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Biomedical subjects

M J Snyder

Publications and source records attributed to M J Snyder.

At least 19 recordsLinked to original sources
PubMed1995

Expression of cytochrome P450 genes of the CYP4 family in midgut and fat body of the tobacco hornworm, Manduca sexta.

Two conserved regions in the alignment of cytochrome P450 family 4 (CYP4) proteins served as guide to the synthesis of degenerate oligonucleotide primers. The primers were used in PCR from a midgut cDNA library and RT-PCR from fat body mRNA, both from last instar larvae of the tobacco hornworm, Manduca sexta. The PCR products of 443-449 bp were cloned and sequenced. Nine P450 clones representing four new genes were obtained from the midgut. Fifteen P450 clones representing three new genes were obtained from the fat body. Two genes were expressed in both tissues. A number of putative allelic variants were also observed for three of the P450 genes. The resulting sequences of 130-132 amino acids were aligned to generate a parsimony analysis of CYP4 P450 proteins. Two new subfamilies of CYP4 were designated from M. sexta by these procedures, CYP4L and CYP4M. The sequence of a full-length cDNA clone for CYP4M2 (41.2% identity to CYP4C1) confirmed that the PCR products obtained by this method were P450s belonging to the CYP4 family. The developmental expression of the CYP4 genes appeared to be coordinately regulated in both fat body and midgut. In the fat body, CYP4 mRNA levels declined after the first day of the final larval instar, peaked during the wandering stage, and fell again until the prepupal molt. Midgut CYP4 mRNA levels were higher during the active feeding, midwandering, prepupal, and pupal stages. Addition of 2-tridecanone or 2-undecanone to the diet induced several P450s in the midgut and in the fat body. Phenobarbital induced CYP4M1 in the fat body and dietary clofibrate induced the mRNA levels of CYP4M1 and CYP4M3 in the midgut. The results indicate that at least four CYP4 genes are expressed in single tissues of a Lepidopteran insect. Several of these P450 may be involved in tissue responses to xenobiotics.

Adipose Tissue↗
PubMed1995

Glutathione S-transferases from larval Manduca sexta midgut: sequence of two cDNAs and enzyme induction.

Two glutathione S-transferase (GST) clones from a larval midgut cDNA library of the tobacco hornworm, Manduca sexta were sequenced. The nucleotide sequence of the first clone, M. sexta GST1, encoded a protein of 217 amino acids with a predicted molecular weight of 24,644 and isoelectric point of 4.8. The M. sexta GST1 was 45.9-48.6% identical to GSTs from Musca domestica and several Drosophila species. The M. sexta GST2 cDNA encoded a protein of 203 amino acids with a predicted molecular weight of 23,596 and isoelectric point of 5.5. The M. sexta GST2 shared 44.8-50.0% sequence identity to a second cluster of insect GSTs from M. domestica, D. melanogaster and Anopheles gambiae. GST1 and GST2 were only 24.1% identical in amino acid sequence. The divergence of these two classes of insect GSTs occurred before the radiation of Diptera and Lepidoptera. Northern analysis of the expression of these GSTs showed increased GST1 mRNA levels in midguts of larvae fed diets containing 2-undecanone, or phenobarbital. Midgut and fat body cytosolic GST activities were induced when larvae were fed diets containing 2-tridecanone, 2-undecanone, or phenobarbital. Partial purification of midgut GSTs by size-exclusion and glutathione affinity chromatography resulted in a series of isoelectric focusing bands, with the major one corresponding to the predicted isoelectric point of the M. sexta GST1. In summary, two midgut GSTs have been identified on the basis of cDNA sequence and one of these, GST1, was inducible by dietary chemicals.

Amino Acid Sequence↗
PubMed1994

Carmustine, Ara C, cyclophosphamide and etoposide with autologous bone marrow transplantation in relapsed or refractory lymphoma: a dose-finding study.

The purpose of this study was to define the dose-limiting non-hematologic toxicity of carmustine, Ara C, cyclophosphamide and etoposide (BACE). Between October 1986 and March 1990, 37 patients with relapsed or refractory lymphoma received escalating doses of combination chemotherapy followed by autologous bone marrow transplant (ABMT). Twenty patients with Hodgkin's disease (HD) and 17 patients with intermediate or high grade non-Hodgkin's lymphoma (NHL) initially received conventional-dose therapy with either a 7 week course of modified MACOP-B or a single dose of cyclophosphamide (CY) at 2 g/m2 depending on prior therapy and response. Regardless of response, patients then received escalating doses of BACE, toxicity permitting. Ten patients obtained complete responses (CR) and 12 patients were partial responders (PR), CR+PR (75%) with modified MACOP-B and 7 (64%) patients obtained PR with CY. The maximum-tolerated dose (MTD) for BACE was determined to be carmustine 700 mg/m2, Ara C 1500 mg/m2, CY 150 mg/kg and etoposide 1500 mg/m2. When Ara C was escalated from 1500 mg/m2 to 3000 mg/m2 holding the other drugs at the prior doses, the next two patients died secondary to diffuse alveolar damage. Overall and event-free survivals are identical with 14 of 37 patients (38%) alive with a median follow-up of 61 months (range 38-79 months). Ten patients were treated at the MTD, none of whom died a toxic death and 3 (30%) are alive with a median follow-up of 42 months (range 38-52 months). We defined the MTD and BACE showing pulmonary toxicity to be the dose-limiting non-hematologic toxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Marked increase in veno-occlusive disease of the liver associated with methotrexate use for graft-versus-host disease prophylaxis in patients receiving busulfan/cyclophosphamide.

The use of cyclosporine-A/methotrexate (CyA/MTX) for graft-versus-host disease (GVHD) prophylaxis is safe and effective for patients undergoing allogeneic bone marrow transplantation after preparation with cyclophosphamide and total body irradiation. We report 87 patients prepared for allogeneic transplant with busulfan 4 mg/kg/d orally for 4 days, followed by cyclophosphamide 60 mg/kg/d intravenously for 2 days (Bu4Cy2). A marked increase in hepatotoxicity was observed in 20 patients administered CyA/MTX, compared with 67 historical control patients who received CyA/methylprednisolone (CyA/MP) for GVHD prophylaxis with all other treatment and support variables remaining constant. The incidence of hyperbilirubinemia (bilirubin greater than or equal to 2 mg/dL) increased from 48% to 80% (P = .02), and the mean maximal bilirubin increased from 4.67 +/- 7.27 to 8.72 +/- 8.73 mg/dL (P = .04), when CyA/MTX was used in place of CyA/MP for GVHD prophylaxis. In addition, the incidence of veno-occlusive disease (VOD) increased from 18% to 70% (P = .0001), and death caused by VOD increased from 4.5% to 25% (P = .02). Survival was not significantly different for the two groups because of a higher non-VOD death rate in patients receiving CyA/MP for GVHD prophylaxis (P = .77). We suggest caution when using Bu4Cy2 in combination with CyA/MTX for GVHD prophylaxis.

Actuarial Analysis↗
PubMed1992

Role of the midgut gland in metabolism and excretion of ecdysteroids by lobsters, Homarus americanus.

The chromatographic profile of ecdysteroids (Ecds) from the midgut gland (MG) of juvenile female lobsters, Homarus americanus, was examined using high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA) over four stages of the molt cycle. Upon initial examination, highly polar Ecd conjugates appeared to be the principal metabolites found in all molt stages. HPLC fractions containing apolar Ecds initially exhibited low RIA activity. Upon hydrolysis with a Helix pomatia enzyme preparation and reanalysis, significant amounts of other Ecds were released. Amounts of apolar Ecd conjugates were estimated, at their highest levels, to be at least 50% of the total Ecds in MGs of molt stage D3 lobsters. Only the MG formed significant amounts of apolar Ecds upon in vitro culture with [3H]ecdysone ([3H]E). Epidermis and antennal gland significantly increased their rates of [3H]E metabolism in vitro between molt stages C4 and D1. This result further supports the idea that regulation of ecdysteroid metabolism, at least in selected tissues, may be important in the molt cycle regulation of hormone titers. Using gel filtration column chromatography and sucrose density gradient centrifugation analyses, evidence was found for association of apolar Ecds with a protein(s) from MG cytosol. The protein was estimated to have a molecular weight of 180,000-200,000 and specifically bound apolar Ecds.

Animals↗
PubMed1992

Pilot trial of prophylactic ursodiol to decrease the incidence of veno-occlusive disease of the liver in allogeneic bone marrow transplant patients.

Ursodiol is a hydrophilic, non-hepatotoxic bile salt indicated for the medical treatment of cholesterol gallstones. This pilot study explored the use of prophylactic ursodiol in an attempt to decrease the incidence and severity of veno-occlusive disease (VOD) of the liver following allogeneic bone marrow transplantation (BMT). Between February 1991 and January 1992, 22 consecutive patients undergoing BMT for hematologic malignancies received the BU(4)/CY(2) preparative regimen and CSA/MTX for GVHD prophylaxis. Ursodiol, 600-900 mg daily by mouth was begun at least 1 day prior to beginning the preparative regimen. Results for this pilot group were compared to a control group of 28 consecutive patients transplanted between June 1989 and January 1991 with the same regimen without ursodiol. There were no significant differences in disease or clinical status between the groups pretransplant. However, mean baseline AST levels were significantly higher in the ursodiol group, 28.0 U/l vs 18.1 U/l in the control group (p = 0.001). The median maximum bilirubin observed post-transplant was 2.35 mg/dl (range 0.9-45) in the ursodiol group, and 5.05 mg/dl (range 0.7-29.4) in controls. The incidence of VOD was 2/22 (9.1%) in the ursodiol group and 18/28 (64.3%) in controls (p = 0.0001). Death due to VOD occurred in 1/22 patients (4.5%) in the ursodiol group and in 6/28 (21.4%) controls (p = 0.12). Our data suggest that ursodiol may decrease the incidence of VOD in allogeneic BMT patients.

Adolescent↗
PubMed1991

Ecdysteroids in relation to the molt cycle of the American lobster, Homarus americanus. II. excretion of metabolites.

Ecdysteroid (Ecd) excretion patterns were followed during the molt cycle of adult male and female lobsters. Homarus americanus. Urine was the major route of Ecd elimination, amounting to greater than or equal to 96% of the excreted radioimmunoassay activity for all molt stages. The other identified route of Ecd elimination from the hemolymph was the feces, which accounted for the remaining 4% of the total Ecd excretion. High polarity metabolites (HP), including 20,26-dihydroxyecdysone (2026E) and 20-hydroxyecdysonoic acid (20EA), were the major types of Ecds found in the urine. Other urinary Ecd components included 20-hydroxyecdysone (20E), ecdysone (E), and ponasterone A (P). The major portion of urinary HP was composed of conjugates of 2026E, 20E, E, P, and other unidentified metabolites. The fecal Ecds were predominately HP and apolar metabolites. Apolar fecal Ecds were hydrolyzable to release 20EA, 2026E, 20E, E, P, and other metabolites. By means of intubation, [3H]E was placed directly into the cardiac stomach of lobsters. The gut pathway formed an apolar conjugate of [3H]E which was found exclusively in the feces. Lobsters are therefore capable of excreting ingested Ecds without absorption.

Animals↗
PubMed1991

Ecdysteroids in relation to the molt cycle of the American lobster, Homarus americanus. I. Hemolymph titers and metabolites.

Hemolymph ecdysteroid (Ecd) titers were measured using radioimmunoassay (RIA) during the molt cycle of the American lobster, Homarus americanus. Individual animals showed small, transitory rises of Ecds which increased in magnitude with the onset of premolt and culminated in a large premolt peak at morphological stages D2(2)-D3(1). Male lobsters had significant postmolt peaks and late premolt titers that remained high until ecdysis. In females, postmolt peaks were absent and late premolt titers reached basal levels before ecdysis. At least seven different Ecd metabolites were identified by high-performance liquid chromatography-RIA analyses. High polarity products (HP) were the most abundant metabolites in virtually every molt stage. Titers of HP were significantly higher in males during late postmolt-early intermolt and in late premolt. Levels of 20-hydroxyecdysone (20E) were equivalent in both sexes and correlated with the morphological changes associated with premolt. Evidence was also obtained for the presence of ecdysone, ponasterone A, and other as yet unidentified metabolites. The pattern of Ecd metabolites in the hemolymph supports other data indicative of 20E as the major molting hormone. Metabolism of 20E is primarily toward more polar compounds, including conjugates.

Animals↗
PubMed1988

An evaluation of optimal sampling strategy and adaptive study design.

We have evaluated the utility of optimal sampling strategy coupled with adaptive study design in the determination of individual patient and population pharmacokinetic parameter values. In 9 patients with cystic fibrosis receiving a short (1 minute) infusion of ceftazidime pharmacokinetic parameter values were determined with a nonlinear least-squares estimator analyzing a traditional, geometrically spaced set of 12 postinfusion serum samples drawn over 8 hours. These values were compared with values generated from four sample subsets of the 12 obtained at optimal times and analyzed by nonlinear least-squares estimator, as well as a maximum a posteriori probability Bayesian estimator with prior distributions placed on beta and clearance. The four sampling times were determined according to an adaptive design optimization technique that employs sequential updating of population prior distributions on parameter values. Compared with the 12-point determination, the four optimal points analyzed with the maximum a posteriori probability Bayesian estimator faithfully reproduced both microscopic and hybrid pharmacokinetic parameter values for individual patients and, consequently, also produced accurate measures of population central tendency and dispersion. This has important implications in being able to more efficiently derive target patient population pharmacokinetic information for new drugs. This should also allow generation of better concentration-effect relationships in populations of interest.

Adolescent↗
PubMed1983

Serodiagnosis of Rocky Mountain spotted fever: comparison of IgM and IgG enzyme-linked immunosorbent assays and indirect fluorescent antibody test.

To characterize IgM and IgG antibody responses in Rocky Mountain spotted fever (RMSF), a microtiter enzyme-linked immunosorbent assay (ELISA) using density gradient-purified Rickettsia rickettsii as antigen was developed. Sera of vaccinated individuals and patients with RMSF were tested by ELISA and by indirect fluorescent antibody (IFA) tests. Diagnostic agreement between ELISA and the IFA test was 76% and 52% for IgG and IgM antibody, respectively. Diagnostic agreement between the ELISA for IgG antibody and the IFA test for total immunoglobulins was 84%. The ELISAs for IgM and IgG antibody were as specific (100%) and as sensitive (100%) as the IFA test (83%-100%) in detecting antibody increases in paired sera from persons with RMSF and were superior to the IFA test in detecting seroconversions in vaccinees. The ELISA also detected antibodies in a single convalescent-phase serum with sensitivity and reliability. The ELISA for IgG antibody is appropriate for seroepidemiology and serodiagnosis since it permits measurement of antibody at a single dilution of serum up to a year after illness.

Adult↗
PubMed1983

Imipenem therapy of Pseudomonas aeruginosa bacteraemia in neutropenic rats.

Rats were made neutropenic by intraperitoneal (ip) injection of cyclophosphamide. Those neutropenic (mean white blood cell count of 470/mm3) rats were challenged intraperitoneally with Pseudomonas aeruginosa to assess the efficacy of single agent therapy with either imipenem, latamoxef (moxalactam) or amikacin, or combination therapy with imipenem-amikacin or latamoxef (moxalactam)--amikacin. Pharmacokinetic studies were performed in rats to assure that therapy was equivalent during therapeutic trials. Three levels of bacterial challenge (4 LD50, 13 LD50 and 250 LD50) were examined. At all challenge levels, single agent therapy with latamoxef (moxalactam) failed to significantly protect rats from fatal bacteraemia. Single-agent therapy with amikacin did significantly protect rats from fatal bacteraemia at the lower challenge levels, but not at the 250 LD50 challenge. Single agent therapy with imipenem significantly protected rats at all challenge. Single agent therapy with imipenem significantly protected rats at all challenge levels. In-vitro studies established a synergistic effect when combination antibiotics were used. This correlated with in-vivo findings that combination therapy resulted in improved rat survival and recovery of fewer Ps. aeruginosa isolates. The latamoxef (moxalactam)-amikacin combination was more effective than either agent alone, but was not more effective than imipenem alone. The imipenem-amikacin combination was the most effective therapeutic regimen tested. These results suggest that imipenem alone, and particularly when combined with an aminoglycoside, is effective in treating serious Ps. aeruginosa infections in neutropenic rats. Clinical studies in infected immunocompromised patients may be warranted.

Agranulocytosis↗
PubMed1983

Response of traumatized splenectomized patients to immediate vaccination with polyvalent pneumococcal vaccine.

In recent years the syndrome of overwhelming post-splenectomy sepsis has been increasingly reported in adults. Since more than 50% of these infections are caused by pneumococcus these post-splenectomy patients are considered a suitable group to receive the pneumococcal vaccine. Previous studies of the response obtained in post-splenectomy patients have been conflicting and we found no study that looked at the response to immediate vaccination in this group of patients. Sixteen consecutive multitraumatized patients received polyvalent pneumococcal vaccine 0.5 ml IM within 72 hours of splenectomy and 10 normal controls were given 0.5 cc polyvalent pneumococcal vaccine. Patients received an average of 19.2 units of blood and blood products; seven were on steroids for concomitant head injury. Antibody was measured by the radioimmune assay. Most of the subjects of both groups responded to at least seven of the 12 measured antigens and no patient in the control group and only one in the splenectomized group responded to all 12 antigens. When rate of response to individual serotypes was compared no difference was found between the two groups. Comparison of geometric mean fold rise and fold rise between the two groups for each of the 12 serotypes revealed essentially no difference. We conclude the response to polyvalent pneumococcal vaccine among polytrauma splenectomized patients is similar to that of normal controls, and that the vaccine can be administered immediately post-splenectomy.

Abdominal Injuries↗
PubMed1981

Model of intraabdominal abscess in mice.

Intraperitoneal inoculation of sterile mouse feces into mice produced intraabdominal abscesses. The addition of Bacteroides fragilis increased the incidence and the number of abscesses.

Abdomen↗
PubMed1977

Group B beta-hemolytic streptococcal colonization. Acquisition, persistence, and effect of umbilical cord treatment with triple dye.

Following an outbreak of group B beta-hemolytic streptococcal neonatal infection (GBS), a prevalence survey of GBS colonization was performed on 238 infants. No important differences were noted in the prevalence of colonization when the infants were grouped according to age. Follow-up of 24 colonized babies for three months disclosed that most had persistence of GBS at the rectum and pharynx. Local umbilical cord care with triple dye (TD) or hexachlorophene skin cleanser was compared with untreated controls with respect to rates of GBS colonization. At birth the colonization rates of the three groups were similar. The rate of acquisition of colonization with GBS was 1.0% in the TD group, 6.3% in the hexachlorophene group, and 8.3% in the control group. Triple dye was much more effective than no specific cord care or hexachlorophene in preventing acquisition of GBS colonization.

Acridines↗
PubMed1977

Pseudomonas species bacteremia caused by contaminated normal human serum albumin.

In May and June 1973, 11 patients on the surgical service at the University of Maryland Hospital had bacteremia caused by Pseudomonas species. Seven of the isolates recovered from blood cultures had the same antibiogram (sensitive only to chloramphenicol and tetracycline). Ten of the 11 patients were given 25% normal serum albumin (human) shortly before the onset of symptoms. In contrast, only two of seven patients with bacteremia due to Psuedomonas aeruginosa in May and June (P =0.013) and only nine of 20 patients located in surgical special care units during these months (P =0.014) were given this product. When cultured, the albumin in one of 54 previously unopened vials from the implicated lot yielded Pseudomonas cepacia sensitive only to chloramphenicol, tetracycline, and nalidixic acid. Subsequent investigation showed that five more patients in four other hospitals had symptoms of bacteremia shortly after the infusion of different lots of albumin from the same manufacturer, and in four cases P. cepacia was cultured from the suspect albumin. Since sterility testing by manufacturers may not detect low-frequency contamination, surveillance of nosocomial infections, investigation of unusual disease clusters, and prompt reporting of suspect reactions are essential in the control of such outbreaks.

Chloramphenicol↗
PubMed1977

Studies with a new generation of oral attenuated shigella vaccine: Escherichia coli bearing surface antigens of Shigella flexneri.

In an attempt to develop a safe, proliferating, oral, attenuated vaccine against shigellosis, genes that control the synthesis of group- and type-specific somatic antigens of Shigella flexneri 2a were transferred via conjugation to a recipient strain of Escherichia coli. The resultant hybrid (E. coli expressing shigella surface antigens) vaccine strain, PGAI 42-1-15, believed to have a complete (smooth) lipopolysaccharide, was given to volunteers in two vaccination-challenge studies. The vaccine was well tolerated and gave evidence of intestinal proliferation. In trial no. 1, volunteers given two doses of vaccine one month apart were challenged after eight weeks with 10(4) virulent S. flexneri 2a. Attack rates were comparable in vaccinees (50%) and controls (40%). In trial no. 2, vaccinees were given three weekly doses of vaccine and were challenged four weeks later with a small inoculum (10(2)) of S. flexneri 2a. Again, attack rates among vaccinees (47%) and controls (39%) were similar. It is unclear why this theoretically ideal, live shigella vaccine failed to protect against S. flexneri 2a.

Administration, Oral↗
PubMed1977

Evaluation of a UDP-glucose-4-epimeraseless mutant of Salmonella typhi as a liver oral vaccine.

A mutant (Ty21a) of Salmonella typhi, which lacks the enzyme uridine 5'-diphosphate-glucose-4-epimerase, was evaluated in volunteers for use as a live attenuated oral typhoid vaccine. Five to eight doses of vaccine (containing 3-10(10) viable organisms per dose) were given to 155 men without significant side effects. The rate of excretion of the vaccine strain in stools was low, and the majority of isolations occurred on day 1 after vaccination. Revertants able to fement galactose were not found in any of 958 stool isolates tested. The mutant, strain Ty21a, grown in brain-heart infusion broth (BHIB) with 0.1% galactose, produces more O side chain than the same vaccine strain cultivated without galactose. Volunteers vaccinated with strain Ty21a grown in galactose and then challenged with 10(5) virulen S. typhi were significantly protected from disease and also had decreased stool carriage of S. typhi as compared with controls. Strain Ty21a grown without galactose did not provide vaccinees significant protection nor decrease fecal excretion of S. typhi as compared with controls. Strain Ty21a, when grown in BHIB with 0.1% galactose, results in a safe, stable and protective oral vaccine that warrants further study in field trials.

Antibodies, Bacterial↗