Validity and reliability of the MTI photoscreener

OBJECTIVES

The prevalence and necessity for early detection of vision problems illustrate the need for improved methods of vision screening in preschool children. This study assessed the validity and reliability of a new device, the MTI photoscreener in a cross-sectional field study.

METHODS

An appropriate sample size (> 140) was calculated and recruited for the study. All children (N = 161) in a migrant workers summer education program were screened with the MTI Photoscreener. Simultaneously and in a masked design, disease status was determined by the Modified Clinic Technique, a well established method for diagnosing the conditions which the MTI screener was designed to detect.

RESULTS

Validity measures revealed a sensitivity of 54%, specificity of 87%, phi coefficient of 0.40, and positive predictive value of 52%. Repeatability was assessed by the kappa coefficient, by a test for effect modification by examiner, and by comparison of sensitivity and specificity across 12 masked examiners. The kappa coefficient was 0.38. A test for effect modification suggested that differences existed among the examiners. Variability of sensitivity was high, but variability of specificity was low.

CONCLUSIONS

Methods for vision screening in preschool children are limited. The MTI Photoscreener is an easy and efficient method, but the validity and reliability is a concern. Comparison of our results with other studies suggests future potential for this instrument provided protocols are refined and further field studies reveal efficacy.

Response to oral and intravenous azithromycin in a patient with toxoplasma encephalitis and AIDS

We present a patient with AIDS and toxoplasma encephalitis who was unable to tolerate established therapy with sulphadiazine or clindamycin but responded to oral azithromycin and pyrimethamine. The patient was maintained on oral azithromycin but subsequently relapsed after 8 months. The recurrence was successfully treated with intravenous azithromycin. The case illustrates that azithromycin can be used to treat patients with toxoplasma encephalitis who are unable to tolerate or fail to respond to other therapeutic agents. Failure of oral azithromycin may be due to inadequate tissue concentrations and patients may further benefit from intravenous administration.

beta-Cyclodextrin: 52-week toxicity studies in the rat and dog

A 52-wk toxicity study by dietary administration was performed in Sprague-Dawley rats and in pure-bred beagle dogs with beta-cyclodextrin, a starch derivative that acts as a molecular inclusion agent. Doses of 0 (control), 12,500, 25,000 and 50,000 ppm were selected for the rat study, and 0 (control), 6200, 12,500 and 50,000 ppm were selected for the dog study. The liver and kidney were identified at the histopathological examination as target organs for toxicity in the rat at doses of 50,000 and 25,000 ppm, with the hepatic changes associated with increased plasma liver enzyme and reduced plasma triglyceride concentrations. In the dog study, there was no pathological evidence of systemic toxicity, although there were minor changes in urinalysis and biochemical parameters and a slightly higher incidence of liquid faeces. These changes were considered to be of no toxicological importance. The results in these studies, therefore, indicate that the non-toxic effect level was 12,500 ppm in the rat (equivalent to 654 or 864 mg/kg/day for males or females, respectively) and 50,000 ppm in the dog (equivalent to 1831 or 1967 mg/kg/day for males or females, respectively).

Hyaluronic acid (hyaluronan) in experimental osteoarthritis

We studied the effects of intraarticular (ia) administration of hyaluronic acid (HA) (Mw approximately 9 x 10(5)) (Artz) on cartilage integrity and release into synovial fluid (SF) of keratan sulfate peptides (KS-pep) in an ovine model of early osteoarthritis (OA) induced by meniscectomy. Five consecutive weekly injections of HA (2 ml, 10 mg/ml) or saline (2 ml) were initiated 16 weeks after meniscectomy, and animals were sacrificed 5 weeks after the last injection. SF was sampled 8, 16, 23, and 26 weeks postoperation. In the saline injected animals KS-pep levels increased progressively in SF, relative to nonoperated controls (p < 0.05). KS-pep levels in SF of the HA treated group also increased, but were not statistically different from controls. Using a modified Mankin histological scoring system, cartilage at necropsy of HA injected joints showed less damage than similar regions of saline treated animals. A new mechanism for the protective effects of HA on cartilage is proposed.

The effects of intraarticular hyaluronan on cartilage and subchondral bone changes in an ovine model of early osteoarthritis

OBJECTIVE

Intraarticular (ia) hyaluronan (HA) is reported to provide symptomatic relief in osteoarthritis (OA); however, there is limited information on the effects that this treatment may have on joint articular cartilage or subchondral bone. Our objective was to address this issue using an ovine model of early OA.

METHODS

Unilateral medial meniscectomy was performed in 10 adult merino sheep, and 5 unoperated animals were used as controls (UOC). Sixteen weeks postmeniscectomy, joints of 5 operated animals were injected with 2 ml of HA (Artz, 10 mg/ml, M(r) = 0.9 x 10(6) Da) ia while the remaining 5 operated animals received 2 ml of sterile saline ia. This protocol was continued for a further 4 weeks. All animals were sacrificed 5 weeks after the last injection; however 3 weeks before sacrifice they were given tetracycline (20 mg/kg intravenously) weekly. Bone slabs, including articular cartilage, were cut from the medial tibial plateaux and femoral condyles, processed for histology, histomorphometry and fluorescence microscopy to assess articular cartilage and subchondral bone pathology.

RESULTS

Meniscectomy and saline treatment increased osteoid volume and surfaces as well as increased the extent of tetracycline labelling of the subchondral bone relative to UOC. The articular cartilage also exhibited a significantly higher modified Mankin's score than UOC. In the HA injected group the aforementioned articular cartilage and subchondral bone changes were modified such that the observed variables were indistinguishable from UOC.

CONCLUSION

Using this animal model intraarticular HA appeared to limit the development of articular cartilage and subchondral bone changes characteristic of early OA.

Effects of intraarticular hyaluronan on matrix changes induced in the lateral meniscus by total medial meniscectomy and exercise

Total medial meniscectomy was performed in 12 adult merino sheep. Immediately after surgery, 8 animals received high-molecular-weight hyaluronan (HA) (1 mL, 10 mg/mL) and 4 were given sterile saline (1 mL) intraarticularly. Injections were given for 5 more weeks. In week 3 an exercise program, consisting of walking 24 km/wk, was initiated. This program was continued until the animals were killed at week 26 postmeniscectomy. At necropsy the lateral menisci were removed and divided into three concentric zones--inner, middle, and outer. Powdered aliquots of tissues from each zone were analyzed for collagen and hexuronate contents using colormetric methods. The glycosaminoglycans (GAGs)--chondroitin-O-sulfate (C-O-S), chondroitin-4-sulfate (C-4-S), chondroitin-6-sulfate (C-6-S), and dermatan sulfate (DS)--were determined using a high-performance liquid chromatography method. The lateral menisci from the joints of animals injected with HA showed higher hexuronate and GAG levels than those of controls. This increase was mainly due to C-6-S, which had highest levels in the inner and middle meniscal zones. In addition, dermatan sulfate levels increased significantly in the middle and outer zones of the lateral menisci compared with the same zones of the meniscus from the saline-treated group. Collagen and C-O-S levels were not statistically different from those of controls. These data suggest that intraarticular administration of high-molecular-weight HA immediately after open total medial meniscectomy may help preserve the proteoglycans in the lateral meniscus remaining in the joint.

The effects of intraarticular administration of hyaluronan in a model of early osteoarthritis in sheep. II. Cartilage composition and proteoglycan metabolism

A model of early osteoarthritis (OA) induced in ovine joints by medial meniscectomy was used to study the effects of two hyaluronan (HA) preparations (AHA and DHA) on cartilage composition and proteoglycan (PG) metabolism. DHA was an HA preparation with an average molecular weight (MW) of approximately 2.0 x 10(6) d, and AHA had an MW of approximately 8.0 x 10(5) d. Both preparations were administered intraarticularly once a week for 5 weeks starting 16 weeks after meniscectomy, and animals (n = 5) were killed 5 weeks after the last injection. Meniscectomized, saline-injected (n = 5) and nonoperated (n = 5) animals were used for controls. At necropsy, 3-mm-diameter full-depth cartilage plugs were sampled under sterile conditions from specific locations on the medial and lateral femoral condyles, tibial plateaus, patella, and trochlear groove. The cartilage plugs were cultured in Hams-F12 medium supplemented with 10% fetal calf serum for 24 hours, then for a further 48 hours in the presence of H2(35)SO4 to determine the biosynthesis of PGs. The percentage of 35S-PGs and sulfated glycosaminoglycans released into the media was also ascertained. The cartilage adjacent to the plugs was analyzed for collagen and proteoglycan content and differential extractability with guanidine hydrochloride (GuHCl) solutions. The extractability of PGs with 0.4 mol/L GuHCl (nondissociative conditions) was lower from the medial femoral cartilages of the DHA-treated group than from the corresponding saline-treated group. In contrast, the release of 35S-PGs from the tibial cartilages of the DHA-treated animals was higher than in the saline-treated group. The biosynthesis of 35S-PGs, determined in vitro, for cartilage derived from the medial compartment was generally lower than for the lateral regions of the meniscectomized joints. The biosynthetic activity was further reduced in joints injected with the two HA preparations, but DHA reduced 35SO4 incorporation into PGs more than AHA. It was concluded that reduced biosynthesis of 35S-PGs and secretion into media was a consequence of increased loading of joints in the HA-treated animals rather than a direct effect of these preparations on chondrocyte metabolism.

The effects of intraarticular administration of hyaluronan in a model of early osteoarthritis in sheep. I. Gait analysis and radiological and morphological studies

Using a model of early osteoarthritis (OA) induced in ovine joints by medial meniscectomy, the intraarticular effects of two hyaluronic acid (HA) preparations (AHA and DHA) were investigated. DHA was an HA preparation with an average molecular weight (MW) of approximately 2.0 x 10(6) d, and AHA had a MW of approximately 8 x 10(5) d. Animals (n = 5) were injected intraarticularly with 1 mL (10 mg/mL) of either HA preparation once a week for 5 weeks beginning 16 weeks after initiation of arthropathy. Meniscectomized, saline (1.0 mL)-injected animals (n = 5) and nonoperated sheep (n = 5) were used for controls. Force-plate analysis of gait and radiographic changes in joints were evaluated in these groups before and after intraarticular treatment. At necropsy, cartilage gross morphology, osteophyte development, and cartilage histopathology were examined. Meniscectomized joints were characterized by erosions and fissuring of cartilage of the medial compartment with areas of decreased matrix staining for proteoglycans. Osteophytes were present at the medial joint margins. Saline-treated meniscectomized animals showed reduced loading of the operated limb using the force plate. Force-plate analysis of walking animals before and after treatment with either AHA or DHA indicated some normalization of joint loading. However, osteophyte scores for meniscectomized joints injected with AHA and DHA were higher after treatment than those of the corresponding saline-treated group. Although the gross cartilage damage was lower than in saline-treated controls for both the HA-treated groups, the histological scores did not support this conclusion. Indeed, the tibial score for the DHA group was higher than for the AHA group (P < .05). These studies confirmed previous reports that meniscectomy of sheep stifle (knee) joints resulted in matrix changes similar to those described for early OA in humans. Both HA preparations appeared to improve gait, suggesting decreased lameness. Increased joint loading associated with gait improvement may account for the higher osteophyte scores in the treated groups. However, cartilage damage with DHA was found to be higher than when the lower-MW HA preparation (AHA) was used.

The metabolic response of articular cartilage to abnormal mechanical loading induced by medial or lateral meniscectomy

The effects of medial versus lateral meniscectomy on articular cartilage (AC) of adult sheep was investigated. In vitro incorporation of 35S into proteoglycans (PGs) and their release into media was used to assess cartilage metabolism. Lateral meniscectomy produced higher loss of PGs from AC and lower 35S-PG biosynthesis than for AC from medial meniscectomized joints. These findings were consistent with the proposed role of the lateral meniscus in joint mechanics.

Animal models of early osteoarthritis: their use for the evaluation of potential chondroprotective agents

Medial meniscectomy was undertaken in adult merino sheep and after 16 weeks exercise each group was administered five weekly intra-articular injections of saline, pentosan polysulphate (PPS), hyaluronic acid (HA) or a combination of PPS + HA. Gait analysis and x-rays were undertaken before and after drug treatment. At sacrifice (26 weeks), joints were examined for gross pathological and histochemical changes. Only the PPS-treated group showed an improvement in gait, with low radiological and histology scores. The HA-treated group showed similar but less significant changes to these parameters.

Interaction of Haemophilus influenzae with mucus, cilia, and respiratory epithelium

One nontypeable laboratory strain and five nontypeable clinical isolates of Haemophilus influenzae from sputum were investigated. Bacteria replicated from 10(4) to 10(8) cfu/ml over 24 h in an organ culture of human respiratory mucosa with only the intact mucosal surface exposed. By transmission electron microscopy, bacteria were not seen in association with normal respiratory epithelium, even after incubation for 24 h. H. influenzae infection caused patchy and occasionally confluent damage to epithelium, and the bacteria associated only with structurally damaged cells. Scanning electron microscopy revealed increased mucus, and slowed ciliary beat frequency was measured by photometry. Fimbriation of H. influenzae increased buccal cell adherence but did not facilitate association with normal or damaged respiratory epithelium or increase epithelial damage, indicating that adhesins other than fimbriae are present. Interactions with mucus, cilia, and epithelium are likely to be important in the pathogenesis of H. influenzae respiratory infections.

The interaction of Streptococcus pneumoniae with intact human respiratory mucosa in vitro

The interaction of Streptococcus pneumoniae with human ciliated upper respiratory mucosa was studied in an agar-embedded organ culture of nasal turbinate tissue, which only exposed the intact epithelial surface and its secretion. The ciliary beat frequency, measured along the edge of the organ culture, was slowed by 13% in the presence of S. pneumoniae after 16 h (p less than 0.05) compared with the control, and by 24% after 24 h (p less than 0.01). Light microscopy showed bacteria in a thickened gelatinous layer, which obscured the surface of the organ culture. Transmission and scanning electron microscopy confirmed the association of bacteria with the gelatinous layer above an epithelial surface which showed only minor changes compared to uninfected control organ cultures. Contact between bacteria and normal or damaged epithelial cells was not seen. S. pneumoniae in organ culture developed projections from their surface, which were not present after broth culture. S. pneumoniae interactions with epithelial-derived secretions, the formation of a thickened gelatinous layer, and the effects of bacterial toxins on ciliary motility, may be important during colonization of the respiratory tract.

The interaction of Streptococcus pneumoniae with intact human respiratory mucosa in vitro

The interaction of Streptococcus pneumoniae with human ciliated upper respiratory mucosa was studied in an agar-embedded organ culture of nasal turbinate tissue, which only exposed the intact epithelial surface and its secretion. The ciliary beat frequency, measured along the edge of the organ culture, was slowed by 13% in the presence of S. pneumoniae after 16 h (p less than 0.05) compared with the control, and by 24% after 24 h (p less than 0.01). Light microscopy showed bacteria in a thickened gelatinous layer, which obscured the surface of the organ culture. Transmission and scanning electron microscopy confirmed the association of bacteria with the gelatinous layer above an epithelial surface which showed only minor changes compared to uninfected control organ cultures. Contact between bacteria and normal or damaged epithelial cells was not seen. S. pneumoniae in organ culture developed projections from their surface, which were not present after broth culture. S. pneumoniae interactions with epithelial-derived secretions, the formation of a thickened gelatinous layer, and the effects of bacterial toxins on ciliary motility, may be important during colonization of the respiratory tract.

Evidence for intestinal release of absorbed selenium in a form with high hepatic extraction

Selenium is readily absorbed from the gastrointestinal tract and utilized for synthesis of selenoproteins. Roles of intestine, liver, and selenoprotein P in this process were evaluated. Rats were given 75Se-selenite by stomach tube, and distribution of 75Se was followed for 3 h. A high portal vein plasma-to-hepatic vein plasma ratio of 75Se 15 min after 75Se administration and earlier uptake by liver than by other tissues indicated avid hepatic extraction of absorbed selenium from portal vein blood. The results of gel filtration of plasma taken 15 min after 75Se administration suggested that the 75Se was in the form of small molecules with some affinity for protein. Immunoprecipitation studies using plasma indicated that 75Se began to appear in selenoprotein P between 15 and 30 min after intragastric administration. To evaluate the role of the liver in the fate of absorbed selenium, rats with portacaval shunts, in which absorbed selenium bypasses the liver, were compared with sham-operated rats. After intragastric administration of selenium, uptake by the liver and incorporation into selenoprotein P were diminished in rats with portacaval shunts but kidney uptake and urinary excretion were increased. This suggests that hepatic extraction of absorbed selenium from portal vein blood decreases its entrance into the systemic circulation. The results of this study indicate that intestine releases absorbed selenium into portal blood in a small-molecule form, designated A-Se, which is highly extracted by the liver. The liver takes up A-Se better than other tissues because of a high extraction capacity and the fact that it is the first organ through which the blood from the intestine passes.

Response of rat selenoprotein P to selenium administration and fate of its selenium

Selenoprotein P is a glycoprotein that contains greater than 60% of the selenium in rat plasma. Physiological experiments were undertaken to gain insight into selenoprotein P function. Selenium-deficient rats were injected with doses of selenium ranging from 25 to 200 micrograms/kg, and the appearance of selenoprotein P was compared with the appearance of glutathione peroxidase activity in plasma and in liver. Selenoprotein P concentration increased to 35% of control by 6 h, whereas glutathione peroxidase activity increased minimally or not at all. Moreover, in rats given 100 and 200 micrograms selenium/kg, selenoprotein P reached 75% of its concentration in control rats at 24 h, whereas glutathione peroxidase activity reached only 6% of control. Cycloheximide pretreatment blocked the appearance of selenoprotein P in response to selenium injection. Male and female rats had similar concentrations of selenoprotein P. Partially purified selenoprotein P and plasma glutathione peroxidase labeled with 75Se were administered intravenously to selenium-deficient and control rats. 75Se given as selenoprotein P disappeared more rapidly from plasma than did 75Se given as glutathione peroxidase. Selenium deficiency did not significantly affect 75Se disappearance from plasma. At 2 h, brain, but not other tissues, took up more 75Se in selenium-deficient rats than in control rats when 75Se was given as selenoprotein P. This suggests that brain has a specific uptake mechanism for selenium given in the form of selenoprotein P. These results demonstrate that several physiological properties distinguish selenoprotein P from glutathione peroxidase. However, they do not clearly indicate its function.

The cDNA for rat selenoprotein P contains 10 TGA codons in the open reading frame

Selenoprotein P is a plasma protein recently purified and characterized as containing 7.5 +/- 1.0 selenium atoms/molecule as selenocysteine. In rats maintained on a defined diet containing nutritionally adequate amounts of selenate as the sole selenium source, over half the selenium in plasma is accounted for by selenoprotein P. Its cDNA has been cloned from a rat liver library and sequenced. The sequence is highly unusual, containing 10 TGA codons in its open reading frame prior to the TAA termination codon. TGA designates selenocysteine in other selenoproteins, and limited peptide sequencing that included the amino acids encoded by two of the TGA codons verified that they correspond to selenocysteine. The deduced 366-amino acid sequence is histidine- and cysteine-rich and contains 9 of its selenocysteines in the terminal 122 amino acids. Comparison of the deduced amino acid sequence of selenoprotein P with those of other selenoprotein reveals no significant similarities. Selenoprotein P represents a new class of selenoproteins and is the first protein described with more than 1 selenocysteine in a single polypeptide chain. The primary structure of selenoprotein P suggests that it might be responsible for some of the antioxidant properties of selenium.

Recent advances in animal models for evaluating chondroprotective drugs

While a variety of animal models have been described to evaluate the effects of antiarthritic and chondroprotective drugs on cartilage metabolism, most cannot be said to truly reproduce the temporal changes that occur in human osteoarthritis (OA). Total meniscectomy is a common orthopedic procedure in humans and frequently leads to OA in later years. We investigated the effects of unilateral medial meniscectomy in sheep knee joints subjected to moderate regular exercise. Morphological and biochemical studies of joint cartilage after 6 months revealed slowly progressive changes similar to those seen in early OA, characterized by cartilage fibrillation, chondrocyte hypertrophy, matrix proliferation and marginal osteophyte formation. The proteoglycans synthesized contained more chondroitin-4-sulphate than chondroitin-6-sulfate.

Pneumocystis carinii: A review of an important opportunistic pathogen in AIDS

Since the first report of human infection with Pneumocystis carinii in 1942, cases of pneumonia due to this opportunistic pathogen have become increasingly common. Animal studies and clinical observations show that a significant depletion or dysfunction of T helper lymphocytes predisposes to clinical disease. Individuals with damaged T helper cells secondary to malignancies (eg, Hodgkin's lymphoma), drugs (eg, cyclosporine, steroids), or certain infections (eg, human immunodeficiency virus) are at particular risk. Serological studies suggest that disease is most often secondary to the reactivation of an asymptomatic infection, usually acquired during childhood. Increasing shortness of breath, a nonproductive cough and hypoxia often preceded by several weeks of lethargy, fever and weight loss are the classical features of P carinii pneumonia in acquired immune deficiency syndrome. Bronchoalveolar lavage is usually the optimal diagnostic test. Immunofluorescent staining on liquified sputum induced by nebulized saline appears to be a promising and noninvasive test. Early empiric therapy with trimethoprim-sulphamethoxazole (trimethoprim 5 mg-sulphamethoxazole 25 mg/kg/day every 6 h) or intravenous pentamidine (4 mg/kg/day) for 21 days is usually effective, but infection is not eradicated, and clinical disease is likely to recur. Prophylaxis using aerosolized pentamidine reduces the risk of pulmonary disease but can predispose to extrapulmonary infection. Improved in vitro and in vivo models of human pneumocystis infection would significantly increase understanding of the molecular biology of the organism, the pathogenesis of disease, and the optimal therapeutic regimens.