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Biomedical subjects

J Blackman

Publications and source records attributed to J Blackman.

6 recordsLinked to original sources
PubMed1991

Nocturnal elevation of glucose levels during fasting in noninsulin-dependent diabetes.

To define the spontaneous diurnal variations in glucose regulation during fasting in noninsulin-dependent diabetes (NIDDM), we measured circulating levels of glucose, insulin, C-peptide, GH, cortisol, and glucagon at 15-min intervals in 11 patients with untreated diabetes and 7 matched control subjects studied during a 24-h period. The rates of insulin secretion were derived from the concentrations of C-peptide by deconvolution using a two-compartment mathematical model for C-peptide distribution and metabolism. In both groups of subjects, despite continued fasting, glucose levels stopped declining in the evening and subsequently rose throughout the night to reach a morning maximum. Elevated levels persisted until noon. The morning glucose maximum corresponded to a relative increase of 23.8 +/- 5.5% above the evening nadir in NIDDM patients and 13.2 +/- 4.6% in nondiabetic subjects (P less than 0.05). In NIDDM patients, insulin levels and insulin secretion rates did not parallel the nocturnal glucose changes. In contrast, in control subjects, this nocturnal glucose rise coincided with a similar increase in insulin secretion rates. Cortisol concentrations in patients with NIDDM were higher than those in control subjects throughout the study period (P less than 0.001) and rose earlier in the evening than in control subjects, thus failing to demonstrate the normal nocturnal suppression. In both groups of subjects, the nighttime glucose elevation was temporally and quantitatively correlated with the circadian cortisol rise. GH secretion was increased in the evening and nighttime periods compared to the daytime values, and in NIDDM patients, but not in control subjects, the size of the morning glucose elevation was directly related to the magnitude of this increase in GH secretion (r = 0.88; P less than 0.01). Glucagon concentrations were similar in both groups of subjects and remained essentially constant throughout the study period. We hypothesize that the nocturnal glucose rise that occurs during fasting represents a normal diurnal variation in the set-point of glucose regulation amplified by counterregulatory mechanisms activated by the fasting condition.

Adult↗
PubMed1990

Methods for the endoscopic photographic and visual detection of helium cadmium laser-induced fluorescence of Photofrin II.

Endoscopic detection of small tumors is key to the early diagnosis and treatment of malignancy. This paper describes a simple, endoscopic detection system which enables tumor localization and a permanent record based on the laser-induced fluorescence of dihematoporphyrin ether (LIFD). Spectral analysis of dihematoporphyrin ether (DHE, Photofrin II) was performed with a Perkin Elmer LS-5 scanning fluorimeter. DHE at concentrations of 50 micrograms/ml and 5 micrograms/ml in 95% ethanol were tested, demonstrating fluorescence quenching at 50 micrograms/ml DHE at 406 nm excitation. This phenomenon was not observed at 442 nm excitation. Based on this data and the availability of the helium cadmium laser, a series of endoscopic detection systems was developed and tested utilizing a LiConix 4240NB helium cadmium laser (TEMoo, 442 nm, 40 mW). A fiber with a microdiverging (MDL) lens was used. Irradiance achieved at the tip of the fiber was 31.58 mW/cm2 for MDL. A Corning 34832 (550 nm) sharp cutoff barrier filter was coupled to an Olympus OES BF2T10 bronchoscope. Successful detection of LIFD was obtained. Direct observation of LIFD is possible when wearing Laserguard argon safety goggles (OD 15 at 488 nm, OD 11 at 514 nm). Photographic recording of LIFD was performed with the following cameras and parameters: Olympus OM-2S camera (OM2) with EES135 film (ISO 1600) with a 4-second exposure (method 1) and the Olympus OES SCP-10 instant camera with Polaroid 779 (ISO 640) film and a 120-second exposure (method 2). The photographic methods demonstrate the red fluorescence of DHE on filter paper disks at concentrations of 0.5 micrograms/ml (500 ng/ml). (ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Lack of effect of high-dose biosynthetic human C-peptide on pancreatic hormone release in normal subjects.

We studied the effect of high doses of biosynthetic human C-peptide on pancreatic hormone secretion in response to oral (75 g) and intravenous [( IV] 0.33 g/kg of D50%) glucose on normal volunteers. The infusion of human C-peptide at a rate of 360 ng/kg/min body weight, increased the plasma C-peptide concentration from a basal level of 0.32 +/- 0.04 pmol/mL to 38.5 +/- 1.8 pmol/ml. Overall, C-peptide had no significant effect on the serum levels of glucose, insulin, proinsulin, glucagon, and pancreatic polypeptide, either under basal conditions or following IV and oral glucose administration. However, small decreases in glucose and insulin concentrations that were not statistically significant were seen during the first hour after C-peptide infusion. The results of the present studies are therefore consistent with the conclusion that even supraphysiologic plasma concentrations of infused C-peptide do not affect basal insulin secretion or overall insulin secretory responses to oral or IV glucose. However, we cannot definitively exclude a small reduction in insulin secretion in the first hour after oral glucose ingestion.

Adult↗
PubMed1986

Two simple models for teaching fiberoptic choledochoscopy techniques.

Two models are used for the development of practical skills with the fiberoptic choledochoscope. The models allow the surgeon to become comfortable in manipulating the fiberoptic choledochoscope and various tools. Olympus, Pentax and American ACMI fiberopticscopes have been shown using these models. Use of models eliminates the cost and ethics of using live animals, as well as ensuring training before intraoperative choledochoscopy is attempted on patients.

Animals↗
PubMed1976

Hydroxyquinolines inhibit ribonucleic acid-dependent deoxyribonucleic acid polymerase and inactivate Rous sarcoma virus and herpes simplex virus.

8-Hydroxyquinoline and several of its derivatives inactivate the transforming ability of Rous sarcoma virus and inhibit its ribonucleic acid-dependent deoxyribonucleic acid polymerase activity. The copper complex of these metal-binding ligands is as active as the free ligand. The activity of the 8-hydroxyquinolines is approximately 50-fold more effective than another group of metal-binding compounds that we have tested, the thiosemicarbazones. In contrast to the potency of the 8-hydroxyquinolines to inactivate Rous sarcoma virus, no intracellular inhibition of transformation could be demonstrated at a concentration that did not affect the growth and appearance of the cells. Cellular deoxyribonucleic acid synthesis was inhibited to a greater extent than was ribonucleic acid or protein synthesis. The phenomenon of "concentration quenching" was observed with high concentrations of drug, causing less inhibition of deoxyribonucleic acid synthesis than was observed with lower concentrations. Herpes simplex virus type 1 was inactivated also by the 8-hydroxyquinolines and their copper complexes. No intracellular inhibition of plaque formation was observed. Treatment with 8-hydroxyquinoline sulfate had no effect on the resolution of herpetic keratitis in rabbits. Some 8-hydroxyquinolines bind to deoxyribonucleic acid in the presence of copper, a phenomenon that may be important in their antiviral activity.

Animals↗