Continuous ambient lighting and eye growth in primates.

PURPOSE: To determine the effect of continuous light exposure on ocular growth and emmetropization in infant monkeys. METHODS: Nine infant rhesus monkeys were reared with the normal vivarium lights on continuously. The 24-hour light cycle was initiated between 1 and 4 weeks of age and maintained for 6 months. The ocular effects of continuous light were assessed by cycloplegic retinoscopy, keratometry, and A-scan ultrasonography. Longitudinal control data were obtained from 23 normal infants that were reared with an illumination cycle that included defined light and dark phases (either 12-hour light:12-hour dark or 8.5-hour light:15.5 hour dark). RESULTS: In contrast to previous studies involving light-reared chickens, no monkeys exhibited exaggerated ocular growth. There were no significant differences between treated and control monkeys in corneal radius, overall eye size, or the axial dimensions of individual ocular components. At the end of the treatment period, eight of the nine experimental monkeys also exhibited the moderate hyperopic errors (range, +1.5 to +3.4 D) that are typically found in normal animals. Aspects of emmetropization were, however, unusual for three monkeys. One monkey manifested a -0.50 D myopic error that was associated with an abnormally steep cornea but had normal axial lengths. Two additional monkeys developed persistent axial anisometropias. CONCLUSIONS: In infant primates constant light exposure does not promote the constellation of ocular changes (in particular corneal flattening, a decrease in anterior chamber depth, and an increase in vitreous chamber depth) that has been observed in light-reared chickens. The slight variations from the expected developmental sequence observed in three infants may reflect individual differences. However, it is also possible that aspects of the emmetropization process may not operate as effectively under constant light as they do under an ordinary light/dark cycle.

The effect of withdrawal of drugs treating intermittent claudication.

BACKGROUND: Pharmacologic treatment for intermittent claudication is a management option. This study evaluated the effect of withdrawal of drug therapies, cilostazol and pentoxifylline, on the walking ability of peripheral artery disease patients. METHODS: Single-blind placebo crossover from a randomized, double-blind trial; 45 claudication patients received either cilostazol 100 mg orally twice daily (n = 16), pentoxifylline 400 mg orally three times daily (n = 13), or placebo (n = 16) for 24 weeks. After 24 weeks of double-blind therapy, treatment for all groups was placebo only, and follow-up continued through week 30. Treatment efficacy was established with treadmill testing. RESULTS: Profile analysis demonstrated a highly significant loss of treatment benefit after crossover (P = 0.001) for cilostazol-treated patients, but no significant change after crossover was observed with pentoxifylline. CONCLUSIONS: Drug withdrawal worsened the walking of claudicants who had benefited from cilostazol therapy. This decline with crossover to placebo suggests that the initial improvement with cilostazol treatment was due to the drug's action. Withdrawal of pentoxifylline did not adversely affect walking.

Form deprivation myopia in adolescent monkeys.

BACKGROUND: Early in life, at ages corresponding to the rapid infantile phase of ocular growth in humans, visual feedback can modulate refractive development in monkeys and many other species. To determine if vision-dependent mechanisms can still influence refractive development in primates during the slow juvenile phase of ocular growth, the time period when myopia typically develops in human children, we examined the effects of form deprivation on adolescent monkeys. METHODS: Unilateral, form deprivation was produced in four rhesus monkeys by surgically fusing the eyelids of one eye. The onset of deprivation was between 3.7 and 5 years of age, which corresponds to onset ages between approximately 15 and 20 human years. The ocular effects of form deprivation were assessed by cycloplegic retinoscopy and A-scan ultrasonography. RESULTS: At the onset of form deprivation all four monkeys were isometropic and the axial dimensions in the two eyes were well matched. After 71 to 80 weeks of form deprivation, all of the deprived eyes had become relatively more myopic than their fellow non-treated eyes (mean anisometropia = -2.03 +/- 0.78 D) and they exhibited relative increases in vitreous chamber depth (mean = 0.55 +/- 0.31 mm) and axial length (mean = 0.49 +/- 0.35 mm). DISCUSSION: Our results demonstrate that vision-dependent mechanisms can influence ocular growth and refractive development in "teenage" monkeys. These results raise the possibility that visual experience may be involved in the genesis of school-age myopia in children.

Temporary arterial shunts to maintain limb perfusion after arterial injury: an animal study.

BACKGROUND: Temporary shunt placement can quickly restore perfusion after extremity arterial injury. This study examined the adequacy of limb blood flow with shunt use, non-heparin-bonded shunt patency over prolonged periods, and the safety of this technique. METHODS: Common iliac arteries were divided and 4.0-mm Silastic Sundt shunts placed in 16 anesthetized pigs. Eight (group I) had shunts placed immediately; eight others (group II) were shunted after an hour of limb ischemia and hemorrhagic shock. Physiologic parameters and femoral artery blood flow in both hindlimbs were continuously monitored. Limb lactic acid generation, oxygen utilization, and hematologic and metabolic effects were serially evaluated for 24 hours. RESULTS: Shunts remained patent in 13 of 16 pigs. Shunts thrombosed in two group I animals because of technical errors, but functioned well after thrombectomy and repositioning. Patency could not be maintained in one animal that died from shock. Flow in group I shunted limbs was 57 (+/-11 SD) % of control. For group II animals in shock, shunted limb flow initially averaged 46 +/- 15% of control, but 4 hours after shunt placement, the mean limb blood flow was the same as in group I. Increased oxygen extraction compensated for the lower flow. Lactic acid production was not increased in comparison to control limbs. CONCLUSION: Shunts provided adequate flow in this model of extremity trauma. Correctly placed shunts stayed patent for 24 hours, without anticoagulation, if shunt placement followed resuscitation.

The refractive development of untreated eyes of rhesus monkeys varies according to the treatment received by their fellow eyes.

To determine the extent to which the visual experience of one eye may influence the refractive development of its fellow eye, we analyzed the data of untreated (UT) eyes of monkeys that received different types of unilateral pattern deprivation. Subjects were 15 juvenile rhesus monkeys, with five monkeys in each of three treatment groups: aphakic eyes with optical correction (AC), aphakic eyes with no correction (ANC), and eyes that were occluded with an opaque contact lens (OC). Under general anaesthesia, refractive error (D) was determined by cycloplegic retinoscopy and axial length (mm) was determined with A-scan ultrasonography. For measurements of refractive error of the UT eyes, there was a significant main effect of groups according to the treatment of the fellow eyes, F(2, 12) = 6.6. While UT eyes paired with AC fellow eyes (mean = +4.2 D) were significantly more hyperopic than the eyes of age-matched normal monkeys (mean = +2.4 D), t(25), = 2.5, UT eyes paired with OC fellow eyes (mean = -0.5 D) were significantly more myopic than the eyes of normal monkeys, t(25) = -9. UT eyes paired with ANC fellow eyes (mean = +1.9 D) were not significantly different from normal eyes. For measurements of axial length there was also a significant main effect of groups, F(2, 12) = 6.9. While UT eyes paired with AC fellow eyes (mean = 16.9 mm) were significantly shorter than the eyes of age-matched normal monkeys (mean = 17.5 mm), t(25) = 2.3, UT eyes paired with OC fellow eyes (mean = 18.1 mm) were significantly longer than the eyes of normal monkeys, t(25) = 2.3. UT eyes paired with ANC fellow eyes (mean = 17.5 mm) were not significantly different from the eyes of normal monkeys. The measurements of axial length and of refractive error of the UT eyes were also significantly correlated with one another, probably indicating that the differences in refractive error were due to differences in axial length, r = -0.8. The present data reveal that despite normal visual experience, UT eyes can have their refractive development altered, systematically, simply as a function of the type of pattern deprivation received by their fellow eyes. These data add to the growing evidence that there is an interocular mechanism that is active during emmetropization. As a consequence, future models of eye growth will need to consider both: (1) the direct influence of visual input on the growing eye; as well as (2) the indirect influence coming from the fellow eye.

Emmetropization in the rhesus monkey (Macaca mulatta): birth to young adulthood.

PURPOSE: To provide baseline measurements on the postnatal changes in refractive error, corneal curvature, and axial elongation of the eyes of normal monkeys. Little is known about the course of normal eye growth from birth to adolescence, particularly how refractive parameters co-vary during development. In animal models of ametropia, usually one eye is manipulated and the fellow eye serves as a control. However, given individual differences, and without baseline data, it is impossible to determine whether either eye develops normally. METHODS: Measurements were obtained on 237 rhesus monkeys, whose ages ranged from birth to 5 years. Examinations included cycloplegic refraction by retinoscopy, keratometry measurements, and A-scan ultrasound measurements of axial length. The time course of development was evaluated using a growth curve analysis appropriate for a mixture of cross-sectional and longitudinal data. RESULTS: At birth, all three parameters were normally distributed and only weakly correlated. Monkeys had +7 D (SD=2.3 D) of hyperopia, corneal power of 58 D (SD=1 D), and axial length of 13.2 mm (SD=0.4 mm). Refractive error ranged from +0.5 D to +14.5 D, with a mean difference between the two eyes of 0.5 D. Corneal curvature ranged from 61 D to 54 D, with a mean difference between the two eyes of 0.8 D. Axial length ranged from 12.0 mm to 14.2 mm, with a mean difference between the two eyes of 0.1 mm. Although the degree of hyperopia achieved asymptote, of + 2 D, shortly after 1 year of age, corneal curvature and axial length did not achieve asymptote until nearly 5 years of age. By this time, refractive error had declined by 5 D, corneal curvature had declined by 7 D, and axial length had increased by 6 mm. CONCLUSIONS: The magnitude of the individual differences that can occur in a small sample of experimental subjects is large enough to necessitate reference to age norms derived from a large population. Our results provide a baseline for studies of normal and abnormal eye growth and ametropia in primates. Our results also led to the confirmation of a set of "rules" that have been offered as an explanation of how these three parameters interact during emmetropization.

Identification and antibiotic sensitivity of bacteria isolated from periapical lesions.

Periradicular tissues from 28 refractory endodontic cases requiring surgical intervention were submitted for histological diagnosis and microbiological culture. Bacteria isolated from these lesions were identified and then tested for their antibiotic sensitivity to a panel of common antibiotics. The periapical tissue specimens of 22 out of 28 lesions (79%) contained microorganisms. Of the 22 cases showing positive growth cultures, 15 were polymicrobial and 7 were single species isolates. Fifty-three different species were recovered: 29 anaerobes, 19 facultative anaerobes, and 5 aerobes. Microbes were observed under light microscopy in only one case. The most common organisms isolated were Propionibacterium acnes, Staphylococcus epidermidis, Streptococcus intermedius, Wolinella recta, Fusobacterium species, and Clostridium species. Antibiotic susceptibility results showed no clear cut evidence of significant antibiotic resistance among the species tested. The results of this study seem to corroborate earlier studies regarding the microbial population of periapical lesions refractory to nonsurgical endodontics.

Immersion disinfection of irreversible hydrocolloid impression in pH-adjusted sodium hypochlorite. Part 1: Microbiology.

Sodium hypochlorite is one of the disinfectants recommended for impressions, usually in a 1:10 dilution to minimize the negative effects on the impression material and poured gypsum cast. Dilution causes a loss of antimicrobial properties, however. Sodium hypochlorite is known to have enhanced antimicrobial properties at lower pH levels. This study evaluated the antimicrobial activity of sodium hypochlorite at progressively lower pH levels. A metal model of a dental arch was contaminated, and irreversible hydrocolloid impressions were made, cultured, disinfected (by immersion), and cultured again. Predisinfection and postdisinfection bacterial counts were compared. It was found that a 10-minute immersion in solutions reduced to pHs 7 to 11 consistently produced a 4-log (99.99%) or greater reduction in viable organisms. A pH of 10 was the only level that was consistently effective at decreased immersion times. It was effective in times of 3 minutes or greater.

Diffuser contact lenses retard axial elongation in infant rhesus monkeys.

In each of five monkeys, one eye was fitted with a diffuser lens at birth. This lens allowed pattern vision, but also reduced contrast by about 1 log unit. In four out of five monkeys, the treated eyes were shorter and more hyperopic than the untreated fellow eyes. At 25 weeks of age, interocular differences (OD -- OS) of the experimental group were significantly greater than interocular differences of age-matched normal monkeys for both axial length (P < 0.05) and refractive error (P < 0.02). In addition, while the treated eyes were significantly different from normal eyes for both axial length measurements (P < 0.01) and refractive error (P < 0.01), there were no significant differences between the untreated fellow eyes and normal eyes. In primates less severe pattern deprivation appears to produce an effect on eye growth that is opposite to that of severe pattern deprivation (little or no pattern vision), which typically results in axial myopia.

Immersion disinfection of irreversible hydrocolloid impressions. Part 1: Microbiology.

This study evaluated the effectiveness of four disinfectants for irreversible hydrocolloid impressions. Impressions were made of a sterile metal model of the maxillary arch that had been contaminated with one of the following bacteria: Staphylococcus aureus, Salmonella choleraesuis, Pseudomonas aeruginosa, Mycobacterium bovis, or Bacillus subtilis. The impressions were cultured before and after immersion in one of the following disinfectants: lodofive, OMC II, 0.525% sodium hypochlorite, or Alcide LD. Alcide LD achieved a 4-log10 (99.99%) or greater reduction in colony forming units for all five organisms plus mixed oral flora. Sodium hypochlorite achieved a 4-log10 reduction in three of the five organisms and mixed oral flora. Iodofive and OMC II were ineffective against all test organisms and mixed oral flora.

Immersion disinfection of irreversible hydrocolloid impressions. Part 2: Effects on gypsum casts.

This study evaluated the quality of gypsum casts recovered from disinfected irreversible hydrocolloid impressions. Four disinfectants were evaluated: 0.525% sodium hypochlorite, Alcide LD, Iodofive, and OMC II. Water served as the control. Specimens were evaluated for roughness, surface detail, and dimensional stability. Impressions disinfected with NaOCI or Alcide produced gypsum casts with physical properties that were generally equal or superior to casts from impressions rinsed with water. OMC II and Iodofive generally produced casts inferior to the controls.

Immersion disinfection of irreversible hydrocolloid impressions with sodium hypochlorite. Part I: Microbiology.

Current American Dental Association infection control guidelines recommend immersion disinfection of irreversible hydrocolloid impressions, and this study further defines the parameters for use of sodium hypochlorite. Sodium hypochlorite has been shown to be an effective disinfectant for impressions; however, it has not been fully evaluated for optimum immersion time and concentration. In this study, irreversible hydrocolloid impressions contaminated with different bacteria were immersed in varying concentrations of sodium hypochlorite for 1, 5, or 10 minutes. Dilute solutions of sodium hypochlorite (0.525% or 0.0525%) produced a 4-log10 (99.99%) reduction in colony-forming units of Staphylococcus aureus, Salmonella choleraesuis, or Pseudomonas aeruginosa after 1 to 5 minutes' immersion. Full-strength sodium hypochlorite (5.25%) required 5 minutes to produce a 4-log10 reduction of Bacillus subtilis. A 4-log10 reduction of Mycobacterium bovis was not obtained under any conditions examined.

Bacteriological analysis of high-speed handpiece turbines.

The microbial contamination of handpiece turbines was examined clinically. In 20 handpieces, no bacterial growth was found on any culture from an autoclaved or non-autoclaved handpiece group. But growth occurred in the positive control inoculated with fresh whole human saliva. An adjunctive investigation with saliva substitute showed that oral fluids can contaminate handpiece turbines during simulated clinical treatment.

Visual effects of opiates in pigeons. III. Luminance and wavelength sensitivity.

In a psychophysical task that permitted dissociations among sensitivity, overall stimulus control, and bias, pigeons learned to discriminate among stimuli along separate wavelength and luminance dimensions. Subsequent tests followed injections of morphine (1-8 mg/kg) and morphine plus naloxone (3 mg/kg). Morphine decreased sensitivity to both dimensions, and reduced overall control by luminance. These effects were reduced or reversed by naloxone. Morphine's effects appeared more pronounced for luminance than for wavelength stimuli. There were no consistent drug effects on response bias.

Safe storage times for sterile instrument packs.

Military health care facilities are required to place expiration dates on sterile instrument packs. There are few scientific guidelines for determining these dates. This article reports the findings of two studies conducted at Wilford Hall USAF Medical Center, which investigated the potential shelf-life of three packaging materials for sterile instruments. The results of the studies indicate that sterility is maintained for at least 1 year with all three materials. The maximum storage times allowed for sterile instruments at most military facilities appear to be overly restrictive.

Efficacy of various spray disinfectants on irreversible hydrocolloid impressions.

This study evaluated the effectiveness of eight disinfectant sprays on irreversible hydrocolloid impressions contaminated with three microorganisms (Staphylococcus aureus, Mycobacterium phlei, or Bacillus subtilis) or mixed oral flora. Alcide LD, OMC II, Biocide, and Professional Lysol Spray were relatively ineffective under the test conditions. Sporicidin and 0.525% sodium hypochlorite were able to effect a 4-log10 (99.99%) reduction against S aureus only. A 4-log10 reduction in bacterial counts was achieved by 5.25% sodium hypochlorite and Impresept in all tests except against B subtilis. Full-strength sodium hypochlorite (5.25%) was the most effective disinfectant overall and required the shortest contact time.

Evaluation of the shelf life of sterile instrument packs.

No published studies have specifically addressed the shelf life of sterile packaging materials commonly used in dentistry. This study examined the effect of time on the sterile integrity: paper envelopes, peel pouches, and nylon sleeves. Seven thousand two hundred sample packs, each containing three glass rods, were prepared and steam sterilized. After sterilization, half the packs (control packs) were immediately opened and the contents were analyzed for bacterial contamination. The other half (test packs) were randomly sorted and stored in dental treatment operatories. At monthly intervals for 12 months, 100 packs of each type were similarly opened and analyzed. The contamination rates between the control packs were not significantly different from one another. Differences in contamination rates between control packs and test packs for both the paper envelopes (0.4% and 0.7%) and the peel pouches (0.2% and 0.2%) were also insignificant. However, a significant difference (p less than 0.01) between control and test packs (0.3% and 1.5%) was found for the nylon sleeves. This increase was not time related and was attributed to difficulty in removing the glass rods from the nylon packs in a sterile manner. The most important finding was the absence of a trend toward an increased rate of contamination over time for any pack type. This indicates that when these materials are placed in covered storage in dental operatories, a 12-month storage period is not detrimental to their sterile integrity.

The use of warm solutions for more rapid disinfection of prostheses.

The barrier system of specific sequential steps for cleansing and disinfecting dental prosthesis as they enter and leave the laboratory was tested by comparing the use of room-temperature disinfectants for 10 minutes with warmed chlorine-based disinfectants at decreased immersion times. There were no statistically significant differences between 1- or 2-minute disinfection times using warmed 5.25% sodium hypochlorite, Alcide Expore, and Tetravalent Oxident, and using room-temperature Sporicidin for 10 minutes.