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Biomedical subjects

S J Roberts

Publications and source records attributed to S J Roberts.

At least 19 recordsLinked to original sources
PubMed1992

Localization of (-)-[125I]cyanopindolol binding in guinea-pig heart: characteristics of non-beta-adrenoceptor related binding in cardiac pacemaker and conducting regions.

Receptor autoradiography was used in guinea-pig heart to locate binding sites for the beta-adrenoceptor ligand (-)[125I]cyanopindolol (CYP) resistant to blockade by the beta-adrenoceptor antagonist (-)-propranolol (1 microM). Highly localized binding was observed to regions closely associated with the sinoatrial node, atrioventricular node and bundle of His but was not observed on myocardial, pacemaker, conducting cells or adipose tissue. Free [125I] also bound to identical sites. Binding was enhanced in the presence of ascorbic acid but was completely inhibited by (-)-isoprenaline (100 microM), serotonin (5-HT) (10 microM) and phentolamine (10 microM).

Alprenolol↗
PubMed1992

Variations in blood flow to and from the bovine mammary gland measured using transit time ultrasound and dye dilution.

Blood flow across the lactating bovine mammary gland was measured by two techniques. The use of transit time flow probes appeared to give flows which correlated well with dye dilution in only one of five cows, although the relative changes in flow were similar between the techniques in four of the cows. Further studies were made on the effect of posture on mammary blood flow using both techniques. The crossover of venous blood from one side of the mammary gland was also studied using the dye dilution technique, and revealed large differences between animals and also with posture. These observations suggest that particular care should be taken when sampling blood from the milk vein of cows, if a representative sample is required. Changes in blood flow with posture may be indicative of a repartitioning of flow within the body, and the physiology of such a mechanism would be of interest in itself. The control of this mechanism may be useful in modifying blood flow to the mammary gland and thus milk yield, since blood flow is related to the level of milk production.

Animals↗
PubMed1992

V3 loop region of the HIV-1 gp120 envelope protein is essential for virus infectivity.

The mechanism by which HIV-1 mediates cell fusion and penetrates target cells, subsequent to receptor (CD4) binding, is not well understood. However, neutralizing antibodies, which recognize the principal neutralizing determinants of the gp120 envelope protein (the V3 loop region, residues 296 to 331), have been shown to effectively block cell fusion and virus infectivity independent of the initial gp120-CD4 binding. To investigate the role of the V3 loop in an HIV infection, a series of site-specific mutations were introduced into the HIV-1 envelope gene. Specifically, each residue (312 to 315) in the strongly conserved tetrapeptide sequence, GPGR, which is positioned in the center of the V3 loop domain was individually altered. The processing, transport, and CD4 binding properties of the mutant envelope proteins were comparable to those of the wild-type protein, however, none of the mutants were able to form syncytia in the HeLa-T4 assay. Molecular HIV-1 clones containing mutations altering the G312, G314, or R315 residues produced noninfectious virions, whereas a clone with a P313A mutation was found to be infectious. These results demonstrate that certain V3 loop mutations can be lethal and clearly indicate that this region of the HIV-1 gp120 protein is essential for virus infectivity.

Amino Acid Sequence↗
PubMed1992

The establishment of polarized membrane traffic in Xenopus laevis embryos.

Delineation of apical and basolateral membrane domains is a critical step in the epithelialization of the outer layer of cells in the embryo. We have examined the initiation of polarized membrane traffic in Xenopus and show that membrane traffic is not polarized in oocytes but polarized membrane domains appear at first cleavage. The following proteins encoded by injected RNA transcripts were used as markers to monitor membrane traffic: (a) VSV G, a transmembrane glycoprotein preferentially inserted into the basolateral surface of polarized epithelial cells; (b) GThy-1, a fusion protein of VSV G and Thy-1 that is localized to the apical domains of polarized epithelial cells; and (c) prolactin, a peptide hormone that is not polarly secreted. In immature oocytes, there is no polarity in the expression of VSV G or GThy-1, as shown by the constitutive expression of both proteins at the surface in the animal and vegetal hemispheres. At meiotic maturation, membrane traffic to the surface is blocked; the plasma membrane no longer accepts the vesicles synthesized by the oocyte (Leaf, D. L., S. J. Roberts, J. C. Gerhart, and H.-P. Moore. 1990. Dev. Biol. 141:1-12). When RNA transcripts are injected after fertilization, VSV G is expressed only in the internal cleavage membranes (basolateral orientation) and is excluded from the outer surface (apical orientation, original oocyte membrane). In contrast, GThy-1 and prolactin, when expressed in embryos, are inserted or released at both the outer membrane derived from the oocyte and the inner cleavage membranes. Furthermore, not all of the cleavage membrane comes from an embryonic pool of vesicles--some of the cleavage membrane comes from vesicles synthesized during oogenesis. Using prolactin as a marker, we found that a subset of vesicles synthesized during oogenesis was only released after fertilization. However, while embryonic prolactin was secreted from both apical and basolateral surfaces, the secretion of oogenic prolactin was polarized. Oogenic prolactin was secreted only into the blastocoel (from the cleavage membrane), none could be detected in the external medium (from the original oocyte membrane). These results provide the first direct evidence that the oocyte synthesizes a cache of vesicles for specific recruitment to the embryonic cleavage membranes which are polarized beginning with the first cleavage division.

Animals↗
PubMed1992

Truncation of the human immunodeficiency virus type 1 transmembrane glycoprotein cytoplasmic domain blocks virus infectivity.

Human immunodeficiency virus type 1 contains a transmembrane glycoprotein with an unusually long cytoplasmic domain. To determine the role of this domain in virus replication, a series of single nucleotide changes that result in the insertion of premature termination codons throughout the cytoplasmic domain has been constructed. These mutations delete from 6 to 192 amino acids from the carboxy terminus of gp41 and do not affect the amino acid sequence of the regulatory proteins encoded by rev and tat. The effects of these mutations on glycoprotein biosynthesis and function as well as on virus infectivity have been examined in the context of a glycoprotein expression vector and the viral genome. All of the mutant glycoproteins were synthesized, processed, and transported to the cell surface in a manner similar to that of the wild-type glycoprotein. With the exception of mutants that remove the membrane anchor domain, all of the mutant glycoproteins retained the ability to cause fusion of CD4-bearing cells. However, deletion of more than 19 amino acids from the C terminus of gp41 blocked the ability of mutant virions to infect cells. This defect in virus infectivity appeared to be due at least in part to a failure of the virus to efficiently incorporate the truncated glycoprotein. Similar data were obtained for mutations in two different env genes and two different target cell lines. These results indicate that the cytoplasmic domain of gp41 plays a critical role during virus assembly and entry in the life cycle of human immunodeficiency virus type 1.

Animals↗
PubMed1992

Mutations in the leucine zipper of the human immunodeficiency virus type 1 transmembrane glycoprotein affect fusion and infectivity.

Many retroviruses, including the human and simian immunodeficiency viruses, contain a leucine zipper-like repeat in a highly conserved region of the external domain of the transmembrane (TM) glycoprotein. This region has been postulated to play a role in stabilizing the oligomeric form of these molecules. To determine what role this region might play in envelope structure and function, several mutations were engineered into the middle isoleucine of the leucine zipper-like repeat of the human immunodeficiency virus type 1 (HIV-1) TM protein. A phenotypic analysis of these mutants demonstrated that conservative mutations (Ile to Val or Leu) did not block the ability of the viral glycoprotein to mediate cell-cell fusion or affect virus infectivity. In contrast, each of the other mutations, except for the Ile-to-Ala change, completely inhibited the ability of the glycoprotein to fuse HeLa-T4 cells and of mutant virions to infect H9 cells. The alanine mutation produced an intermediate phenotype in which both cell fusion and infectivity were significantly reduced. Thus, the biological activity of the glycoprotein titrates with the hydrophobicity of the residue in this position. None of the mutations affected the synthesis, oligomer formation, transport, or processing of the HIV glycoprotein complex. Although these results do not rule out a role for the leucine zipper region in glycoprotein oligomerization, they clearly point to a critical role for it in a post-CD4 binding step in HIV membrane fusion and virus entry.

Amino Acid Sequence↗
PubMed1991

Localization and characterization of two propranolol resistant (-) [125I]cyanopindolol binding sites in rat skeletal muscle.

Autoradiographic studies were performed in sections of rat gastrocnemius, plantaris and soleus muscle bundles with (-)-[125I]cyanopindolol (59-69 pM) in the presence of (-)-propranolol (1 microM) to block beta 1- and beta 2-adrenoceptors. Two distinct populations of binding sites remained, one evenly distributed over the muscle bundles and the other localized in discrete patches. Evenly distributed binding was highest in the soleus muscle and inhibited by (+/-)-, (-)- and (+)-alprenolol (20 microM), tertatolol (1 microM), BRL 37344 (2-20 microM), (-)-isoprenaline (100 microM), phentolamine (10 microM) and haloperidol (250 microM) but not ICI 118,551 (70 nM), CGP 20712A (100 nM), (+)-isoprenaline (100 microM), pindolol (2 microM), cimaterol (100 microM) or serotonin (10 microM). Stereoselectivity for the optical isomers of alprenolol was displayed in the soleus muscle only. Highly localized binding was inhibited by serotonin (10 microM), (-)- and (+)-isoprenaline (100 microM) and phentolamine (10 microM).

Animals↗
PubMed1991

Haemangiopericytoma--Queensland Radium Institute experience and a review of the literature.

We report the presenting clinical characteristics, management, relapse patterns and survival of 17 patients with haemangiopericytoma treated at the Queensland Radium Institute, Australia from 1962 to 1989. Twelve patients were referred at the time of first diagnosis and were treated with curative intent. Three patients were treated with palliative intent when referred following initial diagnosis, and the remaining two patients were referred at the time of relapse. Disease was metastatic at presentation in 4 patients. Radiotherapy was used as a component of primary treatment of disease in 11 patients, in both patients referred for management of local relapse of haemangiopericytoma, and for palliation of metastatic disease developing in 3 patients. One patient received chemotherapy as part of initial treatment. Nine patients have died with survival from first treatment ranging from 3 to 139 months. All 8 surviving patients remain free of disease at 6 to 94 months from first treatment.

Adolescent↗
PubMed1991

Testicular lymphoma--the need for a new approach.

Thirteen cases of malignant lymphoma of the testis were referred to the Queensland Radium Institute between 1975 and 1989. The age varied from 43 years to 84 years and the histology was intermediate to high grade in all cases. Seven patients had Stage I/II and 6 had Stage III/IV. The 4 year survival was only 16%. Half of the relapses were systemic, 1 was in the para-aortic nodes (unirradiated) and 2 were in the opposite testicle. Adjuvant radiotherapy to para-aortic nodes and mild chemotherapy have produced disappointing results. A new approach using aggressive combination chemotherapy and adjuvant scrotal irradiation is proposed for early stage disease.

Adult↗
PubMed1990

The primary effect of the Ity locus is on the rate of growth of Salmonella typhimurium that are relatively protected from killing.

The Ity locus affects the net increase in numbers of Salmonella typhimurium in the liver and spleen of infected mice. There has been controversy, however, about whether the effects of this locus are due to differential killing of S. typhimurium or differential growth rates of S. typhimurium in mice. Our studies using S. typhimurium aroA mutants, which do not grow in vivo, demonstrate that growth of the infecting salmonella is necessary for the observation of the Ity phenotype. To examine the effects of the Ity locus on the growth and killing of fully virulent salmonella, we infected Ity-congenic mice i.v. with stationary phase S. typhimurium containing a single copy of the plasmid pHSG422. This plasmid exhibits defective replication at body temperature and is diluted out during salmonella growth in vivo. Thus, the frequency of plasmid-containing salmonella recovered from mice provides a measure of salmonella cell divisions in vivo. Inasmuch as the numbers of plasmid-containing salmonella are only slightly affected by bacterial division, any decline in the numbers of plasmid-containing salmonella is an unbiased measure of killing. By infecting mice with these plasmid-containing salmonella we observed that: 1) during the first four h post infection (during blood clearance of injected salmonella) there is about 3-fold more killing of salmonella in Ityr mice than in Itys mice; 2) from 4 to 44 h postinfection (after blood clearance is completed) there is little if any additional killing in either Itys or Ityr mice; and 3) during the first 48 h postinfection there is about 18-fold more growth of salmonella in Itys mice than in Ityr mice. Thus, the major effect of the Ity locus on resistance to salmonella, is the regulation of growth within a "safe" (relatively nonbactericidal) site in the liver and spleen.

Animals↗
PubMed1990

The secretory pathway is blocked between the trans-Golgi and the plasma membrane during meiotic maturation in Xenopus oocytes.

Protein secretion is blocked in Xenopus oocytes arrested at second meiotic metaphase. In this report, we show that secretion becomes blocked coincident with germinal vesicle breakdown (GVBD). Transport through the metaphase-arrested oocyte's secretory pathway continues unimpeded until proteins reach the trans-Golgi. These conclusions are drawn from experiments using exogenous prolactin and vesicular stomatitis virus G protein (VSV G) encoded by SP6 transcripts and endogenous glycosaminoglycan (GAG) chains initiated on beta-D-4-methylumbelliferyl-xyloside. From the initiation of maturation with progesterone until GVBD, secretion of prolactin synthesized before the start of maturation is comparable to secretion in immature oocytes, but after GVBD secretion of prolactin declines approximately 63% in the first hour. Not all steps in the secretory pathway are blocked when oocytes mature. Since VSV G protein acquires resistance to endo H digestion with equal efficiency in immature oocytes (arrested in first meiotic prophase) and matured oocytes (arrested in second meiotic metaphase), we conclude that transport of this protein from the ER to the Golgi is not inhibited at meiotic metaphase. Using [35S]sulfate to label xyloside-initiated GAG chains we find that transport of GAG chains from the trans-Golgi to the cell surface is 15-fold lower in matured oocytes than in immature oocytes. Examination of the size of GAG chains by SDS-PAGE and HPLC indicates that matured oocytes produce GAG chains significantly larger than GAG chains from immature oocytes. This increase in size suggests that GAG chains from matured oocytes have a longer residence time in the trans-Golgi than GAG chains from immature oocytes. Hence, part of the block to secretion in metaphase-arrested oocytes could be an inhibition of vesicle budding from the trans-Golgi.

Animals↗
PubMed1990

Psychosocial assessment of the high utilizer of occupational health services.

A small group of persons in ambulatory care settings report multiple symptoms and recurrent distress and utilize a high percentage of resources. Often these high utilizers are requesting help with a psychosocial problem through their symptoms. The psychosocial reason for high utilization of services may be a major psychiatric problem such as a somatization disorder or a depression/anxiety disorder. Most often, however, the person is seeking help with family or work stresses or is in need of information and/or reassurance. A careful assessment by the occupational health nurse can lead to a determination of an unmet psychosocial need. Direct help with this problem can break the cycle of multiple symptoms, distress, and utilization.

Ambulatory Care↗
PubMed1989

Properties of the interaction between phosphofructokinase and actin.

The interaction of rabbit skeletal muscle phosphofructokinase (PFK) with actin is characterized in terms of the binding of PFK to actin in the presence and absence of tropomyosin and troponin, the effect of PFK on actin polymerization, and the involvement of adenylates in the binding of PFK to actin. The thin filament proteins, tropomyosin and troponin, are associated with skeletal muscle actin and reduce the binding of PFK to actin, thus influencing the probable distribution of PFK in skeletal muscle. The binding of PFK to actin is inhibited by ATP and ADP but not by fructose 6-phosphate or fructose 2,6-bisphosphate. This specific inhibition, plus evidence from fluorescence quenching and photoaffinity labeling, suggests that actin binds at the adenosine activation sites of PFK. Light scattering measurements used to monitor actin polymerization indicate that PFK dramatically increases the level of light scattering produced by the polymerization of actin, indicative of a superaggregate of PFK and actin. PFK inhibits the polymerization of actin when polymerization is induced by low concentrations of added salts. Although PFK binds to actin with high affinity, it seems to have little effect on the high shear viscosity of actin filaments.

Actins↗
PubMed1988

The salvage of recurrent endometrial carcinoma in the vagina and pelvis.

A retrospective analysis was performed on 93 patients who developed recurrent endometrial carcinoma in the pelvis, vaginal vault, and lower 1/3 vagina. There were 12 lower 1/3 vaginal recurrences, 24 vault recurrences and 57 pelvic recurrences from the 1005 patients treated between 1960 and 1976. Median time to recurrence was 30 months. Twenty-six patients had distant metastases also present at the time of recurrence in the sites mentioned above. Thirty-three percent of lower 1/3 vaginal recurrences, 12.5% of vault recurrences, and 5.3% of pelvic recurrences were salvaged with further treatment. The 10-year actuarial survival rates of isolated lower 1/3 vaginal, vaginal vault, and pelvic recurrences were 50%, 45%, and 24% respectively.

Adenocarcinoma↗