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Biomedical subjects

M W Greene

Publications and source records attributed to M W Greene.

At least 19 recordsLinked to original sources
PubMed1999

Quantitation of IGF-I, IGF-II, and multiple insulin receptor family member messenger RNAs during embryonic development in rainbow trout.

The IGF system has been shown to be important for normal embryonic growth in mice. Characterization of the IGF system in lower vertebrates is still in progress. To gain a greater understanding of the IGF system during embryonic development in teleosts, a competitive reverse transcription-polymerase chain reaction (RT-PCR) assay was developed and used to quantitate the levels of IGF-I and IGF-II mRNAs from rainbow trout embryos isolated from a staged series. The absolute number of molecules of IGF-I mRNA/microg total RNA was significantly lower than the absolute number of molecules of IGF-II mRNA/microg total RNA both during early and late embryonic development. The recent identification of multiple IGF type I receptor (rtIGFR) and insulin receptor (rtIR) cDNAs in rainbow trout has provided us with a tool to investigate the expression of these mRNAs. A relative quantitative RT-PCR assay was used to determine the steady state levels of two forms of rtIGFR and three forms of rtIR mRNAs in rainbow trout embryos. The relative levels of rtIGFR mRNAs were greater in embryos compared to adult tissues while the relative levels of rtIR mRNAs were generally lower. In a RT-PCR based assay, a differential ability to detect rtIGFR and rtIR mRNAs was shown, suggesting developmental regulation of polyadenylation. Our results suggest that IGF-II mRNA is the predominant IGF expressed in rainbow trout embryos. Our characterization of IGF ligand and receptor mRNA levels in rainbow trout embryos suggests that a functional IGF system exists during embryonic development in teleosts.

Animals↗
PubMed1999

Characterization of teleost insulin receptor family members.

Insulin from mammals and fish has been used to determine insulin-binding affinities and receptor numbers with remarkable similarities between these two vertebrates, suggesting functional conservation. Yet, the nature and structure of teleost insulin receptors are not known. Therefore, the cloning and mRNA characterization of rainbow trout insulin receptors were undertaken. Three insulin receptor cDNAs were isolated by screening a cDNA library, confirmed as separate genes by genomic Southern hybridization, and designated as rainbow trout insulin receptor a (rtIR a), rainbow trout insulin receptor b (rtIR b), and rainbow trout insulin receptor c (rtIR c). A high degree of amino acid identity was observed between rainbow trout insulin receptors (rtIRs) and their human homolog, confirming the structural similarities between mammalian and fish insulin receptors. Reverse transcription-polymerase chain reaction from total RNA using either oligo(dT) or random hexamer primers resulted in a diminished ability to detect rtIR a and rtIR b mRNA when oligo(dT) was used, suggesting developmental and tissue-specific polyadenylation. The highest steady-state levels of rtIR mRNAs were consistently detected in juvenile and adult pyloric caeca (which also contained adipose and pancreatic tissue), while the lowest levels were consistently found in muscle. A high level of rtIR b and rtIR c mRNA was also found in ovary, while a high level of rtIR a was found in adult brain. Significant differences were also found between steady-state rtIR mRNA levels in corresponding juvenile and adult tissues. These results suggest a complex expression pattern of insulin receptor mRNAs in partial tetraploid fish.

Aging↗
PubMed1999

Characterization of teleost insulin receptor family members. II. Developmental expression of insulin-like growth factor type I receptor messenger RNAs in rainbow trout.

The insulin-like growth factor (IGF) system in teleosts consists of two ligands, IGF-I and IGF-II, multiple binding proteins, and high-affinity transmembrane receptors. There exists a large gap in our knowledge of the structure and expression of receptors mediating the biological effects of the IGFs in teleosts. For example, nucleotide sequence data other than those from the kinase domain, evidence of multiple genes, mRNA expression pattern and polyadenylation status in multiple tissues at different developmental stages, and quantitation of mRNA levels in multiple tissues are not known for any teleost. In the study described here, two rainbow trout IGF type I receptor cDNAs (rtIGFR Ia and rtIGFR Ib) were isolated by a 5' rapid amplification of cDNA ends method and confirmed as separate genes by genomic Southern blot hybridization. The predicted amino acid sequences are 85% identical to each other in the tyrosine kinase domain. Both cDNAs are more homologous to mammalian IGF type I receptors than to insulin receptors. Reverse transcription-polymerase chain reaction from total RNA using either oligo(dT) or random hexamers as primers resulted in a diminished ability to detect IGF receptor mRNAs when oligo(dT) was used, suggesting developmental and tissue-specific polyadenylation. The highest steady-state mRNA levels of rtIGFR Ia were found in juvenile gill and adult heart, while the highest levels of rtIGFR Ib were found in adult pyloric caeca, which also contained diffuse pancreatic and adipose tissue. The lowest steady-state mRNA levels of both rtIGFR Ia and rtIGFR Ib were found in juvenile heart, liver, muscle, and spleen, and adult liver. Significant differences in steady-state mRNA levels were also found between juveniles and adults. These results suggest a complex expression pattern of IGF type I receptor mRNAs in partial tetraploid fish.

Amino Acid Sequence↗
PubMed1998

Characterization of a teleost insulin-like growth factor II (IGF-II) gene: evidence for promoter CCAAT/enhancer-binding protein (C/EBP) sites, and the presence of hepatic C/EBP.

Insulin-like growth factor I (IGF-I) and IGF-II, acting under the regulatory control of growth hormone, are the principal mediators of vertebrate growth. We have previously demonstrated that like humans, but unlike rodents, rainbow trout maintain high hepatic IGF-II messenger RNA levels into adulthood. Here we describe a rainbow trout IGF-II gene with a proximal promoter that contains two CCAAT/enhancer-binding protein (C/EBP) binding sites (TCBS1 and TCBS2). Nuclear proteins corresponding in size to rat C/EBPalpha and C/EBPbeta were detected on Western immunoblots of growth-hormone-treated and mock-treated trout liver extracts. Electrophoretic mobility shift assay of these nuclear extracts further suggests the presence of C/EBPs in trout liver and confirms the ability of TCBS1 to form a complex with trout liver nuclear proteins that is identical in mobility and specificity to that formed by a mammalian consensus CBS construct. In both Western blot and mobility assay results, the growth-hormone-treated trout livers appeared to have a greater accumulation of C/EBP, suggesting a molecular mechanism by which growth hormone can influence the level of serum IGF-II.

Animals↗
PubMed1997

Temporal expression pattern of insulin-like growth factor mRNA during embryonic development in a teleost, rainbow trout (Onchorynchus mykiss).

The appearance of insulin-like growth factor I (IGFI) and II (IGF-II) mRNA was studied during rainbow trout embryonic development. Reverse transcription-polymerase chain reaction (RT-PCR), followed by Southern blotting and high-stringency hybridization with rainbow trout IGF-I and IGF-II cDNA probes, was used to detect all four forms of IGF-I mRNA and one form of IGF-II mRNA from whole-embryo total RNA isolated from a staged series. IGF-I and IGF-II mRNA were detected in unfertilized eggs. IGF-I and IGF-II mRNA were also detected during cleavage, gastrulation, and organogenesis, at hatching, during yolk absorption, and at feeding. IGF-IEa-1 and Ea-3 mRNA were detected in unfertilized eggs, while IGF-I Ea-4 was first detected at stage 9 when the zygotic genome is believed to become activated in rainbow trout. IGF-IEa-2 was not detected at any stage of embryonic development. IGF mRNA of immunoreactive peptides have been detected durin embryonic development in all vertebrates studied to date. Our results confirm the presence of IGF-I mRNA in teleost embryos. In addition, IGF-II mRNA is also present in teleost embryos. Our results suggest that the role IGF-I and IGF-II play during embryonic development may be conserved in vertebrates.

Animals↗
PubMed1989

Arthroscopy of the temporomandibular joint: an anatomic perspective.

Anatomic relationships in the temporomandibular joint (TMJ) region related to arthroscopic surgery were analyzed in cadaver dissections and dry skulls. The study showed that the maxillary artery and the main bifurcation of the facial nerve are located a safe distance from the usual arthroscopic approaches to the TMJ. The frontal branch of the facial nerve are located a safe distance from the usual arthroscopic approaches to the TMJ. The frontal branch of the facial nerve may be as close as 3 mm anterior to the midpoint of the lateral pole of the condyle. The neurovascular complex of the superficial temporal vessels and the auriculotemporal nerve may also be very close to puncture sites. The roof of the glenoid fossa had an average thickness of 0.9 mm. The external soft tissue auditory canal courses anteriorly to meet the bony external auditory canal. A skin puncture perpendicular to the bony canal was approximately 7 mm anterior to the posterior aspect of the tragus.

Arthroscopy↗
PubMed1989

Survey of TMJ arthroscopy in oral and maxillofacial surgery residency programs.

A questionnaire was mailed to oral and maxillofacial surgery residency programs in February 1988 regarding their indications for arthroscopy, number of patients treated, acquisition of skills, success of therapy, and several other questions about arthroscopy. Of the 56 questionnaires returned, 38 (68%) reported experience with TMJ arthroscopy. Pain and decreased range of jaw motion were the most frequently listed indications for surgery. Neural injuries were the most frequently seen complication. Four auditory canal perforations were reported. The operation was deemed successful in 64.8% of the patients. The most frequent criteria given for success were pain relief and increased range of motion. The main sources chosen by the respondents of this survey for acquiring skill in a residency program were information from the literature and hands-on training.

Arthroscopy↗
PubMed1988

Management of an oroantral fistula in a patient with Wilson's disease: case report and review of the literature.

After removal of an impacted maxillary third molar, an oroantral fistula developed in a patient with Wilson's disease. Management consisted of antibiotics, decongestants, irrigation, and surgical closure. Complications of treatment did not directly involve the disease but, rather, were related to the therapeutic agent penicillamine. Penicillamine causes interference between the cross links of tropocollagen molecules and cleaves newly formed molecules. Reduction in dosage is recommended when surgery is planned to increase collagen formation and, thus, healing. Such a measure was undertaken in this case. The patient healed uneventfully. A review of Wilson's disease and a case report are presented.

Adult↗
PubMed1977

Thallium-201 for medical use. Part 3: Human distribution and physical imaging properties.

Studies were undertaken to determine the biologic distribution of thallium-201 in man. The disappearance from the blood is extremely rapid and intracellular deposition is nearly immediate. The biologic half-time of thallium was measured by both the Brookhaven whole-body counter and the Donner whole-body scanner, with excellent agreement. The effective whole-body half-time of thallium-201 is about 57 hr. Concentration of activity was seen in the heart, kidneys, large bowel, and thyroid. The whole-body radiation dose is 0.21 rads/mCi.

Animals↗
PubMed1975

Thallium-201 for medical use. I.

Thallium-201 merits evaluation for myocardial visualization, kidney studies, and tumor diagnosis because of its physical and biologic properties. A method is described for preparation of this radiopharmaceutical for human use. A critical evaluation of 201Tl and other radiopharmaceuticals for myocardial visualization is given.

Cesium Isotopes↗
PubMed1975

Thallium-201 for medical use. II: Biologic behavior.

Thallium-201 has been evaluated for myocardial imaging by determining its distribution and assessing its imaging properties. Organ distribution with time was studied in goats, chosen for their large size and easy operability. Myocardial imaging was performed in living and sacrificed goats and also in two anesthetized dogs, without infarction. Infarcts were made by ligature at open chest surgery on the goats and the infarcts subsequently confirmed histologically. The myocardium of normal and infarced, young and old goats was cut into blocks and the isotope distribution measured and compared with that in the lungs, liver, spleen, and kidney in normal goats. The renal medulla-to-cortex concentration ratio in goats was studied and is approximately five. The heart uptake exceeds 3% for 100 min whereas contiguous organs have less than one-half of the myocardial concentration, and blood clearance is rapid. One problem may prove to be inhomogeneity of uptake of thallium in the "normal" myocardium, showing a standard deviation of 1u% in a young goat and 29% in an old goat. In view of the good myocardial uptake, however, this work strongly suggests the trial 201Tl in patients.

Animals↗