Biomedical subjects

J A Palmer

Publications and source records attributed to J A Palmer.

At least 19 recordsLinked to original sources

PubMed2004

Comparative analysis of genomic HSV vectors for gene delivery to motor neurons following peripheral inoculation in vivo.

The use of viral vectors for gene delivery to motor neurons in vivo has been hampered by the need to perform invasive surgery to inject directly the vector into the anterior horn of the spinal cord. Here, we have characterized the features of herpes simplex virus-1 (HSV)-derived vectors, in terms of gene mutations and promoter constructs, that are required to allow efficient transduction of motor neurons following a relatively noninvasive peripheral administration via sciatic nerve or footpad injection. Owing to the wide variety of animal models used to study neurodegenerative diseases of motor neurons, we analysed the effectiveness of these vectors in adult mice and adult and neonatal rats. We tested viruses with differing degrees of disablement based on the 1764 backbone (deleted for ICP34.5 and an insertional inactivation in VP16) rendered completely replication incompetent by the deletion of the essential immediate-early genes ICP27 and/or ICP4. In the adult mouse, prolonged gene expression in motor neurons was obtained after sciatic nerve inoculation with a vector defective in ICP4 and ICP27. In the adult rat, both the vector defective in ICP4 and the vector defective in ICP4 and ICP27 were capable of transducing motor neurons for extended periods of time during viral latency. This study demonstrates the feasibility of using HSV vectors for persistent transgene expression in motor neurons in a safe and nontoxic manner following peripheral administration. These vectors are potentially useful tools to investigate the functions of genes involved in motor neuronal survival and regeneration in models of motor neuron diseases in vivo.

Animals↗

PubMed2004

Short sirolimus half-life in pediatric renal transplant recipients on a calcineurin inhibitor-free protocol.

Immunosuppression with SRL may provide an opportunity to avoid long-term exposure to the nephrotoxicity of CNI. Thus, we have initiated an experimental protocol of IL-2r antibody induction, prednisone, MMF and SRL in pediatric renal transplant recipients (median age 15.5 yr, IQR 8.5, range 1.3-21.7). The recipients were treated with daclizumab every 2 wk for the first 2 months, prednisone on a tapering schedule, MMF at 1200 mg/m(2)/day and SRL given b.i.d. The SRL was dosed to achieve defined target whole blood 12-h trough levels. We performed 24 SRL PK profiles in 13 stable pediatric renal transplant recipients at 1 and 3 months post-transplant. Half-life (T(1/2)) and terminal T(1/2) were 9.7 (7.1-24.6) and 10.8 (4.4-95.2) hours (median, range) respectively at month 1, and were 9.6 (5-17.8) and 12.1 (4.7-71.0) hours respectively at month 3. SRL trough levels correlated with AUC (r(2) = 0.84, p < 0.001). There was no relationship between SRL and mycophenolic acid (MPA) AUC values (r(2) = 0.04). During the first 3 months post-transplant only one patient experienced severe neutropenia and another patient had subclinical (histologic) evidence of a mild acute rejection episode with no change in renal function. We conclude that the T(1/2) of SRL in pediatric renal transplant recipients not treated with CNI is much shorter than what has been reported for adults, due to rapid metabolism. We conclude that children require SRL dosing every 12 h, higher doses and frequent drug monitoring to achieve target SRL concentrations.

Adolescent↗

PubMed2001

Multiple immediate-early gene-deficient herpes simplex virus vectors allowing efficient gene delivery to neurons in culture and widespread gene delivery to the central nervous system in vivo.

Herpes simplex virus (HSV) has several potential advantages as a vector for delivering genes to the nervous system. The virus naturally infects and remains latent in neurons and has evolved the ability of highly efficient retrograde transport from the site of infection at the periphery to the site of latency in the spinal ganglia. HSV is a large virus, potentially allowing the insertion of multiple or very large transgenes. Furthermore, HSV does not integrate into the host chromosome, removing any potential for insertional activation or inactivation of cellular genes. However, the development of HSV vectors for the central nervous system that exploit these properties has been problematical. This has mainly been due to either vector toxicity or an inability to maintain transgene expression. Here we report the development of highly disabled versions of HSV-1 deleted for ICP27, ICP4, and ICP34.5/open reading frame P and with an inactivating mutation in VP16. These viruses express only minimal levels of any of the immediate-early genes in noncomplementing cells. Transgene expression is maintained for extended periods with promoter systems containing elements from the HSV latency-associated transcript promoter (J. A. Palmer et al., J. Virol. 74:5604-5618, 2000). Unlike less-disabled viruses, these vectors allow highly effective gene delivery both to neurons in culture and to the central nervous system in vivo. Gene delivery in vivo is further enhanced by the retrograde transport capabilities of HSV. Here the vector is efficiently transported from the site of inoculation to connected sites within the nervous system. This is demonstrated by gene delivery to both the striatum and substantia nigra following striatal inoculation; to the spinal cord, spinal ganglia, and brainstem following injection into the spinal cord; and to retinal ganglion neurons following injection into the superior colliculus and thalamus.

Animals↗

PubMed2000

Development and optimization of herpes simplex virus vectors for multiple long-term gene delivery to the peripheral nervous system.

Herpes simplex virus (HSV) has often been suggested as a suitable vector for gene delivery to the peripheral nervous system as it naturally infects sensory nerve terminals before retrograde transport to the cell body in the spinal ganglia where latency is established. HSV vectors might therefore be particularly appropriate for the study and treatment of chronic pain following vector administration by relatively noninvasive peripheral routes. However parameters allowing safe and efficient gene delivery to spinal ganglia following peripheral vector inoculation, or the long-term expression of delivered genes, have not been comprehensively studied. We have identified combinations of deletions from the HSV genome which allow highly efficient gene delivery to spinal dorsal root ganglia (DRGs) following either footpad or sciatic nerve injection. These vectors have ICP34.5 deleted and have inactivating mutations in vmw65. We also report that peripheral replication is probably necessary for the efficient establishment of latency in vivo, as fully replication-incompetent HSV vectors allow efficient gene expression in DRGs only after peripheral inoculation at a high virus dose. Very low transduction efficiencies are otherwise achieved. In parallel, promoters have been developed that allow the long-term expression of individual or pairs of genes in DRGs by using elements from the latently active region of the virus to confer a long-term activity onto a number of promoters which otherwise function only in the short term. This work further defines elements and mechanisms within the latently active region that are necessary for long-term gene expression and for the first time allows multiple inserted genes to be expressed from HSV vectors during latency.

Animals↗

PubMed1999

Disruption of the substance P receptor (neurokinin-1) gene does not prevent upregulation of preprotachykinin-A mRNA in the spinal cord of mice following peripheral inflammation.

The neuropeptide substance P is thought to play an important role in nociception, although the function of the peptide remains controversial. Following peripheral inflammation there is a pronounced upregulation of substance P expression both in sensory neurons and in postsynaptic neurons within the spinal cord. We have examined the levels of expression of mRNA encoding substance P and dynorphin following the development of inflammatory hyperalgesia in mice in which the substance P receptor gene, also known as the neurokinin-1 receptor gene, has been disrupted by homologous recombination. We show that inflammatory hyperalgesia following injection of complete Freund's adjuvant develops normally in animals that lack the neurokinin-1 receptor and that expression of mRNAs encoding substance P and the neuropeptide dynorphin are upregulated regardless of the genotype of the mouse. This suggests that substance P activity is not required for the development and maintenance of inflammatory hyperalgesia and that the upregulation of substance P expression is mediated by neurotransmitters other than substance P.

Animals↗

PubMed1998

Altered nociception, analgesia and aggression in mice lacking the receptor for substance P.

The peptide neurotransmitter substance P modulates sensitivity to pain by activating the neurokinin-1 (NK-1) receptor, which is expressed by discrete populations of neurons throughout the central nervous system. Substance P is synthesized by small-diameter sensory 'pain' fibres, and release of the peptide into the dorsal horn of the spinal cord following intense peripheral stimulation promotes central hyperexcitability and increased sensitivity to pain. However, despite the availability of specific NK-1 antagonists, the function of substance P in the perception of pain remains unclear. Here we investigate the effect of disrupting the gene encoding the NK-1 receptor in mice. We found that the mutant mice were healthy and fertile, but the characteristic amplification ('wind up') and intensity coding of nociceptive reflexes was absent. Although substance P did not mediate the signalling of acute pain or hyperalgesia, it was essential for the full development of stress-induced analgesia and for an aggressive response to territorial challenge, demonstrating that the peptide plays an unexpected role in the adaptive response to stress.

Aggression↗

PubMed1996

Dermatitis among automobile production machine operators exposed to metal-working fluids.

This cross-sectional study was designed to assess differences in prevalence of contact dermatitis between machine operators exposed to metal-working fluids (MWFs) and unexposed assemblers, and to assess potential risk factors for contact dermatitis among these machine operators. In their work, machine operators were exposed to either semisynthetic or soluble oil MWFs. We evaluated 158 machine operators and 51 assemblers from one large automobile transmission plant using questionnaires, dermatologist examination of the skin, and dermal dosimetry to measure wetness and metal exposures. We found that machine operators had more combined (definite plus possible) dermatitis (27.2% vs. 13.7%, chi(2) = 3.9, p = 0.05, 1 df) compared with assemblers. Among machine operators, risk factors significantly associated with (combined) dermatitis were subjective assessment of wetness of the work, exposure to semisynthetic as opposed to soluble oil MWF, current cigarette smoking, and increasing worker age. These risk factors suggested preventive and control measures including control of wet work, surveillance program including early self-report of dermatitis, consideration of replacement of semisynthetic with soluble oil MWFs, and strictly limiting smoking among machine operators exposed to MWFs.

Adult↗

PubMed1996

Immunohistochemical study of endometrial microvascular basement membrane components in women using Norplant.

The mechanisms responsible for progestogen-induced breakthrough bleeding remain unexplained. The aim of the present study was to examine the expression of three basement membrane components, collagen IV (CIV), laminin and heparan sulphate proteoglycan (HSPG), by immunohistochemistry in sections of endometrium from women receiving the subdermal levonorgestrel implant (Norplant) and normally cycling women. Control biopsies were obtained from 20 normal subjects from Melbourne, Australia, and pre- and post-Norplant-insertion biopsies were obtained from 11 women from Sydney, Australia, with between 3 and 6 months Norplant exposure. It was postulated that in Norplant users a decrease in the amount of basement membrane material present around endometrial vessels may be responsible for increased capillary fragility. The results, however, showed that for all three components, Norplant biopsies exhibited vascular basement membrane immunostaining at least as intense as that found in the mid-late secretory phase of the normal cycle. During the normal cycle, HSPG was only detected in approximately 40% of vessels with CIV and laminin immunoreactivity, and menstrual biopsies demonstrated reduced staining for all three components. Several biopsies exhibited a degree of regional variability in staining intensity, and Norplant biopsies exhibited areas of discrete, decidual-like stromal immunostaining for CIV and laminin. Although no differences were found in microvascular basement membranes in Norplant users that might explain capillary fragility, it is possible that other techniques could yield information on changes in the integrity of basement membrane components that might influence basement membrane strength.

Adolescent↗

PubMed1996

Effectiveness of subgingival scaling and root planing: single versus multiple episodes of instrumentation.

This study evaluates the effectiveness of subgingival scaling and root planing comparing the effect of a single instrumentation to the effect of three instrumentations. A total of 35 teeth in 15 patients were selected; 15 were scaled once (Group A), 15 were scaled three times (Group B), and 5 were used as controls (Group C), representing teeth that were not instrumented. The Group A and B teeth were chosen in the same patient based on random selection. All the teeth were scored by the calculus index of the periodontal disease index. Six surface locations were probed to determine probing depth. The level of the gingival margin was marked on the teeth to locate supra- and subgingival calculus after extraction. The Group A and B teeth received the initial episode of scaling and root planing for not more than 10 minutes, then only the Group B teeth received two additional instrumentations of not more than 5 minutes each. The additional instrumentations were performed 24 hours after the initial scaling. The scaled and control teeth were extracted immediately after the third instrumentation period. The teeth were washed with water and stained with methylene blue. They were viewed under a stereomicroscope which had a tenth grid on its eyepiece. Assessments were made involving the total counts and percents of the surfaces covered with calculus on the scaled and unscaled teeth. The results demonstrated no significant difference in the effectiveness of calculus removal between single and multiple episodes of scaling and root planing. Similar results were found for the total amount of calculus removed, the calculus removed from individual surfaces, and the calculus removed from various probing depth levels.

Adult↗

PubMed1995

Natural history and etiology of hyperuricemia following pediatric renal transplantation.

A retrospective review was conducted to determine the incidence, etiology, natural history and complications of hyperuricemia after pediatric renal transplantation. Of 81 active transplant recipients aged 10.1 +/- 4.8 (mean +/- SD) years being followed by St. Christopher's Hospital for Children, 57 (70%) were males and 59 (73%) Caucasian. Their immunosuppression consisted of azathioprine, cyclosporine A and prednisone. Mean serum uric acid concentrations peaked at 6 months post transplantation (6.2 +/- 2.6 mg/dl), when 39% of the patients had hyperuricemia and 60% were receiving diuretics, and decreased thereafter. At 30 months, 23% of the patients had hyperuricemia and 17% required diuretics. When we compared 42 normouricemic (group A) with 24 hyperuricemic (group B) patients at 18 months post transplantation, we found that patients in group B were older (11.6 +/- 4.2 vs. 8.6 +/- 5.2 years, P = 0.01), had worse renal function (77 +/- 25 vs. 96 +/- 36 ml/min per 1.73 m2, P = 0.03) and required diuretics more frequently (63% vs. 21%, P = 0.001), but had identical blood levels of cyclosporine A (82 +/- 28 vs. 84 +/- 35 ng/ml, P = 0.78). A family history of gout did not affect the prevalence of hyperuricemia after transplantation. Asymptomatic hyperuricemia is common following pediatric renal transplantation and is more likely attributable to reduced renal function and diuretic therapy than to the known hyperuricemic effect of cyclosporine A. Of these variables, only diuretic therapy is readily controllable and should be closely regulated following pediatric renal transplantation.

Aging↗

PubMed1995

Effects of type of exercise on depression in recovering substance abusers.

This experiment investigated the effects of three types of structured exercise (aerobics, bodybuilding, and circuit training) on depressive symptoms of 45 clients undergoing a 4-wk., inpatient rehabilitation program for substance abuse. Pre- and posttest measures included the Center of Epidemiological Studies--Depression, resting pulse rate, blood pressure, maximum strength on incline bench press, and estimates of aerobic fitness and body fat. The bodybuilding program produced a significant decrease in depressive symptoms. Physiological and psychological explanations are discussed.

Adolescent↗

PubMed1995

Childhood abuse as a factor in attrition from drug rehabilitation.

The following factors were examined as possible influences of clients' attrition from inpatient and outpatient drug-rehabilitation programs: depression (Center of Epidemiological Studies-Depression test), attributional style (Attributional Style Questionnaire), primary drug of choice, family incidence of substance abuse, and history of childhood physical abuse. A step-wise regression analysis indicated that a history of childhood abuse was a statistically reliable predictor of program noncompletion for 92 substance abusers who entered a drug-rehabilitation program.

Adult↗

PubMed1994

Growth after conversion to alternate-day corticosteroids in children with renal transplants: a single-center study.

During the 1980s all children with growth potential and stable/adequate renal function at 6-9 months after kidney transplantation underwent conversion to alternate-day corticosteroids in an attempt to maximize growth. Conversion was attempted in 79 of 160 children who received allografts during this decade and was considered successful if they remained on alternate-day prednisone for more than 1 year, with a calculated creatinine clearance of at least 75% of the pre-conversion baseline value. Conversion succeeded in 55 children but failed in 24. Growth was markedly improved among those successfully converted when compared with the failure group, as measured by standard deviation score for growth velocity based on chronological age (+0.94 +/- 1.58 vs. -0.86 +/- 1.53, P < 0.001) and bone age (+0.49 +/- 0.61 vs. -1.24 +/- 1.47, P < 0.001). The improved growth among the successfully converted patients is believed to have been related to the combined effects of lower corticosteroid dose (0.36 +/- 0.16 vs. 0.48 +/- 0.21 mg/kg per day, P < 0.02) and better renal function (calculated creatinine clearance 87 +/- 32 vs. 47 +/- 21 ml/min per 1.73 m2, P < 0.001) at 1 year post conversion. Two factors appeared to improve the likelihood of successful conversion: the use of cyclosporine and receiving a live-related rather than cadaver transplant. Cyclosporine was associated with improvement in the overall rate for successful conversion in all recipients, from 59% to 83% (P < 0.05). Recipients of allografts from live-related donors underwent successful conversion in 90% of cases compared with 58% receiving cadaver allografts (P < 0.05). (ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Peritoneal dialysis catheter infections in children after renal transplantation: choosing the time of removal.

As a foreign body, the peritoneal dialysis (PD) catheter represents a potential source of infection, particularly for immunosuppressed renal transplant patients. A retrospective study was therefore undertaken to compare the risks and benefits of our policy of removing PD catheters at 3 months following renal transplant, which was established to allow for early re-initiation of dialysis. Between 1984 and 1990, 43 renal transplants were performed in 35 children who had been receiving maintenance PD. During the 1st month post transplantation, the PD catheter was used in 25 patients (58%) because of acute rejection or primary allograft non-function. Thirty-one patients were eventually discharged with functioning allografts and a PD catheter in place. Of them, 43% developed a catheter-related infection within the next 2 months, a period during which PD was not performed. Potential contributing factors included a history of catheter-related infection prior to transplantation, use of high-dose methylprednisolone to treat acute rejection, and the type of maintenance immunosuppression prescribed; conversely, the use of prophylactic antibiotics appeared to decrease this risk. This study established the potential need for the catheter during the first few weeks, but because of the infection risk of 43% by 3 months post transplantation, our protocol was revised to include catheter removal at the time of hospital discharge. From 1990 until the end of 1992, an additional 19 PD recipients underwent transplantation. In this group, catheters were used during the 1st month in 6 children (32%). Fifteen patients were discharged with a functioning allograft and only 1 patient returned to PD at 12 months post transplant. It is concluded that PD catheters represent an additional source of infection following transplantation and should be removed at the time of hospital discharge, after which the likelihood of use is low.

Anti-Infective Agents↗

PubMed1993

Evaluation of OKT3 monoclonal antibody and anti-thymocyte globulin in the treatment of steroid-resistant acute allograft rejection in pediatric renal transplants.

We reviewed the effectiveness of Muromonab-CD3 (OKT3) and anti-thymocyte globulin (ATG) in the treatment of corticosteroid-resistant acute renal allograft rejection in 49 transplanted children. Reversal of rejection was successful in 22 of 23 patients (96%) treated with OKT3 and 21 of 26 (81%) treated with ATG (P = NS). Re-rejection episodes occurred within 1 month of cessation of therapy in 9 of 22 patients treated with OKT3 but only in 2 of 21 who received ATG (P < 0.05). In the patients with re-rejection, 7 of the 9 patients originally given OKT3 and 1 of the 2 who received ATG responded to a repeat course of high-dose corticosteroids; thus, at 1 month post treatment, the incidence of graft loss due to initial rejection or re-rejection was 13% for the OKT3 and 23% for the ATG group (P = NS). Graft survival was similar at 6 months: 82% for OKT3- and 73% for ATG-treated patients (P = NS); 100% patient survival was noted in both groups. Mean calculated creatinine clearance prior to, during, and at 1 and 6 months post rejection was similar in the OKT3- and ATG-treated groups. Neutropenia and thrombocytopenia occurred more frequently in the ATG group, but there was no significant difference in infectious complications. Two patients developed high (> or = 1:1,000) OKT3 antibody titers. In our experience, children with corticosteroid-resistant acute renal allograft rejection treated with OKT3 and ATG had similar allograft survival and level of renal function at 1 and 6 months, and number of infectious complications post therapy.

Acute Disease↗

PubMed1991

Cloning, sequence and transcriptional analysis of the structural gene for LPD-3, the third lipoamide dehydrogenase of Pseudomonas putida.

The third lipoamide dehydrogenase structural gene of Pseudomonas putida, lpd3, was isolated from a library of P. putida PpG2 DNA cloned in Escherichia coli TB1. The nucleotide sequence of lpd3 and its flanking regions indicate that lpd3 is not part of an operon, which is unique for a prokaryotic lipoamide dehydrogenase. An open reading frame was found 207 bases upstream from the start of transcription, but is encoded on the strand opposite lpd3. There is no evidence of an open reading frame immediately downstream from lpd3. The coding region of lpd3 consists of 1401 bp, providing for 466 amino acids plus a stop codon with a G/C content of 62.4%. The transcriptional start site was located 33-bp upstream from the start of translation. The third lipoamide dehydrogenase (LPD-3) shares amino acid identity with the other two lipoamide dehydrogenases of P. putida, 45% with that of the 2-oxoglutarate dehydrogenase and pyruvate multienzyme complexes, and 45.9% with the lipoamide dehydrogenase of the branched-chain oxoacid complex. LPD-3 is more closely related to eukaryotic lipoamide dehydrogenases since it has 53.6% amino acid sequence identity with pig and human lipoamide dehydrogenases and 51.1% identity with yeast lipoamide dehydrogenase. LPD-3 was not produced in wild-type P. putida PpG2 under a variety of growth conditions. However, LPD-3 was produced in P. putida PpG2 carrying pSP14, a pKT240-based clone with the entire lpd3 gene plus 104 bases of the leader. The only demonstrated role of LPD-3 in P. putida is as a substitute for lipoamide dehydrogenase of the 2-oxoglutarate dehydrogenase and pyruvate multienzyme complexes when the latter is inactive or missing.

Amino Acid Sequence↗

PubMed1991

Cloning and sequence analysis of the LPD-glc structural gene of Pseudomonas putida.

Pseudomonas putida is able to produce three lipoamide dehydrogenases: (i) LPD-glc, which is the E3 component of the pyruvate and 2-ketoglutarate dehydrogenase complexes and the L-factor for the glycine oxidation system; (ii) LPD-val, which is the specific E3 component of the branched-chain keto acid dehydrogenase complex and is induced by growth on leucine, isoleucine, or valine; and (iii) LPD-3, which was discovered in a lpdG mutant and whose role is unknown. Southern hybridization with an oligonucleotide probe encoding the highly conserved redox-active site produced three bands corresponding to the genes encoding these three lipoamide dehydrogenases. The complete structural gene for LPD-glc, lpdG, was isolated, and its nucleotide sequence was determined. The latter consists of 476 codons plus a stop codon, TAA. The structural gene for LPD-glc is preceded by a partial open reading frame with strong similarity to the E2 component of 2-ketoglutarate dehydrogenase of Escherichia coli. This suggests that lpdG is part of the 2-ketoglutarate dehydrogenase operon. LPD-glc was expressed in Pseudomonas putida JS348 from pHP4 which contains a partial open reading frame corresponding to the E2 component, 94 bases of noncoding DNA, and the structural gene for lpdG. This result indicates that lpdG can be expressed separately from the other genes of the operon.

Amino Acid Sequence↗

PubMed1991

Antimouse antibody response after OKT3 administration for steroid resistant rejection.

OKT3 has become one of the more effective antirejection therapies for patients receiving kidney transplants. However, its usefulness is diminished or blocked by the development of antimouse/anti-OKT3 antibodies. We evaluated 17 children receiving OKT3 for steroid-resistant acute rejection for the development and persistence of antibodies after therapy. OKT3 was successful in reversing acute rejection in 14 of 17 patients. Eight children developed antimouse antibodies, 7 at a low titer (1:100). The retesting of all children 6 months later showed no detectable antibodies. Children develop anti-OKT3 antibodies at a rate similar to adults and with time lose detectable levels which may have significance if a subsequent course of OKT3 is needed.

Animals↗