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Biomedical subjects

L H Smith

Publications and source records attributed to L H Smith.

At least 145 records · Page 8Linked to original sources
PubMed1977

Clinical features and management of cystinuria.

Cystinuria is a complex hereditary disorder that affects both sexes with equal frequency and severity. Symptoms usually begin early (children and young adults) but may develop at any age. Stature is normal and there are no clinical nutritional abnormalities. The morbidity of cystine urolithiasis is considerable. Hyperuricemia is a frequent associated finding and is probably the result of multiple factors. No other abnormalities are consistently related to this disease. Treatment with adequate oral fluids to ensure a copious urine volume and with oral alkali to keep the urine alkaline is most successful when used prophylactically in the stone-free patient. However, dissolution of existing calculi is unlikely with this regimen alone. The addition of D-penicillamine often results in dissolution of stones and prevention of recurrent calculi in patients who have continued stone growth despite the use of oral fluids and alkali. Because toxic reactions with D-penicillamine are frequent and sometimes severe, this drug should be used only when necessary and then as an adjunct to rather than a substitute for increased oral fluids and alkali. Failure of treatment in spite of adequate therapy should alert the physician to the possibility of coexisting complicating problem.

Adolescent↗
PubMed1976

The APUD cell concept.

Embryonic neural crest cells have been traced to the primitive entoderm where they differentiate into a family of hormone-producing cells, APUD cells. The APUD cell concept explains many otherwise seemingly dissociated clinical circumstances involving endocrine glands and hormone production by tumors.

Amines↗
PubMed1976

Modified nucleosides in urine: selective removal and analysis.

Because excretion of certain nucleosides increases in all types of cancer, detection and treatment of the disease would be enhanced by rapid, simple quantitation of such nucleotides. To facilitate these analyses in urine, we have prepared a specific adsorbent for nucleosides. The affinity adsorbent gel contains an immobilized phenylboronic acid group that specifically binds cis-diols, as in ribonucleosides, which can then be quantititatively recovered by elution with acetic acid. The advantage of this boronate gel over other preparations lies in its high capacity in the swollen state (0.26 mmol/ml), so that only small volumes (less than 1 ml) of gel are required for assays. Nucelosides containing a free diol group on the ribosyl group are retained at pH 8.8 in 0.25 mol/liter salt solution with a retention volume of 15 or larger, as compared with values of 1 to 2 for the free bases. Negatively charged species (not including the boronate complex) are eluted earlier than neutral or cationic species. Added nucleosides (neutral, cationic, or anionic) are quantitatively recovered. Because pseudouridine is eluted in a unique position, this property has been used to measure it in urine. The procedures used are chemically mild. For example, we have confirmed the observation of Fink and Adams [Arch. Biochem. Biophys. 126, 27 (1968)] that urine contains N1-methyladenosine and not N6-methyladenosine, the alkaline rearranged product.

Adenosine↗
PubMed1976

The epitaxially induced crystal growth of calcium oxalate by crystalline uric acid.

Seed crystals of anhydrous uric acid were shown to epitaxially induce the crystal growth of calcium oxalate monohydrate from its metastable supersaturated solution. Scanning electron microscopic examination of crystalline material isolated from the kinetic experiments supports the chemical evidence that calcium oxalate had been nucleated by uric acid. In spite of close lattice similarities between some of the faces of the two phases, the induction period required for heterogeneous nucleation by the seed material was about half of that required for precipitation in the absence of potential nucleating agents. This has created some doubt as to whether crystalline uric acid has an influence on the formation of calcium oxalate lithiasis.

Calcium↗
PubMed1975

Isogeneic or allogeneic transplantation of duct-ligated pancreas in streptozotocin diabetic mice.

Recovery from hyperglycaemia was observed in three different mouse hybrids that were made diabetic with streptozotocin, and then transplanted with pancreas from isogeneic donors whose pancreatic ducts were ligated over 8 weeks earlier. Recovery did not occur in recipients of allografts indicating that islets in ligated pancreas cannot be successfully transplanted across a major histocompatibility barrier. However, in lethally irradiated mice injected with allogeneic bone marrow (allogeneic radiation chimeras), subsequent transplantation of ligated pancreas from either isogeneic donors or allogeneic donors of the same strain as the bone marrow donor decreased blood glucose of diabetic recipients. Thus, irradiation and allogeneic bone marrow therapy allow subsequent allogeneic transplantation of functional islet tissue in diabetic mice. Observations on diabetic mice transplanted isogeneically with ligated pancreas suggest that recovery from hyperglycaemia was more consistent when grafts were placed subcutaneously rather than intraperitoneally and when hosts received ligated pancreas from three donors rather than one. Thus, the site and amount of tissue transplanted are important considerations in the transplantation of ligated pancreas. Persistence of endocrine beta-cells in ligated pancreas was required for recovery in grafted mice since diabetic hosts failed to recover when grafted with ligated pancreas obtained from alloxan or streptozotocin-treated, diabetic donors.

Animals↗
PubMed1975

Epitaxial relationships in urolithiasis: the calcium oxalate monohydrate-hydroxyapatite system.

Chemical kinetic data, complemented with scanning electron-microscope observations of the crystalline phase, show that seed crystals of hydroxyapatite have the ability to induce the growth of calcium oxalate monohydrate crystals epitaxially from a metastable supersaturated solution of calcium oxalate. The rate of growth of calcium oxalate crystals is dependent on the surface area of the seed material and follows a second-order rate law. It is suggested that there may be a causal relationship between the occurrence of apatite crystals in the urinary tract and the formation of both 'pure' and mixed urinary stones containing calcium oxalate. Under similar experimental conditions, however, seed crystals of calcium oxalate monohydrate appeared unable to induce epitaxially the growth of calcium phosphate crystals from a supersaturated calcium phosphate solution, indicating the absence of an epitaxial relationship between calcium oxalate monohydrate and the initially precipitating calcium phosphate phase(s).

Calcium↗
PubMed1975

Determination of urinary carbamylaspartate and dihydro-orotate in normal subjects and in patients with hereditary orotic aciduria.

An isotope dilution assay for urinary dihydro-orotic acid and carbamylaspartic acid (CAA) has been developed which has been shown to yield accurate measurements for these pyrimidine precurosrs. Dihydro-orotic acid could not be detected in 24-hour urine specimens from 10 normal adults and 7 normal children, or in specimens from 2 children with hereditary orotic aciduria Type I. Small amounts (approximately 10 mumole per 24 hours) of carbamylaspartic acid are excreted in normal urine, and there was a modest elevation in CAA excretion in the 2 patients with hereditary orotic aciduria.

Adult↗
PubMed1975

A normobaric hypoxia facility for preparing polycythemic mice for assay of erythropoietin.

A normobaric hypoxia chamber was designed in which large numbers of mice (up to 250) were made polycythemic, after which they were used in an erythropoietin assay. The hypoxic atmosphere was composed of air diluted with N2 gas generated from liquid N2. Continuous exposure of mice to 8% O2 for 11 da resulted in a polycythemia of sufficient magnitude and duration to provide appropriate erythropoietic conditions for the erythropoietin assay. The chamber, which has been in almost continuous operation for 3 yr, requires little attention and maintenance and has proved to be reliable, safe, and economical.

Animals↗
PubMed1975

Mesenteric angiofollicular lymph node hyperplasia (lymphoid hamartoma) with nephroitc syndrome.

In an 18-year-old woman who presented with the nephrotic syndrome and an abdominal mass, removal of a benign mesenteric lymphoid tumor was associated with remission of the nephrotic syndrome without further recurrence (30 month follow-up). Biopsies of both kidneys showed a minimal-change glomerular lesion. Clinical and pathologic characteristics of angiofollicular lymph node hyperplasia and its possible relationship to the nephrotic syndrome are discussed.

Adolescent↗