm2 for ΔflgK-lux and 7.08 × 106 ± 1.55 × 106 μm2 for the noninfected control (p = 0.048).

CONCLUSIONS

To our knowledge, this proposed, novel in vivo biofilm-based model is the most clinically representative for GN-PJI to date, since animals can bear weight on the implant, poor osseointegration was associated with biofilm formation, and localized PJI was assessed by various modalities.

CLINICAL RELEVANCE

This model will allow for more reliable testing of novel biofilm-targeting therapeutics.

Molecular mechanisms of biofilm-based antibiotic resistance and tolerance in pathogenic bacteria

Biofilms are surface-attached groups of microbial cells encased in an extracellular matrix that are significantly less susceptible to antimicrobial agents than non-adherent, planktonic cells. Biofilm-based infections are, as a result, extremely difficult to cure. A wide range of molecular mechanisms contribute to the high degree of recalcitrance that is characteristic of biofilm communities. These mechanisms include, among others, interaction of antimicrobials with biofilm matrix components, reduced growth rates and the various actions of specific genetic determinants of antibiotic resistance and tolerance. Alone, each of these mechanisms only partially accounts for the increased antimicrobial recalcitrance observed in biofilms. Acting in concert, however, these defences help to ensure the survival of biofilm cells in the face of even the most aggressive antimicrobial treatment regimens. This review summarises both historical and recent scientific data in support of the known biofilm resistance and tolerance mechanisms. Additionally, suggestions for future work in the field are provided.

Molecular mechanisms of biofilm-based antibiotic resistance and tolerance in pathogenic bacteria

Biofilms are surface-attached groups of microbial cells encased in an extracellular matrix that are significantly less susceptible to antimicrobial agents than non-adherent, planktonic cells. Biofilm-based infections are, as a result, extremely difficult to cure. A wide range of molecular mechanisms contribute to the high degree of recalcitrance that is characteristic of biofilm communities. These mechanisms include, among others, interaction of antimicrobials with biofilm matrix components, reduced growth rates and the various actions of specific genetic determinants of antibiotic resistance and tolerance. Alone, each of these mechanisms only partially accounts for the increased antimicrobial recalcitrance observed in biofilms. Acting in concert, however, these defences help to ensure the survival of biofilm cells in the face of even the most aggressive antimicrobial treatment regimens. This review summarises both historical and recent scientific data in support of the known biofilm resistance and tolerance mechanisms. Additionally, suggestions for future work in the field are provided.

Optimized tetramer analysis reveals Ly49 promiscuity for MHC ligands

Murine Ly49 receptors, which are expressed mainly on NK and NKT cells, interact with MHC class I (MHC-I) molecules with varying specificity. Differing reports of Ly49/MHC binding affinities may be affected by multiple factors, including cis versus trans competition and species origin of the MHC-I L chain (β2-microglobulin). To determine the contribution of each of these factors, Ly49G, Ly49I, Ly49O, Ly49V, and Ly49Q receptors from the 129 mouse strain were expressed individually on human 293T cells or the mouse cell lines MHC-I-deficient C1498, H-2(b)-expressing MC57G, and H-2(k)-expressing L929. The capacity to bind to H-2D(b)- and H-2K(b)-soluble MHC-I tetramers containing either human or murine β2-microglobulin L chains was tested for all five Ly49 receptors in all four cell lines. We found that most of these five inhibitory Ly49 receptors show binding for one or both self-MHC-I molecules in soluble tetramer binding assays when three conditions are fulfilled: 1) lack of competing cis interactions, 2) tetramer L chain is of mouse origin, and 3) Ly49 is expressed in mouse and not human cell lines. Furthermore, Ly49Q, the single known MHC-I receptor on plasmacytoid dendritic cells, was shown to bind H-2D(b) in addition to H-2K(b) when the above conditions were met, suggesting that Ly49Q functions as a pan-MHC-Ia receptor on plasmacytoid dendritic cells. In this study, we have optimized the parameters for soluble tetramer binding analyses to enhance future Ly49 ligand identification and to better evaluate specific contributions by different Ly49/MHC-I pairs to NK cell education and function.

Temporal stability of the Learning Efficiency Test-II for adults

This study examined the temporal stability of the Learning Efficiency Test-II with 101 undergraduate students over a mean test-retest time interval of 19 days. Temporal stability estimates were .79 for the Visual Modality factor score, .75 for the Auditory Modality factor score, and .80 for the Global Memory factor score. A repeated measures analysis of variance for these three factor scores indicated no significant mean differences from Test 1 to Test 2. Slightly lower retest correlations were obtained for each of the 12 subtests, with correlations ranging from .44 to .70. The findings indicate that some subtests are reliable to assess the memory processing of adults over time and also highlight the stability over 19 days of memory processes for intact learners. Other studies with older groups of persons are needed to examine the stability of scores.

Gender and racial differences in mathematical performance

The authors examined gender and racial differences in mathematics performance among 5th- and 8th-grade students in the United States. Math performance was assessed by scores on the math-concepts and math-computation sections of the California Achievement Test (CTB/McGraw-Hill, 1986) given at the end of the previous year. There were no significant gender differences, but in both grades, the White students scored significantly higher than the Black students. The racial differences were more pronounced in the scores for concepts than in the scores for computation. Responses to a parent questionnaire showed significant relationships between parents' self-reported math anxiety, parents' most advanced math course, and parents' education level in relation to the child's math performance. Differences in these relationships suggest that, although parents' beliefs and attitudes about math influence their child's math performance, the relationship is complex and may vary with race.

College students' perception of facial expressions

95 college students were administered the Facial Expressions subtest of the Diagnostic Analysis of Nonverbal Accuracy to measure perception of nonverbal cues. Participants also completed the Nowicki-Strickland Locus of Control Scale and responded to a short questionnaire regarding their beliefs about their own ability to perceive nonverbal cues as well as how effective they felt others were in perceiving nonverbal cues. A significant correlation between locus of control and perception of adult facial expressions indicated those students with a more internal locus of control had higher scores on correct perception of adult facial expression. There was no significant correlation between locus of control and facial expressions of children. Sex differences were also found in perception of nonverbal cues. Female students scored higher in correctly perceiving facial expressions than the men. Participants also scored higher in correctly perceiving facial expressions of children than of adults.

The influence of gender on the ocular surface

PURPOSE

Dry eye is more prevalent among women than men. To examine whether gender influences the ocular surface, conjunctival goblet-cell density was monitored for a 30-day period. Changes in goblet-cell density are a sensitive marker for ocular surface disease.

METHODS

Six men and twelve women who were free from ocular surface disease were sampled by impression cytology on the inferior bulbar conjunctiva every other day for 30 days. Samples were analyzed for goblet-cell content. The mean age of the subjects was 24 years for the men and 25.4 years for the women. A minimum of 200 epithelial cells were scored per microscopic field examined.

RESULTS

There is a statistically significant difference in goblet-cell count between men and women over the 30-day test period. The mean goblet-cell count measured for men was 3.75% +/- 1.04%, while the mean count for women was 2.545% +/- 0.8%. When the data on women were replotted with reference to the menstrual cycle, the largest and longest depression of goblet-cell count occurs midcycle, around the time of ovulation. A significant difference in goblet-cell count was also noted when subjects using oral contraceptives (3.065% +/- 0.98%) are compared with those not using oral contraceptives (2.28% +/- 0.92%).

CONCLUSION

It appears there may be a reproductive hormonal influence on conjunctival goblet-cell count.

Synaptic effects of nitric oxide on enkephalinergic, GABAergic, and glutamatergic networks of the rat periaqueductal gray

Previous studies have shown that the injection of nitric oxide (NO) donating compounds into the dorsal periaqueductal gray region of the midbrain (PAG) decreases mean arterial pressure (MAP), while the injection of NO synthase (NOS) inhibitors increases MAP. In this study we used both in-vivo and in-vitro preparations and examined the effect of a NO donor and a NOS inhibitor on MAP, membrane properties, and synaptic activities in PAG neurons. We found that: (1) Injection of the NO donor hydroxylamine (HA) into the dorsal PAG decreased MAP, while the injection of the neuronal NOS (nNOS) inhibitor, 1-(2-trifluoromethylphenyl) imidazole (TRIM) increased MAP. These responses were consistent and site-specific. (2) HA-evoked hypotensive responses were mediated by PAG neuronal activity, because they were blocked by pre-injection with gamma-amino-butyric acid (GABA). (3) HA consistently increased the rate of observable synaptic events while TRIM consistently decreased the rate of observable synaptic events. (4) Bicuculline (BIC) and naloxone (NAL) blocked HA-evoked increases in the rate of observable inhibitory synaptic events. (5) Perfusion with sodium nitroprusside (SNP) and illumination with bright light consistently elevated rates of observable synaptic events, and SNP-evoked increases of excitatory synaptic events were blocked by pretreatment with glutamic acid antagonists. (6) PAG-medullary projecting neurons exhibited similar response patterns. The results of this study suggest that: (1) NO production within the PAG is a major component of PAG-mediated cardiovascular responses. (2) The effects of NO may be mediated in part by increased presynaptic vesicular release of glutamic acid, GABA, and enkephalin.

Reduced utilization of Man5GlcNAc2-P-P-lipid in a Lec9 mutant of Chinese hamster ovary cells: analysis of the steps in oligosaccharide-lipid assembly

Recently we reported that CHB11-1-3, a Chinese hamster ovary cell mutant defective in glycosylation of asparagine-linked proteins, is defective in the synthesis of dolichol [Quellhorst et al., 343:19-26, 1997: Arch Biochem Biophys]. CHB11-1-3 was found to be in the Lec9 complementation group, which synthesizes polyprenol rather than dolichol. In this paper, levels of various polyprenyl derivatives in CHB11-1-3 are compared to levels of the corresponding dolichyl derivatives in parental cells. CHB11-1-3 was found to maintain near normal levels of Man5GlcNAc2-P-P-polyprenol and mannosylphosphorylpolyprenol, despite reduced rates of synthesis, by utilizing those intermediates at a reduced rate. The Man5GlcNAc2 oligosaccharide attached to prenol in CHB11-1-3 cells and to dolichol in parental cells is the same structure, as determined by acetolysis. Man5GlcNAc2-P-P-polyprenol and Man5GlcNAc5-P-P-dolichol both appeared to be translocated efficiently in an in vitro reaction. Glycosylation of G protein was compared in vesicular stomatitus virus (VSV)-infected parent and mutant; although a portion of G protein was compared in vesicular stomatitus virus (VSV)-infected parent and mutant; although a portion of G protein was normally glycosylated in CHB11-1-3 cells, a large portion of G was underglycosylated, resulting in the addition of either one or no oligosaccharide to G. Addition of a single oligosaccharide occurred randomly rather than preferentially at one of the two sites.

The medial preoptic nucleus of the hypothalamus modulates activity of nitric oxide sensitive neurons in the midbrain periaqueductal gray

Stimulation of the medial preoptic nucleus of the hypothalamus (MPO) has been shown to produce decreases in mean arterial pressure (MAP) by a pathway involving the periaqueductal gray region of the midbrain (PAG). Previous studies have shown that the injection of nitric oxide (NO) donating compounds into the dorsal PAG also decreases MAP, while the injection of nitric oxide synthase (NOS) inhibitors increases MAP. Collectively these studies suggest that the MPO elicited hypotensive response may involve NO production in PAG neurons. In this study, we investigated this hypothesis. We found that: (1) Bilateral injection of the NOS inhibitor 7-nitro indazole (7-NI) into the dorsolateral PAG cell columns produced elevations in MAP in a highly consistent and site specific fashion. (2) Microinjection of 7-NI in quantities that were too low to directly influence MAP blocked the MPO evoked hypotensive response in 9/11 cases. (3) While 41% of dorsal PAG neurons had baseline firing rates that were sensitive to 7-NI, 69% of PAG neuronal responses to MPO stimulation were blocked by 7-NI. (4) Inhibitory responses that were not blocked by 7-NI had significantly shorter latencies to onset in the presence of 7-NI. (5) PAG neurons that projected to the medulla exhibited similar electrophysiologic response patterns. Our results suggest the following: (1) The dorsolateral PAG contains a NO producing hypotensive network. (2) The MPO elicited hypotensive response may utilize this network. (3) Stimulation of the MPO elicits NO dependent responses from PAG neurons, some of which do project to medullary-cardiovascular control centers.

Synthesis of dolichol in a polyprenol reductase mutant is restored by elevation of cis-prenyl transferase activity

CHB11-1-3 is a glycosylation mutant of Chinese hamster ovary (CHO) cells, isolated by screening mutagenized cells for those with decreased intracellular lysosomal enzyme activity [C. W. Hall et al. (1986) Mol. Cell. Biochem. 72, 35-45]. CHB11-1-3 synthesizes the lipid polyprenol, the metabolic precursor of dolichol, rather than dolichol, indicating a defect in polyprenol reductase. This defect was demonstrated previously in Lec9 CHO mutants, and cell fusion experiments confirmed that CHB11-1-3 is a member of this complementation group. A revertant of CHB11-1-3, CHBREV, isolated for its ability to grow at 39 degrees C, synthesizes dolichol at near-normal levels. CHBREV is probably a second-site revertant, because it synthesizes three to four times as much polyprenol as CHB11-1-3 and exhibits a similar elevation in the specific activity of cis-prenyl transferase. This higher activity appears to reflect an increase in enzyme molecules rather than the presence of an activator or absence of an inhibitor. These results suggest that CHB11-1-3 is a "K(m)" mutant, because synthesis of higher amounts of the substrate of polyprenol reductase obviates the defect.

Teenagers' knowledge about prenatal exposure to cocaine

The current study indicated limited knowledge among 124 teenagers about prenatal exposure to cocaine. Given the widespread problem of substance abuse among teenagers as well as high incidence of teenage pregnancies, there is a need to make this information more readily available.

A comparison of the performance of cognitively disabled children on the WISC-R and WISC-III

This study compared differences in performance on the WISC-III and on the WISC-R. Sixty-one students with learning impairments, due for reevaluation of their special education placement, were administered the WISC-III as part of a psychological assessment battery. Results indicate a mean difference between WISC-R and WISC-III FSIQ of 7.95 points, which is similar to WISC/WISC-R comparisons. Substantial differences that averaged 9.21 points were found between WISC-R and WISC-III PIQ means. These findings suggest that for a special education sample an average decrease of at least 8 points can be expected on the WISC-III Full Scale IQ. Caution should be exercised when one is considering changes in educational classification or interpreting qualitative differences in performance on WISC-III scores compared with WISC-R scores.

Adjustment issues with adult children of alcoholics

The current study assessed locus of control, general level of life satisfaction, and self-reported grade-point averages among adults who had experienced either alcoholism within the family of origin, traumatic life events other than alcoholism, or who indicated neither problem during their childhood. Results indicated that both the adult children of alcoholics (ACOA) and traumatic experience (TE) groups had lower life satisfaction scores than the control group. Significantly lower levels of locus of control also were found for the ACOA group in comparison to the control group. There were no significant differences among the three groups based on self-reported GPAs. Results of the current study support the concept that family dysfunction during childhood can influence negatively later life experiences and adjustment.

Learning styles of LD and NLD ADHD children

Attention Deficit Hyperactive Disorder (ADHD) children (N = 26) with a learning disability (LD) and without (NLD) were compared on measures of information processing using the Learning Efficiency Test (LET). Method of presentation (visual vs. auditory), order of recall (ordered vs. non-ordered), and memory processes (immediate, short-term, and long-term) were assessed. While both groups showed more difficulty with short-term and long-term memory processes than with immediate memory processes, the ADHD-LD subjects demonstrated more difficulty processing information effectively. Ordered recall was significantly more difficult for both short-term and long-term memory processes than was unordered recall. While both groups demonstrated difficulty with auditory ordered recall under short-term and long-term conditions, the ADHD-LD subjects lost the most information under auditory conditions.

Effects of two treatment techniques on delay and vigilance tasks with attention deficit hyperactive disorder (ADHD) children

In this study, we examined the effects of two treatment techniques under on-medication and off-medication conditions on the hyperactive behavior patterns of children. Three groups of subjects were compared: a control group, a behavior modification group, and a cognitive training group. The Gordon Diagnostic System (Gordon, McClure, & Post, 1986) was used to assess the subjects at the initial screening, during treatment without medication, and during treatment with medication. The two medication conditions were counterbalanced during the second and third testing sessions. Results showed that when the cognitive intervention was combined with medication, there was a significant improvement in the subjects' ability to delay impulsive responding. However, no significant effects were seen for sustained vigilance for either the behavioral or cognitive groups. Parents rated children in the cognitive group significantly higher than those in the control group.

Recovery of function in Chinese hamster ovary cell mutants with temperature-sensitive defects in vacuolar acidification

After 4 h at 41 degrees C, B3853 and M311, temperature-sensitive Chinese hamster ovary cell End1 and End2 mutants, respectively, are pleiotropically defective in endocytosis and trans-Golgi network-associated activities (Roff, C. F., R. Fuchs, I. Mellman, and A. R. Robbins. 1986. J. Cell Biol. 103:2283-2297). We have measured recovery of function after return to the permissive temperature. Based on return of normal transferrin-mediated Fe uptake and sensitivity to diphtheria toxin both mutants had restored endosomal function at 10 h; based on delivery of endocytosed lysosomal enzymes to lysosomes and normal sensitivity to modeccin both had functional late endocytic organelles at 10-12 h; and based on retention of newly synthesized lysosomal enzymes and sialylation of secreted glycoproteins both had functional trans-Golgi network at 6 h. At 10 h, M311 had recovered almost all of its ability to endocytose lysosomal enzymes; B3853 required 30 h to recover fully its ability to endocytose lysosomal enzymes. Slow recovery of mannose 6-phosphate-dependent uptake in B3853 reflected altered trafficking of cation-independent mannose 6-phosphate receptors. Although B3853 had normal amounts of receptor at 6-8 h, it had greatly diminished amounts of receptor at the cell surface. Altered trafficking was also suggested by the finding that B3853 rapidly degraded receptor that had been present before the shift to the nonpermissive temperature.

Field independence and simultaneous processing in preschool children

The present study examined the relations between field independence and simultaneous processing of preschool children as measured by the Preschool Embedded Figures Test (PEFT) and subtests from the Kaufman Assessment Battery for Children (K-ABC), respectively. Data partially supported the assumption that field-independent children would perform significantly better on simultaneous processing tasks in general. Significant age and sex differences on field-independence/field-dependence and simultaneous-processing abilities were found among the embedded figures task and selected portions of the K-ABC. Analysis of embedded figures further indicated age differences, but no significant sex differences.

Regional brain [Met]-enkephalin in alcohol-preferring and non-alcohol-preferring inbred strains of mice

Scrutiny of the data from these studies reveals that the C58/J alcohol-preferring mice have significantly lower baseline methionine-enkephalin levels in both the corpus striatum and hypothalamus compared to C3H/CHRGL/2 non-alcohol-preferring mice. In other brain regions in these two strains, specifically, pituitary, amygdala, midbrain, and hippocampus, analysis of methionine-enkephalin levels did not show any significant differences. This suggests that the hypothalamus may indeed be a specific locus involved in the regulation of alcohol intake, via the molecular interaction between neuroamines, opioid peptides, as they are influenced by genetics and environment.

Preliminary characterization of a Chinese hamster ovary cell glycosylation mutant isolated by screening for low intracellular lysosomal enzyme activity

A novel screening procedure was developed for isolating Chinese hamster ovary cell mutants altered in the early steps of the biosynthesis of asparagine-linked glycoproteins. This procedure identifies cells with low intracellular levels of two lysosomal hydrolases, beta-glucuronidase and alpha-iduronidase. One mutant cell line isolated in this way, CHB 11-1-3, has low intracellular levels of seven lysosomal enzymes as compared to wild-type cells. Although CHB 11-1-3 synthesizes mannosylphosphoryldolichol and [Man]5[NAcGlcNH2]2-P-P-lipid, it fails to utilize these lipid intermediates to make normal amounts of [Glc]3[Man]9[NAcGlcNH2]2-P-P-lipid. As a consequence of this glycosylation defect, this mutant transfers oligosaccharides of a different structure than wild type to the lysosomal enzyme beta-hexosaminidase. In addition, it underglycosylates its proteins.

Supersensitivity to norepinephrine induced by prenatal exposure to ethanol

Pregnant random bred mice were treated with ethanol (ETOH) (0.33 g/kg) for 1 or 2 days prior to parturition. When compared to saline controls, ETOH-treated adult males had vasa deferentia that were supersensitive to norepinephrine (NE). Tissues from mice prenatally treated for 1 day with ETOH showed a decreased response to electrical stimulation whereas vas deferens obtained from 2-day-treated ethanol showed no significant difference in the response compared to that of controls. These findings indicate that prenatal exposure to ETOH can influence the subsequent sensitivity of the vas deferens to adrenergic stimulation. These changes appear to reflect effects of ETOH during critical periods.

Some factors that influence prolonged interfacial continuity

Bringing a percutaneous implant through the integument with the intentions of leaving it as a functional device for prolonged periods of time has not yet become a reality. If we are ever to achieve prolonged uninfected implants, attention must be directed toward a variety of failure mechanisms. Some of these mechanisms have defied our scrutiny, and our awareness of others are poorly understood. Some of the causes for failure of a percutaneous implant are the forces, either extrinsic or intrinsic, that cause shearing and tearing at the skin-implant interface. Extrinsic forces are defined as those forces applied either to the skin or the implant by the external environment. Intrinsic forces are those that have to do directly or indirectly with the body's growth and cell maturation, such as the retraction of maturing scar tissue and the surface migration of squamous epithelium. An intact skin-implant interface is important to attain in order to close the portal which might allow microbial invasion. The integument must remain intact, since a suppurative wound makes the implant's removal mandatory.

Canine alpha-L-iduronidase deficiency. A model of mucopolysaccharidosis I

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Administration of iduronate sulfatase by plasma exchange to patients with the Hunter syndrome: a clinical study

The Hunter syndrome (MPS II) is the only mucopolysaccharidosis in which there is appreciable activity of the deficient enzyme in normal plasma. We performed enzyme-replacement treatment by plasma exchange in five Hunter syndrome children. Carefully monitoring the cardiovascular status, we administered monthly single plasma volume exchanges for a 3 to 8 mo period. The results indicate a substantial gain of enzyme activity, persisting with a t50% = 19 +/- 5 hr. The maximal level and persistence of increased enzyme activity did not change after repeated exchanges, suggesting that immune responses were not elicited. Despite this, no demonstrable clinical benefit was apparent when the study group was compared with an age-matched control group of Hunter syndrome patients.

Sleep attacks--apparent relationship to atlantoaxial dislocation

Sleep attacks, while being characteristic of narcolepsy, have been reported in several metabolic and central nervous system disorders--most of which are refractory to treatment. We have recently treated a 47-year-old man with disabling sleep attacks who was found to have atlantoaxial dislocation. Despite narrowing of the sagittal cervical canal diameter to 12 mm (behind the dens), symptoms of spinal cord compression were mild and intermittent, while signs were absent. Posterior fusion of the C-1 and C-2 vertebrae resulted in relief of symptoms. We suggest that this sleep disorder was a function of impaired efferent control of respiration.

The defect in Hurler and Hunter syndromes. II. Deficiency of specific factors involved in mucopolysaccharide degradation

Cultured fibroblasts, derived from patients with the Hurler and Hunter syndromes, show defective degradation of sulfated mucopolysaccharide. The aberrant metabolism of Hurler cells can be corrected by secretions of fibroblasts of genotype other than Hurler, and similarly, the defect of Hunter cells can be corrected by secretions of fibroblasts of genotype other than Hunter. The active factors in these secretions, which are heat labile and associated with macromolecules, accelerate the degradation of mucopolysaccharide.

Hurler and Hunter syndromes: mutual correction of the defect in cultured fibroblasts

The biochemical defect of cultuired skin fibroblasts from Hurler or Hunter patients (faulty degradation of sulfated mucopolysaccharide, resulting in excessive intracellular accumulation) may be corrected if cells of these two genotypes are mixed with each other or with normal cells. The effect is mediated by substances released into the medium.

Healing of Pseudointimas in Velour-lined, Impermeable Arterial Prostheses

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