Urinary outputs of oxalate, calcium, and magnesium in children with intestinal disorders. Potential cause of renal calculi

24-hour urinary outputs of oxalate, calcium, and magnesium have been determined in a total of 62 children aged 3 months to 17 years who fell into the following groups: (i) 16 normal controls, (ii) 3 with primary hyperoxaluria, (iii) 9 with small and/or large intestinal resections, (iv) 9 with untreated coeliac disease, (v) 5 with pancreatic dysfunction, and (vi) a miscellaneous group of 20 children with a variety of intestinal disorders. Taken as a whole, 58% of patients with intestinal disorders had hyperoxaluria, and of these 7% had urinary outputs of oxalate which fell within the range seen in primary hyperoxaluria. The proportion of children with hyperoxaluria in the different diagnostic groups was as follows: intestinal resections (78%), coeliac disease (67%), pancreatic dysfunction (80%), and miscellaneous (45%). 35% of the patients with hyperoxaluria had hypercalciuria, whereas magnesium excretion was normal in all subjects studied. In 2 patients treatment of the underlying condition was accompanied by a return of oxalate excretion to normal. These results indicate that hyperoxaluria and hypercalciuria are common in children with a variety of intestinal disorders, and that such children may be at risk of developing renal calculi without early diagnosis and treatment.     

Bilateral optic pathway glioma with intracranial calcification: Magnetic resonance imaging and magnetic resonance spectroscopy findings

Optic nerve glioma is the most common primary neoplasm of the optic nerve in childhood. It can extend intracranially along the optic pathway (optic pathway glioma). The lesion tends to present with decreased visual acuity in the affected eye, but can cause additional symptoms when it is large. Local involvement within the orbit can be characterized using CT, but MRI is superior in showing the intracranial extent of the lesion. Intracranial calcification in optic pathway glioma is rare. We present a rare case of optic pathway glioma with calcification in the intracranial component. Also, we describe MR spectroscopy (MRS) findings in this case.     

Specific inhibition of N-methyl-D-aspartate receptor function in rat hippocampal neurons by L-phenylalanine at concentrations observed during phenylketonuria

Hippocampal N-methyl-D-aspartate receptors (NMDARs) are thought to be involved in the regulation of memory formation and learning. Investigation of NMDAR function during experimental conditions known to be associated with impaired cognition in vivo may provide new insights into the role of NMDARs in learning and memory. Specifically, the mechanism whereby high concentrations of L-phenylalanine (L-Phe) during phenylketonuria (>1.2 mM) cause mental retardation remains unknown. Therefore, the effects of L-Phe on NMDA-activated currents (I(NMDA)) were studied in cultured hippocampal neurons from newborn rats using the patch-clamp technique. L-Phe specifically and reversibly attenuated I(NMDA) in a concentration-dependent manner (IC(50) = 1.71 +/- 0.24 mM). In contrast, L-tyrosine (L-Tyr), an amino acid synthesized from L-Phe in normal subjects, did not significantly change I(NMDA). Although the L-Phe-I(NMDA) concentration-response relationship was independent of the concentration of NMDA, it was shifted rightward by increasing the concentration of glycine. Consistent with an effect of L-Phe on the NMDAR glycine-binding site, L-Phe (1 mM) did not attenuate I(NMDA) in the presence of D-alanine (10 microM). Furthermore, L-Phe significantly attenuated neither glutamate-activated current in the presence of MK-801, nor current activated by AMPA. The finding that L-Phe inhibits specifically NMDAR current in hippocampal neurons by competing for the glycine-binding site suggests a role for impaired NMDAR function in the development of mental retardation during phenylketonuria and accordingly an important role for NMDARs in memory formation and learning.     

Associative conditioning of the exercise ventilatory response in humans

Repeated hypercapnic exercise augmented the ventilatory response to subsequent trials of exercise alone in running goats and in humans performing arm exercise, suggesting a form of associative conditioning or 'long-term modulation' had taken place. These studies did not include 'control' single stimulus conditioning paradigms. This study demonstrated that ten repeated trials of familiar leg bicycling exercise with dead-space induced hypercapnia also elicited similar significant increases in inspired ventilation (+ 22%; P < 0.009) and tidal volume (VT; + 255 +/- 73 ml(BTPS); mean +/- S.E.M.; P = 0.004) within the first 20 sec of subsequent exercise only trials. Long-term modulation of the early ventilatory response to cycling was not fully replicated by ten trials of 'control' paradigms involving either repeated exercise alone or resting dead space alone. This study thus demonstrated that long term modulation of the early ventilatory response exercise was due to an explicit effect of associative conditioning and not simply sensitisation to repeated trials of a single stimulus.     

Secretory immunoglobulin A in tears: functions and changes during contact lens wear

Introduction : Secretory immunoglobulin A (sIgA) is the predominant immunoglobulin in tears. The role of sIgA in defending the eye against pathogens has not been established clearly. There have been conflicting reports about the effect of contact lens wear on the concentration of sIgA in tears. This study was conducted to elucidate the role of sIgA in ocular defence and to determine the effect of contact lens wear on sIgA concentration. Methods : Tears were collected from contact lens wearers and non-wearers using microcapillary tubes. The concentration of sIgA was evaluated using an in-house ELISA. The specificity of sIgA to a strain of P. aeruginosa was examined using a fluorescent assay and the ability of neutrophils to phagocytose sIgA coated bacteria were assessed by plate counts. Results : Tears contained sIgA that reacted to P. aeruginosa. P. aeruginosa coated with sIgA was phagocytosed by the neutrophils. The level of sIgA and the level of sIgA specific to P. aeruginosa in the tears of contact lens wearers were significantly reduced. Conclusions : These results indicate that contact lens wear significantly alters the level of sIgA in tears which may lead to changes in the ability of the ocular surface to defend itself against potential pathogens.     

Meningitis in Hong Kong children, with special reference to the infrequency of haemophilus and meningococcal infection

Objective: To study the epidemiologic and aetiologic features of meningitis in children in Hong Kong.
Methodology: A retrospective study of 85 children resident in the New Territory East region of Hong Kong admitted to a teaching Hospital because of meningitis during a 9 year period.
Results: Mycobacterium tuberculosis was the most common aetiological agent accounting for 13 cases (15.3%). Other bacteria accounted for 41 cases (48%); among these one fifth were caused by Haemophilus influenzae type b. The overall admission rates for tuberculous meningitis in Chinese children were 0.76/100 000 (95% CI 0.25-1.78) and 0.42/100 000 (CI 0.19-0.8) per year, respectively, for under 5 year olds and under 15 year olds. The overall annual incidence rates of bacterial meningitis other than tuberculous were 5.2/100 000 (CI 3.72-7.43) and 1.6/100 000 (CI 1.14-2.29) for Chinese children under 5 years and under 15 years, respectively. The annual incidence of H. influenzae meningitis in Chinese children under 5 years old was low at 1.1/100 000 (0.43-2.2). All five cases of meningococcal meningitis were in Vietnamese children (under 5 years of age incidence: 13.0/100 000 per year, CI 4.2-30.3). There were no cases of meningococcal meningitis in Chinese children during the 9 year period.
Conclusion: M. tuberculosis was the most common aetiological agent of meningitis in Hong Kong children. The incidence of haemophilus or meningococcal meningitis was very low.     

Effect of respiratory virus infections including rhinovirus on clinical status in cystic fibrosis

One hundred and eight patients with cystic fibrosis were investigated over one year to determine whether an association existed between rhinovirus or other respiratory virus infection and clinical status. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), Shwachman score, Chrispin-Norman chest radiograph score, and percentage weight for height were recorded at the beginning and end of the study; days of intravenous antibiotics were noted. Nasopharyngeal aspirates were taken for viral studies during respiratory exacerbations. Serum was collected at enrollment and 2-6 weeks after each respiratory exacerbation. One hundred and fifty seven exacerbations occurred in 76 patients. Respiratory virus infection was detected in 44 exacerbations and rhinovirus was present in 16% (25/157) of exacerbations. Patients with one or more respiratory virus infections were compared with those who had none. When all respiratory virus infections were considered, patients had a significantly greater deterioration in Shwachman score and received significantly more days of intravenous antibiotics. When rhinovirus was considered separately, patients received significantly more days of intravenous antibiotics, but showed no deterioration in clinical status. However, patients infected with another respiratory virus had a significant decline in FEV1, with trends towards significance for decline in FVC and Shwachman score.     

Spontaneous intracranial hypotension: A study of six cases with MR findings and literature review

Spontaneous intracranial hypotension is clinically characterized by orthostatic headache and other symptoms caused by low cerebrospinal fluid pressure due to leakage of cerebrospinal fluid from dural punctures or other medical causes. The other symptoms are mainly due to traction of the cranial and spinal nerves owing to descent of the brain caused by low cerebrospinal fluid pressure. Magnetic resonance imaging is very useful in the diagnosis because of its characteristic findings. We describe the MRI findings in six cases that had variable clinical presentation.     

Sperm-induced oocyte activation in the rhesus monkey: nuclear and cytoplasmic changes following intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) has increased the potential of the assisted reproductive technologies to propagate mammalian species and has provided an opportunity for research into cell cycle control and the mechanisms involved in sperm-induced oocyte activation. We have investigated the efficacy of ICSI in the rhesus monkey, the mechanism of fertilization following sperm injection and the cytoskeletal rearrangement that occurs upon oocyte activation. These studies were conducted on mature, and to a lesser extent, immature oocytes. Ejaculated spermatozoa, washed, capacitated and activated before immobilization, were injected into oocytes using conventional ICSI methodology. Sperm injection into mature oocytes induced oocyte activation (19/22; 86%) and pronuclear formation. In contrast, sham- injected oocytes did not activate readily (2/16; 13%). To localize oocyte activation factor(s), spermatozoa were separated mechanically into heads and tails which were then injected individually into mature oocytes. Activation occurred in 87% (20/23) of oocytes receiving heads. After tail injection, a single microtubule aster was nucleated and one pronucleus (PN) was seen in four of 21 oocytes. Intracytoplasmic injection of sperm extract (SE) resulted in oocyte activation at a significantly higher rate than occurred following sham injection (76 versus 13%). Sperm-induced oocyte activation was also evaluated in immature metaphase (MI) oocytes; activation occurred in 46% (12/26) of cases; however, only 8% of the activated oocytes exhibited 2 PN. Finally, beta-tubulin localization in untreated and taxol-treated oocytes was established as a marker for cytoplasmic changes associated with oocyte activation. These results are consistent with the hypothesis that spermatozoa contain an oocyte activating factor(s) which is primarily localized in the sperm head. Moreover, an activation response is limited to mature oocytes and is accompanied by cytoskeletal changes analogous to those seen following conventional fertilization.      

Chronotropic effect of angiotensin II via type 2 receptors in rat brain neurons

Previously, we determined that angiotensin II (Ang II) elicits an Ang II type 2 (AT(2)) receptor-mediated increase of neuronal delayed rectifier K(+) (I(KV)) current in neuronal cultures from newborn rat hypothalamus and brain stem. This requires generation of lipoxygenase (LO) metabolites of arachidonic acid (AA) and activation of serine/threonine phosphatase type 2A (PP-2A). Enhancement of I(KV) results in a decrease in net inward current during the action potential (AP) upstroke as well as shortening of the refractory period, which may lead to alterations in neuronal firing rate. Thus, in the present study, we used whole-cell current clamp recording methods to investigate the AT(2) receptor-mediated effects of Ang II on the firing rate of cultured neurons from the hypothalamus and brain stem. At room temperature, these neurons exhibited spontaneous APs with an amplitude of 77.72 +/- 2.7 mV (n = 20) and they fired at a frequency of 0.8 +/- 0.1 Hz (n = 11). Most cells had a prolonged early after-depolarization that followed an initial fully developed AP. Superfusion of Ang II (100 nM) plus losartan (LOS, 1 microM) to block Ang II type 1 receptors elicited a significant chronotropic effect that was reversed by the AT(2) receptor inhibitor PD 123,319 (1 microM). LOS alone had no effect on any of the parameters measured. The chronotropic effect of Ang II was reversed by the general LO inhibitor 5,8,11,14-eicosatetraynoic acid (10 microM) or by the selective PP-2A inhibitor okadaic acid (1 nM) and was mimicked by the 12-LO metabolite of AA 12-(S)-hydroxy-(5Z, 8Z, 10E, 14Z)-eicosatetraynoic acid. These data indicate that Ang II elicits an AT(2) receptor-mediated increase in neuronal firing rate, an effect that involves generation of LO metabolites of AA and activation of PP-2A.