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Biomedical subjects

J C Andrews

Publications and source records attributed to J C Andrews.

At least 19 recordsLinked to original sources
PubMed1992

The exacerbation of symptoms in Menière's disease during the premenstrual period.

The pathophysiology of the characteristic episodic symptoms of vertigo, low-frequency hearing loss, and tinnitus in Menière's disease remains poorly understood. It is likely that the manifestation of this condition may be multifactorial and related to elements affecting the inner ear beyond the underlying pathology of endolymphatic hydrops. We have identified a subgroup of female patients with Menière's disease in which the symptoms of this disorder are correlated with the late luteal phase of the menstrual cycle (premenstrual period). Through audiometric and vestibular testing, we have documented these inner ear effects in six women. Although many hormonal effects occur during the premenstrual period, compartmental fluid redistribution within the body may be the most pertinent. Endolymphatic hydrops represents a fluid imbalance within the inner ear and, when combined with an additional fluid shift, may produce symptomatic dysfunction. Case histories demonstrating the correlation of the symptoms of Menière's disease and the premenstrual period will be presented along with theoretical mechanisms of pathophysiology.

Adolescent↗
PubMed1992

Sperm capacitation in the domestic cat (Felis catus) and leopard cat (Felis bengalensis) as studied with a salt-stored zona pellucida penetration assay.

The ability of domestic cat or leopard cat spermatozoa to penetrate zonae pellucidae (ZP) of salt-stored, domestic cat oocytes was examined as an assay for sperm capacitation. Ovarian oocytes were recovered after ovariectomy and matured in vitro for 18-36 h. Following removal of cumulus cells, the oocytes were used fresh, or stored (4 degrees C, 0.5-24 weeks) in a HEPES-buffered hypertonic salt solution. Electroejaculated, washed sperm (2-4 x 10(6) sperm/ml) were preincubated for 1.0 h (38 degrees C, 5% CO2 in air) and then co-incubated (2 x 10(5) sperm/ml) with fresh or stored oocytes for 6.0 h. Gametes were incubated in a protein-free, modified Tyrode's solution (TLP-PVA) or in the same medium containing 4.0 mg/ml bovine serum albumin (BSA; TALP-PVA). Treatments were compared for percentage ZP penetration (defined as sperm heads reaching more than halfway through the ZP) as an index of sperm capacitation. In both the domestic cat and leopard cat, there was no difference (P greater than 0.05) in sperm penetration of fresh ZP (domestic cat, 42.5 +/- 5.4%; leopard cat, 38.6 +/- 2.8%) or stored ZP (domestic cat, 32.4 +/- 4.2%; leopard cat, 27.6 +/- 2.3%). Sperm incubated in protein-free medium (TLP-PVA) were less capable (P less than 0.05) of ZP penetration (domestic cat, 14.6 +/- 5.9%; leopard cat, 7.9 +/- 3.0%) than sperm incubated in medium TALP-PVA containing BSA (domestic cat, 60.3 +/- 5.9%; leopard cat, 58.4 +/- 3.0%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

The use of 3-D dose volume analysis to predict radiation hepatitis.

Although it is well known that the tolerance of the liver to external beam irradiation depends on the volume of liver irradiated, few data exist which quantify this dependence. Therefore, a review was carried out of our clinical trial for the treatment of intrahepatic malignancies in which the dose of radiation delivered depended on the volume of normal liver treated. Three dimensional treatment planning using dose-volume histogram analysis of the normal liver was used for all patients. Nine of the 79 patients treated developed clinical radiation hepatitis. None of the patient related variables assessed were associated with radiation hepatitis. All patients who developed radiation hepatitis received whole liver irradiation, as all or part of their treatment, which produced a mean dose greater than or equal to 37 Gy. Dose volume histograms were used to calculate normal tissue complication probabilities based on parameters derived from the literature. The risk of complication was greatly overestimated among patients receiving a high dose of radiation to part of the liver without whole liver treatment. An estimation of model parameters based on the clinical results indicated a larger magnitude for the "volume effect parameter" than the literature estimate (n = 0.69 +/- 0.05 vs 0.32; p less than 0.001). Computation of the normal tissue complication probabilities using the larger value of n produced a good description of the observed risk of radiation hepatitis. These findings suggest that dose volume histogram analysis can be used to quantify the tolerance of the liver to radiation. The predictive value of this parameterization of the normal tissue complication probability model will need to be tested with liver tolerance and dose volume histogram data from an independent clinical trial.

Adult↗
PubMed1992

Design and testing of a high-flow autoperfusion catheter: an experimental study.

An autoperfusion catheter is similar to an angioplasty balloon catheter with side holes in the guide-wire lumen proximal to the balloon. When the balloon of the autoperfusion catheter is deployed and inflated in an artery, the guide wire is removed, and the hub of the guide-wire lumen is capped. The catheter then allows passive distal perfusion by using ambient pressure to drive blood into the guide-wire lumen, through the balloon, and out the end hole. This article discusses the requirements and constraints of a high-flow autoperfusion catheter, summarizes attempts to modify standard angioplasty catheters for use as an autoperfusion catheter, and describes the design and testing of a custom autoperfusion catheter capable of delivering approximately 3 mL/sec at physiologic pressures. In a model of canine acute renal artery occlusion lasting 90 minutes, the custom autoperfusion catheter provided marked protection from acute tubular necrosis compared with conventional percutaneous transluminal angioplasty catheters. The authors conclude that the high-flow autoperfusion catheter may be useful as a temporary stent in cases of rupture, dissection, or penetrating wounds involving large arteries.

Angioplasty, Balloon↗
PubMed1992

Early predictors of survival in symptomatic HIV-infected persons treated with high-dose zidovudine.

The survival times of 246 patients treated with high-dose zidovudine beginning in 1986 were obtained through November 1988. We analyzed clinical and laboratory predictors of survival as measured before initiation of therapy and during the first 32 weeks of therapy. In a multivariate proportional-hazards model, we found significant independent predictive abilities for four pretherapy measurements (AIDS versus ARC diagnosis, Karnofsky performance score, age, and hemoglobin) and four measurements made during therapy (change in log CD4 lymphocyte count from pretherapy to week 24, CD8 lymphocyte count at week 24, rate of decline of hemoglobin over the first 3 months of therapy, and rate of decline in white blood count over the first 6 months of therapy). The presence of three predictors measured during therapy that are statistically significant when controlled for changes in CD4 count suggests that the use of other measures in addition to CD4 counts may substantially improve the prediction of long-term survival based on early response of surrogate markers to therapy.

Drug Administration Schedule↗
PubMed1992

Three-dimensional CT scan reconstruction for the assessment of congenital aural atresia.

Major advances in medical computer graphics workstations have provided the capability to produce high quality three-dimensional image reconstructions from conventional thin-section computerized tomography (CT) scans with the ability to observe the imaged structure from any angle, with views and dimensions that are comparable to actual dissections. We have applied this technique to the temporal bone to assess congenital aural atresia in surgical planning for hearing reconstruction in six patients. The digital information produced by thin-section CT scanning allowed for the re-creation of multiplanar reformatted, shaded surface, and volumetric images. With this technique the surface landmarks of the temporal bone were readily visualized, the configuration of the atretic plate and middle ear in relation to the tegmen and glenoid fossa could be precisely assessed and the structure of the ossicular mass was easily analyzed. Most significantly, the facial nerve could be accurately and easily envisioned in its entire intratemporal course. Three-dimensional imaging is a highly desirable means for observing CT scan data to facilitate the surgical planning for correction of congenital aural atresia.

Adolescent↗
PubMed1991

Treatment of cancers involving the liver and porta hepatis with external beam irradiation and intraarterial hepatic fluorodeoxyuridine.

A Phase I/II clinical trial was designed for patients with malignancies of the liver and porta hepatis. This protocol employed three concepts: a) boost treatment to gross tumor within the liver for selected patients, determined by the dose-volume histogram (DVH) of the normal liver that would be irradiated by boost treatment; b) concurrent use of intraarterial hepatic 5-fluorodeoxyuridine (FdUrd) as a radiosensitizer; and c) hyperfractionation (1.5 Gy fractions given bid greater than 4 hr apart). This report describes the results of treatment of the first 33 patients entered onto this study, with a minimum follow-up of 1 year. Twenty patients received only whole liver irradiation (33 Gy). Thirteen patients were treated with whole liver irradiation (30 Gy) plus a 15 Gy (6 patients) or 30 Gy (7 patients) boost (total 45 Gy and 60 Gy to the tumor, respectively). Forty-eight percent of the evaluable patients (14/29) had an objective response, based on CT scan. The median duration of response was 8 months. The chief toxicities were fatigue, nausea, gastritis, and diarrhea, which were less than or equal to grade 2 in severity. Two patients developed mild radiation hepatitis which was treated successfully with diuretics. These data suggest that the treatment of intrahepatic malignancies can be guided by the concept of DVH analysis of the normal liver to allow the safe administration of doses of radiation that are potentially tumoricidal and are well above those that would be predicted to be tolerable for the whole liver.

Adenoma, Bile Duct↗
PubMed1991

Hepatobiliary toxicity of 5-fluoro-2'-deoxyuridine. Intra-arterial versus portal venous routes of infusion.

Biliary sclerosis remains the dose-limiting toxicity in a subset of patients receiving hepatic arterial (HA) floxuridine (FUDR) for the treatment of hepatic malignancy. To investigate the etiology of FUDR-associated sclerosing cholangitis, portal vein catheters were placed in mixed-breed hounds (N = 4) and connected to an implanted infusion pump system. Floxuridine 0.3 mg/kg/day was infused for 49 to 77 days each, as a continuous infusion. Cholangiograms were performed before and after infusion, and weekly liver function tests were obtained. The results were compared to dogs (N = 6) that received HA FUDR 0.3 mg/kg/d x 30 days, and dogs (N = 5) that received HA saline for 100 days. Elevation in the serum glutamic pyruvic transaminase and alkaline phosphatase, indistinguishable from the HA group, was seen in all four dogs with portal vein infusion. Maximum bilirubin levels ranged from 0.6 to 3.0 (mean 1.7), compared to a range of 6.4 to 28 (mean 13.4) for the HA dogs. Cholangiograms demonstrated hepatic volume loss consistent with hepatocellular injury, but no biliary sclerosis. These data suggest that sclerosing cholangitis resulting from intra-arterial infusion of FUDR is unlikely to be due to metabolites of the drug excreted in the bile, but due to direct toxicity to the biliary tree.

Animals↗
PubMed1991

Nonneoplastic enhancing lesions mimicking intracanalicular acoustic neuroma on gadolinium-enhanced MR images.

The authors describe five patients with nonneoplastic lesions of the facial and/or vestibulocochlear nerves that demonstrated focal enhancement within the internal auditory canal on magnetic resonance (MR) images. MR and surgical findings for four patients with unilateral sensorineural hearing loss and one with Ramsay Hunt syndrome were reviewed. Three patients with hearing loss underwent surgical exploration and decompression of the internal auditory canal. The MR findings in all four patients with hearing loss were similar: Focal enhancement of the internal auditory canal was depicted on postcontrast T1-weighted images. Nonneoplastic lesions of the seventh and eighth cranial nerves may show focal enhancement on MR images, which mimics the appearance of a small intracanalicular neuroma. This potential for misdiagnosis may have important therapeutic implications.

Cranial Nerve Diseases↗
PubMed1991

The measurement and manipulation of intralabyrinthine pressure in experimental endolymphatic hydrops.

Three to four months after unilateral surgical ablation of the endolymphatic duct and sac, endolymphatic and perilymphatic pressures were measured in both the normal and hydropic ears of 11 guinea pigs. In normal ears, endolymphatic pressure always approximated perilymphatic pressure. Endolymphatic pressure exceeded perilymphatic pressure in all ears with hydrops, except one in which these pressures were equal. The effect of postural inversion on inner ear pressures were studied in both normal and hydropic inner ears. Normal ears showed endolymphatic and perilymphatic pressure to rise equally during this maneuver. In hydropic ears, the difference between endolymphatic and perilymphatic pressure was notably reduced from measurements obtained in the prone position. This study indicates that an alteration in pressure regulation within the inner ear may be important in the pathogenesis and manifestation of experimental endolymphatic hydrops in the guinea pig. Physiologic mechanisms and clinical implications of these results are described.

Animals↗
PubMed1991

Malignant nerve sheath tumors of the head and neck: a combined experience from two university hospitals.

Malignant schwannoma is an aggressive neoplasm whose cell of origin and histologic characteristics remain controversial. Despite advances in diagnostic techniques, the natural history of this tumor remains uncertain. The charts of all patients with malignant schwannoma who were treated at the UCLA Center for the Health Sciences and the University of Iowa Hospital and Clinics were retrospectively reviewed. Sixteen patients received surgery and radiotherapy in combination or as sole therapy. Irrespective of treatment modality, prognosis was poor with an overall survival of 15%. Recent advances in imaging and histologic techniques that assist in establishing the diagnosis and delineating tumor location are discussed. In addition, the literature pertaining to malignant schwannoma of the head and neck is reviewed.

Adolescent↗
PubMed1990

Long-term central venous access with a peripherally placed subcutaneous infusion port: initial results.

A new subcutaneous infusion port and catheter system for long-term central venous access, designed to be implanted in the interventional radiology suite, was evaluated. In 35 patients, a 5-F polyurethane catheter was placed in the superior vena cava via the axillary or brachial venous approach under fluoroscopic guidance. A 2.5 X 2.5-cm2 subcutaneous pocket was dissected for the port. The port was then connected to the catheter, and the incision was closed. Ports have been implanted for a total of 5,290 patient days (5-307 days for an individual patient). Blood transfusion, bolus drug administrations, and 5-day outpatient chemotherapy infusions were successful in all attempts. Blood sampling was successful in 98.9% of attempts. No infectious or thrombotic complications were encountered. Acceptance of this device by patients and nursing staff has been excellent. The initial results indicate that this peripherally placed port is a viable alternative for patients requiring long-term central venous access.

Adult↗
PubMed1990

Effects of moderating variables on product managers' behavior.

This study examined the moderating effects of role autonomy, need for affiliation, and tolerance of ambiguity on the relationships between role pressures of conflict and ambiguity and personal outcomes of job satisfaction, job-related tension, and perceived performance. Data from 166 product managers indicate that role autonomy and need for affiliation do have moderating effects unlike tolerance of ambiguity. Managerial implications are discussed.

Adult↗
PubMed1989

Parotitis and facial nerve dysfunction.

Paralysis of the facial nerve in association with suppurative parotitis is rare, with only ten previously reported cases. In some situations, inflammation surrounding a benign neoplasm accounted for the observed paralysis. In this article, three new cases of parotitis with associated facial nerve dysfunction are described, none of which was associated with a neoplasm. In one, an occult abscess was present and in another an aggressive necrotizing process was seen. The treatment of this disease should initially be conservative management with high doses of wide-spectrum antibiotics. In the majority of cases, resolution of the facial paralysis should follow. However, persistence of a parotid mass with continued facial palsy mandates surgical exploration to exclude the presence of an underlying neoplasm.

Adult↗
PubMed1989

Capacitation of hamster spermatozoa with the divalent cation chelators D-penicillamine, L-histidine, and L-cysteine in a protein-free culture medium.

By using a chemically defined (protein-free) culture medium that supports sperm viability but not capacitation or the acrosome reaction, we have determined that hamster spermatozoa can be chemically capacitated in vitro by the divalent cation chelators D-penicillamine, L-histidine, and L-cysteine in the absence of bovine serum albumin (BSA). Washed cauda epididymal spermatozoa were preincubated (1-2 x 10(6) sperm/ml) for 3, 4, or 6 hr at 37 degrees C in 5% CO2 in air. The basic culture medium used for sperm preincubation and for sperm:egg coincubation was a modified Tyrode's solution (protein-free) containing 10 mM sodium lactate, 100 microM sodium pyruvate, and 1.0 mg/ml polyvinylalcohol (TLP-PVA). Sperm viability was maintained in all preincubation and coincubation media with PHE (20 microM D-penicillamine, 100 microM hypotaurine, and 1.0 microM epinephrine). The low control sperm preincubation medium consisted of TLP-PVA. In some cases the high control preincubation medium also contained 3 mg/ml BSA (TALP-PVA). The experimental preincubation medium was TLP-PVA with additional D-penicillamine (125 or 500 microM), or L-histidine (10, 100, or 1,000 microM) or L-cysteine (25, 75, or 125 microM). After preincubation, sperm were coincubated (2 x 10(4) sperm/ml) with cumulus-free hamster eggs in TALP-PVA +/- additional D-penicillamine, L-histidine, or L-cysteine for 1.5 hr, fixed, and evaluated for percent egg penetration as an index of sperm capacitation. The results demonstrate that hamster spermatozoa can be chemically capacitated in vitro with D-penicillamine (500 microM: range of mean penetration values, 53.6%-84.3%), L-histidine (100 microM: range of mean values, 24.8%-56.3%) or L-cysteine (75 microM: 51.3%) in the absence of exogenous protein.

Animals↗