Risk Factors for Glaucoma Diagnosis and Surgical Intervention following Pediatric Cataract Surgery in the IRIS® Registry

PURPOSE

To compare demographic and clinical factors associated with glaucoma following cataract surgery (GFCS) and glaucoma surgery rates between infants, toddlers, and older children using a large, ophthalmic registry.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients in the IRIS® Registry (Intelligent Research in Sight) who underwent cataract surgery at ≤ 17 years old and between January 1, 2013 and December 31, 2020.

METHODS

Glaucoma diagnosis and procedural codes were extracted from the electronic health records of practices participating in the IRIS Registry. Children with glaucoma diagnosis or surgery before cataract removal were excluded. The Kaplan-Meier estimator was used to determine the cumulative probability of GFCS diagnosis and glaucoma surgery after cataract surgery. Multivariable Cox regression was used to identify factors associated with GFCS and glaucoma surgery.

MAIN OUTCOME MEASURES

Cumulative probability of glaucoma diagnosis and surgical intervention within 5 years after cataract surgery.

RESULTS

The study included 6658 children (median age, 10.0 years; 46.2% female). The 5-year cumulative probability of GFCS was 7.1% (95% confidence interval [CI], 6.1%-8.1%) and glaucoma surgery was 2.6% (95% CI, 1.9%-3.2%). The 5-year cumulative probability of GFCS for children aged < 1 year was 22.3% (95% CI, 15.7%-28.4%). Risk factors for GFCS included aphakia (hazard ratio [HR], 2.63; 95% CI, 1.96-3.57), unilateral cataract (HR, 1.48; 95% CI, 1.12-1.96), and Black race (HR, 1.61; 95% CI, 1.12-2.32). The most common surgery was glaucoma drainage device insertion (32.6%), followed by angle surgery (23.3%), cyclophotocoagulation (15.1%), and trabeculectomy (5.8%).

CONCLUSIONS

Glaucoma following cataract surgery diagnosis in children in the IRIS Registry was associated with young age, aphakia, unilateral cataract, and Black race. Glaucoma drainage device surgery was the preferred surgical treatment, consistent with the World Glaucoma Association 2013 consensus recommendations for GFCS management.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Treatment Outcomes for Juvenile Open Angle Glaucoma in Thailand

PRCIS

Juvenile open angle glaucoma (JOAG) patients with thick central corneas and negative family history were more likely to undergo surgery, mainly trabeculectomy with half requiring additional surgery within 10 years.

PURPOSE

To assess the characteristics and treatment outcomes of patients with JOAG in Thailand.

PATIENTS AND METHODS

This retrospective, multicenter study included all patients diagnosed with JOAG over 12 years from 2 tertiary hospitals in Bangkok, Thailand.

RESULTS

A total of 200 eyes from 104 patients were included in this study. The mean age of onset was 24.0±10.1 years (range: 5-40 y), with male predominance (60.5%). Over 90% of patients had bilateral JOAG and 25% had a positive family history. Negative family history (adjusted odds ratio=4.59, P =0.02) and thick central corneal thickness were surgical predictors (every 10 µm adjusted odds ratio=1.29, P =0.01). Over 70% of cases needed glaucoma surgery. Trabeculectomy with Mitomycin-C was performed on 131 eyes (65.5%) with a cumulative probability of complete success of 71.0%, 57.8%, 39.2%, and 26.9% and qualified success of 86.3%, 73.6%, 64.8%, and 45.7% at 1, 3, 5, and 10 years, respectively. The mean follow-up after surgery was 94.9 ± 69.8 months (range: 13-153 mo). There were no serious postoperative complications. Myopia and the number of baseline glaucoma medications were significantly associated with surgical failure.

CONCLUSIONS

Trabeculectomy with mitomycin C was the most common primary surgery performed in Thai patients with JOAG, and successfully reduced intraocular pressure without significant complications. Patients with thicker corneas were more likely to undergo surgery. By 10 years, half of the patients required additional surgery and risk factors for failure included myopia and the number of medications.

Regional Disparities in Pediatric Uveitis Care Availability in the United States

A service coverage analysis of pediatric uveitis care in the United States was implemented to determine geographic disparities between subspecialists and the pediatric population. There were substantial potential service deserts, including several small metropolitan areas.

Postoperative Management of Kahook Dual Blade Goniotomy with Phacoemulsification Cataract Extraction

Aim

To review the efficacy and safety of two common postoperative regimens following Kahook Dual Blade goniotomy with phacoemulsification cataract extraction (KDB-CE).

Materials and methods

This is a retrospective review of eyes undergoing KDB-CE from May 2016 to 2018 by a single surgeon. Almost 12-month follow-up data were assessed for two common postop regimens-treatment with (1) topical prednisolone acetate 1% with pilocarpine 1% (pred-pilo) or (2) difluprednate 0.05% postoperatively. Postoperative results were compared to each respective baseline intraocular pressure (IOP) levels.

Results

There were 53 eyes in the difluprednate group and 25 eyes in the pred-pilo group. In the difluprednate group, the IOP decreased at postoperative day 1 (POD1) [16 ± 5 baseline vs 15 ± 5 POD1, mean ± standard deviation (SD) in mm Hg, and p = 0.321], but increased at postoperative week 1 (POW1) due to a 15% rate of IOP-spikes (19 ± 9, p = 0.099). The number of IOP-lowering drops decreased from baseline (2 ± 1 drops) to 1 ± 1 drops at POD1 (p < 0.0001), and remained at 1 ± 1 drops through postoperative month 12 (POM12) (p < 0.0001). In the pred-pilo group, there was a statistically significant decrease in mean IOP at POW1 (16 ± 4 POW1 vs 18 ± 6 baseline, p = 0.044), which persisted through POM6. The number of IOP-lowering drops was not statistically significantly lower from baseline at POM3 (2 ± 1 at POM3, p = 0.188). Spikes in IOP, corneal edema, and hyphema were the most common complications.

Conclusion

Both postoperative regimens were effective following KDB-CE at reducing IOP at 12 months. The difluprednate group was likely to experience an IOP-spike at POW1 but used fewer IOP-lowering drops 12 months after KDB goniotomy. In the pred-pilo group, the number of IOP-lowering drops was equivalent to baseline levels at POM3. Aside from IOP spikes, there were similar complication rates observed between the two postoperative regimens. Due to demographic differences, it was not possible to compare relative IOP-lowering efficacy between the two postoperative regimens.

Clinical significance

It is efficacious and safe to use either postoperative regimen following KBD-CE. Postoperative trajectories may differ with respect to the postoperative regimen, but further randomized controlled trials are needed to compare various topical steroid medications for postoperative regimens following KDB-CE.

How to cite this article

Birnbaum F, Wakil S, Vu DM, et al. Postoperative Management of Kahook Dual Blade Goniotomy with Phacoemulsification Cataract Extraction. J Curr Glaucoma Pract 2023;17(4):169-174.

Two types of childhood glaucoma secondary to familial exudative vitreoretinopathy

BACKGROUND

Glaucoma secondary to familial exudative vitreoretinopathy presents as angle closure by either neovascular or non-neovascular mechanisms. We analyze the presentation and outcomes of two types of childhood glaucoma secondary to familial exudative vitreoretinopathy (FEVR).

METHODS

This retrospective cross-sectional study included all patients <18 years of age diagnosed with glaucoma after or concurrently with a diagnosis of FEVR between 2010 and 2020 from Queen Sirikit National Institute of Child Health in Bangkok, Thailand. Two groups were analyzed: neovascular or non-neovascular angle-closure status. Primary outcome measures were final visual acuity and intraocular pressure (IOP) in both groups.

RESULTS

Of 144 FEVR patients, 8 children (5.5%; 11 eyes, 3 bilateral cases) developed childhood glaucoma. Mean time between FEVR presentation and glaucoma was 42.2 ± 40.0 months. In the neovascular group, 3 of 9 eyes presented with glaucoma at FEVR diagnosis; 3 of 9 eyes (33%) required glaucoma surgery. In the non-neovascular group, 2 eyes presented with acute angle closure secondary to a phacomorphic lens. Both were treated with trabeculectomy, with resolution of pupillary block. All eyes had stage 4B FEVR or greater. Six of 8 eyes had stable or better visual acuity, and 10 eyes (91%) had IOP <21 mm Hg at final follow-up.

CONCLUSIONS

Childhood glaucoma secondary to FEVR is a rare complication caused by later stages of the disease. It may present as neovascular or non-neovascular angle closure, often requiring complex care. Therefore, awareness and adequate management of FEVR can help prevent additional morbidity from childhood glaucoma.

A Service Coverage Analysis of Primary Congenital Glaucoma Care Across the United States

PURPOSE

To assess the number of infants at risk of delayed primary congenital glaucoma (PCG) evaluation due to long travel times to specialists.

DESIGN

Cross-sectional geospatial service coverage analysis.

METHODS

All American Glaucoma Society (AGS) and American Association for Pediatric Ophthalmology and Strabismus (AAPOS) provider locations were geocoded using each organization's member directory. Sixty-minute drive time regions to providers were generated using ArcGIS Pro (Esri). The geographic intersection of AGS and AAPOS service areas was computed because patients typically require visits to both types of specialists. American Community Survey data were then overlaid to estimate the number of infants within and beyond the AGS/AAPOS service areas.

RESULTS

One thousand twenty-nine AGS and 1,040 AAPOS provider locations were geocoded. The analysis yielded 944,047 infants age 0-1 year (23.6%) who live beyond the AGS/AAPOS service areas. Therefore, approximately 14-94 new PCG cases/year may be at risk of delayed diagnosis as a result of living in a potential service desert. Compared with children living within the AGS/AAPOS service areas, children aged <6 years in these potential service deserts were more likely to live in households earning below the US federal poverty level, lack health insurance, and live in a single-parent home. These communities are disproportionately likely to experience other rural health disparities and are more prevalent across the Great Plains.

CONCLUSION

Service coverage analysis is a useful tool for identifying underserved regions for PCG referrals and evaluation. These data may assist in targeting screening programs in low access areas for pediatric glaucoma care.

A Geodemographic Service Coverage Analysis of Travel Time to Glaucoma Specialists in Florida

PRECIS

Approximately 1 in 9 Florida residents over the age of 65 years (438,642 people) live more than an hour away from a glaucoma specialist, which represents a significant barrier to care.

PURPOSE

To describe access to glaucoma care for Florida's elderly population using travel time to American Glaucoma Society (AGS) member offices.

METHODS

For this cross-sectional service coverage analysis, a list of AGS member locations was extracted from the AGS website, and addresses were geocoded using ArcGIS Online. Driving time regions were created using the service area tool in ArcGIS Pro 2.4 and overlaid with 2010 United States Census and 2016 American Community Survey data for all Florida residents age 65 or older.

RESULTS

Fifty-eight AGS member providers with 65 locations were identified and geocoded. There were 3,797,625 individuals aged over 65 years in Florida, of which 1,153,320 (30.4%) lived within 15 minutes of driving time from an AGS provider's office, 2,586,825 (68.1%) within 30 minutes, 3,358,983 (88.4%) within 60 minutes, and 3,491,815 (91.9%) within 120 minutes. The areas with the lowest access include rural areas near Lake Okeechobee and the Florida Panhandle. The population living beyond a 60-minute drive was more likely to be White, non-Hispanic and older, but less likely to be living below the federal poverty level or receiving public assistance than the population living within a 60-minute drive.

CONCLUSIONS

There is a significant travel burden for the elderly community of Florida to reach AGS providers. Additional studies could help identify other social barriers to accessing glaucoma providers in Florida and beyond in an effort to improve patient compliance and, ultimately, vision outcomes.

Fedratinib-induced orbital inflammation

A 69-year-old man with myelofibrosis presented with a two-day history of left periorbital swelling, blurred vision, and non-radiating dull orbital pain. On examination, there was restricted left-sided extraocular motility with conjunctival injection, chemosis, and periorbital edema. Magnetic resonance imaging demonstrated left-sided pre- and post-septal fat stranding concerning for orbital cellulitis. Two weeks before symptom onset, the patient began fedratinib therapy for myelofibrosis but discontinued this medication upon hospital admission. After restarting fedratinib, he presented with similar right-sided ophthalmic signs. A review of his medication history revealed a temporal relationship between symptom onset and fedratinib use. After medication discontinuation, his symptoms improved rapidly.

XEN Gel Stent Implantation Following Encircling Scleral Buckle Surgery

Scleral buckling procedures create a challenge for intraocular pressure (IOP) control in the glaucoma patient. The encircling band is believed to compress vortex veins, causing increased episcleral venous pressure, a proposed mechanism for secondary glaucoma. Glaucoma drainage device implantation is preferred over trabeculectomy when medical management fails, but often involves modification of the glaucoma implant and manipulation of the fibrotic capsule surrounding the scleral buckle. This case demonstrates that ab externo XEN gel stent implantation may successfully reduce IOP without interfering with the previous scleral buckle, a major limitation of previous glaucoma filtering surgeries. [Ophthalmic Surg Lasers Imaging Retina. 2020;51:289-292.].

Factors Impacting Outcomes and the Time to Recovery From Malignant Glaucoma

PURPOSE

To identify factors associated with the successful treatment of malignant glaucoma (MG).

DESIGN

Retrospective case series.

METHODS

Setting: single institution; study population: 64 eyes (55 subjects) with MG; observation procedure(s): chart review; main outcome measures: anatomy, intraocular pressure (IOP), best visual acuity (BVA).

RESULTS

87.5% (n=56/64) of eyes with MG required surgical intervention. Vitrectomy was more likely to be successful in eyes with a history of <3 incisional surgeries, <3 glaucoma drops, or IOP ≤30 mm Hg (P < .05). If vitrectomy was performed within 30 days, recovery of anatomy, BVA, and IOP occurred sooner (P < .05). IOP reduction was greater in subjects treated with oral carbonic anhydrase inhibitors (P = .016) or Nd:YAG laser hyaloidotomy (P = .007), and without a history of MG (P = .007). Time to maximal improvement was significantly longer for IOP and BVA than anatomy (P < .001). Treatment of MG with an oral carbonic anhydrase inhibitor hastened anatomic recovery (P = .01). Time to improvement in BVA was significantly faster in men and African Americans (P < .05). Time to maximal reduction in IOP occurred sooner in eyes that underwent anterior chamber reformation in clinic (P < .002). Trabeculectomy surgery prior to MG was associated with prolonged recovery of anatomy, BVA, and IOP (P < .05).

CONCLUSIONS

Earlier vitrectomy may shorten recovery times for MG. Nd:YAG laser hyaloidotomy and oral carbonic anhydrase inhibitors may lead to greater IOP reduction. The time to maximal improvement in IOP and BVA may be longer than the time to anatomic resolution. Although trabeculectomy may impede time to recovery from MG, oral carbonic anhydrase inhibitors may shorten the time to anatomic recovery and anterior chamber reformation may hasten IOP recovery.

Factors Associated with Interventions after Laser Peripheral Iridotomy for Primary Angle-Closure Spectrum Diagnoses

PURPOSE

To assess factors associated with receipt of subsequent medical, laser, or surgical interventions after laser peripheral iridotomy (LPI).

DESIGN

Retrospective review.

PARTICIPANTS

A total of 1271 eyes in 692 subjects with narrow angles (NAs) that were treated with LPI.

METHODS

Demographic and clinical factors associated with primary angle-closure (PAC) or PAC glaucoma (PACG) versus PAC suspect (PACS) diagnosis and use of glaucoma medications at the time of LPI, as well as factors predictive of subsequent addition of glaucoma medications, and receipt of selective laser trabeculoplasty (SLT), cataract surgery, and glaucoma surgery were assessed using logistic regression with generalized estimating equations. Kaplan-Meier curves and Cox proportional-hazards regression analysis were used to assess baseline factors affecting the time to SLT, cataract surgery, or glaucoma surgery.

MAIN OUTCOME MEASURES

Diagnosis of PAC/PACG and medical, laser, or surgical interventions after LPI.

RESULTS

African Americans (odds ratio [OR], 2.12; P < 0.001) were significantly more likely than whites to have PAC/PACG than PACS and to already be taking glaucoma medications (OR, 2.25, P < 0.001) at the time of LPI. In multivariable logistic regression analysis, African Americans were significantly more likely to be prescribed additional glaucoma medications after LPI (OR, 1.73; P = 0.025) and receive glaucoma surgery (OR, 2.7; P = 0.007), but were less likely to receive SLT (OR, 0.37; P = 0.009). In multivariate Cox proportional-hazards regression analysis, African Americans had longer time to SLT than whites (hazard ratio [HR], 0.41; P = 0.022), but a shorter time to glaucoma surgery (HR, 2.57; P = 0.004). There was no significant association between race and the likelihood of cataract surgery or time to cataract surgery (P > 0.10).

CONCLUSIONS

African Americans were more likely than whites to carry a diagnosis of PAC or PACG at the time of LPI and were significantly more likely to be prescribed additional glaucoma medications and require glaucoma surgery after LPI. Improved screening methods that target African Americans with NAs are needed so that preventive interventions such as LPI can be performed earlier to decrease the risk of progression.

Surgical outcomes associated with a sutureless drainage valve implantation procedure in patients with refractory glaucoma

Purpose

To evaluate the safety and efficacy profile of a sutureless procedure for drainage valve implantation with combined cataract removal and/or endoscopic cyclophotocoagulation (ECP).

Materials and methods

A retrospective case series study of consecutive surgeries for Ahmed glaucoma valve (AGV; New World Medical) implantation in a 1-year period was analyzed. The surgery was performed using a Tisseel fibrin sealant (Baxter Healthcare Corporation) in place of sutures. Some subsets within the case series also included a cataract extraction with intraocular lens (CEIOL) insertion and/or ECP (Endo Optiks) within the same procedure. Primary outcomes for this study including efficacy (IOP change, reduction in medications) and safety (complications and reoperations) were measured out to 3 years. Comparisons between subsets were made using ANOVA with post hoc Tukey’s pairwise tests.

Results

One hundred twenty-two eyes of 99 patients underwent sutureless AGV implantation surgery. Of the 122, 18 had an AGV implantation only, 46 had an AGV + CEIOL, 35 had an AGV + ECP, and 23 had an AGV + CEIOL + ECP. In total, there was a significant decrease in IOP (P<0.0001) and number of glaucoma medications (P≤0.0054) at each postoperative visit. In a one-way ANOVA, there were no significant differences in mean IOP between the different subsets of surgeries (P>0.05); 10.7% and 14.8% of eyes required a reoperation either for a complication or for uncontrolled glaucoma, respectively.

Conclusion

Sutureless valve implantation is associated with a significant reduction in IOP percentage and medication use after the procedure with a safety profile comparable with other glaucoma surgeries.

Seroepidemiological Studies of Arboviruses in Africa

The literature on sero-epidemiological studies of flaviviral infections in the African continent is quite scarce. Much of the viral epidemiology studies have been focussing on diseases such as HIV/AIDS because of their sheer magnitude and impact on the lives of people in the various affected countries. Increasingly disease outbreaks caused by arboviruses such as the recent cases of chikungunya virus, dengue virus and yellow fever virus have prompted renewed interest in studying these viruses. International agencies from the US, several EU nations and China are starting to build collaborations to build capacity in many African countries together with established institutions to conduct these studies. The Tofo Advanced Study Week (TASW) was established to bring the best scientists from the world to the tiny seaside town of Praia do Tofo to rub shoulders with African virologists and discuss cutting-edge science and listen to the work of researchers in the field. In 2015 the 1st TASW focussed on Ebola virus. The collections of abstracts from participants at the 2nd TASW which focused on Dengue and Zika virus as well as presentations on other arboviruses are collated in this chapter.

Risk Factors Associated with Missed Diagnoses of Narrow Angles by the Van Herick Technique

PURPOSE

To identify which factors are associated with a deep-appearing anterior chamber on slit-lamp examination by the Van Herick (VH) technique in eyes with a diagnosis of narrow angle (NA) on gonioscopy.

DESIGN

Retrospective review.

PARTICIPANTS

One thousand three hundred fourteen eyes in 696 participants with NA on indirect gonioscopy.

METHODS

All included eyes were graded as narrow with iridotrabecular contact on indirect gonioscopy in a darkened room by a single trained glaucoma specialist. Before gonioscopy, eyes were graded as narrow or deep by VH slit-lamp examination technique. Demographic and clinical factors predictive of a deep VH grading were assessed using logistic regression with generalized estimating equations.

MAIN OUTCOME MEASURES

Factors associated with deep versus narrow VH grade.

RESULTS

Using the VH technique, 13.7% of eyes (n = 180/1314) with NA on gonioscopy were classified as deep. Eyes with primary angle-closure glaucoma (PACG; odds ratio, 2.43; P < 0.001) and primary angle closure (PAC; odds ratio, 1.38; P = 0.006) were significantly more likely to be graded as deep by the VH technique relative to eyes that were primary angle-closure suspects (PACSs). In multivariate analysis, male gender (odds ratio, 2.22; P < 0.001), myopia (odds ratio, 1.4; P = 0.048), and black (odds ratio, 4.11; P < 0.001) and Asian (odds ratio, 2.24; P = 0.044) race were independent risk factors for a deep grading with the VH technique in eyes with NA on gonioscopy.

CONCLUSIONS

Patients with NAs on gonioscopy who are men, myopic, and of black or Asian race are at increased risk of being misdiagnosed with deep angles if examined with the VH technique alone. Eyes with PACG and PAC may be more likely than those with PACS to be misdiagnosed as deep with the VH technique. It is possible that by being missed by the VH technique, these eyes could have progressed from PACS to PAC and PACG. Patients with these demographic and clinical characteristics in the presence of other risk factors for glaucoma should undergo careful gonioscopy.

Preferential biological processes in the human limbus by differential gene profiling

Corneal epithelial stem cells or limbal stem cells (LSCs) are responsible for the maintenance of the corneal epithelium in humans. The exact location of LSCs is still under debate, but the increasing need for identifying the biological processes in the limbus, where LSCs are located, is of great importance in the regulation of LSCs. In our current study we identified 146 preferentially expressed genes in the human limbus in direct comparison to that in the cornea and conjunctiva. The expression of newly identified limbal transcripts endomucin, fibromodulin, paired-like homeodomain 2 (PITX2) and axin-2 were validated using qRT-PCR. Further protein analysis on the newly identified limbal transcripts showed protein localization of PITX2 in the basal and suprabasal layer of the limbal epithelium and very low expression in the cornea and conjunctiva. Two other limbal transcripts, frizzled-7 and tenascin-C, were expressed in the basal epithelial layer of the limbus. Gene ontology and network analysis of the overexpressed limbal genes revealed cell-cell adhesion, Wnt and TGF-β/BMP signaling components among other developmental processes in the limbus. These results could aid in a better understanding of the regulatory elements in the LSC microenvironment.

Relationship between corneal hysteresis and optic nerve parameters measured with spectral domain optical coherence tomography

BACKGROUND

Corneal hysteresis (CH) has been associated with visual field damage in glaucoma and is related to the velocity of perimetric glaucoma progression. We undertook this investigation to determine whether CH is associated with structural markers of glaucoma damage on spectral domain optical coherence tomography (SD-OCT).

METHODS

In this retrospective study, 131 patients under glaucoma evaluation were evaluated with SD-OCT (Cirrus; Carl Zeiss Meditec, Dublin, CA) and had CH measurements with the ocular response analyzer (Reichert, Inc., Buffalo, NY). Pearson and partial correlation adjusting for age were preformed to examine the association between CH and variables of interest. Generalized estimating equations were used to construct simple and multiple linear models.

RESULTS

While Pearson correlations were modest overall, CH best correlated with mean deviation (MD; r = 0.19) followed by average retinal nerve fiber layer (RNFL) thickness (r = 0.18) and vertical cup to disc ratio (r = -0.11) in the open angle glaucoma group. In univariable models, CH varied as a function of MD (ß = 0.1, 95 % CI 0.03, 0.1; p < 0.001) and of average RNFL thickness (ß = 0.2, 95 % CI 0.1, 0.4; p = 0.001). In a multivariable analysis including MD, age, average RNFL thickness, and glaucoma status, MD (p = 0.001) and age (p < 0.001) retained significant associations with CH.

CONCLUSIONS

In patients under evaluation and treatment for glaucoma, CH was more closely related to visual field MD than to structural markers of glaucoma damage as measured by SD-OCT.

Examination of the folding of E. coli CspA through tryptophan substitutions

Escherichia coli cold shock protein, CspA, folds very rapidly (time constant, tau = 4 msec) by an apparent two-state mechanism. However, recent time-resolved infrared (IR) temperature-jump experiments indicate that the folding trajectory of CspA may be more complicated. The sole tryptophan of wild-type CspA (Trp11), which is used to monitor the folding process by fluorescence spectroscopy, is located in an unusual aromatic cluster on the surface of CspA within the nucleic acid binding site. To gain a more global picture of the folding kinetics of CspA and to determine if there are any previously undetected intermediates, we have introduced a second tryptophan at three different surface locations in the protein. The three mutations did not significantly alter the tertiary structure of CspA, although two of the substitutions were found to be slightly stabilizing. Two-state folding, as detected by stopped-flow fluorescence spectroscopy, is preserved in all three mutants. These results indicate that the fast folding of CspA is driven by a concerted mechanism.

Role of a solvent-exposed aromatic cluster in the folding of Escherichia coli CspA

Escherichia coli CspA is a member of the cold shock protein family. All cold shock proteins studied to date fold rapidly by an apparent two-state mechanism. CspA contains an unusual cluster of aromatic amino acids on its surface that is necessary for nucleic acid binding and also provides stability to CspA (Hillier et al., 1998). To elucidate the role this aromatic cluster plays in the determining the folding rate and pathway of CspA, we have studied the folding kinetics of mutants containing either leucine or serine substituted for Phe 18, Phe20, and/or Phe31. The leucine substitutions are found to accelerate folding and the serine substitutions to decelerate folding. Because these residues exert effects on the free energy of the folding transition state, they may be necessary for nucleating folding. They are not responsible, however, for the very compact, native-like transition state ensemble seen in the cold shock proteins, as the refolding rates of the mutants all show a similar, weak dependence of unfolding rate on denaturant concentration. Using mutant cycle analysis, we show that there is energetic coupling among the three residues between the unfolded and transition states, suggesting that the cooperative nature of these interactions helps to determine the unfolding rate. Overall, our results suggest that separate evolutionary pressures can act simultaneously on the same group of residues to maintain function, stability, and folding rate.

Body fatness and bioelectrical impedance in non-obese pre-menarcheal girls: comparison to anthropometry and evaluation of predictive equations

OBJECTIVES

To determine in non-obese pre-menarcheal girls if bioelectrical impedance (BIA) is a better predictor of body fatness than triceps skinfold (TSF) or body mass index (BMI) and to cross-validate published equations for determination of fat-free mass (FFM) from BIA in pre-menarcheal girls.

DESIGN

Cross-sectional analysis of data from 132 non-obese pre-menarcheal girls. The relationship of percent body fat (%BF), derived from isotopic dilution of H2 18O to TSF, BMI, and %BF by BIA, calculated from measures of height, weight and resistance was examined by correlation analysis.

SETTING

Massachusetts Institute of Technology (MIT) Clinical Research Center in Cambridge, MA, USA.

SUBJECTS

Pre-menarcheal girls aged 8-12 y were recruited from local schools, MIT summer day camp and by word of mouth.

RESULTS

TSF accounted for 68% of the explained variance (R2) in the prediction of %BF measured by H2 18O, compared to 38% for BMI and 70% for BIA. Prediction of FFM by comparison of published equations was evaluated in this population. The predictive ability differed by Tanner stage. Kushner's equation (Kushner et al, 1992), based solely on height2/resistance was the only equation that provided estimates that did not differ significantly from measured values among all Tanner stages.

CONCLUSIONS

BIA appears to be a valid and reliable measure of FFM but is no better than TSF in predictions of body fat.

Factors influencing infant mortality in Vietnam

Selected determinants of overall infant mortality in Vietnam were examined using data from the 1988 Vietnam Demographic and Health Survey, and factors underlying neonatal and post-neonatal mortality were also compared. Effects of community development characteristics, including health care, were studied by logistic regression analysis in a subsample of rural children from the 1990 Vietnam Accessibility of Contraceptives Survey. Infant neonatal and post-neonatal mortality rates showed comparable distributions by birth order, maternal age, pregnancy intervals, mother's education and urban-rural residence. Rates were highest among first order births, births after an interval of less than 12 months, births to illiterate mothers and to those aged under 21 or over 35 years of age. Logistic regression analysis showed that the most significant predictor of infant mortality was residence in a province where overall infant mortality was over 40 per 1000 live births. In the rural subsample, availability of public transport was the most persistent community development predictor of infant mortality. Reasons for the low infant mortality rates in Vietnam compared to countries with similar levels of economic development are discussed.

Contraceptive use in Vietnam: the effect of individual and community characteristics

Data from the 1988 Vietnamese Demographic and Health Survey and the 1990 Vietnam Study of Accessibility of Contraceptives were used in this analysis to determine how selective individual and community characteristics influenced the use of modern methods of contraception in Vietnam. Although there were no significant differences in the use of contraceptives between women with a primary education and those with a higher educational attainment, the illiterate women with no formal education were significantly less likely to use modern methods of contraception. Women living in provinces with high infant mortality rates were significantly less likely to use modern methods of contraception than women in low-infant-mortality provinces. Independent of other individual and community characteristics, there were no significant differences in the use of contraception between urban and rural women.

Fertility and family planning in Vietnam

This report provides the first reliable statistical data on fertility patterns and the family planning program in the Socialist Republic of Vietnam. Findings are from the 1988 Demographic and Health Survey of Vietnam and the 1989 census survey. The data show that the total fertility rate has declined from over 6 children per woman in the early 1970s to under 4 in the later 1980s. Contraceptive prevalence for modern methods is estimated at 37 percent among married women of reproductive age in 1988. The average duration of breastfeeding is over 14 months; marriage is relatively late. The IUD is the most common contraceptive method and abortion is widespread. The major factors likely to influence fertility and family planning in the future are the government's population policy, improved access to modern methods of contraception, and the institution of new economic policies that are currently under way in Vietnam.