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Biomedical subjects

P Martin

Publications and source records attributed to P Martin.

At least 325 records · Page 18Linked to original sources
PubMed1998

Correlating structure and stability of DNA duplexes with incorporated 2'-O-modified RNA analogues.

Chemically modified nucleic acids are currently being evaluated as potential antisense compounds for therapeutic applications. 2'-O-Ethylene glycol substituted oligoribonucleotides are second-generation antisense inhibitors of gene expression with promising features for in vivo use. Relative to DNA, they display improved RNA affinity and higher nuclease resistance. Moreover, chimeric oligonucleotides with 2'-O-methoxyethyl ribonucleoside wings and a central DNA phosphorothioate window have been shown to effectively reduce the growth of tumors in animal models at low doses. Using X-ray crystallography, we have determined the structures of three A-form DNA duplexes containing the following 2'-O-modified ribothymidine building blocks: 2'-O-methoxyethyl ribo-T, 2'-O-methyl[tri(oxyethyl)] ribo-T, and 2'-O-ethoxymethylene ribo-T. In contrast to 2'-O-ethylene glycol substituents, the presence of a 2'-O-ethoxymethylene group leads to slightly reduced RNA affinity of the corresponding oligonucleotides. The three structures allow a qualitative rationalization of the differing stabilities of duplexes between oligonucleotides comprising these types of 2'-O-modified ribonucleotides and complementary RNAs. The stabilizing 2'-O-ethylene glycol substituents are conformationally preorganized for the duplex state. Thus, the presence of one or several ethylene glycol moieties may reduce the conformational space of the substituents in an oligonucleotide single strand. In addition, most of these preferred conformations appear to be compatible with the minor groove topology in an A-type duplex. Factors that contribute to the conformational rigidity of the 2'-O-substituents are anomeric and gauche effects, electrostatic interactions between backbone and substituent, and bound water molecules.

Base Composition↗
PubMed1998

Liver transplantation for decompensated cirrhosis after jejunoileal bypass: a strategy for management.

BACKGROUND: Although jejunoileal bypass results in end-stage liver disease in up to 100% of patients, little is known about outcome after liver transplantation. METHODS: The clinical courses of six patients who underwent liver transplantation at UCLA for decompensated cirrhosis owing to a jejunoileal bypass were reviewed. Liver function, allograft pathology, renal function, and nutritional status were assessed. RESULTS: Of the four patients with an intact jejunoileal bypass, two of the three who were biopsied had recurrent steatotic liver disease. The two patients whose jejunoileal bypass was reversed at the time of liver transplantation had lower alkaline phosphatase, lower creatinine, higher albumin, and higher cholesterol, and were more obese than their counterparts with intact bypasses. CONCLUSIONS: Patients undergoing liver transplantation for jejunoileal bypass-associated liver disease should, if possible, have their bypass reversed at the time of transplantation; otherwise, they must be followed closely and be biopsied routinely. Recurrent liver disease should prompt reversal of the jejunoileal bypass.

Adult↗
PubMed1998

Significance of early aminotransferase elevation after liver transplantation.

BACKGROUND: We retrospectively reviewed 213 consecutive patients who received their first liver allograft between January 1 and December 31, 1993, in order to study the impact of ischemia/preservation/reperfusion injury (IPRI) on patient and graft outcome. METHODS: The extent of IPRI was assessed by the peak value of aspartate aminotransferase (ASTmax) observed within the first 72 hr after transplant. For the purpose of univariate analysis, categorical classification of recipients was done based upon ASTmax as follows: group 1, ASTmax<600 U/L (n=46); group 2, ASTmax=600-2000 U/L (n=97); group 3, ASTmax>2000-5000 U/L (n=50), and group 4, ASTmax>5000 U/L (n=17). For multivariate analysis, stepwise Cox regression was performed with age, ASTmax, and United Network for Organ Sharing (UNOS) status as covariates. RESULTS: Groups were comparable with respect to age, UNOS status at the time of transplantation, and diagnostic case mix. Median follow-up was 644 days. The overall incidence of primary graft nonfunction (PNF) was 7.6%. PNF incidence was significantly correlated with the severity of IPRI (0%, 4%, 10%, and 41% for groups 1 to 4, respectively, P < 0.0001), but this impact was confined to the respective rates of retransplantation as early patient survival was unaffected. The 1-year survival of patients whose initial grafts manifested extreme IPRI (group 4) was significantly inferior to recipients in the three other groups (77%, 71%, 73%, and 52% for groups 1 to 4, respectively, P=0.03). This increased mortality was confined to patients who never achieved discharge from their initial hospitalization, with no significant differences between groups being detected in the survival of those patients who were discharged (84%, 80%, 85%, and 81% for groups 1 to 4, respectively, P=NS). Although overall 1-year graft survival was strongly correlated with the extent of IPRI (77%, 67%, 62%, and 41% for groups 1 to 4, respectively, P=0.001), this correlation was abolished when survival of grafts not lost to PNF was examined at 1 and 2 years. Stepwise Cox regression analysis confirmed the independent association between ASTmax and patient and graft survival. The long-term quality of allograft function as well as the incidence of chronic rejection and biliary complications were unrelated to the extent of IPRI. CONCLUSIONS: We conclude that: (1) patient survival is influenced by IPRI only when it is extreme (ASTmax>5000 U/L), provided parameters of graft function are used in conjunction with aminotransferase values to assess the need for prompt retransplantation; (2) short-term graft survival is proportional to the extent of IPRI, but grafts that are not lost to PNF have equivalent 1- and 2-year survival irrespective of the magnitude of IPRI; (3) 40% of grafts with extreme IPRI are lost to PNF, but the same proportion also provide long-term function; and (4) for surviving grafts, long-term biochemical function as well as the incidence of biliary complications and of chronic rejection are unrelated to the extent of IPRI.

Adult↗
PubMed1998

Sutureless cartilage graft laryngotracheal reconstruction using fibrin sealant.

OBJECTIVE: To determine whether fibrin sealant can replace suture as a means of holding a cartilage graft securely in the trachea. DESIGN: Randomized blinded control study comparing the use of fibrin sealant vs sutures in laryngotracheal reconstruction in ferrets. We compared results at 7 and 30 days. SUBJECTS: Forty ferrets randomized into 2 groups of 20: fibrin sealant and sutures. Within each group, half were studied at 7 days and the rest at 30 days. No ferrets were withdrawn from study because of adverse effects of the intervention. INTERVENTION: A carved costal cartilage graft was placed in the anterior cricoid split incision, and was secured with either fibrin sealant or sutures. All animals were extubated after recovery from anesthesia. Specimens were examined grossly and histologically. RESULTS: All animals survived until humanely killed. The pathologist, unaware of the groupings, measured lumen expansion in millimeters, cartilage graft migration, mucosal in-growth, degree of inflammation, graft integration, and graft viability. The fibrin sealant group had statistically significant (P<.05) better results in mucosal in-growth. In no categories was the suture group better than the fibrin sealant group. In comparing 7-day with 30-day results, the 30-day group had significantly better results in inflammation and graft viability. CONCLUSIONS: Fibrin sealant can be used in place of sutures with improvement in mucosal growth in costal cartilage laryngotracheal reconstruction in the experimental animal model. Use of fibrin sealant (instead of sutures) may result in less surgical trauma and edema, less surgical time, and faster recovery.

Animals↗
PubMed1998

Serologic responses by immunoblot following natural infection with rotavirus serotypes G1 and G4 in children.

Serologic responses to proteins of rotavirus serotypes G1, P1A[8]; G2, P1B[4]; G3, P1A[8]; and G4, P2A[6] were evaluated by immunoblotting paired sera from 17 children with primary rotavirus infection. Ten children were infected with G1, P1A[8]; five with G4, P1A[8]; and two with G4, P2A[6] viruses. Anti-VP6 and anti-VP2 were seen in most responses. Homotypic anti-VP7 developed following G1 and G4 infections in 8 (80%) and 6 (86%) cases, respectively. Homotypic anti-VP4 developed in 9 (60%) cases following P1A[8] infection and in 0 of 2 cases following P2A[6] infection. Heterotypic anti-VP7 appeared against G4 (20%) and G3 (20%) following the 10 G1 infections, and against G3 (86%) and G1 (57%) following the 7 G4 infections. Heterotypic anti-VP4 occurred in only 3 (18%) children. The data show the antigenic predominance of internal proteins VP6 and VP2. Homotypic antibodies developed against VP7 but not against VP4 in most cases, while heterotypic antibodies were infrequent.

Child, Preschool↗
PubMed1998

Liver transplantation for adult polycystic liver disease.

Polycystic liver disease, commonly associated with polycystic kidney disease, can result in massive hepatomegaly and debilitating symptoms. Surgical intervention for symptomatic polycystic liver disease has been associated with significant morbidity and inconsistent long-term palliation; it is more appropriate in patients with a single dominant cyst or cysts which is/are confined to one lobe. At our institution, nine patients have undergone orthotopic liver transplantation for symptomatic hepatic cysts with excellent long-term results and minimal morbidity and mortality. Surgical candidates were selected based on severe limitations in daily activities and on sequelae of hepatic cystic involvement. Other factors considered were the extent and pattern of hepatic cystic disease, the degree of hepatic and renal dysfunction, and prior surgical intervention. Three patients (33%) required combined liver and kidney transplantation because of renal cystic involvement with renal insufficiency. The one-year survival rate was 89% with excellent symptomatic relief and improved quality of life in all the surviving patients. One death occurred in a significantly malnourished 62-year-old female. Complications included one case each of hepatic artery thrombosis requiring retransplantation, biliary leak necessitating biliary reconstruction, and postoperative bleeding requiring re-exploration. The mean hospital stay was 23 days and the mean intraoperative blood transfusion requirement was 18 units. Our experience demonstrates that appropriately selected patients with extensive hepatic involvement with adult polycystic liver disease can have an excellent outcome with transplantation, with morbidity comparable with other surgical options.

Adult↗
PubMed1998

Prophylaxis against hepatitis B recurrence following liver transplantation using combination lamivudine and hepatitis B immune globulin.

Patients undergoing liver transplantation for hepatitis B-related liver disease are prone to recurrence. The mainstay of prophylaxis has been passive immunotherapy with hepatitis B immune globulin (HBIG). Antiviral therapy with lamivudine has proven effective in lowering hepatitis B virus (HBV) DNA and improving histology in patients with hepatitis B infection; its role in prophylaxis against hepatitis B recurrence following liver transplantation is under investigation. Viral breakthrough and resistance, however, are a significant problem with monotherapy with either HBIG or lamivudine. The efficacy of combination lamivudine/HBIG prophylaxis has not been reported. Fourteen patients underwent transplantation for decompensated liver disease owing to hepatitis B. Lamivudine (150 mg p.o./d) was begun before transplantation in 10 patients, including 4 who were HBV DNA-positive. In addition, 1 patient was HBV DNA-positive when transplanted. HBIG was given perioperatively and continued thereafter; treatment with lamivudine was maintained or initiated at the time of transplantation and continued indefinitely. The median follow-up was 387 days. Actuarial 1-year patient and graft survival was 93% (1 patient died of unrelated causes). At a median interval of 28 days following lamivudine treatment, all 5 HBV DNA-positive patients cleared HBV DNA from the serum; 1 went on to clear hepatitis B surface antigen (HBsAg), before transplantation, at day 148 of lamivudine treatment. By the highly sensitive polymerase chain reaction (PCR), at a median of 346 days (range, 130-525 days) following transplantation, all 13 surviving patients had no detectable serum HBV DNA. Lamivudine suppresses HBV replication in patients awaiting liver transplantation. At a median follow-up of 1.1 years, combination prophylaxis with lamivudine and HBIG prevented hepatitis B recurrence following liver transplantation.

Adult↗
PubMed1998

N-0923, a novel soluble dopamine D2 agonist in the treatment of parkinsonism.

N-0923, a novel aminotetralin dopamine D2 agonist, was shown to effectively reverse parkinsonian symptoms in nine dopa/agonist-responsive Parkinson's disease patients. The drug was given up to 4.5 hours by continuous intravenous (i.v.) infusion using an i.v. pump. The onset of anti-parkinsonian effect was seen within minutes of the initiation of the infusion and was absent within 90 minutes of cessation of the infusion. The short elimination half-life of N-0923 (90 min) would allow for the rapid initiation of drug effect when necessary and at the same time permit the effect to be terminated quickly if necessary. The drug would be useful in situations where oral medication is not feasible or is associated with erratic absorption. The patients tolerated the drug well. Dose escalation load was limited by nausea and vomiting. It should be noted that the doses were increased until these symptoms occurred, but therapeutic effects were noted well before the side effects occurred. Using a modified Columbia scale, maximum improvement consisted of a 27-95% drop in score. Maximum response was obtained at infusion rates varying from 2-16 microg/kg per hour and at blood levels of 0.11-1.49 microg/mL.

Aged↗
PubMed1998

Metabolism, excretion and pharmacokinetics of a single dose of [14C]-raltitrexed in cancer patients.

Raltitrexed (Tomudex) is a specific inhibitor of thymidylate synthase and has recently been licensed in Europe for use in the treatment of advanced colorectal carcinoma. This study evaluated the metabolism, excretion and pharmacokinetics after a single dose of 3.0 mg/m2 [14C]-raltitrexed in patients with advanced solid malignancies not amenable to curative therapy. From April 1994 to July 1995, nine patients (six men and three women) were recruited into the study. Pharmacokinetics analysis was performed during the first cycle of treatment in all patients and, in two patients, limited sampling was done prior to and during the second cycle of treatment. The mean observed peak plasma concentration (Cmax) was 700.6 ng/ml and the median time (tmax) to reach maximal raltitrexed concentrations was 15 min after the initiation of the infusion. After reaching Cmax the drug declined in a triexponential manner with a terminal half-life of 257 h. The AUC0-infinity as predicted by the pharmacokinetic model was 2341.7 ng h ml(-1). Clearance was 41.3 ml/min, of which renal clearance accounted for 50-60%. Urinary collection for the measurement of radiolabeled drug revealed that renal excretion extrapolated to infinity accounted for 40% of the total radioactive dose. Faecal excretion accounted for only 3% of the dose when samples were collected to day 5 in the first six patients. Collection was extended to 10 days in the last three patients and faecal elimination accounted for 14% in these patients. Raltitrexed measurements prior to subsequent doses suggest that there was no accumulation of the drug with repeated administration. Low levels of radioactivity measured in the red cell pellets on days 15, 22 and 29 are likely to represent drug retained by newly forming red cells at the time of dosing. Examination of the urine revealed that the drug was excreted unchanged. The toxicities seen were in line with those encountered in previous studies. Grade 3 and 4 thrombocytopenia occurred in three patients and grade 3 neutropenia occurred in two patients.

Adult↗
PubMed1998

Basque Country autochthonous population data on 7 short tandem repeat loci.

Blood samples from 202-208 unrelated Basque Country autochthonous individuals were amplified, typed and their allele frequencies were determined. Results demonstrate the assumption of independence within and between the loci analyzed. Therefore, a Basque population database can be used in identity testing to estimate the frequency of a multiple PCR-based locus DNA profile.

Blood Donors↗
PubMed1998

Rodent data and general hypothesis: antipsychotic action exerted through 5-Ht2A receptor antagonism is dependent on increased serotonergic tone.

The locomotor stimulation induced by the N-methyl-D-aspartate (NMDA) receptor antagonist MK-801 (dizocilpine) in mice was regarded as a model of at least some aspects of schizophrenia. The serotonin synthesis inhibitor dl-p-chlorophenylalanine (PCPA) was used to evaluate the involvement of endogenous serotonin in (a) the induction of MK-801-induced hyperlocomotion in NMRI mice, and (b) the inhibition of MK-801-induced hyperlocomotion by each of five monoaminergic antagonists (M100907, clozapine, olanzapine, raclopride, SCH23390). Further, brain monoaminergic biochemistry was characterised in rats and mice after various drug treatments. PCPA pretreatment did not significantly reduce MK-801-induced hyperlocomotion in any of the experiments performed; however in a meta-analysis of six experiments, the locomotion displayed by MK-801-treated animals was diminished 17% by PCPA pretreatment. The selective 5-HT2A receptor antagonist M100907 exerted a dose-dependent inhibition of MK-801-induced hyperlocomotion. This effect was abolished in mice pretreated with PCPA, but could be restored in a dose-dependent manner by restitution of endogenous 5-HT by means of 5-hydroxytryptophan (5-HTP). On the other hand, the inhibition of MK-801-induced hyperlocomotion exerted by the selective dopamine D-2 receptor antagonist raclopride or the dopamine D-1 receptor antagonist SCH23390 was unaffected by PCPA pretreatment. The antipsychotics clozapine and olanzapine displayed a split profile. Hence, the inhibitory effect on MK-801-induced hyperlocomotion exerted by low doses of these compounds was diminished after PCPA pretreatment, while inhibition exerted by higher doses was unaffected by PCPA. These results suggest that (1) MK-801-induced hyperlocomotion is accompanied by an activation of, but is not fully dependent upon, brain serotonergic systems. (2) In the hypoglutamatergic state induced by MK-801, endogenous serotonin exerts a stimulatory effect on locomotion through an action at 5-HT2A receptors, an effect that is almost completely counterbalanced by a concomitant inhibitory impact on locomotion, mediated through stimulation of serotonin receptors other than 5-HT2A receptors. M100907, by blocking 5-HT2A receptors, unveils the inhibitory effect exerted on locomotion by these other serotonin receptors. (3) Dopamine D-2 receptor antagonistic properties of antipsychotic compounds, when they come into play, override 5-HT2A receptor antagonism. Possible implications for the treatment of schizophrenia with 5-HT2A receptor antagonists are discussed. It is hypothesized that treatment response to such agents is dependent on increased serotonergic tone.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1998

Max Sandreczky: a pediatric surgeon in 19th-century Jerusalem.

Until the mid-19th century, there had not been a single resident physician in the Holy Land. However, by the first World War in 1914, 19 hospitals had been established in Jerusalem. The reasons for this unusual phenomenon were religious, political, and sectarian. This does not apply to The Marienstift Kinderhospital, which was unique in 19th century Jerusalem. The hospital was founded and operated by Dr Max Sandreczky, a German pediatric surgeon. The standards of medical and surgical practice in the hospital not only compared favorably with those in western Europe, but, in certain aspects, they were more advanced. The Marienstift Kinderhospital was an "implant" of a western institution in a society that was medieval in character. The response of this society was studied as well as the natural history of this unique institution and its medical director, the pediatric surgeon, Dr Max Sandreczky.

General Surgery↗
PubMed1998

Repair of exposed hydroxyapatite orbital implant by a tarsoconjunctival pedicle flap.

OBJECTIVE: This study aimed to determine a surgical method of management of exposed hydroxyapatite orbital implants. DESIGN: Noncomparative small case series. PARTICIPANTS: Four patients with exposures of hydroxyapatite orbital implants are described. INTERVENTION: A superiorly based tarsoconjunctival pedicle flap is fashioned from the upper eyelid; this flap is inverted and placed over the scleral-covered, exposed hydroxyapatite orbital implant. The flap is divided as a second-stage procedure 4 weeks later. MAIN OUTCOME MEASURE: Mucosal coverage of the previously exposed orbital implant was measured. RESULTS: Four cases are presented with excellent postoperative results at 3 to 18 months' follow-up. CONCLUSION: A suitably fashioned pedicle flap from the upper eyelid is an effective method of managing exposed hydroxyapatite orbital implants.

Adult↗