Biomedical subjects
Publications and source records attributed to S J Phillips.
A 39-year-old man presented with a pure motor stroke 9 days after cervical chiropractic manipulation. Computerised tomographic scanning showed a pontine infarct. Cerebral angiography showed changes consistent with the diagnosis of bilateral vertebral artery dissection. It is postulated that the infarct resulted from artery-to-artery embolism.
The purpose of this study was to compare the knee extensor demands and low back injury risks of the front and back squat exercises. Highly strength-trained college-aged males (n = 8), who performed each type of squat (Load = 75% of front squat one repetition maximum), were filmed (50 fps) from the sagittal view. The body was modeled as a five link system. Film data were digitized and reduced through Newtonian mechanics to obtain joint forces and muscle moments. Mean and individual subject data results were examined. The maximum knee extensor moment comparison indicated similar knee extensor demands, so either squat exercise could be used to develop knee extensor strength. Both exercises had similar low back injury risks for four subjects, but sizable maximum trunk extensor moment and maximum lumbar compressive and shear force differences existed between the squat types for the other subjects. The latter data revealed that with the influence of trunk inclination either exercise had the greatest low back injury risk (i.e., with greater trunk inclination: greater trunk extensor demands and lumbar shear forces, but smaller lumbar compressive forces). For these four subjects low back injury risk was influenced more by trunk inclination than squat exercise type.
Chronically elevated blood pressure predisposes to stroke through effects on the extracranial and intracranial cerebral vessels. Hypertension-associated disease of small-diameter penetrating cerebral arteries may produce either lacunar infarction or intracerebral hemorrhage. The role of hypertension in the pathogenesis of atherothromboembolic cerebral infarction must be questioned in view of the evidence that antihypertensive therapy does not prevent myocardial infarction. Hypertension, in the absence of rheumatic heart disease, is frequently associated with atrial fibrillation. The incidence of stroke due to embolization of thrombus from the fibrillating left atrium of the nonrheumatic heart may have been overestimated in the past. Ideally, investigation of the patient who has had a stroke should include a brain-imaging study and a cerebral arteriogram. In practice, however, arteriography cannot always be justified. Treatment of the completed stroke is unsatisfactory but tissue plaminogen activator and calcium-channel blockers hold promise for cerebral infarction. Surgical decompression of the posterior fossa can be life-saving in cases of cerebellar infarction or hemorrhage. In patients with cerebral infarction, aspirin has been shown to reduce the incidence of stroke recurrence.
We report the isolation and characterization of two recombinant clones containing DNA derived from the Y chromosome of the C57BL/10 inbred mouse strain. Both clones were isolated from a lambda phage library derived from a partial EcoRI digest of C57BL/10 male DNA using the murine retrovirus M720. Characterization of these clones showed they were derived from a repeated segment present on the C57BL/10J Y chromosome that contains sequences found elsewhere in the genome. In addition, one clone contained a sequence, designated YB10, that is unique to the Y chromosome and present in approximately 500 copies on the C57BL/10J Y chromosome. Analysis of Southern blots containing DNAs prepared from females and males of representative species from four subgenera of Mus probed with pYB10 and the 3'LTR from one of the Y-associated retroviruses (MuRVY) revealed that, with the exception of a single fragment observed in both female and male DNA of Mus saxicola, hybridization to pYB10 was observed only to male DNA of the species Mus spretus, Mus hortulanus, Mus musculus, Mus domesticus and Mus abbotti. In addition, the pattern and intensity of hybridization to YB10 and the MuRVY-LTR indicated that sequence of divergence was followed by amplification of Y chromosome sequences containing YB10 and MuRVY. The divergence and amplification occurred separately in each of the ancestral lineages leading to M. spretus, M. hortulanus, M. abbotti, M. musculus and M. domesticus. We suggest that acquisition and amplification of DNA sequences by the mammalian Y chromosome has contributed to its evolution and may imply that the mammalian Y chromosome is evolving at a faster rate than the rest of the genome.
Two outstanding problems pertaining to the population dynamics and evolution of the t complex in mice concern the frequency of t haplotypes in the wild and the degree to which these haplotypes recombine with their wild-type homologs. To address these problems, the frequency and distribution of several t complex-associated restriction fragment variants in wild mice were estimated. Sixty-four versions of chromosome 17 from wild-derived Mus musculus musculus and Mus musculus domesticus were examined with DNA probes for six loci within the t complex that exhibit restriction fragment variation. All six probes detect variants that have heretofore been found exclusively associated with the t complex. Haplotype analysis of wild-derived chromosomes revealed a high frequency (45.3%) of "mosaic" haplotypes with a mixture of t-specific and wild-type variants and only one haplotype with t-specific variants at all six loci. When 12 well-characterized t haplotypes isolated from diverse geographic regions were analyzed, only three had a complete set of t-specific restriction fragments for the six loci examined. The preponderance of mosaic haplotypes in both groups of mice can be explained by any one of the following hypotheses: genetic recombination between t haplotypes and their wild-type homologs, the persistence in wild populations of haplotypes that have descended from ancestral partial t haplotypes, or that the restriction fragment variants fixed in the ancestral t haplotype were also fixed in some wild-type haplotypes. There is evidence to support all three of these hypotheses in our data. The allelic composition of some mosaic haplotypes indicates that they may have been formed by segmental recombination, either double crossing over or gene conversion, rather than by simple single crossovers. The occurrence of indistinguishable mosaic haplotypes in both M. m. musculus and M. m. domesticus suggests that these haplotypes are ancestral rather than recently derived.
We have determined the pigeon's head orientation for two postures and two locomotor activities that do not involve a specific visual stimulus. Using a high-speed cine camera, we filmed four pigeons (Columba livia) while (1) flying, (2) walking, (3) perching and (4) standing on a flat surface. Under these conditions, the head orientation is relatively constant, allowing us to estimate the normal horizon of the visual field and thus the horizontal meridian of the retina. Measurements of the lateral semicircular canal showed that the canal is tilted slightly up with respect to the horizon in the head orientation determined by the film analysis. In contrast to their relatively stable head posture during locomotion, the pigeons consistently altered their head orientation when presented with seed targets, apparently to fixate each seed with a small portion of the visual field around the bill tip.
Despite the lack of evidence of its efficacy, heparin therapy has been recommended for selected patients with ischemic stroke syndromes. However, heparin has procoagulant effects on platelet function and a propensity to produce serious side effects. When these factors are considered, heparin loses its appeal as a therapeutic agent for patients with acute focal cerebral ischemia.
Studies of the population of Rochester, Minnesota, have provided the only data on temporal trends for the incidence of stroke in North America. Among the residents of Rochester, the average annual incidence rate of stroke declined by 46%, from 213 to 115 per 100,000 population, between 1950-1954 and 1975-1979. The decline occurred in all age and sex groups, but it occurred earlier in women than in men. The rates stabilized in the 1970s, and did so earlier in women. For 1980-1984, the incidence rate of stroke was 17% higher than that for 1975-1979. The onset of the decline in incidence rates coincided with the introduction of effective antihypertensive therapy, but stabilized and increased rates were associated with continuing improvement in the control of hypertension. The increase in the incidence rates of stroke coincided with the introduction of computed tomography, which appeared to increase the detection of less severe strokes.
There is a large population of patients in end-stage congestive heart failure who cannot be treated by means of conventional cardiac surgery, cardiac transplantation, or chronic catecholamine infusions. In 2 such patients, we provided permanent left ventricular assistance on an outpatient basis by surgically implanting a modified intra-aortic balloon pump. A Dacron-velour graft to the common iliac artery served as a covering for the extravascular portion of the balloon's pneumatic tubing, which was stabilized by routing it through the iliac crest. The tubing was then carried ventrally to exit through a stoma just above the inguinal ligament. Before hospital discharge, each patient underwent a 5-day regimen of alternate pumping and ambulation. The patient was then permitted to go home, but returned daily as an outpatient in accordance with individual need, for approximately 6 hours of hemodynamic support. The 1st patient lived 3 months after pump insertion, and the 2nd patient for 38 days. Although the 1st patient developed a fever of unknown origin that prompted us to remove the intra-aortic balloon pump unnecessarily, there was no evidence of infection upon surgical exploration and subsequent tissue culturing; she died, rather, of intractable ventricular fibrillation, apparently consequent to her 36-hour loss of hemodynamic support. The 2nd patient also died of a cause unrelated to the presence of the pump, and on autopsy showed good evidence of healing and absence of infection. On the evidence of this pilot study, we conclude that intermittent left ventricular assistance, through periodic activation of a permanently implanted intra-aortic balloon pump during outpatient visits, warrants further study as an alternative for selected patients with end-stage heart disease, when medical and other surgical options have been exhausted.
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A versatile retractor is described that can be used to harvest either mammary artery without disturbing the operative field and can be converted to a standard sternotomy retractor. It uses the principle of elevating the cut sternal edge and applying external pressure to the area of the costochrondal junction to rotate the mammary pedicle into view. We have used this retractor and found it to be very efficient in exposing the mammary pedicle while being atraumatic to the sternum.
The organization of interlimb coordination was studied in newly walking infants with and without support and in infants who had been walking 0.5, 1, 3, and 6 months. Analysis of the temporal and distance phase relationships between the limbs revealed that newly walking infants exhibit interlimb coordination similar to that of mature walkers. The coupling between the limbs, however, is loosely constrained, approaching adult-like consistency after 3 months of walking. Providing support for the newly walking infant afforded a more consistent, mature coordination suggesting that neuromuscular development is in advance of its ability to function in the physical world.
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In 1975, 80 patients undergoing revascularization were prospectively randomized to receive either a greater saphenous vein (SV) graft (41 patients, Group 1) or a left internal mammary artery (LIMA) graft (39 patients, Group 2) to the left anterior descending coronary artery (LAD). All patients were completely revascularized. The average number of grafts per patient in both groups was 3.2. Patients were followed 10 years; follow-up was 97.5% complete. Group 1 and Group 2 were compared in regard to mortality, treadmill response, myocardial infarction, reoperation, percutaneous transluminal coronary angioplasty, and return to work. Mortality in Group 1 was 17.9% versus 7.7% in Group 2 (p less than 0.05). Treadmill studies were positive in 17 Group 1 patients and 7 Group 2 patients (p less than 0.05). Myocardial infarctions occurred in 8 patients in Group 1 versus 3 in Group 2. The number of reoperations was 2 in Group 1 versus 1 in Group 2. Percutaneous transluminal coronary angioplasty was performed in 3 patients in Group 1 and 2 in Group 2. Repeat studies revealed 76.3% patency of the SV graft to the LAD (Group 1) and 94.6% patency of the LIMA graft to the LAD (Group 2). Cardiac-related mortality in Group 1 was 12.8% at 10 years (5 patients) versus 7.7% in Group 2 (3 patients). Based on this study, the IMA is a superior conduit for bypass to the LAD.
To determine the prevalence and control of hypertension in the adult population of Rochester, Minnesota, a blood pressure survey was conducted among a stratified random sample of 2,122 subjects 35 years of age or older. Hypertension--defined as a history of hypertension or a systolic pressure of 160 mm Hg or more, a diastolic pressure of 95 mm Hg or more, or both at the time of interview--was found in 663 subjects (31%). Among these hypertensive subjects, 82 (12%) had no prior history of hypertension. Of the 581 subjects with a history of hypertension, 447 (77%) were taking antihypertensive medication, 127 (22%) had a systolic pressure of 160 mm Hg or more, a diastolic pressure of 95 mm Hg or more, or both, and 288 (50%) had a systolic pressure of 140 mm Hg or more, a diastolic pressure of 90 mm Hg or more, or both. Of the treated patients with hypertension, 75% were taking a diuretic either alone or in combination with one or more other agents. Side effects of therapy were reported by 12% of subjects taking antihypertensive medication.
Multiple regression analysis were used to investigate the relationship between blood pressure and age, sex, relative weight, antihypertensive medication, diabetes mellitus, diet (low-salt, low-cholesterol, and weight-reducing regimens), cigarette smoking, coffee drinking, and aerobic exercise among a stratified random sample of the population of Rochester, Minnesota, 35 years of age or older. Age, sex, relative weight, antihypertensive medication, and cigarette smoking were significantly correlated with blood pressure and were incorporated in regression models of systolic and diastolic pressure. These models were used to predict average (geometric mean) blood pressure values for the adult population of Rochester and to predict age-, sex-, and relative weight-specific blood pressure percentiles.