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Biomedical subjects

M L Gutierrez

Publications and source records attributed to M L Gutierrez.

9 recordsLinked to original sources
PubMed1995

Black/white differences in prenatal care utilization: an assessment of predisposing and enabling factors.

OBJECTIVE: This article reports on analysis of the predisposing and enabling factors that affect black/white differences in utilization of prenatal care services. DATA SOURCES: We use a secondary data source from a survey conducted by the Michigan Department of Public Health. STUDY DESIGN: The study uses multivariate analysis methods to examine black/white differences in (1) total number of prenatal care visits, (2) timing of start of prenatal care, and (3) adequacy of care received. We use the model advanced by Aday, Andersen, and Fleming (1980) to examine the effect of enabling and predisposing factors on black/white differences in prenatal care utilization. DATA COLLECTION: A questionnaire was administered to all women who delivered in Michigan hospitals with an obstetrical unit. PRINCIPAL FINDINGS: Enabling factors fully accounted for black/white differences in timing of start of prenatal care; however, the model could not fully account for black/white differences in the total number or the adequacy of prenatal care received. CONCLUSION: Although there are no black/white differences in the initiation of prenatal care, black women are still less likely to receive adequate care as measured by the Kessner index, or to have as many total prenatal care contacts as white women. It is possible that barriers within the health care system that could not be assessed in this study may account for the differences we observed. Future research should consider the characteristics of the health care system that may account for the unwillingness or inability of black women to continue to receive care once they initiate prenatal care.

Adult↗
PubMed1993

Modulation of pp60v-src and pp60c-src expression in Rous sarcoma virus-transformed hamster fibroblasts transfected with activated N-ras.

Three phenotypically different hamster cell lines transformed with Rous sarcoma virus (RSV) were transfected with plasmid DNA containing an activated N-ras oncogene, and nine clones expressing various levels of p21N-ras were characterized. We examined the effects of p21N-ras on expression and kinase activity of resident src proteins by using a variety of assays that allowed us to discriminate between viral and cellular src proteins. In eight clones with a 10- to 20-fold increase in p21N-ras levels relative to the endogenous protein, we observed a marked reduction in the synthesis and kinase activity of p60v-src. This decrease correlated with transcriptional downregulation of RSV genomic and v-src subgenomic mRNAs. In the same cells, we found a concomitant accumulation of p60c-src and, accordingly, an increase in its protein kinase activity without an apparent increase in c-src mRNA levels. Therefore, modulation of viral and cellular src proteins in cells overexpressing p21N-ras appeared to result from two distinct effects: a downregulation of long terminal repeat-driven transcription and a more complex interaction with cellular effectors that control the stability of p60c-src. Such modulation also seemed to depend on the levels of p21N-ras and, possibly, on host-cell factors, since it was not observed in the third cell line, in which the relative increase in p21N-ras was only 2.5-fold to fivefold.

Animals↗
PubMed1988

Pharmacokinetics of leucovorin calcium after intravenous, intramuscular, and oral administration.

The pharmacokinetics of leucovorin was evaluated after intravenous, intramuscular, and oral administration in a randomized crossover study of 37 healthy men. A single 25-mg dose of leucovorin calcium was administered intravenously, intramuscularly, or orally to the subjects. Blood samples were obtained immediately before and at 13 time points up to 24 hours after the leucovorin dose. The three treatment phases were separated by one-week intervals. Bioavailability was assessed by measuring over 24 hours the blood concentrations of total folates, the parent compound 5-formyltetrahydrofolate, and the metabolite 5-methyltetrahydrofolate, using differential microbiologic assays with Lactobacillus casei and Streptococcus faecalis. Both intravenous and intramuscular administration produced rapid increases in serum concentrations of biologically active folates; these rises were sustained over time and were still detectable at 24 hours after drug administration. The bioavailability of intravenous and intramuscular doses was comparable based on area under the serum concentration-time curve, although for intramuscular administration, the peak concentration was lower and the time to peak concentration was longer. The initial rise in serum folate with intravenous and intramuscular dosing represented 5-formyltetrahydrofolate; this fell concomitantly with the appearance of 5-methyltetrahydrofolate. Oral leucovorin was 92% bioavailable compared with intravenous administration and produced a predictably different pattern of circulating folates, 5-methyltetrahydrofolate being the predominant form. Terminal elimination half-life, apparent volume of distribution, and clearance of total folate were not significantly different among the three treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1987

Absorption kinetics of orally administered leucovorin calcium.

Oral dose proportionality and pharmacokinetics of leucovorin [(d,l)-5-formyltetrahydrofolate (5-formyl-THF)] were studied in 30 healthy male subjects. In a randomized cross-over design, 24 fasted subjects were given 4 of a series of 5 single test doses between 20 and 100 mg, at 1-week intervals, of 5-formyl-THF as an oral solution of leucovorin calcium. Six separate subjects received 200 mg iv and po in a 2-way crossover. Blood and urine samples were collected over 24 hours for differential microbiological folate assays using Lactobacillus casei and Streptococcus faecalis. Using L casei activity to measure total serum folates, the area under the concentration-time curve from 0 to infinite time (AUC[0-infinity]) was calculated. Relative bioavailabilities were 78%, 62%, 49%, and 42% for the 40-, 60-, 80-, and 100-mg doses, respectively. Both the AUC and peak concentration (CPEAK) of total folates (consisting predominantly of the major metabolite, 5-methyltetrahydrofolate (5-methyl-THF], displayed significant deviation from linearity consistent with a saturation of folate absorption. Absolute bioavailability of the 200-mg oral dose of leucovorin based on AUC was 31% compared with that of the iv dose (6,848 vs. 22,298 ng.hr/ml, respectively). Total clearance, terminal half-life, and apparent volume of distribution of total folate at the 200-mg dose were not significantly different between the two routes of administration. Eighty-three percent of the biologically active iv dose was recovered in the urine within 24 hours, 31% as 5-methyl-THF. Twenty percent of the same oral dose was excreted in 24 hours, 16% as 5-methyl-THF. In contrast to the nondose-proportionality observed in total serum folates, AUC of the small component of S faecalis activity, which appeared earlier than 5-methyl-THF, displayed linear kinetics, suggestive of a distinct mechanism of uptake. As dose increased, S faecalis activity increased in relative proportion to L casei, indicating that saturation of the enzymatic bioconversion to 5-methyl-THF may also be occurring. In light of the demonstrated nondose-proportionality of total folates with oral leucovorin in this dose range, consideration should be given to parenteral administration in regimens employing higher doses. Oral administration should be at a level consistent with the capacity for efficient folate uptake.

Administration, Oral↗
PubMed1981

Phase II evaluation of mitomycin C (MMC) in children with refractory solid tumors using the single high-intermittent-dose schedule.

Nine evaluable patients with refractory solid tumors received mitomycin C as a single intravenous injection at a dose of 20 mg/m2 at 6- to 8-week intervals. Toxicity was tolerable. One patient with Wilms' tumor had a transient decrease in liver size. Pharmacokinetic data on three patients have suggested that the disposition of mitomycin C were comparable to those obtained in adults.

Adolescent↗
PubMed1978

Hepatic synthesis and albumin distribution in the primary nephrotic syndrome (PNS). as demonstrated by immunofluoresce.

To study some of the aspects of albumin homeostasis and proteinuria in PNS, the hepatic production of albumin is analyzed using semiquantitative immunofluorescent techniques, in biopsy specimens from nine subjects, free of hepatic or renal disease and nine patients with PNS, where renal biopsies were also made. Tissue sections 0.5 millimicron thick were cut. The hepatic synthesis of albumin, interpreted by the number of cells with specific fluorescence, was much higher in patients with PNS (p less than 0.001), and kept inverse relationship with serum albumin concentrations. Numberless droplets containing albumin were observed in the renal tissue indicating intense resorption and catabolism in the luminal and basal portions of the proximal convoluted tubules. Our findings indicate that, in PNS, albumin synthesis is substantially increased and hypoalbuminemia is caused by exaggerated renal excretion and catabolism.

Humans↗