The effect of gravity on the horizontal and vertical vestibulo-ocular reflex in the rat

Horizontal and vertical eye movements were recorded in alert pigmented rats using chronically implanted scleral search coils or temporary glue-on coils to test the dependence of the vestibulo-ocular reflex (VOR) upon rotation axis and body orientation. The contributions of semicircular-canal versus otolith-organ signals to the VOR were investigated by providing canal-only (vertical axis) and canal plus otolith (horizontal axis) stimulation conditions. Rotations that stimulated canals only (upright yaw and nose-up roll) produced an accurate VOR during middle- and high-frequency rotations (0.2-2 Hz). However, at frequencies below 0.2 Hz, the canal-only rotations elicited a phase-advanced VOR. The addition of a changing gravity stimulus, and thus dynamic otolith stimulation, to the canal signal (nose-up yaw, on-side yaw, and upright roll) produced a VOR response with accurate phase down to the lowest frequency tested (0.02 Hz). In order to further test the dependence of the VOR on gravitational signals, we tested vertical VOR with the head in an inverted posture (inverted roll). The VOR in this condition was advanced in phase across all frequencies tested. At low frequencies, the VOR during inverted roll was anticompensatory, characterized by slow-phase eye movement in the same direction as head movement. The substantial differences between canalonly VOR and canal plus otolith VOR suggest an important role of otolith organs in rat VOR. Anticompensatory VOR during inverted roll suggests that part of the otolith contribution arises from static tilt signals that are inverted when the head is inverted.     

Quantitative reflection spectroscopy at the human ocular fundus

A new model of the reflection of the human ocular fundus on the basis of the adding-doubling method, an approximate solution of the radiative transport equation, is described. This model enables the calculation of the concentrations of xanthophyll in the retina, of melanin in the retinal pigment epithelium and the choroid, and of haemoglobin in the choroid from fundus reflection spectra. The concentration values found in 12 healthy subjects are in excellent agreement with published data. In individual cases of pathologic fundus alterations, possible benefits to the ophthalmologic diagnostics are demonstrated.     

Prolonged field bursts in the dentate gyrus: dependence on low calcium, high potassium, and nonsynaptic mechanisms.

1. The dentate gyrus has been proposed to be a gate for entry of neuronal activity into the hippocampus. This function would give it a critical role in the propagation of seizure activity in that region. The hallmark of epileptiform activity in the dentate itself, often referred to as "maximal dentate activation" (MDA), has not been reproduced previously in vitro. 2. With the use of rat hippocampal slices, bath [Ca2+] was decreased, and [K+] was increased concurrently to simulate conditions found during intense neuronal activity in vivo. Both evoked and spontaneous field bursts were observed in the dentate granule cell layer under these conditions. These bursts were similar to MDA, consisting of a prolonged negative shift in extracellular potential with large-amplitude population spikes. 3. In 0.5 mM bath [Ca2+], single stimuli applied to the perforant path could evoke prolonged field bursts in the dentate only when bath [K+] was > or = 9 mM. However, repetitive stimulation (10 Hz) of the perforant path could elicit similar dentate responses when bath [K+] was as low as 5 mM. 4. In 0.5 mM bath [Ca2+], interictal-type bursts appeared spontaneously in CA1 and CA3 when bath [K+] was > or = 5 mM but were lost when [K+] was > 9 mM. Spontaneous seizurelike activity in the dentate required a higher minimum bath [K+] (9 mM) and persisted at [K+] of 11 mM. 5. Stimulation-evoked field bursts in the dentate altered epileptiform activity in CA3. At bath [K+] insufficient to cause spontaneous CA3 bursts, CA3 was activated transiently when prolonged field bursts occurred in the dentate. At higher bath [K+] in which spontaneous CA3 bursts did occur, they were depressed during the dentate bursts. 6. Deletion of Ca2+ from the bath; the addition of 30 microM each of bicuculline methiodide, D,L-2-amino-5-phosphonopentanoate (AP-5), and 6,7-dinitroquinoxaline-2,3-dione (DNQX); or the combination of both manipulations did not block antidromically evoked or spontaneous prolonged field bursts in the dentate. Thus the mechanisms maintaining and propagating these events did not require fast amino acid-mediated synaptic transmission. 7. The concurrent alteration of [K+] and [Ca2+] required to produce prolonged field bursts in the dentate underscores the positive feedback relationship between neuronal excitation and extracellular ionic concentrations, whereas the ability of synaptic stimulation to trigger nonsynaptic seizurelike events such as these prolonged field bursts may be relevant to the transition from interictal to ictal activity in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)     

Sphenoid sinus brown tumor, hypercalcemia, and blindness: an unusual presentation of primary hyperparathyroidism

This is a first report of primary hyperparathyroidism (HPT) masquerading as a destructive fibrous sphenoid sinus "Brown tumor" associated with progressive blindness and hypercalcemia. Diagnosis of a Brown tumor was delayed despite serial computerized tomography of the head and repeated transnasal and transethmoid sphenoid biopsies demonstrating diffuse fibrosis. Only detection and medical evaluation of hypercalcemia, demonstrating elevation of both serum calcium and C-terminal parathyroid hormone with an elevated chloride/phosphate ratio, prompted neck exploration, thus confirming a solitary left superior parathyroid adenoma. Postoperative normocalcemia occurred synchronously with the return of light perception and the arrest of sphenoid sinus and parasellar erosion. Although maxillary Brown tumors of secondary HPT have been reported, this is the first report of osteitis fibrosa of the sphenoid sinus. Differential diagnosis of an erosive sphenoid lesion with cranial nerve dysfunction, exclusive of inflammatory or vascular disease, should include sarcoidosis, primary and metastatic sphenoid carcinoma, fibrous dysplasia, giant cell reparative granuloma, midline lethal granuloma, chordoma, and chondrosarcoma. Furthermore, the bony destructive lesions with concomitant hypercalcemia of sarcoidosis and HPT are distinguishable by radiographic and laboratory analyses and by the Dent corticosteroid suppression test. Hypercalcemia of primary HPT is associated with elevated serum C-terminal parathormone, osteitis fibrosa, a negative Dent test, and a chloride/phosphate ratio greater than 33 in 94% of primary HPT patients. Hypercalcemia of sarcoidosis is associated with a normal or decreased C-terminal parathormone assay and a positive Dent test, as well as elevated serum immunoglobulins and erythrocyte sedimentation rate, and a positive angiotensin-converting enzyme assay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Race as a risk factor in the severity of infragenicular occlusive disease: study of an urban hospital patient population

We retrospectively studied the arteriograms of 135 men admitted for evaluation of lower extremity ischemia to examine whether race influences the severity of infragenicular occlusive disease. The scoring system prepared by the Ad Hoc Committee on Reporting Standards for the Society for Vascular Surgery and the International Society for Cardiovascular Surgery was used to grade the severity of stenosis in each of the upper, middle, and lower thirds of the anterior and posterior tibial and peroneal arteries (collectively called "infragenicular" arteries). The patients were divided into two groups: 83 blacks (140 arteriogram limbs) and 52 whites (87 arteriogram limbs). Disease severity scores between the groups were compared, and the existence of five known risk factors for atherosclerosis were considered for poststratification adjustment. Results showed that higher disease scores, indicating more severe disease, were found in the black population in every segment of the infragenicular arteries. The mean (+/- SE) score for all the infragenicular segments in blacks was significantly higher than that in the whites (2.08 +/- 0.05 vs 1.57 +/- 0.06, p less than 0.001). The black and white groups were comparable in terms of age (65.2 vs 64.6 years), prevalence of diabetes (20% vs 25%), smoking history (93% vs 90%), and hypercholesterolemia (51% vs 63%). Hypertension was more prevalent among the black patients (51% vs 27%, p less than 0.001). When only the non-hypertensive patients in both groups were considered, however; the mean severity score was still significantly higher in blacks (2.10 +/- 0.06 vs 1.42 +/- 0.06, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Photodynamic therapy for treatment of head and neck cancer

Since 1975, photodynamic therapy has reportedly been effective in a variety of head and neck malignancies that failed traditional (conventional) therapy, including surgery, cryotherapy, chemotherapy, hyperthermia, and radiation therapy. Photodynamic therapy consists of the intravenous administration of (di)hematoporphyrin ether, a chemosensitizing drug selectively retained by neoplastic and reticuloendothelial tissues which, when exposed to a 630-nm argon laser, catalyzes a photochemical reaction to release free oxygen radicals, "the cytotoxic" agents responsible for cell death and tumor necrosis. Preliminary investigations have assessed the efficacy of photodynamic therapy in treatment of: (1) superficial "condemned mucosa" or "field cancerization" of the oral cavity and (2) stage III and IV head and neck carcinomas that had unsuccessful conventional therapy. Complete and/or partial remissions were obtained in 11 of 12 patients (16 treatments) with a variety of carcinomas of the nasopharynx, palate and uvula, retromolar trigone, temporal bone, cervical esophagus, and AIDS-related Kaposi's sarcoma of the oral cavity.     

Allelic loss on chromosome-13 can preceed histological-changes in head and neck-cancer

Seventy paired tumor and blood samples from patients with upper aerodigestive tract squamous cell carcinoma (UADT SCC) were tested for allelic loss on chromosome 13. Increased loss of heterozygosity (LOH) was observed at 11 of 13 different highly polymorphic microsatellite 'CA' dinucleotide repeat-containing loci. Increasing percent LOH correlated with lymph node metastasis (N Stage) (p=0.016). LOH was also detected in 10 of 16 (63%) informative samples of histologically normal mucosa adjacent to the tumors. These findings demonstrate that allelic loss on chromosome 13 is a frequent event in UADT SCC. Furthermore, these genetic alterations can be detected prior to histological changes in normal mucosa adjacent to these tumors.     

New instruments, bone liners, and tray for finger joint arthroplasty

Titanium circumferential grommets have been developed for finger joint arthroplasty that fit on the base of the silicone implant stems to protect the flexible hinge from tearing and fracture. To facilitate grommet insertion, new intramedullary bone rasps have been devised with a reverse cutting tooth pattern, an extended shaft for an improved view of the surgical field, and a redesigned cutting head to allow for grommet insertion. Surgical accessibility and ease of recognition have been facilitated by the development of color-coded sizers. All of the instruments necessary for finger joint surgery are available in a molded tray that has also been redesigned with a transparent lid and clearly labeled compartments for accurate determination of instruments and implant sizers.     

Internal derangements of the shoulder: decision tree and cost-effectiveness analysis of conventional arthrography, conventional MRI, and MR arthrography

Purpose. In a patient with internal derangement of the shoulder, the diagnostic method of choice is controversial. Conventional arthrography can diagnose most rotator cuff tears accurately; however, in many institutions MR arthrography is usually necessary to diagnose labral tears. We utilized decision tree methodology to compare the cost- effectiveness of conventional arthrography and conventional MRI with a hypothetical algorithm in which a patient underwent arthrography, performed with admixed gadolinium, which if negative, was followed by MRI. Design. The use of double-contrast arthrography alone, conventional MRI alone, and gadolinium-enhanced MRI used as an adjunct to conventional arthrography were modeled for the diagnosis of full-thickness rotator cuff tears (RCT), partial RCTs, labral tears, and the absence of cuff/labral tears using decision analysis methodology. English language medical publications were searched to determine the base probabilities for the accuracy of the diagnostic tests. The outcome utilities ranged from –1 to +1 to reflect the value of correct diagnostic evaluation. Charges for diagnostic tests and appropriate surgical treatments were based on 1997 Medicare reimbursement rates for professional fees and hospital charges in an outpatient setting. Sensitivity analyses were performed to evaluate the effects of uncertainty regarding the prevalence of each disease state and the accuracy of several diagnostic tests. Results. In the base-case analysis, the average effectiveness of double-contrast arthrography alone, MRI alone and arthrography selectively followed by MRI were 0.6610, 0.6715, and 0.7204, respectively. The average costs for each of these strategies were $1090, $2033, and $2339, respectively. Conclusion. Arthrography performed with admixed diluted gadolinium, which if negative is immediately followed by MRI, was somewhat more expensive than conventional MRI. However, because of much greater effectiveness, cost-effectiveness was significantly higher for our proposed algorithm. Conventional arthrography without gadolinium, although less expensive, had severely limited effectiveness. Received: 4 June 1999 Revision requested: 6 August 1999 Revision received: 30 August 1999 Accepted: 1 September 1999