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Biomedical subjects

D L Cook

Publications and source records attributed to D L Cook.

27 records · Page 2Linked to original sources
PubMed1987

A quantitative method for the detection and localization of quantum-limited events from radionuclides in cells and tissue sections by computer-enhanced video microscopy.

Cellular dynamics often involve extremely low concentrations of biologically active substances, which can be radiolabeled and detected, localized and quantitated by autoradiography. The latter may require exposures from a few days to many months. The objective of this research was to demonstrate the feasibility of reducing this long period of data collection by one to two orders of magnitude, while maintaining or improving the spatial resolution and localization in tissues and the quantitative characteristics inherent in autoradiography. A mathematical model describing the complete system was generated using energy partition calculations to estimate photon production via scintillant per H3 beta particle emission and to estimate the subsequent photon capture based upon imaging system parameters and microscope geometry. Calculations showed that, typically, a single tritium beta particle produces a maximum of 5.8 X 10(3) photons. A photon-limited camera and microscope imaging system were selected and optimized in conjunction with a specially developed physical scintillation model. Results showed that the number of detected photoevents increases monotonically with both signal integration time and, independently, with the concentration of the radionuclide. Consequently, this work demonstrates that video microscopy imaging methods can spatially and temporally quantify very low concentrations of radiolabeled substances and can reduce data acquisition times.

Beta Particles↗
PubMed1986

Induction of estrus in ovariectomized cows and heifers: effects of estradiol benzoate and gonadotropin releasing hormone.

Three experiments were conducted with ovariectomized (OVX) cows and heifers to investigate potential neuroendocrine mechanisms controlling estrous behavior. In Exp. 1, 10 OVX cows were treated with either 125 micrograms estradiol benzoate and 10 cc saline (125 micrograms EB + SAL), 125 micrograms EB and 500 micrograms gonadotropin releasing hormone (125 micrograms EB + GnRH), 250 micrograms EB and 10 cc SAL (250 micrograms EB + SAL), 250 micrograms EB and 500 micrograms GnRH (250 micrograms EB + GnRH) or 500 micrograms EB and 10 cc SAL (500 micrograms EB + SAL) in a replicated 5 X 5 Latin-square design. During the 48 h following EB injection, 2-h observation blocks were alternated with 2-h non-observation blocks. During each 2-h observation block, 14 behavioral interactions were monitored. The percentage of cows in estrus was lower for cows receiving 125 micrograms EB as compared with those given the higher doses. However, the cows receiving 125 micrograms EB + SAL did not differ in their estrous response from those receiving 125 micrograms EB + GnRH. The interval from injection to the onset of estrus and the duration of estrus were similar for all treatments. In Exp. 2, 10 OVX heifers were subjected to the same treatments and observation procedures utilized in Exp. 1. The results of Exp. 2 were similar to those of Exp. 1. In Exp. 3, 10 OVX cows were treated with either 300, 600, 1,200, 2,400 or 4,800 micrograms EB in a replicated 5 X 5 Latin-square design.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

The sulphonylurea receptor may be an ATP-sensitive potassium channel.

The stimulation of insulin secretion from the beta cells of the islets of Langerhans appears to be mediated by a decrease in the cell-membrane potassium-ion permeability. Tolbutamide reduced K+ movement through an ATP-sensitive K+ channel in patches of plasma membrane from an insulin-producing cell line when applied to the external surface of the membrane. The effect occurred at concentrations which exist in the serum of patients treated with tolbutamide and which stimulate insulin secretion from islets of Langerhans in vitro. Glibenclamide had a similar effect but, in keeping with its greater therapeutic potency, at concentrations one hundred times lower. These findings suggest that an ATP-sensitive K+ channel or a protein closely associated with it may be the receptor through which sulphonylureas act to stimulate insulin secretion in vitro.

Adenosine Triphosphate↗
PubMed1985

Voltage-gated Ca2+ current in pancreatic B-cells.

Voltage-dependent inward Ba++ and Ca++ currents were recorded in cultured neonatal rat pancreatic islet cells using the whole-cell voltage clamp technique. Outward current was suppressed by internal Cs+ and ATP and external TEA. Inward currents activated rapidly and decayed to a variable extent. The current decay was particularly marked when using long duration or large depolarizing pulses. Currents were due to Ca++ channel activation since they were abolished by omitting Ba++ and Ca++ or including Co++.

Animals↗
PubMed1976

A continuous-flow, variable mixing valve for perfusion experiments.

The device described here continuously mixes two solutions in any required ratio and has been used at flow rates of 6 ml/min in tissue perfusion experiments. Its low-cost construction consists of a three-way miniature solenoid valve driven by a simple electronic circuit. Mixing is stable, reproducible and accurate to +/- 1% of dial setting.

Electronics, Medical↗
PubMedDate not supplied

Correlations among autonomic, sensory, and motor neural function tests in untreated non-insulin-dependent diabetic individuals.

A well-defined group of untreated non-insulin-dependent (NIDD) subjects were evaluated to determine whether involvement of neural function measurements is generalized and symmetrical and to compare the autonomic, sensory, and motor neural measurements. After age adjustment, the sensory and motor neural function measurements were significantly slower in the diabetic group than in normal subjects (P less than 0.01). Similarly, the autonomic nervous system function measurements were also abnormal in the NIDD group (P less than 0.01). Further analysis revealed that each of the specific measurements--median motor nerve conduction velocity (NCV,P less than 0.005), peroneal motor NCV (P less than 0.005), median sensory NCV (P less than 0.005), dark-adapted pupil size after muscarinic blockade (P less than 0.02), pupillary latency time (P less than 0.02), and RR-variation after beta adrenergic blockade (P less than 0.001)--was significantly less by analysis of covariance after age adjustment in the NIDD group than in normal subjects. Thus, there was evidence of motor and sensory neural impairment in the upper and lower extremities as well as evidence of impairment of the reflex arcs involving the parasympathetic nerves to the heart and eye and the sympathetic nerves to the iris. Further analysis revealed that right and left NCV were correlated (P less than 0.01), as were the median motor and median sensory NCV (P less than 0.01), the median motor and peroneal motor NCV (P less than 0.001), and the peroneal motor and median sensory NCV (P less than 0.001). Thus, there was evidence of symmetrical upper and lower limb, as well as motor and sensory proportional involvement of large nerve fiber NCV in this group of NIDD subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗