Biomedical subjects

J J Brown

Publications and source records attributed to J J Brown.

At least 19 recordsLinked to original sources

PubMed1995

Pneumococcal clearance function of the intact autotransplanted spleen.

OBJECTIVE: To determine if the venous drainage of the spleen into the portal circulation is essential for its ability to protect against encapsulated bacterial challenge. DESIGN AND INTERVENTIONS: Three groups of dogs were randomly assigned to undergo either sham laparotomy, splenectomy, or splenectomy with autotransplantation of the intact spleen into the pelvis and formation of vascular anastomoses to the iliac vessels. Two weeks post-operatively, the dogs received a sublethal intravenous injection of Streptococcus pneumoniae type 25. OUTCOME MEASURES: Bacterial clearances and inflammatory damage to the liver. Bacterial clearance of the autotransplanted spleen should be no different from that of a sham-operation spleen and significantly different from that of a splenectomized animal. In addition, immunologic function of the autotransplanted spleen should not differ from that of a sham-operation spleen in the degree of inflammatory damage to the liver. RESULTS: No differences in bacterial clearance function were found between the animals that had undergone sham laparotomy or splenic autotransplantation. However, bacterial clearance in the splenectomized animals was significantly impaired. Histologic examination of the liver 2 weeks after the bacterial challenge revealed high-grade inflammatory damage to the livers of splenectomized dogs, intermediate liver damage in dogs that underwent autotransplantation, and essentially no damage in dogs that underwent sham laparotomy. Autotransplanted spleens were essentially nonreactive, lacking actively proliferating germinal centers, whereas splenic tissue from sham-operation animals showed reactivity. CONCLUSION: Although bacterial clearance function is unchanged in autotransplanted spleens, this method still does not fully protect the liver from inflammatory damage.

Analysis of Variance↗

PubMed1995

Nephrogenic adenoma arising from a urethral diverticulum: magnetic resonance features.

Nephrogenic adenoma is a rare benign tumor of the urinary tract. Although its most commonly arises within the urinary bladder, this tumor may also occur within a urethral diverticulum. We report the magnetic resonance imaging (MRI) findings of a nephrogenic adenoma arising within a urethral diverticulum in a 43-year-old woman. MRI appears to be helpful in showing the anatomic extent of the lesion as well as differentiating it from other anterior vaginal wall masses.

Adenoma↗

PubMed1995

Dynamic contrast-enhanced MR imaging of the liver: parenchymal enhancement patterns.

A retrospective study of 164 patients undergoing dynamic contrast-enhanced magnetic resonance (MR) imaging was performed to assess hepatic parenchymal enhancement patterns and to correlate these patterns with hepatic function and disease. Rapid T1-weighted images were acquired before and after gadolinium administration. Hepatic enhancement patterns were analyzed blindly by two observers. Medical records were reviewed to document known liver pathology and liver function test results. A total of 72% of patients had homogeneous enhancement of the liver parenchyma; 28% had heterogeneous enhancement. Of the latter group, 61% of patients had enhancement conforming to segmental or lobar boundaries. Patients with heterogeneous enhancement patterns were more likely to have abnormal liver function test results and hepatic morphological abnormalities on their MR examinations than patients with homogeneous enhancement patterns. Heterogeneous hepatic enhancement on dynamic MR images is associated with a higher likelihood of liver disease and biochemical evidence of hepatic dysfunction than homogeneous enhancement.

Adult↗

PubMed1995

Large angle spin-echo imaging.

A study was undertaken to assess the use of excitation flip angles greater than 90 degrees for T1 weighted spin-echo (SE) imaging with a single 180 degrees refocusing pulse and short TR values. Theoretical predictions of signal intensity for SE images with excitation pulse angles of 90-180 degrees were calculated based on the Bloch equations and then measured experimentally from MR images of MnCl2 phantoms of various concentrations. Liver signal-to-noise ratios (SNR) and liver-spleen contrast-to-noise ratios (CNR) were measured from breathhold MR images of the upper abdomen in 16 patients using 90 and 110 degrees excitation flip angles. The theoretical predictions showed significant improvements in SNR with excitation flip angles > 90 degrees, which were more pronounced at small TR values. The phantom studies showed reasonably good agreement with the theoretical predictions in correlating the excitation pulse angle with signal intensity. In the human imaging studies, the 110 degrees excitation pulse angle resulted in a 7.4% (p < .01) increase in liver SNR and an 8.2% (p = .2) increase in liver-spleen CNR compared to the 90 degrees pulse angle at TR = 275 ms. Increased signal intensity resulting from the use of large flip angle excitation pulses with a single echo SE pulse sequence was predicted and confirmed experimentally in phantoms and humans.

Abdomen↗

PubMed1995

Hibernoma: MRI appearance of a rare tumor.

We report the features of a hibernoma on magnetic resonance (MR) imaging. The MR characteristics of this lesion were consistent with a complex lipid-containing mass. The mass did not suppress on short tau inversion recovery (STIR) imaging and was clearly not a simple lipoma. Hibernoma should be considered in the differential diagnosis of complex fatty masses.

Adipose Tissue, Brown↗

PubMed1995

Renal arteries: clinical comparison of three-dimensional time-of-flight MR angiographic sequences and radiographic angiography.

PURPOSE: To prospectively compare three magnetic resonance (MR) angiographic techniques in the renal arteries. MATERIALS AND METHODS: Twenty-five adult patients underwent three-dimensional time-of-flight MR angiography with three different sequences: conventional, tilted optimized nonsaturating excitation (TONE), and selective inversion-recovery rapid gradient-echo (SIR-RAGE). Fifteen also underwent radiographic angiography. Stenosis grade measured with each MR angiographic technique was compared with that measured with radiographic angiography by using correlation coefficients. Visible artery lengths with each MR angiographic technique were compared by using the Turkey method. RESULTS: Correlation between stenosis grades with each MR angiographic technique and with radiographic angiography was good (P < .01). Stenosis was correctly excluded with SIR-RAGE findings in six patients. Mean visible artery length was greatest with SIR-RAGE (P < .01). CONCLUSION: SIR-RAGE depicts a greater length of renal artery than does conventional MR angiography. TONE also improved depiction of distal arteries. Normal SIR-RAGE findings were highly predictive of normal arteries.

Adult↗

PubMed1995

Oxygen modulates surfactant protein mRNA expression and phospholipid production in human fetal lung in vitro.

We studied the effect of 20-95% O2 on mRNA levels for the surfactant-associated proteins (SP)-A, SP-B, and SP-C and [3H]choline incorporation into total phosphatidylcholine and type II cell-specific disaturated phosphatidylcholine (DPPC) in human fetal lung in culture. SP-A mRNA levels were increased by 25 and 39% in lung explants incubated in 70 and 95% O2, respectively, compared with levels in tissues incubated in 20% O2. SP-B mRNA levels were unaffected by O2, whereas SP-C mRNA levels were increased by 85, 102, and 115% in atmospheres of 35, 50, and 70% O2, respectively. [3H]choline incorporation into total phosphatidylcholine and DPPC were both increased in human fetal lung explants incubated in increased O2 concentrations compared with tissues incubated in 20% O2. Tissue levels of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) activity were not affected by O2 concentration, implying that the changes observed in SP mRNA levels and [3H]choline incorporation may not be mediated through alterations in PKA enzyme activity. These findings demonstrate that O2 regulates SP mRNA expression and phospholipid production in human fetal lung in vitro. We speculate that surfactant composition and possibly function may be regulated by O2 in human lung.

Choline↗

PubMed1995

MR imaging of the adrenal glands.

MR imaging provides an excellent morphologic depiction of normal and abnormal adrenal glands. Although CT scanning remains the primary imaging technique for detecting adrenal lesions, MR imaging is being used increasingly for characterization of adrenal masses. Chemical shift imaging is the most recent MR technique to be evaluated for distinguishing benign from malignant masses, and it appears to be the most reliable; however, further validation of this technique is necessary. In most clinical situations, adrenal lesions thought to be malignant on the basis of MR criteria should still be biopsied. MR imaging is also a useful problem-solving technique after equivocal CT scanning or sonography.

Adrenal Gland Diseases↗

PubMed1995

MR imaging of the retroperitoneum.

The diagnosis of retroperitoneal pathology has historically presented a challenge to physicians. The signs and symptoms of retroperitoneal diseases are myriad and often subtle. Cross-sectional imaging techniques have therefore had a major impact on retroperitoneal diagnosis. Computed tomography (CT) is currently the standard imaging technique for evaluating the retroperitoneum. Magnetic resonance (MR) imaging is also well suited for retroperitoneal imaging and has several advantages over CT. MR imaging is the preferred technique in patients with contraindications to iodinated contrast material due to renal dysfunction or allergy. It excels at evaluating the blood vessels, providing a reliable assessment of vessel patency, aneurysm, or dissection. The ability of MR imaging to acquire images without exposure to ionizing radiation facilitates imaging of obstetric and pediatric patients. The ability to acquire images in any plane is a distinct advantage for assessing the extent and origin of retroperitoneal pathology, although this can now be accomplished with spiral CT as well as MR imaging. The spatial resolution of CT is currently superior to MR imaging for most retroperitoneal studies, but this may change with continued technological advances such as improved phased array coil systems (Bidgood WD Jr, Schiebler ML. Retroperitoneum and mesentery. In: Ros PR, Bidgood WD Jr, eds. Abdominal magnetic resonance imaging. St. Louis: Mosby Year Book, 1993:310-47). Finally, MR imaging provides the flexibility to tailor each examination to the specific clinical question. With few exceptions, anything CT can do in the retroperitoneum, MR imaging can do as well or better.

Aortic Diseases↗

PubMed1994

Evaluation of fat saturation technique for T2-weighted endorectal coil MRI of the prostate.

The use of fat suppression has been found to improve tissue contrast and artifact control for performance of body coil MR imaging of the pelvis. The objective of this study was to evaluate whether use of fat suppression confers similar advantages when endorectal coil MR examinations are performed for staging of prostate cancer. Sixty consecutive patients were evaluated with conventional T1-weighted (TR 600, TE 20) and conventional and fat saturation proton density-/T2-weighted (TR 2500, TE 35/80) sequences. Thirteen of 60 patients underwent subsequent radical prostatectomy and constituted the study group for which conventional and fat suppressed long TR images were directly compared by three reviewers. Criteria assessed included the relative ability of each sequence to demonstrate zonal distinction, periprostatic venous plexus, fibromuscular stroma, capsule definition, seminal vesicle architecture, tumor conspicuity, capsular penetration and/or seminal vesicle tumor invasion, artifact control, and overall image quality. There was no statistically significant improvement in factors relating to image quality with use of fat saturation. In addition, depiction of the anatomic and pathologic features listed above was not significantly improved for fat-suppressed as compared with conventional endorectal coil images. It is concluded that fat saturation does not result in significant improvement over conventional T2-weighted images in endorectal MR imaging of the prostate.

Humans↗

PubMed1994

Effect of a null mutation of the c-fos proto-oncogene on sexual behavior of male mice.

Sexual behavior was observed in male mice that were homozygous for a null mutation of the c-fos proto-oncogene, as well as in heterozygous mutants and wild-type controls. The onset of mounting was slower and the subsequent mounting rate was significantly lower in homozygous mutants than in either group of controls. Even so, a similar percentage of males of each genotype achieved ejaculation, and ejaculation latencies were equivalent in these mice. Likewise, in males that intromitted, the intromission efficiency and the number of intravaginal thrusts/intromission were similar among the three genotypes. The nuclear protein product (Fos) of c-fos was visualized immunocytochemically in the brains of heterozygous male mice 1 h after they exhibited a series of mounts, with or without intromission, leading to an ejaculation. As in the male of several other rodent species, nuclear Fos immunoreactivity was augmented in neurons of limbic and midbrain regions thought to convey olfactory/vomeronasal and genital/somatosensory information, respectively, to the medial preoptic area following contact with an estrous female. One interpretation of our behavioral results is that in the absence of normal neuronal c-fos expression, sensory stimuli that impinge on the male brain during mating lose their ability to initiate a cascade of further gene transcription events that otherwise control the rate at which a male reorients towards and mounts an estrous female during an ejaculatory series. Alternatively, the c-fos null mutation may disrupt normal neural development, leading to a structural change that mediates the observed deficit in mounting capacity.

Amygdala↗

PubMed1994

Hepatic hemangiomas: a multi-institutional study of appearance on T2-weighted and serial gadolinium-enhanced gradient-echo MR images.

PURPOSE: To define the appearance of hepatic hemangiomas on T2-weighted and serial gadolinium-enhanced gradient-echo magnetic resonance (MR) images. MATERIALS AND METHODS: In four university hospitals, with 1.0- or 1.5-T MR imaging, T2-weighted and T1-weighted gradient-echo images were obtained in 66 adult patients before and at 1, 45, and 90 seconds and 10 minutes after injection of a gadolinium chelate. Hemangiomas were categorized as small (< 1.5-cm-diameter), medium (1.5-5.0-cm), and large (> 5.0-cm) tumors. RESULTS: In all, 154 hemangiomas were depicted (81 small, 56 medium, and 17 large tumors). All 154 lesions were hyperintense on T2-weighted images. Three patterns of contrast enhancement were observed: (a) uniform enhancement at 1 second (35 of 81 small lesions and no medium or large lesions), (b) peripheral nodular enhancement progressing centripetally to uniform enhancement (75 of all 154 lesions), and (c) peripheral nodular enhancement with persistent hypointensity centrally (44 of all 154 lesions, including 16 of 17 large lesions). CONCLUSION: Three patterns of enhancement of hemangiomas were observed. High signal intensity on T2-weighted images provided complementary information.

Adult↗

PubMed1992

Evaluation of two new gadolinium chelates as contrast agents for MRI.

Two new gadolinium chelates were investigated for potential use as tissue-specific contrast agents for magnetic resonance imaging. In vitro measurements of stability constants, octanol/water partition coefficients and relaxation times in solutions of water and human serum albumin (HSA) were performed with each new chelate and compared with gadolinium-diethylenetriamine pentaacetic acid, Gd(DTPA). Biodistribution studies and magnetic resonance imaging in rats were used to evaluate the new chelates in vivo. The stability constants (log K) of gadolinium-N,N''-bis(3-hydroxy-6-methyl-2- pyridylmethyl)diethylenetriamine-N,N',N''-triacetic acid, Gd(DTTA-HP), and gadolinium-1,7,13-triaza-4,10,16-trioxacyclooctadecane-N,N', N''-triacetic acid, Gd(TTCT), were determined to be 23.65 and 18.07, respectively. These can be compared to a literature value of 22.46 for Gd(DTPA). Octanol/water partition coefficients for both complexes showed they were more lipophilic than Gd(DTPA). Gd(DTTA-HP) exhibited a smaller relaxivity in water but a larger relaxivity in 4% HSA than Gd(DTPA). Gd(TTCT) exhibited a lower relaxivity than Gd(DTPA) in both water and 4% HSA. Both complexes showed similar biodistributions to Gd(DTPA) no carrier-added concentrations. Gd(DTTA-HP) had a greater percent change in signal intensity than Gd(DTPA) on T1-weighted spin-echo images in the heart, liver, and kidney. Percent change in signal intensity for Gd(TTCT) was lower than Gd(DTPA) in heart, liver, and kidney.

Acetates↗

PubMed1992

MR imaging of benign prostatic hypertrophy using a Helmholtz-type surface coil.

MR examinations of the prostate were performed on six healthy volunteers and 18 patients with well-documented symptomatic benign prostatic hypertrophy, using an organ-encompassing Helmholtz-type surface coil at 1.5 T. The healthy volunteers were also imaged with a standard circumferential body coil. The morphologic features and signal intensity characteristics of the prostate and adjacent structures were analyzed in the patient group. Several recognizable patterns of benign prostate hypertrophy were identified including bilaterally symmetrical nodules in the central gland, multiple central gland nodules, and a diffusely heterogeneous central gland without appreciable nodules. The peripheral zone was of moderate to high signal intensity on T2-weighted images, and was diffusely heterogeneous in 78% of patients. The false prostatic capsule, peripheral venous plexus, and seminal vesicles were also characterized. A good correlation was shown between prostatic glandular volume and prostate-specific antigen. Calculated signal-to-noise ratios (S/N) were significantly greater on images acquired with the Helmholtz-type receiver coil than on those acquired with the body coil. We conclude that the hyperplastic prostate gland has a variety of MR appearances, but that recognizable patterns are frequently seen. High resolution imaging with a Helmholtz-type surface coil provides excellent anatomical depiction of the prostate and adjacent structures.

Aged↗

PubMed1992

Distribution of hyaluronan in the mouse endometrium during the periimplantation period of pregnancy.

The tissue distribution of stromal hyaluronan (HA) in the periimplantation mouse uterus was studied histochemically using a biotin-labelled HA-binding complex from cartilage proteoglycan. HA is present around proliferating stromal cells in both the pregnant and pseudopregnant mouse uterus prior to their differentiation into the decidualized phenotype. Decidualization is accompanied by clearance of HA from the extracellular matrix (ECM). This clearing is part of an intrinsic developmental program of the differentiating deciduum. A specific embryonic signal from the implanting conceptus is not required for this phenomenon to occur, since a similar response could be induced in deciduoma produced by artificial stimulation of a receptive uterus. Clearing of HA from the antimesometrial stroma is consistent with the hypothesis that the HA-negative decidual cell may be involved in restricting the invasion of trophoblast cells during embryo implantation. Retention of HA within angiogenic regions of the decidua basalis implies a functional role for this molecule in placental vascularization.

Animals↗

PubMed1992

The dynamic provision of different energy substrates improves development of one-cell random-bred mouse embryos in vitro.

Preliminary observations showed that one-cell embryos from random-bred MF1 mice avoid cleavage arrest at the two-cell stage ('in vitro two-cell block') when cultured in modified M16 culture medium containing lactate and pyruvate but lacking glucose. The roles of lactate, pyruvate and glucose during preimplantation development of embryos from random-bred mice in vitro were therefore examined. When all three substrates were present continuously during culture, one-cell embryos arrested at the two- to four-cell stages. Improved development to the morula stage after 96 h in culture was obtained in media containing pyruvate alone, lactate and pyruvate, pyruvate and glucose, lactate pyruvate and glucose for the first 24 h, and medium containing lactate and pyruvate for the remaining 72 h. In a second experiment, embryos were cultured in medium containing pyruvate alone, lactate and pyruvate or pyruvate and glucose for the first 24 h, and lactate plus pyruvate medium for the second 24 h. Subsequent transfer to medium containing lactate, pyruvate and glucose supported the morula to blastocyst transition. These results show that developmental arrest in vitro can be overcome by changing the combination of energy substrates at different stages of preimplantation development.

Animals↗

PubMed1992

MR appearance of the normal and abnormal vagina after hysterectomy.

To define the MR appearance of the vagina after hysterectomy, we reviewed the MR examinations of 43 women who had undergone hysterectomy for a variety of benign and malignant indications. In eight of the patients, MR examinations showed a mass lesion involving the vagina. The masses included four recurrent primary gynecologic malignant neoplasms (one endometrial, one ovarian, and two cervical carcinomas) and four primary vaginal carcinomas. The remaining 35 patients had no evidence of vaginal disease. Of these 35 patients, the repaired vaginal apex, or vaginal cuff, was linear and smooth in appearance in 23 and partially obscured by surgical clip artifacts in seven. In the other five patients, the vaginal cuff had a nodular appearance that was indistinguishable from a vaginal mass on T1-weighted images. However, the vagina had a normal appearance in these patients on T2-weighted images, on which the low-signal-intensity layer of vaginal smooth muscle could be distinguished from the bright outer layer of connective tissue. In patients with recurrent vaginal tumors, the tumor was relatively high in signal intensity on T2-weighted images and obliterated the low-signal-intensity vaginal muscularis. Our experience shows that the normal posthysterectomy vagina may have a nodular appearance on T1-weighted images mimicking a vaginal mass. This appearance can be distinguished from that of a true vaginal mass on the basis of different signal intensity characteristics on T2-weighted images.

Adult↗

PubMed1991

Evaluation of congenital heart disease by three-dimensional magnetic resonance imaging.

This study was undertaken to compare electrocardiographically gated magnetic resonance imaging (MRI) to established imaging modalities in the detection of complex intra- and extracardiac morphologic defects. Twenty-three patients with congenital cardiac abnormalities were imaged by four methods: cardiac catheterization, echocardiography, two-dimensional (2D) transaxial MRI, and three-dimensional (3D) MRI surface reconstruction. Observers with experience in congenital cardiac disease diagnosis (two for echo, one for catheterization, two for 2D MR, and three for 3D MR) evaluated the images in a blinded fashion, and the results were analyzed with receiver operating characteristic (ROC) analysis. Overall, cardiac catheterization had the best diagnostic performance. The diagnostic value of routine 2D cardiac MR images and 3D MR reconstruction images were similar to that of echocardiography. All of the modalities performed poorly in the diagnosis of extracardiac defects and atrial septal defects.

Cardiac Catheterization↗