PubMed Health⌕ Search

Biomedical subjects

J T Watson

Publications and source records attributed to J T Watson.

At least 19 recordsLinked to original sources
PubMed1992

Preliminary studies of 6 beta-hydroxydexamethasone and its importance in the DST.

The role of the metabolites of dexamethasone (DEX) in the dexamethasone suppression test (DST) has never been fully elucidated. We report here our preliminary studies of 6 beta-hydroxydexamethasone (6 OH-Dex), a known metabolite of DEX, on the hypothalamic-pituitary-adrenal (HPA) axis of the rat; its activity in the most commonly used radioimmunoassay for plasma DEX; and its plasma concentrations in a normal human subject during the standard 1.0 mg DST. Six OH-Dex administered subcutaneously to rats at a dose of 1 mg/kg was able to completely suppress corticosterone production for at least 3 hr. In the IgG Corp. radioimmunoassay for plasma DEX, 6 OH-Dex was moderately cross-reactive yielding a 50% cross-reactivity of 10%. Gas chromatographic coupled mass spectroscopic analysis of human plasma samples, obtained 12 to 20 hr after the oral ingestion of 1.0 mg DEX, demonstrated similar plasma concentrations for both the parent compound and the 6-hydroxyl metabolite. The relevance of these findings, particularly to pharmacokinetic studies of the DST, is discussed.

Animals↗
PubMed1992

Complex mixture analysis based on gas chromatography-mass spectrometry with time array detection using a beam deflection time-of-flight mass spectrometer.

A beam deflection time-of-flight mass spectrometer was developed in conjunction with an integrating transient recorder to provide time array detection, permitting high mass spectral scan file acquisition rates for complex mixture analysis by capillary gas chromatography-mass spectrometry (GC-MS). Results are presented for the analysis of a urinary organic acid mixture by GC-MS at a scan file acquisition rate of 10 scan files per second (sf/s), showing the advantages of such data collection in the deconvolution of partially resolved components. The reconstructed total ion current (RTIC) chromatogram available from data acquired at this scan file generation rate is shown to be comparable to the profile obtained from a flame ionization detector in representing the chromatography performed under identical experimental parameters. The RTIC chromatogram available from the database obtained at 10 sf/s is compared with that available from a database obtained at 1 sf/s, the latter representing that scan rate typically used with most GC-MS instruments. The advantages of the higher scan file acquisition rate in representing the chromatographic profile and in allowing mass spectral data to be obtained for components in the complex mixture that are unresolved chromatographically are discussed.

Acids↗
PubMed1992

Testicular masculinization of vocal behavior in juvenile female Xenopus laevis reveals sensitive periods for song duration, rate, and frequency spectra.

In Xenopus laevis, adult males but not females produce courtship songs comprised of rapid trills. Two experiments were conducted to determine whether male-typical singing could be induced in females. At 6 different juvenile stages, male and female frogs were gonadectomized and implanted with testes, grown to sexual maturity, and tested for vocal behavior. All frogs with functional testicular implants sang; females sang as much as males. The frequency spectra of the clicks within trills were fully masculinized in females implanted at PM0, PM1, and PM2. There were deficiencies in song quality in females implanted late in juvenile life. Females receiving testis implants at PM3, PM4, and PM5 did not produce clicks with masculine spectral qualities. In a concurrent experiment, adult males and females were gonadectomized and implanted with testes or silicone tubes containing testosterone propionate. When tested for vocal behavior 10 to 15 months after implantation, 8/10 androgen-treated males, 3/12 androgen-treated females, 5/5 testes-implanted males, and 2/4 testes-implanted females sang. The females that did sing spent much less time singing than males. The click rates of females were uniformly slower than males and no female produced clicks with a masculine frequency spectrum. Thus, testicular secretions can induce male-typical singing in females until late in juvenile development. However, females exhibit a progressive decline in vocal potential with increasing age, culminating in an almost complete loss of singing ability by adulthood.

Acoustic Stimulation↗
PubMed1992

Dirofilaria immitis: do filarial cyclooxygenase products depress endothelium-dependent relaxation in the in vitro rat aorta?

Endothelial cells modulate the function of their underlying smooth muscle. Thus, altered endothelial behavior could be important in the pathogenesis of vascular and lymphatic diseases, including human and animal filariasis. Endothelium-dependent relaxation is depressed in both in vivo canine femoral artery of dogs infected with Dirofilaria immitis and in vitro rat aorta exposed to adult D. immitis. The experiments reported here were designed to determine if filarial cyclooxygenase products could depress endothelium-dependent relaxation in vitro. Pretreatment of the parasites, but not the vascular ring, with either indomethacin or aspirin, prevented filarial-induced depression of relaxation. Analysis of heartworm-conditioned medium by gas chromatography--mass spectrometry revealed two peaks in the biologically active medium that were not present in the control. One peak had a retention time and chromatographic profile characteristic of derivatized PGD2 standard, and the other was not identified. Incubation of the vascular ring with PGD2 mimicked filarial-induced depression of endothelium-dependent relaxation at low, but not high, concentrations of acetylcholine. Thus, filarial PGD2 may be involved in altered endothelium-dependent relaxation seen in heartworm-infected dogs.

Acetylcholine↗
PubMed1992

A model for evaluating the strength of bones lengthened by distraction osteogenesis.

In an effort to evaluate the strength of bones lengthened by distraction osteogenesis, a modified Ilizarov-type external fixator was applied to the right tibiae of five adult mongrel dogs. Diaphyseal corticotomies were performed, and distraction (lengthening) was carried out at a rate of approximately 1 mm per day for 20 days. After completion of the lengthening, the animals were killed, the fixators were removed, and the right and left tibiae were harvested and stripped of soft tissue. The ends of all harvested bones were fixated in polymethylmethacrylate to allow testing on a materials testing system (MTS) machine. Testing under torsional loads was performed on the MTS machine (50 degrees maximum angle of rotation at ten seconds) until failure. The right tibiae were lengthened an average of 12 mm (range, 7-15 mm). The slopes of the linear portion of the torque versus rotation curves were determined. A comparison of slopes revealed a mean change in stiffness between test and control bones of 20.32% (range, 0.64%-40.5%). All tibiae exhibiting mature regenerate bone demonstrated stiffness greater than the matched controls (range, 0.64-24.09% stiffer). Four of five dogs had problems with proximal and distal ring impingement. This study presents a reproducible model for evaluating the strength of bones lengthened by distraction osteogenesis. The lengthened bones that exhibited bony or mature regeneration were as strong as the control bones.

Animals↗
PubMed1991

Highly resolving two-dimensional gels for protein sequencing.

Two-dimensional (2D) PAGE, using carrier ampholytes for the first-dimension separation, has provided a tool for the simultaneous analysis of cellular proteins. To extend the utility of 2D PAGE to the preparative level, we have investigated the use of immobilized pH gradients (IPG) for the first-dimension separation. The results we have obtained indicate that as much as 1 mg of cellular protein can be loaded onto a single IPG gel without loss of resolution. Mutant polypeptides previously detected in carrier ampholyte-based 2D gels were equally detectable in IPG-based 2D gels. With IPG gels several hundred cellular polypeptides can be isolated, from as few as 10 gels, in sufficient amount for sequencing with current sequencing technology. We therefore conclude that IPG greatly enhances the prospects for the large-scale sequencing of cellular proteins for the development of 2D gel-related protein data bases and for the identification of new polypeptide gene products, with the attendant implications for a genome sequencing effort.

Amino Acid Sequence↗
PubMed1991

Derivatization of peptides to enhance ionization efficiency and control fragmentation during analysis by fast atom bombardment tandem mass spectrometry.

Novel and simple procedures for preparing ethyl-triphenylphosphonium derivatives of peptides are described. These procedures allow an ethyl-triphenylphosphonium moiety to be selectively attached to either the N- or C-terminus. The resulting derivatives contain a positive charge at a fixed position and have significant hydrophobic character. Modification of peptides by these chemical methods significantly enhances the efficiency of fast atom bombardment ionization, especially of hydrophilic peptides. Moreover, upon collisionally activated dissociation, the derivatized peptides generate a predictable series of sequence ions from either the C-terminus or the N-terminus, depending on the location of the ethyl-triphenylphosphonium moiety.

Amino Acid Sequence↗
PubMed1991

A new model to assess tibial fixation in knee arthroplasty. I. Histologic and roentgenographic results.

A model to assess tibial fixation in knee arthroplasty is described. Eighteen mongrel dogs were implanted with a right tibial hemiarthroplasty. Implantation was of a press-fit, smooth implant (eight dogs) or a titanium alloy beaded device (ten dogs). Animals were studied at six, 12, 18, and 24 weeks. Roentgenographic and histologic analysis was performed for all implants. All animals were ambulatory. Roentgenographically, smooth implants showed progressive radiolucencies with increasing trabecular sclerosis under the implants. These changes were less prominent under the porous implants. Histologically, fibrous interfaces were identified focally under all implants but were thicker under smooth devices. Eighteen- and 24-week specimens showed substantial ingrowth into the porous pegs but minimal ingrowth into the porous plateau. Concurrent histologic and biochemical evaluation in dogs demonstrates the possible fate of implants in knee arthroplasty in human beings. As has been observed, histologic analyses suggest that clinically satisfactory results do not constitute evidence of stabilization by bone ingrowth.

Animals↗
PubMed1991

A new model to assess tibial fixation. II. Concurrent histologic and biomechanical observations.

A tibial hemiarthroplasty model was designed to allow concurrent histologic and biomechanical analysis of the tibial implant-bone interface. In this study, micromotion was visually observed at the implant-bone interface of cemented and uncemented implants. Six dogs had staged bilateral implantation. Biomechanical analysis of three- and 12-month specimens was correlated with histologic analysis of the same specimen. Load transmission involved compression of trabecular bone and fibrous tissue at the interface. Failure of the interface occurred through cyclic fatigue and microfracture of trabeculae. Micromotion was seen at all interfaces, porous or smooth, cemented or uncemented. Displacement was greatest under an eccentrically loaded plateau. Micromotion at ingrown and cemented interfaces was because of trabecular compression. Uncemented smooth devices and uncemented porous devices with fibrous fixation of the plateau appeared unstable. The cemented implants and a single uncemented implant studied at 12 months showed no interface micromovement. The absence of micromovement in the uncemented implant was associated with subsidence and with ingrowth of 30% into the porous peg and porous plateau.

Animals↗
PubMed1990

Renaissance of gas chromatography-time-of-flight mass spectrometry. Meeting the challenge of capillary columns with a beam deflection instrument and time array detection.

This report describes the use of a unique beam deflection time-of-flight mass spectrometer to address some of the demands made on mass spectrometry by new developments in high-resolution capillary column gas chromatography. An integrating transient recorder is used in combination with this beam deflection time-of-flight instrument to apply the concept of time array detection in capturing all of the mass spectral information available from the ion source, thereby greatly enhancing the signal-to-noise ratio quality of the mass spectral data. The applicability of the time array detection approach to gas chromatography-mass spectrometry is demonstrated in the context of an analysis of the standard Grob mixture for assessing performance of capillary column chromatography. During analysis of the Grob mixture by gas chromatography-mass spectrometry, mass spectra were recorded at a rate of 20 scan files per second. The data indicate that this rate of mass spectral scan file generation is adequate to provide a suitable data base for reconstruction of the chromatographic profile. In addition, the effective scan rate is high enough that there is no distortion in the relative peak intensities throughout the individual mass spectra of components regardless of the relatively high dynamic changes in partial pressure of the analyte as reflected by the sharp peaks in the chromatographic profile. The experimental results indicate that the beam deflection time-of-flight mass spectrometer can provide mass spectra at a scan file generation rate much higher than that possible with the conventional quadrupole or magnetic sector mass spectrometer, but at comparable detection limits.

Chemical Phenomena↗
PubMed1990

Application of time array detection to capillary column gas chromatography/conventional time-of-flight mass spectrometry.

The technique of time array detection (TAD) is designed to take advantage of the high spectral generation rate available in time-of-flight (TOF) mass spectrometry. In TAD, a number of successive TOF arrival time transient signals are summed to produce each recorded mass spectrum. The TOF/TAD technique offers significant improvements over conventional scanning mass spectrometers for the analysis of capillary GC effluents. Up to 20 mass spectra per second were generated to demonstrate the accurate reconstruction of the chromatographic profile and the lack of mass spectral distortion despite the rapidly changing analyte concentration. Varying the number of TOF transients per recorded spectrum allows the chromatography to be optimized for speed of analysis without sacrificing chromatographic resolution or detection limits. Components of charcoal lighter fluid were chromatographically separated in less than 4 min with quality mass spectra obtained for each eluent.

Gas Chromatography-Mass Spectrometry↗
PubMed1990

Sexual dimorphism in the avian brain is not limited to the song system of songbirds: a morphometric analysis of the brain of the quail (Coturnix japonica).

Nissl-stained sections of adult male and female quail brains were examined for possible sex differences in the sizes of nuclei implicated in reproductive function or known to be dimorphic in songbirds, including nucleus magnocellularis preopticus, two additional preoptic nuclei, n. ventromedialis hypothalami, n. taeniae, n. hypoglossus and n. commissurae pallii. There was a significant sex difference in the volume of one of the preoptic nuclei (which was 38% larger in males), known to be a critical area for the hormonal activation of male copulatory behavior, which cannot be accounted for by overall brain size dimorphism. It is suggested that this nucleus be named nucleus preopticus medianus (POMn). There was no sex difference in the average neuronal density or cross-sectional soma area within POMn; rather, the male POMn consists of a greater total number of neurons than the female POMn. No other nuclei that were measured were dimorphic in volume, including n. hypoglossus. There was small but significant lateral asymmetry in n. commissurae pallii, the left side being about 10% larger in volume.

Animals↗
PubMed1990

Determination of plasma dexamethasone by chemical oxidation and electron capture negative ionization mass spectrometry.

A quantitative assay for dexamethasone in human plasma is described as based on methodology employing electron capture negative ionization mass spectrometry (ECNI/MS). The unique feature of this assay is the sample preparation involving chemical oxidation which transforms dexamethasone to a highly electrophilic species while not significantly affecting the electrophilic character of the biochemical matrix, thereby permitting selective and sensitive detection of the analyte. Optimized chemical procedures and instrumental parameters are described for the detection of oxidized dexamethasone. Finally, the newly developed methodology, based on gas chromatography/mass spectrometry (GC/MS) with ECNI, is evaluated by comparison with a conventional GC/MS assay using electron impact of an 11,17,21-tris-trimethylsilyl ether 20-enol-trimethylsilyl ether derivative of dexamethasone and with a radioimmunoassay in the analysis of pooled samples of human plasma containing widely varying concentrations of the drug as obtained from patients at different stages of the dexamethasone suppression test.

Dexamethasone↗
PubMed1990

The prophylactic use of octreotide in a patient with ovarian carcinoid and valvular heart disease.

This case report describes the use of octreotide, a long-acting somatostatin analogue, in the management of a patient with an ovarian carcinoid tumour and severe cardiac valvular disease. This patient underwent laparotomy and tumour resection without complication. Anaesthesia was induced with midazolam, fentanyl, and vecuronium, and maintained with isoflurane as well as additional fentanyl and vecuronium. However, we feel that it was the use of octreotide that prevented a life-threatening crisis intraoperatively, and recommend its use in patients with carcinoid syndrome undergoing anaesthesia and surgery.

Anesthesia, Inhalation↗
PubMed1990

Circulating estradiol and the activation of male and female copulatory behavior in Japanese quail (Coturnix japonica).

Previous experiments using systemic and preoptic area (POA) hormone treatments have shown that aromatization of testosterone (T) to estrogen (E) is essential for activation of male-typical copulatory behavior in castrated male Japanese quail (Coturnix japonica). Two experiments were conducted to determine whether circulating estrogen levels characteristic of normal intact males are high enough to activate male-typical or female-typical copulatory behavior. In Experiment 1, blood samples were drawn every 4 hr from groups of sexually active male quail housed under a 16L:8D light-dark cycle, and assayed for estradiol (E2) concentration. The mean +/- SEM serum E2 was 54.2 +/- 3.6 pg/ml, and no daily cycle in serum E2 was seen. The males were then tested for sexual behavior; 88% mounted females, and 23% crouched when mounted by males. In Experiment 2, 51 males were castrated and implanted with Silastic tubes containing estradiol benzoate (EB) and/or cholesterol designed to produce five different levels of serum E2, then tested for male- and female-typical copulatory behavior and bled. The serum E2 in EB-implanted quail which mounted (253 +/- 30 pg/ml) was significantly higher than that of intact quail in Experiment 1, and only 10.2% of intact males had serum E2 as high as the minimum associated with mounting in EB-implanted males. These results show that serum E2 levels in intact males are not high enough to support male-typical copulation, and that aromatization in the POA to produce locally high E2 levels may be required. In addition, it was found that the threshold serum E2 to elevate receptivity significantly was 3.6 times the intact male level, and only slightly higher than serum E2 reported for intact females. Thus the lack of receptivity in intact males is probably due to insufficient circulating E2, and the male is not defeminized with respect to sensitivity to E2 for activation of receptivity.

Animals↗
PubMed1990

Mycobacterial prepatellar bursitis.

Prepatellar bursitis secondary to infection with an atypical mycobacterium developed in an 88-year-old man. A review of all previously reported cases in the English literature indicates tuberculosis is important in the differential diagnosis of prepatellar bursitis.

Aged↗