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Biomedical subjects

J Mallol

Publications and source records attributed to J Mallol.

At least 91 records · Page 5Linked to original sources
PubMed1990

A possible specific receptor for 3-beta-androstanediol in the human sebaceous gland.

Dihydrotestosterone (DHT) does not seem to be the active specific metabolite of testosterone in hypertrophic sebaceous glands of subjects affected by male pattern baldness (MPB) and several results indicate that probably 3-beta-androstanediol (beta DIOL) could be an active form of testosterone in those glands. Cytosol and serum from several patients affected by MPB and subjected to hair autotransplantation, was incubated with both beta DIOL and 3-alpha-androstanediol (alpha DIOL). Binding patterns indicate that alpha DIOL binds to cytosolic proteins probably due to the contaminating sex hormone binding globulin (SHBG), whereas beta DIOL exhibits an atypical binding process in cytosol in the presence of high concentrations of non radioactive beta DIOL. This binding increases progressively up to 2 pmol/mg protein at the limit solubility conditions for the non radioactive steroid. This pattern is not observed in serum from the same patients, where the binding of beta DIOL is typically restricted to the SHBG. These results strongly suggest the existence of a specific beta DIOL-binding protein in the hypertrophic sebaceous glands and explain the lack of specific receptor for DHT in these tissues.

Alopecia↗
PubMed1990

Regional scalp differences of the androgenic metabolic pattern in subjects affected by male pattern baldness.

Regional differences in the androgen metabolism were established in alopecic and non alopecic areas of patients affected by male pattern baldness (MPB). 5-alpha-reductase (5-alpha-R) activity was measured by the formation of dihydrotestosterone (DHT), using 3H-testosterone as substrate: this activity was higher in the alopecic areas (3.4 pmol/g tissue/h) than in the non alopecic skin (1.5 pmol/g tissue/h). 3-alpha,beta-hydroxysteroid oxoreductase (3-alpha, beta-HO) was studied using 3H-DHT as precursor and measuring the corresponding formed 3-alpha- and 3-beta-androstanediols (alpha DIOL and beta DIOL). The beta DIOL was the predominant metabolite and total 3-alpha, beta-HO activity was higher in alopecic skin (12.4 pmol/g tissue/h) than in non alopecic areas (8.4 pmol/g tissue/h). Also 17, beta-hydroxysteroid oxoreductase was measured using either testosterone or DHT as substrates: androstenedione formed from testosterone was higher in hairy skin (12 pmol/g tissue/h) than in alopecic areas (6 pmol/g tissue/h); androstanedione formed from DHT was also higher in non alopecic areas (8.1 pmol/g tissue/h) than in alopecic skin (2.8 pmol/g tissue/h). The greater formation of beta DIOL in the sebaceous glands-enriched alopecic skin supports the hypothesis for a specific role of this metabolite in the control of the sebaceous activity.

3-Hydroxysteroid Dehydrogenases↗
PubMed1989

Beta-2-microglobulin in the assessment of renal function in full term newborns following perinatal asphyxia.

In order to evaluate the clinical usefulness of serum and urinary beta 2 microglobulin (beta 2-m) determination as a marker of renal damage following perinatal asphyxia, twenty asphyxiated and twenty healthy full term newborns were studied. Renal function was monitored on the first and third day after birth by traditional tests such as creatinine (Cr), endogenous creatinine clearance (Ccr), and fractional Na excretion (FeNa), as well as by serum and urinary beta 2 microglobulin. The value of different tests for the diagnosis of oliguria and of acute renal failure was determined. Eleven asphyxiated neonates developed oliguria and five ARF in contrast to none of the controls. Both traditional tests of renal function, and determinations of beta 2-m with the exception of serum beta 2-m, were significantly different (p less than 0.01) between controls and asphyxiated neonates. When stratified analysis was performed, only serum cr, urinary beta 2-m/cr ratio, and Fe beta 2-m were able to discriminate oliguria from preserved diuresis on the first day of life. For ARF, only Ccr and Fe beta 2-m were different, again on the first day of life. Urinary beta 2-m/creatinine ratio and Fe beta 2-m appear to be more sensitive and specific for the early detection of proximal tubular renal dysfunction following perinatal asphyxia than usual tests of renal function.

Asphyxia Neonatorum↗
PubMed1989

Factors affecting beta 2-microglobulin plasma concentration during hemodialysis.

We studied ten patients on hemodialysis (HD) treated in sequence with cuprophan (CU), ethylenevinylalcohol (EVAL), polyacrylonitrile (A-69) and polysulphone (PSP) membrane dialyzers. beta 2-microglobulin (beta 2m) was measured by radioimmunoassay in plasma and dialysate samples. Plasma concentrations were corrected for changes in extracellular volume (ECV). We also studied adsorption in vitro by incubating the above membranes with I-125-labelled beta 2m. There were no changes in beta 2m plasma concentration after HD with CU dialyzers, but a significant decrease was observed with the other membranes tested. Filtration of beta 2m across the dialyzer was absent with CU and minimal with EVAL. However, large amounts were recovered from dialysate with the high-permeability dialyzers, AN-69 and PSP. In vitro studies showed that maximal adsorption capacity was obtained with AN-69 (13%) compared to 9% with CU, 4% with EVAL and 7% with PSP. In summary, beta 2m clearance with PSP is achieved through greater removal of this protein by mass transport across the membrane. The mechanism by which beta 2m is removed from blood during AN-69 dialysis seems to include both adsorption to and filtration by the membrane itself.

Adolescent↗
PubMed1988

Effect of chloral hydrate on arterial oxygen saturation in wheezy infants.

Chloral hydrate is commonly used to sedate infants for pulmonary function tests and other investigations. However, sedation is generally not recommended for infants with acute wheezing illnesses. The commonly used dose range exceeds the maximum recommended dose; however, the effects of this dosage regimen during pulmonary function testing have not been studied. The present study shows that 70-100 mg/kg of chloral hydrate, a dose commonly used to sedate infants for pulmonary function testing, causes a fall in arterial oxygen saturation and a decrease in clinical score of infants recovering from acute viral bronchiolitis, but not in infants with clinically stable cystic fibrosis. These findings suggest that wheezy infants with baseline SaO2 less than or equal to 94% are more susceptible to central respiratory depression following sedation with chloral hydrate. The results of the present study raise serious doubts about the advisability of sedation with chloral hydrate, in the currently used doses, in wheezy infants.

Bronchiolitis, Viral↗
PubMed1988

Inherent variability of pulmonary function tests in infants with bronchiolitis.

During the last decade, many new methods of assessing pulmonary function in infants have been introduced. However, considerable controversy has arisen when these different techniques are used to assess the efficacy of various inhaled medications. The currently employed measures of pulmonary function have been reported to have coefficients of variation of less than 10%. However, these figures refer to repeated measurements made in individual babies over a short period of time, with the infant in a constant position. They may not be applicable to studies on the effects of drugs when a significant time interval elapses between measurements, particularly if the infant is repositioned during this time. In the present study, we found that the variability of measurements of thoracic gas volume (TGV), passive respiratory mechanics, and forced expiration approximately doubled if the infant was taken out of the plethysmograph, or repositioned within the plethysmograph, between sets of measurements. The between-test coefficients of variation ranged from 4.8% to 18.9% for TGV, 7.8% to 23.5% for respiratory system resistance, from 5.0% to 24.1% for respiratory system compliance, and from 10.8% to 36.1% for maximal flow at functional residual capacity. These results demonstrate that the commonly employed infant pulmonary function tests have wide variability in infants with acute wheezing illnesses. Before studying the efficacy of therapeutic interventions in such infants, it is necessary to establish the individual variability of the tests in the infants under the conditions of the study. Failure to do so may result in erroneous conclusions and recommendations.

Bronchiolitis, Viral↗
PubMed1988

Isolation and characterization of bovine brain myelin distribution of 5'-nucleotidase.

Myelin was isolated from bovine brain by several published procedures and modifications of these procedures. High activity of the myelin marker (2',3'-cyclic nucleotide 3'-phosphohydrolase) and low activity of contaminants markers in white matter homogenates in respect to cerebral cortex showed the white matter to be better than the cerebral cortex or the whole brain for myelin isolation. A procedure is described for the preparation of purified myelin from bovine white matter which yielded a content of protein (40%), myelin marker (51%), and 5'-nucleotidase (25%) in purified myelin higher than by any used method. Acetylcholinesterase or succinate dehydrogenase was lower than 7% of its activity in the white matter homogenate, and monoamine oxidase and NADPH:cytochrome c reductase were not recovered in myelin fraction. Morphologically, myelin fraction was shown to mainly consist of multilamellar membranes of different sizes. Sodium dodecyl sulphate polyacrylamide gel electrophoresis of myelin fraction showed a characteristic protein pattern of myelin. When our procedure was applied to frozen white matter, lower protein (32%) and myelin marker (34%) and similar 5'-nucleotidase activity (24%) were recovered in myelin, increasing its recovery in denser fractions of white matter.

5'-Nucleotidase↗
PubMed1988

Localization of 5'-nucleotidase in bovine brain myelin fraction and myelin subfractions.

Purified myelin from fresh calf brain white matter was subfractionated in a discontinuous sucrose gradient; significant recovery of protein and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP) and 5'-nucleotidase (5'N) activities occurred in all three obtained subfractions, the highest recovery being in the light subfraction; highest 5'N and CNP specific activities were in medium myelin. Purified myelin was also subfractionated in a continuous sucrose gradient, with a similar localization of protein; CNP activity and 5'N activity maxima suggest that myelin may be a predominant locus of 5'N in bovine brain white matter. Freezing of brain white matter caused an increase in protein and in CNP and 5'N total activity recoveries in denser myelin subfractions. Cytochemistry showed the reaction product of 5'N in the whole myelin fraction to be associated with the innermost, outermost and medial compact myelin layers. Effects of non-ionic detergent (LUbrol WX) on 5'N activity were studied, and the results also suggest the intrinsic nature of 5'N as an ectoenzyme in myelin membranes. Lubrol WX was viewed as an advisable detergent for the stimulation of myelin 5'N activity, but not for the solubilization of this enzyme.

5'-Nucleotidase↗
PubMed1987

Effects of maternal iodine deficiency on thyroid hormone economy of lactating dams and pups: maintenance of normal cerebral 3,5,3'-triiodo-L-thyronine concentrations in pups during major phases of brain development.

Female rats were fed a diet with a low iodine content (LID), or the same LID supplemented with KI, and mated. Fetuses were obtained at 17 and 21 days of gestation, or pups were killed at different ages after birth. The dams on LID were markedly iodine deficient and developed a large goiter. Their thyroidal iodine content was only 4% of that of LID + I dams. The iodine deficiency of the LID mothers was severe enough to result in very low plasma T4 levels and in hepatic and cerebral T3 deficiency, despite normal circulating levels of T3. The fetuses from LID dams had low concentrations of iodine in their placentas and thyroid glands, and were deficient both in T4 and T3 in all tissues studied, including the brain. After birth, however, suckling LID pups were able to increase the plasma T4 to levels which were higher than those found in either LID fetuses or in adult LID progeny, although plasma T4 was always lower than in age-paired LID + I animals. This increase in T4 was probably due to an approximately 5-fold increase in iodine intake while suckling. Milk from LID mothers was found to contain 22% of the amount of iodine found in milk from LID + I dams, in contrast to their iodine intake, which was about 4% that of the LID + I rats. Cerebral T3 levels were the same for LID and for LID + I pups throughout most of the postnatal period of brain development. This finding might explain the difficulties encountered in obtaining an experimental model of neurological cretinism in rats.

Animals↗
PubMed1987

Physiopathological role of bald-scalp cytosolic proteins.

The physiopathological role of androgen binding proteins in male pattern baldness (MPB) has been studied by using tritiated dihydrotestosterone (DHT) and methyltrienolone (R 1881) as ligands. DHT binding in bald scalp from subjects suffering from MPB is high (53 +/- 12 fmol/mg protein) in cytosol obtained from bald areas, being undetectable in hairy areas from the same subject. Since methyltrienolone does not bind in bald scalp cytosol, there must be no specific DHT receptor in this material. Several kinetic and molecular parameters of DHT binding in bald scalp cytosol and serum were similar in both samples. Only the association rate constant (k+1) was significantly higher in serum (8.8 X 10(6) M-1 min-1) than in cytosol (3.08 X 10(6) M-1 min-1). DHT binding in serum as well as the evaluation of plasma contamination in the skin samples (by nephelometric analysis) strongly suggests that DHT binding in skin cytosol is merely due to the presence of contaminating SHBG but it does not explain the lack of DHT binding in non bald areas. Thus, the possibility arises of there being a specific mechanism for the uptake of the plasmatic testosterone SHBG-complex taking place only in the hypertrophic sebaceous gland as well as the existence of active T metabolites other than DHT, probably 3 beta-androstanediol.

Alopecia↗
PubMed1986

Effects of maternal iodine deficiency on the L-thyroxine and 3,5,3'-triiodo-L-thyronine contents of rat embryonic tissues before and after onset of fetal thyroid function.

Female rats were placed on a low iodine diet (LID) or LID supplemented with KI. They were mated 3-6 months later. Maternal and embryonic tissues were obtained both before the onset of fetal thyroid function, at 11 and 17 days of pregnancy, and at 21 days of gestation. T4 and T3 concentrations were measured by RIA. T4 concentrations were very low in the plasma, liver, and lung of LID dams and in all embryonic samples obtained from such mothers, namely 11-day-old embryotrophoblasts, 17-day-old placentas and embryos, 21-day-old placentas, embryos, plasma, liver, lung, and carcass (whole embryos minus the trachea, thyroid, blood, liver, and brain). T3 was low in 17-day-old placentas and embryos and in all fetal tissues obtained at 21 days of gestation from LID dams. These results show that when iodine deficiency is severe enough to result in very low maternal plasma T4 levels, embryonic tissues are deficient in T4 and T3 both before and after the onset of fetal thyroid function. This finding might be relevant to the etiopathology of human iodine deficiency disorders.

Animals↗