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Biomedical subjects

M H Weiss

Publications and source records attributed to M H Weiss.

At least 73 records · Page 4Linked to original sources
PubMed1993

The significance of subarachnoid hemorrhage after penetrating craniocerebral injury: correlations with angiography and outcome in a civilian population.

Certain clinical factors are considered to have an effect on patient outcome after penetrating missile injury. These include bilateral hemispheric injury, ventricular hemorrhage, intracerebral hemorrhage, mass effect, and missile or bony fragmentation. The relationship of subarachnoid hemorrhage (SAH) after penetrating craniocerebral injury and outcome is unknown. In addition, controversy exists regarding the role of angiography and the incidence of traumatic intracranial aneurysm in this population. Finally, can we assume that the incidence of traumatic intracranial aneurysm is equal in military and civilian populations, given the absence of penetrating shrapnel injury in civilian populations? Now that computed tomography has supplanted angiography as the primary diagnostic modality, increasing vigilance on the part of the physician and examination of angiography in high-risk patients should allow for enhanced outcome. We evaluated 100 patients with a diagnosis of cerebral gunshot wound over a 12-month period. All patients were evaluated neurologically at the time of admission and had imaging studies. Thirty-one patients with radiological evidence of SAH on computed tomography underwent angiography. Angiograms were limited to the side of the injury in patients with single-lobe or unilateral multilobe injuries and were bilateral in patients with bilateral hemispheric involvement. One intracranial aneurysm (3.2%) was documented and treated surgically. In those patients who died within 48 hours of admission, 68% had SAH as compared with only 17% of those surviving. Outcome was based upon neurological evaluation at the time of discharge and at the time of clinical follow-up at 3 and 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

Penetrating craniocerebral injury resultant from gunshot wounds: gang-related injury in children and adolescents.

We prospectively and retrospectively reviewed a series of 780 patients who presented to the University of Southern California/Los Angeles County Medical Center with a diagnosis of gunshot wound to the brain during an 8-year period. Of these, 105 were children ranging in age from 6 months to 17 years. Injuries were gang related in 76 (72%) children and adolescents. Stepwise linear regression analysis was used to formulate a predictive model of outcome in this population. Patient age (F = 10.92), sex (F = 9.32), occipital entry site (F = 8.17), bihemispheric injury (F = 8.50), and admission Glasgow Coma Scale (F = 69.91) were all found to correlate with outcome (P < 0.05). Significant differences between pediatric and adult populations were noted in transit time, entrance site, and age-related outcome. Occipital or assassination-type wounds were most common in children. In addition, a younger age was associated with poor outcome (P < 0.0001). We describe both the economic and racial trends in our population of patients in addition to weapon type and toxicological evaluation. The Department of Neurological Surgery is becoming directly involved in providing information to children at the junior high school level regarding gang activity and brain and spinal cord injury. In conjunction with the Community Youth Gang Services Organization and Think First Organization, we are attempting to integrate prevention through education and community mobilization. This is a plan aimed at informing and recovering the youth affected by gangs.

Adolescent↗
PubMed1993

Development of neurosurgery in southern California and the Los Angeles county/University of Southern California Medical Center.

The Los Angeles County General Hospital has played an integral role in the development of medicine and neurosurgery in Southern California. From its fledgling beginnings, the University of Southern California School of Medicine has been closely affiliated with the hospital, providing the predominant source of clinicians to care for and to utilize as a teaching resource the immense and varied patient population it serves.

Academic Medical Centers↗
PubMed1993

Subdural empyema of the cervical spine: clinicopathological correlates and magnetic resonance imaging. Report of three cases.

A paucity of formally described information is available in the scientific literature regarding spinal subdural empyema. Patients presenting with neurological deterioration associated with subdural empyema are rarely identified, and treatment is often based upon anecdotal cases. The authors contribute three cases of primary cervical spinal subdural empyema and review the seven found in the literature. All patients had clinical evidence of neurological compromise, cervical tenderness, cervical pain, and leukocytosis upon admission. Cervical involvement ranged from C-2 to C-7. All patients underwent laminectomy with durotomy and drainage. The authors recommend prompt surgical decompressive laminectomy, copious irrigation, and drainage, followed with appropriate adjunctive antibiotic therapy for treatment of these patients.

Adult↗
PubMed1992

An in situ perfused guinea-pig eye model for blood-ocular transport studies: application to amino acids.

A technique for in situ vascular eye perfusion (VEP) in the guinea-pig has been developed for measurements of the blood-ocular transport kinetics of substrates under controlled conditions of arterial inflow. The blood-aqueous and blood-vitreous barriers remained intact to the vascular space marker [3H]dextran (MW 70 kDa) with the perfusion pressure maintained between 80 and 100 mmHg. Several 3H-, 14C- or 35S-labeled amino acids, and 3H- or 14C-labeled sucrose (extracellular space marker) were used to validate the VEP model for transport kinetic studies. Multiple time-point graphic analysis was used to estimate the compartmental unidirectional blood-ocular transport constants, K(in), within the 20 min period of the VEP experiment. Blood-to-aqueous humor K(in) values for [3H]serine, [14C]N-methyl-alpha-aminoisobutyric acid (MeAIB) and [3H] or ]14C]sucrose were 3.57 +/- 0.38, 1.21 +/- 0.13 and 1.13 +/- 0.17 microliters min-1 g-1, respectively. The respective blood-to-lens K(in) values for labeled serine, MeAIB and sucrose were 1.71 +/- 0.19, 0.09 +/- 0.03 and 0.03 +/- 0.002 microliters min-1 g-1. The uptake of newly secreted amino acids from the aqueous humor in the lens followed the order: [35S]methionine greater than [3H]serine greater than or equal to [35S]cysteine greater than or equal to [3H]alanine greater than [14C]cycloleucine greater than or equal to [14C]MeAIB greater than or equal to [3H] or [14C]sucrose. The data indicate lack of a rapid blood-to-lens uptake of two model amino acids defining the A and L amino acid carriers.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1992

Magnetic resonance imaging and pathological correlates of meningiomas.

We examined the relationships between specific magnetic resonance imaging features and certain gross and microscopic characteristics of meningiomas, including vascularity, gross texture (consistency), and venous sinus involvement. Magnetic resonance imaging scans, surgery reports, and the histopathological findings of tumors were examined retrospectively in 54 patients. Sinus involvement was accurately predicted on T1-weighted images in 9 of 10 cases (P = 0.001) and tumors with cystic changes in 3 of 3 cases. T1-weighted images were not useful for predicting vascularity unless actual flow voids could be visualized (five of six cases). There was no correlation between T1 signal intensity, tumor consistency, or histological findings. In tumors without detectable vascularity on T1-weighted images, hyperintensity relative to gray matter on T2-weighted images was correlated with increased vascularity (P = 0.004). Tumors with soft consistency (P = 0.007), cellular atypia, invasion, angioblastic, or melanocytic components were also hyperintense, compared with gray matter on T2-weighted images (P = 0.0266). Aggressive meningiomas were found to be more vascular (P = 0.045). No correlation was found between the degree of surrounding edema or contrast enhancement with histopathological findings, vascularity, or consistency.

Brain↗
PubMed1992

Surgery for recurrent and residual cholesteatoma.

One hundred twelve patients (116 ears) were treated for recurrent and residual cholesteatoma. A retrospective review revealed that 66% had undergone canal wall down mastoidectomy at the previous surgery. The surgical procedure at revision was selected on the basis of an intraoperative assessment of the extent of disease, and clinical prediction of eustachian tube function. The average period of follow-up was 3.4 years. Revision surgery was successful in providing the patient with a safe, dry ear in 105 (91%) of 116 cases. Surgical principles and hearing results are presented.

Adult↗
PubMed1991

Vasopressin uptake by hypothalamopituitary axis and pineal gland in guinea pigs.

The uptake of circulating arginine vasopressin (AVP) by the pituitary gland (anterior lobe), pineal gland, and hypothalamus (ventromedial part) was investigated in an isolated in situ perused brain of anesthetized guinea pig. Kinetic experiments revealed saturable AVP uptake in all studied regions with Km values of 0.79, 0.19, and 0.76 microM and maximum velocity values of 22, 2.1, and 1.6 pmol.min-1.g-1 for the pituitary gland, pineal gland, and hypothalamus, respectively. The nonsaturable components (diffusion constants) were not significantly different from zero. Peptide fragments, L-phenylalanine, and Bestatin (an aminopeptidase inhibitor) did not interfere with AVP uptake. However, uptake of AVP was strongly inhibited in the presence of the V1 antagonist [1-(beta-mercapto-beta-beta-cyclopentamethylenepropionic acid), 2-(O-methyl)tyrosine]AVP at 2.7 microM, and regional Ki values, assuming that the observed inhibitions were purely competitive, ranged between 0.32 and 2.23 microM. The V2 agonist 1-desamino-8-D-AVP at 2.7 microM produced only a weak inhibition of AVP uptake, and regional Ki values ranged between 9.56 and 21.3 microM. It is concluded that specific uptake mechanisms in the hypothalamopituitary axis and pineal gland are sensitive enough to detect blood-borne AVP under the physiological hormonal state. It is suggested that AVP binding in situ is primarily related to V1 receptors, which may be involved in mediating the central effects of this circulating peptide.

Animals↗
PubMed1991

Kinetics of circulating vasopressin uptake by choroid plexus.

Uptake of circulating arginine vasopressin (AVP) by choroid plexus was studied by means of the in situ brain perfusion technique in anesthetized guinea pig and by means of single-circulation paired-tracer dilution technique in isolated perfused sheep choroid plexus. Kinetic analysis revealed saturable AVP uptake with Michaelis constant (Km) values of 32 +/- 4 and 31 +/- 5 nM and maximal saturable influx rate (Vmax) of 0.45 +/- 0.06 and 12.1 +/- 0.67 pmol.min-1.g-1 in guinea pig and sheep choroid plexus, respectively. The peptide fragments AVP-(1-8) and [pGlu4,Cyt6]AVP-(4-9), the amino acids L-phenylalanine, L-tyrosine, and 2-aminobicyclo(2,2,1)heptane-2-carboxylic acid, and the aminopeptidase inhibitors Bestatin and bacitracin did not influence hormone kinetics. However, the V1 antagonist [(1-beta-mercapto-beta,beta-cyclo-pentamethylenepropionic acid)-O-methyl-Tyr2]AVP significantly inhibited AVP uptake with inhibitor constant (Ki) values of 0.19 +/- 0.03 (guinea pig) and 0.07 +/- 0.01 microM (sheep). The V2 agonist 1-desamino-8-D-AVP and pressinoic acid produced weak inhibitions only in guinea pig choroid plexus, and Ki/Km ratios indicated 220 and 310 times lower affinities than for AVP, respectively. It is suggested that the membrane mechanism responsible for AVP uptake in choroid plexus has a binding site with properties similar to those of V1 receptor.

Animals↗
PubMed1991

Choanal atresia and lymphedema.

The coexistence of bilateral bony choanal atresia and lower-extremity lymphedema was observed in a family with several consanguineous marriages. The combination of these two rare anomalies, in a hereditary form, has not been described before.

Abnormalities, Multiple↗
PubMed1991

Management of labyrinthine fistulas caused by cholesteatoma.

The surgical management of labyrinthine fistulas caused by cholesteatoma remains controversial. Forty cases (41 ears) of labyrinthine fistulas were reviewed. This represented 10% of our total series of cholesteatomas in adults and children (426 ears). Clinical presentation, extent of disease, results of fistula testing and audiometric studies, and radiographic findings were analyzed. A canal wall-down procedure was performed in all but one patient. Generally an attempt was made to completely remove the cholesteatoma, to graft the fistulous area, and to reconstruct the middle ear mechanism in one stage. The matrix was preserved in patients with large fistulas where the involved ear was the only hearing one, when the matrix was adherent to the underlying optic duct, and in selected elderly persons. Long-term followup did not reveal a significant difference in hearing, degree of vertigo, or incidence of recidivism when those patients in whom the matrix was removed were compared with those in whom the matrix was preserved. The importance of recognizing the presence of a labyrinthine fistula preoperatively is stressed, along with the need to be prepared for an unexpected fistula. Operative management is described.

Adolescent↗
PubMed1991

Treatment of unresectable meningiomas with the antiprogesterone agent mifepristone.

The possibility that meningioma growth may be related to female sex hormone levels is suggested by several lines of evidence. Meningiomas are twice as common in women as in men, have been observed to wax and wane with pregnancy, and are positively associated with breast cancer. A physiological explanation for these phenomena is provided by the finding of steroid hormone receptors in meningiomas. However, unlike breast cancer, meningiomas are much more commonly positive for progesterone receptors than for estrogen receptors. The authors initiated a study on long-term oral therapy of unresectable meningiomas with the antiprogesterone mifepristone (RU486). Fourteen patients received mifepristone in daily doses of 200 mg for periods ranging from 2 to 31+ months (greater than or equal to 6 months in 12 patients). Five patients have shown signs of objective response (reduced tumor measurement on computerized tomography scan or magnetic resonance image, or improved visual field examination). Three have also experienced subjective improvement (improved extraocular muscle function or relief from headache). The side effects of long-term mifepristone therapy have been mild. Fatigue was noted in 11 of the 14 patients. Other side effects included hot flashes in five patients, gynecomastia in three, partial alopecia in two, and cessation of menses in two. Long-term therapy with mifepristone is a new therapeutic option that may have efficacy in cases of unresectable benign meningioma.

Adult↗