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Biomedical subjects

B C Smith

Publications and source records attributed to B C Smith.

At least 37 records · Page 2Linked to original sources
PubMed1993

A systematic approach to the sampling of dental DNA.

As investigations into the forensic aspects of DNA analysis continue, the human tooth will play a dual role in identification. Dentin and enamel provide a protective enclosure for genomic and mitochondrial DNA as well as providing the basis for radiographic, biochemical, and ultrastructural forensic studies. The purpose of this investigation is to establish technical guidelines, based on histology and experimental evidence, for the management and sampling of dental DNA. The anatomic location of dental DNA is discussed with emphasis on the conservation of tooth structure during sampling. Ten pairs of maxillary right and left third molars were sampled for DNA following storage for 18 weeks at ambient temperature and humidity. Right third molars were crushed, whereas the left third molars were sectioned conservatively prior to sampling the DNA. The quantity and quality of human DNA obtained from each tooth was compared, as well as the radiographic appearance of remaining hard tissue and the overall simplicity of each approach. DNA typing was performed, both sequence and length based analyses, comparing teeth from the same individual and teeth from different donors. The results of this study suggest that the odontologist will maximize the dental DNA yield by crushing the entire specimen but that substantial yields of human DNA can be obtained by using a conservative technique that preserves the tooth structure. In addition, the method of sampling does not affect the ability to perform DNA typing analyses.

Adolescent↗
PubMed1992

Differences in 2-oxoglutarate dehydrogenase regulation in liver and kidney.

In response to acidosis, renal ammoniagenesis is stimulated, enhancing urinary buffering power, while hepatic ammoniagenesis and ureagenesis decrease, so as to spare bicarbonate consumed in the urea cycle. 2-Oxoglutarate (2-OG) levels can regulate ammoniagenesis in kidney and gluconeogenesis in liver and kidney. Since the activity of 2-oxoglutarate dehydrogenase (2-OGDH) has an important influence on cellular levels of 2-OG, this study evaluated the effects of pH on 2-OGDH in liver and kidney and found that: (1) the isolated enzyme from both organs has the same pH-sensitivity; (2) 2-OGDH flux measured in intact mitochondria was inhibited by increasing H+ in liver, but stimulated in kidney; (3) transport of 2-OG into the mitochondria was not rate-limiting; (4) liver mitochondrial 2-OGDH exhibited a strong preference for 2-OG generated within the mitochondria from glutamate-oxaloacetate transaminase (GOT), suggesting that channelling between GOT and 2-OGDH occurs. Since complexation between 2-OGDH and GOT occurs in vitro, we propose that the degree of complexation is higher in liver than in kidney, such that most of the 2-OGDH may be complexed to GOT in liver. In the liver the inherent H(+)-sensitivity of 2-OGDH is masked by the pH-sensitivity of GOT and the glutamate-aspartate carrier.

Animals↗
PubMed1992

Regulation of glutamine metabolism in dog kidney cortex: effect of pH and chronic acidosis.

To examine the interrelationships of proton compartmentation and ammoniagenesis, experiments were performed in tubules and mitochondria isolated from dog kidney cortex. Tubules were incubated in Krebs-Henseleit buffer at different pH (pHe), and cytosolic pH (pHi) was estimated with the fluorescent probe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. Mitochondrial pH (pHm) was determined simultaneously in intact tubules by use of dimethyloxazolidine-2,4-dione. Over the pHe range 6.9-7.7, pHi was similar in control and acidotic dogs and linearly related to pHe. At pHe 7.4 in control tubules. pHm was 7.78 +/- 0.07, and varied little over the pHe range of 7.0-7.7. The pH gradient across the mitochondrial membrane rose at acid pHe. pHm was more alkaline when estimated in tubules from acidotic dogs compared with controls. Ammonium and glucose productions from glutamine were inversely related to pHe and pHi in tubules from both control and acidotic animals and were higher in acidosis. In contrast, ammonium production by isolated mitochondria did not vary as pHe was altered. Enzyme fluxes, calculated from metabolite changes, demonstrated that glutamate dehydrogenase (GDH) flux was altered. Enzyme fluxes, calculated from metabolite changes, demonstrated that glutamate dehydrogenase (GDH) flux was inversely and glutaminase (PDG) flux was linearly related to pHe. Ammonium production was significantly greater in mitochondria from acidotic dogs because of accelerated flux through PDG but not GDH. The present study demonstrates significant difference between proton compartmentation and regulation of ammoniagenesis in kidneys from acidotic dog compared with rat.

Acidosis↗
PubMed1992

Reconstruction of root morphology in skeletonized remains with postmortem dental loss.

A reversible technique is presented in which the root morphology of missing teeth in skeletonized human remains can be reconstructed for the purpose of radiographic comparison and postmortem identification. In this technique, which is based upon pilot studies with skeletonized mandibles of archival remains, the alveolar socket walls are sealed with a coat of cyanoacrylate cement and injected with a mixture of vinyl polysiloxane and barium sulfate. Radiographs are produced with the radiopaque mixture in place, which highlights the antemortem morphology of the roots. Subsequently, the impression material is removed, resulting in no gross alteration of the evidence. The radiographs made with this technique, as well as the impressions, can be stored for later use at a trial or pending the discovery of antemortem dental evidence.

Adult↗
PubMed1991

Nuclear calcium gradients in cultured rat hepatocytes.

Ca2+ concentrations ([Ca2+]) in cytosol and nucleus in fura-2-loaded cultured rat hepatocytes were determined by three-dimensional (3-D) optical-sectioning microscopy. After determining the empirical 3-D point spread function of the fluorescence microscope-coupled digital video imaging system, contaminating light arising from optical planes above and below the plane of interest was removed by deconvolution using the nearest-neighboring approach (NNA) algorithm. Although deconvolution resulted in substantial improvement in accuracy of fluorescence intensity determinations in single-wavelength excitation images as well as sharper delineation of boundaries between cellular compartments, the complicated mathematical process did not significantly enhance the precision of [Ca2+] values derived from ratiometric (ratio of dual-wavelength excitation) images. In resting hepatocytes, cytosolic Ca2+ (210 +/- 15 nM) was 1.6- to 2-fold higher than nuclear Ca2+ (128 +/- 12 nM). This difference in Ca2+ between the two compartments was detected both in raw ratiometric images and in those processed with NNA algorithm. Addition of arginine vasopressin or epidermal growth factor resulted in significant increases (2- to 3-fold) in both cytosolic and nuclear Ca2+; however, the nuclear-to-cytosolic Ca2+ gradient was preserved in hepatocytes stimulated with mitogens. We conclude that the hepatocyte nuclear membrane contains Ca2+ permeability barriers and Ca2+ transport mechanisms that may be hormonally sensitive. We postulate that the increase in nuclear Ca2+ may be important in regulation of cell proliferation induced by mitogens, possibly by activating Ca(2+)-dependent endonucleases, nuclear calmodulin, or nuclear protein kinase C.

Algorithms↗
PubMed1991

Changes in perikymata and their significance to a postmortem dental identification.

Perikymata are wavelike features that are normally found in the surface enamel of teeth. These structures are known to undergo regressive changes due to gradual attrition, mechanical abrasion, or chemical erosion. Forensic science has suggested that significance be placed on some forms of their loss as indicators of age, oral habits, and alignment of individual teeth. The dental identification of victims of a Vietnam War military aircraft crash is presented. The unusual pattern of perikymata change on two of the teeth suggests the antemortem existence of a removable partial denture. These findings support the exclusionary conclusions.

Dental Enamel↗
PubMed1990

A preliminary report: proximal facet analysis and the recovery of trace restorative materials from unrestored teeth.

A small sample of unrestored teeth with wear facets on the proximal surfaces was examined using a scanning electron microscope and energy-dispersive X-ray fluorescence spectrometry (EDS) analysis. Initial results indicate the potential of this technique for detection of residual restorative materials in these facet areas, and its resulting capability to determine the existence and composition of unrecovered adjacent restorations. The potential value of this technique in the identification of incomplete dental remains is discussed.

Dental Materials↗
PubMed1990

Cognitive changes in chronic renal patients during hemodialysis.

The Number Connection Test (NCT) was used to assess cognitive functioning in 29 chronic renal patients receiving hemodialysis. The patients required an average of 81 seconds to complete the test before hemodialysis compared to 98 seconds during hemodialysis (difference = 17 seconds) (t = 3.29; p = .0027). These findings cannot be explained by test order, sex, age, number of years on dialysis, or duration of each dialysis treatment. This study suggests that renal patients may have decreased cognitive functioning during the hemodialysis treatment. The dialysis period, though a convenient and popular time for patient education, may not be the best time to teach patients. Additional research is needed to confirm these findings and to identify the best and worst times for patient education for hemodialysis patients.

Adult↗
PubMed1989

A comparison of motility: autogenous dermis-fat vs synthetic spherical implants.

The socket and prosthesis motility and the forniceal depths in a group of 47 patients who had undergone enucleation and implantation of synthetic spherical implants were compared with those in a group of 34 patients who had undergone enucleation and implantation of autogenous dermis-fat orbital implants. The primary autogenous dermis-fat orbital implants provided greater socket movement and deeper fornices than the synthetic spherical implants. Prosthesis motility, however, was the same in the two groups.

Adipose Tissue↗
PubMed1988

Renal gluconeogenesis.

Gluconeogenesis, the de novo formation of glucose from non-carbohydrate precursors, is confined to the proximal convoluted and proximal straight tubules of the mammalian kidney. Compared to liver, renal gluconeogenesis has different substrate requirements and responds to different regulatory stimuli. Stimuli in kidney include starvation, metabolic acidosis, glucocorticoid treatment, and, possibly, PTH and catecholamines. Regulation of gluconeogenic flux occurs at three or four key enzyme sites, particularly phosphoenolpyruvate carboxykinase (PEPCK) and fructose 1,6-bisphosphatase. Interest has focused on the relation among H+, Ca2+, and cyclic AMP in the hormonal regulation of gluconeogenesis. The importance of other putative regulators including fructose 2,6-bisphosphate remains to be determined.

Gluconeogenesis↗
PubMed1987

Volkmann's ischemic contractures and blowout fractures.

Volkmann's ischemic contractures have long been recognized by orthopedic surgeons as a sequela of increased pressure within osseofascial muscle compartments. We present evidence that the same mechanism is a cause of fibrosis and contracture of extraocular muscles following orbital blowout fractures. Surgical treatment of a specific, recognizable type of blowout fracture is proposed.

Adolescent↗