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J J Lim

Publications and source records attributed to J J Lim.

29 records · Page 2Linked to original sources
PubMed1976

Standing-gradient osmotic flow. Examination of its validity using an analytical method.

The solutions to the non-linear differential equations governing solute-solvent coupling in the intercellular spaces of epithelial layers have been obtained by using an analytical method, rather than the usual numerical ones. When the present series solution includes second-order correction terms, the concentration and velocity profiles obtained by the analytical method agree very well with those coming from numerical solutions. This method has further allowed us to examine the standing-gradient hypothesis when applied to the backwards fluid transport system of the corneal endothelium. With the information presently available for the relevant parameters (osmotic permeability, rate of transport, radius and length of the spaces, and location of the pumping sites), near-isotonicity of the transported fluid would not be explained by the standing-gradient model.

Biological Transport↗
PubMed1974

Role of cations, anions and carbonic anhydrase in fluid transport across rabbit corneal endothelium.

1. A small electrical potential difference (541 +/- 48 muV, aqueous side negative) across rabbit corneal endothelium has been recently found. Its dependence on ambient [Na(+)], [K(+)], [H(+)] and metabolic and specific inhibitors was examined.2. Changes in concentration of the ions above either were known or were presently shown to affect the rate of fluid transport across this preparation (normal value: 5.2 +/- 0.4 mul./hr.cm(2)). Ionic concentration changes were also found here to influence potential difference in the same way as fluid transport. In the cases tested, the effects on both fluid transport and potential difference were reversible.3. Fluid transport and potential difference were both decreased or abolished in absence of Na(+), K(+) and HCO(3) (-), and when [H(+)] was decreased. Fluid transport and potential difference were saturable functions of [HCO(3) (-)] and half-saturation occurred in both cases at about 13 mM-HCO(3) (-). The potential difference was also a saturable function of [Na(+)] (half-saturation around 15 mM). There was a pH optimum for potential difference in the range 7.4-7.6. Lower pH values decreases the potential difference and the fluid transport, and a small (-100 muV) reversed potential was observed in the range of 5.3-5.5.4. Total replacement of Cl(-) by HCO(3) (-) or SO(4) (2-) produced no impairment on either fluid transport or potential difference.5. Carbonic anhydrase inhibitors (ethoxyzolamide 10(-5) or 10(-4)M and benzolamide 10(-3)M) produced a 40-60% decrease in the rate of fluid pumping. In contrast, ethoxyzolamide 10(-4)M or acetazolamide 10(-3)M did not produce any change in the potential difference. NaCN and Na iodoacetate (both 2 mM) eliminated the potential difference in 1-1.5 hr while in controls it lasted for 5-6 hr.6. Ouabain (10(-5)M) abolished the potential difference in less than 10 sec when added to the aqueous side, which suggests the existence of an electrogenic pump. This extremely fast time transient can be accounted for by the accessibility and simple geometry of the present monocellular layer. Ouabain abolished also the reversed potential difference observed at low pH.7. The data are interpreted in terms of a scheme similar to that advanced for other epithelia and in which (a) H(+) would be pumped into the intercellular spaces, while Na(+) and CO(2) would enter into the cells, and (b) Na(+) would be subsequently pumped into the aqueous humour, producing as a result the fluid movement observed. The actual origin of the potential difference is further discussed in terms of two contrasting possibilities: (i) one or more electrogenic pumps, and (ii) a neutral pump which would create a diffusion potential across ;leaky' intercellular junctions.

Animals↗
PubMed1971

An investigation of the bound water in tendon by dielectric measurement.

The dielectric constant of natural tendon in the frequency range of 200 Hz to 100 kHz has been determined as a function of temperature (300-450 degrees K) for water concentrations ranging from about 6 to 16% by weight. The results compare well with the approach taken by Haggis and his coworkers. Based on the assumption that at low concentration of water the probability of water-water bonding is small and hence may be disregarded, a structure for water in the collagen matrix is proposed in which the water is either bonded in one of four possible states to the polar groups of the polypeptide chains, or is unbound. In determining the distribution of the water among these states an approach similar to that of Haggis and his co-workers, in conjunction with the order-disorder theory of Bragg and Williams, is used. The number of water molecules per unit volume is then determined experimentally by relating it to weight loss as a function of temperature, as determined by thermogravimetric analysis. The dispersion which is normally found in dipolar substances has not been found for tendon. A maximum in the value of the dielectric constant is observed to occur between 25 and 80 degrees C, the temperature depending upon the heating rate.

Animals↗
PubMedDate not supplied

Clinical significance of neck node metastasis in squamous cell carcinoma of the maxillary antrum.

PURPOSE: To further clarify the clinical significance of neck node metastasis in squamous cell carcinoma of the maxillary sinus (maxillary SCC). MATERIALS AND METHODS: The medical charts of the 116 patients with maxillary SCC were retrospectively reviewed. Twelve patients (10.3%) presented initially with neck node metastases, and 14 (13.5%) of 104 node-negative patients subsequently developed regional recurrence during the follow-up period. The high-risk factors for neck node metastasis, patterns of regional failure, and survival for node-positive patients were analyzed with the patient cohort that had largely been treated with radiation alone. RESULTS: Of the various factors, the tumor extension to the nasopharynx or oral cavity was the statistically significant determinants predictive of neck node metastasis at the initial diagnosis. During the follow-up period, regional failure was far less common than local failure (19.0% v 68.1%), and the majority of regional failures were accompanied by local recurrences. The oral cavity extension and control status of local disease were the high-risk factors for subsequent development of regional recurrence in node-negative patients. The overall 5-year survival rate for node-positive patients (16.7%) showed a poorer outcome compared with that for node-negative patients (31.3%), but it was similar to that of T4N0 patients (26.6%). Although patients who subsequently developed neck node recurrence during follow-up represented a dismal prognosis, uncontrolled local diseases in these patients still remained a major problem, resulting in a poor prognosis. CONCLUSIONS: Despite an unfavorable prognosis of patients with neck node metastasis, an aggressive trial to achieve maximum local control of the primary tumor was considered to be more important than elective neck treatments.

Adult↗
PubMedDate not supplied

Effects of bicarbonate on the potential difference across the rabbit corneal endothelium.

The electrical potential difference across the rabbit corneal endothelium is dependent on the concentration of HCO-3 in the bathing solution. When the HCO-3 was present only on the stromal side, the average normal potential difference of 570 +/- 20 microV (n = 18, aqueous negative) was observed. On the other hand, when the HCO-3 was present only on the aqueous side, the average potential difference was 124 +/- 11 microV (n = 8). By replacing NaHCO3 in the solution with NaCl and KHCO3 with KCl, the potential difference was 32 +/- 7 microV (n = 16). The potential difference reached no saturation level but increased as a function of increasing ambient [HCO-3] up to 70 mM while the electrical resistance remained constant. The near abolishment of the potential difference in the absence of HCO-3 in the solution suggests that endogenous as well as exogenously generated CO2 from air may play at most a minor role in generation of the potential difference. A model to explain the results observed is proposed.

Action Potentials↗