PubMed Health⌕ Search

Biomedical subjects

K S Subramanian

Publications and source records attributed to K S Subramanian.

At least 19 recordsLinked to original sources
PubMed1993

Canadian Human Specimen Bank: an emerging Great Lakes health effects program.

Plans for establishing a Canadian human specimen bank as part of the Great Lakes Health Effects program initiated by the Environmental Health Directorate, Health and Welfare Canada, have been under consideration since 1990. This presentation delineates the program rationale, our objectives in establishing the bank and the progress we have made to-date in achieving our goal. This paper is intended to be a planning document.

Canada↗
PubMed1993

Bone-lead analysis: development of analytical methodology for milligram samples.

A graphite platform-in-furnace atomic absorption spectrometric (GFAAS) method for determining micrograms/g levels of Pb in 10-20 mg cortical and trabecular primate bone samples is described. The GFAAS method is based on an ambient temperature nitric acid digestion of the sample, matrix modification with palladium nitrate, stabilized temperature platform furnace atomization, and a systematic evaluation of the temperature program of the atomizer. The method of standard additions is mandatory. The detection limit (3 standard deviations of the blank) is 0.19 micrograms Pb/g dry weight for a 10-mg sample taken up in a 1-mL volume. Data are presented on the degree of accuracy and precision. The accuracy of the proposed GFAAS method has been assessed using the IAEA bone reference material, H-5, and by comparing the values obtained in a bone sample with an isotope dilution mass spectrometric (IDMS) procedure. The GFAAS method can be applied to the determination of Pb in 10-20 mg bone samples and for concentrations which are > or = 10 x detection limit. The method is simple, fast, and contamination-free since the entire operation from weighing to GFAAS measurement is carried out in the same centrifuge tube. The method has been applied to the determination of total-Pb in some adult and fetal primate cortical and trabecular bone specimens.

Animals↗
PubMed1992

Sampling of cortical and trabecular bone for lead analysis: method development in a study of lead mobilization during pregnancy.

The paper describes a methodological approach to the investigation of maternal-fetal transfer of lead in a non-human primate species, with particular focus on skeletal tissue, which is known to be a site of lead deposition. Eight female cynomolgus monkeys were dosed with lead acetate during gestation, and in four of the animals, the isotopic composition of the lead was modified by enriching the amount of the stable isotope 204Pb included in the dose. Biopsy and dissection procedures for the preparation of bone samples for lead analysis and stable lead isotope analysis are described. Emphasis is placed on the containment of potential contamination of the samples by lead during preparation. Containment procedures included: use of a Class 100 clean room, special cleaning regimes and use of Teflon containers and stainless steel instruments. Preliminary data of lead concentrations in adult bone (trabecular and cortical) and fetal bone subsequent to the dosing regimen of lead during pregnancy, suggest notable differences between the two bone "compartments" examined. The bone samples of fetuses from the dams which had received enriched 204Pb showed drastically reduced 206Pb/204Pb isotope ratios.

Animals↗
PubMed1990

Biological monitoring for occupational cadmium exposure: the urinary metallothionein.

The relationship between urinary metallothionein and kidney and liver cadmium levels was examined in 68 active and retired smelter workers. Metallothionein was analyzed by a radioimmunoassay and liver and kidney cadmium levels were determined by in vivo neutron activation. Four workers suffered from severe renal dysfunction and excreted high amounts of total protein and beta 2-microglobulin and greater than 1 mg metallothionein/g creatinine. In the remaining 64 workers the urinary metallothionein levels correlated significantly with the cadmium levels in both liver and kidney. Similarly, in these individuals urinary metallothionein was significantly related to cadmium in blood and urine. These results demonstrate that urinary metallothionein is a sensitive biological indicator of cadmium exposure and body burden, before the onset of severe renal dysfunction.

Adult↗
PubMed1990

Transtentorial brain herniation in the monkey: analysis of brain stem auditory and somatosensory evoked potentials.

A monkey model of transtentorial brain herniation (TBH) was created to simulate the clinically encountered situation of a gradually expanding intracranial lesion. TBH was produced by extradural balloon inflation over a 4-hour period and documented by the appearance of the pupils as dilated or fixed at midposition. Intracranial pressure (ICP), brain stem auditory evoked potentials (BAEP), and short-latency somatosensory evoked potentials (SSEP) were recorded before, during, and after TBH. Statistical significance from baseline values to TBH was found for diminution of the BAEP amplitude, rise of the ICP, and diminution of the SSEP amplitude. An ICP rise to twice the baseline value and a 25% decrease in Wave V amplitude was found 1 hour before TBH. Changes in BAEP and SSEP took several minutes after deflation to return to baseline values. Analysis of Wave V of the BAEP was as sensitive as ICP in warning of TBH. Discussion centers upon previous animal studies of brain herniation and ICP elevation, and findings reported in humans deteriorating as a result of intracranial mass lesions. BAEP and SSEP monitoring may be used as noninvasive tests for brain stem compression in the setting of primate TBH, and in the future may be used to guide the effectiveness of therapy.

Animals↗
PubMed1989

Determination of lead in blood by graphite furnace atomic absorption spectrometry--a critique.

Graphite furnace atomic absorption spectrometry (GFAAS) is increasingly becoming the method of choice for the determination of Pb in blood. The major GFAAS methods that have been published to date include: (i) direct introduction of the sample into the furnace; (ii) dilution with water, Triton X-100 or acid; (iii) deproteinization with nitric acid; (iv) matrix modification; and (v) solvent extraction. This review focuses on the difficulties associated with each of these methods, and highlights recent attempts to overcome matrix interferences and improve the accuracy and precision of Pb determination in blood using modern furnace technology, especially the stabilized temperature platform furnace.

Humans↗
PubMed1989

Lead concentrations in human bones from the Canadian population.

Stable lead was determined in post-mortem samples of human bones from three Canadian cities. All age groups and both sexes were represented. The cities selected for investigation were Winnipeg, Montreal and Charlottetown. No significant difference was found between the locations, although levels tended to be higher for Montreal. Mean lead concentrations (micrograms Pb/g ash) were 8.98 +/- 1.17, 11.11 +/- 1.74 and 8.47 +/- 1.06 for Winnipeg, Montreal and Charlottetown, respectively. Corresponding geometric means were 6.21, 7.88 and 6.71, respectively. Individual values ranged from 0.45 to 240.07 micrograms Pb/g ash. Concentrations were highest in the greater than 20-year age group, indicating increased body burden with age. An increase in lead concentration was observed for the ages 1-11 years with a decrease for the 12-19-year age group. Differences in concentrations between the sexes were not significant. Higher than average concentrations were observed in samples obtained from Winnipeg for the period 1976-1980, particularly in the 1-4-year age group. A similar pattern was observed in the air lead concentrations, suggesting a possible correlation between the concentrations of lead in the air and in bones at Winnipeg.

Age Factors↗
PubMed1988

Determination of lead in blood--an interlaboratory study.

An international co-operative blood-Pb interlaboratory study and a Canadian co-operative blood-Pb interlaboratory study were conducted using freeze-dried bovine blood samples with different endogenous Pb levels. The samples were prepared from whole blood of a nonexposed cow and another fed with a single dose of lead acetate. The mean values computed for the two samples analyzed by 25 international participants from 13 countries were 55 and 250 micrograms Pb l-1, respectively. These results showed a positive bias of 10% for the low level and 9% for the high Pb level with respect to the reference values obtained by isotope dilution mass spectrometry. In the case of the Canadian interlaboratory survey the mean values computed for the two samples analyzed by the 12 participants were 40 and 229 micrograms Pb l-1, respectively. These results showed a negative bias of 20 and 0.4% in relation to the target values of 50 and 230 micrograms Pb l-1, respectively. Despite such a bias, the data, on the whole, were of acceptable precision and accuracy when compared with previous interlaboratory blood-Pb surveys.

Animals↗
PubMed1987

Modified auditory brainstem responses (MABR): Part I--Rationale and normative study.

Binaural, rapid rate, ABR stimulation at four intensity levels (MABR) as well as ABR at two intensity levels were carried out in 35 normal subjects. Latency and amplitude relationship with stimulus intensity of wave V of the MABR was extensively studied in these subjects. MABR recording is a rapid, sensitive, non-invasive screening method readily done at the intensive care bedside. Less than 10 minutes is required in addition to the ABR examination time. Normality of the MABR potentials implies a high degree of peripheral auditory and brainstem functional integrity, augmenting information gained with standard ABR technique. Only clinical trials can decide if MABR sensitivity will exceed that of the ABR and prove helpful to diagnosis and patient care.

Acoustic Stimulation↗
PubMed1986

Electrocochleography recorded non-invasively from the external ear.

A method is described to record cochlear evoked potentials in humans (ECochG) with a low impedance electrode on the external ear near the opening of the external auditory canal. A piezoelectric click stimulus was delivered to the ear through a polyethylene tube creating diminution of stimulus artifact and a signal delay. Wave forms resembling the cochlear microphonic (CM), summating potential (SP) and the eighth nerve action potential (N1) were differentially accentuated by changes in stimulation and recording parameters. The addition or subtraction of condensation and rarefaction click wave forms further clarified the N1 and SP, or the CM potential, respectively. These responses can be recorded with most contemporary evoked response equipment. This non-invasive method of ECochG lends itself well to the study of hearing loss and possibly other neurologic disorders, and may complement BAER examination especially when wave I is poorly delineated.

Audiometry, Evoked Response↗
PubMed1985

Kidney and liver levels of some major, minor and trace elements in two Ontario communities.

The contents of Ag, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Th, Ti and Zn in 143 autopsied liver and kidney specimens from two Ontario communities (Kingston and Ottawa) were determined using the techniques of inductively-coupled plasma--atomic emission spectrometry, and electrothermal atomization--atomic absorption spectrometry coupled with hydride evolution (As, Se), reduction--aeration (Hg), or solvent extraction (Pb). The majority of samples came from individuals older than 50 y. In general, the data for the various elements were independent of age or sex but showed some dependence on location for elements such as Cu, Fe, K, Mg, Mn, Na, P, Se and Zn. Despite these differences the elemental values of the liver and kidney samples from both the communities were within the normal range.

Adolescent↗