Potential for bilateral nephrectomy to reduce oxalate release after combined liver and kidney transplantation for primary hyperoxaluria type 1

Primary hyperoxaluria type 1 (PH-1) is frequently associated with end stage renal failure due to urinary calculi, obstructive uropathy and interstitial deposits of calcium oxalate. The currently accepted treatment for PH-1 is liver transplantation to replace the deficient enzyme peroxisomal alanine glycoxylate aminotransferase (AGT) and a simultaneous renal transplant to restore renal function. The transplanted kidney may become significantly impaired or fail when systemic calcium oxalate is eliminated by renal excretion. The native kidneys are a major source of this oxalate. This study was undertaken to determine whether there is a difference in oxalate clearance following combined liver-kidney transplant in patients with PH-1 by comparing the effect of native kidney nephrectomy at the time of transplantation against leaving the native kidneys in situ. Regression analysis was used to compare daily urinary oxalate excretion corrected for body surface area. There was a significant reduction in urinary oxalate excretion (P < 0.05) in the patient who had undergone bilateral nephrectomy compared to the patient whose native kidneys remained in situ for the first 100 d following combined liver and kidney transplantation. No difference was observed in the serum oxalate levels between patients over the same period or in the renal function assessed by creatinine clearance corrected for body surface area. Total body oxalate load was not determined in this study. A larger study should be undertaken to examine the benefits of nephrectomy in reducing oxalate deposition in recently inserted allografts for patients with PH-1.

Oligomerization of expanded-polyglutamine domain fluorescent fusion proteins in cultured mammalian cells

Six inherited neurologic diseases, including Huntington's disease, result from the expansion of a CAG domain of the disease genes to produce a domain of more than 40 glutamines in the expressed protein. The mechanism by which expansion of this polyglutamine domain causes disease is unknown. Recent studies demonstrated oligomerization of polyglutamine-domain proteins in mammalian neurons. To study oligomerization of polyglutamine proteins and to identify heterologous protein interactions, varying length polyglutamine-green fluorescent protein fusion proteins were expressed in cultured COS-7 cells. The 19- and 35-glutamine fusion proteins (non-pathologic length) distributed diffusely throughout the cytoplasm. In contrast, 56- and 80-glutamine fusion proteins (pathologic length) formed fibrillar arrays resembling those previously observed in neurons in Huntington's disease and in a transgenic mouse model. These aggregates were intranuclear and intracytoplasmic. Intracytoplasmic aggregates were surrounded by collapsed intermediate filaments. The intermediate filament protein vimentin co-immunoisolated with expanded polyglutamine fusion proteins. This cellular model will expedite investigations into oligomerization of polyglutamine proteins and their interactions with other proteins.

Phosphorylation and calcium influx are not sufficient for the activation of cytosolic phospholipase A2 in U937 cells: requirement for a Gi alpha-type G-protein

Differentiation with dibutyryl cyclic AMP (dBcAMP) of the human, premonocytic U937 cell line toward a monocyte/granulocyte-like cell results in the cell acquiring an ability to release arachidonate upon stimulation. In contrast, the calcium ionophore ionomycin was able to stimulate phospholipase C, as measured by inositol 1,4,5-trisphosphate formation, to equal extents in both undifferentiated and dBcAMP-differentiated U937 cells. The role and regulation of cytosolic phospholipase A2 (cPLA2) in the production of arachidonate in these cells when either the chemotactic peptide fMLP or ionomycin are used as stimulus were investigated. The ionomycin- and fMLP-stimulated release of arachidonate were sensitive to the cPLA2 inhibitor arachidonyl trifluoromethylketone (IC50 values of 32 and 18 microM, respectively), but were not inhibited by E-6-(bromomethylene)-tetrahydro-3-(1-naphthalenyl)-2 H-pyran-2-one, a bromoenol lactone inhibitor of the calcium-independent phospholipase A2. These results, coupled with the inhibition of ionomycin-induced arachidonate production by electroporation of differentiated cells to introduce an anti-cPLA2, demonstrate that the cPLA2 is the enzyme responsible for arachidonate release in differentiated cells. SDS-PAGE and immunoblot analysis of differentiated cells showed the cells to contain both phosphorylated and unphosphorylated forms of cPLA2 (ratio of about 2: 3). Surprisingly, undifferentiated cells contain 30% more enzyme than differentiated cells and contain a higher percentage (approximately 75%) of the phosphorylated in the absence of stimulation. The inability of undifferentiated cells to produce arachidonate is not due to insufficient intracellular calcium concentrations since ionomycin induces large (820-940 nM) influxes of intracellular calcium in both differentiated and undifferentiated cells. This demonstrates that phosphorylation of cPLA2 andan influx of intracellular calcium are not sufficient to activate the enzyme to produce arachidonate. Instead, activation of a pertussis toxin-sensitive Gi alpha-type G-protein is required as evidenced by the production of arachidonate in undifferentiated cells stimulated with mastoparan, an activator of Gi alpha subunits, in combination with ionomycin. This activation of a Gi alpha-type G-protein is independent of modulations of adenylyl cyclase activity since cellular cAMP levels were not modulated upon treatment with mastoparan and ionomycin.

Multielectrode recordings of tibial nerve H-reflexes at various triceps surae muscle sites in the right and left legs

The purpose of the study was to determine the laterality of tibial nerve H-reflexes recorded at various triceps surae muscle sites. In 10 college-aged adults, maximum H-reflexes and maximum M-waves were measured in the right and left legs from the following bipolar surface elctromyographic (EMG) recording sites: (1) the belly of medial gastrocnemius muscle; (2) the belly of the lateral gastrocnemius muscle; (3) proximal soleus muscle location, 1 cm below the inferior margin of the two heads of gastrocnemius; (4) mid soleus muscle location, 3 cm below the proximal site; and (5) distal soleus muscle location, 3 cm below the mid site. Peak-to-peak EMG values of the evoked muscle responses were analyzed using leg by muscle site repeated measures ANOVA models and linear regression models to determine the laterality of the tibial nerve H-reflex. This multielectrode recording technique indicated that spinal responses evoked in the triceps surae muscle are symmetrical in humans.

Polyglutamine domains are substrates of tissue transglutaminase: does transglutaminase play a role in expanded CAG/poly-Q neurodegenerative diseases?

Huntington's disease and six other neurodegenerative diseases are associated with abnormal gene products containing expanded polyglutamine (poly-Q; Qn) domains (n > or = 40). In the present work, we show that glutathione S-transferase (GST) fusion proteins containing a small, physiological-length poly-Q domain (GSTQ10) or a large, pathological-length poly-Q domain (GSTQ62) are excellent substrates of guinea pig liver (tissue) transglutaminase and that both GSTQ10 and GSTQ62 are activators of tissue transglutaminase-catalyzed hydroxaminolysis of N-alpha-carbobenzoxyglutaminylglycine. The present findings have implications for understanding the pathophysiological mechanisms of expanded CAG/poly-Q domain diseases.

Presence of glycerol masks the effects of phosphorylation on the catalytic efficiency of cytosolic phospholipase A2

Cytosolic phospholipase A2 catalyzes the selective release of arachidonic acid from the sn-2 position of phospholipids and is believed to play a key cellular role in the generation of arachidonic acid. The enzymatic activity of cPLA2 is affected by several mechanisms, including substrate presentation and the phosphorylation state of the enzyme. Using covesicles of 1-palmitoy1-2-arachidonoyl-[arachidonoyl-1-14C]-8n-glycero-3 -phosphocholine and 1,2-dimyristoyl-phosphatidylmethanol as substrate, the effects of phosphorylation on the interfacial binding and catalytic constants were investigated. Phosphorylated and dephosphorylated enzyme forms were shown to have identical values of 2.6 microM for KMapp, an equilibrium dissociation constant which consists of the intrinsic dissociation constant from the lipid/water interface (Ks) and the dissociation constant for phospholipid from the active site (KM*). Moreover, the values of KM* for phosphorylated and dephosphorylated enzyme did not differ significantly (0.4 +/- 0.1 and 0.2 +/- 0.1, respectively). However, dephosphorylation of the enzyme reduced the value of kcat by 39%. The phosphorylation state of the enzyme had no effect on either the cooperativity shown by this enzyme or the thermal stability of the enzyme. Surprisingly, the presence of glycerol (4 M) masks the effect of phosphorylation on kcat. Instead, glycerol increased the value of kcat by 440% for the phosphorylated enzyme and by 760% for the dephosphorylated form. Moreover, addition of glycerol had only small effects on KMapp. the increase in the kcat upon addition of glycerol results from a substantial decrease in the activation energy from 29.4 to 14.8 kcal. mol-1. To determine whether the effects of phosphorylation of the enzyme or addition of glycerol are unique to this artificial substrate, membranes from U937 cells were isolated and used as substrate. With these membranes, the dephosphorylated enzyme was only 21% less active than the phosphorylated enzyme. In the presence of glycerol, there was no detectable difference the two enzyme forms, and the rate of hydrolysis was increased by 300-390% over that measured in the absence of glycerol. These results suggest that the catalytic efficiency of the phosphorylated enzyme is not particularly relevant to its activation in vivo. Moreover, it may be that glycerol is mimicking the effect of some unidentified factor which greatly enhances the catalytic efficiency of the enzyme.

Toxicity of expanded polyglutamine-domain proteins in Escherichia coli

Five neurodegenerative diseases are caused by proteins with expanded polyglutamine domains. Toxicity of these proteins has been previously identified only in mammals, and no simple model systems are available. In this paper, we demonstrate in E. coli that long polyglutamine domains (59-81 residues) as GST-fusion proteins inhibit growth while smaller glutamine (10-35 residues) or polyalanine (61 residues) domains have no effect. Analogously in humans, polyglutamine repeats less than 35-40 glutamines produce a normal phenotype, while expansion greater than 40 glutamines is always associated with disease. Expression of polyglutamine proteins in E. coli may help identify the molecular mechanism of pathogenesis of CAG trinucleotide repeat diseases and be a useful screen to identify potential therapeutic compound.

The influence of age on the assessment of motor unit activation in a human hand muscle

Two indices of motor unit recruitment, the ramp-force and repetitive-discharge thresholds, were compared in the first dorsal interosseus muscle of ten young and twelve elderly subjects. The purpose was to determine the effect of age on the relationship between the two recruitment thresholds and the spike-triggered average force of motor units. Each subject performed three tasks requiring isometric abduction of the left index finger: a maximum voluntary contraction (MVC), a ramp-and-hold contraction, and a repetitive-discharge task. The elderly subjects used coactivation of the antagonist muscle (second palmar interosseus) more frequently than the young subjects during the ramp-and-hold contraction. Many elderly subjects expressed difficulty with the controlled ramp-down phase of the ramp-and-hold contraction and preferred a coactivation strategy to a derecruitment strategy for this task. There were no differences due to age or gender in the ramp-force thresholds between the various groups. However, the normalized repetitive-discharge threshold was significantly less for the younger subjects and for the male subjects. Nonetheless, the two recruitment thresholds were able to predict the spike-triggered average force with similar success for both the young and the elderly subjects. These data suggest that the recruitment threshold of a motor unit in first dorsal interosseus was characterized equally well by either the ramp-force or repetitive-discharge measurement for both young and elderly subjects but that coactivation was used more frequently by the elderly subjects during the ramp-and-hold task.

Survey of haemolytic-uraemic syndrome in Queensland 1979-1995

OBJECTIVE

To review the clinical course of haemolytic-uraemic syndrome (HUS) in children admitted to Brisbane children's hospitals between April 1979 and October 1995.

DESIGN

Retrospective case survey.

SETTING

Royal Children's Hospital and Mater Misericordiae Children's Hospital (the two major children's hospitals in Brisbane).

SUBJECTS

All children hospitalised for HUS.

OUTCOME MEASURES

Clinical and laboratory features on presentation (including typical [diarrhoea-positive, D+] or atypical [diarrhoea-negative, D-] presentation), clinical course, treatment and features on subsequent outpatient follow-up (1, 3, 6 and 12 months later), renal outcome on long term follow-up (3-16 years later).

RESULTS

55 children (aged 2 months to 13 years) were hospitalised for HUS, but no epidemic was detected. Seven children (13%) had D- presentations, including three (5%) with T-activation caused by pneumococcal pneumonia. Thrombocytopenia was more severe and prolonged in D- patients (P < 0.01). Major complications occurred only in the D+ group (one patient died, and two had recurrences). Chronic renal failure was significantly more likely in patients with prolonged oliguria or hypertension in the acute illness and proteinuria or hypertension on follow-up.

CONCLUSIONS

The clinical course and outcome in childhood HUS vary greatly and D- HUS is not invariably associated with a poorer prognosis than D+ HUS. Pneumococcal-associated T-activation is an important cause of D- HUS and should be actively sought to allow for appropriate therapy.

Prednisolone and cellulose phosphate treatment in idiopathic infantile hypercalcaemia with nephrocalcinosis

A girl presented at the age of 8 months with idiopathic infantile hypercalcaemia complicated by hypercalciuria, nephrocalcinosis and failure to thrive. Her hypercalcaemia was partially corrected by prednisolone, but resolved with the addition of cellulose phosphate. Her height and weight showed significant improvement during the treatment period. Cellulose phosphate should be considered in the management of children with idiopathic infantile hypercalcaemia and nephrocalcinosis.

Specificity, sensitivity, and predictive value of apolipoprotein-E genotyping for sporadic Alzheimer's disease

BACKGROUND

We aimed to determine the specificity, sensitivity, and predictive value of apolipoprotein E (APOE) genotyping in 67 consecutive patients with clinical diagnoses of sporadic Alzheimer's disease (AD) who underwent necropsy.

METHODS

We studied patients who attended the Duke Memory Disorders Clinic and were diagnosed as having probable AD. These patients were followed up until they died. APOE genotyping was done during life in most cases, but in some brain tissue obtained at necropsy was used. Members of known AD families were excluded.

FINDINGS

After neuropathological examination 57 (85%) of 67 of our patients were confirmed as having AD including all 43 who had at least one APOE-epsilon 4 allele. None of the patients found not to have AD carried an epsilon 4 allele. In this series, the specificity of the epsilon 4 allele was 100%, the sensitivity 75%, the positive predictive value 100%, and the negative predictive value 42%. In this necropsy-confirmed series, the epsilon 4/epsilon 4 genotype predicted AD with 100% accuracy. The epsilon 3/epsilon 4 and epsilon 2/epsilon 4 genotypes were also unexpectedly highly specific for AD.

INTERPRETATION

Data from hundreds of necropsy-confirmed non-AD patients in other longitudinal necropsy series will allow the predictive value of APOE genotypes to be assessed with useful confidence limits.

Age-dependent effects of muscle vibration and the Jendrassik maneuver on the patellar tendon reflex response

OBJECTIVE

To explore possible effects of aging on the excitability of spinal reflexes.

DESIGN

Using a cross-sectional design, the influences of muscle vibration and the Jendrassik maneuver on patellar tendon reflex function were compared between 30 young adults and 15 older adults.

SETTING

Motor control research laboratory.

SUBJECTS

The young adults were volunteers of college age. The older adults (74.5 +/- 4.14 yr) were volunteers from the local community. All subjects were free of medications and neurological conditions that would affect normal neuromuscular responses.

MAIN OUTCOME MEASURES

A force-time curve analysis of the patellar tendon reflex response was used to assess the inhibition and facilitation of spinal reflexes. In the experimental protocol to assess spinal reflex inhibition, 100 Hz vibration was applied to the right quadriceps muscle. In another experimental protocol, spinal reflex facilitation was assessed using the Jendrassik maneuver. To perform the Jendrassik maneuver, subjects were instructed to grasp their hands together and to pull as hard as possible while breathing normally. After a 2-second count, the tendon tap was delivered to the right leg and the subject was instructed to relax. In both experimental protocols, control patellar tendon reflexes were collected.

RESULTS

Analysis of variance for reflex peak force revealed a significant 30% reduction in the amount of vibration-induced reflex inhibition with increasing age, and a similar 33% reduction in the amount of Jendrassik maneuver facilitation observed for the older adults as compared with the younger adults.

CONCLUSION

These results support the hypothesis that inhibitory and excitatory influences acting on the alpha motoneuron pool are different in young and older adults.

Loin pain haematuria syndrome

Loin pain haematuria syndrome is a descriptive diagnosis of recurrent episodes of loin pain accompanied by haematuria, in which investigations do not reveal adequate pathology to account for the symptoms. The majority of patients present between 20 and 40 years, but onset may occur in older children. A significant number of patients show psychological and psychopathological features. Renal histology may show minor abnormalities, including mesangial proliferation, arteriolar and arterial hyalinosis and C3 in arterioles. Renal angiography is often normal but changes in intrarenal arterioles and cortical infarcts may be seen. Haematological abnormalities include decreased heparin-thrombin clotting time and elevated free plasma serotonin concentration. It is important that the assessment include a detailed psychiatric history, the patient's perception of pain, and the psychosocial environment. The pain may be very severe, leading to the requirement for addictive analgesics: management often becomes very difficult and frustrating to medical practitioners. Surgical intervention with capsulotomy, denervation and autotransplantation should only be considered as a last resort, as there is frequent recurrence of pain on the same or contralateral side.

Huntingtin and DRPLA proteins selectively interact with the enzyme GAPDH

At least five adult-onset neurodegenerative diseases, including Huntingtin disease (HD), and dentatorubral-pallidoluysian atrophy (DRPLA) are produced by genes containing a variably increased CAG repeat within the coding region. The size range of the repeats is similar in all diseases; unaffected individuals have fewer than 30 CAG repeats, whereas affected patients usually have more than 40 repeats. The size of the inherited CAG repeat correlates with the severity and age of disease onset. The CAG triplet repeat produces a polyglutamine domain in the expressed proteins. All of these diseases are inherited in a dominant fashion, and a pathologic gain of function in gene carriers has been proposed. We sought to identify proteins in the brain that selectively interact with polyglutamine-domain proteins, hypothesizing that the polyglutamine domain may determine protein-protein interactions.

Changes in spinal reflexes preceding a voluntary movement in young and old adults

BACKGROUND

Age-related differences in spinal excitability during response preparation were assessed by eliciting either a 50% H-reflex or an Achilles tendon reflex preceding the onset of a right plantar flexion contraction in 20 young adults (23.1 +/- 1.64 yrs) and 20 old adults (68.5 +/- 5.53 yrs).

METHODS

On each simple reaction time trial, the test reflex was elicited at a specific test interval during either the foreperiod or the response period. The foreperiod test intervals were 500, 600, 700, 800, 900, and 1000 msec after the presentation of the warning stimulus. The response period test intervals were 50, 100, 150, 200, 250, and 300 msec after the presentation of the response stimulus. Control reflexes were randomly elicited between the simple reaction time trials.

RESULTS

Changes in reflex excitability were not observed during the foreperiod in either age group. During the response period, the percentage of H-reflex facilitation as compared to control H-reflexes was similar for the young (68%) and the old (61%) adults, but the magnitude of Achilles tendon reflex facilitation with respect to control reflex responses was greater in the young adults (74%) than in the old adults (38%). The time course of H- and tendon reflex facilitation was delayed in the old group during the response period.

CONCLUSIONS

The results indicate that processes underlying the preparation and generation of a motor response are similar in young and old adults. However, these processes occur at a slower rate in old adults.

Cooperativity and binding in the mechanism of cytosolic phospholipase A2

Cytosolic phospholipase A2 (cPLA2) hydrolyzes the sn-2 ester of phospholipids and is believed to be responsible for the receptor-regulated release of arachidonic acid from phospholipid pools. The enzyme was assayed using vesicles containing arachidonate-containing phospholipid substrate, such as 1-palmitoyl-2-arachidonoylphosphatidylcholine (PAPC) or 1-stearoyl-2-arachidonoylphosphatidylinositol (SAPI), dispersed within vesicles of 1,2-dimyristoylphosphatidylmethanol (DMPM). We report here that the enzyme shows an apparent cooperative effect with respect to the mole fraction of arachidonate-containing phospholipids within these covesicles. The data can be fit to a modified Hill equation yielding Hill coefficients, n, of 2-3. This effect is unusual in that it is dependent on the nature of the sn-2 ester as opposed to the phosphoglycerol head group. This cooperativity is independent of both the concentration of glycerol, which greatly increases enzyme activity and stability, and the concentration of calcium, which facilitates the fusion of the covesicles. Surprisingly, 1-palmitoyl-2-arachidonoylphosphatidylethanolamine (PAPE) does not show the same cooperative effect, although the rate at which it is hydrolyzed is much greater when PAPC is present. Moreover, PAPE has a dissociation constant from the active site (KD* = 0.7 mol %) which is comparable to that of PAPC and SAPI (KD* values of 0.3 and 0.3 mol %, respectively). These results are consistent with the presence of an allosteric site that, when occupied, induces a change in the enzyme which facilitates enzymatic hydrolysis. If so, PAPC and SAPI, but not PAPE, must be able to bind to this allosteric site. Alternatively, this effect may result from changes in the physical nature of the bilayer which result upon increasing the bilayer concentration of arachidonate-containing phospholipids. This previously unobserved effect may represent another mechanism by which cells can regulate the activity of cPLA2.

Low-dose subcutaneous recombinant erythropoietin in children with chronic renal failure. Australian and New Zealand Paediatric Nephrology Association

In a multicentre trial, low-dose subcutaneous recombinant human erythropoietin (r-Hu EPO) was evaluated in 22 children aged 4 months to 16 years with anaemia of chronic renal failure over a 12-month period. A starting dosage of 50 U/kg twice weekly was given until a target haemoglobin of 9-11 g/dl was achieved. The dosage was increased by 50 U/kg per week, each 4 weeks, if the haemoglobin did not increase by 1 g/dl per month. When the target haemoglobin was achieved, the same weekly dosage was given as a single injection. After 10 weeks, the mean haemoglobin increased from 6.7 +/- 0.7 to 9.6 +/- 1.9 g/dl (P < 0.001) and the haematocrit from 19.8% +/- 2.4% to 29.3% +/- 6.3% (P < 0.001). By 4 months the target haemoglobin was achieved in 19 patients on 50 U/kg twice weekly and 1 patient on 75 U/kg twice weekly. Two children with severe renal osteodystrophy failed to respond to 95 U/kg and 150 U/kg twice weekly. The maintenance weekly dose of r-Hu EPO in 9 children over 4-12 months ranged between 45 and 125 U/kg. The Wechsler intelligence score increased in 11 children from 92 +/- 16 to 97 +/- 17 over the 12-month period (P = 0.007). No adverse effects were recorded. A starting dose of r-Hu EPO of 50 U/kg subcutaneously twice weekly is recommended as effective and safe for the majority of children with anaemia of chronic renal failure.

A comparison of amitriptyline, vasopressin and amitriptyline with vasopressin in nocturnal enuresis

Forty-five children aged 6-14 years with primary nocturnal enuresis were randomised to determine whether desmopressin is more effective than amitriptyline and whether the combination of amitriptyline/desmopressin is more effective than amitriptyline or desmopressin alone. Amitriptyline dosage was 25 mg for children 6-10 years and 50 mg for children aged 10-14 years. Desmopressin (20 micrograms) was given in the same dosage for all age groups. After a run-in period of 2 weeks, children were treated for 16 weeks and then observed for 12 weeks. In the amitriptyline group mean wet nights per week decreased from 5.8 +/- 0.9 to 3.3 +/- 1.9 (P < 0.0005); in the desmopressin group mean wet nights per week decreased from 6.0 +/- 0.9 to 4.7 +/- 1.7 (P < 0.02); in the amitriptyline/desmopressin group mean wet nights per week decreased from 6.3 +/- 0.9 to 3.3 +/- 2.5 (P < 0.0006). When comparing the groups, amitriptyline/desmopressin and amitriptyline were statistically more effective than desmopressin in week 6 (P < 0.009), week 8 (P < 0.03) and week 10 (P < 0.04). No significant side effects occurred. At this dose amitriptyline was more effective than desmopressin and the combination of desmopressin and amitriptyline did not confer any additional benefit.

Impairments of the response preparation process in the elderly

In 20 young adults (23.1 +/- 1.64 yrs) and 20 old adults (68.5 +/- 5.53 yrs), H-reflexes were evoked simultaneously in the right soleus muscle that was preparing to respond to a reaction time stimulus and in the left soleus muscle that was uninvolved in the impending reaction time response. In the one-second period preceding the presentation of the response stimulus, the right H-reflex was inhibited as compared to the left H-reflex in the young adults; whereas, in the old adults, the response preparation profiles for the left and right H-reflexes were similar. Following the presentation of the response stimulus, H-reflex facilitation in the young adults reflected a non-specific tuning response and a specific, movement-related response. The nonspecific H-reflex enhancement was not observed in our older adults. These results indicate that the generalized tuning sequence necessary for movement planning is impaired in the elderly.