Search PubMed⌕ Search

Biomedical subjects

M A Haidar

Publications and source records attributed to M A Haidar.

35 records · Page 2Linked to original sources
PubMed1990

Genomic structure of the human proliferating cell nucleolar protein P120.

A gene for human proliferating cell nucleolar protein p120 has been isolated from a human genomic library using p120 cDNA as a probe. The gene spanned 12 kilobase pairs and was composed of 15 exons and 14 introns. Unusual splice junction sequences, (AT) and (AC), instead of (GT) and (AG), respectively, were located at the splice sites for intron F. The 5' flanking region was analyzed for putative cis-acting factor binding sites. The region contained a TATA-like sequence and the CCAAT box. CAT assays indicated that the region -2532 /+ 102 was necessary for transcription. Two specific areas at -1444/-1224 and -537/-278 were shown to be important for transcription. Two "GC" boxes and two "GC"-rich sequences were observed Other sites upstream of these sites were analyzed for homology to other gene control regions.

Base Sequence↗
PubMed1987

Human renin is correctly processed and targeted to the regulated secretory pathway in mouse pituitary AtT-20 cells.

Renin is formed by intracellular processing of prorenin and catalyzes the conversion of angiotensinogen to angiotensin I, the precursor to angiotensin II. Several tissues synthesize prorenin. However, in man, the kidney is the only known source of circulating renin, raising the possibility that the processing enzyme is unique to that tissue. We have transfected a gene that directs prorenin synthesis in pituitary AtT-20 cells, which are capable of processing other prohormones. The results demonstrate that transfected AtT-20 cells can secrete inactive prorenin, accurately process prorenin to active renin, and be stimulated to release active renin in response to a secretagogue. These data imply that cellular elements capable of directing the processing of prorenin to renin and its correct subcellular compartmentalization may be present in nonrenal cell types and that critical elements of the regulated release of renin that occur in the kidney can be reconstituted in cells in culture.

Amino Acid Sequence↗
PubMed1984

Ontogeny, regional distribution and properties of thyroid-hormone receptors in the developing chick brain.

Studies on the thyroid-hormone receptors in the nuclei of developing chick brain revealed a single class of binding sites for tri-iodothyronine (T3) and thyroxine (T4) at all embryonic and adult ages. High-affinity [Ka = (1.85-3.3) X 10(9)M-1 and (0.3-0.6 X 10(9)M-1 for T3 and T4 respectively] receptors were detected in the brain as early as day 7 of embryonic development; their level increased progressively rapidly until day 13, and thereafter the value remained essentially constant during development. Occupancy of the receptor site with endogenous hormone was 75-90% at 7-11 days, 50-60% during the late phase of embryogenesis (13-17 days), and 80% after hatching. Comparison of the binding properties of the receptors with T3 and T4 indicates that, although the binding capacities per nucleus are almost identical, T4 has four to five times less binding affinity than T3. The half-lives of dissociation of solubilized T3- receptor complexes were 20-30h between 0 degrees and 7 degrees C, about 4h at 20 degrees C and less than 15 min at 37 degrees C. Studies of the regional distribution of receptors in the brain indicate that cerebrum has the highest concentration of T3 receptors (4000-7000 sites per nucleus); this concentration is 2-4-fold higher than that in the cerebellum, optic lobe or medulla oblongata. The overall results indicate that between 7 and 13 days of embryonic development the thyroid-hormone receptors in the embryonic chick brain, particularly in the cerebrum, assume a very high level and appear to be mostly saturated with endogenous hormone. This, and the temporal correspondence of the phenomenon with the period of neuronal growth and synaptogenesis, strongly indicate the influence of the hormone in the maturation of the developing brain.

Animals↗
PubMed1983

Thyroid hormone receptors of developing chick brain are predominantly in the neurons.

The relative concentration of the triiodothyronine (T3) receptors in the neuronal and glial nuclei of developing chick brain have been studied. Scatchard analysis indicate that the number of T3 binding sites in the neuronal nuclei increases from 400 to 1600 sites/nucleus between 7-11 day of embryonic development without any concomitant change in the level of glial nuclear receptors (130 - 200 sites/nucleus). Both sites are of high affinity (Ka = 1-3 x 10(9) M-1) at all ages examined. The abundance of the T3- receptors in the neuronal nuclei and the close coincidence of the period of rise in the level of these receptors in these nuclei (7-11 day) with that of maximal neuronal growth and synaptogenesis (7-13 day) suggest that the neurons are the primary site of action of T3 in the developing brain.

Animals↗
PubMed1976

Tobacco rattle virus RNA-protein interactions.

For the purpose of attempting to generalize the rules concerning morphogenesis of helical viruses, the in vitro reconstitution of the CAM strain of TRV was studied. The conditions for reconstitution and the importance of the aggregation state of the protein for initiation and elongation are compared with those of TMV. The initiation step consisting of the binding of RNA with the 36S disk of protein was easily accomplished. The polarity and the specificity of encapsidation of TRV RNA by homologous and heterologous viral protein is discussed.

In Vitro Techniques↗
PubMed1975

Serum alkaline phosphatase isoenzymes in sickle cell anemia.

Alkaline phosphatase isoenzymes in sera from patients with sickle cell anemia were separated by electrophoresis on starch gel. Physical and biochemical criteria identified bone alkaline phosphatase as the principal, although not necessarily the sole, enzyme fraction that increases during symptomatic sickle cell crises. Moreover, there appeared to be concordance between crisis severity, serum levels of alkaline phosphatase, and isoenzyme patterns; electrophoretic and biochemical abnormalities could be detected even when the patients were asymptomatic. The present data suggest that the serum alkaline phosphatase level may be an additional indicator of the degree, frequency, and persistence of tissue injuries that occur in sickle cell anemia.

Alanine Transaminase↗
PubMed1970

Porphyrin Biosynthesis in Cell-free Homogenates from Higher Plants.

The porphyrin and phorbin biosynthetic activity of etiolated cucumber (Cucumis sativus, L.) cotyledons was compared to that of cotyledonary homogenates. Etiolated cotyledons incubated with delta-aminolevulinic acid accumulate protoporphyrin, coproporphyrin, small amounts of Mg protoporphyrin monoester, and trace amounts of uroporphyrin. They also incorporate 4-(14)C-delta-aminolevulinic acid into free porphyrins, protochlorophyllide, protochlorophyllide phytyl ester, and Mg protoporphyrin monoester. Homogenates incubated with delta-aminolevulinic acid likewise accumulate coproporphyrin, uroporphyrin, Mg coproporphyrin, and trace amounts of protoporphyrin. They also incorporate 4-(14)C-delta-aminolevulinic acid into Mg protoporphyrin monoester, Mg coproporphyrin, and free porphyrins. However, the capacity to synthesize protochlorophyllide and protochlorophyllide phytyl ester is lost and the endogenous protochlorophylls gradually disappear. Mg protoporphyrin monoester represents the terminal biosynthetic step in this cell-free system.

Journal Article↗
PubMedDate not supplied

Ovarian activity before and after gonadal suppression by GnRH-a in patients with polycystic ovary syndrome, hyperandrogenism, hyperinsulinism and acanthosis nigricans.

OBJECTIVE: To investigate the ovarian activity before and after gonadal suppression with GnRH-analog in patients with PCO, hyperandrogenism, hyperinsulinism and acanthosis nigricans. DESIGN: Controlled clinical study. SETTING: Tertiary academic medical center. PATIENTS: Six patients with clinical findings of PCO, hirsutism and acanthosis nigricans. INTERVENTIONS: Morning blood samples in the follicular phase to determine the steroid levels, glucose and insulin curve, comparing to a control group. Administration for 2 consecutive months of a GnRH-analog, comparing, in the study group, the free testosterone levels before and after ovarian suppression. MAIN OUTCOME MEASURE: Determination of insulin levels in PCO, hirsutism and acanthotic patients and the free-testosterone levels before and after gonadal suppression. RESULTS: Insulin levels were significantly higher in the study group when compared to normal women during the glycemic test. We also found a significant decrease in the free-testosterone levels after 2 months of gonadal suppression with GnRH-analog when compared to the initial time. CONCLUSIONS: Patients with PCO, hirsutism and acanthosis nigricans present high levels of insulin, suggesting an ovarian hyperesponsiveness, which is not sustained when gonadotrophic blockage was achieved.

Acanthosis Nigricans↗
PubMedDate not supplied

Premature ovarian failure: morphological and ultrastructural aspects.

The authors documented by means of light and transmission electron microscopy that the ovaries of women with premature ovarian failure (POF) displayed dense connective tissue and rare corpora albicantia. Eight of the ten studied cases did not present ovarian follicles; in two cases, it was verified the presence of ovarian follicles, atypical primordial follicles and in one case, a corpus luteum was identified (after stimulation with exogenous gonadotrophin). Regarding the ultrastructural analysis, it was noted that the fibroblasts were united one to each other by cellular prolongations that formed a woof, constituting a cellular syncicius.

Adult↗
PubMedDate not supplied

Polycystic ovary syndrome: clinical and laboratory evaluation.

OBJECTIVE: To evaluate clinically, and with laboratory, tests, women with polycystic ovary syndrome (PCO). PATIENTS: One hundred and twelve women with PCO were studied. METHODS: The following data was recorded: Current age; age at menarche; menstrual irregularity, occurrence of similar cases in the family; fertility, obstetric history; body mass index (BMI); and presence of hirsutism. Serum measurements of follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, free testosterone, and dehydroepiandrosterone sulfate were taken. RESULTS: All patients presented either oligomenorrhea (31 percent), periods of secondary amenorrhea (9 percent), or both alterations (60 percent). The majority of the patients were infertile (75.6 percent). The LH/FSH ratio was higher than 2:1 in 55 percent of the patients and higher than 3:1 in 26.2 percent. The ultrasonographic aspect of the ovaries was considered to be normal in 31 percent. CONCLUSION: The main clinical feature of the PCO is the irregularity of menses since menarche, and that the laboratory tests would be important to exclude other disorders such as hyperprolactinemia or hyperandrogenemia caused by late-onset congenital adrenal hyperplasia.

Adolescent↗
PubMedDate not supplied

The ACTH test in the diagnosis of hirsutism.

The ACTH test has been used to confirm the diagnosis of adrenal insufficiency and the classic and the non-classic adrenal hyperplasia due to the 3-HSD, 21 OH e 110H deficiencies. This article reviews the historical aspects of the use of ACTH in the diagnosis of hirsutism and points out its mains indications. In spite of new biological molecular advances in the diagnosis of adrenal enzymatic deficiencies, the use of the ACTH test can help the physician to predict both genothipus and fenothipus in populations with hyperandrogenic manifestations due to non-classical or late-onset congenital adrenal hyperplasia.

Adrenocorticotropic Hormone↗
PubMedDate not supplied

The molecular biology of human renin and its gene.

The molecular biology of renin, prorenin, and the renin gene have been studied. A tissue-specific pattern of expression was found in rat and human tissues. In the human placenta, the transfected and endogenous renin promoters are active, and renin mRNA levels and transfected promoter activity are increased by a calcium ionophore plus cAMP. Cultured pituitary AtT-20 cells transfected with a preprorenin expression vector mimick renal renin release by converting prorenin to renin and releasing renin in response to 8Br-cAMP. Studies with mutant renin genes suggest that the body of renin directs renin to the regulated secretory pathway, and renin glycosylation affects its trafficking. Chinese hamster ovary cells were used to produce recombinant prorenin. Infused prorenin was not converted to renin in monkeys. Renin crystals were used to determine its three-dimensional structure. Renin resembles other aspartyl proteases in the active site and core, but it differs in other regions that probably explain renin's unique substrate specificity. Based on structural and mutational analysis, a model for human prorenin was built that suggests lysine -2 of the prosegment interacts with active site aspartate residues, and that the prosegment inactivation of renin is stabilized by binding of an amino terminal beta strand into a groove on renin.

Animals↗