Biomedical subjects

M A Adams

Publications and source records attributed to M A Adams.

At least 145 records · Page 8Linked to original sources

PubMed1986

The stages of disc degeneration as revealed by discograms.

One hundred and thirty-nine discs from cadaveric lumbar spines were injected with a mixture of radio-opaque fluid and dye. Discograms were taken and the discs were then sectioned in the sagittal plane. Examination of the sections revealed that injected fluid did not at first mix with the disc matrix but pushed it aside to form pools of injected fluid. The location of these pools, and hence the appearance of a discogram, depended on the stage of degeneration of the disc. It is concluded that useful clinical information can be obtained from discograms.

Adolescent↗

PubMed1986

The effect of posture on diffusion into lumbar intervertebral discs.

The diffusion of small solutes into the intervertebral discs of cadaveric lumbar motion segments was measured using a radioactive tracer technique. The motion segments were wedged and loaded to simulate erect posture and flexed sitting postures. The results show that erect posture favours diffusion into the anterior half of the disc compared to the posterior half. Flexed posture, by deforming the annulus fibrosus, reverses this imbalance.

Adolescent↗

PubMed1985

The influences of ethanol and other factors on the excretion of urinary salsolinol in social drinkers.

Salsolinol, a substance that may participate in the development of alcoholism, has been identified in urine and other biological samples from alcoholics. Differentials have been observed between alcoholics and controls. Salsolinol forms when dopamine reacts with acetaldehyde, which may exist in higher concentrations in the blood of alcoholics after alcohol ingestion. Hence, it was postulated that there is a relationship between level of social drinking and the elaboration of salsolinol. Salsolinol is also found in certain food and beverage products. Eighty volunteers, balanced for gender, social drinking level, ethanol dose administered and experimental diet provided urine samples 90 minutes and three hours after ethanol was consumed. Salsolinol levels were analysed in urine using high performance liquid chromatography. A 24 hour carryover effect was observed. Diet, ethanol dose and social drinking level had main and interactive effects on excreted quantities of salsolinol. Gender, situational stress and cigarette smoking had minor if any influence on salsolinol excretion. While there was no evident difference in amounts of salsolinol excreted by light and heavy drinkers in the absence of external sources of salsolinol, heavy social drinkers excreted less salsolinol than did light drinkers after consuming a "salsolinol-enriched" diet, suggesting that they differ in some aspect of absorption, distribution, or metabolism of salsolinol after drinking ethanol. Accordingly, studies that attempt to determine whether salsolinol has any relationship to drinking behaviour in humans should be particularly concerned with salsolinol that occurs in exogenous sources.

Adult↗

PubMed1985

The effects of hepatocyte stimulating factor on fibrinogen biosynthesis in hepatocyte monolayers.

The biosynthesis of fibrinogen increased at least eightfold in primary hepatocytes when incubated in the presence of monocyte/macrophage-derived hepatocyte stimulating factor (HSF). The large increase in fibrinogen production is due to increased availability of the mRNAs for the protein since cytodot analysis of cellular RNA showed a 10-12-fold increase in each of the fibrinogen mRNAs. Pulse-chase experiments showed that the time for fibrinogen synthesis, assembly, and secretion was 40-50 min for both control and stimulating conditions. This indicates that the increased production was due principally to the presence of greater amounts of fibrinogen mRNA rather than translation or secretion-specific events. Three lines of evidence indicate that the increase in fibrinogen production was due to HSF effects on transcription: (a) analysis of cytoplasmic levels of each of the fibrinogen mRNAs showed that all three increased at the same rate and to the same extent, demonstrating that HSF affects the three gene products coordinately; (b) Northern gel analysis of cytoplasmic RNA isolated after very brief exposures to HSF showed increases in a large molecular weight fibrinogen RNA precursor; and (c) actinomycin D blocked the HSF-stimulated increase in fibrinogen mRNA species. Furthermore, experiments in which protein synthesis was inhibited by cycloheximide failed to inhibit the increase in fibrinogen mRNAs, indicating new protein synthesis is not required for the HSF stimulation of fibrinogen mRNA. These results are consistent with our hypothesis that HSF is exerting its control of fibrinogen at the level of gene transcription.

Animals↗

PubMed1985

Pulmonary complications of hyperventilation therapy for persistent pulmonary hypertension.

Hyperventilation has become a primary therapeutic modality in the management of neonates with persistent pulmonary hypertension (PPH). Of 51 PPH infants undergoing hyperventilation therapy, 45% developed pneumothorax. The subgroup which developed pneumothorax was exposed to assisted ventilation for significantly longer time periods and at higher peak inspiratory pressures. They were also exposed to longer periods of oxygen therapy at higher oxygen concentrations. Survival in the pneumothorax group was significantly lower. The incidence of bronchopulmonary dysplasia (BPD) in the 35 survivors was only 6%. These data indicate that the use of hyperventilation to treat PPH is associated with a significant incidence of pneumothorax but a low incidence of BPD.

Bronchopulmonary Dysplasia↗

PubMed1985

The effect of posture on the lumbar spine.

A series of experiments showing how posture affects the lumbar spine is reviewed. Postures which flatten (that is, flex) the lumbar spine are compared with those that preserve the lumbar lordosis. Our review shows that flexed postures have several advantages: flexion improves the transport of metabolites in the intervertebral discs, reduces the stresses on the apophyseal joints and on the posterior half of the annulus fibrosus, and gives the spine a high compressive strength. Flexion also has disadvantages: it increases the stress on the anterior annulus and increases the hydrostatic pressure in the nucleus pulposus at low load levels. The disadvantages are not of much significance and we conclude that it is mechanically and nutritionally advantageous to flatten the lumbar spine when sitting and when lifting heavy weights.

Humans↗

PubMed1984

Rapid and sensitive determination of acetylsalicylic acid and its metabolites using reversed-phase high-performance liquid chromatography.

A rapid and sensitive high-performance liquid chromatographic technique was developed for the simultaneous determination of gentisic acid, salicyluric acid, acetylsalicylic acid and salicylic acid in plasma and serum. The method involved a single deproteinization step and separation using a reversed-phase column eluted with a buffered methanol (35%) mobile phase. Detection was achieved with a variable-wavelength ultraviolet detector set at 235 nm and a given chromatographic analysis could be completed in less than 10 min. The method was tested in both human and animal (rat) models given a single dose of acetylsalicylic acid.

Animals↗

PubMed1984

Persistent pulmonary hypertension of the newborn. Trends in incidence, diagnosis, and management.

Persistent pulmonary hypertension of the newborn ( PPHN ) has become a more commonly recognized problem in neonatal intensive care nurseries. In 62 neonates, 27 from 1980 and 35 from 1981, we compared classification, methods of diagnosis, modes of therapy, and survival. Thirty neonates (48%) had primary and 32 (52%) had secondary PPHN . Overall survival was 71% with significant differences in primary v secondary PPHN . Survival was also higher in 1981 than 1980 and was related to earlier diagnosis and to the more rapid initiation of therapy.

Humans↗

PubMed1984

Hemodynamic modification of aortic atherosclerosis. Effects of propranolol vs hydralazine in hypertensive hyperlipidemic rabbits.

According to hemodynamic theories of atherogenesis, atherosclerotic plaques are a reaction to endothelial damage caused by arterial flow disturbances such as turbulence. Earlier studies showed that hydralazine increased, whereas propranolol decreased, the product of heart rate X blood velocity, a predictor of arterial flow disturbances, and that hydralazine aggravated, whereas propranolol decreased turbulence in the region of carotid artery stenosis. This study was done to test the hypothesis that drugs which reduce arterial flow disturbances may be more effective in preventing atherosclerosis, than antihypertensive drugs which worsen arterial flow disturbances. Eighty-three New Zealand white rabbits were made hypertensive by a one-kidney Goldblatt procedure, and were fed a 1% cholesterol diet. Untreated hypertensive (P less than 0.01) and hydralazine-treated hypertensive rabbits (P less than 0.05) had significantly more atherosclerosis than did the normotensive controls; propranolol-treated rabbits did not differ significantly from the normotensive controls. Analysis of covariance showed that propranolol-treated rabbits had significantly less atherosclerosis than hydralazine-treated rabbits with blood pressure (P less than 0.04) or heart rate (P less than 0.006) as the covariates.

Animals↗

PubMed1984

Adrenal and urinary catecholamines during and after severe ethanol intoxication in rats: a profile of changes.

Adrenal and urinary levels of adrenaline and noradrenaline were determined in rats subjected to severe ethanol intoxication for periods of up to 96 hours, in rats undergoing withdrawal and in a post-withdrawal period, and in controls. Adrenaline and noradrenaline content of adrenal glands fell markedly to less than eight and twenty percent, respectively, after four days of intoxication. Noradrenaline content, but not adrenaline content, had recovered after a subsequent four day period of recovery. The depletion in adrenal catecholamine levels was coincident with increases in urinary adrenaline and noradrenaline levels over the first 48 hours of intoxication. Urinary catecholamine levels remained higher than control values for the next 48 hours of intoxication. Adrenal glands were larger after 12 hours of intoxication, although there was no increase in dry weight. At later times adrenal enlargement was associated with increased dry weight and protein content. This increase in mass was found to be of cortical origin. These results demonstrate that severe ethanol intoxication promotes an intense stimulation of the rat adrenal gland with enhanced synthesis and release of catecholamines, and cortical hypertrophy.

Adrenal Glands↗

PubMed1984

Disc space narrowing and the lumbar facet joints.

Cadaveric lumbar spine specimens of "motion segments", each including two vertebrae and the linking disc and facet joints, were compressed. The pressure across the facet joints was measured using interposed pressure-recording paper. This was repeated for 12 pairs of facet joints at four angles of posture and with three different disc heights. The results were that pressure between the facets increased significantly with narrowing of the disc space and with increasing angles of extension. Extra-articular impingement was found to be caused, or worsened, by disc space narrowing. Increased pressure or impingement may be a source of pain in patients with reduced disc spaces.

Adult↗

PubMed1983

Myocardial hypertrophy, cardiac and urinary catecholamines during severe ethanol intoxication and withdrawal.

Cardiomegaly was observed in rats severely intoxicated with ethanol for a 4 day period. It was apparent at 48 hours of treatment, a time at which cardiac protein was elevated and continued into withdrawal. During a 4 day abstinence period the degree of hypertrophy declined towards normal. Cardiac noradrenaline was reduced at the 48 hour time of intoxication, then increased gradually in the further experimental period. As the cardiac hypertrophy occurs at a time that urinary catecholamines are elevated and the adrenal medulla is intensely stimulated, it is proposed that increased levels of circulating catecholamines are largely responsible for the enlargement of the heart.

Adrenal Medulla↗

PubMed1983

Translational and cotranslational events in fibrinogen synthesis.

What we have shown in these studies are some of the first steps in the assembly of fibrinogen. We believe that using the hepatocyte culture system together with molecules capable of stimulating an increase in synthesis holds much promise in helping to learn how the cell puts together this elegant and complicated molecule. Moreover, these studies may also provide clues to mechanisms operant for other complex proteins produced by the liver.

Amino Acid Sequence↗

PubMed1983

The mechanical function of the lumbar apophyseal joints.

Experiments were carried out on cadaveric lumbar spines to determine the mechanical function of the apophyseal joints. It was found that they resist most of the intervertebral shear force and share in resisting the intervertebral compressive force, but only in lordotic postures. They prevent excessive movement from damaging the discs: the posterior annulus is protected in torsion by the facet surfaces and in flexion by the capsular ligaments.

Humans↗

PubMed1983

The effect of posture on the fluid content of lumbar intervertebral discs.

Cadaveric lumbar motion segments were creep loaded for 4 hours, and the fluid content of the intervertebral discs was measured and compared with that of unloaded discs. Half of the specimens were wedged to simulate sitting with the lumbar spine flexed, and the other half were wedged to simulate sitting or standing erect. The results showed that "flexed" discs lost more fluid, especially from the nucleus pulposus, than did the "erect" discs. It is concluded that fluid flow in flexed postures can aid the nutrition of the lumbar discs.

Adult↗

PubMed1983

The effect of fatigue on the lumbar intervertebral disc.

Forty-one cadaveric lumbar intervertebral joints from 18 spines were flexed and fatigue loaded to simulate a vigorous day's activity. The joints were then bisected and the discs examined. Twenty-three out of 41 of the discs showed distortions in the lamellae of the annulus fibrosus and, in a few of these, complete radial fissures were found in the posterior annulus.

Adolescent↗

PubMed1983

A computerized system for continuous physiologic data collection and analysis: initial report on mean arterial blood pressure in very low-birth-weight infants.

A system for continuous measurement and analysis of mean arterial blood pressure (MABP) by microcomputer is presented. The system allows prolonged recording and maintenance of fine detail by sequential evaluation and storage of up to 3,600 data points per hour. Fifteen preterm appropriate-for-gestational-age (AGA) infants weighing less than or equal to 1,500 g (very low birth weight) who were free of pulmonary and neurologic disease were monitored continuously from birth to 5 days of age. MABP was recorded via an umbilical arterial catheter with a pressure transducer and module interfaced with the microcomputer. Software was developed to analyze this stored data rapidly. MABP was found to correlate significantly with gestational age from 3 to 15 hours of age (P less than .05). Significant correlation was rare after 20 hours of age. MABP increased as a function of postnatal age in 11 infants. This increase was greater (0.31 to 0.54 mm Hg/h) for the least mature infants (27 to 29 weeks of gestation). The increase for the most mature infants (31 to 32 weeks of gestation) was low (0 to 0.24 mm Hg/h), and in three infants a small negative slope was seen. The steep rise in MABP during the first 40 hours of life in the least mature infants may be due to the perfusion requirements of extrauterine life. These pressures may be at or near the threshold for rupture of immature vascular beds such as are found in the subependymal germinal matrix and thus predispose to intraventricular hemorrhage.

Blood Pressure Determination↗

PubMed1982

The mechanics of prolapsed intervertebral disc.

Cadaveric lumbar intervertebral joints were subjected to compressive loads while wedged in forward flexion. In some specimens disc lesions were produced and we have been able to identify three different types: postero-lateral radial fissure, annular protrusion and nuclear extrusion. The type of lesion depended on the loading regime but all occurred more readily in slightly degenerated discs.

Adult↗