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Biomedical subjects

J Smith

Publications and source records attributed to J Smith.

At least 1,225 records · Page 68Linked to original sources
PubMed1982

Human newborns are deficient in natural killer activity.

The peripheral blood natural killer (NK) activity of newborns was found to be significantly less than that of adults. In mixing experiments newborn cells inhibited adult NK activity in only one of nine instances. Interferon treatment in vitro increased newborn NK activity to an even greater degree than adult NK activity. These findings imply that diminished newborn NK activity is due not to inhibitory cells or lack of pre-NK cells but rather to deficient in vivo activation of pre-NK cells. This deficiency may be a major factor in the increased susceptibility of newborns to certain virus infections.

Adult↗
PubMed1982

Radiation-induced sarcoma of bone: clinical and radiographic findings in 43 patients irradiated for soft tissue neoplasms.

Sarcomas rarely follow irradiation of benign lesions of bone as the dangers of this form of therapy is well recognised. Forty-three patients with soft tissue neoplasms - mainly carcinoma - were irradiated and developed sarcomas in the radiation field. Twenty-four of these patients were seen at this centre in the last decade, a considerable increase compared to earlier years. Radiation osteitis may indicate the nature of the tumour but was only present in 50%. A purely lytic or purely sclerotic pattern was commoner than a mixed lytic and sclerotic appearance. CT scan, bone scan and angiography were helpful in delineating disease but did not assist in diagnosing the type of tumour. A tumour arising within the irradiated field is an indication for biopsy. Prognosis of radiation-induced sarcoma (RIS) remains poor, only five of the 43 patients survived 5 years.

Adolescent↗
PubMed1982

Migration and differentiation of neural crest cells and their derivatives: in vivo and in vitro studies on the early development of the avian peripheral nervous system.

After a period of extensive migration through the vertebrate embryo, neural crest cells differentiate into a great variety of cell types, including all the elements of the peripheral nervous system. We have studied crest cell migration in quail-chick chimeras in which quail cells can be identified by means of a stable natural nuclear marker. The results of interspecific grafts of neural primordium, performed systematically at different levels of the neuraxis, have established the sites of origin of the principal peripheral ganglia. In addition, they suggest that the cholinergic and adrenergic phenotypes are not predetermined in the neural crest before migration, but are the result of multiple cellular interactions. Furthermore, the phenotype expression of young differentiating autonomic ganglia is labile and can be modified if the latter are subjected to an appropriate cellular environment by grafting into a younger host embryo. The results of experiments in which fragments of neural crest, sensory and autonomic ganglia were transplanted are presented in terms of a model of crest cell-line segregation. As a step towards the analysis of the cellular interactions occurring during autonomic neuron differentiation, we have also studied neuronal development in tissue cultures of neural crest, taken from the cranial and trunk levels of quail embryos and grown in the presence or absence of other embryonic tissues. The results confirm that both levels of the crest are potentially able to give rise to cells that can make acetylcholine and catecholamines. However, whereas acetylcholine-synthesizing ability is apparently a very early feature of autonomic neuron precursors, the ability to produce catecholamines is acquired later as a result of interactions with other cell types, in particular with mesenchymal derivatives. Although production of both neurotransmitters can be considerably stimulated by associating crest with any of several young embryonic rudiments, only when trunk crest is cultured with the sclerotomal moiety of the somite is biochemical differentiation accompanied by extensive morphological and cytochemical neuronal maturation.

Acetylcholine↗
PubMed1982

Enteral hyperalimentation in undernourished patients with cirrhosis and ascites.

Available enteral hyperalimentation solutions used to treat undernourished cirrhotic, ascitic patients with protein intolerance are excessive in water, sodium, and in some cases protein. This study investigated the use of enteral formulae tailored to the water, sodium, and protein tolerance of 10 undernourished subjects with ascites due to alcoholic liver disease (n = 8) and postnecrotic cirrhosis (n = 2). During a 10- to 60-day (mean +/- 80 = 37 +/- 19) hyperalimentation period, three subjects were treated with a low Na (1g Na/2000 kcal), high caloric density formula (2 kcal/ml); previous encephalopathy in seven remaining subjects required infusion of a low Na, low protein (40 g/day) modular high caloric density formula. The high caloric density formula protein content in 6/7 subjects was increased to 80 to 143 g without adverse effect. Nine subjects tolerated the program well and showed improvement in the following indices: serum albumin, creatinine/height, and midarm muscle and fat areas. In selected cases, enteral hyperalimentation solutions with appropriate composition can be safely and effectively administered to cachectic cirrhotic subjects with ascites.

Adult↗
PubMed1982

Biochemical composition of muscle in normal and semistarved human subjects: relevance to anthropometric measurements.

Anthropometric methods aimed at assessing muscle size in undernourished subjects assume a constant proportionality between the mass (i.e., size) and composition (specifically protein-energy content) of this tissue. This assumption was examined in three autopsy groups: controls (n = 11, sudden traumatic death), early semistarvation (n = 6), acute preterminal disease), and chronic semistarvation (n = 34, severe weight loss over time). Results of semistarved groups were expressed relative to respective control value. Early semistarvation produced no detectable change in muscle mass, protein, or total energy content (per gram wet weight), although RNA and glycogen were -50 to -70% of control value (p less than 0.05). Chronic semistarvation caused muscle atrophy (-54.2%), but not all measured constituents were reduced to the same degree. The results were H2O--52.9%, collagen--46%, noncollagen proteins--65.3%, total lipids--40%, DNA--54.1%, RNA--81.7%, glycogen--90.3%, and total energy--59.6%. Muscle per unit mass in chronic semistarvation thus reflects relatively more H2O and less protein and energy when compared to normal tissue. About 85 to 95% of muscle protein-energy loss can be detected by anthropometric measurements of muscle size; the remaining 5 to 15% depletion of protein and energy is masked by muscle compositional changes. Proper interpretation of anthropometric data requires an understanding of these unmeasured but important compositional differences in normal and semistarved muscle.

Anthropometry↗
PubMed1982

Anthropometric measurement of muscle mass: revised equations for calculating bone-free arm muscle area.

Arm muscle area (AMA, cm2) is currently calculated from triceps skinfold thickness (TSF, cm), and midarm circumference (MAC, cm). In assessing the accuracy of the current equation by comparison to AMA measured by computerized axial tomography, error in each of the four approximations made was found to result in a 20 to 25% overestimate of AMA. Two correctible error sources were: a 10 to 15% overestimation caused by assuming a circular midarm muscle compartment and a 5 to 10% overestimation due to inclusion of midarm cross-sectional bone area. Corrected AMA equations for men and women were respectively: [(MAC - pi x TSF)2/4 pi] - 10, and [MAC - pi x TSF)2/4 pip] - 6.5. With two additional study groups, the overall improved accuracy of the new equations was confirmed, although the average error for a given patient was 7 to 8%; the relationship between corrected AMA and total body muscle mass was established [muscle mass (kg) = (ht, cm2) (0.0264 + 0.0029 x corrected AMA)]; and the minimal range of corrected AMA values compatible with survival (9 to 11 cm2) was defined. Bedside estimates of undernutrition severity and prognosis can therefore be calculated from two simple measurements, TSF and MAC.

Adult↗
PubMed1982

Impaired clot retraction in thrombocytopenia due to methyldopa.

We have described a case of thrombocytopenic purpura caused by methyldopa. A methyldopa-dependent antiplatelet antibody as the mechanism of the patient's thrombopenia was suggested by a positive clot retraction inhibition test. This simple in vitro test should be done more often in suspected cases of drug-induced thrombocytopenia.

Clot Retraction↗
PubMed1982

Neural-tube defect risk assessment for individual pregnancies using alphafetoprotein and acetylcholinesterase test results.

Pregnancies at risk of being associated with (open) neural tube defects can be identified by maternal serum and amniotic-fluid alphafetoprotein (AFP) concentrations in excess of established screening cut-off valves in conjunction with the results of an amniotic fluid electrophoretic acetylcholinesterase screening test. The risk associated with the AFP cut-off values are formulated in terms of a population screening programme. These "population risks" are of little value in the assessment of test results from individual "at-risk" pregnancies, especially when the observed AFP concentrations are in proximity to the "cut-off" values. A complete risk assessment procedure for individual pregnancies is described and presented in graphical form to permit immediate access by clinical staff.

Acetylcholinesterase↗
PubMed1982

Radiographic changes in primary osteogenic sarcoma following intensive chemotherapy. Radiological-pathological correlation in 63 patients.

Sixty-three patients with osteogenic sarcoma of the long bones, all of whom were treated with chemotherapy, demonstrated striking and unusual radiographic changes. Patients with a "good" radiographic response (48%) showed the most dramatic changes, including medullary sclerosis, prominent periosteal new bone formation, and disappearance of the soft-tissue mass; and these findings correlated well with the histological grading of the surgical specimens. Radiographic evaluation of patients receiving chemotherapy for osteogenic sarcoma is a valuable method of assessing response.

Adolescent↗
PubMed1982

Effect of parathyroid hormone on osmotic fragility of human erythrocytes.

The survival of erythrocytes (RBC) is shortened in uremia, and it has been shown that calcium influx into RBC evoked crenation and increased their rigidity. The high blood levels of parathyroid hormone (PTH) may augment entry of calcium into RBC and hence affect their integrity. We examined the effect of PTH on osmotic fragility of human RBC and investigated the mechanisms through which PTH interacts with RBC. Both the amino-terminal (1-34) PTH and the intact (1-84) PTH, but not the carboxy-terminal (53-84) PTH, produced significant increases in osmotic fragility. This effect was abolished by prior inactivation of the hormone. There was a dose-response relationship between both moieties of PTH and the increase in osmotic fragility. This action of PTH required calcium, was mimicked by calcium ionophore, and was partially blocked by verapamil. PTH caused significant influx of (45)Ca into RBC, which was not associated with potassium leak. The hormone did not affect water content of RBC. Scanning electron microscopy revealed that the incubation of RBC with PTH was associated with the appearance of membrane filamentous extensions, which anchor RBC together. Inhibition of glycolytic activity of RBC with NaF or inhibition of Na-K-activated ATPase with ouabain did not abolish the effect of PTH on osmotic fragility. PTH did not stimulate RBC Na-K-activated ATPase or Mg-dependent ATPase but caused marked and significant stimulation of Ca-activated ATPase. The basal activity of the RBC adenylate cyclase was low and PTH produced only a modest stimulation of this enzyme. Both cyclic AMP and dibutyryl cyclic AMP had no effect on osmotic fragility. THE DATA INDICATE THAT: (a) the RBC is a target organ for PTH, (b) the hormone increases osmotic fragility of RBC, and (c) this effect of PTH is due to enhanced calcium entry into RBC. We suggest that the increased calcium influx may affect the spectrin-actin of the cytoskeletal network of the RBC and may alter the stability and integrity of the cell membrane. This action of PTH on the RBC could be, at least in part, responsible for the shortened survival of RBC in uremia, and assign a new role for PTH in the pathogenesis of the anemia of uremia.

Adenosine Triphosphatases↗
PubMed1982

Vietnam veterans and posttraumatic stress disorder.

As many as four million Americans were stationed in Indochina during the Vietnam War; some 800,000 were assigned to the combat zone. These individuals are at especially high risk for developing posttraumatic stress disorder, a diagnostic category that appeared for the first time in DSM-III. The authors explore the reasons why many Vietnam veterans have developed the disorder. They discuss four broad types of disorders now being found among veterans, the problems in diagnosing and treating the disorder, and the theoretical basis in ego psychology for the behavior of veterans with the disorder. Also briefly outlined are some clinical considerations for therapists treating Vietnam veterans.

Combat Disorders↗