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Biomedical subjects

J C Leonard

Publications and source records attributed to J C Leonard.

At least 73 records · Page 4Linked to original sources
PubMed1984

Unique aspects of human newborn cerebral metabolism evaluated with phosphorus nuclear magnetic resonance spectroscopy.

In vivo phosphorus nuclear magnetic resonance spectroscopy (31P NMR) was used to evaluate the pattern of phosphate compounds in seven newborn babies (mean gestational age, 32 weeks; birth weight, 1,430 gm; age, 37 days) with a history of perinatal asphyxia. Spectra were collected in a 1.9 Tesla superconductive magnet with surface coil techniques. The spectra had characteristic peaks for phosphorylated monoesters (PME), inorganic phosphate (Pi), phosphodiesters (PD), phosphocreatine (PCr), and ATP. In contrast to cortical spectra from mature animals, these newborn infant 31P NMR spectra were dominated by a large PME peak and had small PCr, Pi, and PD peaks. Intracellular pH, as measured from the chemical shift of the Pi peak relative to the PCr peak, was 7.1 +/- 0.1 (SD). We studied one infant postmortem, and a large PME peak was present in his spectrum. The presence of PME 3 hours after death strongly suggests that it is not a sugar phosphate. In NMR spectroscopy, compounds are identified by their chemical shift relative to a known standard (PCr); the chemical shift of the PME peak was 6.5 ppm, suggesting that it is a mixture of phosphoryl ethanolamine and phosphoryl choline. The PCr/Pi ratio (1.3 +/- 0.7) and the PCr/ATP ratio (0.7 +/- 0.4) were lower in these babies than in mature animals (greater than 2 and greater than 1.4, respectively); the PME/PD ratio (1.2 +/- 0.6), however, was much greater in the infants (mature animals, less than 0.2). These findings suggest that there are unique aspects of human newborn cerebral metabolites and bioenergetic reserve.

Adenosine Diphosphate↗
PubMed1984

An evaluation of diagnostic techniques utilized in the initial workup of pediatric patients with acute lymphocytic leukemia.

The records of 32 pediatric patients with acute lymphocytic leukemia (ALL) were reviewed to evaluate the role of various diagnostic techniques used to assess the extent of extramedullary disease. Our findings indicate that adequate screening for hepatosplenomegaly is obtained by clinical assessment and for bone and renal involvement by bone scintigraphy including concomitant renal imaging. We recommend that radiographs be restricted to scintigraphically abnormal areas and/or sites of bone pain. Liver-spleen scintigraphy, gallium studies, intravenous pyelography, and ultrasound studies of the abdomen and pelvis should be utilized only to answer specific clinical questions. Evaluation in this manner reduces both radiation exposure and patient expense, while it adequately defines the extent of disease in these organs.

Bone and Bones↗
PubMed1983

AIDS in 1959?

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1983

The influence of cell cycle kinetics on the radiosensitivity of Down's syndrome lymphocytes.

In agreement with previous work, [60Co]gamma-irradiation shortly after phytohemagglutinin (PHA) stimulation, induces higher frequencies of chromosomal aberrations in trisomy 21 lymphocytes compared to normal controls. However, equal frequencies of chromatid aberrations are induced in fully-stimulated trisomy 21 and normal lymphocytes by irradiation during G2. We have observed that trisomic lymphocytes respond more rapidly to PHA stimulation than normal lymphocytes. Furthermore, we have observed that chromosomal radiosensitivity increases as a function of time after PHA stimulation in normal lymphocytes. When normal lymphocytes are irradiated 8 h after PHA stimulation, the frequencies of chromosomal aberrations induced are comparable to those induced in trisomy 21 lymphocytes irradiated 30 min after PHA stimulation.

Cell Cycle↗
PubMed1983

Absence of hepatic uptake of Tc-99m sulfur colloid in an infant with Coxsackie B2 viral infection.

After the intravenous administration of Tc-99m sulfur colloid, there was found homogeneous lung, renal, and splenic uptake with absence of uptake by the liver and bone marrow of a nine-day-old female infant. More than 20 other doses were dispensed from the same Tc-99m sulfur colloid preparation with the expected biodistribution. A necropsy done two days later showed diffuse hepatic hemorrhagic necrosis without evidence of intravascular fibrin deposition in the lungs or kidneys. The underlying cause of the infant's disease was a Coxsackie B2 viral infection, based upon positive postmortem viral cultures of kidney and liver tissues and characteristic histopathologic lesions of the central nervous system and viscera. The altered biodistribution presumably reflected marked impairment of Kupffer cell function and an apparent increase in pulmonary macrophages.

Coxsackievirus Infections↗
PubMed1983

Mitral valve prolapse: an assessment of clinical features, associated conditions and prognosis.

One hundred and eighty-two patients (100 females, 82 males) with mitral valve prolapse (MVP) confirmed by echocardiography are described. Their ages range from 12 to 87 years (mean 48 years). The symptoms of breathlessness, pain in the chest and palpitations were analysed. They were associated with left ventricular failure, co-existing ischaemic heart disease and arrhythmias in some, but in a proportion the symptoms were thought to be due to psychoneurosis. Seventy-two patients (40 per cent) were referred because of complications of MVP. In 67 patients (37 per cent) the condition was discovered by chance and in 43 patients (24 per cent) neurotic symptoms had led to referral to hospital. A systolic click was heard in 117 patients (54 per cent); 41 patients (23 per cent) had a late systolic murmur and 30 patients (16 per cent) had a pansystolic murmur. The incidence of murmurs rose with increasing age, and pansystolic murmurs were more frequent in males. Thirty-two patients (18 per cent) had neither a click nor a murmur. Twenty-four patients (13 per cent) had associated supraventricular tachycardia and 22 (12 per cent) atrial fibrillation. Twelve patients (7 per cent) had severe mitral incompetence and eight (4 per cent) developed bacterial endocarditis. Only three patients had symptoms suggesting cerebral ischaemia. Twelve patients (7 per cent) had associated aortic incompetence. Twenty-two patients had had an inguinal hernia, the incidence in males over 50 being 26 per cent. Twenty-six patients (14 per cent) had non-specific T wave changes in the electrocardiogram. Echocardiography showed that 112 patients (62 per cent) had mid-systolic buckling of the posterior leaflet and 70 patients (38 per cent) had holosystolic prolapse. In view of the high incidence of complications it is felt that the long-term prognosis not as good as has been generally believed.

Adolescent↗
PubMed1982

Development of tetraploidy in V79 spheroids.

Chinese hamster V-79-171 cells, when placed in suspension culture, spontaneously form multicell spheroids. As the spheroids enlarge the fraction of polyploid (predominantly tetraploid) cells increases and can approach 100% in very large spheroids. Spheroid size, rather than age, seems to be a major determinant for increased ploidy. When cell separation techniques were used to select enriched populations of diploid and tetraploid cells, the growth rate and plating efficiency of the diploid cells was always marginally higher, and they gradually became predominant in mixed monolayer cultures. Cloned tetraploid cells, however, generally remained quite stable, and no consistent ploidy dependent changes in radiosensitivity were observed relative to normal, diploid cell lines.

Animals↗
PubMed1982

The use of diethyl-IDA Tc 99m clearance curves in the differentiation of biliary atresia from other forms of neonatal jaundice.

A family of isotope elimination curves that reflects changes in the biodistribution of diethyl-IDA Tc 99m in neonatal cholestatic jaundice and biliary atresia is defined. Time/activity curves generated from equal areas over the heart and liver were evaluated separately and in conjunction with the scintigraphic data. Patients without scintigraphic evidence of significant hepatic uptake and with a hepatic curve that resembled the cardiac curve were found to have neonatal hepatitis. Good hepatic uptake and a hepatic curve with a terminal portion that appeared to be parallel to or divergent from the cardiac curve were associated with biliary atresia. Apparently converging hepatic and cardiac curves were associated with biliary patency. Although preliminary, these results provide further documentation that diethyl-IDA Tc 99m is useful in discriminating biliary atresia from other causes of cholestatic jaundice, while reducing radiation exposure and the need for pharmacologic intervention.

Bile Ducts↗