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Biomedical subjects

M G Lee

Publications and source records attributed to M G Lee.

At least 19 recordsLinked to original sources
PubMed1995

Structure of a frequently rearranged rRNA-encoding chromosome in Giardia lamblia.

It has been shown previously that the rRNA encoding chromosomes in Giardia lamblia undergo frequent rearrangements with an estimated rate of approximately 1% per cell per division (Le Blancq et al., 1992, Nucleic Acids Res., 17, 4539-4545). Following these observations, we searched for highly recombinogenic regions in one of the frequently rearranged rRNA encoding chromosomes, that is chromosome 1, a small, 1.1 Mb chromosome. Chromosome 1 undergoes frequent rearrangements that result in size variation of 5-20%. We analyzed the structure of chromosome 1 in clonal lineages from the WB strain. The two ends of chromosome 1 comprise telomere repeat [TAGGG] arrays joined to a truncated rRNA gene and a sequence referred to as '4e', respectively. Comparison of the structure of four polymorphic versions of chromosome 1, resulting from independent rearrangement events in four cloned lines, located a single polymorphic region to the variable rDNA-telomere domain. Chromosome 1 is organized into two domains: a core region spanning approximately 850 kb that does not exhibit size heterogeneity among different chromosome 1 and a variable region that spans 185-450 kb and includes the telomeric rRNA genes, referred to as the variable rDNA-telomere domain. The core region contains a conserved region, spanning approximately 550 kb adjacent to the telomeric 4e sequence, which is only present in the 4e containing chromosomes and a 300 kb region of repetitive sequences that are also components of other chromosomes as well. Changes in the number of rDNA repeats accounted for some, but not all, of the size variation. Since there are four chromosomes that share the core region of chromosome 1, we suggest that the genome is tetraploid for this chromosome.

Animals↗
PubMed1995

Pharmacokinetics of methotrexate after intravenous and intramuscular injection of methotrexate-bearing positively charged liposomes to rats.

The pharmacokinetics and tissue distribution of methotrexate (MTX) were investigated after intravenous (IV) and intramuscular (IM) injection of free MTX (treatment I), freshly prepared MTX-bearing positively charged liposomes (large unilamellar vesicles), PLUVs (treatment II), and empty PLUVs mixed manually with free MTX (treatment III), 4 mg kg-1 as free MTX to rats, using HPLC assay. After 1 min IV infusion, the plasma concentrations of MTX (Cp), the area under the plasma concentration-time curve (AUC, 173 against 314 micrograms mL min-1), the terminal half-life (t1/2, 24.0 against 412 min), the mean residence time (MRT, 13.0 against 324 min), and the apparent volume of distribution at steady state (VSS, 289 against 3370 mL kg-1) were significantly larger, but the total body clearance (CL, 23.1 against 12.8 mL min-1 kg-1), the renal clearance (CLR, 8.38 against 3.09 mL min-1 kg-1), the non-renal clearance (CLNR, 14.6 against 9.56 mL min-1 kg-1), and the amount of MTX excreted in urine (Xu, 415 against 275 micrograms) were significantly lower in treatment II than in treatment I. This could be due to the fact that some of the MTX-bearing PLUVs were entrapped in tissues and the rest were present in plasma (larger MRT and Vss in treatment II), and MTX is slowly released from MTX-bearing PLUVs (longer t1/2 in treatment II). In the present HPLC assay, the concentrations of MTX represent the sum of free MTX and MTX in MTX-bearing PLUVs (larger Cp and AUC and slower CL in treatment II). Saturable formation of 7-hydroxymethotrexate from MTX was reported in rabbit blood and nonlinear disposition of MTX was also reported in rats and rabbits (lower Xu and CLR in treatment II). After 1 min IV infusion, some pharmacokinetic parameters of MTX, such as AUC, CL, CLR, CLNR, and Xu, were significantly different between treatments I and III, but nonetheless the differences were smaller than those between treatments I and II. After both IV and IM administration, the amount of MTX remaining per gram of tissue or organ in the kidney, stomach, small intestine, and large intestine was significantly smaller in treatment II than in treatment I.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1995

Pharmacokinetics and antitumour activity of a new anthracycline, DA-125, after intravenous administration to subcutaneously implanted Lewis-lung-carcinoma-bearing mice.

The pharmacokinetics and tissue distribution of M1-M4 were compared after intravenous (i.v.) administration of DA-125, 25 mg kg-1, to BDF1 mice (n = 5 at each sampling time) and subcutaneously implanted Lewis-lung-carcinoma-bearing BDF1 mice (n = 10 at each sampling time. The mean plasma concentrations of M1-M4 were not significantly different between the two groups of mice, and hence similar pharmacokinetic parameters for M1-M4 were obtained. The amount of M1 in the lung was significantly greater in the tumour-bearing mice than in the control mice, resulting in a greater AUAt in the tumour-bearing mice (18,600 against 8940 micrograms min g-1), and vice versa in the liver (962 against 3840 micrograms min g-1). However, the corresponding values for other tissues were comparable between the control and tumour-bearing mice. The amount of M1 was greatest in the lung for up to 2 h in the tumour-bearing mice. M2 was the predominant metabolite among M1-M4 excreted in 24 h urine by both groups of mice; 8.36 and 10.7% of the i.v. dose were excreted in 24 h urine as M2--expressed in terms of DA-125--by the control and tumour-bearing mice, respectively. The amount of M1 in the tumour mass reached a mean Cmax of 3.75 micrograms g-1 immediately after i.v. administration of DA-125 to the tumour-bearing mice, then declined very slowly to an amount that remained almost constant for up to 24 h. This suggested that M1 has high affinity for the subcutaneously implanted Lewis lung carcinoma. The antitumour activity, such as the increase in life span (ILS) and tumour growth inhibition (TGI) of DA-125, 6-48 mg kg-1, and adriamycin (ADM), 3-18 mg kg-1, were also compared in subcutaneously implanted Lewis-lung-carcinoma-bearing BDF1 mice after four weekly i.v. administration of the drugs on days 1,8,15, and 22 following tumour implantation. More than three out of six mice survived as tumour-free for longer than 70 d at a DA-125 dose range of 6-24 mg kg-1, but there were no tumour-free mice at any dose of ADM. Assuming ILS values higher than 30% to be effective, DA-125 doses ranging from 6 to 24 mg kg-1 were effective in increasing the life span, which ADM does only within the dose range of 6-12 mg kg-1.

Animals↗
PubMed1995

Effects of the rate and composition of fluid replacement on the pharmacokinetics and pharmacodynamics of intravenous bumetanide.

The effects of differences in the rate and composition of intravenous (i.v.) fluid replacement for urine loss on the pharmacokinetics and pharmacodynamics of bumetanide were evaluated with rabbit as the animal model. Each rabbit received a 4-h constant i.v. infusion of bumetanide at 1 mg/kg with 0% replacement (treatment I, n = 8), 50% replacement (treatment II, n = 6), and 100% replacement (treatment III, n = 7) with lactated Ringer's solution, in addition, another group of rabbits received 100% replacement with 5% dextrose in water (D-5-W, treatment IV, n = 4). Some pharmacokinetic parameters, such as the apparent volume of distribution at steady-state, mean residence time, and terminal half-life, remained relatively unchanged in all four treatments. Renal clearance and urinary excretion rate of the drug in treatments I-III were essentially the same, but were considerably higher than those in treatment IV. In spite of the similarities in kinetic properties (approximately 40% difference between lowest and highest values), the diuretic and/or natriuretic effects of bumetanide were markedly different among the four treatments. For example, the mean 8-h urine output values were 189, 317, 2170, and 306 mL for treatments I-IV, respectively, the corresponding 8-h sodium excretion values were 9.19, 16.5, 88.8, and 15.7 mmol, and the chloride excretion values were 10.8, 33.7, 77.4, and 11.7 mmol. Except for treatment III, diuresis and/or natriuresis were time dependent, generally decreasing with time until reaching a low plateau during later hours of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

A foreign transcription unit in the inactivated VSG gene expression site of the procyclic form of Trypanosoma brucei and formation of large episomes in stably transformed trypanosomes.

Transcription of the variant surface glycoprotein (VSG) gene expression site (ES) in Trypanosoma brucei is inactivated upon differentiation from the bloodstream form to the insect-adapted, procyclic form. This paper demonstrates that a foreign transcription unit, containing a procyclic acidic repetitive protein (PARP) gene promoter driving a neomycin phosphotransferase (neo) gene, can be fully active once integrated at the lingering, transcriptionally inactive VSG ES of procyclic trypanosomes. Following targeting into the ES two types of transformants were identified. Type one transformants were generated by integration of the PARP-neo gene into the region downstream of the long 70-bp repeat array of the silent telomeric ES encoding VSG gene 118. alpha-amanitin-resistant transcription at the neo locus proceeded from the PARP promoter to approximately 2.5 kb downstream of the integration site and terminated in front of the VSG 118 gene. Type two transformants contained variously sized large episomes (ranging from 135 kb to 500 kb), consisting of tandemly linked input plasmids. Transcription of the neo gene in the episomes was also resistant to alpha-amanitin. The presence of large amounts of the active episomal PARP promoter did not significantly affect the transcription of most RNA polymerase II transcribed genes, but resulted in a significant and equal reduction of the transcriptional efficiency of the endogenous PARP genes and VSG gene promoter sequences. This observation suggests that transcription of the PARP gene and the VSG gene expression sites in insect form trypanosomes may share a common transcriptional machinery.

Animals↗
PubMed1995

Effects of water deprivation for 48 hours on the pharmacokinetics and pharmacodynamics of furosemide in rats.

The effects of water deprivation for 48 h on the pharmacokinetics and pharmacodynamics of furosemide were examined after intravenous, 8 mg/kg body weight, and oral administration, 16 mg/kg body weight, of furosemide to control and water deprived rats. After i.v. administration, the total body and nonrenal clearances decreased significantly in water-deprived rats. The urine output, urinary excretion of sodium, potassium and chloride based on grams of kidney weight, and the diuretic, natriuretic and chloruretic efficiencies decreased significantly in water-deprived rats after both intravenous and oral administration of furosemide, suggesting that the dose of furosemide for water-deprived patients may require modification.

Administration, Oral↗
PubMed1995

Seroreversion of the serological tests for syphilis in the newborns born to treated syphilitic mothers.

BACKGROUND: IgG antibodies from mothers adequately treated for syphilis can cross the placenta and appear in the sera of healthy newborns without infection. In such infants, a false diagnosis of congenital syphilis is often made. We have designed a retrospective survey to determine the time of seroreversion of the serological tests for syphilis (STS) in uninfected newborns born to mothers who were adequately treated for syphilis. MATERIALS AND METHODS: Fifty two seropositive, untreated newborns born to 51 mothers treated for syphilis were studied. The newborns were followed at 1, 3, 6, 9, and 12 months of age until seroreversion was detected. The VDRL test was followed until 12 months in 12 of the 22 newborns who were positive at birth, the TPHA in 21 of the 46 newborns, and the FTA-ABS test in 22 of the 48 newborns. RESULTS: In the first serological tests done within 1 month after birth, the VDRL was positive in 22 newborns (42%), the TPHA in 46 (88%), and FTA-ABS in 48 (92%). The VDRL seroreverted within 6 months after birth in 84%, and within 1 year in 100%. The TPHA test seroreverted in 95% within 1 year after birth. The FTA-ABS test seroreverted in 100% within 1 year after birth. CONCLUSIONS: In most seropositive, untreated newborns born to treated mothers the VDRL became negative within 6 months after birth and the TPHA and FTA-ABS within 1 year. This result is consistent with current Centers for Disease Control (CDC) guidelines. However, although the CDC guidelines are adequate in general, we think that some revision is desirable concerning the IgM test and combination of the test results in order to rule out congenital syphilis in seropositive, nonsymptomatic newborns born to the treated mothers.

Female↗
PubMed1995

The constitutive expression of the immunomodulatory gp19k protein in E1-, E3- adenoviral vectors strongly reduces the host cytotoxic T cell response against the vector.

The immune response against cells infected by gene therapy vectors may be a major hindrance for gene therapy, destroying infected cells thus limiting the length of exogene expression and quickly eliminating infected cells on repeat administration. Adenoviruses and many other pathogens have evolved strategies for escape from immune surveillance, including the gp19k gene, found in the adenovirus E3 region, known to down-regulate major histocompatibility complex class 1 expression on the cell surface, and thus reduce lysis of the infected cells by cytotoxic T cells. We have constructed an adenoviral vector expressing the genes for beta-galactosidase and gp19k both under the control of constitutive promoters, and compared the capacity of lymphocytes from DBA/2 mice previously injected with the virus or with Ad-beta gal, a virus expressing beta-galactosidase but not gp19k, to lyse target cells infected with various viruses. Lymphocytes raised against Ad-beta gal fail to lyse target cells infected with Ad-beta gal-gp19k significantly, whereas Ad-beta gal infected target cells and a beta-galactosidase expressing cell line are strongly lysed. The administration of Ad-beta gal-gp19k fails to stimulate the proliferation of anti-vector lymphocytes, and thus these lymphocytes show poor cytotoxic activity against Ad-beta gal or Ad-beta gal-gp19k infected cells.

3T3 Cells↗
PubMed1995

Peptic ulcer disease and Jamaican patients' awareness of their disorder.

In the management and prevention of recurrence of peptic ulcer disease, patients' awareness of their disorder is essential. Fifty-one patients with peptic ulcer disease were studied regarding their awareness of their disorder and compliance with medications. There were 30 women and 21 men with a mean age of 45 years. Thirty-five per cent had secondary school education; 22% had tertiary training and 10% had no formal education. Sixty-three per cent of patients knew their ulcer location but 37% were unaware of their diagnosis. Twenty-nine per cent received most of their information from their pharmacists. Twenty per cent of patients smoked cigarettes; 31% drank alcohol, and 14% took non-steroidal analgesics. Seventy-six per cent thought that poor eating habits were a contributory cause of their ulcer; 39% thought that stress was a cause and 16% implicated heredity. Seventy-six per cent of patients took their medications daily, and 24% only when symptomatic. Jamaican patients' awareness of their ulcer disease is inadequate. There is a need for more physician education of their patients as well as public health promotion about peptic ulcer disease.

Adolescent↗
PubMed1995

Complete recovery of mice from a pre-established tumor by direct intratumoral delivery of an adenovirus vector harboring the murine IL-2 gene.

Direct introduction of exogenous genes into pre-existent tumors could provide an effective therapeutic approach for treatment of localized tumors. In this report we show that direct intratumoral delivery in animals of a replication-deficient adenovirus vector harboring the murine interleukin (IL)-2 gene (AD-mIL2) causes complete disappearance of P815 murine mastocytoma tumors in up to 75% of cases. Histological analysis of treated tumors revealed the presence of several zones of necrosis and the infiltration of macrophages and T cells. Moreover, the successfully treated animals develop a long lasting state of immunity during which further challenges with the tumor cells are rejected. To our knowledge this is the first successful in vivo treatment of an established tumor using adenoviral gene therapy methods.

Adenoviruses, Human↗
PubMed1994

The gene family of EF-hand calcium-binding proteins from the flagellum of Trypanosoma brucei.

The flagellum of Trypanosoma brucei contains calmodulin, and a separate family of antigenically related EF-hand calcium-binding proteins which we call calflagins. The following study evaluates the structure and genomic organization of the calflagin family. Genomic Southern blots indicated that multiple copies of calflagin genes occurred in T. brucei, and that all of these copies were contained in a single 23 kb XhoI-XhoI fragment on chromosomes 15 and 16 mRNAs of 1.2 and 1.6 kb were identified in bloodstream and procyclic life-cycle stages. Genomic fragments of 2.5 and 1.7 kb were cloned that encoded calflagin sequences. The calflagin genes were arranged tandemly along the genomic fragments. Three new members of the calflagin family were sequenced from a cDNA clone and the two genomic clones. Two unrelated families of 3' flanking sequences were downstream from the calflagin genes. An open reading frame that was unrelated to any calflagin sequence was at the 5' end of the 2.5 kb genomic fragment. The deduced amino acid sequences of the genomic clones (called Tb-24 and Tb-1.7g) were similar to the previously described Tb-17. Each encoded an approximately 24 kDa protein which contained three EF-hand calcium-binding motifs and one degenerate EF-hand motif. The cDNA encoded a protein (called Tb-44A) which was approximately twice as large as the other calflagins. The large size resulted from a nearly direct repeat of 186 amino acids. In general, variability among the T. brucei calflagins was greater than observed for related proteins from Trypanosoma cruzi. We demonstrate that this variability resulted from amino acid substitutions at the N-terminus, C-terminal extensions, and duplication of internal segments.

Amino Acid Sequence↗
PubMed1994

Simultaneous determination of a new anthracycline, DA-125, and its metabolites M1, M2, M3 and M4 in plasma and urine by high-performance liquid chromatography.

A high-performance liquid chromatographic method was developed for the simultaneous determination of a new anthracycline, DA-125 (I), and its metabolites (M1, M2, M3, and M4) in rat plasma and urine using fluorescein as an internal standard. Compound I, a prodrug of M1, is a beta-alanine derivative of M1, and only M1 shows antineoplastic activity. The method involved extraction or deproteinization followed by injection of 80-100 microliters of the aqueous layer or supernatant onto a C18 reversed-phase column. The mobile phases were 1% acetic acid-isopropyl alcohol-methanol (70:20:10, v/v) or 5 mM of ion-pairing chromatography reagent (IPC B8)-isopropyl alcohol-methanol (70:20:10, v/v) for the extraction or deproteinization methods, respectively. The flow-rate was 1.5 ml/min for both methods. The column effluent was monitored by a fluorescence detector with excitation wavelength of 488 nm and emission wavelength of 556 nm. The detection limits for M1, M2, M3, and M4 in rat plasma and urine were 50 ng/ml for all compounds using the extraction method, and 100, 50, 50, 50, and 50 ng/ml for I, M1, M2, M3 and M4 in rat plasma respectively, using the deproteinization method. No interferences from endogenous substances, adriamycin or daunorubicin were found.

Animals↗
PubMed1994

Determination of azosemide and its metabolite in plasma, blood, urine and tissue homogenates by high-performance liquid chromatography.

High-performance liquid chromatographic methods were developed for the determination of azosemide and its metabolite, M1, in human plasma and urine and rabbit blood and tissue homogenates. The methods involved deproteinization of the biological samples: 2.5 volumes of acetonitrile were used for the determination of azosemide and 1 volume of saturated Ba(OH)2 and ZnSO4 for that of M1. A 50-microliters aliquot of the supernatant was injected onto a C18 reversed-phase column in each instance. The mobile phases employed were 0.03 M phosphoric acid-acetonitrile (50:40, v/v) for azosemide and 0.03 M phosphoric acid/0.2 M acetic acid-acetonitrile (83:17, v/v) for M1. The flow-rate was 1.5 ml/min in both instances. The column effluent was monitored by ultraviolet detection at 240 and 236 nm for azosemide and M1, respectively. The retention times for azosemide and M1 were 6.0 and 8.3 min, respectively. The detection limits for both azosemide and M1 in both human plasma and urine were 50 ng/ml. The coefficients of variation of the assay were generally low (below 11.0%) for plasma, urine, blood and tissue homogenates. No interferences from endogenous substances or other diuretics tested were observed.

Animals↗