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Biomedical subjects

J C Andrews

Publications and source records attributed to J C Andrews.

At least 73 records · Page 4Linked to original sources
PubMed1991

Middle cranial fossa transtemporal approach to the intrapetrous internal carotid artery.

Diseases involving the proximity of the internal carotid artery at the skull base require identification of this vessel in the temporal bone to gain vascular control for any maneuver in its vicinity. This article details the technique of surgical dissection and exposure of the internal carotid artery within the skull base through a transtemporal middle cranial fossa approach. The anatomic landmarks important in utilizing this procedure include the greater superficial petrosal nerve, the mandibular branch of the trigeminal nerve, and the middle meningeal artery. With this approach, the internal carotid artery can be followed throughout the carotid canal and beyond the formen lacerun to the region of the cavernous sinus. The indications and limitations of this procedure are described and several clinical applications are provided.

Journal Article↗
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↗
PubMed1989

Maintenance of hydrostatic pressure gradients in the membranous labyrinth.

In normal guinea pig ears, hydrostatic perilymphatic pressure is equal to endolymphatic pressure. Alterations of perilymphatic pressure induced, for example, by laceration of the round window membrane are transmitted immediately to the endolymphatic compartment, probably via Reissner's membrane. In guinea pigs with experimental endolymphatic hydrops, however, pressure gradients between the endolymph and perilymph remained preserved after rupture of the round window membrane. This is considered as further evidence that after long-standing distention of Reissner's membrane the membranous labyrinth loses its ability to equalize endolymphatic and perilymphatic pressure.

Animals↗
PubMed1989

Steady-state arterial and hepatic venous plasma concentrations of 5-bromo-2'-deoxyuridine and 5-iodo-2'-deoxyuridine in animals--drugs which are subject to both splanchnic and extra-splanchnic elimination.

We have previously shown that 5-fluorouracil (FUra) in humans obeys Michaelis-Menten elimination kinetics. In this article we show that the related bromine and iodine-containing analogs in animals obey similar kinetics. Steady-state arterial (CssA) and hepatic venous plasma (CssV) concentrations of 5-bromo-2'-deoxyuridine (BrdUrd) are reported for 7 rabbits given 5 different infusion rates of BrdUrd and 5 dogs given 4 or 5 different infusion rates of BrdUrd. Steady-state arterial and hepatic venous plasma concentrations of 5-iodo-2'-deoxyuridine (IdUrd) are reported for 5 rabbits and 2 dogs given 5 different infusion rates of IdUrd. Each set of data could be fitted by a nonlinear least squares method to the equation: (equation; see text) where Vm/Q is the maximum difference, (CssA) - (CssV), and Km is the Michaelis constant. The estimated parameter Vm/Q and Km are compared for the two drugs and different species and also with the same parameters derived in the same manner from previously published data on fluorouracil in 8 cancer patients. The infusion rate needed to saturate the splanchnic elimination system (Rs in mumol/kg/min) was also estimated. For BrdUrd the mean value of Rs in the rabbit, namely 1.23, and in the dog, namely 1.25 mumol/kg/min are essentially the same.

Animals↗
PubMed1989

Combination chemo-radiation therapy for jaundice due to focal malignant obstruction of the major bile ducts.

Twenty patients with focal malignant obstruction of the major bile ducts (6 cholangiocarcinoma, 8 colorectal, 3 hepatoma, 2 unknown primary, and 1 gastric cancer) were treated on a protocol examining the toxicity and efficacy in relieving jaundice of external beam radiation therapy (4500 cGy in 300 cGy fractions) combined with continuous hepatic arterial (15 patients) or peripheral venous (5 patients) fluorouracil infusion. Toxicity of this regimen consisted of anorexia with mild nausea and vomiting in 55% of patients and gastric ulceration (responsive to medical management) in 15% of patients. One patient exhibited transient grade 2 hepatic toxicity and one had asymptomatic grade 4 leukopenia. Of 14 patients treated without prior biliary drainage, 8 exhibited a decrease in bilirubin levels from a mean of 14.5 mg/dl to 1.5 mg/dl. Four of six patients with biliary drainage catheters at the start of treatment were able to have them removed without reobstruction. For the 8 responding patients among those who did not have cholangiocarcinomas, the median response duration was 5 months with a median survival from treatment of 6.5 months. For the 4 responding patients with cholangiocarcinoma, the median response duration was 16 months with a median survival from treatment of 20 months. All responders did not have a return of jaundice due to reobstruction of the major ducts (until death or to the present). All responders who have died did so due to tumor progression outside of the treated field except for one who died of unrelated causes. The mean number of proven or presumed episodes of cholangitis per patient was virtually identical in those without (1.8) and those with stents/tubes (1.4, p = 0.561). This regionally focused combined modality cytotoxic therapy was able to relieve obstruction in the majority of patients without excess morbidity (including a lack of any detectable increase in sepsis). Thus, it appears feasible to consider randomized studies of this cytotoxic approach versus standard mechanical drainage procedures to define the relative risks and benefits of each.

Adult↗
PubMed1989

Hamster zonae pellucidae cannot induce physiological acrosome reactions in chemically capacitated hamster spermatozoa in the absence of albumin.

Cauda epididymal hamster spermatozoa were capacitated with D-penicillamine in a chemically defined (protein-free) medium (= "chemical" capacitation). Hamster zonae pellucidae were incapable of inducing functional acrosome reactions in chemically capacitated hamster sperm in a protein-free medium during sperm-egg coincubation. The culture medium used throughout incubation was a modified Tyrode's solution containing 10 mM sodium lactate, 100 microM sodium pyruvate and 1.0 mg/ml polyvinylalcohol (TLP-PVA). Sperm motility was maintained in all media with PHE (20 microM penicillamine, 100 microM hypotaurine, and 1.0 microM epinephrine). Additional D-penicillamine (125 or 500 microM) or 3 mg/ml bovine serum albumin (high control: TALP-PVA) was used to capacitate sperm during preincubation at 1-2 X 10(6) sperm/ml for 4.0 h at 37 degrees C in 5% CO2 in air. Sperm were then coincubated (2 X 10(4) sperm/ml) with cumulus-free hamster eggs in TALP-PVA or TLP-PVA +/- additional D-penicillamine (total: 500 or 125 microM) for 1.5 or 6.0 h. Percent egg penetration was used as the definitive index of sperm capacitation and functional acrosome reactions. Chemically capacitated sperm did not penetrate eggs (0.0 +/- 0.0%) in the absence of albumin during 1.5 h of sperm-egg coincubation. When sperm were chemically capacitated with 125 microM or 500 microM D-penicillamine, then coincubated with eggs for 6.0 h in the absence of albumin, only 18.8 +/- 28.6% and 23.7 +/- 29.7%, respectively, of eggs were penetrated. Significantly (p less than 0.05) more eggs (67.7 +/- 22.4%) were penetrated when coincubated with chemically capacitated sperm for 1.5 h in medium containing albumin. These results demonstrate that zonae pellucidae of hamster eggs require the presence of albumin to efficiently induce functional acrosome reactions in sperm that are chemically capacitated with D-penicillamine.

Acrosome↗
PubMed1989

Floxuridine-associated sclerosing cholangitis. A dog model.

The authors developed a dog model for the biliary sclerosis that occurs as a severe complication of protracted hepatic arterial floxuridine (FUDR) infusions (using implanted drug delivery systems) in patients with hepatic cancers. Infusaid pumps attached to hepatic arterial catheters were used for protracted infusions in ten mixed breed hounds. To allow repeated cholangiograms, the animals' gallbladders were removed and catheters connected to subcutaneous infusion ports were positioned in the cystic ducts. Five treated dogs received FUDR 0.3 mg/kg/day through the pump for a total of 30 days. Five control dogs received only saline through the pump. Cholangiograms were obtained before and after treatment in all animals. In the control group, serum liver function test results and the cholangiographic appearance of the biliary tree remained within normal limits. By contrast, in the FUDR-treated group, serum glutamic-pyruvic transaminase and alkaline phosphatase progressively rose above normal, starting 2-3 weeks into FUDR infusion, followed by hyperbilirubinemia (7-28 mg/dl peak levels) beginning 4 to 6 weeks after initiation of the drug infusion. Cholangiograms revealed focal strictures involving the central bile ducts (five dogs) and diffuse attenuation of the intrahepatic ducts (four dogs). Thus, the liver function abnormalities and the cholangiographic findings in this dog model mimic the hepatobiliary toxicity in sensitive patients receiving similar treatment.

Animals↗
PubMed1989

Modulation of liver tumor blood flow with hepatic arterial epinephrine: a SPECT study.

Changes in the relative arterial flow to hepatic tumors and adjacent normal liver, in response to varied doses of hepatic arterial epinephrine, were studied with single photon emission computed tomography. In 18 patients with known hepatic tumors, hepatic artery perfusion scans were obtained with the concurrent infusion of technetium-99m-labeled macroaggregated albumin and escalating doses of epinephrine (0-10 micrograms/min). Regions of interest were drawn around tumor and adjacent normal liver in three planes, and the average tumor-to-liver ratio (T:L) was calculated. In all 18 patients, there was a measurable baseline T:L perfusion advantage (range, 1.7-18.7; mean, 4.8). In 12 of 18 patients, this ratio increased with epinephrine (range, 1.1-53.6 times the baseline value; mean, 7.1). In six patients, no improvement in T:L could be demonstrated. In 14 patients the lung shunt index, a measurement of arteriovenous shunting, increased with escalating doses of epinephrine. This pilot study suggests that the infusion of epinephrine may improve the therapeutic index of certain regional therapies such as bolus drug infusions, hepatic arterial embolization, and radioactive microsphere therapy.

Epinephrine↗
PubMed1989

Unsatisfactory hepatic perfusion after placement of an implanted pump and catheter system: angiographic correlation.

Thirty-five patients with scintigrams showing unsatisfactory hepatic artery perfusion after surgical placement of an implanted pump and catheter system were examined with selective angiography (33 cases) or digital subtraction angiography (DSA) during which the contrast material was injected through the side port of the pump (six cases). In 34 of 35 cases, the cause of the unsatisfactory (either extrahepatic or incomplete) hepatic perfusion was defined. DSA was definitive in only two cases, in which extrahepatic flow through collateral vessels was demonstrated. The cause of the perfusion defect was hepatic artery thrombosis in 14 cases, extrahepatic flow through collateral vessels in 14 cases, a misplaced catheter in four cases, and a short proper hepatic artery without adequate length for mixing in two cases. Although hepatic artery perfusion scintigraphy is the primary tool for evaluation of hepatic perfusion after catheter placement, angiography plays an important role in treating the subset of patients with unsatisfactory hepatic perfusion.

Antineoplastic Agents↗
PubMed1989

Hepatic arterial chemotherapy: role of angiography.

Hepatic arterial infusion chemotherapy increases the hepatic concentration of chemotherapeutic agents without increasing systemic toxicity. Both percutaneous (most commonly left transbrachial) and surgical approaches are currently used for infusion catheter placement. Surgical catheter and pump placement has proved to be a reliable means of delivering drugs to the liver and has been commonly used for hepatic arterial chemotherapy for metastatic colorectal carcinoma. Meticulous angiographic evaluation of the hepatic vascular anatomy, its variations, and hemodynamics is necessary for correct catheter placement to achieve total liver perfusion without significant extrahepatic perfusion. Satisfactory hepatic perfusion should be documented before drug infusion. Hepatic arterial radionuclide flow imaging with technetium-99m-labeled macroaggregated serum albumin remains the most reliable means of assessing hepatic perfusion following catheter placement. Transcatheter techniques have been used to facilitate catheter placement, to prevent gastrointestinal drug toxicity, and to correct unsatisfactory perfusion following surgical catheter placement.

Antineoplastic Agents↗