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Biomedical subjects

A C Allen

Publications and source records attributed to A C Allen.

At least 55 records · Page 3Linked to original sources
PubMed1994

Low antibody affinity restricted to the IgA isotype in IgA nephropathy.

Antibody affinity affects the handling and behaviour of immune complexes, and experimental studies have shown that animals which produce predominantly low-affinity antibody are prone to immune complex deposition resulting in glomerulonephritis. In order to investigate the potential role of antibody affinity in the pathogenesis of IgA nephropathy, affinity of both IgA and IgG antibody isotypes during secondary response to systemic immunization with tetanus toxoid was studied in 20 patients with IgA nephropathy. Patients with IgA nephropathy produced IgA antibodies of significantly lower affinity than controls (P < 0.001), whereas IgG antibody affinities were similar. Contrasting with controls, patients' IgA antibody affinity was inversely related to antibody concentration, with higher responders producing large amounts of low-affinity antibody. IgG antibody affinity increased with time, and maturation of IgG antibody affinity was similar in both controls and patients. IgA affinity in controls decreased with time, and this lack of IgA affinity maturation may explain the relative unimportance of IgA in normal systemic immunity. This temporal decrease in IgA affinity was not observed in patients with IgA nephropathy. The production of low-affinity IgA in IgA nephropathy may provide an explanation for the predominant deposition of IgA in this disease.

Adolescent↗
PubMed1993

Systemic and mucosal IgA responses to systemic antigen challenge in IgA nephropathy.

IgA nephropathy (IgAN) is characterized by the deposition of glomerular IgA. The source of the deposited IgA is not known, but both the mucosal and systemic IgA systems have been implicated. In order to investigate mucosal and systemic antibody production to systemic antigen challenge in IgAN, 20 patients and 20 controls where immunized with tetanus toxoid (TT). While patients with IgAN responded with a similar serum IgG, IgA, IgA1, and IgA2 antibody response to controls, they did, however, produce more IgA1 antibodies relative to IgA2 (P < 0.05). No salivary IgA antibody response was observed to systemic immunization in controls; however, there was a significant IgA response to TT in the saliva of patients with IgAN. IgA antibodies were produced in vitro by Epstein Barr virus (EBV)-transformed peripheral blood lymphocytes (PBLs) obtained from control blood only when taken shortly (1 or 2 weeks) after immunization. Patients with IgAN produced significantly more IgA anti-TT positive cultures than controls and for a longer period (P < 0.01) after immunization. In contrast, IgG anti-TT was produced in EBV-transformed cultures at all time points, but with no difference between IgAN and controls in the proportion of IgG producing cultures. These results demonstrate increased IgA antibody production in both the systemic and mucosal IgA systems following systemic immunization in IgAN and suggest an abnormal overlap between the two systems in IgAN.

Adolescent↗
PubMed1993

PCP: a review of synthetic methods for forensic clandestine investigation.

A review of the synthetic routes to phencyclidine (PCP, 1-(1-phenylcyclohexyl)piperidine) available in the open literature is presented. The emphasis herein is directed toward the forensic investigation of clandestine PCP laboratories. Six published synthetic routes to PCP/analogs are discussed. Each method is rated for overall yield, degree of difficulty and potential hazard, in order to assist the forensic chemist in evaluation of a particular clandestine operation. One clandestine recipe is illustrated and discussed.

Forensic Medicine↗
PubMed1993

Massive pericardial effusion as a cause for sudden deterioration of a very low birthweight infant.

We describe the successful resuscitation of a very low birthweight infant after sudden deterioration caused by a massive pericardial effusion. The neonatal course of this 740 gm, 26-week gestational age infant had been complicated by moderate respiratory distress syndrome, apnea, and bronchopulmonary dysplasia. A Silastic catheter was placed percutaneously in the right axillary vein on day 6 of life and documented to be in the superior vena cava prior to continuous parenteral nutrition. On day 38, her cardiorespiratory status abruptly deteriorated, blood return could not be obtained from the central line, and it was removed. Chest radiograph and subsequent echocardiogram confirmed a massive pericardial effusion. Under echocardiographic guidance, an emergency percutaneous pericardiocentesis allowed aspiration of 23 ml of straw-colored fluid. Her vital signs immediately returned to normal and reaccumulation of the effusion did not occur. Despite the high mortality of premature infants from pericardial effusion as a complication of central venous catheterization, early diagnosis and prompt therapy can assure a good outcome. As a cause of sudden deterioration of very low birthweight infants, tamponade must not be forgotten, since it is now a rapidly treatable complication of central venous cannulation.

Cardiac Tamponade↗
PubMed1993

Elevation of IgA in IgA nephropathy is localized in the serum and not saliva and is restricted to the IgA1 subclass.

Glomerular deposits in IgA nephropathy (IgAN) are predominantly IgA1 but their origin is not known. Previous studies have analysed serum or saliva IgA, but not in the same patients. To investigate whether IgA and IgA subclass anomalies occur in IgAN at both mucosal and systemic sites, blood and saliva from 20 patients and 20 age- and sex-matched controls were studied. Patients with IgAN had significantly increased serum IgA (P < 0.002), and this elevation was restricted to the IgA1 subclass. Serum IgA1 was also increased significantly (P < 0.001) but IgA2 was not. By contrast salivary IgA, IgA1, and IgA2 did not differ significantly from the controls. These results demonstrate that the elevated serum IgA is predominantly IgA1 and is likely to be of systemic origin. Further studies should consider the bone marrow as a potential source of the elevated IgA1.

Adolescent↗
PubMed1993

Deficiency of IgG subclass antibody response to tetanus toxoid associated with high serum IgA levels in IgA nephropathy.

In order to investigate IgG subclass response in IgA nephropathy (IgAN), 20 patients and 20 age and sex matched controls were systemically immunized with tetanus toxoid (TT). Nineteen/20 controls and 19/20 IgAN made a serum IgG anti-TT response of similar magnitude. However, significantly more patients with IgAN had undetectable amounts of at least one IgG subclass antibody to this antigen than controls (7/19 IgAN, 1/19 controls, p < 0.05). All individuals with an IgG subclass anti-TT deficiency lacked IgG1 and/or IgG4. Two patients made no IgG3 anti-TT (as well as no IgG1 and IgG4 anti-TT) but all individuals who responded to TT made IgG2 anti-TT. Total IgG subclass levels in IgAN did not differ from controls and no patient with IgAN had a total IgG subclass deficiency. Total serum IgA was significantly raised in IgAN (p < 0.002) and 6/7 IgAN with an IgG anti-TT subclass deficiency had a serum IgA level of over 3.2 milligrams compared to only 2/12 IgAN with no IgG subclass anti-TT deficiency (p < 0.01). The association of high serum IgA levels with IgG subclass deficiency to TT may be due to an abnormality in switching from IgG to IgA production in IgAN, or a manifestation of a defect of immunoregulation analogous to that proposed in IgA deficiency.

Adult↗
PubMed1993

Measurement of heroin and its metabolites by isotope-dilution electron-impact mass spectrometry.

A solid-phase extraction procedure was developed for the isolation of heroin, 6-acetylmorphine, and morphine from blood, plasma, saliva, and urine with subsequent assay by gas chromatography/mass spectrometry. Aprotic solvents, mild elution conditions, and an enzyme inhibitor were used to ensure maximum analyte stability. Samples were extracted and the extract was divided into two equal portions. One portion was assayed directly for heroin; detector response was linear over a concentration range of 1.0 to 250 micrograms/L. The second part of the extract was reacted with N-methyl-bis-trifluoroacetamide and assayed for the trifluoroacetyl derivatives of 6-acetylmorphine and morphine; detector response was linear over a concentration range of 1.0 to 500 micrograms/L. The limit of sensitivity was 1.0 microgram/L for each analyte. Hydrolysis of heroin to 6-acetylmorphine during extraction and analysis was < 5%. The method can be used to corroborate heroin use and to study the pharmacological effects of heroin and its metabolites.

Body Fluids↗
PubMed1992

Increased and prolonged production of specific polymeric IgA after systemic immunization with tetanus toxoid in IgA nephropathy.

IgA nephropathy (IgAN) is a chronic form of glomerulonephritis which is characterized by the deposition in the glomerular mesangium of polymeric IgA (pIgA), the source of which is unknown. In order to investigate the production of pIgA in IgAN, patients were immunized systemically with tetanus toxoid (TT). Two weeks after immunization patients and controls responded to TT with an IgA response of similar magnitude. HPLC separation of sera showed that patients with IgAN produce significantly more pIgA anti-TT than controls (7.7 versus 2.88 arbitrary units; P less than 0.04). At this time, 33% of serum IgA anti-TT produced by patients with IgAN was polymeric, compared with 21% produced by controls (P less than 0.02). Monomeric IgA (mIgA) anti-TT levels were similar in both groups. Four weeks after immunization the proportion of pIgA anti-TT in controls and patients was significantly reduced from the 2 week level (from 21% to 0%, P less than 0.02 for controls; and from 33% to 8%, P less than 0.001, for patients). Only four out of 12 controls had any detectable pIgA anti-TT at this time compared with nine out of 10 patients with IgAN (P less than 0.05), and IgAN patients produced proportionally more pIgA anti-TT than did controls (median 8%, interquartile ranges (IQR) 4-10% versus 0% IQR 0-3%; P less than 0.01). HPLC analysis under acid conditions did not alter the pattern of pIgA and mIgA anti-TT, suggesting that the high molecular weight IgA fraction was not due to complexes. These data indicate that circulating pIgA results (at least in part) from a systemic response to antigen, which may be exaggerated in IgAN.

Adolescent↗
PubMed1992

Bradykinin stimulates arachidonic acid release through the sequential actions of an sn-1 diacylglycerol lipase and a monoacylglycerol lipase.

In cultured dorsal root ganglion (DRG) neurons prelabeled with [3H]arachidonic acid [( 3H]AA), bradykinin (BK) stimulation resulted in increased levels of radioactive diacylglycerol, monoacylglycerol, and free AA. The transient increases in content of radioactive diacylglycerol and monoacylglycerol preceded the increase in level of free AA, suggesting the contribution of a diacylglycerol lipase pathway to AA release. An analysis of the molecular species of diacylglycerols in unstimulated cultures revealed the presence of two primary [3H]AA-containing species, 1-palmitoyl-2-arachidonoyl and 1-stearoyl-2-arachidonoyl diacylglycerol. BK stimulation resulted in a preferential increase in content of 1-stearoyl-2-arachidonoyl diacylglycerol. When DRG cultures were labeled with [3H]stearic acid, treatment with BK increased the amount of label in diacylglycerol and free stearic acid, but not in monoacylglycerol. This result suggested that AA release occurred through the successive actions of an sn-1 diacylglycerol lipase and monoacylglycerol lipase. Other data supporting a diacylglycerol lipase pathway was the significant inhibition of [3H]AA release and consequent accumulation of diacylglycerol by RG 80267, which preferentially inhibits diacylglycerol lipase. Analysis of the molecular species profiles of individual phospholipids in DRG neurons indicated that phosphoinositide hydrolysis may account for a significant portion of the rapid increase in content of 1-stearoyl-2-arachidonoyl diacylglycerol. We were unable to obtain evidence that the phospholipase A2 pathway makes a significant contribution to BK-stimulated AA release in DRG cultures. Under our assay conditions there were no BK-stimulated increases in levels of radioactive lysophosphatidylinositol, lysophosphatidylcholine, or lysophosphatidylethanolamine in cultures prelabeled with [3H]inositol, [3H]choline, or [3H]-ethanolamine, respectively.

Animals↗
PubMed1992

Simultaneous in situ hybridisation of native mRNA and immunoglobulin detection by conventional immunofluorescence in paraffin wax embedded sections.

AIMS: The development of a technique for simultaneous in situ hybridisation for native mRNA and conventional immunofluorescence for cytoplasmic antigens in routine pathology specimens. METHODS: Cocktails of synthetic deoxyoligonucleotides coding for immunoglobulin J chain and kappa light chain were 3' end labelled enzymatically with digoxigenin using terminal deoxynucleotidyl transferase. Native mRNA sequences were "unmasked" using proteolytic digestion with proteinase K and hybrid detection was achieved with an alkaline phosphatase labelled anti-digoxigenin antibody. Alkaline phosphatase was visualised with Fast red/naphthol AS-MX phosphate. Fluorescein isothiocyanate (FITC) conjugated anti-isotype antibodies were used simultaneously at the detection stage to identify the isotype production by individual plasma cells in endoscopic duodenal biopsy specimens. RESULTS: The IgA plasma cells of the lamina propria were identified by immunofluorescence and hybrids were detected in the anticipated plasma cell population by Fast red visualisation. The reaction product was visible in bright field or ultraviolet illumination which allowed FITC and Fast red labels to be visualised together under ultraviolet light at 490 nm. Dual labelled cells were clearly visible. Morphology was well preserved throughout. CONCLUSIONS: This technique permits the demonstration of specific mRNA species in cells expressing immunoglobulin. It combines all the advantages of non-radioactive synthetic oligonucleotide probes and conventional immunofluorescence techniques in routine formol-saline fixed and paraffin wax embedded sections with good retention of morphology.

Antigens↗
PubMed1991

Twin delivery: influence of the presentation and method of delivery on the second twin.

To ascertain the perinatal mortality and morbidity in the second twin as related to its presentation and method of delivery, we reviewed the data on 578 sets of twins delivered from 1980 to 1987 and included 397 sets in whom both twins were greater than or equal to 1000 gm, without lethal anomalies, and in whom the first twin presented as a vertex. The perinatal outcome comparing twin A (all vertex) with twin B (vertex or nonvertex) with cesarean section or vaginal delivery was analyzed. No statistically significant difference in perinatal mortality or morbidity was found in comparing the nonvertex second twin delivered vaginally or by cesarean section. The one perinatal death and significant perinatal morbidity occurred in infants weighing less than 1500 gm or at less than 32 weeks' gestational age. It is concluded that vaginal delivery, irrespective of the position of the second twin, is valid in selected cases as long as fetal weight is greater than 1500 gm and the gestational age is greater than or equal to 32 weeks.

Birth Order↗
PubMed1991

Inhibition by bradykinin of voltage-activated barium current in a rat dorsal root ganglion cell line: role of protein kinase C.

The whole-cell patch-clamp technique was used to record Ba2+ currents through voltage-activated calcium channels in the clonal dorsal root ganglion cell line F11-B9. The pain-producing peptide bradykinin (BK; 100 nM) reduced the sustained Ba2+ current in F11-B9 cells by 30%. In cultures prelabeled with 3H-arachidonic acid and tested under ionic conditions similar to those used for recording Ba2+ currents, BK also induced a concentration-dependent, transient, 2.7-fold accumulation of 3H-diacylglycerol. Both the elevation of 3H-diacylglycerol and the inhibition of Ba2+ current began within 5 sec following BK exposure, and the effective concentration range of BK was similar for the 2 responses. In whole-cell recordings, extracellularly applied 1-oleoyl-2-acetylglycerol (OAG; 0.5-5 microM) mimicked the degree of block and occluded the block of sustained current by BK. Another protein kinase C (PKC) activator, 1,2-dioctanoylglycerol (diC8), blocked 70-100% of sustained current when applied intracellularly or extracellularly at 5 microM, whereas extracellular application of ethylene glycol dioctanoate (5 microM), an analog reported not to stimulate PKC, inhibited only 14% of sustained current. The pseudosubstrate peptide PKC19-36 (2 microM in pipette) and the lipid staurosporine (100 nM in pipette), both inhibitors of PKC, reduced the effects of maximal concentrations of OAG or BK by 55-60%. Dynorphin A applied intracellularly (2 microM) as a control for nonspecific effects of PKC19-36 did not inhibit the block of sustained current by BK. These data are consistent with the hypothesis that BK inhibits whole-cell sustained Ba2+ current in F11-B9 cells via a mechanism that involves activation of PKC.

Alkaloids↗
PubMed1989

Diacylglycerol modulates action potential frequency in GH3 pituitary cells: correlative biochemical and electrophysiological studies.

We have investigated the involvement of enhanced phosphoinositide metabolism in mediating TRH-induced alteration of electrophysiological events related to prolactin secretion by GH3 cells (a line of pituitary origin). Patch-clamp recording (in the current clamp, whole-cell configuration) showed that a few seconds after TRH application there was a brief period (about 30 s) of membrane hyperpolarization followed by several minutes of increased calcium-dependent action potential frequency. In parallel experiments cells were labeled for 24 h with either [3H]myo-inositol or [3H]arachidonate. Application of TRH resulted in rapid increases in levels of inositol phosphates and diacylglycerol. The time course of elevation of inositol 1,4,5-triphosphate (maximal by 5 s) is compatible with an initial burst of intracellular calcium mobilization associated with a transient phase of TRH-induced prolactin release. Application of TRH was also followed by a rapid but more sustained (several minutes) period of elevated diglyceride accumulation; a time course corresponding to a prolonged period of prolactin release which is dependent on the influx of external calcium. A causal relationship between diglyceride release and increased action potential frequency was demonstrated since local application (via a U-tube apparatus) of either 2 microM phorbol ester (phorbol 12,13-dibutyrate or phorbol 12-myristate 13-acetate) or 60 microM 1-oleoyl-2-acetyl-glycerol to patch-clamped cells could mimic this aspect of the TRH effect. In contrast, the inactive phorbol ester, 4 alpha-phorbol, was unable to elicit this response.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Drug errors and incidents in a neonatal intensive care unit. A quality assurance activity.

We prospectively examined the causes of medication errors and incidents in a level 3 neonatal intensive care unit for a 2-year period. There were 313 incidents in 23,307 patient days (13.4 incidents per 1000 patient days). The relative risk of incidents was greater in more intensive levels of care. The two most common causes of incidents were neglecting to give a medication on schedule (n = 52) and nonregulation of an intravenous infusion (n = 32). Twenty percent of orders made by physicians that were in error resulted in serious incidents compared with only 6% of all other causes.

Drug Administration Schedule↗
PubMed1989

Effect of high-dose vitamin D supplementation on radiographically detectable bone disease of very low birth weight infants.

To test the hypothesis that high-dose vitamin D2 supplementation would result in a lower incidence of radiographically detectable bone disease, we randomly assigned 40 very low birth weight infants to a control group who received vitamin D2 in a dosage of 400 IU/day and 41 to an experimental group who received a dosage of 2000 IU/day. After 6 weeks, radiographs from all infants were scored blindly for degree of radiographic bone disease, and serum osteocalcin and 25-hydroxyvitamin D levels were measured. Mean vitamin D intake was 360 +/- 141 (SD) IU/day in the control group and 2170 +/- 144 (SD) IU/day in the experimental group. Median 6-week serum 25-hydroxyvitamin D levels were 24 ng/ml (range 3 to 60 ng/ml) in the control group and 68 ng/ml (range 9 to 150 ng/ml) in the experimental group (p less than 0.001). Overall, 20% of the infants had evidence of moderate radiographic bone disease and only 2% were severely affected. The radiographic bone score (median = 2.5) and serum osteocalcin concentration (mean = 21.7 +/- 8.7 ng/ml) in the control subjects did not differ significantly from those in the experimental group (median bone score = 2.0; mean osteocalcin level = 24.1 +/- 7.9 ng/ml). Although there may be a subset of very low birth weight infants who would benefit from high doses of vitamin D, we conclude that no generalized clinical improvement can be attributed to this regimen alone.

Bone Diseases↗
PubMed1989

Bradykinin stimulates phosphoinositide hydrolysis and mobilization of arachidonic acid in dorsal root ganglion neurons.

Cultures of fetal rat dorsal root ganglion neurons (7 days in culture) were prelabeled with myo-[3H]inositol or [3H]arachidonic acid for 24 h and stimulated with 10 microM bradykinin for time intervals of 5-300 s. The incubation was terminated by addition of 5% perchloric acid to extract inositol phosphates or organic solvent to extract lipids. Inositol phosphates were resolved by anion-exchange HPLC; lipids were resolved by TLC. Bradykinin stimulation resulted in a 10-fold increased accumulation of inositol 1,4,5-trisphosphate (IP3) and inositol bisphosphate (IP2) (fivefold) by 5 s. The increase in IP3 was transient (half maximal by 1 min), whereas stimulated IP2 levels were sustained for several minutes. Even longer term increases were observed in inositol monophosphate. Stimulation also resulted in a threefold increase in arachidonic acid which was preceded by transient increases in diacylglycerol (twofold) and arachidonoyl-monoacylglycerol (threefold). The temporal lag in the accumulation of arachidonic acid with respect to diglyceride and monoglyceride suggested the involvement of di- and monoglyceride lipases in arachidonic acid mobilization. A role for phospholipase A2 is also possible, because pretreatment of cultures with quinacrine partially blocked arachidonic acid release. Bradykinin-stimulated arachidonic acid release was decreased in the presence of calcium channel blockers nifedipine or verapamil (50 microM), or EDTA (2.5 mM). The role of calcium was verified further in that accumulation of phosphatidic acid, diacylglycerol, and arachidonic acid was maximally stimulated by treatment with the calcium ionophore A23187 (20 microM).

Animals↗
PubMed1988

Effect of timing of cerebral ultrasonography on the prediction of later neurodevelopmental outcome in high-risk preterm infants.

To determine the predictive value of cranial ultrasonographic examination in high-risk preterm infants at different postnatal ages, we scanned 110 infants less than or equal to 32 weeks gestational age at 1, 2, 3, and 6 weeks postnatal ages and at 40 weeks postconceptional age (PCA). Cranial abnormalities detected by ultrasonography at each postnatal age of examination were classified as minor (periventricular superolateral echogenicity with or without intraventricular hemorrhage, grades 1 to 3) or major (cystic periventricular leukomalacia with or without intraventricular hemorrhage, grade 4) and correlated with neurodevelopmental outcome determined by 1 year of age. Major abnormalities detected by ultrasonography were present in four infants at 1 week, four at 2 weeks, eight at 3 weeks, and 11 infants at 6 weeks and 40 weeks PCA, respectively. Nineteen infants (17%) had moderate to severe functional handicaps defined as cerebral palsy, cognitive or visual deficit, or deafness. The positive and negative predictive values of ultrasound examinations, with regard to later neurodevelopmental outcome, improved with increasing postnatal age at examination and was best at 40 weeks PCA. Negative results of ultrasound study at 40 weeks PCA most correctly predicted satisfactory outcome. Although only 58% of moderately to severely handicapped infants were correctly identified by ultrasound examination at 40 weeks PCA, all infants with major ultrasonographic abnormalities at 40 weeks PCA had moderate or severe handicap. Our data demonstrate that the timing of cerebral ultrasonography is important in the prediction of later neurodevelopmental outcome in high-risk preterm infants.

Age Factors↗