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Biomedical subjects

A L Martinez

Publications and source records attributed to A L Martinez.

7 recordsLinked to original sources
PubMed1998

Accessing the embryo interior without microinjection.

For decades it has been assumed that in order to insert macromolecules into the embryo blastocoel for numerous experimental purposes, microinjection was required. Microinjection, however, can be only performed on a few embryos at a time, thus precluding many studies that could involve large populations of embryos. Laser scanning confocal microscopy, with its optical sectioning advantage, showed that fluorochrome-labeled macromolecular lectins and bovine albumin enter the blastocoel of living, swimming sea urchin embryos following a period of incubation without microinjection. A procedure is also described that shows macromolecular entry is substantially accelerated in low calcium seawater. The information gained from this study should greatly facilitate experiments on entire populations of millions of embryos at a time that require access of macromolecules to the embryo interior.

Animals↗
PubMed1998

Bone mineral, histomorphometry, and body composition in adults with growth hormone receptor deficiency.

Growth hormone (GH) and insulin-like growth factor I (IGF-I) deficiencies have been associated with osteopenia in both children and adults. To examine the effects of growth hormone resistance on bone mineral and body composition, we studied 11 adults (mean age 30 years) with growth hormone receptor deficiency (GHRD, Laron syndrome) and 11 age- and gender-matched controls from Southern Ecuador. Bone mineral and body composition were determined by dual-energy X-ray absorptiometry. Bone physiology was assessed with biochemical markers of bone turnover and dynamic bone histomorphometry. Bone size and body composition differed markedly between subjects with GHRD and controls. Affected adults were 40 cm shorter than controls, had significantly less lean body mass, and had increased percent body fat. Bone mineral content and density (BMD) at the spine, femoral neck, and whole body were significantly lower in adults with GHRD than in controls. Mean BMD Z scores were -1.5 to -1.6 at all sites in affected women and -2.2 to -2.3 in men with GHRD. Estimated volumetric bone density (BMAD) at the spine and femoral neck, however, was not reduced in GHRD. Spine BMAD was 0.210 +/- 0.025 versus 0.177 +/- 0.021 for affected women versus controls (p < 0.05) and 0.173 +/- 0.018 versus 0.191 +/- 0.025 for men with GHRD versus normals (p = 0.31). Urinary pyridinoline concentrations were significantly greater in adults with GHRD than in controls, while type I collagen C-telopeptide breakdown products and markers of bone formation did not differ. Differences in histomorphometry were limited to a reduction in trabecular connectivity; bone volume and formation rate were similar to controls. These data confirm the importance of the GH/IGF axis in regulating bone size and body composition. The contribution of these peptides to the acquisition and maintenance of bone mineral is less certain since volumetric bone density was preserved despite low levels of IGF-I and IGFBP-3 associated with GH resistance.

Absorptiometry, Photon↗
PubMed1995

A randomized, double blind, placebo-controlled trial on safety and efficacy of recombinant human insulin-like growth factor-I in children with growth hormone receptor deficiency.

GH insensitivity due to GH receptor deficiency is a rare autosomal recessive condition, characterized by deletions or mutations of the GH receptor gene. Patients are refractory to both endogenous and exogenous GH, resulting in severe growth retardation. Therapy with recombinant human insulin-like growth factor-I (rhIGF-I) can bypass the defect in the GH receptor and potentially stimulate growth. We previously identified a genetically homogeneous group of patients in southern Ecuador, thus providing a patient base for a controlled clinical trial of rhIGF-I therapy. Seventeen prepubertal patients were entered in a randomized, double blind, placebo-controlled trial. Subjects received either a 12-month course of rhIGF-I (120 micrograms/kg, sc, daily) or 6 months of placebo followed by 6 months of rhIGF-I. Subjects receiving rhIGF-I showed a significant increase in growth rate, which was sustained over the 1-yr course of therapy (from 2.9 +/- 0.6 to 8.6 +/- 0.4 cm/yr). Incidents of hypoglycemia were equal in frequency in the placebo and rhIGF-I groups. One recipient of rhIGF-I developed papilledema, which resolved spontaneously. rhIGF-I therapy did not alter serum IGF-binding protein-3 concentrations. rhIGF-I treatment is effective in stimulating skeletal growth in GH receptor deficiency. Although the therapy proved to be safe, the potent metabolic actions of rhIGF-I and the persistently low levels of serum IGF carrier protein necessitate continued careful observation for side-effects.

Adolescent↗
PubMed1994

Body changes in adolescent patients with growth hormone receptor deficiency receiving recombinant human insulin-like growth factor I and luteinizing hormone-releasing hormone analogue: preliminary results.

Auxological and body composition changes were studied in three adolescent patients (2 female, 1 male) with growth hormone receptor deficiency (GHRD) given insulin-like growth factor I (IGF-I), 120 micrograms/kg s.c. twice daily, plus a monthly intramuscular injection of 7.5 mg of a luteinizing hormone-releasing hormone (LHRH) analogue. Preliminary results from the first 12 months of the study show that height velocity was increased compared with the pretreatment values. This increase was probably due to the IGF-I therapy, as the LHRH analogue would have suppressed gonadotrophins and gonadal steroid production. There was a reduction in percentage body fat, and increases in lean mass and the lean:fat ratio, whole body mineral content and body calcium content, even when expressed per kg body weight. There was also a trend towards increased bone mineral density of the whole skeleton, lumbar spine and femoral structures, as well as a maturation of facial features. These preliminary results indicate that concomitant therapy with IGF-I and an LHRH analogue is safe and efficacious in inducing growth without advancing bone age in patients with GHRD.

Adolescent↗
PubMed1994

Heart rate increases in patients with growth hormone receptor deficiency treated with insulin-like growth factor I.

Cardiac function was measured in 16 prepubertal Ecuadorean patients with growth hormone receptor deficiency given insulin-like growth factor I (IGF-I) during part of a clinical trial. The IGF-I was given subcutaneously twice daily at a dose of 40 micrograms/kg on days 1 and 2, 80 micrograms/kg on days 3 and 4, and 120 micrograms/kg thereafter. Heart rate was determined at baseline (pretreatment) and on days 1-7 by repeated palpation of the radial artery and at baseline and on days 2, 4 and 7 by continuous portable Holter monitoring. Heart rate measured by both methods rose progressively with increasing doses of IGF-I. The mean palpated pulse exceeded baseline on each treatment day and was significantly higher on day 5 than day 4 and significantly higher on day 3 than day 2. The mean Holter heart rate was significantly higher on day 4 than on day 2 and significantly higher on day 2 than at baseline. Non-significant glucose and electrolyte changes did not appear to be associated with the cardiac events.

Adolescent↗
PubMed1991

Papillary carcinoma in thyroglossal duct remnants.

About 100 cases of carcinoma arising in thyroglossal remnants have been reported in the world literature. Five additional cases were discovered incidentally on histopathological examinations of specimens following Sistrunk's operation for removal of thyroglossal cysts and are now reported. The possibility of preoperative clinical diagnosis and the modalities of treatment are discussed.

Adenocarcinoma↗