Learner-to-learner visual acuity screening: a solution for early identification of visual acuity disabilities.

BACKGROUND: The National School Health Policy guidelines (2002) stipulate that primary school learners should have their vision, speech, hearing, mental health, teeth, nutrition and development screened annually. In reality, especially in under-resourced areas such as the Eastern Cape, many learners with disabilities are not identified, with profound consequences for their ability to learn. METHOD: This article describes a cost-effective and community-empowering solution, Learner-to-Learner Visual Acuity Screening, whereby secondary school learners were trained to conduct basic visual acuity (VA) eye screening for foundation-phase learners. RESULTS: Of a group of Grade R learners, 30% were identified as having impaired VA and referred for ophthalmic or optometric evaluation. CONCLUSIONS: This project created greater awareness among learners, parents and teachers regarding abnormal VA and increased interaction between secondary and primary school learners. This simple and cost-effective strategy could be easily and effectively replicated in other schools, helping to address the need for basic eye care.

Adaptation of continuous-flow cavity ring-down spectroscopy for batch analysis of δ13C of CO2 and comparison with isotope ratio mass spectrometry.

Measurements of δ(13)C in CO(2) have traditionally relied on samples stored in sealed vessels and subsequently analyzed using magnetic sector isotope ratio mass spectrometry (IRMS), an accurate but expensive and high-maintenance analytical method. Recent developments in optical spectroscopy have yielded instruments that can measure δ(13)CO(2) in continuous streams of air with precision and accuracy approaching those of IRMS, but at a fraction of the cost. However, continuous sampling is unsuited for certain applications, creating a need for conversion of these instruments for batch operation. Here, we present a flask (syringe) adaptor that allows the collection and storage of small aliquots (20-30 mL air) for injection into the cavity ring-down spectroscopy (CRDS) instrument. We demonstrate that the adaptor's precision is similar to that of traditional IRMS (standard deviation of 0.3‰ for 385 ppm CO(2) standard gas). In addition, the concentration precision (±0.3% of sample concentration) was higher for CRDS than for IRMS (±7% of sample concentration). Using the adaptor in conjunction with CRDS, we sampled soil chambers and found that soil-respired δ(13)C varied between two different locations in a piñon-juniper woodland. In a second experiment, we found no significant discrimination between the respiration of a small beetle (~5 mm) and its diet. Our work shows that the CRDS system is flexible enough to be used for the analysis of batch samples as well as for continuous sampling. This flexibility broadens the range of applications for which CRDS has the potential to replace magnetic sector IRMS.

Synthesis of copper octabromotetracarboranylphenylporphyrin for boron neutron capture therapy and its toxicity and biodistribution in tumour-bearing mice.

Copper tetracarboranyltetraphenylporphyrin (CuTCPH) is a minimally toxic carborane-containing porphyrin that has safely delivered high concentrations of boron for experimental boron neutron capture therapy (BNCT). Copper octabromotetracarboranylphenylporphyrin (CuTCPBr), synthesized by bromination of CuTCPH, is one of several new minimally toxic analogues of CuTCPH being studied in our laboratory, which could possess comparable or better tumour-targeting properties with enhanced tumour cytotoxicity. Its biodistribution, biokinetics and toxicity in mice with subcutaneous EMT-6 (mammary) or SCCVII (squamous cell) carcinomas were compared with those of CuTCPH. The administration of approximately 200 mg kg(-1) of either porphyrin in six intraperitoneal injections over 2 days had no apparent effect, but administration of approximately 400 mg kg(-1) slightly lowered body weights, elevated alanine and aspartate transaminase activities in blood plasma, and depressed blood platelet counts for several days. Enzymes and platelets returned to normal within 5 days after those injections and body weights returned to normal within 2 weeks. High average concentrations of boron from either porphyrin were achieved in the two tumour models from a total dose of approximately 200 mg kg(-1). The high tumour boron concentration decreased slowly while concentrations in blood decreased rapidly. Boron concentrations in brain and skin were consistently lower than in tumour by a factor of 10 or more. Although either CuTCPH or CuTCPBr can be labelled with (64)Cu for imaging by positron emission tomography (PET), CuTCPBr can also be labelled by (76)Br, another PET-imageable nuclide.

Cell damage excites nociceptors through release of cytosolic ATP.

The release of cytosol from damaged cells has been proposed to be a chemical trigger for nociception. K(+), H(+), adenosine triphosphate (ATP), and glutamate are algogenic agents within cytosol that might contribute to such an effect. To examine which, if any, compounds in cytosol activate ion channels on nociceptors, we recorded currents in dissociated nociceptors when nearby skin cells were damaged. Skin cell damage caused action potential firing and inward currents in nociceptors. Extracts of fibroblast cytosol did the same. Virtually all response to extract and cell killing was eliminated by enzymatic degradation of ATP or desensitization or blockade of P2X receptors, ion channels that are activated by extracellular ATP. Thus, if cytosol provides a rapid nociceptive signal from damaged tissue, then ATP is a critical messenger and P2X receptors are its sensor.

Alternative indications for laser-assisted tympanic membrane fenestration.

BACKGROUND AND OBJECTIVE: To assess the utility of the CO(2) Flashscanner laser for treatment of selected middle ear diseases other than otitis media with effusion (OME) and acute otitis media (AOM). STUDY DESIGN/MATERIALS AND METHODS: A retrospective review of the records of 144 patients treated with the OtoLAM((R)) device, a Flashscanner laser, between July 1, 1998, and February 29, 2000. Patients treated for AOM or OME were excluded. RESULTS: Data are presented on 11 patients (17 ears). Four indications were identified: Elimination of middle ear fluid before auditory brainstem response with or without otoacoustic emission testing (ABR +/- OAE), barotrauma, eustachian tube obstruction, tympanocentesis when a culture of middle ear fluid was deemed necessary. All tympanic membranes (TM) healed. CONCLUSIONS: Fenestration of the TM can be accomplished for both diagnostic and therapeutic purposes. Laser assisted tympanic membrane fenestration seems to be effective in the management of middle ear fluid before ABR +/- OAE, barotrauma, eustachian tube dysfunction, and for tympanocentesis.

Effectiveness of adenoidectomy and laser tympanic membrane fenestration.

OBJECTIVE: Adenoidectomy alone or with tonsillectomy (A+/-T) is an effective surgical intervention in the management of otitis media in children, especially when it is performed in conjunction with insertion of pressure equalization tubes (PETs). Otorrhea and persistent tympanic membrane (TM) perforation are frequent complications. This study evaluates the effectiveness of intermediate duration middle ear ventilation using laser tympanic membrane fenestration (LTMF) without tube insertion and as an adjunct to adenoidectomy in resolving middle ear disease within the first 90 days after surgery. STUDY DESIGN: This pilot study was a multicenter, prospective clinical cohort trial. Institutional review board approval and informed consent were obtained. The study involved four tertiary care pediatric otolaryngology departments. Fifty children (96 ears) were treated with LTMF in conjunction with A+/-T from June 1, 1998, through March 30, 1999. Ages ranged from 9 months to 12 years. Patients undergoing A+/-T who would have been recommended for PET insertion instead underwent middle ear ventilation with LTMF using the Oto-LAM device (ESC/Sharplan, Yokneam, Israel). Patients were seen at 30, 60, and 90 days postoperatively. Resolution of otitis media with effusion was determined by clinical examination, which included pneumatic otoscopy, audiometry, and tympanometry. RESULTS: Of the treated ears, 88%, 86%, and 83% had clinical resolution of middle ear disease at 30, 60, and 90 days, respectively. Preoperatively, 45% (n = 85) of ears had normal hearing; 92% (n = 49) had normal hearing at 90 days. Eighty-nine percent (n = 92) had type C2 or B tympanograms preoperatively, and 12% (n = 60) had type C2 or B at 90 days. CONCLUSION: Laser tympanic membrane fenestration in conjunction with adenoidectomy was effective in restoring normal middle ear function at 90 days post-treatment in greater than 80% of children who otherwise may have had placement of PETs.

The role of explicit memory processes in cross-modal priming: an investigation of stem completion priming in amnesia.

To clarify the role of explicit memory processes in cross-modal priming, two experiments examined the status of cross-modal stem completion priming in amnesia. Experiment 1 used a standard behavioral paradigm in which stems corresponding to studied and unstudied words were intermixed. Amnesic patients showed intact within- and cross-modal priming, but, in contrast to controls, they recognized very few of their completions as having been on the study list. This finding suggests that memorial awareness is not necessary for cross-modal priming to occur. Experiment 2 used a paradigm modeled after functional imaging studies, in which stems corresponding to studied and unstudied words were blocked. Amnesic patients showed intact within-modal priming, but impaired cross-modal priming. This finding is consistent with the notion that a blocked format induces voluntary retrieval strategies in normal participants.

Postoperative bilevel positive airway pressure ventilation after tonsillectomy and adenoidectomy in children--a preliminary report.

Obstructive sleep apnea (OSA) in children, characterized by hypoventilation secondary to upper airway obstruction, often results from tonsil and adenoid hypertrophy. Adenotonsillectomy is the standard therapy in this patient population. The immediate postoperative period is complicated occasionally by respiratory difficulties that may require intubation and mechanical ventilation. Recently, physicians have provided temporary airway support using continuous and bilevel positive airway pressure (BiPAP) devices. Reported complications of positive airway pressure devices include local abrasions to the nose and mouth; dryness of the nose, eyes, and mouth; sneezing; nasal drip, bleeds, and congestion; sinusitis; increased intraocular pressure; non-compliance; and pneumocephalus. Subcutaneous emphysema following facial trauma, dental extractions, adenotonsillectomy, and sinus surgery has been reported. There is also a hypothetically increased risk of subcutaneous emphysema following the use of positive airway pressure ventilation in the tonsillectomy patient. Between January 1997 and July 1998, 1321 patients underwent tonsillectomy and/or adenoidectomy at our institution. In reviewing the records of all pediatric intensive care unit admissions during that time period, we identified nine patients, of the 1321, who required BiPAP postoperatively. Of these, four children were obese, four had preexisting neurological disorders, and one underwent endoscopic sinus surgery and adenoidectomy. Three children were asthmatic, and three were less than 3 years of age. Two obese children were discharged with home BiPAP, one of whom had been on BiPAP prior to surgery. All patients tolerated BiPAP without complications. This preliminary report suggests that BiPAP is a safe and effective method of respiratory assistance in the adenotonsillectomy patient with preexisting conditions who is predisposed to postoperative airway obstruction. Furthermore, with BiPAP, the risks of intubation and ventilator dependence are avoided.

A memory for extracellular Ca2+ by speeding recovery of P2X receptors from desensitization.

Nerve endings of nociceptors (pain-sensing neurons) express an unusual subtype of ATP-gated ion channel, the P2X3 receptor, that rapidly desensitizes (<100 msec) and slowly recovers (>20 min). Here we show that Ca2+, or certain other polyvalent cations, binds to an extracellular site on rat sensory neurons and can increase current through P2X3 channels more than 10-fold. Importantly, Ca2+ facilitates P2X3 current to precisely the same level whether a transient Ca2+ change occurred just before or several minutes before activating the channels with ATP. This memory for past changes in Ca2+ is integrative in that a 90 sec Ca2+ stimulus delivered just before an ATP application has the same effect as an earlier series of three, separated 30 sec Ca2+ stimuli. These diverse phenomena are explained by a single mechanism: Ca2+ speeds recovery of P2X channels from desensitization. Recovery follows an exponential growth curve that depends on the duration, but not the timing, of changes in recovery rate. Modulation of desensitization underlies a well described short-term memory in bacteria, and it might be similarly used in the nervous system.

Obstructive sleep apnea in Schwartz-Jampel syndrome.

Schwartz-Jampel syndrome (SJS) is a rare entity characterized by myotonia and skeletal abnormalities. Death and respiratory distress have previously been reported in newborns and young children with SJS. We describe a patient with SJS and snoring in whom polysomnography demonstrated obstructive sleep apnea and hypoxia. Although tonsillectomy with laser palatoplasty significantly widened the oropharyngeal introitus, obstructive sleep apnea persisted. Ultimate improvement occurred only after the institution of home therapy with bi-level positive airway pressure during the night. We also discuss the specific structural and neuromuscular features of SJS that may be responsible for upper airway obstruction.

Desensitization, recovery and Ca(2+)-dependent modulation of ATP-gated P2X receptors in nociceptors.

We have shown the presence and activity of ATP-gated ion channels (P2X receptors) in nociceptive nerve endings, supporting the theory that these channels mediate some forms of nociception [Cook S.P., Vulchanova L., Hargreaves K. M., Elde R. and McCleskey E. W. (1997) Distinct ATP receptors on pain-sensing and stretch-sensing neurons. Nature 387, 505-508]. The kinetics and pharmacology of ATP-gated currents in nociceptors suggest that the channels are comprised of either homomeric or heteromeric combinations of P2X3 receptors. Consistent with the diverse nature of P2X structure, electrophysiological responses of rat tooth-pulp nociceptors fall into two distinct classes based on desensitization and recovery kinetics. Here, we quantified the dramatic differences in desensitization kinetics of transient and persistent currents. The major component of transient P2X current desensitized with a tau decay = 32 +/- 2 msec, while persistent current desensitized > 100-fold more slowly, tau decay = 4000 +/- 320 msec. Both currents recovered from desensitization in minutes: tau recovery = 4 min for transient current, and tau recovery = 0.7 +/- 0.2 min for persistent current. Persistent current recovery was often accompanied by a current "overrecovery" that averaged ca threefold magnitude prior to desensitization. Comparison of ATP current in elevated Ca2+ext also revealed differences in transient and presistent currents. In 2 mM Ca2+ext medium, decrease of Na+ext resulted in an almost complete reduction of persistent, but not transient, current. Subsequent elevation of Ca2+ext greatly increased the transient, but not persistent, current. Mechanistic explanations for either the increase in transient current magnitude by elevated Ca2+ext, or persistent current overrecovery may reflect endogenous pathways for P2X receptor modulation.

The use of the salivagram in the evaluation of severe and chronic aspiration.

Chronic salivary aspiration may be responsible for a significant percentage of pneumonia in the neurologically impaired child. The radionuclide salivagram (RS), a simple investigative study, can document salivary aspiration as the source of pulmonary contamination. The purpose of this study was to determine if the results of the RS would accurately identify children with severe and chronic salivary aspiration who would benefit from laryngotracheal separation (LTS). We reviewed 30 records of children with chronic aspiration pneumonitis who underwent LTS between 1988 and 1996. We recorded the number of inpatient days required for respiratory infections before and after LTS. This number was compared with the number of inpatient days for respiratory infection from children (n = 27) who underwent the RS during a ten-month period but who were never referred for LTS. Fifteen children who underwent LTS had a preoperative RS. The RS documented salivary aspiration in 11 of these children. Aspiration was effectively controlled by LTS for this group. There were three studies that failed to show either aspiration or progression of the Technetium 99m sulfur colloid (Tc 99m SC) into the esophagus This finding was felt to represent significant swallowing dysfunction and, therefore, was also considered a positive finding. There was a significant difference in the number of inpatient days for children who had a negative RS and were never referred for LTS when compared with the number of inpatient days for those children who had a positive RS and were referred for LTS. We feel that the RS is an effective tool to document salivary aspiration as the source of recurrent pneumonia. A modification of the technique and interpretation of RS is suggested.

Lyme disease and seventh nerve paralysis in children.

PURPOSE: This study was undertaken to determine the frequency of Lyme disease (LD) as a cause of transient facial nerve palsy (FNP) in children. Acute onset FNP in children has been primarily associated with acute otitis media (AOM). Recently, LD has emerged in regions where the deer-tick vector is present and has been associated with multiple cranial neuropathies. PATIENTS AND METHODS: Fifty children with transient FNP were evaluated and treated at our institution over a 5.5-year period. RESULTS: The rank of etiologies confirmed LD to now be the most common (50%), followed by AOM (12%), varicella (6%), Herpes zoster (4%), and coxsackievirus (2%). Thirteen children (26%) had idiopathic FNP consistent with Bell's palsy. CONCLUSION: We conclude that transient FNP in children is most commonly caused by LD for regions with endemic infections caused by Borrelia burgdorferi.

Mu and delta opioids but not kappa opioid inhibit voltage-activated Ba2+ currents in neuronal F-11 cell.

Whole-cell patch-clamp recordings were used to study Ba2+ currents through voltage-dependent Ca2+ channels in dorsal root ganglion x mouse neuroblastoma hybrid (F-11) cells. Opioid agonists selective for either mu (Tyr-D-Ala-Gly-Mephe-Gly-ol; DAMGO) or delta (Tyr-D-Pen-Gly-Phe-D-Pen-OH; DPDPE) receptors inhibited high-threshold Ba2+ currents. The inhibition was reversible, naloxone-sensitive, and dose-dependent. The inhibitory effects of both DAMGO and DPDPE were blocked by pretreatment of the cells with pertussis toxin (PTX) as well as by brief exposure to the sulfhydryl alkylating agent, N-ethylmaleimide (NEM). The N-type Ca2+ channel antagonist omega-conotoxin GVIA (omega-CTX GVIA) irreversibly inhibited high threshold Ba2+ currents by 66% and blocked the inhibitory effect of DAMGO or DPDPE. In contrast, the L-type Ca2+ channel blocker nifedipine inhibited high threshold Ba2+ currents by 15% and failed to block the inhibitory effect of DAMGO or DPDPE. These results demonstrate that mu and delta opioid receptors are negatively coupled to N-type Ca2+ channels via PTX- and NEM-sensitive GTP-binding proteins in F-11 cells.

Distinct ATP receptors on pain-sensing and stretch-sensing neurons.

The initial pain from tissue damage may result from the release of cytoplasmic components that act upon nociceptors, the sensors for pain. ATP was proposed to fill this role because it elicits pain when applied intradermally and may be the active compound in cytoplasmic fractions that cause pain. Moreover, ATP opens ligand-gated ion channels (P2X receptors) in sensory neurons and only sensory neurons express messenger RNA for the P2X3 receptor. To test whether ATP contributes to nociception, we developed a tissue culture system that allows comparison of nociceptive (tooth-pulp afferent) and non-nociceptive (muscle-stretch receptor) rat sensory neurons. Low concentrations of ATP evoked action potentials and large inward currents in both types of neuron. Nociceptors had currents that were similar to those of heterologously expressed channels containing P2X3 subunits, and had P2X3 immunoreactivity in their sensory endings and cell bodies. Stretch receptors had currents that differed from those of P2X3 channels, and had no P2X3 immunoreactivity. These results support the theory that P2X3 receptors mediate a form of nociception, but also suggest non-nociceptive roles for ATP in sensory neurons.

Prevention and management of aerodigestive foreign body injuries in childhood.

Pediatricians have a critical role in the evaluation of children who experience a choking episode and foreign body injury. Familiarity with important symptoms and signs improves diagnostic skills and complements radiographic evaluation. Further reduction in injury prevention is assisted by parental education and avoidance of objects and foods that produce the greatest risk. Design modifications of toys and other products for children's use is the next important step in this safety process.