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Biomedical subjects

A M Robson

Publications and source records attributed to A M Robson.

At least 37 records · Page 2Linked to original sources
PubMed1985

Geographic access to health care services: the case of maintenance hemodialysis.

A longitudinal study of the system for delivering maintenance hemodialysis services in St Louis, Missouri was conducted to determine the significance of geographic access in the selection and continued utilization of a treatment facility. Historically, center hemodialysis patients in this metropolitan area received care at four centrally located facilities. In 1981, two new, independent facilities were constructed; a satellite of an existing unit was opened in 1983. The data obtained in this study demonstrated that end-stage renal disease (ESRD) patients generally did not change their mode of maintenance therapy, their treatment facility, or the location of their personal residence. When such changes occurred, they were rarely precipitated by a desire to reduce travel time to treatment. Furthermore, the opportunity to improve geographic access by transferring to a closer unit was perceived by patients to be viable only if they could retain their physician. It was concluded, therefore, that travel time to treatment is a relatively unimportant aspect of the chronic care of center hemodialysis patients in a metropolitan area.

Adult↗
PubMed1985

Does social support determine the treatment setting for hemodialysis patients?

The availability of an adequate system of social support has been suggested to be significant in determining whether an end-stage renal disease (ESRD) patient is dialyzed in a center or at home. To evaluate this hypothesis more completely, we conducted a study of social support among 257 home and center hemodialysis patients receiving maintenance therapy at four facilities in a midwestern, metropolitan area. A statistically significant difference, chi 2(3) = 14.031, P = 0.0029, was observed in the percentage of patients with social support available to them across the four facilities. The distribution of patients between home and center hemodialysis at the facilities also differed significantly, chi 2(3) = 14.919, P = 0.0019. An adequate social support system was present among 96.4% of the 55 home hemodialysis patients and 85.6% of the 202 center hemodialysis patients, a difference that was statistically significant, chi 2(1) = 4.684, P = 0.0305. However, a more detailed analysis of these findings revealed that the presence of social support was not significant, chi 2(1) = 1.080, P = 0.2995, in determining whether and ESRD patient was dialyzed at home or in a center after accounting for the facility differences. The facility differences remained significant in determining the setting of hemodialysis even after correcting for social support, chi 2(3) = 10.740, P = 0.0132. We concluded, therefore, that the attitudes of clinical staff toward home and center hemodialysis and the willingness of staff to develop those resources that facilitate a specific treatment setting are the principal elements in the therapy selection process.

Adult↗
PubMed1985

Urinary beta 2-microglobulin in full-term newborns: evidence for proximal tubular dysfunction in infants with meconium-stained amniotic fluid.

Urinary concentrations of beta 2-microglobulin (beta 2M) and creatinine were measured in normal term infants and in those born with meconium-stained amniotic fluid. None of the infants or their mothers had conditions known to modify beta 2M excretion. Measurements of beta 2M were made on urines collected by bagging; urines obtained from diapers were not satisfactory. Urinary beta 2M concentrations increased significantly (P less than .02) in the normal infants from the first day (0.36 +/- 0.29 mg/L: n = 29) to the third day (0.60 +/- 0.43 mg/L: n = 21) postpartum. Compared with the normal infants, values for the infants with meconium-stained amniotic fluid were increased significantly on days 1 (1.64 +/- 2.16 mg/L: n = 25: P less than .005) and 3 (2.12 +/- 2.04 mg/L: n = 23: P less than .005). Levels exceeded two standard deviations above the normal mean in 12 of the 26 infants with meconium-stained amniotic fluid on postpartum day 1, and 12 of the 23 infants with meconium-stained amniotic fluid on day 3. Urinary creatinine levels were similar in both the normal infants and those with meconium-stained amniotic fluid. All infants with meconium-stained amniotic fluid with a one-minute Apgar score of 6 or less had an elevated urinary beta 2M concentration. The elevated levels of urinary beta 2M in infants with meconium-stained amniotic fluid indicate the existence of tubular dysfunction, probably mild acute tubular necrosis secondary to hypoxia.

Amniotic Fluid↗
PubMed1984

The effects of polycations on vascular permeability in the rat. A proposed role for charge sites.

This study investigated whether charge sites in the walls of the microvasculature may play a role in maintaining the impermeability of the nonrenal capillaries to albumin. All experiments were performed in nephrectomized rats, studied in the awake state. The intravenous injection of protamine sulfate (4 mg/100 g body wt dissolved in 0.9% saline) was followed by a mean increase of 29.1% in hematocrit and a decrease of 28.4% in plasma albumin concentration over a 10-min period, indicating a significant 50-60% loss of albumin from the vascular space; a finding confirmed by studies using exogenous 125I-labeled albumin. Changes persisted for the remaining 80 min of observation, and could be reproduced by the injection of two other polycations, hexadimethrine and poly-l-lysine. These effects were not prevented by the antihistamine diphenhydramine hydrochloride. In contrast to 125I-labeled albumin, 14C-labeled neutral dextran of comparable size was not confined to the vascular space; its apparent volume of distribution progressively increased during the 90 min of observation. Intravenous injection of protamine sulfate was followed by a significantly smaller loss of 14C-dextran (36.5%) than albumin (59.1%) from the vascular space (P less than 0.01). Protamine sulfate could not be demonstrated to result in any changes in the physicochemical characteristics of albumin. These observations suggest that the negative charge sites present in nonglomerular capillary walls have functions similar to equivalent sites present in the glomerular capillaries. Thus, charge sites could contribute to the low permeability of the microvasculature to negatively charged macromolecules such as albumin. This may be an important mechanism for retaining albumin in the vascular space and preventing edema formation in health.

Animals↗
PubMed1983

Sensitive and specific radioenzymatic assay for norepinephrine, epinephrine and dopamine based on the thin-layer chromatographic separation of their Dns-O-methyl derivatives.

A radioenzymatic assay is described in which norepinephrine, epinephrine and dopamine are converted to their tritiated 3-O-methyl derivatives by reaction with S-[methyl-3H]adenosyl-L-methionine in the presence of catechol-O-methyltransferase. The methylated compounds are then reacted with Dns chloride, and the Dns derivatives are extracted into ethyl acetate, isolated by thin-layer chromatography and quantified by liquid scintillation spectrometry. The assay displays a high degree of specificity for each compound, due in large part to the chromatographic properties of the Dns derivatives. It is capable of measuring 2 pg of each catecholamine, and is linear to at least 5 ng. Approximately 50 samples can be assayed in 1.5 days.

Animals↗
PubMed1983

Amphetamine-stimulated release of endogenous dopamine from the rat caudate nucleus in vivo.

The in vivo release of endogenous dopamine (DA) has been measured from the rat caudate nucleus. A push-pull cannula was implanted into the brain and the tissue was perfused with artificial cerebrospinal fluid (CSF) containing amphetamine in concentrations ranging from 5 X 10(-3) to 5 X 10(-7) M. The DA released into the perfusate was determined by a radioenzymatic procedure. DA release was increased to levels significantly above its resting rate by amphetamine concentrations of 5 X 10(-6) M or greater. Release stimulated by 5 X 10(-5) M amphetamine was significantly reduced by removing calcium from the perfusing fluid; the unstimulated release rate was not significantly affected. The concentrations of amphetamine required to increase DA release in vivo would appear to be similar to those found in the brain following intraperitoneal doses which produce increases in locomotor activity and stereotyped behavior.

Animals↗
PubMed1983

In vivo release of endogenous dopamine from rat caudate nucleus by phenylethylamine.

The in vivo release of endogenous dopamine (DA) from the rat caudate nucleus has been measured in the presence and absence of beta-phenylethylamine. A push-pull cannula was implanted into the brain and the tissue was perfused with artificial cerebrospinal fluid (CSF) containing phenylethylamine in concentrations ranging from 5 X 10(-3) to 5 X 10(-7) M. The DA released into the perfusate was determined radioenzymatically. Dopamine was released at rates significantly greater than its resting rate by concentrations of phenylethylamine of 5 X 10(-3) to 5 X 10(-5)M; 5 X 10(-6)M phenylethylamine caused a slight increase in release, but the difference from the resting rate was not significant. The absence of calcium in the perfusing medium did not significantly alter either the unstimulated release rate of DA or the release rate stimulated by 5 X 10(-5)M phenylethylamine. The concentrations of phenylethylamine required to increase release of DA in vivo are discussed briefly in relation to the doses required to elicit behavioural effects.

Animals↗
PubMed1983

Treatment bias in the management of end-stage renal disease.

A study was conducted of 419 patients with end-stage renal disease (ESRD) being treated by center or home hemodialysis or by renal transplantation at four facilities located within 2.5 km of each other. The objectives were to examine the distribution of patients among the three modes of treatment and to analyze patient transfers to alternate modes of ESRD therapy. While white patients at each facility were comparable (P greater than 0.05) on age, sex, travel time to treatment, marital status, work or employment status, and the presence of diabetes mellitus, the distribution of patients among the treatment modes differed significantly (P less than 0.001) across the facilities. Similarly, the sociodemographic and diagnostic characteristics of the nonwhite patients were comparable at each of the facilities (P greater than 0.05); however, despite observable variation among the facilities in the distribution of these patients, the differences did not achieve statistical significance (P greater than 0.05). Patient transfers to alternate modes of ESRD therapy were infrequent, and among center hemodialysis patients, the distribution of transfers differed significantly across the facilities (P less than 0.001). It is concluded that the distribution of patients was dependent on the patient's initial mode of therapy and the staff attitudes at the individual facilities.

Adult↗
PubMed1983

Cerebral cortical atrophy in pediatric patients with end-stage renal disease.

Computed tomography of the head in 15 children with end-stage renal disease revealed cerebral cortical atrophy in eight and ventricular enlargement in an additional two. These changes were not necessarily associated with any clinical signs or symptoms. Although high doses of steroids may have been responsible for some of the lesions, alternate etiologies are required to explain the abnormality in others cases. The mean length of time the patients received chronic hemodialysis was twice as long in patients with atrophy as in those with normal scans. However, possible causative factor/s related to dialysis could not be identified. The high incidence of cerebral atrophy is cause for concern and indicates the need for further study of this phenomenon.

Adolescent↗
PubMed1983

The quality of maintenance therapy for end-stage renal disease. A review of social adjustment and rehabilitation.

Prior to 1972, ESRD patients selected for maintenance dialysis or renal transplantation were generally young, emotionally and socially well-adjusted, and physically healthy except for their renal disease. Following the enactment of Public Law 92-603 (1972), which extended Medicare coverage to virtually all ESRD patients, the criteria for the selection of patients were substantially liberalized. During the past decade, maintenance therapy has increasingly been provided for severely debilitated ESRD patients whose reported levels of rehabilitation have been less than desired. While the majority of the current ESRD patient population have not been restored to their premorbid levels of individual and social functioning, recent studies suggest this may be the result of initiating rehabilitation efforts too late in the disease process. For optimal social functioning to be achieved by ESRD patients, it is concluded that psychosocial intervention and support must be initiated at the time ESRD is diagnosed and be focused on the maintenance, rather than rehabilitation, of the patient's functioning.

Humans↗
PubMed1982

Pulse methylprednisolone therapy in diffuse proliferative lupus nephritis.

The prognosis of patients with diffuse proliferative lupus nephritis is generally poor, and the majority of patients with this lesion develop progressive deterioration in renal function. Intravenous "pulses" of methylprednisolone have been advocated for the treatment of severe nephritis. In this study, 15 patients with biopsy-proven diffuse proliferative lupus nephritis were treated with oral high-dose prednisone therapy, initially 2 mg/kg/day. They were compared with seven patients with similar renal pathology treated with six daily pulses of methylprednisolone (30 mg/kg/day, not to exceed 1 gm/day), followed by prednisone orally, initially 2 mg/kg/day. There were no deaths in either group and the side effects of therapy were similar in the two groups. Pretreatment GFRs for the pulse and high-dose groups were similar. There was a more rapid improvement in GFR following pulse therapy, but the long-term effects on renal function for the two modes of therapy were the same.

Administration, Oral↗
PubMed1982

Glomerular charge and urinary protein excretion: effects of systemic and intrarenal polycation infusion in the rat.

To study the role of the fixed anionic sites of the glomerular capillary wall in protein filtration, the negative charges were neutralized in vivo. With systemic infusion of the polycation protamine sulfate, glomerular staining for polyanion was reduced and protein excretion increased by 154%. To avoid systemic side effects in subsequent studies, small doses of a polycation were infused directly into one renal artery. The contralateral kidney was infused with the vehicle solution. Albumin excretion from the experimental kidneys in the first 1-hr collection after infusing 0.5 mg protamine sulfate was 24.3 +/- 6.3 micrograms/min/kidney (N = 13; P less than 0.01). Albuminuria declined during the subsequent 3 hr with a second infusion inducing a second proteinuric response. The degree and longevity of the albuminuric response was correlated directly to the dose of protamine sulfate. The polycations hexadimethrine and poly-l-lysine also induced proteinuria. The increased protein excretion consisted of albumin; the excretion of nonalbumin protein was identical in the experimental and control kidneys. Hemodynamic factors did not explain the increase in proteinuria. Morphologically, the polycation-treated kidneys showed scanty foot process fusion and a decrease in free negative sites in the lamina rarae of the glomerular basement membrane. The results strongly support an important role for glomerular charge in preventing filtration of circulating plasma albumin.

Albuminuria↗
PubMed1982

Unstimulated and amphetamine-stimulated release of endogenous noradrenaline and dopamine from rat brain in vivo.

The in vivo release rates of endogenous noradrenaline from the hypothalamus and dopamine from the caudate nucleus of the rat have been determined. Artificial CSF perfusates collected from a push-pull cannula inserted into specific areas of the brain were assayed for the amines by a sensitive radioenzymatic procedure. The release rates of noradrenaline and dopamine into artificial CSF perfusates were 38 +/- 6 and 46 +/- 6 pg/h (225 +/- 36 and 301 +/- 39 fmol/h), respectively; when 0.5 mM amphetamine was added to the CSF, the release rates of noradrenaline and dopamine increased to 176 +/- 50 and 1183 +/- 453 ph/h (1041 +/- 296 and 7732 +/- 2961 fmol/h), respectively.

Animals↗
PubMed1981

The treatment of severe glomerulopathies in children using high dose intravenous methylprednisolone pulses.

Thirty-five patients, 29 with severe proliferative glomerulonephritis and six with either steroid resistant or steroid dependent nephrotic syndrome, were treated with high dose bolus infusions of methylprednisolone (pulses) followed by prednisone given orally in more conventional doses for 6 mo or longer. Twenty-one of the 29 patients with severe proliferative glomerulonephritis had sustained improvement in renal function after treatment. In addition, pulse treatments reduced proteinuria and urine sediment abnormalities in these patients. Those who did not respond had a long duration of disease before receiving pulse therapy. Five of six patients with the nephrotic syndrome had reduction in proteinuria and three of these patients entered prolonged remission after treatment. Few side effects occurred with pulse therapy. Our observations suggest that the use of steroid pulses may limit or prevent long-term major loss of renal function in many patients with severe proliferative glomerulonephritis. It may be effective also in treatment of some patients with steroid refractory or frequently relapsing nephrotic syndrome. This therapeutic approach deserves continuing evaluation.

Adolescent↗
PubMed1981

Maturation of the developing rabbit kidney: variations in cellular size and contents.

Because the rabbit kidney is being used as an experimental model with increasing frequency, this study was designed to measure the relationships between cell number, size, and contents in the developing rabbit. Kidney slice extracellular and intracellular fluid spaces, high in the fetus and neonate, declined as the rabbits matured, being parallel by changes in body fluid spaces. Although the cellular contents of both sodium and potassium were increased in the young kidney, intracellular sodium concentration was slightly lower in the fetal (43.6 mEq/liter) and 2-wk kidneys (44.5 mEq/liter) than in the mature kidney (51.7 mEq/liter). Intracellular potassium concentrations were similar in all age groups (163 to 167 mEq/liter). Tissue protein content was similar during development. In contrast, DNA content and the number of nuclei in kidney tissue were high in the fetus (DNA, 59.9 mg/g solids; nuclei, 3.9 x 10(9)/g solids), decreasing in postnatal life (DNA in adult, 18.2 mg/g solids; nuclei in adult, 1.0 x 10(9)/g solids). In association with this, the diameter of proximal tubular cells increased with maturation. These data should be valuable to those interested in kidney development.

Animals↗