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Biomedical subjects

L G Hansen

Publications and source records attributed to L G Hansen.

135 records · Page 8Linked to original sources
PubMedDate not supplied

Estrogenic and antiestrogenic actions of PCBs in the female rat: in vitro and in vivo studies.

A series of studies were performed to examine the effects of various PCB congeners [3,4,3',4'-TCB (PCB77), 2,5,2',5'-TCB (PCB52), 4' OH-2,4,6-TCB (OHPCB)] and a complex PCB mixture (Aroclor 1242; A1242) on the weights and patterns of cell proliferation of immature rat uteri in vivo and the effects of A1242 on gonadotropin release by dispersed anterior pituitary cells in vitro. Immature (20-day) rats were treated ip with corn oil (vehicle), PCBs, or 17 beta-estradiol (E2) once or daily for two consecutive days. Except for PCB77, all PCBs and E2 produced significant increases in uterine weights (P < 0.01) and increases in uterine 3H-thymidine labeling. PCB77 attenuated (P < 0.01) the increase in uterine weight due to either A1242 or E2 treatment. Cultured anterior pituitary cells exposed to varying concentrations of A1242 (0.1 to 50 ppm) exhibited enhanced gonadotropin responses to gonadotropin-releasing hormone (GnRH) similar to that of E2. These results demonstrate that PCBs can produce either estrogenic or antiestrogenic effects.

Animals↗
PubMedDate not supplied

In situ calibration of an oxygen sensor in intervertebral discs.

Intradiscal hypoxia has been suspected of playing a role in the pathogenesis of degenerative back diseases. Investigating this hypothesis requires quantitative methods for measuring PO2 in the intervertebral disc. Tissue oxygen tensions are usually measured with a membrane-covered oxygen-consuming sensor. Calibrating this sensor is complicated by the existence of an oxygen-diffusion gradient in front of the membrane. This article describes a method based on mass spectrometry to measure the oxygen tension in the intervertebral disc and an 'in situ' calibration technique, which is able to compensate for errors caused by the oxygen-diffusion gradient. The principle of the calibration technique is to measure the signal of an inert reference gas, whose partial pressure in the intervertebral disc is known, and to utilize the measured signal to estimate the magnitude of the oxygen-diffusion gradient.

Humans↗
PubMedDate not supplied

High-frequency chest compression system to aid in clearance of mucus from the lung.

The authors developed a high-frequency chest compression (HFCC) device to aid in mucous clearance for patients with obstructive lung disease. The device, designed for self-therapy, consists of a large-volume variable-frequency air-pulse delivery system and a nonstretchable inflatable vest worn by the patient. Pressure pulses are controlled by the patient and applied during expiration. Pulse frequency is tunable from 5 to 25 Hz. Maximum vest pressure is 39 mmHg (5.2 kPa), with patient-controlled vest inflation and deflation time constants of 0.5 s. Vest pressure increases from 28 mmHg (3.7 kPa) at 5 Hz to 39 mmHg (5.2 kPa) at 25 Hz. Preliminary clinical trials have shown the HFCC device to be more effective than standard chest physical therapy. The HFCC device yielded a mean volume of cleared mucus of 3.3 cc per session, compared with 1.8 cc for a conventional therapy session.

Biomedical Engineering↗
PubMedDate not supplied

The pharmacokinetics of hexachlorobenzene in male beagles. Distribution, excretion, and pharmacokinetic model.

The distribution of hexachlorobenzene (HCB) was studied in male beagles after a single 1-mg/kg iv dose of either 14C-HCB or unlabeled HCB. Distribution was also determined in animals after seven daily oral administrations of either 10 mg/kg or 100 mg/kg HCB. Excretion of HCB and metabolites through urinary and fecal routes was studied in all four animals receiving 14C-HCB. In addition, total bile was collected from one of the animals receiving 14C-HCB to determine the importance of biliary excretion. Immediately after iv administration, a large proportion of the dose was distributed to the lungs. From the lungs, HCB was rapidly distributed to highly perfused tissues including the visceral organs and brain. Further redistribution of HCB from highly perfused tissues to adipose tissue occurred at a much slower rate. In animals receiving daily oral doses of 10 or 100 mg of HCB per kg, adipose tissue was again found to accumulate the highest concentrations of HCB. Excretion of HCB and metabolites occurred primarily through fecal elimination, with urinary excretion being of less importance. Fecal excretion was found to be composed of two separate processes, biliary excretion and intestinal excretion. Of these two processes, biliary excretion was shown to be the major contributor to fecal excretion. After single 1-mg/kg IV doses of 14C-HCB in three beagles, blood, urine, and feces were monitored over a 12-week period for 14C content. Computer-assisted pharmacokinetic models were constructed to characterize these data. A three-compartment mammillary model provided the optimum fit to the observed data. Biological half-life values were projected to range from 6 weeks to 3 years.

Animals↗