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Biomedical subjects

A M Martin

Publications and source records attributed to A M Martin.

At least 73 records · Page 4Linked to original sources
PubMed1988

Abnormal differentiation of immunoregulatory T-lymphocyte subpopulations in the major histocompatibility complex (MHC) class II antigen deficiency syndrome.

The major histocompatibility complex (MHC) class II deficiency syndrome is a rare immunodeficiency disease associated with defective expression of class II MHC antigens. We have examined the consequences of this defect for the differentiation and functional capabilities of immunoregulatory T-cell subpopulations in an affected patient. Although the number of circulating T cells was normal, there was a striking reduction in the number of CD4+ T cells. Furthermore, purified CD4+ cells from the patient were unable to provide help for antibody secretion. This defect in helper function appeared to be due to the abnormal differentiation of the few CD4+ cells present, virtually all of which expressed the CD4+HB11+ phenotype characteristic of immature "virgin" T cells. Abnormal development of immunoregulatory CD8+ T cells was also observed. Although increased numbers of CD8+ T cells were present, virtually none had phenotypic properties of suppressor cells (i.e., CD3+/CD8+/9.3- granular lymphocytes that coexpress the Leu-15 or Leu-7 antigens), and purified CD8+ cells from the patient had no suppressor activity. Thus, the absence of class II MHC antigens profoundly disrupts the development of immunoregulatory T cells. We propose that these effects occur by the following mechanisms: (1) the absence of intrathymic class II antigens results in deficient production of CD4+ cells, (2) the CD4+ cells that do emerge from the thymus do not undergo postthymic maturation into CD4+HB11- cells with helper capabilities, and (3) the absence of CD4+HB11- effector cells results in abortive development of suppressor cells involved in feedback suppression.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Bare lymphocyte syndrome. Consequences of absent class II major histocompatibility antigen expression for B lymphocyte differentiation and function.

The bare lymphocyte syndrome is a rare combined immunodeficiency disorder associated with the absence of class I and/or class II major histocompatibility (MHC) antigens. Although it has been inferred that the immune deficiency is a consequence of disordered MHC-restricted interactions among otherwise normal cells, the biological capabilities and differentiation of B lymphocytes deficient in class II MHC antigens have not been rigorously analyzed. We have examined the phenotypic and functional attributes of B cells with absent class II MHC antigens. Our data demonstrate that these B cells are intrinsically defective in their responses to membrane-mediated activation stimuli. In addition, virtually all the B cells had phenotypic evidence of arrested differentiation at an immature stage. Finally, these B cells also failed to express the C3d-EBV receptor normally present on all B lymphocytes. These data indicate that class II MHC molecules are vital participants in early events of the B cell activation cascade, and that other non-MHC membrane molecules may also be absent as a consequence of either arrested differentiation or as a result of the basic defect affecting the expression of MHC membrane antigens.

Antibody-Producing Cells↗
PubMed1987

The effect of raised intracranial pressure on intracochlear fluid pressure: three case studies.

The effects of changes in intracranial fluid pressure (ICP) on cochlear fluid pressure have been studied in 3 patients who underwent ventriculo/lumbar-peritoneal shunt operations. The operations were performed in order to alleviate problems caused by an abnormally raised ICP. Indirect measurements of perilymphatic pressure were made before and after surgery using a non-invasive technique which measures tympanic membrane displacement. This technique proved extremely sensitive and revealed changes in cochlear fluid pressure brought about by changes in the ICP. The results emphasise the need to consider audiological measurements in the context of ICP abnormalities. These findings have important implications in that an audiological technique may be used for the simple and non-invasive serial monitoring of changes in ICP and may even assist differential diagnosis in a number of neurological patients.

Adolescent↗
PubMed1986

Dietary evaluation of outpatients with chronic obstructive pulmonary disease.

Protein-calorie malnutrition is prevalent among individuals with chronic obstructive pulmonary disease (COPD), and suboptimal body weight has been associated with increased morbidity and mortality. Pulmonary function, anthropometric measurements, and dietary intake were evaluated in 64 outpatients with stable COPD to assess interrelationships of those parameters. Those individuals with body weights less than 75% of standard for height, age, and sex had the greatest degree of airway obstruction, poorest lung diffusing capacity, and greatest loss of body fat and muscle mass. Contrary to what had been anticipated, calorie and protein intake levels were highest in the less than 75% of standard body weight group, decreased as relative body weight increased, and were lowest in the greater than 105% of standard body weight group. Those results indicate that caloric needs increase as COPD progresses. Intake levels of calcium, phosphorus, iron, vitamin A, thiamin, riboflavin, niacin, and vitamin C were adequate in terms of the RDAs and were not related to relative body weight.

Anthropometry↗
PubMed1985

Increased digitalis-like activity in human cerebrospinal fluid after expansion of the extracellular fluid volume.

The present study was designed to determine whether acute expansion of the extracellular fluid volume influenced the digitalis-like activity of human cerebrospinal fluid (CSF), previously described by our laboratory. Human CSF samples, drawn before and 30 minutes after the intravenous infusion of 1 liter of either saline or glucose solutions, were assayed for digitalis-like activity by inhibition of either the 86Rb+ uptake into human erythrocytes or by the activity of a purified Na+ - K+ ATPase. The CSF inhibitory activity on both systems significantly increased after the infusion of sodium solutions but did not change after the infusion of glucose. These results indicate that the digitalis-like factor of human CSF might be involved in the regulation of the extracellular fluid volume and electrolyte content and thereby in some of the physiological responses to sodium loading.

Calcium↗
PubMed1985

Growth of Agaricus campestris NRRL 2334 in the Form of Pellets.

The production of pellets of the fungus Agaricus campestris NRRL 2334 was studied in submerged fermentation with peat extract as the main substrate source. Pellets up to 6 mm in diameter were obtained when the peat extract was diluted to reduce the concentration of growth inhibitors. Yeast extract and yeast extract plus glucose were the most effective nutrient supplements in the diluted peat extract media and stimulated the formation of large pellets which contained 44.4% crude protein, 2.8% fat, and 9% ash (dry weight basis). No solid supports were required for the growth of the pellets. The effects on the growth morphology of several dilution ratios of the peat extract, rates of agitation and aeration, and time were investigated.

Journal Article↗
PubMed1985

A computer-based test system for implementing pure-tone audiometry, acoustic immittance and tympanic membrane displacement measurements.

Valuable information on functional features of the auditory system may be gained by measuring the fine structure and time course of the acoustic stapedial reflex. This type of measurement invariable needs a computer for averaging the reflex response and the analysis of its salient features. This paper describes a 'Computerised Audiometric System' (CAS) which allows an integrated approach to certain audiometric tests, including pure-tone audiometry and tympanometry. In particular, 'tympanic membrane displacement' and acoustic immittance measurements have been combined to allow a comprehensive study of the reflex characteristics to be made. The purpose of this paper is twofold; first to describe the CAS in respect of reflex measurements; secondly, to describe the design of a practical computerised audiometric system which may be used for a wide variety of clinical testing and research. Features of special mention are the modular design strategy used, which makes the system an extremely versatile research tool as well as a potentially valuable addition to the audiology clinic, and menu-driven software written in FORTH, which allows complex test paradigms to be learnt and reliably implemented with a minimum of training. The prototype facility has been used extensively for research over the past 18 months, and a second is now installed in the Wessex Regional Audiology Centre. Both facilities will be linked to a patient data bank now under development.

Acoustic Impedance Tests↗
PubMed1984

Bone disease in long-term hemodialysis patients with low dialysate aluminium.

The dialysis unit in Sunderland uses softener water treatment with low Al concentration (dialysate mean Al 22 micrograms/L) but employs continuous oral Al (OH)3 to control serum phosphate. Thirty-one patients, 22 males and 9 females, with a mean age of 45 years, maintained on hemodialysis for a mean of 48 months were studied. Patients had higher Al concentrations than normal controls (p less than 0.001) and the postdialysis serum Al levels were also significantly higher than the predialysis levels. Twenty-four of 31 patients had evidence of hyperparathyroidism on radiology but only 4 of 31 had fractures. From a histopathological point of view, the patients were found to have no lesions (4 patients), osteitis fibrosa alone (17 patients), and osteitis fibrosa combined with osteomalacia (5 patients). The effect of 1-alpha(OH)D3 treatment was checked by repeated bone biopsies. One case of the last group showed no improvement of osteitis fibrosa, while osteomalacia progressed to severe. We conclude that both antacids and dialysate contribute to the serum and tissue Al accumulation in Sunderland Renal Unit, where over a period of ten years only one patient developed Al-related osteomalacia.

Adult↗
PubMed1983

Wound treatment with Sorbsan--an alginate fibre dressing.

This highly absorbent, biodegradable dressing derived from seaweed can be successfully applied to cleanse a wide variety of secreting lesions. The high absorption of exudate is achieved via strong hydrophilic gel formation and this serves to control wound secretion levels and to minimize bacterial contamination. Alginate fibres trapped in a wound are readily biodegraded and do not have to be removed thus avoiding disturbance of granulation tissue formation. Additional features are odour remission, conformability and ready removal of tissue adherent material.

Alginates↗
PubMed1982

Responses to ergometer exercise in a healthy biracial population of children.

To determine normal values for the exercise variables heart rate, blood pressure, maximal workload, physical working capacity index, J point displacement, and ST segment slope, we stress tested 405 healthy children. We analyzed the data for four body surface area-determined groups, to discover whether there were any racial differences between healthy white children and black children. There were numerous racial differences in blood pressure, maximal workload, and physical working capacity index; there were no differences in the heart rate values. The incidence of false-positive J point displacement was less than or equal to 3% when the PR isoelectric line method was used. The ST segment slope in healthy children was always greater than zero at maximal exercise. Thus, norms for exercise variables must be expressed in relation to both sex and race. The nomograms presented in this report provide an easy-to-use set of normative data for cycle ergometer stress testing in children.

Adolescent↗
PubMed1981

Blood pressure response to dynamic exercise in healthy children--black vs white.

In order to determine normal values for systolic blood pressure response to cycle ergometer stress testing in children, we performed 405 studies in subjects from 6 to 15 years of age, of whom 184 were black and 221 were white. We analyzed the data in relation to sex, color, age, and body surface area. Resting systolic blood pressure showed no differences between groups of black and white children, analyzed either by age or surface area. Peak exercise blood pressures were higher in the black females, in comparison to their white counterparts, only when separated into groups by body surface area. The black males had higher exercise blood pressure values than the whites, both by age and surface area evaluation. Our data suggest a difference in the blood pressure response to dynamic exercise within the black population. Further studies are needed to define the mechanism of this difference and whether this difference may provide a clue to the identification of children at increased risk for developing hypertension later in life.

Adolescent↗
PubMed1981

The effect of hearing protectors on the attention demand of warning sounds.

A reason often given by noise-exposed workers for not wearing their hearing protection is that it impairs their ability to hear important sounds such as acoustic warning signals. An experiment was therefore conducted to assess the possible effect of wearing hearing protection on the attention demand of a typical industrial warning sound. Inattention was created by providing uncertainty as to the time occurrence of the signal, and a separate loading task. The results indicate that neither inattention, nor the combination of inattention and the wearing of hearing protection, need necessarily impair the perception of a warning sound. The experiment therefore found no basis for the attitude that hearing protectors impair the effectiveness of warning sounds. This conclusion may not however apply to warning sounds which are not distinct from the ambient noise, those which have to be recognized amongst other discrete sounds, or to users of hearing protection with an existing noise-induced hearing loss.

Adult↗