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R S Freeman

Publications and source records attributed to R S Freeman.

At least 19 recordsLinked to original sources
PubMed1992

Phosphorylation of conserved serine residues does not regulate the ability of mosxe protein kinase to induce oocyte maturation or function as cytostatic factor.

Expression of the mosxe protein kinase is required for the normal meiotic maturation of Xenopus oocytes and overexpression induces maturation in the absence of other stimuli. In addition, mosxe functions as a component of cytostatic factor (CSF), an activity responsible for arrest of the mature egg at metaphase II. After microinjection of Xenopus oocytes with in vitro synthesized RNA encoding either wild-type mosxe or kinase-inactive mosxe(R90), both proteins are phosphorylated exclusively on serine residues and exhibit essentially identical chymotryptic maps. Since the phosphorylated kinase-inactive mosxe(R90) protein was recovered from resting oocytes that have not yet begun to translate endogenous mosxe, this indicates that the major phosphopeptides of mosxe(R90) are phosphorylated by a preexisting protein kinase present in resting oocytes, and are not the result of autophosphorylation. The results presented here also indicate that the mosxe protein does not undergo significant phosphorylation at unique sites during oocyte maturation. If the biological activity of mosxe were regulated by phosphorylation, a site of regulatory phosphorylation would most likely be conserved among mos proteins of different species. Site-directed mutagenesis was used to construct 13 individual serine----alanine mutations at conserved residues (3, 16, 18, 25, 26, 57, 71, 76, 102, 105, 127, 211, and 258). These 13 mutants were analyzed for their abilities to induce oocyte maturation and to function as CSF. Results obtained with the mosxe(A105) mutant revealed that serine-105 is required for both maturation induction and CSF activity, even though serine-105 does not represent a major site of phosphorylation. All of the remaining serine----alanine mosxe mutants induced oocyte maturation and exhibited CSF activity comparable with the wild type. These results demonstrate that none of the conserved serines examined in this study function as regulatory phosphorylation sites for these biological activities. Peptide mapping of the remaining mosxe mutants identified serine-3 as a major phosphorylation site in vivo, which is contained within the chymotryptic peptide MPSPIPVERF.

Amino Acid Sequence↗
PubMed1991

Meiotic induction by Xenopus cyclin B is accelerated by coexpression with mosXe.

We have investigated the relationship between Xenopus laevis c-mos (mosXe) and the cyclin B component of maturation-promoting factor. Microinjection of Xenopus oocytes with in vitro-synthesized RNAs encoding Xenopus cyclin B1 or cyclin B2 induces the progression of meiosis, characterized by germinal vesicle breakdown (GVBD). By preinjecting oocytes with a mosXe-specific antisense oligonucleotide, we show that GVBD induced by cyclin B does not require expression of the mosXe protein. GVBD induced by cyclin B proceeds significantly faster than GVBD induced by progesterone or MosXe. However, coinjection of RNAs encoding cyclin B1 or cyclin B2 with mosXe RNA results in a 2.5- to 3-fold acceleration in GVBD relative to that induced by cyclin B alone. This acceleration of GVBD does not correlate with changes in the level of cyclin B1 and cyclin B2 phosphorylation.

Animals↗
PubMed1990

Effects of the v-mos oncogene on Xenopus development: meiotic induction in oocytes and mitotic arrest in cleaving embryos.

Previous work has demonstrated that the Xenopus protooncogene mosxe can induce the maturation of prophase-arrested Xenopus oocytes. Recently, we showed that mosxe can transform murine NIH3T3 fibroblasts, although it exhibited only 1-2% of the transforming activity of the v-mos oncogene. In this study we have investigated the ability of the v-mos protein to substitute for the mosxe protein in stimulating Xenopus oocytes to complete meiosis. Microinjection of in vitro synthesized RNAs encoding either the mosxe or v-mos proteins stimulates resting oocytes to undergo germinal vesicle breakdown. Microinjection of an antisense oligonucleotide spanning the initiation codon of the mosxe gene blocked progesterone-induced oocyte maturation. When oocytes were microinjected first with the mosxe antisense oligonucleotide, and subsequently with in vitro synthesized v-mos RNA, meiotic maturation was rescued as evidenced by germinal vesicle breakdown. The v-mos protein exhibited in vitro kinase activity when recovered by immunoprecipitation from either microinjected Xenopus oocytes or transfected monkey COS-1 cells; however, in parallel experiments, we were unable to detect in vitro kinase activity associated with the mosxe protein. Microinjection of in vitro synthesized v-mos RNA into cleaving Xenopus embryos resulted in mitotic arrest, demonstrating that the v-mos protein can function like the mosxe protein as a component of cytostatic factor. These results exemplify the apparently conflicting effects of the v-mos protein, namely, its ability to induce maturation of oocytes, its ability to arrest mitotic cleavage of Xenopus embryo, and its ability to transform mammalian fibroblasts.

Animals↗
PubMed1989

Xenopus homolog of the mos protooncogene transforms mammalian fibroblasts and induces maturation of Xenopus oocytes.

The oncogene v-mos transforms mammalian fibroblasts and encodes a serine/threonine protein kinase. Expression of the c-mos protooncogene is most abundant in germ cells, suggesting a normal role for c-mos in meiosis. Here we describe the isolation of cDNA clones containing the complete coding region of the Xenopus laevis homolog of c-mos (mosxe). The mosxe gene is transforming when introduced into murine NIH 3T3 cells, and transformation is abrogated by a lysine-to-arginine mutation in the canonical ATP-binding site. Microinjection of in vitro transcribed mosxe RNA into prophase-arrested Xenopus oocytes causes a resumption of meiosis, leading to germinal vesicle breakdown and oocyte maturation. Oocyte maturation was not observed after microinjection of in vitro transcribed mosxe RNA encoding the lysine-to-arginine mutation. These results demonstrate that the mosxe-encoded protein can induce progression through the cell cycle for both meiotic and mitotic cells and that this property is dependent on the presumptive ATP-binding domain in the protein kinase.

Amino Acid Sequence↗
PubMed1989

Transforming mutant v-mos protein kinases that are deficient in in vitro autophosphorylation.

We investigated the importance of specific serine residues for autophosphorylation and transformation by serine-threonine protein kinase p37mos. When either serine 326 or 358 was replaced with alanine, the resulting mutant protein retained the ability to transform NIH 3T3 cells but failed to autophosphorylate in vitro. These studies represent the first functional uncoupling of these two activities for p37mos.

Animals↗
PubMed1976

Systemic infection with Alaria americana (Trematoda).

Alaria americana is a trematode, the adult of which is found in mammalian carnivores. The first case of disseminated human infection by the mesocercarial stage of this worm occurred in a 24-year-old man. The infection possibly was acquired by the eating of inadequately cooked frogs, which are intermediate hosts of the worm. The diagnosis was made during life by lung biopsy and confirmed at autopsy. The mesocercariae were present in the stomach wall, lymph nodes, liver, myocardium, pancreas and surrounding adipose tissue, spleen, kidney, lungs, brain and spinal cord. There was no host reaction to the parasites. Granulomas were present in the stomach wall, lymph nodes and liver, but the worms were not identified in them. Hypersensitivity vasculitis and a bleeding diathesis due to disseminated intravascular coagulation and a circulating anticoagulant caused his death 8 days after the onset of his illness.

Adult↗
PubMed1976

Fatal human infection with mesocercariae of the trematode Alaria americana.

A fatal human infection with mesocercafiae of Alaria americana is described. Several thousand mesocercariae were estimated to be present in the peritoneal cavity, bronchial aspirate, brain, heart, kidney, liver, lungs, lymph nodes, pancreas, retroperitoneal adipose tissue, spinal cord, spleen, and stomach. Nine days from the onset of symptoms death resulted from asphyxiation due to extensive pulmonary hemorrhage probably caused by immun-mediated mechanisms. Circumstances suggest the victim probably ate inadequately cooked frog legs while hiking. Mesocercariae penetrated through the stomach wall and spread to the various organs both directly and via and circulatory system.

Adult↗
PubMed1976

Corrigia Obscura Sp. N. (Trematoda: Dicrocoeliidae) from the North American black duck.

Corrigia obscura sp. n. was found in the pancreatic ducts of a black duck, Anas rubripes. This is the first record of the genus Corrigia from an anseriform bird and from North America. Corrigia obscura differs from other Corrigia spp. by having a greater relative forebody length and greater relative body width. Noticeable hyperplasia and sloughing of the wall of the pancreatic ducts were associated with this infection.

Animals↗
PubMed1976

Survival of two trematode parasites (Diplostomum spp.) in mammalian eyes and associated pathology.

Cercariae of Diplostomum spathaceum dropped onto the eyes of small unanaesthetized rabbits penetrated through the cornea, crossed the anterior chamber, and entered the lens. After 2-3 weeks they died and became semi-permanent amorphous cataracts. Cercariae remaining in the cornea became the centres of stromal nebulae 0.1-0.2 mm across which remained visible for at least 3 months. Re-exposure produced marked conjunctival inflammation. Parasites applied to the eyes of large adult rabbits or cold-stored enucleated eyes of man entered the cornea but failed to penetrate as far as the anterior chamber. It is suggested that cercariae are unlikely to reach the lens of bathers because of the thickness of the human cornea. However, exposure to infection may result in temporary conjunctival inflammation and more persistant stromal nebulae. Cercariae of the closely related D. adamsi, did not penetrate or develop in the eyes of mammals.

Animals↗
PubMed1975

Penetration and survival of mesocercariae (Alaria spp.) in the mammalian eye.

A Canadian woman presented with a motile, intra-retinal worm, which by appearance and movement was strikingly similar to the mesocercaria of Alaria sp., a trematode from frogs. Using these mesocercariae and rabbits this study set out to establish 1) whether these mesocercariae can penetrate the cornea, 2) how long they might survive within the eye, and 3) what reaction is produced. It was found that some penetrated the cornea readily and, after injection, were capable of prolonged survival within the eye. Little overt reaction was produced though histologically the expected chronic inflammatory reaction with eosinophils occurred.

Animals↗
PubMedDate not supplied

Residual incomitant DVD following large bilateral superior rectus recession.

A recent survey of 25 experienced strabismus surgeons indicated that a very large superior rectus recession is the procedure of choice for DVD. We report a series of seven patients who exhibited a persistent DVD following large superior rectus recession. Furthermore, the DVD was markedly incomitant, much greater in adduction than in abduction. This residual DVD would mimic inferior oblique overaction on version testing, although proving to be purely DVD on critical observation. This "overaction" is apparently due to the marked weakening of the superior rectus and was not always predictive of the location and amount of persistent DVD. This previously unreported complication of large superior rectus recession is important to recognize so that alternative surgical approaches may be contemplated. It is hoped that more accurate observations and measurements both preoperatively and postoperatively will lead to a more orderly approach to DVD surgery.

Child↗
PubMedDate not supplied

The use of part-time occlusion for early onset unilateral exotropia.

Eleven patients (9 months to 5 years of age) with intermittent or constant exotropia of predominantly one eye on distant gaze were studied to investigate the effect of part-time occlusion. No patient had constant exotropia on near fixation. Visual acuity was found to be equal in both eyes. All patients were treated by part-time patching of the non-deviating eye from four to six hours a day and tapered as appropriate. If exotropia recurred after conversion to a heterophoria, part-time occlusion was reinstated. With occlusion, all patients converted to hetero- or orthophoria, at least temporarily. Mean follow-up (to last visit or surgical intervention) was 22 months (range 3 to 37 months). Three patients (27%) later developed constant exotropia (mean 28.3 months after beginning occlusion) and underwent surgery. Three patients (27%) became and remain orthophoric without further patching. Part-time occlusion for preschool patients with exodeviations that are predominantly unilateral can postpone surgical intervention and convert exotropia to orthophoria or exophoria.

Child, Preschool↗