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Biomedical subjects

M Mitchell

Publications and source records attributed to M Mitchell.

At least 19 recordsLinked to original sources
PubMed1992

Appropriateness of the Draw-A-Person test with Alaskan Native populations.

The appropriateness of the Draw-A-Person test with Alaskan Native populations was assessed by matching 33 White subjects to 33 Alaskan Native subjects, asking them to perform the DAP, and rating their performance according to eight criteria chosen for their clinical relevancy. Results indicated that neither level of commitment to Native culture nor ethnicity per se affected drawing ratings. It is hypothesized that the DAP is a useful clinical tool appropriate for use with Alaskan Native populations.

Acculturation↗
PubMed1992

Case report 713. Chondromyxoid fibroma of the third metatarsal.

In the case presented, the imaging features are those of an aggressive benign or less aggressive malignant lesion. The differential diagnosis radiographically included aneurysmal bone cyst with or without an accompanying lesion, giant cell tumor synovial sarcoma, and other mesenchymal sarcomas. Indeed, at times it is difficult to be certain whether the process originated in the bone or soft tissue. Pathological examination of the resected specimen showed the typical features of chondromyxoid fibroma. Grossly, the tumor was well demarcated and firm and composed of tan, translucent tissue that destroyed cortex but was confirmed by periosteum. Histologically, the tumor consisted of myxoid, chondroid, and fibrous elements. The tumor lobules were composed of predominately myxoid matrix containing stellate cells. Variable chondroid elements were present with immature appearing chondrocytes, containing eosinophilic cytoplasm and irregularly shaped nuclei.

Adult↗
PubMed1992

Evolution of DNA sequence homologies between the sex chromosomes in primate species.

Cloned DNA sequences from 18 X-Y homologous loci have been used to examine the evolution of regions of homology between the human X and Y chromosomes. The pattern of X-Y linkage in different primate species has enabled the charting of the chronology of their appearance and removal from the sex chromosomes during evolution. Examination of the pattern of differences in restriction enzyme sites at different loci has been used to estimate the degree of divergence in three different regions of homology. These studies have indicated that (1) blocks of homology have arisen at different points in evolution, (2) different regions of homology are heterogeneous in composition in that they contain X-Y homologous sequences of different age, and (3) the combination of X and Y locations together with the point of evolutionary origin has defined five new patterns of homology.

Animals↗
PubMed1992

Preimplantation diagnosis of a human beta-globin transgene in biopsied trophectoderm cells and blastomeres of the mouse embryo.

The preimplantation diagnosis of a HbSA-globin transgene in biopsied trophectoderm cells and blastomeres in embryos using a transgenic mouse model for the trait of human sickle-cell anaemia has been undertaken. A sensitive procedure was developed for the amplification of the human beta-globin gene sequence flanking the sickle mutation. Polymerase chain reaction (PCR) assays were undertaken on one to five biopsied trophectoderm cells and isolated blastomeres of the preimplantation mouse embryo. After biopsy the blastocysts were cultured whilst the cells were analysed for the presence of the transgene, and a high proportion (82-91%) were viable as assessed by the presence of a blastocoele cavity within a 5-h period. The majority of the biopsied cultured blastocysts were frozen and used to confirm the diagnosis; 90 biopsied cultured blastocysts were transferred to pseudopregnant recipients and 34% established pregnancy. Material from day 13.5 post-coitum fetuses was also used to confirm the original diagnosis. The time (4-5 h) required to carry out the analysis obviates a need for extended culture or cryopreservation of the biopsied embryo. In individual experiments under optimal conditions, the presence of the transgene in biopsied cells was detected with 100% accuracy, and the PCR analysis was sensitive at the 1-cell level. The overall success rate of diagnosis and confirmation of the presence or absence of the human beta-globin sequence in the biopsied embryo was 70%. Over the entire experimental period (14 months) DNA contamination from a variety of sources did occasionally occur; the methods used to overcome this problem are discussed.

Anemia, Sickle Cell↗
PubMed1992

Effect of 48-hour infusion of the synthetic oxytocin antagonist, [1-beta-mercapto(beta-(CH2)5)1(OMe)Tyr2,Orn8]-oxytocin, on myometrial activity of pregnant sheep at 139-140 days of gestation.

Currently there is considerable interest in the actions of oxytocin antagonists on the pregnant myometrium. Few studies have been conducted involving long-term infusions of oxytocin antagonists to late-pregnant experimental animals. We set out to determine whether continuous infusion of an oxytocin antagonist ([1-beta-mercapto(beta-(CH2)5)1(OMe)Tyr2,Orn8]-oxytocin) would influence basal levels of myometrial activity of the contracture type and maternal prostaglandins in pregnant sheep. The antagonist was infused into a uterine vein at 80 micrograms.h-1 for 48 h starting at 139 days of gestational age. The antagonist significantly reduced total myometrial electromyogram activity and the frequency of contractures but did not change contracture duration. Antagonist infusion did not produce any significant alterations in maternal carotid or uterine vein 13,14-dihydro-15 keto prostaglandin F2 alpha concentrations. Contractures probably represent an intrinsic instability of the resting membrane potential of uterine muscle and these results suggest that oxytocin may play a role in regulating their frequency in sheep during the last third of gestation.

Animals↗
PubMed1992

Knee effusion: normal distribution of fluid.

Although visualization of articular fluid on MR images of the knee is common, no specific MR criteria that enable assessment of the quantity of the effusion have been established. We performed MR of three cadaveric knee specimens after the instillation of increasingly large volumes of fluid and studied the distribution of the fluid. When 4 ml of fluid was injected, the anteroposterior diameter of the suprapatellar recess was 4 mm on midline sagittal MR images and 10.0-12.5 mm on lateral sagittal MR images, corresponding to the usual routine radiographic criteria for a knee effusion.

Humans↗
PubMed1992

Prostaglandin production in the umbilical and uterine circulations in pregnant sheep at 129-136 days gestation.

Prostaglandins circulating in the maternal and foetal blood have been implicated in important physiological systems. These functions include foetal adrenal function, maintenance of patency of the ductus arteriosus, regulation of uterine and umbilical circulations, and labor and delivery type myometrial contractions. The placenta is a major site of prostaglandin production in pregnancy. Limited data are available which combine measurements of veno-arterial differences across the uterine and umbilical circulations with blood flow in these circulations to enable calculation of umbilical-placental and utero-placental production rates for the prostaglandins. In chronically instrumented pregnant ewes, between 129 and 136 days of gestation, prostaglandin F2 alpha(PGF2 alpha), 13, 14 dihydro-15-keto prostaglandin F2 alpha (PGFM), prostaglandin E2 (PGE2) were measured in the maternal carotid artery and uterine vein. Foetal PGE2, and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) (the major metabolite of prostacyclin) were measured in umbilical venous and foetal descending aorta arterial plasma. Umbilical and uterine blood flow were measured using the diffusion-equilibrium technique. Uterine blood flow was 1693 +/- 137 ml.min-1 (mean +/- SEM); uterine production rates were 480 +/- 88 ng.min-1 for PGF2 alpha, 517 +/- 144 ng.min-1 for PGFM, and 165 +/- 27 ng.min-1 for PGE2. Umbilical blood flow was 147 +/- 17 ml.min-1.kg-1 foetal body weight. Umbilical production rates into the foetal circulation were 11 +/- 2 ng.min-1.kg-1 for PGE2 and 6 +/- 2 ng. ng.min-1.kg-1 foetal body weight for PGI2.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Reduction of morbidity and mortality from biliary complications after liver transplantation.

Over a 4-yr period that began October 1, 1986, 103 orthotopic liver transplants were performed on 91 patients at the Johns Hopkins Hospital. Biliary reconstruction at the time of transplantation was performed in standard fashion by an appropriately trained member of the surgical team. Six (7%) patients developed biliary complications, which included three cases of common bile duct stricture and one case each of bile duct obstruction caused by biopsy-related hemobilia, biloma and a retained fragment of a T tube after removal. Five of the six patients were treated successfully by nonoperative interventional radiological procedures performed under local anesthesia with light intravenous sedation. Reoperative surgery (to remove the T-tube fragment from subcutaneous tissue) was required for only one patient, and no deaths (0 of 91) were attributable to biliary complications. All six patients are alive and well 6 to 33 mo after the operation with excellent liver function. Our findings would suggest that most biliary complications of orthotopic liver transplants are avoidable and that the few that do appear can usually be managed both safely and effectively by an interventional radiological approach.

Adult↗
PubMed1991

Effects of remoxipride on measures of psychological performance in healthy volunteers.

The acute psychomotor effects after oral doses of 30, 60 and 120 mg remoxipride, a new selective D2 receptor blocker, and placebo were investigated in a double-blind crossover study in 11 healthy male volunteers. Two out of the first three subjects given 120 mg remoxipride experienced marked akathisia, and therefore no subsequent subjects were given this dose. There were no other clearly drug-related adverse effects reported below 120 mg, although restlessness was reported at 60 mg. Remoxipride was associated with increases in error scores on a continuous attention task and on auditory vigilance, and with a reduction in critical flicker frequency, suggesting a decrease in arousal level. There were no significant changes in psychomotor measures such as choice reaction time, decision making time, or body sway. Subjective assessments using visual analogue scales showed a slight dose-related increase in drowsiness, while the calm-excited scale showed a small change in the excited direction with 30 mg only. The peak effects were at 4-6 h after drug intake, which was later than expected from previous pharmacokinetic data. These results indicate that remoxipride may have a slight depressant effect in the dose-range used. The pattern of changes is consistent with current theories on the role of dopamine in attention and arousal, and with the effects of other neuroleptics. It differs, however, from tranquilisers such as the benzodiazepines, which show a more global pattern of effects.

Adult↗
PubMed1991

Studies on the efficacy of deltamethrin applied to cattle for the control of tsetse flies (Glossina spp.) in southern Africa.

The tsetse fly (Glossina spp.) inhabits 11 million km2 of Africa (Greekmore, 1989) where it is responsible for the transmission of trypanosomosis to man and animals. Because of its slow rate of reproduction, with females producing only four to five pupae per annum, control of the tsetse fly is the best means of controlling trypanosomosis. A number of different methods have been and are used but, whilst successes have been achieved, a long term solution has not been found.

Administration, Topical↗
PubMed1991

Somatosensory evoked potentials in intracranial hypertension: analysis of the effects of hypoxia.

The loss of somatosensory evoked potentials (SSEP's) was investigated in a feline model of intracranial hypertension. Threshold values of cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) required for maintenance of SSEP's are defined using a mathematical model. The model describes loss of amplitude of SSEP's using the form of a dose-response curve. Amplitude of the SSEP's declined to 50% of control values at a CBF of 15 ml/100 gm/min and a CPP of 20 mm Hg in the normoxic animal; in the presence of mild hypoxia (8 to 9 kPa), a significant increase in these values to 18 ml/100 gm/min and 32 mm Hg, respectively, occurred. No reliable changes in latency or central conduction time were demonstrated. It is concluded that given adequate oxygenation, evoked electrical activity is lost at too low a level of CPP for this parameter to be useful in clinical monitoring. However, even mild hypoxia, when combined with intracranial hypertension, produces a major risk to neuronal integrity.

Animals↗
PubMed1991

Insulin induced fetal hypoglycaemia and fetal and maternal plasma prostaglandin concentrations in sheep in late gestation.

Fetal hypoglycaemia consequent on food withdrawal for 48 h in sheep in late pregnancy is accompanied by an increase in fetal PGE2 plasma concentrations and myometrial contractility. To assess the contribution of fetal hypoglycaemia and related cellular glucopenia in the increased production of fetal PGE2 we studied the effect of 48 h insulin infusion to the fetus. Fetal whole blood glucose was lowered from 19 +/- 2 to 9 +/- 1 mg.dl-1. This experimental regimen maintains glucose availability to those fetal cells in which insulin increases glucose uptake. Fetal umbilical venous and femoral arterial PGE2 concentrations and umbilical veno-arterial PGE2 difference were unchanged, but maternal uterine veno-arterial difference for PGFM increased during the insulin induced fetal hypoglycaemia. Myometrial activity was also unchanged. We conclude that the increased fetal PGE concentration previously reported during food withdrawal is due to a deficiency of glucose to specific insulin dependent cells within vascular beds served by the fetal cardiovascular system. In addition, the findings suggest a need for a supply of glucose of fetal origin for cells that are responsible for increased PGFM concentrations in the maternal uteroplacental circulation.

Adrenocorticotropic Hormone↗
PubMed1991

The cost of rural health services in Papua New Guinea.

In 1988 a countrywide study was conducted on the costs of rural health services in Papua New Guinea. 16% of all health centres and subcentres were surveyed. Information was collected on physical facilities, recurrent costs, staff time allocation, service outputs and quality of services. Wide variation was found in the costs of rural health facilities overall, and significant differences were found between the costs and outputs of health centres and subcentres. Average levels of service output were found to be similar at church and government facilities but average levels of utilization by the population were higher at church facilities. Despite government policy on extension of preventive health care, a strong emphasis was found on curative care. Many facilities were found to have significant excess bed capacity. Recurrent financing for transportation and maintenance was found to be inadequate.

Cost Allocation↗