Age dependence of ocular biometric measurements under cycloplegia with tropicamide and cyclopentolate

Background : Cyclopentolate continues to be the cycloplegic of choice for refracting young children, although many studies of ocular biometry promote the use of tropicamide. Methods : To clarify the role of drug type in biometric measurements, cycloplegia was induced in two disparate age groups using cyclopentolate and tropicamide on two separate occasions. Refraction, phakometry and A-scan ultrasonography measurements were made on two groups of Tibetan children resident in Nepal. Results : Cyclopentolate produced significantly more cycloplegia in the younger group, which was supported by phakometry measurements. However, in clinical terms, the difference between the measurements was not significant. Conclusion : We conclude that although cyclopentolate is more effective than tropicamide in relaxing accommodation in young children, the use of a local anaesthetic prior to instillation of tropicamide produces refractive data virtually equivalent to that of cyclopentolate, regardless of the age group measured. However, biometric measurements may be susceptible to greater error when near fixation targets are used during phakometry procedures.     

Bone mineral status in children with phenylketonuria under treatment

Bone mineral status was assessed in 48 children with phenylketonuria (PKU) (20 M, 28 F, aged 2.5-17 y). Bone density was measured in the distal third of the right forearm using single photon absorptiometry and was expressed as ±SD with respect to age- and gender-matched controls. Serum calcium (Ca), magnesium (Mg), phosphorus (P), alkaline phosphatase (ALP), parathyroid hormone and 25-hydroxyvitamin D were measured in morning samples. The ratios of urinary Ca/creatinine (UCa/ UCr), UP/UCr, UMg/UCr and hydroxyproline (OH-Pr)/UCr were calculated in urine samples collected over a period of 3h. Patients' data were compared with those of 50 controls (22M, 28F, aged 3-15y). The data showed severe osteopenia (below -2 SD) in 22/48 patients. Bone loss was more prominent in patients over 8y old. Bone density correlated significantly with age ( r =– 0:56, p < 0.001) and with Phe ( r =– 0:49, p < 0.007) but did not correlate with the other biochemical indices studied. Comparing PKU children with controls, significantly higher serum calcium and magnesium ( p = 0:04, p < 0.001, respectively), lower ALP ( p = 0:01), higher UCa/UCr ratio ( p < 0.001), lower UP/UCr ( p < 0.001) and lower UOH-Pr/UCr ( p < 0.001) were found. Dietary compliance was poor in patients over the age of 8y, as only 3/22 of ≤ 8y had mean serum phenylalanine >10mgdl⁻¹, in contrast to 21/26 in the older group. It is clear from the data that osteopenia is commonly found in PKU patients from early life. The biochemical data indicate a metabolic state of low bone turnover in PKU patients. In conclusion, a better, more restricted diet may correct osteopenia.     

The dexamethasone suppression test in mania

The results of the overnight 2 mg Dexamethasone Suppression Test administered to 50 manic patients are reported. Twenty-three (46%) cases showed an absence of normal suppression, results which are similar to those seen in endogenous depression and which differ to those of others who have all reported normal suppression in mania. Suppressors and non-suppressors were not shown to differ in the factors of age, weight, polarity or the rated severity of mood.     

MOUSE ASTROCYTES POSSESS SPECIFIC ANP RECEPTORS WHICH ARE LINKED TO cGMP PRODUCTION

1. Receptors for atrial natriuretic peptide (ANP) have been identified on mouse astrocytes in primary culture, and have similar characteristics to those found on previously recognized ANP-target tissues. 2. Scatchard analysis revealed one class of high affinity receptors with a Kd of 0.32 nmol/L. The IC50 for specific binding was 0.5 nmol/L. 3. Ligand binding resulted in stimulation of guanylate cyclase. 4. Under reducing conditions, the covalently cross-linked receptor-ANP complex migrated on SDS-polyacrylamide gels as a single band with an apparent molecular weight of 66 kDa. 5. Although the physiological relevance of our observations remains to be determined, these data document that cultured mouse astrocytes contain specific high-affinity ANP receptors which are linked to the production of cGMP.