Biomedical subjects

J R Scott

Publications and source records attributed to J R Scott.

At least 163 records · Page 9Linked to original sources

PubMed1990

Developing an artificial fallopian tube: successful in vitro trials in mice.

This report describes the design and testing of an artificial fallopian tube for the treatment of tubal infertility. Within the device, mouse eggs incubated with sperm were fertilized and a microinfusion pump was used to transport the fertilized ova through the tube. Normal offspring resulted from transfer of the developing embryos into pseudopregnant recipients. These results provide encouraging evidence that an artificial fallopian tube warrants further investigation as a potential alternative to in vitro fertilization.

Animals↗

PubMed1990

Weight loss, dietary carbohydrate modifications, and high intensity, physical performance.

Well trained subjects (N = 12) were studied before and after losing approximately 6% of body weight to determine whether physical performance could be maintained while consuming a hypocaloric, high percentage carbohydrate diet. During a 4-d period of weight loss, subjects were randomly assigned to a high carbohydrate (HC) or low carbohydrate (LC) diet. A crossover design was used; subjects were measured before (PRE) and after (POST) weight loss on both diets for a 6-min bout of high intensity arm cranking, weight, skinfold thickness, and profile of mood states (POMS). Hemoglobin, hematocrit, and glycerol concentrations were analyzed for resting blood samples, while lactate, pH, and base excess were analyzed for blood samples drawn at rest and 1, 3, and 5 min after arm cranking. A three-way ANOVA of sprint work revealed a weight loss effect, a diet by weight loss interaction, and an order by diet by weight loss interaction (P less than 0.05). Total sprint work (mean +/- SE) PRE and POST HC was 37.7 +/- 2.1 kJ and 37.4 +/- 2.2 kJ, respectively. Sprint work was higher for PRE LC vs POST LC, with mean values of 37.4 +/- 2.1 kJ and 34.4 +/- 2.2 kJ, respectively. Post-arm cranking lactate was significantly higher PRE compared to POST for both HC and LC. Post-exercise blood pH was lower (P less than 0.05) at PRE vs POST, with no diet effect. Regardless of the diet, POMS variables tension, depression, anger, fatigue, and confusion were significantly elevated from PRE to POST; vigor was significantly lower.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Excision and insertion of the conjugative transposon Tn916 involves a novel recombination mechanism.

The covalently closed circular form of the conjugative transposon Tn916, which acts as an intermediate in transposition, is produced by a novel type of recombination. Excision of the element pairs noncomplementary base pairs, which flank the transposon in a heteroduplex, at the joint of a circular form. By a reversal of the excision process, the base pairs from the heteroduplex are inserted into the next target. We present a detailed molecular model for the movement of conjugative transposons that involves the initial formation of staggered nicks in the "coupling regions" that flank the inserted element. The different products of excision and insertion of Tn916 can be explained by this model.

Base Composition↗

PubMed1989

Enucleation after intraocular scrapie injection delays the spread of infection.

After right intraocular infection, mice develop lesions in the contralateral retinal projections long before clinical disease occurs. Enucleation up to 7 days post-infection prevented targeting of lesions to visual projections, and prolonged the incubation period. When enucleation was delayed until at least 14 days post-infection, lesion targeting and incubation periods were similar to unenucleated mice. It was concluded that infectivity took a minimum of 14 days to reach the brain via the optic nerve.

Animals↗

PubMed1989

31P NMR studies of the metabolic status of pig hearts preserved for transplantation.

31P NMR spectroscopy has been used to evaluate the metabolic status of cardioplegically arrested pig hearts. Hearts were stored with Plegisol for up to 12 hours at either 5 degrees C or 12 degrees C. Results indicated that the ATP content of hearts could be maintained (greater than 70% of initial values) for up to 5 hours in the ischemic storage state. The ATP loss was greater at 12 degrees C. PCr was lost exponentially under the same conditions. Functional testing by reperfusing the stored hearts in vitro indicated a good correlation between the ATP content and survivability of the preparations. Twenty-four hour preservation of pig hearts using slow perfusion with a modified cardioplegic solution (Wicomb) allowed for preservation of both PCr and ATP, in all cases, reperfusion of hearts revealed a loss of NMR- visible ATP and PCr.

Adenosine Triphosphate↗

PubMed1989

Comparison of maximum aerobic power, maximum anaerobic power, and skinfold thickness of elite and nonelite junior wrestlers.

The purpose of this investigation was to identify physiologic differences between elite high school-age wrestlers and nonelite wrestlers of comparable age, weight, and training experience. Two groups of junior wrestler, elite (n = 18) and nonelite (n = 18) were measured for maximum aerobic power (treadmill run), maximum anaerobic power of the arms and legs (Wingate test), and skinfold thickness. On the average (+/- SE) elite juniors had a VO2max of 52.6 +/- 2.0 ml/kg.min-1, 376 +/- 20 W for arm power, and 540 +/- 25 W for leg power. The nonelite group had a VO2max of 51.5 +/- 1.4 ml/kg.min-1 and 331 +/- 22 W and 467 +/- 29 W for arm and leg power, respectively. Ttests were computed to identify differences between the groups. The results revealed significant differences in four skinfold thicknesses, absolute anaerobic leg power, and relative anaerobic power of arms and legs. It was concluded that relative maximum anaerobic power is distinctly greater in elite high school wrestlers than less successful peers. In light of the results, it may be of benefit for wrestlers of lower caliber to decrease body fat, increase fat-free weight, and increase total body power through training.

Adolescent↗

PubMed1989

A plasmid-encoded regulatory gene, rns, required for expression of the CS1 and CS2 adhesins of enterotoxigenic Escherichia coli.

To be virulent, enterotoxigenic Escherichia coli (ETEC) must produce a toxin and a pilus-like structure that mediates specific attachment to host tissue. Expression of two of these specific adherence structures, CS1 and CS2, requires the presence of a plasmid in an ETEC strain of a particular serotype and biotype. We show here that this plasmid does not contain the structural gene for a pilin protein, as previously believed. Instead we have identified a plasmid-encoded gene called rns that is required for expression of CS1 or CS2 colonization factor antigens and for adhesion. The rns gene, defined by two separately isolated insertion mutations, produces a 26-kDa protein when transcribed and translated in vitro. At the protein level the rns gene product is homologous to AraC, a positive regulator of the arabinose operon of enteric bacteria, and to RhaR and RhaS, which regulate the rhamnose operon of E. coli. The homology of the Rns protein to AraC is localized to regions that are believed to bind to DNA. Moreover, the sequence of one of these homologous regions is consistent with a DNA binding helix-turn-helix motif. The average G + C content of E. coli DNA is 50%; yet the rns gene contains only 28% G + C, suggesting that it was acquired from some other organism.

Adhesins, Escherichia coli↗

PubMed1989

A method for allelic replacement that uses the conjugative transposon Tn916: deletion of the emm6.1 allele in Streptococcus pyogenes JRS4.

The emm6.1 allele of Streptococcus pyogenes JRS4 was deleted by using the conjugative transposon Tn916. The aphA-3 gene, conferring resistance to kanamycin, was cloned between the sequences flanking the structural gene for the type 6 M protein (emm6.1) and inserted into the BstXI site of Tn916 to generate the chimeric transposon Tn916-5K3. Because the BstXI site lies in a nonessential region of Tn916, the chimeric transposon could transfer by conjugation from Bacillus subtilis into JRS4. In some of the transconjugants, Tn916-5K3 replaced the emm6.1 locus of JRS4 by homologous recombination between the cloned emm6.1-flanking regions and the resident chromosome. One recombinant studied in detail, JRS75, was kanamycin resistant and tetracycline sensitive and lacked immunologically detectable M6 protein. Furthermore, by Southern blot analysis, the DNA region encompassing the emm6.1 structural gene was found to have been replaced by aphA-3.

Alleles↗

PubMed1989

The association of antiphospholipid antibodies with severe preeclampsia.

Over a 3-year period, we studied 43 women who presented with severe preeclampsia prior to 34 weeks' gestation. Seven (16%) had significant levels of antiphospholipid antibodies, whereas none of the normotensive controls of similar gestational age had antiphospholipid antibodies (P less than .001). Three of the seven women with antiphospholipid antibodies suffered the following complications during the peripartum period: 1) cerebral infarction and episodes of transient monocular blindness; 2) pulmonary embolism, deep venous thrombosis, and an autoimmune flare in the postpartum period; and 3) transient monocular blindness and amnesia after delivery. Our experience suggests that antiphospholipid antibodies are found in a substantial proportion of cases of early-onset severe preeclampsia and have important clinical implications. We suggest that patients with early-onset severe preeclampsia be screened for antiphospholipid antibodies; if antibodies are detected, these women should be considered for prophylactic anticoagulation therapy.

Autoantibodies↗

PubMed1989

Elevated anti-D titer after the administration of Rh immune globulin. A case report.

An anti-D titer of 1:16 was detected in a woman who had received 300 micrograms of Rh immune globulin as antepartum prophylaxis. It has been generally accepted that antibody titers following the administration of Rh immune globulin are less than 1:2. Although Rh immunization is always a potential cause of a titer greater than 1:4, a conservative approach is warranted in managing the patient with elevated anti-D antibody titers detected following the administration of Rh immune globulin.

Adult↗

PubMed1989

Transport and targeting of scrapie infectivity and pathology in the optic nerve projections following intraocular infection.

The initial development of scrapie lesions can be seen following intraocular infection to be directly related to sequential infection of connecting neuronal relays within the projections of the optic nerve. For example, intraocular infection of VM mice with 22A virus produces lesions in the contralateral dorsal lateral geniculate nucleus (dLGN) and superior colliculus around halfway through the incubation period of about 360 days; the next lesions appear in the visual cortex, presumably as a result of the transport of infection through the geniculo-cortical tract. Infection of the same strain of mouse with 87V virus produces similar lesions in the dLGN slightly later in the incubation period of about 440 days, although cortical lesions are never seen with this agent. Subsequent lesions with both strains of the virus occur symmetrically in sites which are recognised targets with other routes of infection. Differences of this type provide the opportunity to relate levels of infectivity in sets of neurons directly to subsequent pathological changes. If the two murine Sinc genotypes (Sinc controls incubation period length) are compared after intraocular infection with ME7 virus, the timing of the appearance of the first lesions is in proportion to the length of the incubation period; this may provide a means of identifying the action of Sinc at a cellular level. Serial enucleation following infection of the right eye with ME7 virus has shown that infection takes between 7 and 14 days to reach the superior colliculus and initiate infection via this pathway. This slow rate of spread of infectivity suggests that ME7 is carried in an anterograde direction by the slow rate of axonal transport.

Animals↗

PubMed1989

The molecular pathology of scrapie and the biological basis of lesion targeting.

Strains of scrapie virus can only be distinguished from the incubation period and neuropathology of the disease they induce in mice of different Sinc genotypes. There are two main aspects of the neuropathology: a spongiosis or degenerative vacuolation associated with the replication of virus, and cerebral amyloid plaques. The relationship between these two is unclear - they can occupy topographically quite different centres in the CNS and the timing of their occurrence is different. Surprisingly this is also the case using the very precise targeting provided by the intraocular infection route. Here the earliest spongiosis is very localised into the primary and secondary projections from the retina, but plaques, when they occur, occupy quite different sites. The relationship between plaques and spongy degeneration is probably a neuroanatomical one, similar to that suggested between plaques and tangle-bearing neurons in Alzheimer's disease. A third aspect of the pathology is the occurrence of SAF in negative-stained E.M. preparations, formed from the aggregation of a sialoglycoprotein called PrP or SAF-protein. Immunolabelling of plaques with antisera to SAF protein shows as yet that there is no antigenic variation in the protein prepared from different scrapie models with different strains of the virus based on available reagents. Strain variation is only recognised on biological criteria; as yet, there are no independent molecular markers or in vitro tests which can account for the biological variation.

Amyloidosis↗

PubMed1988

Conformational characteristics of the complete sequence of group A streptococcal M6 protein.

M protein is considered a virulence determinant on the streptococcal cell wall by virtue of its ability to allow the organism to resist attack by human neutrophils. The complete DNA sequence of the M6 gene from streptococcal strain D471 has allowed, for the first time, the study of the structural characteristics of the amino acid sequence of an entire M protein molecule. Predictive secondary structural analysis revealed that the majority of this fibrillar molecule exhibits strong alpha-helical potential and that, except for the ends, nonpolar residues in the central region of the molecule exhibit the 7-residue periodicity typical for coiled-coil proteins. Differences in this heptad pattern of nonpolar residues allow this central rod region to be divided into three subdomains which correlate essentially with the repeat regions A, B, and C/D in the M6 protein sequence. Alignment of the N-terminal half of the M6 sequence with PepM5, the N-terminal half of the M5 protein, revealed that 42% of the amino acids were identical. The majority of the identities were "core" nonpolar residues of the heptad periodicity which are necessary for the maintenance of the coiled coil. Thus, conservation of structure in a sequence-variable region of these molecules may be biologically significant. Results suggest that serologically different M proteins may be built according to a basic scheme: an extended central coiled-coil rod domain (which may vary in size among strains) flanked by functional end domains.

Amino Acid Sequence↗

PubMed1988

Intravenous immunoglobulin treatment of pregnant patients with recurrent pregnancy loss caused by antiphospholipid antibodies and Rh immunization.

A patient with antiphospholipid antibodies and nine consecutive fetal deaths and a severely Rh-immunized woman with one previous live birth and seven fetal/neonatal deaths achieved live births after antepartum administration of intravenous immunoglobulin. This agent shows promise as a new treatment for patients with previous repetitive fetal deaths from immunologic causes.

Adult↗

PubMed1988

A single amino acid difference between Rep proteins of P1 and P7 affects plasmid copy number.

P1 and P7 are closely related plasmid prophages which are members of the same incompatibility group. We report the complete DNA sequence of the replication region of P7 and compare it to that of P1. The sequence predicts a single amino acid difference between the RepA proteins of these two plasmids, no differences in methylation sites or regions where dnaA protein is expected to bind, and no difference in the spacing of the major features of the two replicons. A P1 replicon with a mutation in repA, the gene that encodes an essential replication protein, is complemented for replication by providing either the P1 RepA protein (RepA1) or the P7 RepA protein (RepA7) in trans. Furthermore, when either of these proteins is supplied in trans, the plasmid copy number of P1 cop mutants drops to that of P1 cop+. However, when RepA7 is supplied, the copy number of P1 cop and P1 cop+ is higher than that when RepA1 is supplied. This indicates that the single amino acid difference between the two versions of the RepA protein plays an important role in determining the plasmid copy number.

Amino Acids↗

PubMed1988

The gamete and embryo compatibility of various synthetic polymers.

Several popular and well-characterized polymeric materials were evaluated for their biocompatibility toward the cells unique to reproduction. To accomplish these studies, several in vitro tests were developed that evaluated biocompatibility between the polymers and spermatozoa, ova, and embryos. The data indicated significant differences between the materials with respect to their biocompatibility toward sperm motility, the sperm's ability to penetrate zona-free hamster eggs, and the ability of two-cell mouse embryos to divide. Polytetrafluoroethylene (PTFE-Teflon; PTFE, Chemplast Inc., Wayne, NJ), polyethylene glycol (PEG), and polyhydroxyethyl methacrylate (PHEMA) appear to be the most inert of the materials studied. Polyvinyl chloride (PVC; Tygon-Norton, Akron, OH) was found to be the most detrimental material toward gametes and embryos, with gross physiologic and morphologic changes observed in the PVC-exposed cells.

Animals↗

PubMed1988

Genetically discrete populations of Trypanosoma congolense from livestock on the Kenyan coast.

Twenty-seven stocks of Nannomonas trypanosomes isolated from livestock in 1982 on a ranch at Kilifi on the Kenyan coast were characterized by isoenzyme electrophoresis and by the abilities of the parasite's DNA to hybridize to two repetitive sequence DNA probes. All the Kilifi stocks which were examined had isoenzyme patterns which were markedly different from the 75 patterns previously described from 78 stocks of Trypanosoma congolense. On average only 15% of the enzyme bands present in the Kilifi stocks were present in those stocks of T. congolense which had previously been surveyed for isoenzymes. The DNA from all the Kilifi stocks which had been examined for isoenzymes hybridized with only the repetitive sequence probe isolated from a clone of a Kilifi stock. In contrast, the DNA from all 27 Kilifi stocks failed to hybridize with a repetitive sequence probe isolated from a clone from a different stock of T. congolense. Thus, the trypanosomes in all the Kilifi stocks examined were both phenotypically and genotypically discrete. These genetically discrete trypanosomes have also been detected in 2 stocks isolated from livestock from another location on the Kenyan coast. The results show that there is a wide range of genetic heterogeneity within the trypanosomes currently classified as T. congolense. We suggest that the limits of this genetic heterogeneity could represent incipient speciation.

Animals↗

PubMed1988

An intermediate in transposition of the conjugative transposon Tn916.

Using the conjugative transposon Tn916, we have identified a closed covalent circular form produced in vivo that is able to serve as an intermediate in transposition. When a region of a streptococcal chromosome containing Tn916 is cloned in an Escherichia coli plasmid, supercoiled transposon molecules are excised spontaneously. The purified supercoiled forms transform Bacillus subtilis protoplasts by inserting into the chromosome, apparently at random. In B. subtilis, Tn916 retains its ability to promote conjugative transposition, as shown by its transfer to Streptococcus pyogenes.

Bacillus subtilis↗