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Biomedical subjects

R W Hardy

Publications and source records attributed to R W Hardy.

At least 19 recordsLinked to original sources
PubMed1992

Genetic dissection of cyclophilin function. Saturation mutagenesis of the Drosophila cyclophilin homolog ninaA.

Cyclophilins, the intracellular receptors for the widely used immunosuppressant cyclosporin A have been found to be peptidyl-prolyl cis/trans isomerases and have been implicated in intracellular protein folding and trafficking. The Drosophila ninaA gene encodes a photoreceptor-specific cyclophilin homolog involved in rhodopsin biogenesis. ninaA mutants have a 90% reduction in the levels of Rh1 rhodopsin. To gain insight into the role of cyclophilins in vivo, we carried out a genetic screen designed to identify functionally important regions in the ninaA protein. Over 700,000 mutagenized flies were screened for a visible ninaA phenotype and 70 independent mutations in ninaA were isolated and characterized. These mutations provide a detailed dissection of the structure/function relationships in cyclophilin. We also show that mammalian cyclophilins engineered to contain missense mutations found in two temperature-sensitive ninaA alleles display temperature-sensitive prolyl cis/trans isomerase activity.

Alleles↗
PubMed1992

The effects of extracellular calcium and epinephrine on cytosolic-free calcium in single rat adipocytes.

Changes in cytosolic calcium concentration ([Ca2+]i) in response to extracellular calcium and epinephrine were monitored in individual rat adipocytes by both photon counting and digital imaging techniques utilizing the intracellular fluorescent calcium probes Fura-2 and Indo-1. Adipocytes containing Fura-2 were attached to coverslips and shown to be as hormonally responsive to insulin as adipocytes in suspension [3.5 +/- 0.8 (n = 5) vs. 4.2 +/- 0.6 (n = 8)-fold increase in glucose oxidation over basal in response to 0.7 nM insulin]. Basal [Ca2+]i in single rat adipocytes was found to be 128 +/- 6 nM (n = 100). The addition of either extracellular calcium or epinephrine elicited transient, concentration-dependent increases in [Ca2+]i. Although the characteristics of calcium- and epinephrine-induced calcium transients are generally similar, the peak [Ca2+]i increase over basal is higher in response to calcium vs. epinephrine [37 and 64% (1 and 27 microM epinephrine), vs. 132 and 236% (2 and 4 mM calcium)]. All the cells tested responded to calcium but only 67% responded to epinephrine. Both alpha- and beta-adrenergic agonists were able to increase [Ca2+]i. The epinephrine-induced [Ca2+]i transients appear to be dependent upon extra-cellular calcium. Neither cholera nor pertussis toxin treatments altered basal [Ca2+]i. However, after treatment of adipocytes with either pertussis or cholera toxin, epinephrine stimulated oscillations in [Ca2+]i. Digital imaging revealed that adipocytes demonstrate a high degree of intracellular spatial heterogeneity and intercellular variability in the magnitude of response to both calcium and epinephrine. These studies demonstrate the feasibility of using single rat adipocytes to monitor intracellular free calcium, using both photon counting and digital imaging.

Adipose Tissue↗
PubMed1992

A multicenter evaluation of lipid profiling with a compact analyzer (Miles Clinistat).

We evaluated the Clinistat Analyzer (Miles Inc., Diagnostics Division, Elkhart, IN) for measuring cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol at three medical centers. The system, based on multilayer film technology, uses precalibrated, dry film reagent disks. Ten microliters of serum is applied to the dry film reagent disk in the test procedure. For HDL-cholesterol measurement, serum is pretreated by precipitation with phosphotungstic acid and magnesium chloride. Total precision (CVs) of each of the three assays was less than or equal to 5%. The assay ranges were linear and satisfactory for clinical use. Patients' results compared well with established methods. No significant interferences were found with hemolysis, icterus, and lipemia.

Chemistry, Clinical↗
PubMed1991

Photoreceptor deactivation and retinal degeneration mediated by a photoreceptor-specific protein kinase C.

The protein kinase C (PKC) family of serine-threonine kinases has been implicated in the regulation of a variety of signaling cascades. One member of this family, eye-PKC, is expressed exclusively in the Drosophila visual system. The inaC (inactivation-no-afterpotential C) locus was shown to be the structural gene for eye-PKC. Analysis of the light response from inaC mutants showed that this kinase is required for the deactivation and rapid desensitization of the visual cascade. Light adaptation was also defective in inaC mutant flies. In flies carrying the retinal degeneration mutation rdgB, absence of eye-PKC suppressed photoreceptor cell degeneration. These results indicate that eye-PKC functions in the light-dependent regulation of the phototransduction cascade in Drosophila.

Adaptation, Physiological↗
PubMed1991

Palmitate stimulates glucose transport in rat adipocytes by a mechanism involving translocation of the insulin sensitive glucose transporter (GLUT4).

In rat adipocytes, palmitate: a) increases basal 2-deoxyglucose transport 129 +/- 27% (p less than 0.02), b) decreases the insulin sensitive glucose transporter (GLUT4) in low density microsomes and increases GLUT4 in plasma membranes and c) increases the activity of the insulin receptor tyrosine kinase. Palmitate-stimulated glucose transport is not additive with the effect of insulin and is not inhibited by the protein kinase C inhibitors staurosporine and sphingosine. In rat muscle, palmitate: a) does not affect basal glucose transport in either the soleus or epitrochlearis and b) inhibits insulin-stimulated glucose transport by 28% (p less than 0.005) in soleus but not in epitrochlearis muscle. These studies demonstrate a potentially important differential role for fatty acids in the regulation of glucose transport in different insulin target tissues.

3-O-Methylglucose↗
PubMed1991

Cervical paraganglioma with subsequent intracranial and intraspinal metastases. Case report.

Paragangliomas, tumors derived from the extra-adrenal paraganglion system, have commonly been found in the retroperitoneum, abdomen, mediastinum, skull base, and neck. Rare intraspinal cases have included involvement of the cauda equina and filum terminale, and a recent case has been reported of thoracic cord paraganglioma with metastasis to the cauda equina. The authors present the case of a patient with a cervical paraganglioma who underwent subtotal resection followed by postoperative irradiation; she subsequently developed multiple intracranial and intraspinal metastases 7 months following the first decompression procedure.

Adult↗
PubMed1990

Uses of biotechnology and technology transfer to keep food safe.

The era of biology is composed of 1) the definition of molecular laws of biology, 2) the exponential expansion of the data base, and 3) the establishment of the first generation molecular and cellular tool kit; this era is driving the development and commercialization of biotechnological products and processes for agriculture and the food system. These products and processes should have a major impact in maintaining and improving food safety. Several meeting and organizational initiatives on biotechnology and food safety are summarized. Possible roles of biotechnology in areas of food safety involve microbial contaminants, nutritional quality, natural antimetabolites, allergens, toxicants, and synthetic chemical residues. Biotechnology will have an impact on all these areas through both improved ability to measure as well as to modify microbes, animals, and plants used as food. Diagnostics for microbial contaminants and biobased alternatives to synthetic chemicals are most advanced. However, all these biotechnological products and processes for food safety are in very early stages of development and commercialization.

Animals↗
PubMed1978

The opportunity for and significance of alteration of ribulose 1,5-bisphosphate carboxylase activities in crop production.

Increased population and the dietary changes accompanying increased affluence are creating a need for a suggested doubling of world cereal grain production (a 3% per year compounding rate) and quadrupling of grain legume production (a 6% per year compounding rate) during this quarter century (1). CO2 enrichment of field-grown crops has demonstrated the possibility of enhancing RuBP carboxylase activity to achieve improved crop production; it increases the production of grain legumes by 50 to 100% and that of cereal grains, for which the studies are less complete, by perhaps 10 to 50%. Results of O2 alteration of growth-room legumes and cereal grains are consistent with the results of CO2 enrichment except for a second role of O2 in assimilate partitioning. It may be necessary to include other components of the system, e.g., additional soil fertility, especially for non-N2-fixing plants, to enable an improved RuBP carboxylase to increase production. No practical method--chemical, genetic, or physical--of improving RuBP carboxylase activity has been reported.

Agriculture↗
PubMed1978

Dural arterio-venous malformations involving the cavernous sinus: a case report.

A case of dural arteriovenous malformation involving the cavernous sinus is reported. The patient was successfully treated with selective embolisation of the fistula. These patients constitute a distinct neuro-ophthalmological syndrome which may be very difficult to diagnose clinically because of the subtle signs and symptoms they present with. Angiography is necessary to make diagnosis and to differentiate these patients from those with the more common carotidcavernous fistulae.

Adult↗
PubMed1976

Alexia without agraphia.

This typical case of alexia without agraphia, caused by an astrocytoma, is the first recorded case in the literature of alexia without agraphia with a right homonymous hemianopia caused by a tumor. This case differs from previously reported cases of the syndrome by its fluctuating clinical course and its slow progression. All but one of previously reported cases had been of vascular or surgical etiology. This course and the associated radiographic findings should differentiate the neoplastic from the vascular etiology of this most fascinating syndrome.

Astrocytoma↗
PubMed1975

The influence of chromosome content on the size and shape of sperm heads in Drosophila melanogaster and the demonstration of chromosome loss during spermiogenesis.

The volumes of sperm heads were estimated from three-dimensional reconstructions of serially sectioned bundles of nearly mature spermatid nuclei. Cysts from males in which all sperm are expected to have comparable amounts of chromatin (X/Y and 1n(3LR)/+) show unimodal frequency distributions of nuclear volumes, whereas cysts from males in which meiotic segregation is expected to deliver unequal amounts of chromatin material to spermatid nuclei show two (XY/O and XY/Y) or more (T(2;3)/+ ANd C(2L);C(2R)) modes. The mean volumes of the subpopulations in these cases are related in the same proportions as the metaphase lengths of their chromosomal complements. Thus the volumes of sperm nuclei are proportional to their DNA content. Sperm head shape, on the other hand, does not appear to be very sensitive to chromosomal constitution, as heads of different size do not vary greatly in shape.----The numbers of sperm heads in the various size classes in a cyst depart from mendelian expectations; these departures are caused by the elimination, during individualization, of chromosomes contained within micronuclei that are formed in spermatids at the end of the second meiotic division. The effect of this chromosome loss is to increase the proportion of nullosomic gametes in the sperm pool.----The relative frequencies of XY-bearing and nullo-X, nullo-Y sperm in XY/O males were estimated from the volume measurements. Taking this estimate as a measure of the fertilizing population, it is possible to infer from the change in sex ratio over time following insemination, that XY-bearing sperm have an advantage of 1.5 over nullo-X, nullo-Y sperm in leaving the seminal receptacle of the female for fertilization of ova.

Animals↗