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Biomedical subjects

S Collins

Publications and source records attributed to S Collins.

At least 145 records · Page 8Linked to original sources
PubMed1995

Rapid analysis of beta-agonists in urine by thermospray tandem mass spectrometry.

A method is described for the analysis of beta-agonists in urine of cattle. The method uses solid-phase extraction (SPE), followed by analysis of the resulting extract by flow injection thermospray tandem mass spectrometry (TSP-MS-MS). Sample preparation is performed using a mixed-bed SPE procedure using a sorbent having both hydrophobic and ionic properties. MS-MS analysis following thermospray ionization, is performed in single-reaction monitoring parent mode. In that way isotope dilution can be used for quantitation of clenbuterol. Data are presented on precision and accuracy for clenbuterol and related compounds. Furthermore, data acquisition was performed in full-scan neutral loss mode to indicate the suitability of flow injection analysis (FIA)-TSP-MS-MS for exploratory analysis. Detection of beta-agonists in this mode is based on the presence of the N-tert.-butyl-beta-ethanolamino moiety and, in that respect, detection of known as well as unknown compounds having this moiety will take place. This feature is exemplified by the analysis of samples containing several compounds.

Adrenergic beta-Agonists↗
PubMed1995

Regulation of the uncoupling protein gene (Ucp) by beta 1, beta 2, and beta 3-adrenergic receptor subtypes in immortalized brown adipose cell lines.

Immortalized brown adipocyte cell lines derived from a mouse hibernoma express all three beta-adrenergic receptor subtypes, including beta 3-adrenergic receptor (AR). In response to norepinephrine, cAMP production by plasma membranes from four clonal cell lines was stimulated to levels comparable with brown adipocytes isolated from interscapular brown adipose tissue (72.8-89.6 versus 97.8 pmol cAMP/min/mg of protein, respectively). All cell lines responded to the highly selective beta 3-adrenergic receptor agonist CL316,243 by stimulating adenylyl cyclase activity (3-10-fold over basal). beta 1-, beta 2-, and beta 3-adrenergic receptor mRNA was detected by Northern blotting and/or reverse transcriptase-polymerase chain reaction. Competition binding assays with the antagonists CGP20712A and 125I-cyanopindolol showed the proportions of beta 1AR and beta 2AR in immortalized cells to be similar to brown adipocytes from tissue (cells: 35% beta 1AR, 65% beta 2AR; brown adipocytes from tissue: beta 1AR 41%, 59% beta 2AR). Expression of brown fat-specific mitochondrial uncoupling protein (Ucp) was stimulated by beta-adrenergic agonists in two of the four cell lines. The ability of individual beta AR subtypes to regulate Ucp expression was examined with combinations of selective beta-adrenergic agonists and antagonists. Expression of Ucp could be induced by any of the beta-adrenergic receptor subtypes. However, the greatest response was obtained by stimulating all three beta-adrenergic receptor subtypes simultaneously (100 microM isoproterenol). Incubation of membranes from cultured cells or brown adipocytes from tissue with CL316,243 at an optimal concentration (5 microM) did not prevent norepinephrine from further stimulating adenylyl cyclase activity, suggesting that the combined activation of beta 1AR/beta 2AR, plus beta 3AR, together produced an additive cAMP response. Multiple forms of adenylyl cyclase were identified in brown and white adipocyte cell lines and tissues. Northern blot analysis detected adenylyl cyclase types 5, 6, and 10. Screening of reverse transcriptase-PCR products by DNA sequencing confirmed the identities of these forms and lower levels of additional isoforms, raising the possibility that beta-adrenergic receptor subtypes in adipocytes couple to distinct adenylyl cyclases. Because these cell lines display functional and phenotypic similarities to interscapular brown adipocytes, they will be a useful model to study the regulation of beta-adrenergic receptor expression and function, and the control of Ucp expression and activity.

Adenylyl Cyclases↗
PubMed1995

Polymerase chain reaction detection of the BCR-ABL fusion transcript after allogeneic marrow transplantation for chronic myeloid leukemia: results and implications in 346 patients.

We studied 346 patients after bone marrow transplantation (BMT) for chronic myeloid leukemia (CML) for the presence of the bcr-abl transcript detected by the polymerase chain reaction (PCR) to understand the frequency and implication of a positive test. A total of 634 samples of BM and/or peripheral blood were obtained for PCR analysis between 3 and 192 months after BMT. A positive PCR test at 3 months post-BMT was not statistically significantly associated with an increased risk of relapse compared with PCR-negative patients. However, a positive PCR assay at 6 months and beyond was highly associated with subsequent relapse. The Kaplan-Meier estimate of relapse for patients testing PCR-positive at 6 to 12 months was 42% versus 3% for PCR-negative patients (P < .0001). The Kaplan-Meier estimate of survival at 4 years for the PCR-positive patients was 74% compared with 83% for the PCR-negative group (P = .002). Multivariable analysis indicated that a PCR-positive result at 6 to 12 months post-BMT, the type of BMT donor (allogeneic matched donor v mismatched or unrelated), and the presence of acute GVHD were independent risk factors for subsequent relapse. The relative risk (RR) for relapse for patients PCR-positive at 6 to 12 months post-BMT was 26.1 (95% confidence interval, 8.9 to 76.1, P < .0001). The outcome of long-term patients (> 36 months post-BMT) who tested PCR-positive was much better, as 15 of 59 (25%) tested positive for bcr-abl, but only one patient relapsed. There was a 91% concordance between PCR tests of simultaneously obtained BM and peripheral blood. These analyses show that the PCR assay of the bcr-abl fusion transcript 6 to 12 months post-BMT is an independent predictor of subsequent relapse which provides an opportunity for early therapeutic intervention.

Adolescent↗
PubMed1995

Phrenic nerve conduction study in normal subjects.

Phrenic nerve conduction studies were performed in 50 phrenic nerves from 25 normal subjects using a technique modified from previously described methods. The normal ranges for latency, amplitude, negative peak area, and duration were established. The latency correlates with age and the amplitude increases with chest circumference. With our method, the amplitude increases and the duration decreases with lung volume. We found good right-left agreement and reproducibility. Therefore, the unaffected side can be used as a reference in unilateral phrenic nerve lesions and previous studies can be used for comparison in serial studies. We recommend that phrenic nerve conduction studies be used routinely to diagnose and monitor patients with respiratory involvement from neuromuscular diseases.

Action Potentials↗
PubMed1995

Volitional control of anticipatory ocular pursuit responses under stabilised image conditions in humans.

Ocular pursuit responses have been examined in humans in three experiments in which the pursuit target image has been fully or partially stabilised on the fovea by feeding a recorded eye movement signal back to drive the target motion. The objective was to establish whether subjects could volitionally control smooth eye movement to reproduce trajectories of target motion in the absence of a concurrent target motion stimulus. In experiment 1 subjects were presented with a target moving with a triangular waveform in the horizontal axis with a frequency of 0.325 Hz and velocities of +/- 10-50 degrees/s. The target was illuminated twice per cycle for pulse durations (PD) of 160-640 ms as it passed through the centre position; otherwise subjects were in darkness. Subjects initially tracked the target motion in a conventional closed-loop mode for four cycles. Prior to the next target presentation the target image was stabilised on the fovea, so that any target motion generated resulted solely from volitional eye movement. Subjects continued to make anticipatory smooth eye movements both to the left and the right with a velocity trajectory similar to that observed in the closed-loop phase. Peak velocity in the stabilised-image mode was highly correlated with that in the prior closed-loop phase, but was slightly less (84% on average). In experiment 2 subjects were presented with a continuously illuminated target that was oscillated sinusoidally at frequencies of 0.2-1.34 Hz and amplitudes of +/- 5-20 degrees. After four cycles of closed-loop stimulation the image was stabilised on the fovea at the time of peak target displacement. Subjects continued to generate an oscillatory smooth eye velocity pattern that mimicked the sinusoidal motion of the previous closed-loop phase for at least three further cycles. The peak eye velocity generated ranged from 57-95% of that in the closed-loop phase at frequencies up to 0.8 Hz but decreased significantly at 1.34 Hz. In experiment 3 subjects were presented with a stabilised display throughout and generated smooth eye movements with peak velocity up to 84 degrees/s in the complete absence of any prior external target motion stimulus, by transferring their attention alternately to left and right of the centre of the display. Eye velocity was found to be dependent on the eccentricity of the centre of attention and the frequency of alternation. When the target was partially stabilised on the retina by feeding back only a proportion (Kf = 0.6-0.9) of the eye movement signal to drive the target, subjects were still able to generate smooth movements at will, even though the display did not move as far or as fast as the eye. Peak eye velocity decreased as Kf decreased, suggesting that there was a continuous competitive interaction between the volitional drive and the visual feedback provided by the relative motion of the display with respect to the retina. These results support the evidence for two separate mechanisms of smooth eye movement control in ocular pursuit: reflex control from retinal velocity error feedback and volitional control from an internal source. Arguments are presented to indicate how smooth pursuit may be controlled by matching a voluntarily initiated estimate of the required smooth movement, normally derived from storage of past re-afferent information, against current visual feedback information. Such a mechanism allows preemptive smooth eye movements to be made that can overcome the inherent delays in the visual feedback pathway.

Conflict, Psychological↗
PubMed1995

Mutation of the p53 gene precedes aneuploid clonal divergence in colorectal carcinoma.

To establish whether p53 mutation precedes or follows clonal divergence in human colorectal carcinomas, 17 tumours were analysed at multiple sites (2-5 each) for single-strand conformation polymorphisms (SSCP) within exons 5-8 of the p53 gene. A previous study had demonstrated subclones of differing DNA ploidy in these tumours, but all showed immunocytochemical evidence for p53 stabilisation, using the monoclonal antibody PAb 1801. Mutations within exons 5-8 of p53 were identified by the presence of an abnormally migrating band in 10 of the 17 carcinomas: five in exon 5, four in exon 7 and one in exon 8. In each of these positive cases, samples from different parts of the carcinoma showed identical gel migration patterns in SSCP analysis. Similarly, the remaining seven tumours were concordant for absence of band shift across all samples of each tumour. Six SSCP-positive cases contained multiple populations differing in DNA ploidy, while four were homogeneously diploid or aneuploid throughout. Very similar proportions were observed in the SSCP-negative cases. In four positive tumours the mutation was confirmed by sequencing or through alteration of nucleotide-specific restriction enzyme cleavage. Identical mutations appeared in every sample from the same tumour. The results provide unequivocal evidence that the same mutant allele of p53 is present throughout each tumour bearing a mutation, regardless of the clonal variation identified by analysis of DNA ploidy. We conclude that in colorectal tumorigenesis mutation of p53 occurs as a single event which precedes and may facilitate the aneuploid clonal divergence of carcinomas.

Alleles↗
PubMed1995

The limit of human adaptation to starvation.

During the height of the 1992-93 famine in Somalia, data were collected from 573 inpatients at the Concern Worldwide Adult Therapeutic Centre in Baidoa, the town at the epicentre of the disaster. These data indicate that a body mass index (BMI, body weight in kilograms divided by height in metres squared) of less than 10 kg m-2 can be compatible with life, so long as specialized care is provided. Such low levels of BMI may be explained, in part, by the high ambient temperature, the tall phenotype of the Somalis, the gradual reduction in food intake and previous exposure to chronic energy deficiency. Famine oedema occurred with the same prevalence in male and female patients, but male patients had more severe oedema and a poorer prognosis at any given degree of severity. Survival from these extremes of emaciation has never before been recorded, and many of the BMI values documented here are below the level of 12, previously thought to mark the limit of human adaptation to starvation.

Adaptation, Physiological↗
PubMed1995

Offending by adults with learning disabilities and the attitudes of staff to offending behaviour: implications for service development.

The aims of this study were: (I) to identify all adults with learning disabilities living in residential homes or attending day services in the Cambridge Health District in contact with the criminal justice system during 1992; (2) to evaluate the responses of services involved; and (3) to investigate the attitudes of staff and the policies of the services to 'offending behaviour'. Details of offences committed and the response of the police, health and social services, and other agencies were obtained by direct interview with the senior staff and through examination of case records. The attitudes of staff to offending behaviour was investigated by the use of a semi-structured questionnaire. Seven (2%) out of 358 adults with learning disabilities were reported to have had contact with the police during 1992. The eight offences allegedly committed by the seven people were two acquisitive offences, two sexual offences, one assault, one wasting of police time, one offence against the Public Order Act and one traffic offence. One offender was cautioned after the Crown Prosecution Service discontinued the case because of lack of evidence, while the other alleged offenders received informal warnings. None of the seven alleged offenders were prosecuted. Three alleged offenders lived in hostel accommodation, yet hostel accommodation only accounts for 7.8% of adults with learning disabilities living in the Cambridge Health District. Because of a lack of operational policies on offending behaviour, there were no existing referral structures for people who might need specialist health service support. Referrals tended to be inconsistent, with a considerable time-lag between offence and referral. Tolerance levels towards offending behaviour were extremely high in the two hostels, 20 group homes and day centres which were included in this study. Theft and criminal damage was hardly ever reported. Thirty establishments were visited during the course of this study. Of these establishments, staff in 12 said they would always report a major assault. In only three would a sexual assault or indecent exposure always be reported if it was to occur. Staff at one residential establishment said they would hesitate to report rape and the staff in another two would consider the circumstances before reporting it to the police.

Adult↗
PubMed1995

Contrasting histochemical features of various mitochondrial syndromes.

A comparative histochemical analysis of the prevalence and cytochrome oxidase staining characteristics of ragged-red fibres in limb skeletal muscles was performed in 19 patients spanning four distinct mitochondrial syndromes: chronic progressive external ophthalmoplegia; myoclonus epilepsy with ragged-red fibres; mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes; and pure limb myopathy. The percentage occurrence of non-ragged red but cytochrome oxidase negative fibres was additionally noted. Ragged-red fibres and cytochrome oxidase-negative fibres were generally more prevalent in the chronic progressive external ophthalmoplegia syndrome than in myoclonus epilepsy ragged-red fibres syndrome or mitochondrial myopathy encephalopathy lactic acidosis and stroke-like episodes syndrome. Isolated cytochrome oxidase-negative fibres were a common finding in each phenotypic syndrome except pure limb myopathy and could involve any of the major fibre types non-specifically. Ragged-red fibres were devoid of cytochrome oxidase activity in chronic progressive external ophthalmoplegia, but commonly displayed activity in the other three syndromes providing a clue to syndromal differentiation on a histochemical basis.

Adolescent↗
PubMed1995

Expression of candidate pro-GnRH processing enzymes in rat hypothalamus and an immortalized hypothalamic neuronal cell line.

Since gonadotropin-releasing hormone (GnRH, also referred to as LHRH) is a major hormone regulating mammalian reproduction, identification of the processing steps involved in the conversion of the pro-LHRH to LHRH is fundamental to our understanding of its physiology. Extracts from immortalized LHRH neurons (GT1) were used to isolate the pro-LHRH intermediate products and to identify the enzymes which may participate in these conversions. The GT1 cells contain and secrete a pro-LHRH species that elutes at approximately 10,000-12,000 molecular weight. The pro-LHRH is metabolized to various N- and C-terminally modified LHRH products and to gonadotropin-releasing hormone-associated peptide (GAP). Analyses of these intermediates suggests that, at least, four different enzymatic steps are involved in pro-LHRH processing. Northern blot analyses reveal that prohormone convertase 2 (PC2), carboxypeptidase E, glutaminyl cyclase, and peptidyl-glycine alpha-amidating monooxygenase are expressed in the GT1 cells and rat hypothalamus. PC2 immunoreactivity is localized to the perikarya and beaded axon-like processes of these cells. SDS-PAGE analyses indicate that PC2 is biosynthesized, processed and secreted by the immortalized LHRH neurons. Our results indicate that the GT1 cell line may serve as a useful model to study the regulation of pro-LHRH processing and that it may also represent an important tool for dissecting the molecular and cellular basis of mammalian reproduction.

Acyltransferases↗
PubMed1995

Incidence of persons with a learning disability detained in police custody. A needs assessment for service development.

The aim of this prospective study was to identify the number of people with a possible learning disability suspected of having committed a criminal offence who were taken into police custody during a defined period of time. Between 18 January 1993 and 18 March 1993 992 people were taken into custody at Parkside Police Station, Cambridge, of whom 251 (25.3%) were screened by the custody officer using a brief questionnaire to ascertain the presence or absence of reading and writing difficulties and to see if they had received extra help at school or if they had attended a special needs school. Information on age, sex, suspected offence, disposal, if a solicitor assisted and incidence of homelessness was gathered from the custody reports.

Adolescent↗
PubMed1995

Age-dependent changes in beta-adrenergic receptor subtypes and adenylyl cyclase activation in adipocytes from Fischer 344 rats.

Epididymal adipocytes were isolated from Fischer 344 rats aged 3, 6, 12, and 24 months, to study the mechanisms responsible for age-dependent diminution in cellular adrenergic responsiveness. Messenger RNA (mRNA) levels for the beta 1-, beta 2-, and beta 3-adrenergic receptors (ARs) were compared across age groups and related to adenylyl cyclase activation by selective receptor agonists in adipocyte plasma membranes and activation of lipolysis in intact cells. mRNA levels for the beta 1-AR decreased by 60% between 3-6 months and remained at this reduced level through 12 and 24 months. A modest increase in beta 2-AR mRNA was noted between 3-12 months, but decreased between 12-24 months to levels seen in the 3-month-old group. mRNA for the beta 3-AR did not change between 3-6 months, but decreased by about 40% between 6-12 months, and by a further 50% between 12-24 months. Lipolytic responsiveness also diminished with age, and regardless of whether beta 3-selective or beta 1/beta 2-selective agonists were used, the maximal release of glycerol was most severely blunted in adipocytes from 24-month-old rats. The age-dependent changes in adenylyl cyclase activation by beta-adrenergic agonists mirrored the observed changes in lipolytic responsiveness with respect to diminished efficacy. These results together with the similar forskolin-stimulated adenylyl cyclase activity among the groups suggest age-dependent changes in activation of adenylyl cyclase at a prior step. This suggestion is also supported by the comparable inhibitory capacities of the alpha 2-adrenergic and A1-adenosine signaling systems among the age groups. In view of the similar levels of Gs alpha, the age-dependent decrease in adrenergic responsiveness in rat adipocytes appears to result primarily from specific decreases in the expression of both beta 3-AR and beta 1-ARs.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1994

Lymphohematopoietic progenitors immortalized by a retroviral vector harboring a dominant-negative retinoic acid receptor can recapitulate lymphoid, myeloid, and erythroid development.

The lymphohematopoietic progenitors represent < 0.01% of nucleated marrow cells. Here, we describe the immortalization of the murine lymphohematopoietic progenitors by a retroviral vector harboring a dominant-negative retinoic acid receptor. The immortalized progenitors proliferate as a stem-cell-factor-dependent clonal line EML that spontaneously generates pre-pro-B lymphocytes and erythroid and myeloid progenitors. Upon stimulation with interleukin-7 and stromal cells, the pre-pro-B lymphocytes express RAG-1 and undergo D-J rearrangements of the immunoglobulin heavy-chain genes. With erythropoietin the erythroid progenitors proliferate and differentiate into red cells. Generation of the common progenitors for neutrophils and macrophages is suppressed in EML but is inducible by high concentrations of retinoic acid. An additional block in neutrophil differentiation occurs at the promyelocyte stage but can also be overcome by high concentrations of retinoic acid. These studies demonstrate a reproducible way to immortalize lymphohematopoietic progenitors and implicate specific roles for retinoic acid receptors at two distinct stages of hematopoiesis.

Animals↗