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Biomedical subjects

J Ross

Publications and source records attributed to J Ross.

At least 487 records · Page 27Linked to original sources
PubMed1987

Expression of the 5'-flanking region of the beta major-globin gene in cultured murine erythroid precursor cells.

The amounts of mouse beta major-globin mRNA and globin gene upstream RNA polymerase III transcripts were compared during the differentiation of purified erythroid colony-forming progenitor cells (CFU-E) in vitro. The accumulation of each RNA was determined relative to the 100% levels in fetal liver erythroid cells. The mRNA level was low in freshly isolated CFU-E and began to accumulate only after a lag period of approximately 2-4 h. It continued to accumulate for approximately 40 h thereafter, at which point it was comparable to that in the fetal liver. In contrast, in three of four CFU-E preparations, the relative level of upstream RNAs was high in freshly isolated CFU-E and reached the maximal level (defined as 100% of the fetal liver level) more rapidly than did the mRNA. The early induction and accelerated accumulation of upstream RNAs in immature erythroid cells suggest some role for these RNAs at an early stage of globin gene activation.

Animals↗
PubMed1987

Back pain and spinal deformity in cystic fibrosis.

Back pain is a common complaint of individuals with cystic fibrosis (CF). We studied back pain in our patient population in three ways: a questionnaire, an orthopedic evaluation, and a survey of chest roentgenograms. Forty-seven patients with CF reported back pain as compared with seven controls. Patients with CF showed decreased muscle strength and mobility in the trunk, chest, and shoulders. The incidence of structural kyphosis was only 8.7%, but many had vertebral wedging. Much of the back pain may be due to postural abnormalities or to vertebral wedging, not fixed structural kyphosis.

Adolescent↗
PubMed1987

PUVA-induced blisters, complement deposition, and damage to the dermoepidermal junction.

We followed the course of 56 patients receiving psoralen plus long-wave ultraviolet light (PUVA) therapy. Nonhemorrhagic blisters developed on clinically normal skin on the limbs of seven patients. Seeming to be related to friction and trauma, the blisters form as a result of damage to the basal and suprabasal layers. Perilesional skin specimens from all blistered patients contained granular deposits of C3 at the dermoepidermal junction, around the upper dermal blood vessels, or at both sites. The average time for initiation and complete formation of suction blisters was measured in 51 patients at different stages during the course of PUVA treatment. Blister separation was in the lamina lucida, with the pemphigoid antigen in the roof while the blister floor contained the lamina densa, laminin, and type IV collagen. This impaired dermoepidermal adhesion was a general phenomenon that occurred in all PUVA-treated patients. The mechanism remains to be determined.

Adult↗
PubMed1987

Estimation of VO2max from a one-mile track walk, gender, age, and body weight.

The purpose of this investigation was to explore an alternative field test to estimate maximal oxygen consumption (VO2max) using a one-mile walk test. VO2max was determined in 343 healthy adult (males = 165, females = 178) subjects 30 to 69 yr using a treadmill protocol (mean +/- SD: VO2max = 37.0 +/- 10.7 ml X kg-1 X min-1). Each subject performed a minimum of two, one-mile track walks as fast as possible. The two fastest walks (T1, T2) with elapsed times within 30 s were used for subsequent analyses. Heart rates were monitored continuously and recorded every one-quarter mile. Multiple regression analysis (best sub-sets) to estimate VO2max (l X min-1) yielded the following predictor variables: track walk-1 time (T1); fourth quarter heart rate for track walk-1 (HR 1-4); age (yr); weight (lb); and sex (1 = male, 0 = female). The best equation (N = 174) was: VO2max = 6.9652 + (0.0091*WT) - (0.0257*AGE) + (0.5955*SEX) - (0.2240*T1) - (0.0115*HR1-4); r = 0.93, SEE = 0.325 l X min-1. Comparing observed and estimated VO2max values in a cross-validation group (N = 169) resulted in r = 0.92, SEE = 0.355 l X min-1. Generalized and sex-specific equations to estimate VO2max (ml X kg-1 X min-1) were also generated. The accuracy of estimation as expressed by SEE was similar among the equations. The results indicate that this one-mile walk test protocol provides a valid sub-maximum assessment for VO2max estimation.

Adult↗
PubMed1986

The establishment and spread of myxomatosis and its effect on rabbit populations.

The establishment of myxomatosis, the spread of the disease and its effects on rabbit populations in Australia and in Britain are briefly reviewed. Though the disease is endemic, with regular outbreaks in most rabbit populations, its effect is now much less dramatic than previously. Recent epidemiological studies have shown that the rate of spread of infection, the proportion of rabbits infected and the proportion dying from the disease are very much smaller than recorded in earlier outbreaks. The reasons for these changes are discussed, and the epidemiology of the disease in Britain is compared with that in Australia.

Animal Diseases↗
PubMed1986

Limitations and advantages of the ejection fraction for defining high risk after acute myocardial infarction.

Left ventricular (LV) ejection fraction (EF) is known to be related to prognosis after acute myocardial infarction (AMI), but its role alone and in combination with other factors in the definition of a high-risk group has not been adequately specified. Several recent multicenter studies emphasize that LVEF together with features of ventricular ectopic activity during ambulatory electrocardiography define a group at high risk for death for up to 3 years. However, these high-risk groups comprised only a small fraction of the population (less than 7.5%) and failed to include 75% or more (less than 25% specificity) of observed events. In our study, LVEF was determined close to the time of hospital discharge in 750 patients with AMI enrolled in a collaborative study. Used alone, an LVEF of less than 0.45 best defined a high-risk group (39% of the population) yielding 62% sensitivity and 64% specificity for total cardiac mortality by 1 year; it was 77% sensitive for sudden death alone. In a multivariate analysis together with other factors, LVEF was an independent predictor, but other markers of LV dysfunction entered before LVEF with similar sensitivity for total cardiac deaths, but with increased specificity (75%). When an LVEF of less than 0.45 was used together with the presence of complex arrhythmias to define a high-risk group (19% of the population), sensitivity decreased to 39% and specificity increased to 84%. Thus, LVEF is a simple and effective alternative to multivariate analysis for risk assessment after AMI.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Complexes, Premature↗
PubMed1986

H4 histone messenger RNA decay in cell-free extracts initiates at or near the 3' terminus and proceeds 3' to 5'.

The relative decay of four human messenger RNAs, gamma globin, delta globin, c-myc and H4 histone, were compared in a cell-free system. Under appropriate conditions, they are degraded in vitro in approximately the same relative order as in vivo: histone faster than c-myc and delta globin faster than gamma globin. Degradation of polysome-associated H4 histone mRNA and of deproteinized histone mRNA begins at or near the 3' terminus. At least a portion of the mRNA then continues to be degraded in a 3' to 5' direction. Discrete 3'-terminal degradation hold-up points are observed, suggesting that 3' to 5' degradation occurs non-uniformly. Cycloheximide and puromycin inhibit protein synthesis but do not affect the rate or directionality of histone mRNA decay in vitro. We conclude that the rate-limiting step in H4 histone mRNA decay occurs at or near the 3' terminus and that at least a portion of the mRNA molecule is subsequently degraded 3' to 5', probably via a processive exonuclease.

Cycloheximide↗
PubMed1986

Seeing objects in motion.

This paper reports estimates of the conjoint spatiotemporal tuning functions of the neural mechanisms of the human vision system which detect image motion. The functions were derived from measurements of the minimum contrast necessary to detect the direction of drift of a sinusoidal grating, in the presence of phase-reversed masking gratings of various spatial and temporal frequencies. A mask of similar spatial and temporal frequencies to the test grating reduces sensitivity considerably, whereas one differing greatly in spatial or temporal frequency has little or no effect. The results show that for test gratings drifting at 8 Hz, the tuning function is bandpass in both space and time, peaked at the temporal and spatial frequency (SF) of the test (SFs were 0.1, 1 or 5 c deg-1; c represents cycles throughout). For a grating of 5 c deg-1 drifting at 0.3 Hz, the function is bandpass in space but lowpass in time. Fourier transform of the frequency results yields a function in space-time which we term the 'spatiotemporal receptive field'. For movement detectors (bandpass in space and time) the fields comprise alternating ridges of opposing polarity, elongated in space-time along the preferred velocity axis of the detector. We suggest that this organization explains how detectors analyse form and motion concurrently and accounts, at least in part, for a variety of perceptual phenomena, including summation, reduction of motion smear, metacontrast, stroboscopic motion and spatiotemporal interpolation.

Differential Threshold↗
PubMed1986

Cyclopia as a result of an unbalanced familial translocation, rcp(7;18)(q34;q21)

One fetus is described with cyclopia and associated abnormalities as a result of an unbalanced translocation involving chromosomes 7 and 18 [46XX,del 7, rcp(7;18)(q34;21)]. The parents had had a previous infant described as having possible holoprosencephaly, but no medical records were available to substantiate this description.

Chromosome Aberrations↗
PubMed1986

Value and limitations of Doppler ultrasound in the evaluation of aortic stenosis: a statistical analysis of 70 consecutive patients.

Continuous-mode Doppler ultrasound and cardiac catheterization were performed within 1.4 +/- 2.0 days in 70 patients, aged 26 to 84 (mean 67 +/- 11) years, with suspected aortic stenosis. Optimal Doppler spectral display signal was recorded from the apical window in 43% of the patients, the second or third right parasternal area in 34%, and from the suprasternal notch view in 20% of the patients. Aortic valve gradients by Doppler ultrasound were calculated by the simplified Bernoulli equation: pressure gradient = 4X (velocity). There was an overall fair correlation between the peak gradient by Doppler technique and both the maximal instantaneous (r = 0.66) and peak-to-peak aortic pressure gradient (r = 0.68) obtained at catheterization and a good correlation (r = 0.75) between mean gradient by Doppler technique and catheterization. These correlation coefficients improved significantly in the last 51 patients as compared to the initial 19 patients of the study. Of the last 51 patients, correlation was better in those in normal sinus rhythm as compared to those in atrial fibrillation, and in patients with no or insignificant coexistent AR as compared to those with greater than or equal to 2+ AR. The age of the patient and the status of cardiac output did not significantly affect the accuracy of correlations. We conclude that measurements of aortic valve gradient by continuous-mode Doppler ultrasound may not correlate closely with those by catheterization when the experience with the Doppler technique is limited and when patients in atrial fibrillation or with significant coexistent AR are studied.

Adult↗
PubMed1986

The relative cytotoxicity and mutagenicity of cyclobutane pyrimidine dimers and (6-4) photoproducts in Escherichia coli cells.

In order to calculate the relative cytotoxicity and mutagenicity of (5-6) cyclobutane pyrimidine dimers and (6-4) photoproducts, we have measured survival and mutation induction in UV-irradiated excision-deficient E. coli uvrA cells, with or without complete photoreactivation of the (5-6) dimers. Radioimmunoassays with specificity for (5-6) dimers or (6-4) photoproducts have shown that maximum photoreactivation eliminates all of the (5-6) dimers produced up to 10 Jm-2 254-nm light, while it has no effect on (6-4) photoproducts. These results were confirmed by measuring the frequency of T4 endonuclease V-sensitive sites. Based on the best fit equations for survival and mutation induction, we have found that the calculated cytotoxicity of (6-4) photoproducts is similar to that of (5-6) dimers; however, the former is much more mutagenic than the latter.

Dose-Response Relationship, Radiation↗
PubMed1986

Smooth and sampled motion.

Stroboscopic or sampled motion is indistinguishable from smooth motion if the frequency of sampling is sufficiently high. We report measurements of the minimum sample frequency for smooth motion of drifting sinusoidal gratings (extended and truncated) which varied in spatial frequency from 0.06 to 24 c/deg, in temporal frequency from 1.5 to 24 Hz and in contrast from 3 to 100 times detection threshold. Threshold sampling frequency for smoothness increased with temporal frequency and contrast, and inversely with spatial frequency. The threshold step size associated with the sampling frequency ranged from 20" arc (for gratings of 24 c/deg) to 6 deg (for gratings of 0.06 c/deg). Calculations of the spurious frequencies introduced by sampling lead us to conclude that motion appears smooth provided that sampling is above the Nyquist limit and that the amplitude of the spurious components is below their independent threshold.

Humans↗
PubMed1986

Local and global visual processing.

The fundamental sinusoidal components of a chequerboard pattern are oriented at 45 degrees to the orientation of the chequerboard edges. Removal of one of the fundamental sinusoids (at +45 degrees) creates a useful pattern for studying the mechanisms of visual analysis. Close up, the pattern appears to be oriented +45 degrees, although there is no global energy at that orientation, implying local analysis. At a distance, the perceived diagonality switches to -45 degrees implying access to global information. Measurements show that contrast thresholds for seeing diagonality at +45 degrees follow closely those for detecting the 5th harmonic component of the pattern, over a wide range of spatial frequencies and luminances. Low pass filtering also causes the pattern to be perceived according to its global energy, provided that the cutoff frequency is set to remove the fifth harmonic. We conclude that, at least for this particular stimulus, the visual system performs a local analysis if the fifth harmonic is visible and a global analysis if not.

Form Perception↗
PubMed1986

Accurate in vitro initiation of beta-globin gene transcription in induced Friend-cell nuclei.

The initiation of transcription by RNA polymerase II in isolated murine erythroleukemia cell nuclei was investigated by isolating newly synthesized gamma-thio (gamma-S-)-triphosphate-labeled transcripts by Hg-agarose chromatography. The 5' terminus of transcripts initiated in vitro with [gamma-35S]ATP or [gamma-35S]GTP was identified as the thiotetraphosphate in alkaline hydrolysis products from Hg-agarose-selected RNA. Additional control experiments analyzing the nuclear transcription of two well characterized tRNA genes showed that each gene was initiated with the proper triphosphate, either gamma-S-ATP or gamma-S-GTP, indicating little, if any, exchange of the gamma-S-labeled substrate to the other triphosphates. As determined by S1 mapping, newly synthesized beta-globin gene transcripts initiate only with gamma-S-ATP. Their 5'-terminus is located at the cap site, and their synthesis is inhibited by 1 microgram alpha-amanitin/ml. In reactions containing gamma-S-ATP but not gamma-S-GTP, several additional initiation sites are observed that are located in the 5'-flanking region. We conclude that RNA polymerase II can initiate transcription at the cap site in isolated nuclei.

Amanitins↗
PubMed1986

Normal and abnormal prosthetic valve function as assessed by Doppler echocardiography.

Doppler echocardiography was performed in 136 patients with a normally functioning prosthetic valve in the aortic (n = 59), mitral (n = 74) and tricuspid (n = 3) positions. These included patients with St. Jude (n = 82), Björk-Shiley (n = 18), Beall (n = 13), Starr-Edwards (n = 7) or tissue (n = 16) valves. Peak and mean pressure gradients across the prostheses were measured using the simplified Bernoulli equation. The prosthetic valve orifice (PVO, in square centimeters), only in the mitral position, was calculated by the equation: PVO = 220/pressure half-time. In the aortic position, the St. Jude valve had a lower peak velocity (2.3 +/- 0.6 m/s, range 1.0 to 3.9), peak gradient (22 +/- 12 mm Hg, range 4 to 61) and mean gradient (12 +/- 7 mm Hg, range 2 to 32) than the other valves (p less than 0.05) when compared with Starr-Edwards). In the mitral position, the St. Jude valve had the largest orifice (3.0 +/- 0.6 cm2, range 1.8 to 5.0) (p less than 0.0001 compared with all other valves). Insignificant regurgitation was commonly found by pulsed mode Doppler technique in patients with a St. Jude or Björk-Shiley valve in the aortic or mitral position and in patients with a Starr-Edwards or tissue valve in the aortic position. In 17 other patients with a malfunctioning prosthesis (four St. Jude, two Björk-Shiley, four Beall and seven tissue valves) proven by cardiac catheterization, surgery or autopsy, Doppler echocardiography correctly identified the complication (significant regurgitation or obstruction) in all but 2 patients who had a Beall valve. It is concluded that 1) the St. Jude valve appears to have the most optimal hemodynamics; mild regurgitation can be detected by the Doppler technique in normally functioning St. Jude and Björk-Shiley valves in the aortic or mitral position and in Starr-Edwards and tissue valves in the aortic position, and 2) Doppler echocardiography is a useful method for the detection of prosthetic valve malfunction, especially when the St. Jude, Björk-Shiley and tissue valves are assessed.

Adolescent↗