Biomedical subjects

M Alnaqeeb

Publications and source records attributed to M Alnaqeeb.

4 recordsLinked to original sources

PubMed2000

beta-glucuronidase activity is elevated in the rat harderian gland after bromocriptine but decreased after cyproterone acetate treatment or castration. Postcastrational effects on the ultrastructure of the gland.

OBJECTIVE: To investigate the effect of castration, bromocriptine and cyproterone acetate treatment on lysosomal hydrolytic enzymes and ultrastructure of the rat Harderian gland. METHODS: Groups of rats were subjected to the treatment by bromocriptine, cyproterone acetate and castration. Harderian glands were dissected from each experimental animal cut into small pieces and immediately stored in liquid nitrogen. Only those from castrated animals were fixed in Karnovsky fluid and processed for electron microscopy. The activity of acid phosphatase and ss-glucuronidase were estimated by kits from Sigma (St. Louis, Mo, USA). Semi-thin sections were stained with 1-% toluidine blue and ultra-thin sections with uranyl acetate and counter-stained with lead citrate. The examination was performed by Joel JEM-1200 EX II electron microscope. RESULTS: The treatment of male rats with the prolactin release inhibitor bromocriptine induced a significant increase in ss-glucuronidase activity. On the contrary, such activity was significantly decreased after treatment with the testosterone receptor antagonist cyproterone acetate as well as after castration. However, these treatments did not alter the activity of lysosomal acid phosphatase. Castration induced dramatic changes mostly in type A cells such as the appearance of lipid vacuoles with irregular forms and the predomination of smooth endoplasmic reticulum (SER) throughout the cytoplasm. The most dramatic postcastrational change was the degeneration of the mitochondria. These changes in type A cells might be due to the uneven distribution of the testosterone receptors in the rat Harderian gland, which are more numerous in type A cells. CONCLUSIONS: the gland physiology is responsive to alteration in circulating prolactin and testosterone levels.

Acid Phosphatase↗

PubMed1997

Changes in muscle fibre type, muscle mass and IGF-I gene expression in rabbit skeletal muscle subjected to stretch.

The relationship between IGF-1 and changes in muscle fibre phenotype in response to 6 d of stretch or disuse of the lower limb muscles of the rabbit was studied by combining in situ hybridisation and immunohistochemistry procedures. Passive stretch by plaster cast immobilisation of the muscle in its lengthened position not only induced an increase in IGF-I mRNA expression within the individual muscle fibres but also an increase in the percentage of fibres expressing neonatal and slow myosin. This change in phenotype was also found to be accompanied by a rapid and marked increase of muscle mass, total RNA content as well as IGF-I gene expression. In contrast, IGF-I appears not to be involved in muscle atrophy induced by immobilisation in the shortened position and the inactivity which results from this procedure. The level of increase in expression of IGF-I mRNA varied from fibre to fibre. By using adjacent serial sections, the fibres which expressed IGF-I mRNA at the highest levels were identified as expressing neonatal and the slow type 1 myosin. These data suggest that the expression of IGF-I within individual muscle fibres is correlated not only with hypertrophy but also with the muscle phenotypic adaptation that results from stretch and overload.

Adaptation, Physiological↗

PubMed1996

Cloning and characterization of an IGF-1 isoform expressed in skeletal muscle subjected to stretch.

To ascertain if IGF-1 is a regulator of local muscle growth, total RNA was extracted from rabbit muscle induced to undergo rapid hypertrophy using active stretch and from control muscles. This was analysed by Northern hybridization with a 280 base pair probe containing sequences derived from exons 3 and 4 of the insulin-like growth factor 1 gene. Two types of insulin-like growth factor 1 mRNA were shown to be strong expressed in the stretched muscles. In situ hybridization using the same probe (280 base pair) showed that IGF-1 is strongly expressed in muscle that is induced to grow rapidly and is expressed in the muscle fibres themselves. Using RT-PCR a single insulin-like growth factor 1 isoform cDNA (IGF-1Ea) could be cloned from the normal resting muscles. However, an additional isoform of insulin-like growth factor 1 (insulin-like growth factor 1Eb) was found to be expressed in stretched muscle undergoing hypertrophy. The E domain sequence of the additional isoform differs from the liver insulin-like growth factor 1Ea by the presence a 52 base pair insert. This changes the reading frame of the derived carboxyl-terminal resulting in a different precursor insulin-like growth factor 1 isoform. This insulin-like growth factor 1 mRNA probably encodes the precursor insulin-like growth factor 1 isoform that is responsible for local muscle growth regulation in response to mechanical stimulation. To confirm that alternative splicing of the insulin-like growth factor 1 gene occurs in muscle in response to physical activity, oligonucleotide primers were made which specifically amplify the cDNAs of two isoforms (insulin-like growth factors 1Ea and Eb) in the human as well as the rabbit. Following altered physical activity for 2 h to 6 days, appreciable levels of insulin-like growth factor 1Eb (in human the Ec) isoform were detected in skeletal muscle by using RT-PCR. In contrast very little if any of this splice variant could be detected in control muscle not subjected to stretch or extra physical activity.

Animals↗

PubMed1991

Collagen toxicity in rabbits.

Different preparations of soluble collagen, from rabbit skin, rat skin, rat tail tendon and guinea-pig skin, produced respiratory distress, agitation, convulsions and finally death when infused intravenously in lethal doses. Analysis of plasma enzyme levels indicated significant increases in total, cardiac and hepatic lactate dehydrogenase, suggesting that damage to the liver occurred as a result of collagen infusion. Histopathological examination of lungs, livers and hearts of collagen-treated rabbits confirmed that damage had occurred to the lungs and livers of these animals, while heart tissues appeared to be normal. The source of collagen did not appear to influence its toxicity at the tissue level.

Alanine Transaminase↗