Compact and Efficient 3.2-W Diode-Pumped Nd:YVO(4)/KTP Green Laser

We demonstrate a simple way to achieve single-frequency operation by using fiber-coupled diode-pumped Nd:YVO(4)/KTP green lasers in a short standing-wave linear cavity. A single-mode output with 3.2-W green power was generated with a 12.6-W pump power corresponding to a conversion efficiency of 25.4%. The single-mode operation was obtained through the combined action of the anisotropic emission cross section of Nd:YVO(4) and the KTP crystal acting as a birefringent filter.

Effects of a water-soluble extract of Cordyceps sinensis on steroidogenesis and capsular morphology of lipid droplets in cultured rat adrenocortical cells

Cordyceps sinensis contains a factor that stimulates corticosteroid production in the animal model. However, it is not known whether this drug acts directly on the adrenal glands or indirectly via the hypothalamus-pituitary axis. In the present study, we used primary rat adrenal cell cultures to investigate the pharmacological function of a water-soluble extract of Cordyceps sinensis (CS) and the signaling pathway involved. Radioimmunoassay of corticosterone indicated that the amount of corticosterone produced by adrenal cells is increased in a positively dose-dependent manner by CS, reaching a maximum at 25 microg/ml. This stimulating effect was seen 1 h after CS treatment and was maintained for up to 24 h. Concomitantly, the lipid droplets in these cells became small and fewer in number. Immunostaining with a monoclonal antibody, A2, a specific marker for the lipid droplet capsule, demonstrated that detachment of the capsule from the lipid droplet occurs in response to CS application and that the period required for decapsulation is inversely related to the concentration of CS applied. The mechanism of CS-induced steroidogenesis is apparently different from that for ACTH, since intracellular cAMP levels were not increased in CS-treated cells. However, combined application with calphostin C, a PKC inhibitor, completely blocked the effect of CS on steroidogenesis, suggesting that activation of PKC may be responsible for the CS-induced steroidogenesis.

Penetration of levofloxacin into lung tissue after oral administration to subjects undergoing lung biopsy or lobectomy

STUDY OBJECTIVE

To evaluate the pulmonary tissue distribution of levofloxacin, the new once-daily fluoroquinolone, after a single 500-mg oral dose.

DESIGN

Open-label study.

SETTING

One pulmonary clinic and two university-affiliated teaching hospitals.

PATIENTS

Eighteen adults undergoing lung biopsy or lobectomy.

INTERVENTIONS

Levofloxacin plasma and lung tissue concentrations were determined by high-performance liquid chromatography with fluorescence detection. Lung tissue levofloxacin concentrations were corrected for blood contamination by measuring hemoglobin.

MEASUREMENTS AND MAIN RESULTS

After a single 500-mg oral dose, concentrations of levofloxacin in lung tissue consistently exceeded those in plasma at every time point over the 24-hour sampling period, with tissue:plasma penetration ratios of 2.02 (2-3 hrs), 5.02 (4-6 hrs), 5.13 (11-17 hrs), and 4.13 (22-25 hrs). The mean penetration ratio over the 24-hour sampling period was 3.95 (range 1.06-9.98). Lung tissue concentrations of levofloxacin also exceeded minimum inhibitory concentration values for most community-acquired respiratory tract pathogens over the 24 hours.

CONCLUSION

This study supports clinical evaluation of levofloxacin as once-daily oral therapy for community-acquired lower respiratory tract infections.

Effects of food and sucralfate on a single oral dose of 500 milligrams of levofloxacin in healthy subjects

The effects of food and sucralfate on the pharmacokinetics of levofloxacin following the administration of a single 500-mg oral dose were investigated in a randomized, three-way crossover study with young healthy subjects (12 males and 12 females). Levofloxacin was administered under three conditions: fasting, fed (immediately after a standardized high-fat breakfast), and fasting with sucralfate given 2 h following the administration of levofloxacin. The concentrations of levofloxacin in plasma and urine were determined by high-pressure liquid chromatography. By noncompartmental methods, the maximum concentration of drug in serum (Cmax), the time to Cmax (Tmax), the area under the concentration-time curve (AUC), half-life (t1/2), clearance (CL/F), renal clearance (CLR), and cumulative amount of levofloxacin in urine (Ae) were estimated. The individual profiles of the drug concentration in plasma showed little difference among the three treatments. The only consistent effect of the coadministration of levofloxacin with a high-fat meal for most subjects was that levofloxacin absorption was delayed and Cmax was slightly reduced (Tmax, 1.0 and 2.0 h for fasting and fed conditions, respectively [P = 0.002]; Cmax, 5.9 +/- 1.3 and 5.1 +/- 0.9 microg/ml [90% confidence interval = 0.79 to 0.94] for fasting and fed conditions, respectively). Sucralfate, which was administered 2 h after the administration of levofloxacin, appeared to have no effect on levofloxacin's disposition compared with that under the fasting condition. Mean values of Cmax and AUC from time zero to infinity were 6.7 +/- 3.2 microg/ml and 47.9 +/- 8.4 microg x h/ml, respectively, following the administration of sucralfate compared to values of 5.9 +/- 1.3 microg/ml and 50.5 +/- 8.1 microg x h/ml, respectively, under fasting conditions. The mean t1/2, CL/F, CLR, and Ae values were similar among all three treatment groups. In conclusion, the absorption of levofloxacin was slightly delayed by food, although the overall bioavailability of levofloxacin following a high-fat meal was not altered. Finally, sucralfate did not alter the disposition of levofloxacin when sucralfate was given 2 h after the administration of the antibacterial agent, thus preventing a potential drug-drug interaction.

Medical necessity for right heart catheterization

Because there are no definitive guidelines for performing right heart catheterizations or controlled clinical trials demonstrating medical benefit, the value and necessity of performing routine right heart catheterizations for coronary artery disease have been questioned. This Texas Medical Foundation Health Care Quality Improvement Program project was designed to ensure medical necessity and proper documentation of right heart catheterization when performed as part of a bilateral procedure. Medicare claims data were used to identify Texas facilities where rates of bilateral catheterizations suggested that right heart catheterizations were being performed routinely. Five facilities were found to have rates of bilateral procedures exceeding 70%. Suggested guidelines for performing right heart catheterizations were prepared by the Texas Medical Association Committee on Cardiovascular Diseases. These guidelines, together with the facility's data on its rate of right heart catheterizations, were presented by the Texas Medical Foundation to the staff of each facility. They were asked to examine their individual facility's procedures for ensuring medical necessity and to develop and implement process improvement plans. Medicare claims data were analyzed to determine the rates of bilateral catheterizations before and after the plans were instituted. The statewide rate of bilateral procedures decreased from 27.2% to 21.3% (p < 0.005). Rate reductions for 4 facilities implementing improvement plans were statistically significant (p < 0.001): at the 1st facility, the rate decreased from 74.3% to 25.0%; at the 2nd, from 85.0% to 21.0%; at the 3rd, from 76.7% to 17.7%; and at the 4th facility, from 85.4% to 42.9%. The rate for the facility not implementing an improvement plan increased from 86.4% to 89.1%. Reductions in rates of bilateral procedures at the 4 facilities suggest that many procedures previously performed were routine and not medically indicated. Presentation of data and practice guidelines to facilities may have contributed to their ability to improve processes.

A protective anti-peptide antibody against the immunodominant site of the A24 Cruzeiro strain of foot-and-mouth disease virus and its reactivity with other subtype viruses containing the same minimum binding sequence

A synthetic peptide vaccine of the general sequence Cys-Cys-(200-213)-Pro-Pro-Ser-(l41-158)-Pro-Cys-Gly(peptide A40), where the numbered residues refer to the VP1 sequence of foot-and-mouth disease virus (FMDV) strain A24 Cruzeiro, has previously been shown to elicit neutralizing and protective antibodies in guinea-pigs and cattle. To examine this immunogenic tract in more detail monoclonal antibodies (MAbs) were raised to this peptide. One such MAb C1.1, which recognized the homologous peptide, bound to native virus, neutralized infectivity in vitro and passively protected mice from challenge. Using overlapping dodecameric peptides the minimum binding 'footprint' of this MAb incorporated residues 149-154 which were respectively Gly-Ser-Leu-Ala-Ala-Arg. Since this 'footprint' occurs in several other A subtype strains of FMDV, the extent to which MAb C1.1 could cross-react was also examined. Using a liquid-phase competition ELISA, only viruses with a sequence that encompassed the same minimum binding 'footprint', namely A27 Cundinamarca Colombia/76, A Argentina/79, and A Venceslau Brazil/76 reacted with similar affinity against MAb C1.1. However, further serological examination of C1.1 with these viruses by indirect ELISA, in vitro neutralization and passive protection showed clear functional disparity. In contrast to the liquid-phase ELISA, the ability of C1.1 to react with electrostatically bound virus varied significantly depending on the subtype examined. Moreover, the capacity of this MAb to neutralize these subtypes showed wide divergence which was mirrored by the protection data.

The effects of recombinant human insulin-like growth factor (rhIGF)-1 and rhIGF-1/IGF binding protein-3 administration on rat osteopenia induced by ovariectomy with concomitant bilateral sciatic neurectomy

We compared the effect of administration of recombinant human insulin-like growth factor-1 (rhIGF-1) alone or the rhIGF-1/IGF binding protein-3 (IGFBP-3) complex on osteopenia in rats. Female Sprague-Dawley rats (8 months old) underwent combined ovariectomy and bilateral sciatic neurectomy (OVX-NX) or sham operation only. After 2 months, the OVX-NX animals were injected subcutaneously with rhIGF-1 alone or with rhIGF-1A IGFBP-3 equimolar complex for 4 weeks. The IGF-1 contents and dose were 0.3 mg/kg of body weight (BW) three times/week, 3 mg/kg of BW once/week, or 3 mg/kg of BW three times /week. At the end of the experiment, the 4th and 5th lumbar vertebrae (L4, L5) and the proximal tibiae were removed after tetracycline labeling, and histomorphometrical analyses were performed on undecalcified sections using Villanueva's staining. The cancellous bone volume at L5 significantly increased by thickening of the trabecular width in rats treated with the complex. However, the increase in the values at the proximal tibia was not significant. The bone formation rates (BFR/BS) in the lumbar vertebrae of rats treated with the complex three times a week at doses of 0.3 mg/kg of BW and 3 mg/kg of BW were both significantly increased but the parameter increase was less marked with the dose of 3 mg/kg of BW once/week. The BFR/BS did not increase significantly in animals treated with IGF-1 alone. These findings clearly demonstrated that the effect of systemically administered rhIGF-1 on bone formation was markedly potentiated when combined with IGFBP-3 in estrogen deficiency combined with reduced activity. The action of IGF-1 was less potent on the bone in paralyzed limbs. The action of rhIGF-1/IGFBP-3 on trabecular bone appeared to depend not only on the dose but also on the frequency of administration and the parts of the skeleton in rats.

Purification of dopamine neurons by flow cytometry

The heterogeneity and preponderence of other cell types present in cultures has greatly impeded our ability to study dopamine neurons. In this report, we describe methods for isolating nearly pure dopamine neurons for study in culture. To do so, the lipid-soluble dye, 1,1'-dioctadecyl-3,3,3'3'-tetramethylindocarbocyanine perchlorate (diI) was injected into the embryonic rat striata where it was taken up by nerve terminals and transported overnight back to the innervating perikarya in the ventral midbrain. Midbrain cells were then dissected, dissociated and separated on the basis of their (rhodamine) fluorescence by flow cytometry. Nearly all cells recovered as fluorescent positive (> 98%) were also immunoreactive for the dopamine specific enzyme tyrosine hydroxylase (80%-96%). Little contamination by other cells types was observed after labeling for specific neuronal and glial markers. Purified dopamine neurons continued to thrive and elaborate neuronal processes for at least 3 days in culture. Using this new model, it may now be possible to directly study the cellular and molecular processes regulating the survival and functioning of developing, injured and transplanted dopamine neurons.

Effect of organ perfusion on renal drug transport. Application to furosemide in the isolated perfused rat kidney

Angiotensin II was used as a probe to study the effect of changes in perfusate flow rate on the renal clearance parameters of furosemide in the isolated perfused rat kidney. Drug studies were performed in three rats with no angiotensin II present in the perfusate (treatment I) and in three rats with a 2.7 ng/min infusion of angiotensin II into the perfusate (treatment II). Furosemide was introduced into the recirculating perfusate at an initial concentration of 3.5 micrograms/ml and was assayed using HPLC. The protein binding of furosemide in perfusate was determined by equilibrium dialysis. Angiotensin II was found to have a dramatic effect on the renal hemodynamics, resulting in a 42% decrease in perfusate flow, a 27% decrease in GFR, and a 25% increase in filtration fraction. Values for the fractional excretion of glucose were very low and consistent, with or without angiotensin II (3.0-3.5%). Although the fraction unbound of furosemide was unchanged between treatments (0.770 for treatment I vs. 0.695% for treatment II), the renal and secretion clearances of furosemide were reduced by about 30% in the presence of angiotensin II. However, if the renal clearance (CLr) was corrected for free fraction (fu) and glomerular filtration rate (GFR) [ER = CLr/(fu.GFR)], there was no difference between the excretion ratio (ER) values of furosemide after the two treatments (29.0 for treatment I vs. 29.6 for treatment II). These results imply that the altered clearance parameters of furosemide are more likely the consequence of a reduction in functional nephron mass rather than a change in intrinsic secretory transport per unit mass of nephron.

Renal transport kinetics of chlorothiazide in the isolated perfused rat kidney

The effect of protein binding on the renal excretion of chlorothiazide was examined in the isolated perfused rat kidney. Drug studies were performed in three rats at 6.00% bovine serum albumin + 0% dextran and in three rats at 0.25% bovine serum albumin + 3.83% dextran. Chlorothiazide was introduced into the recirculating perfusate at an initial concentration of 100 micrograms/ml, and was assayed using high-performance liquid chromatography. Functional viability of the kidney was assessed by measuring the fractional excretion of sodium and glucose, and the glomerular filtration rate. The protein binding of drug in perfusate was determined by equilibrium dialysis. These experimental conditions resulted in an approximate 14-fold increase of percent free (from 5.3-72.0%), and a 3-fold increase of renal (from 1.03-3.30 ml/min) and secretion (from 1.01-2.83 ml/min) clearances. The data were best fitted by a model in which one Michaelis-Menten term was used to describe active transport, and secretion was dependent upon free concentrations of chlorothiazide in the perfusate. The maximum velocity of secretion (Vm = 85.6 micrograms/min) and Michaelis constant (Km = 2.1 micrograms/ml) of chlorothiazide was estimated using a nonlinear least-squares regression program. These results suggest that for compounds of low renal extraction, free drug concentrations are the driving force for carrier-mediated tubular secretion.

Renal transport kinetics of furosemide in the isolated perfused rat kidney

Direct quantitative data and corresponding theory are provided for the effect of protein binding on the renal transport of furosemide. Drug studies were performed with various combinations of bovine serum albumin and dextran. This resulted in a percent unbound (fu) of furosemide ranging from 0.785 to 85.8%. The corrected renal (CLr/GFR) and secretion (CLs/GFR) clearances of furosemide were observed to increase with percent free, but in a nonproportional manner. Plots of CLr/GFR or CLs/GFR vs. fu appeared to have a prominent y intercept as well as a convex ascending curve. In addition, the excretion ratio [ER = CLr/(fu . GFR)] was reduced from 60.8 to 8.72 as fu increased. Overall, the data were best fitted to a model in which two Michaelis-Menten terms were used to describe renal tubular transport, and secretion was dependent upon free drug concentrations in the perfusate. The results demonstrate that the renal mechanisms of furosemide excretion are more complex than previously reported and that active secretion may involve two different transport systems over the concentration range studied.