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Biomedical subjects

M Carter

Publications and source records attributed to M Carter.

At least 37 records · Page 2Linked to original sources
PubMed1994

Fragile X induction systems in CVS cultures: effect on cytogenetic, PCR, and genomic Southern Blot DNA analyses of the FMR-1 gene.

Low fragile X frequencies have been commonly observed in chorionic villus sample (CVS) cultures, compared to subsequent analysis in whole blood or products of conception (POC). To investigate possible mechanisms for this effect, CVS cultures from a previously identified fragile X positive male, were restudied and compared to subsequent POC cultures from lung, muscle, skin, and thymus. Cultures were exposed, for the last 24 hours before harvesting, to FUdR, excess thymidine, and a combination of both. For CVS, only those cultures that were exposed to a combination of FUdR and excess thymidine showed positive cytogenetic findings (1/90 or 1.1%), agreeing with our original positive cytogenetic results (2/86 or 2.3%) for cultures exposed to excess thymidine. Fragile X frequencies in the POC tissues from this fetus increased to an average of 14%. PCR analyses showed full mutations (> 200 CGG repeats) in uninduced CVS cultures but induced cultures exhibited apparently smaller sizes in the range of 120-180 repeats. The results showed variability. In one instance, the banding pattern from one of the uninduced cultures was similar to the results where cultures were exposed to a double induction system. When PCR analyses were conducted on induced POC cultures, full mutations were observed in virtually all samples. Southern blot genomic analysis using probe StB12.3 showed an unmethylated full mutation in CVS cultures. Southern blot patterns from cultures of muscle revealed size variations of DNA bands in the premutation range representing unmethylated DNA as well as methylated full mutations. Finally, variations were also observed in lung and skin cultures, compared to CVS and muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Blotting, Southern↗
PubMed1994

Chronic adenosine A1 receptor agonist and antagonist: effect on receptor density and N-methyl-D-aspartate induced seizures in mice.

The effect of chronic administration of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and the adenosine A1 antagonist 8-cyclopentyl-1,3-dipropylxanthine (CPX) on N-methyl-D-aspartate (NMDA)-evoked seizures was studied in C57BL/6 mice (20/group). Animals were injected i.p. for 9 days with either 1.0 mg/kg CPA or 1.0 mg/kg CPX followed by 2 injection-free days (the washout period) and subsequent administration of a single dose of 60 mg/kg NMDA. As in our previous study, this dose of NMDA caused clonic/tonic seizures resulting in high (60%) mortality within 3 h after injection of the drug. Despite insignificant changes in seizure latency, chronic pretreatment with CPA increased the incidence of clonic/tonic episodes and end-point mortality. Conversely; chronic exposure to CPX completely eliminated clonic/tonic episodes, significantly increased average survival time, and reduced end-point mortality (P < 0.05). The results indicate that chronic treatment with adenosine A1 receptor antagonist may protect against NMDA-evoked seizures to the same degree as previously observed following a single, acute exposure to CPA. Since the density of adenosine receptor binding sites was unchanged after chronic treatment with either CPX or CPA, it is likely that the mechanism behind the observed protection may rest at the level of second messenger systems coupled to adenosine A1 receptors.

Adenosine↗
PubMed1994

Nap studies underestimate the incidence of gastroesophageal reflux.

Shorter nap (1 and 4 hr) pH studies inaccurately diagnosed gastroesophageal reflux (GER) in a group of infants evaluated for apparent life threatening events (ALTE) and recurrent apnea. Twenty-five infants with a postconceptional age of 42 +/- 8 SD weeks, were evaluated by 12-hr polysomnography (PSG). Prior to the start of the 12-hr study, a 1-hr Tuttle Test was performed. By means of the 12-hr study 11 infants were diagnosed as having GER while the Tuttle Test incorrectly diagnosed 6 infants, 5 as having no GER and 1 as having GER when no GER was present (P < 0.05). No differences in the amount of periodic breathing (PB) or apnea density (AD) were found between the two studies. In addition, the first 4 hr of the 12-hr PSG segment following the first feeding was evaluated separately. In the 4-hr segment, two of the infants were incorrectly diagnosed as not having GER. In this study, nap studies failed to diagnose all of the infants with GER. Therefore, we conclude that an infant cannot be accurately diagnosed as not having GER without prolonged pH recording.

Female↗
PubMed1994

Use of recombinant virus to assess human cytomegalovirus early and late promoters in the context of the viral genome.

We have developed a system to study human cytomegalovirus (HCMV) cis-acting promoter elements within the context of the viral genome. A recombinant HCMV (RV134) containing a marker gene (beta-glucuronidase) was used to insert HCMV promoter-chloramphenicol acetyltransferase gene constructs into the viral genome between open reading frames US9 and US10. Using this system, we have studied the promoters for the early DNA polymerase gene (UL54), the early-late lower matrix phosphoprotein gene (pp65, UL83), and the true late 28-kDa structural phosphoprotein gene (pp28, UL99). Transient-expression assays demonstrated that the pp65 and pp28 promoters are activated earlier and to higher levels than typically observed with the endogenous gene. In contrast, insertion of these promoters into the viral genome resulted in kinetics which mimicked that of the endogenous genes. In addition, we have also tested a variant of the pp28 promoter (d24/26CAT) which is deleted from -609 to -41. This promoter behaved similarly to the wild-type pp28 promoter, indicating that sequences from -40 to +106 are sufficient for conferring true late kinetics. Taken together, these data demonstrate that the viral genome affords a level of regulation on HCMV gene expression that has been previously unrealized. Therefore, these experiments provide a model system for the analysis of cis-acting promoter regulatory elements in the context of the viral genome.

Blotting, Southern↗
PubMed1993

Effects of N6-cyclopentyl adenosine and 8-cyclopentyl-1,3-dipropylxanthine on N-methyl-D-aspartate induced seizures in mice.

The effect of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and antagonist 8-cyclopentyl-1,3-dipropylxanthine (CPX) on N-methyl-D-aspartate (NMDA)-evoked seizures was studied in C57BL/6 mice (20/group). Animals were injected i.p. either with CPA (0.5, 1, 2 mg/kg) or CPX (1, 2 mg/kg) 15 min prior to administration of NMDA (30, 60, 125 mg/kg). Administration of NMDA alone resulted in a complete locomotor arrest at 30 mg/kg, while clonic/tonic seizures and progressively increasing mortality were seen at higher doses. Prior administration of CPA resulted either in a delay of seizure onset and unchanged mortality (0.5 mg/kg CPA, 60 mg/kg NMDA) or in elimination of tonic episodes and a significant reduction in postictal mortality (1, 2 mg/kg CPA; 60, 125 mg/kg NMDA). Pretreatment with CPX at either 1 or 2 mg/kg eliminated locomotor depression in animals injected with NMDA at 30 mg/kg. At 60 mg/kg NMDA, the effect of CPX administration resulted in mortality equivalent to that seen with 125 mg/kg NMDA administered alone. The results indicate that A1 receptor agonists may protect against NMDA-evoked seizures and that the adenosine A1 receptor may be directly involved in these actions.

Adenosine↗
PubMed1993

Typing of feline calicivirus isolates from different clinical groups by virus neutralisation tests.

One hundred and thirteen isolates of feline calicivirus originating from seven different clinical groups were typed by virus neutralisation tests using eight different cat antisera. The clinical groups comprised 'healthy' cats, cases of acute oral/respiratory disease, chronic stomatitis, acute febrile lameness syndrome, vaccine reactions (clinical disease seen within 21 days of vaccination) and vaccine breakdowns (clinical disease seen more than 21 days after but within one year of vaccination). Isolates from the vaccine reaction cases were grouped into those associated with acute oral/respiratory disease alone and those associated with the lameness syndrome, and the latter group was further subdivided according to the vaccine used. Two groups appeared significantly different from others with some of the antisera. Thus the lameness vaccine reaction isolates associated with vaccine B were significantly different from the isolates from all the other clinical groups, including other lameness isolates, with a number of the antisera. In addition, the chronic stomatitis isolates were significantly different from those from the 'healthy' and the acute oral/respiratory disease groups with one or two of the antisera. Eighty-five to 88 per cent of the isolates were neutralised by antisera raised against F9 or F9-like vaccine strains at a dilution of 1 in 2. Twenty antibody units of such antisera neutralised 42 to 80 per cent of the isolates. A bivalent antiserum raised against a vaccine F9 strain and field strain LS015 neutralised 96 per cent of the isolates at a dilution of 1 in 2, and 20 antibody units neutralised 68 per cent of isolates. Antisera to field strain F65 neutralised all the remaining isolates at a dilution of 1 in 2 and 44 per cent of the remaining isolates at a dilution of 20 antibody units. Therefore, strains LS015 and F65 may be of use in the production of a polyvalent feline calicivirus vaccine, together with the widely used strain F9.

Animals↗
PubMed1993

Expression of Drosophila Rrp1 protein in Escherichia coli. Enzymatic and physical characterization of the intact protein and a carboxyl-terminally deleted exonuclease-deficient mutant.

Drosophila Rrp1 protein purified from embryos has four tightly associated enzymatic activities: DNA strand transfer, single-strand DNA renaturation, 3'-exonuclease, and apurinic endonuclease. Copurifying with these activities is a single polypeptide that has an apparent M(r) of 105,000 when estimated by SDS-polyacrylamide gel electrophoresis. To determine if this polypeptide is sufficient for these activities, it has been overexpressed in Escherichia coli. In crude extracts of E. coli cells, an ATP-independent Mg(2+)-dependent strand transfer activity is observed upon activation of the promoter that drives expression of Rrp1. Rrp1 protein purified from induced E. coli cells has electrophoretic, chromatographic, and enzymatic properties similar to those of Drosophila Rrp1 protein. The carboxyl-terminal region of Rrp1 (amino acids 428-679) is homologous to E. coli exonuclease III. Rrp1 deleted for this region cannot carry out DNA strand transfer, but can renature complementary single-strand DNA. The strand transfer activity of this truncated protein can be restored if DNA 3'-exonuclease is provided in trans by pretreating the double-strand DNA substrate with E. coli exonuclease III. This demonstrates a likely role of the exonuclease in the in vitro DNA strand transfer reaction carried out by Rrp1 protein. Such a role is also suggested by an analysis of the polarity of the strand transfer reaction.

Animals↗
PubMed1993

Laser-assisted enterocystoplasty in rats.

The employment of laser welds to anastomose bowel to bladder in urological surgery has never been described. Using rats, we compared laser-assisted enterocystoplasty (LAE) with conventional sutured enterocystoplasty (CSE). A "patch" ileocystoplasty was performed using distal ileum. Operative time, intraluminal bursting pressure and histologic changes were evaluated. Operative time was 38% less in the LAE (p < 0.001). No statistically significant differences in bursting pressure between LAE and CSE groups was demonstrated (p = 0.654) in rats sacrificed 2 weeks postoperatively. Histologic findings in the laser-assisted enterocystoplasties included early loose granulation tissue and later organization of the granulation tissue with significant collagen deposition. In our preliminary study, laser welding of bowel within the urinary stream was safe, efficacious and rapid and resulted in a mechanically comparable surgical outcome.

Anastomosis, Surgical↗
PubMed1993

Monoclonal antibodies of three different immunoglobulin G isotypes produced by immunization with a synthetic peptide or native protein protect mice against challenge with Plasmodium yoelii sporozoites.

Passive transfer of monoclonal antibodies (MAbs) against malaria circumsporozoite (CS) proteins protects animals against malaria. Active immunization with synthetic or recombinant peptides induces a level of polyclonal antibodies to sporozoites comparable to those found after passive immunization but does not provide comparable protection. In the Plasmodium yoelii system, synthetic or recombinant peptide-induced antibodies have never been shown to protect. The current studies were designed to determine whether immunogen structure (native protein versus synthetic peptide) or immunoglobulin G (IgG) subclass of antibodies was responsible for the absolute differences between protective, passively transferred MAbs and nonprotective, actively induced polyclonal antibodies. In this study we produced two MAbs, QGP-S1 (IgG1) and QGP-S2 (IgG2b), by immunization with a synthetic peptide based on the P. yoelii CS major repeat, (QGPGAP)4, conjugated to keyhole limpet hemocyanin. These MAbs were compared tp NYS1 (IgG3), an anti-CS protein MAb previously produced by immunization with irradiated P. yoelii sporozoites, which recognizes (QGP GAP)2. QGP-S1 and QGP-S2 passively transferred protection. However, when compared with NYS1, there was a hierarchy of protection, NYS1 > QGP-S1 > QGP-S2. There was no correlation between antibody level at challenge as determined by immunofluorescent antibody test against sporozoites or enzyme-linked immunosorbent assay against (QGPGAP)2 or apparent antibody avidity for (QGPGAP)2 by sodium thiocyanate elution assay. The data demonstrate that a synthetic peptide can induce protective antibodies and that a specific antibody subclass is not required for protection. Work to determine whether antibody affinity or fine specificity can explain the hierarchy of protection among the MAbs is under way.

Amino Acid Sequence↗
PubMed1993

T cell receptor-beta mRNA splicing: regulation of unusual splicing intermediates.

The expression of functional T cell receptor-beta (TCR-beta) transcripts requires the activation of programmed DNA rearrangement events. It is not clear whether other mechanisms dictate TCR-beta mRNA levels during thymic ontogeny. We examined the potential role of RNA splicing as a regulatory mechanism. As a model system, we used an immature T cell clone, SL12.4, that transcribes a fully rearranged TCR-beta gene but essentially lacks mature 1.3-kb TCR-beta transcripts in the cytoplasm. Abundant TCR-beta splicing intermediates accumulate in the nucleus of this cell clone. These splicing intermediates result from inefficient or inhibited excision of four of the five TCR-beta introns; the only intron that is efficiently spliced is the most 5' intron, IVSL. The focal point for the regulation appears to be IVS1C beta 1 and IVS2C beta 1, since unusual splicing intermediates that have cleaved the 5' splice site but not the 3' splice site of these two introns accumulate in vivo. The block in 3' splice site cleavage is of interest since sequence analysis reveals that these two introns possess canonical splice sites. A repressional mechanism involving a labile repressor protein may be responsible for the inhibition of RNA splicing since treatment of SL12.4 cells with the protein synthesis inhibitor cycloheximide reversibly induces a rapid and dramatic accumulation of fully spliced TCR-beta transcripts in the cytoplasm, concomitant with a decline in TCR-beta pre-mRNAs in the nucleus. This inducible system may be useful for future studies analyzing the underlying molecular mechanisms that regulate RNA splicing.

Animals↗
PubMed1993

Cancer prevention and early detection: nursing students' knowledge, attitudes, personal practices, and teaching.

This study evaluated the impact of an educational workshop on nursing students' knowledge, attitudes, and personal practices regarding cancer prevention and early detection (CP&ED), as well as the effect that it had on their teaching of CP&ED recommendations. Four one-day workshops--which included lectures, small group discussions, and practice of early detection skills--were held in three cities in Minnesota. Students from baccalaureate, associate-degree, and practical nursing programs participated (N = 220). Preworkshop, postworkshop, and six-month follow-up surveys were used to evaluate the knowledge, attitudes, and self-practice of the participants, as well as their teaching of clients, family, friends, and peers. Data were analyzed with matched paired t-tests, chi-square, correlation, and analysis of variance. The postworkshop and six-month follow-up surveys showed improvement in the students' knowledge and attitudes; however, the only self-practice behaviors that changed within six months of the workshop were breast/testicular self-examinations. The results also showed that the students felt more confident and subsequently taught more clients, family, friends, and peers about the CP&ED recommendations. These findings indicate that educating students early in their careers may increase the number of people practicing CP&ED recommendations.

Adult↗
PubMed1992

The identification of a domain in Escherichia coli elongation factor Tu that interacts with elongation factor Ts.

A method has been developed to search for the elongation factor Tu (EF-Tu) domain(s) that interact with elongation factor Ts (EF-Ts). This method is based on the suppression of Escherichia coli EF-Tu-dominant negative mutation K136E, a mutation that exerts its effect by sequestering EF-Ts. We have identified nine single-amino acid- substituted suppression mutations in the region 146-199 of EF-Tu. These mutations are R154C, P168L, A174V, K176E, D181G, E190K, D196G, S197F, and I199V. All suppression mutations but one (R154C) significantly affect EF-Tu's ability to interact with EF-Ts under equilibrium conditions. Moreover, with the exception of mutation A174V, the GDP affinity of EF-Tu appears to be relatively unaffected by these mutations. These results suggest that the domain of residues 154 to 199 on EF-Tu is involved in interacting with EF-Ts. These suppression mutations are also capable of suppressing dominant negative mutants N135D and N135I to various degrees. This suggests that dominant negative mutants N135D and N135I are likely to have the same molecular basis as the K136E mutation. The method we have developed in this study is versatile and can be readily adapted to map other regions of EF-Tu. A model of EF-Ts-catalyzed guanine-nucleotide exchange is discussed.

Amino Acid Sequence↗
PubMed1992

A spliced intron accumulates as a lariat in the nucleus of T cells.

The vast majority of mammalian genes are interrupted by non-coding segments of DNA termed introns. Introns are spliced out of RNA transcripts as lariat structures, and then are typically debranched and rapidly degraded. Here, we described an unusual spliced intron from the constant region of the T cell receptor-beta (TCR-beta) locus that is relatively stable in mammalian cells. This intron, IVS1C beta 1, accumulates as a set of lariat RNA structures with different length tails in the nucleus of T cells. The accumulation of this spliced intron is developmentally regulated during murine thymocyte ontogeny. The property of stability appears to be evolutionarily conserved since the human version of this intron also accumulates in T cells. The stability is selective since other spliced TCR-beta introns do not detectably accumulate in T cells. The unusual stability of this intron does not depend on T cell specific factors since non-T cells transfected with TCR-beta gene constructs also accumulate spliced IVS1C beta 1. The discovery of a mammalian intron that accumulates as a lariat in vivo provides an opportunity to elucidate mechanisms that regulate intron debranching, stability, and nuclear localization.

Animals↗
PubMed1992

Manipulation of phototransductive membrane turnover by crab photoreceptors in vitro: effects of two protein kinase activators, SC-9 and phorbol ester in the presence of a protein phosphatase inhibitor, okadaic acid.

1. Retinae of crabs, Leptograpsus variegatus, held on a 12:12 h light-dark cycle were prepared for culture in vitro shortly before light-off. After an hour in darkness to permit the assembly of "night" rhabdoms, retinae were exposed to various combinations of drugs: 1 microM okadaic acid (OKA); 60 microM SC-9; 10 microM phorbol, 12,13-diacetate (PDA). 2. The effects of the specific protein phosphatase inhibitor, OKA, are confirmed as light-dependent. Rhabdom sizes were not compromised by OKA, nor by either of the two protein kinase activators, SC-9 or PDA when each was deployed alone in darkness. 3. In combination with OKA, PDA induced demolition of rhabdoms by abnormal macropinocytosis of microvillar membranes. 4. Combined with OKA, SC-9 induced a transient reduction of rhabdoms, followed by overgrowth to abnormal sizes. Overgrowth was blocked by the transcription inhibitor actinomycin D. 5. Disparate consequences of combining OKA with SC-9 or PDA imply that more than one protein kinase C may be involved.

Animals↗
PubMed1992

Sonographic characteristics of the urethrovesical anastomosis in the early post-radical prostatectomy patient.

It is possible that the advent of more aggressive surgical approaches to carcinoma of the prostate, including neoadjuvant and adjuvant therapy, will lead to a higher incidence of pelvic recurrence rates in coming years. A method of sequentially monitoring the region of the urethrovesical anastomosis for early recurrence that is more accurate than digital rectal examination is required. Transrectal ultrasound is an established technique for the preoperative assessment of prostate cancer. It has also been used postoperatively to guide a biopsy needle into palpably suspicious areas at the urethrovesical junction or for random biopsies in patients with elevated prostate specific antigen levels. However, the sonographic anatomy of the postoperative urethrovesical junction has not previously been described. In this prospective study we analyze the transrectal sonographic characteristics of the neoanatomy in 30 patients, all within 3 months following surgery for clinically intracapsular disease. We describe features of the neoanatomy, such as anterior tissue nodules and anastomotic rings. Because of distinct variations in the neoanatomy of different patients we recommend early postoperative transrectal biplanar sonography to establish a baseline image for each individual case. This would be useful for later comparison and may prevent a false positive scan on subsequent followup studies.

Adenocarcinoma↗
PubMed1992

A method of predicting adult height and obesity in long-term survivors of childhood acute lymphoblastic leukemia.

PURPOSE: Short stature and obesity have been reported among long-term survivors of childhood acute lymphocytic leukemia (ALL). We examined factors that contribute to these adverse sequelae. PATIENTS AND METHODS: Serial height and weight measurements were analyzed for 91 long-term survivors who were treated for ALL between 1967 and 1975 at a single institution. These patients were all younger than 12 years at diagnosis, were in continuous complete remission, had reached final height, and had height and weight measurements within 1 year of age 18 years. They had received craniospinal (n = 33) or cranial irradiation (n = 58) to total doses of 24 Gy as CNS prophylaxis. Standard deviation scores (SDS) were used to reflect the deviation of height and weight measurements from population means, and the body mass index (BMI; weight divided by height squared) was used in assessing obesity at age 18 years. RESULTS: Short stature (less than fifth percentile) was seen in 41 patients (45%), and obesity (BMI greater than or equal to 24 kg/m2) in 35 (38%). Regression formulae were developed that explain 65% and 62% of the variability in patient height and BMI, respectively. CONCLUSIONS: Risk factors were identified for abnormally short stature, which was defined to be a decrease of 1.5 SDS in height from diagnosis to age 18 years. These factors include younger age and above-average height for age at diagnosis (height SDS greater than 0), craniospinal irradiation, and greater decrease in height SDS during antileukemic therapy. Risk factors for obesity at age 18 years include weight SDS greater than 0 and greater than height SDS at 1 year after the end of chemotherapy.

Adolescent↗
PubMed1992

Long-term survivors of leukemia treated in infancy: factors associated with neuropsychologic status.

PURPOSE: Because of concerns about late toxicities of treatment among infants diagnosed with acute lymphoblastic leukemia (ALL), and especially the effects of cranial radiation therapy (CRT), we compared the functional and neuropsychologic status of 26 long-term survivors of ALL who were diagnosed in the first 24 months of life versus 26 children who were treated previously for Wilms' tumor. PATIENTS AND METHODS: Of the children with ALL, CNS prophylaxis included no CRT in six, 18 Gy CRT in five, 20 Gy CRT in seven, and 24 Gy CRT in five. Three additional children experienced CNS relapse and received total CRT doses of 24, 40, and 44 Gy. All children received neuropsychologic testing; children with ALL also participated in diagnostic imaging studies. RESULTS: As a group, the children who were treated for ALL did not differ significantly from those who were treated for Wilms' tumor on objective measures of global functional status. However, children treated for ALL had a significantly lower mean intelligence quotient (IQ) (87 v 96), poorer performance on four of six measures of visual and auditory memory, lower achievement with regard to arithmetic skills, and a greater frequency of special educational intervention than those who were treated for Wilms' tumor. IQ and auditory memory performance in the ALL group was correlated inversely with time since the completion of therapy and total CRT dose. CONCLUSIONS: These results reinforce the contemporary trend of prophylactic CRT omission in very young children except for those who are at risk for CNS relapse. For infants and very young children who require CRT, evidence is presented that supports the approach for the delay of CRT until the child is older.

Adolescent↗