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Biomedical subjects

E Eisenberg

Publications and source records attributed to E Eisenberg.

At least 19 recordsLinked to original sources
PubMed1992

Lip cancer. Incidence trends in Connecticut, 1935-1985.

Suspicions have recently arisen that cancer of the lip may exert an undue influence on overall oral cancer statistics and, therefore, possibly distort the true image of intraoral cancer. The authors investigated this question through epidemiologic analysis. A total of 2291 cases of lip cancer accessioned by the Connecticut Tumor Registry (CTR) from 1935 to 1985 (23.6% of all oral cancer) were analyzed. Occurrence trends for males and females had different patterns: for men, the age-adjusted incidence rates showed a fivefold decrease during the 51-year study; for women, the rates were relatively low and constant during the same period. Analysis for age-specific rates revealed that the older the age group, the higher the incidence rates for both sexes. Squamous cell carcinoma accounted for at least 87.4% of all lip cancers (96.2% if nonspecified epithelial neoplasms are assumed to be squamous cell carcinoma). The vermilion border of lower lip was the most common site. Moderately differentiated tumors were most common (48.5%), closely followed by well-differentiated tumors (44.2%). Analysis by county showed that the crude incidence rates for males in New London and Windham counties exceeded the average Connecticut statewide rates. The authors concluded that the epidemiology of Connecticut lip cancer differs significantly from that of intraoral squamous cell carcinoma in the same population studied within the same period of time. Epidemiologic studies involving "oral cancer" should direct attention to anatomic subsite to consider differences in disease trends according to specific location.

Adenocarcinoma↗
PubMed1992

Lichenoid lesions of oral mucosa. Diagnostic criteria and their importance in the alleged relationship to oral cancer.

Lichen planus and other lichenoid disorders of oral mucosa occur commonly, and yet they are poorly understood. Further, the question of the premalignant potential of oral lichen planus remains deeply mired in controversy. The object of this article is to delineate these problems, clarify the issues, and present evidence to support the position that true lichen planus of oral mucosa is not only less common than generally appreciated but also has no inherent predisposition to become malignant. Rationale and data from the literature are offered in support of this position.

Humans↗
PubMed1992

Incidental oral hairy leukoplakia in immunocompetent persons. A report of two cases.

In this brief article we report on two HIV-negative patients with documented oral hairy leukoplakia who had no known risk factors for HIV infection nor any evidence of other forms of immune suppression. Therefore we conclude that in some instances hairy leukoplakia can represent an isolated and innocuous Epstein-Barr virus infection.

Adult↗
PubMed1979

Mechanism of actomyosin adenosine triphosphatase. Evidence that adenosine 5'-triphosphate hydrolysis can occur without dissociation of the actomyosin complex.

We have investigated the steps in the actomyosin ATPase cycle that determine the maximum ATPase rate (Vmax) and the binding between myosin subfragment one (S-1) and actin which occurs when the ATPase activity is close to Vmax. We find that the forward rate constant of the initial ATP hydrolysis (initial Pi burst) is about 5 times faster than the maximum turnover rate of the actin S-1 ATPase. Thus, another step in the cycle must be considerably slower than the forward rate of the initial Pi burst. If this slower step occurs only when S-1 is complexed with actin, as originally predicted by the Lymn-Taylor model, the ATPase activity and the fraction of S-1 bound to actin in the steady state should increase almost in parallel as the actin concentration is increased. As measured by turbidity determined in the stopped-flow apparatus, the fraction of S-1 bound to actin, like the ATPase activity, shows a hyperbolic dependence on actin concentration, approaching 100% asymptotically. However, the actin concentration required so that 50% of the S-1 is bound to actin is about 4 times greater than the actin concentration required for half-maximal ATPase activity. Thus, as previously found at 0 degrees C, at 15 degrees C much of the S-1 is dissociated from actin when the ATPase is close to Vmax, showing that a slow first-order transition which follows the initial Pi burst (the transition from the refractory to the nonrefractory state) must be the slowest step in the ATPase cycle. Stopped-flow studies also reveal that the steady-state turbidity level is reached almost instantaneously after the S-1, actin, and ATP are mixed, regardless of the order of mixing. Thus, the binding between S-1 and actin which is observed in the steady state is due to a rapid equilibrium between S-1--ATP and acto--S-1--ATP which is shifted toward acto-S-1--ATP at high actin concentration. Furthermore, both S-1--ATP and S-1--ADP.Pi (the state occurring immediately after the initial Pi burst) appear to have the same binding constant to actin. Thus, at high actin concentration both S-1--ATP and S-1--ADP.Pi are in rapid equilibrium with their respective actin complexes. Although at very high actin concentration almost complete binding of S-1--ATP and S-1--ADP.Pi to actin occurs, there is no inhibition of the ATPase activity at high actin concentration. This strongly suggests that both the initial Pi burst and the slow rate-limiting transition which follows (the transition from the refractory to the nonrefractory state) occur at about the same rates whether the S-1 is bound to or dissociated from actin. We, therefore, conclude that S-1 does not have to dissociate from actin each time an ATP molecule is hydrolyzed.

Actins↗
PubMed1979

Cooperative binding of tropomyosin to muscle and Acanthamoeba actin.

Analyses of the binding of tropomyosin to muscle and Acanthamoeba actin by the use of Scatchard plots indicate that the binding exhibits strong positive cooperativity in the presence of Mg2+. The cooperative nature of the binding is not affected by the presence of 80 mm KCl, but appears to decrease somewhat in the presence of heavy meromyosin or subfragment-1. Heavy meromyosin, subfragment-1, and KCl each increase the binding affinity of actin for tropomyosin; depending on the experimental condition and the type of actin involved, the apparent binding constant, Kapp, is in the range of 1 to 4 x 10(6) M-1. Muscle actin cross-linked with glutaraldehyde failed to bind tropomyosin even when heavy meromyosin, subfragment-1, or KCl were added as inducers, although the cross-linked actin still markedly activated the heavy meromyosin ATPase.

Actins↗
PubMed1979

The mechanism of the skeletal muscle myosin ATPase. I. Identity of the myosin active sites.

In the present study, the question of whether the two myosin active sites are identical with respect to ATP binding and hydrolysis was reinvestigated. The stoichiometry of ATP binding to myosin, heavy meromyosin, and subfragment-1 was determined by measuring the fluorescence enhancement caused by the binding of MgATP. The amount of irreversible ATP binding and the magnitude of the initial ATP hydrolysis (initial Pi burst) was determined by measuring [gamma-32P]ATP hydrolysis with and without a cold ATP chase in a three-syringe quenched flow apparatus. The results show that, under a wide variety of experimental conditions: 1) the stoichiometry of ATP binding ranges from 0.8 to 1 mol of ATP/myosin active site for myosin, heavy meromyosin, and subfragment-1, 2) 80 to 100% of this ATP binding is irreversible, 3) 70 to 90% of the irreversibly bound ATP is hydrolyzed in the initial Pi burst, 4) the first order rate constant for the rate-limiting step in ATP hydrolysis by heavy meromyosin is equal to the steady state heavy meromyosin ATPase rate only if the latter is calculated on the basis of two active sites per heavy meromyosin molecule. It is concluded that the two active sites of myosin are identical with respect to ATP binding and hydrolysis.

Adenosine Triphosphatases↗
PubMed1979

The mechanism of the skeletal muscle myosin ATPase. II. Relationship between the fluorescence enhancement induced by ATP and the initial Pi burst.

A major question about the mechanism of the myosin ATPase is how much of the fluorescence change which accompanies the binding of ATP to myosin is due to the conformational change induced by ATP and how much is due to the subsequent hydrolysis of ATP in the initial Pi burst. Several laboratories have suggested that the maximal rate of the fluorescence change represents the rate of the irreversible conformational change induced by ATP. In the present study, the rate of irreversible ATP binding, the rate of the initial Pi burst, and the rate of the fluorescence enhancement were compared under varied conditions. The results show that: 1) the fluorescence enhancement is mainly due to the hydrolysis of ATP in the initial Pi burst rather than to the conformational change induced by the binding of ATP; 2) the rate of the initial Pi burst is considerably slower than the rate of irreversible ATP binding at high ATP concentration; 3) the rate of the initial Pi burst is almost the same as the rate of the fluorescence enhancement. Therefore, the maximum rate of the fluorescence enhancement represents the rate of the initial Pi burst rather than the rate of the conformational change induced by ATP binding.

Adenosine Triphosphatases↗
PubMed1978

Sjögren's syndrome (sicca complex).

A case of sicca complex Sjögren's syndrome in a 41-year-old woman is presented. Symptoms related to xerophthalmia and xerostomia were severe but, ironically, served to confuse the clinical impressions of medical personnel managing this patient, resulting in a diagnostic dilemma. Biopsy of a labial minor salivary gland followed by histopathologic examination of the tissue provided invaluable information which, together with the clinical picture, aided in the establishment of the delayed diagnosis.

Adult↗
PubMed1978

Intraoral isolated herpes zoster.

A case of herpes zoster limited to the right palate and the edentulous alveolar ridge in the absence of concurrent skin lesions or predisposing systemic disease is presented. Because of the relative rarity of isolated mucous membrane lesions of this viral disease, the tendency for intraoral vesicles to break down and ulcerate early, and, in this patient, the additional clinical findings of marked swelling and induration, malignancy rather than herpes zoster was suspected; cytologic smear furthered the suggestion of the former. A biopsy provided the definitive diagnosis.

Aged↗
PubMed1978

Formation of a ternary complex: actin, 5'-adenylyl imidodiphosphate, and the subfragments of myosin.

The formation of the ternary complex composed of actin, 5'-adenylyl imidodiphosphate [AMP-P(NH)P], and myosin subfragment 1 (S-1) was studied using the analytical ultracentrifuge with UV optics, which enabled the direct determination of the extent of dissociation of actin.S-1 (acto.S-1) by AMP-P(NH)P. In contrast to the reaction with ATP, at saturating levels of AMP-P(NH)P (1.5 mM), extensive formation of the ternary acto.S-1.AMP-P(NH)P complex occurs at 22 degrees . With 40 muM actin present, AMP-P(NH)P causes almost no dissociation of the acto.S-1 complex at 0.04 M ionic strength, while even at 0.22 M ionic strength one-third of the S-1 remains associated with actin and AMP-P(NH)P in a ternary complex. A detailed study of the binding of S-1.AMP-P(NH)P to actin using the Scatchard plot analysis shows that, at saturation, 1 mol of S-1.AMP-P(NH)P binds per mol of actin monomer. There appears to be no cooperativity occurring as the S-1.AMP-P(NH)P binds along the actin filament, with the possible exception of a slight positive cooperativity when most of the sites on the actin filament are saturated. The turbidity of the ternary complex is identical to the turbidity of acto.S-1 alone. Preliminary experiments with the two-headed subfragment of myosin, heavy meromyosin (HMM), show that the binding of HMM.[AMP-P(NH)P](2) to actin is only about twice as strong as the binding of S-1.AMP-P(NH)P to actin, indicating that the second head contributes very little to the free energy of binding.

Actins↗
PubMed1977

Interaction between Acanthamoeba actin and rabbit skeletal muscle tropomyosin.

The binding of 125I-labeled muscle tropomyosin to Acanthamoeba and muscle actin was studied by ultracentrifugation and by the effect of tropomyosin on the actin-activated muscle heavy meromyosin ATPase activity. Binding of muscle tropomyosin to Acanthamoeba actin was much weaker than its binding to muscle actin. For example, at 5 mM MgCl2, 2 mM ATP, and 5 micronM actin, tropomyosin bound strongly to muscle actin but not detectably to Acanthamoeba actin. When the concentration of actin was raised from 5 micronM to 24 micronM in the presence of 80 mM KCl, the binding of tropomyosin to Acanthamoeba actin approached its binding to muscle actin. As with muscle actin, the addition of muscle heavy meromyosin in the absence of ATP induced binding of tropomyosin in Acanthamoeba actin under conditions were binding would otherwise not have occurred. The most striking difference between the interactions of muscle tropomyosin with the two actins, however, was that under conditions where tropomyosin was found to both actins, its stimulated the Acanthamoeba actin-activated heavy meromyosin ATPase but inhibited the muscle actin-activated heavy meromyosin ATPase.

Actins↗