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Biomedical subjects

S H Thompson

Publications and source records attributed to S H Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1988

Features of central giant cell granuloma of the jaws xenografted in nude mice.

In order that the growth pattern and histologic and ultrastructural differentiation of the central giant cell granuloma of the jaws be studied, tissue from three lesions was transplanted into nude mice. Xenografts were harvested at 3 weeks, 5 weeks, 8 weeks, and 13 weeks and examined histologically and ultrastructurally. Implants could be identified as firm subcutaneous nodules, but after 3 weeks began regressing. At 13 weeks, almost total regression had occurred. Histologically, grafts were well vascularized and there was no evidence of necrosis. Typical multinucleated giant cells disappeared at an early stage. The ultrastructural features of the grafts showed giant cells lying in close association with uninuclear cells, features suggestive of a fusion process. Many cells containing microfilaments at their periphery were identified in the original lesional tissue as well as in the xenografts. These cells strongly resembled myofibroblasts. Collagen bundles were seen within the cytoplasm of stromal cells. The observations suggest that the multinucleated giant cells represent a stimulus-dependent, differentiated end-stage cell population.

Animals↗
PubMed1987

Slow membrane currents in bursting pace-maker neurones of Tritonia.

1. Membrane ionic currents in bursting pace-maker neurones of the marine mollusc Tritonia were studied in voltage-clamp experiments with emphasis on slow tail current relaxations after depolarizing pulses. 2. The slow tail current undergoes a complex transition from an initially inward current to an initially outward current as the duration of the depolarizing pulse is lengthened. It was found that the slow tail current is the sum of two separate and independent ionic currents. Methods were devised to study each current in isolation. 3. A slow inward tail current, termed IB, is activated by depolarization and decays exponentially on return to -55 mV with a time constant of 2-4 s. The voltage dependence and kinetics of IB activation were measured. Current amplitude is sensitive to removal of both Na+ and Ca2+ from the bathing medium but the current is not blocked by either tetrodotoxin (TTX) or replacement of Ca2+ by Co+. The amplitude of the current is independent of the external K+ concentration. 4. A slow outward tail current, termed IC, is also activated by depolarization. It is shown to be a K+ current whose activation results from an increase in the cytoplasmic Ca2+ concentration during depolarization. The decay of IC on repolarization requires more than 30 s to reach completion. 5. The slow rates of relaxation of IB and IC tail currents suggest that they are important determinants of the slow membrane potential variations characteristic of burst firing. IB activates more rapidly than IC during depolarization and is thought to be important for maintaining the depolarized phase of the burst cycle and for producing the depolarizing after-potential after each spike. IC activates more slowly but reaches greater amplitudes. It is thought to be important for adaptation in spike frequency during the burst, for burst termination, and for determining the duration of the interval between bursts.

Action Potentials↗
PubMed1986

Cervical lymph node metastases of oral carcinoma related to the depth of invasion of the primary lesion.

Squamous cell carcinoma of the tongue has been found to have a greater frequency of cervical metastases on initial examination than lesions affecting other oral sites. This study analyzes a sample of 21 pathological specimens of oral carcinoma and block neck dissections relating the confirmed histological presence of cervical metastasis to the depth of invasion of the primary lesion. Tongue carcinomas were compared with lesions affecting other oral sites. An arbitrary anatomical levelling system was devised to assess the depth of invasion. Tongue carcinomas show a propensity to infiltrate more deeply than lesions affecting other oral sites. For the entire sample, carcinomas infiltrating the superficial lamina propria occurred much less frequently than lesions showing a deeper infiltration pattern. Overall, lesions infiltrating the deep lamina propria do not exhibit a reduced frequency of occurrence compared to lesions infiltrating the skeletal muscle; however, carcinomas affecting other oral sites showed a reduced frequency of deeply infiltrating lesions in comparison to more superficial lesions. Carcinomas confined to the superficial lamina propria seem to have a better prognosis in relation to developing cervical metastases, and this does not appear to be influenced by age, sex, site, size, or degree of differentiation.

Aged↗
PubMed1985

Plasmacytoid myoepithelioma of a minor salivary gland.

Plasmacytoid myoepitheliomas are rare salivary gland neoplasms that probably represent a variant of the pleomorphic adenoma. They appear to occur more frequently in the minor salivary glands of the mouth. The mean average age at time of diagnosis of intraoral lesions is 18.8 years. Cytologic pleomorphism is a frequent histologic feature, which has led to a questionable diagnosis of malignancy in five out of ten cases. Caution is advocated in the evaluation of a salivary gland neoplasm with such features, and confusion with primary squamous cell or undifferentiated carcinoma of the salivary glands should be avoided. Patients who have cytologically pleomorphic lesions should be assessed for evidence of metastases. Rapid growth, neurologic evidence of sensory or motor dysfunction, and bone invasion should be regarded as ominous clinical parameters. Therapy should be directed toward complete surgical extirpation.

Adult↗
PubMed1985

Ameloblastic sarcoma of the mandible.

Malignant ameloblastic odontogenic tumors have traditionally been classified as either ameloblastic fibrosarcomas, dentinosarcomas or odontosarcomas. This separation is based on the presence of either dentine or dentine and enamel in some lesions. To date, 28 cases of ameloblastic fibrosarcoma, one case of ameloblastic dentinosarcoma, and seven cases of ameloblastic odontosarcoma have been reported in the literature. An additional case of ameloblastic dentinosarcoma is reported in this paper together with a critical review of the clinicopathologic features of previously reported cases of malignant ameloblastic neoplasms. The presence of dental matrix material is not specific and is found in a wide variety of odontogenic tumors in variable amounts. This study supports the concept that the presence of dental matrix material does not alter the basic biologic characteristics of these neoplasms. Accordingly, to simplify a confusing nomenclature, we suggest that malignant tumors of this type be referred to collectively as ameloblastic sarcomas.

Adult↗
PubMed1984

Myoglobin content of granular cell tumor of the tongue. An immunoperoxidase study.

Myoglobin is a protein with a molecular weight of 16,900 daltons that is normally found in adult and fetal striated and cardiac muscle cells. Its synthesis relates to the total ATP requirements of the muscle cell. The histogenesis of the granular cell tumor is controversial, but an origin from striated muscle has been postulated. Seven cases of tongue GCT were evaluated for the presence of myoglobin using the unlabeled antibody (PAP) technique. Normal human striated muscle was used for both positive and negative controls. None of the tumors showed positive staining of the granular cells. Positive controls showed specificity of staining for skeletal muscle. The negative controls did not stain. Granular cell tumors of the tongue do not appear to contain myoglobin. This suggests that either the GCT is not of muscle origin or that, if it is, there may be a metabolic change in the granular cells so that myoglobin is not synthesized. It may be possible that a change in the antigenic determinant has occurred.

Adult↗
PubMed1984

Fibrous histiocytomas of the oral and maxillofacial regions.

Fibrous histiocytomas of the oral and maxillofacial regions are rare. The present study analyzes a sample of 63 cases from the literature together with 7 personally observed cases. Age, sex, site, size, clinical behaviour, treatment and survival were evaluated and related to a histological classification based on that of Rosai (1981). Lesions were assessed for histological criteria which would place them in one of 2 groups: fibrous histiocytoma (FH) or pleomorphic fibrous histiocytoma (PFH). Within these 2 histological groups the cases were subdivided into clinically benign, aggressive or malignant lesions. Thirty-nine cases (56.0%) were classified as FH and 31 cases (44.0%) as PFH. The mean age of male patients with PFH was significantly higher than female patients with FH (t = 3.05; d.f. 37; p less than 0.0025). Lesions in the PFH group involved bone more frequently than those in the FH group (Yate's Chi2 = 16.66; d.f. 1; p less than 0.00025). Lesions involving bone for both histological groups were more likely to be aggressive or malignant than soft-tissue lesions (Yate's Chi2 = 29.9; d.f. 1; p less than 0.00025). Soft-tissue lesions were usually less than 5 cm in greatest diameter. Radiographic features of malignancy for lesions with bone involvement is of prognostic importance regardless of the histological appearance of the lesion. The majority of the lesions under study were from the deep tissues of the oral and maxillofacial regions.

Adolescent↗
PubMed1983

Inherited ophthalmoplegia with intestinal pseudo-obstruction.

A new inherited neuromuscular disease was identified in 4 patients (1 male, 3 females), offspring of consanguineous marriages, belonging to the same kindred. The proband was a 24-year-old female with history of ptosis and ophthalmoplegia since childhood and progressive intestinal pseudo-obstruction for the last 4 years of her life. A sural nerve biopsy showed axonal and demyelinating neuropathy. Muscle biopsies of pectoral and gastrocnemius revealed myopathic alterations with marked variation in muscle fiber size, atrophy of both fiber types and normal mitochondria. An upper gastrointestinal study showed barium in the stomach after 8 h and jejunal diverticula. Tests for absorption of fat, protein, carbohydrate, folic acid and vitamin B12 were normal. Serum levels of vitamin A and lipoproteins were also normal. The patient underwent partial gastrectomy and gastrojejunostomy. Postoperatively, she developed severe pancreatitis, sepsis, peritonitis and expired. Tissue samples from the proband and from her brother, revealed normal mucosa, but degeneration of smooth muscle of the stomach and small intestine. The myenteric plexus and vagus nerves were normal. The biochemical studies of contractile proteins (myosin, actin, tropomyosin) in the fresh and cultured smooth muscle cells of the proband obtained at the time of gastrectomy showed a 50-75% decrease in the synthesis of different contractile proteins. Turnover of contractile proteins and synthesis and turnover of collagen showed normal values. The reduction in synthesis of contractile proteins may account for the weak peristalsis and be a factor in the pathogenesis of the intestinal pseudo-obstruction.

Adult↗
PubMed1983

Calcium buffering and slow recovery kinetics of calcium-dependent outward current in molluscan neurones.

Calcium entry into molluscan neurones during depolarizing voltage-clamp steps activates an outward current which on repolarization decays over periods of more than 30 sec. This slowly decaying tail current was used to study the relation between calcium buffering in cytoplasm and the decline of a calcium-activated membrane process. Calcium-dependent outward current was also studied after injection of calcium into the cytoplasm. The time course of the fall of outward tail current was much less sensitive than tail current amplitude to the amount of calcium entry. Increasing bath temperature from 5 to 15 degrees C decreased the rate of fall of outward tail current activated by calcium entry. In contrast, outward current activated by calcium injection declined more rapidly at higher temperatures. Injection of sufficient EGTA to give maximum depression of outward current during depolarizations reduced the amplitude of outward tail current by at most 50%. After EGTA injection outward tail current declined more rapidly immediately following repolarization, but returned to base line at about the same time as the control. After injection of EGTA, outward current activated by calcium injection was reduced or completely blocked, and returned to base line more rapidly. Application of the mitochondrial uncoupler carbonyl cyanide m-chlorophenyl hydrazone (CCCP) did not alter the decay time course of outward tail current, but markedly prolonged the decline of outward current activated by calcium injection. The slow kinetics of outward tail current were compared to predictions of the concentration of calcium ions at the outermost surface of a spherical model cell following calcium influx. We conclude that after depolarization and calcium entry, the diffusion and binding of free calcium to cytoplasmic buffers plays a key role in determining the rate of fall of outward tail current. Further, different mechanisms influence the decline of calcium-dependent outward current following injection of calcium into the cytosol.

Animals↗
PubMed1979

Current-voltage relationships of repetitively firing neurons.

The current-voltage curves of repetitively firing neurons show non-linearities in the subthreshold region. Microsurgically isolated molluscan neuron somata were studied under voltage clamp using ramp voltage command signals. During the depolarizing 1/2 cycle a region of negative slope conductance was observed. Ion substitution experiments suggest that this results from non-inactivating or slowly inactivating Na+ and Ca2+ currents. The hyperpolarizing 1/2 cycle reveals a hysteresis effect which results at least in part from a Ca2+ activated 5+ current. Similar characteristics have been described in bursting neurons. Their occurrence in the non-bursting neurons studied here shows that they are not unique to this class of neurons and suggests that their primary contribution is to create electrical instability necessary for repetitive firing.

Animals↗
PubMed1979

Inactivation of delayed outward current in molluscan neurone somata.

1. Inactivation of delayed outward current was studied by voltage clamp of isolated neurone somata of the molluscs Archidoris and Anisodoris. During prolonged voltage clamp steps in normal artificial sea water delayed outward current rises to a peak and then declines to a non-zero steady-state. During repetitive clamp pulses at repetition rates slower than 2/sec, the amplitude of peak outward current in the second pulse is commonly less than the amplitude at the end of the preceding pulse, giving the impression of continued inactivation during the repolarized interval. We have termed this property cumulative inactivation. 2. Two components of delayed outward current were separated using tetraethyl ammonium ions (TEA) and cobalt ions (Co). External TEA blocks 90% of a voltage and time dependent outward current termed K current (IK). External Co blocks 85% of a Ca activated delayed outward current termed Ca current (ICa does not inactivate during prolonged or repetitive voltage clamp pulses. IK, however, inactivates during prolonged voltage clamp steps and shows cumulative inactivation during repetitive voltage clamp pulses. 3. Inactivation of IK is voltage and time dependent and does not require influx of Ca ions. 4. As measured by a prepulse method, the onset of inactivation is characterized by a two time constant process. Fast inactivation occurs with a time course comparable to the rate of rise of outward current and can account for 90% of total inactivation. 5. Recovery from inactivation is slow with a time constant approximately an order of magnitude slower than the onset of inactivation. 6. The current-voltage (I-V) curve for peak IK can be N-shaped, with a region of negative slope resistance in the range of +30 to +80 mV. The I-V curve for steady-state IK, however, shows little or no tendency to form a local maximum. 7. The pattern of delayed outward current varies considerably between cells. A major contributing factor to this variability appears to be the relative contributions of ICa and IK to delayed outward current.

Animals↗
PubMed1979

Mechanism of frequency-dependent broadening of molluscan neurone soma spikes.

1. Action potentials recorded from isolated dorid neurone somata increase in duration, i.e. broaden, during low frequency repetitive firing. Spike broadening is substantially reduced by external Co ions and implicates an inward Ca current. 2. During repetitive voltage clamp steps at frequencies slower than 1 Hz, in 100 mM-tetraethyl ammonium ions (TEA) inward Ca currents do not increase in amplitude. 3. Repetitive action potentials result in inactivation of delayed outward current. Likewise, repetitive voltage clamp steps which cause inactivation of delayed outward current also result in longer duration action potentials. 4. The frequency dependence of spike broadening and inactivation of the voltage dependent component (IK) of delayed outward current are similar. 5. Inactivation of IK is observed in all cells, however, only cells with relative large inward Ca currents show significant spike broadening. Spike broadening apparently results from the frequency dependent inactivation of IK which increases the expression of inward Ca current as a prominent shoulder on the repolarizing phase of the action potential. In addition, the presence of a prolonged Ca current increases the duration of the first action potential thereby allowing sufficient time for inactivation of IK.

Action Potentials↗