Strengthening retinopathy of prematurity screening and treatment services in Nigeria: a case study of activities, challenges and outcomes 2017-2020.

OBJECTIVES: Retinopathy of prematurity (ROP) will become a major cause of blindness in Nigerian children unless screening and treatment services expand. This article aims to describe the collaborative activities undertaken to improve services for ROP between 2017 and 2020 as well as the outcome of these activities in Nigeria. DESIGN: Descriptive case study. SETTING: Neonatal intensive care units in Nigeria. PARTICIPANTS: Staff providing services for ROP, and 723 preterm infants screened for ROP who fulfilled screening criteria (gestational age <34 weeks or birth weight ≤2000 g, or sickness criteria). METHODS AND ANALYSIS: A WhatsApp group was initiated for Nigerian ophthalmologists and neonatologists in 2018. Members participated in a range of capacity-building, national and international collaborative activities between 2017 and 2018. A national protocol for ROP was developed for Nigeria and adopted in 2018; 1 year screening outcome data were collected and analysed. In 2019, an esurvey was used to collect service data from WhatsApp group members for 2017-2018 and to assess challenges in service provision. RESULTS: In 2017 only six of the 84 public neonatal units in Nigeria provided ROP services; this number had increased to 20 by 2018. Of the 723 babies screened in 10 units over a year, 127 (17.6%) developed any ROP; and 29 (22.8%) developed type 1 ROP. Only 13 (44.8%) babies were treated, most by intravitreal bevacizumab. The screening criteria were revised in 2020. Challenges included lack of equipment to regulate oxygen and to document and treat ROP, and lack of data systems. CONCLUSION: ROP screening coverage and quality improved after national and international collaborative efforts. To scale up and improve services, equipment for neonatal care and ROP treatment is urgently needed, as well as systems to monitor data. Ongoing advocacy is also essential.

Outcome of cataract surgery in rural areas of Kaduna State, Nigeria.

AIM: To evaluate the visual outcome of all patients who had cataract surgery with intraocular lens implant in five Local Government Areas (LGAs) of Kaduna State and to identify reasons for poor outcome and to proffer suggestions to improve outcome. MATERIALS AND METHODS: A prospective study using the WHO cataract surgery record form to collect data from consecutively screened and operated cataract patients over a period of 18 months (January 2006-June 2007). Data was analysed using Monitoring Catarct Surgery Outcome V2.3 software by the WHO. RESULTS: A total of 690 eyes of 644 patients were operated, ECCE+PCIOL implantation was achieved in 664 (96.2%) while 26(3.8%) had anterior chamber lens implant. The age range was 40 - 99 years and male to female ratio was 1: 0.9. Good outcome was obtained in 239 (34.6%) and 370(53.6%) of patients at 2 and 8 weeks respectively in the postoperative period. Surgical complications like striate keratopathy/corneal oedema (18.3%), cortical reminant (4.2%) and posterior capsular rupture (2.9%), and uncorrected refractive error were identified as reasons for poor outcome. CONCLUSION: A good outcome of greater than 80% at 8 weeks postoperative period was not achieved. Provision of postoperative correction of residual ametropia in the rural community, as well as improved surgical techniques of surgeons, will go a long way to improve the visual outcome and cataract surgery uptake.

Recurrent endometrial cancer: a retrospective study.

OBJECTIVE: The value of follow-up after treatment for endometrial cancer will be discussed. STUDY DESIGN: We evaluated our clinical experience, including mode of detection, of patients with recurrent endometrial cancer treated in the Erasmus Medical Centre in Rotterdam over a 20-year period. Clinical data and histopathological features from 64 patients were analyzed. Survival was analyzed with a Kaplan-Meier curve. RESULTS: Twenty-two patients had a local recurrence, 30 had a distant recurrence and 12 had simultaneous local and distant recurrent disease. Ninety-five percent of the local recurrences and 67% of the distant recurrences were detected within three years. Twenty-seven patients had a screen-detected recurrence, 34 had an interval screening recurrence and two had a chance finding recurrence. The overall survival rate at two years was 70% and at five years 53%. Patients with a screen-detected recurrence had a 5-year survival rate of 62%, while patients with interval screening and chance finding recurrences had a 5-year survival rate of 47%. CONCLUSION: A follow-up program in the first three years after primary treatment of endometrial cancer is useful in detecting recurrent disease. We have no reason to use a different program of follow-up in patients with low risk primary disease.

Stage III and IV endometrial cancer: a 20-year review of patients.

In advanced endometrial cancer, the importance of peritoneal cytology and optimal surgical cytoreduction remain subjects of discussion. We evaluated our clinical experience of 67 patients with FIGO stage III and IV endometrial cancer treated in the Erasmus Medical Centre in Rotterdam over a 20-year period with an emphasis on stage IIIA disease based on positive cytology only and optimal cytoreduction. Lymphadenectomy was not routinely performed and peritoneal cytology was examined in 74% of the patients. Stage IIIA disease was found in 33 patients, 10 of whom had positive cytology only. Analysis showed that incidence of recurrence and survival rates of patients with stage IIIA disease based on positive cytology only were comparable with stage IIIA disease based on other factors. In 50 patients, it was possible to remove all macroscopic tumor, whereas in 17 patients, an optimal cytoreduction was not achievable. The 2- and 5-year survival rates after optimal cytoreduction were 82.2% and 65.6%; where this could not be achieved, these figures were 50.8% and 40.6%. In advanced endometrial cancer patients, positive peritoneal cytology seems an important prognostic factor in stage IIIA disease if lymph node status is unknown. Survival is improved if optimal surgical cytoreduction is achievable.

A threonine residue (Thr71) at the intracellular end of the M1 helix plays a critical role in the gating of Kir6.2 channels by intracellular ATP and protons.

ATP-sensitive K+ (K(ATP)) channels are known to be gated by several intracellular molecules, but the gating mechanisms remain unclear. To understand the relationship of channel gating to ligand binding, we studied Kir6.2 channel gating by ATP and protons, which inhibit and activate the channel, respectively. We have previously shown that a threonine residue (Thr71) is critical for the pH sensitivity of Kir6.2 channel. If this site is involved in channel gating rather than ligand binding, it should affect channel gating by both ATP and proton. To test this hypothesis we performed a mutation analysis. Site-specific mutations of Thr71 to a bulky residue reduced the ATP sensitivity by >100-fold and eliminated the pH sensitivity. Single-channel activity of these mutants was stabilized at the open state with no detectable rundown. Mutations to a small amino acid had little effect on the ATP and pH sensitivities. Mutations to intermediate amino acids reduced but did not abolish the ATP and pH sensitivities. Hydrophobicity is not critical, as both polar and nonpolar amino acids are found in each group. Mutation to a positively charged lysine markedly exacerbated the pH- but not ATP-sensitivity, whereas mutation to glutamate moderately reduced ATP and pH sensitivities. These results indicate that the residue mass is critical for Kir6.2 channel gating, a mass that should be below 120 daltons with no charge. The existence of such a site as Thr71 involved in channel gating by both ATP and proton suggests that channel gating in the K(ATP) channel likely is separate from ligand binding.

Modulation of the heteromeric Kir4.1-Kir5.1 channels by P(CO(2)) at physiological levels.

Several inward rectifier K(+) (Kir) channels are pH-sensitive, making them potential candidates for CO(2) chemoreception in cells. However, there is no evidence showing that Kir channels change their activity at near physiological level of P(CO(2)), as most previous studies were done using high concentrations of CO(2). It is known that the heteromeric Kir4.1-Kir5.1 channels are highly sensitive to intracellular protons with pKa value right at the physiological pH level. Such a pKa value may allow these channels to regulate membrane potentials with modest changes in P(CO(2)). To test this hypothesis, we studied the Kir4.1-Kir5.1 currents expressed in Xenopus oocytes and membrane potentials in the presence and absence of bicarbonate. Evident inhibition of these currents (by approximately 5%) was seen with P(CO(2)) as low as 8 torr. Higher P(CO(2)) levels (23-60 torr) produced stronger inhibitions (by 30-40%). The inhibitions led to graded depolarizations (5-45 mV with P(CO(2)) 8-60 torr). Similar effects were observed in the presence of 24 mM bicarbonate and 5% CO(2). Indeed, the Kir4.1-Kir5.1 currents were enhanced with 3% CO(2) and suppressed with 8% CO(2) in voltage clamp, resulting in hyper- (-9 mV) and depolarization (16 mV) in current clamp, respectively. With physiological concentration of extracellular K(+), the Kir4.1-Kir5.1 channels conduct substantial outward currents that were similarly inhibited by CO(2) as their inward rectifying currents. These results therefore indicate that the heteromeric Kir4.1-Kir5.1 channels are modulated by a modest change in P(CO(2)) levels. Such a modulation alters cellular excitability, and enables the cell to detect hypercapnia and hypocapnia in the presence of bicarbonate.

Distinct histidine residues control the acid-induced activation and inhibition of the cloned K(ATP) channel.

The modulation of K(ATP) channels during acidosis has an impact on vascular tone, myocardial rhythmicity, insulin secretion, and neuronal excitability. Our previous studies have shown that the cloned Kir6.2 is activated with mild acidification but inhibited with high acidity. The activation relies on His-175, whereas the molecular basis for the inhibition remains unclear. To elucidate whether the His-175 is indeed the protonation site and what other structures are responsible for the pH-induced inhibition, we performed these studies. Our data showed that the His-175 is the only proton sensor whose protonation is required for the channel activation by acidic pH. In contrast, the channel inhibition at extremely low pH depended on several other histidine residues including His-186, His-193, and His-216. Thus, proton has both stimulatory and inhibitory effects on the Kir6.2 channels, which attribute to two sets of histidine residues in the C terminus.

Requirement of multiple protein domains and residues for gating K(ATP) channels by intracellular pH.

ATP-sensitive K(+) channels (K(ATP)) are regulated by pH in addition to ATP, ADP, and phospholipids. In the study we found evidence for the molecular basis of gating the cloned K(ATP) by intracellular protons. Systematic constructions of chimerical Kir6.2-Kir1.1 channels indicated that full pH sensitivity required the N terminus, C terminus, and M2 region. Three amino acid residues were identified in these protein domains, which are Thr-71 in the N terminus, Cys-166 in the M2 region, and His-175 in the C terminus. Mutation of any of them to their counterpart residues in Kir1.1 was sufficient to completely eliminate the pH sensitivity. Creation of these residues rendered the mutant channels clear pH-dependent activation. Thus, critical players in gating K(ATP) by protons are demonstrated. The pH sensitivity enables the K(ATP) to regulate cell excitability in a number of physiological and pathophysiological conditions when pH is low but ATP concentration is normal.

Direct activation of cloned K(atp) channels by intracellular acidosis.

ATP-sensitive K(+) (K(ATP)) channels may be regulated by protons in addition to ATP, phospholipids, and other nucleotides. Such regulation allows a control of cellular excitability in conditions when pH is low but ATP concentration is normal. However, whether the K(ATP) changes its activity with pH alterations remains uncertain. In this study we showed that the reconstituted K(ATP) was strongly activated during hypercapnia and intracellular acidosis using whole-cell recordings. Further characterizations in excised patches indicated that channel activity increased with a moderate drop in intracellular pH and decreased with strong acidification. The channel activation was produced by a direct action of protons on the Kir6 subunit and relied on a histidine residue that is conserved in all K(ATP). The inhibition appeared to be a result of channel rundown and was not seen in whole-cell recordings. The biphasic response may explain the contradictory pH sensitivity observed in cell-endogenous K(ATP) in excised patches. Site-specific mutations of two residues showed that pH and ATP sensitivities were independent of each other. Thus, these results demonstrate that the proton is a potent activator of the K(ATP). The pH-dependent activation may enable the K(ATP) to control vascular tones, insulin secretion, and neuronal excitability in several pathophysiologic conditions.

Molecular determinants for the distinct pH sensitivity of Kir1.1 and Kir4.1 channels.

Kir1.1 (ROMK1) is inhibited by hypercapnia and intracellular acidosis with midpoint pH for channel inhibition (pK(a)) of approximately 6.7. Another close relative, Kir4.1 (BIR10), is also pH sensitive with much lower pH sensitivity (pK(a) approximately 6. 0), although it shares a high sequence homology with Kir1.1. To find the molecular determinants for the distinct pH sensitivity, we studied the structure-functional relationship using site-directed mutagenesis. An NH(2)-terminal residue (Lys-53) was found to be responsible for the low pH sensitivity in Kir4.1. Mutation of this lysine to valine (K53V), a residue seen at the same position in Kir1. 1, markedly increased channel sensitivity to CO(2)/pH. Reverse mutation on Kir1.1 (V66K) decreased the CO(2)/pH sensitivities. Interestingly, mutation of these residues to glutamate greatly enhanced the pH sensitivity in both channels. Other contributors to the distinct pH sensitivity were histidine residues in the COOH terminus, whose numbers are fewer in Kir4.1 than Kir1.1. Mutation of two of these histidine residues in Kir1.1 (H342Q/H354N) reduced CO(2)/pH sensitivities, whereas the creation of two histidines (S328H/G340H) in Kir4.1 increased the CO(2)/pH sensitivities. Combined mutations of the lysine and histidine residues in Kir4.1 (K53V/S328H/G340H) gave rise to a channel that had CO(2)/pH sensitivities almost identical to those of the wild-type Kir1.1. Thus the residues demonstrated in our current studies are likely the molecular basis for the distinct pH sensitivity between Kir1.1 and Kir4.1.

Involvement of histidine residues in proton sensing of ROMK1 channel.

ROMK channels are inhibited by intracellular acidification. This pH sensitivity is related to several amino acid residues in the channel proteins such as Lys-61, Thr-51, and His-206 (in ROMK2). Unlike all other amino acids, histidine is titratable at pH 6-7 carrying a positive charge below pH 6. To test the hypothesis that certain histidine residues are engaged in CO(2) and pH sensing of ROMK1, we performed experiments by systematic mutations of all histidine residues in the channel using the site-directed mutagenesis. There are two histidine residues in the N terminus. Mutations of His-23, His-31, or both together did not affect channel sensitivity to CO(2). Six histidine residues are located in the C terminus. His-225, His-274, His-342, and His-354 were critical in CO(2) and pH sensing. Mutation of either of them reduced CO(2) and pH sensitivities by 20-50% and approximately 0.2 pH units, respectively. Simultaneous mutations of all of them eliminated the CO(2) sensitivity and caused this mutant channel to respond to only extremely acidic pH. Similar mutations of His-280 had no effect. The role of His-270 in CO(2) and pH sensing is unclear, because substitutions of this residue with either a neutral, negative, or positive amino acid did not produce any functional channel. These results therefore indicate that histidine residues contribute to the sensitivity of the ROMK1 channel to hypercapnia and intracellular acidosis.