Effects of [Na+], [Cl-], carbonic anhydrase, and intracellular pH on corneal endothelial bicarbonate transport

Sodium removal from the solution bathing the isolated rabbit corneal endothelium caused a reduction in both unidirectional and net flux of bicarbonate, whereas chloride withdrawal from the solution had no effect on the net bicarbonate flux but increased the unidirectional fluxes. These data correlate with previously published data on the effects of similar solution manipulations on both fluid movement and potential difference across the endothelium and strongly implicate bicarbonate as the primary ion involved in the maintenance of corneal hydration. Carbonic anhydrase (1 mg/ml) added to the solution bathing both sides of the endothelium markedly increased unidirectional and net bicarbonate fluxes, possibly by maintaining a high bicarbonate/CO2 concentration close to the membrane and thereby eliminating chemical gradients in the unstirred layer adjacent to the membrane. Determinations of intracellular pH with the 5,5-dimethyl-2,4-oxazolidine-dione method indicate that at more acid ambient conditions there is a lesser gradient between cell and bathing medium for H+; similar ambient conditions in other experiments resulted in larger unidirectional bicarbonate fluxes than at neutral pH. The data are suggestive of a nonvectorial H+-HCO3- exchange occurring across the endothelial cellular membranes.

The kinetics of ionophore X-537A-mediated transport of manganese through dipalmitoylphosphatidylcholine vesicles. A 1H-NMR study

We have studied the kinetics of ionophore X-537A-mediated transport of manganese ions into small unilamellar vesicles formed from dipalmitoylphosphatidylcholine. To follow the transport we used the paramagnetic effect of manganese on the 1H-NMR signal from choline trimethylammonium groups on the inner phospholipid monolayer. The transport of only one manganese ion produces an intravesicular concentration which is high enough (approx. 1 mM) to substantially broaden this signal. The observed signal thus arises predominantly from those vesicles which contain no manganese. Therefore, as manganese is transported into the vesicles the observed signal decreases in intensity, but does not broaden. The initial time-dependence of the intensity of the signal, S(t), can be approximated by the simple first-order rate law: S(t) = S(0) exp(-k't), where k' is the probability per unit time for the transport of a manganese ion from the external medium to the intravesicular space. From the dependence of k' on the ionophore X-537A concentration we conclude that manganese is transported into the vesicles via both 1 : 1 and 2 : 1 complexes with ionophore X-537A. At low ratios of ionophore X-537A to vesicles transport via the 1 : 1 complex predominates; at high ratios transport via the 2 : 1 complex predominates. From the dependence of k' on manganese concentration we determined that under our conditions the equilibration of ionophore X-537A between vesicles is much faster than the transport of manganese through the vesicles. Lastly, from the dependence of k' on temperature, we conclude that the ionophore X-537A-mediated transport of manganese into the dipalmitoylphosphatidylcholine vesicles is very sensitive to the gel-liquid crystalline phase transition.

Leg-length discrepancies in monoarticular and pauciarticular juvenile rheumatoid arthritis

A retrospective study was performed to determine the course of limb-length discrepancies occurring in patients with monoarticular and pauciarticular juvenile rheumatoid arthritis. Data were assessed on thirty-six patients followed to skeletal maturity, on fifteen patients who had not reached skeletal maturity but who had been followed for four years or more, and on forty-nine patients followed for three years or less. In seventy-two of the total of 100 patients the onset of the disease occurred before they were five years old, and ninety patients had involvement of the knee. All patients in whom the disease developed before the age of nine had overgrowth of the involved extremity, but that overgrowth never exceeded 3.0 centimeters. The major discrepancy developed within the first three or four years and either increased very slowly thereafter, remained level, or decreased. Of the thirty-six patients who were followed to skeletal maturity, in twenty-nine a discrepancy of 1.5 centimeters or more developed at some time during the period of assessment. Twelve of the thirty-six patients had diminution of the discrepancy to the extent that epiphyseal arrest was not required. Fifteen eventually had an epiphyseal arrest. Rapid premature closure of the epiphyseal growth plate occurred only in those patients in whom the disease developed after the age of nine years. This led to immediate shortening of the involved side and on occasion to marked limb-length discrepancies.

Analogous effect of protons and inositol hexaphosphate on the alteration of structure of nitrosyl fetal human hemoglobin

We have determined the low temperature EPR spectra and room temperature ligand dissociation rate constants of human NO-hemoglobins F and A as a function of pH and inositol hexaphosphate levels in order to assess the contribution of a quaternary structural equilibrium in the two proteins to their spectral and functional properties. Our results are consistent with an increased stability of a ligated low affinity structure in the fetal protein; the functional properties of this structure appear to be essentially the same in the two hemoglobins, even though its stability relative to a high affinity conformation is different. The pH dependence of the NO dissociation constant in both adult and fetal hemoglobin can be assigned primarily to the pH-dependent equilibria of high and low affinity forms as monitored by EPR.

[Simultaneous occurrence of juvenile diabetes and Addison's disease (author's transl)]

The occurrence of diabetes mellitus and Addison's disease together is discussed by the authors. The female patient described here had diabetes at the age of four; Addison's disease appeared when the patient was 19 years old. Four years prior to the appearance of Addison's disease, an ophthalmoscopic examination revealed microaneurysms. The examination of the fundus of the eye was negative when Addison's disease, was diagnosed. An HLA-B8 antigen positivity was established. The authors discussed the pathogenetic relationship of HLA-B8 antigen positivity, diabetes mellitus, and Addison's disease.

Relative stabilities of the two quaternary conformations of human fetal hemoglobin

The pH dependence of several functional properties of human fetal and adult hemoglobins have been studied to determine the relative stabilities of the high and low affinity (R and T) quaternary conformations of the two proteins under different conditions. Fetal aqumethemoglobin undergoes changes in sulfhydryl reactivity, absorption spectrum, and circular dichroism in the presence of insitol hexaphospahte which are consistent with a transition from the R to T quaternary state, but only at pH values below 6.8. In adult hemoglobin this transition can be induced pH values below 7.2. Even in the absence of phosphates, the ultraviolet (uv) circular dichroism spectrum of fetal aquomethemoglobin at low pH indicates the presence of some T conformation. The initial value for the second-order rate constant for combination of fetal deoxyhemoglobin with carbon monoxide is comparable to that for adult hemoglobin in the absence of organic phosphates and is not reduced by organic phosphates as much as that for the adult protein. The apparent first-order rate constant for dissociation of CO from fully liganded fetal hemoglobin, measured by replacement with NO, increases threefold in the absence of organic phosphates, and fourfold in the presence of organic phosphates, with decreasing pH; the midpoint of the pH dependent transition occurs around 6.8. A similar increase in the apparent first-order rate constant for O2 dissociation as measured by replacement with CO, can also be seen with decreasing pH. NO-hemoglobin F can be converted to the T state even when fully liganded simply by lowering the pH, as judged by uv circular dichroism, visible difference spectrum in the region of the alpha and beta bands, and a dramatic increase in the rate of NO dissociation, measured by replacement with CO in the presence of dithionite. These results are all consistent with a model for fetal hemoglobin in which the organic phosphate site may be functionally weakened by replacement of a residue involved in ionic interactions with the negatively charged phosphate groups, but in which the low affinity T conformation is intrinsically more stable than that of adllt hemoglobin. According to this model,the differences between fetal and adult hemoglobin can be accounted for primarily in terms of the relative stabilities of R and T conformations in each of the proteins with differences in the intrinsic properties of the individual conformations contributing effects of only secondary importance.

Formation of planar bilayer membranes from lipid monolayers. A critique

The formation of planar bilayer membranes from lipid monolayers as described by Montal and Mueller (Proc. Natl. Acad. Sci. 1972. 69:3561) is analyzed. Bilayers absolutely free of alkane solvents or other nonpolar hydrocarbons can be formed on polytetrafluoroethylene (PTFE) (e.g. Teflon) septa only if certain boundary conditions are satisfied. Measurements have been made of the contact angles between monolayer-coated water and PTFE in the presence and absence of alkane solvents. The measurement suggest that the boundary conditions for formation of stable bilayers can be satisfied only when a nonpolar solvent is present. We conclude that the bilayer must be surrounded by a torus of alkane solvent, petroleum jelly, or silicone grease depending upon the details of technique used to form the bilayer. The non-polar solvent used in the formation of the bilayer may or may not be present in the bilayer depending upon the water solubility and size of the solvent molecule relative to the size of the alkyl chain of the lipid. Detailed sketches describing the formation of bilayers from monolayers are presented.

Studies with the International Pyrogen Standard on the sensitivity and reproducibility of pharmacopoeial pyrogen testing

Rabbits, 27 or 36 in each experiment, were injected with the International Pyrogen Standard (I.P.St.) in different seasons. The maximum temperature rises were registered, randomized and interpreted according to the requirements of the B.P. (1973), U.S.P. (1970), P. Hung. (1970) and P. Nord. (1962). Although the dose of 3.5 ng kg(-1) I.P.St. proved to be non-pyrogenic as tested in summer, when tested in winter the same dose was qualified pyrogenic (to be rejected) by up to one third of the combinations by the criteria of the four Pharmacopoeias. In the spring experiment "to be rejected" qualifications predominated as based on the response of large groups of rabbits. Exclusion of the rabbits showing low sensitivity (before randomization) barely influenced the results with 3.5 ng kg(-1) I.P.St. in the experiment in which the mean temperature rise was 0.49 degrees. If, however, the mean temperature rise was higher (0.57 or 0.69 degrees), such a selection practically resulted in the disappearance of "passable" qualifications in the triplet groups and a great predominance of "to be rejected" qualifications in the larger groups. The dose 7.0 ng kg(-1) consistently proved to be pyrogenic in large groups of rabbits.

Calculation of the percentage of a narcotic gas to permit abolition of the high pressure nervous syndrome

A theoretical method is derived for computation of the interactin of pressure and a weak anesthetic such as nitrogen or other narcotic gases in a two-dimensional material so as to prevent signs and symptoms of the high pressure nervous syndrome. A ratio of one part nitogen to 9 parts helium (pressure) is derived, which is in excellent agreement with previous human experiments in men at 31 ATA, with PO2 = 0.5 ATA.

[The transurethral electroresection with continuous waterflow through a new resectoscope (author's transl)]

We report on the experiences of more than 100 resections of the adenoma of the prostata gland with a new resectoscope is made known. This offers the advantages of the continuous waterflow by maintaining physiological bladder pressure. The possibility of permanent resection leads to 1. a considerably shortened operation time and 2. abolition of the TUR syndrom 3. The requirement of electroresection is facilitated.

Lubrication Mechanism of Hip Joint Replacement Prostheses

A laboratory study has been made of the lubrication and friction characteristics of a plastic on metal (Charnley-Muller) and a metal on metal (McKee-Farrar) total hip joint replacement prostheses. The results show the effect of lubricant, speed, and load on the performance of the joints. Under a 560 lb load the coefficient of friction of the plastic to metal joint was lower than that of the metal to metal at speeds up to the equivalent of fast walking. Bovine serum and synovial fluid, as well as human serum albumin were found to be good lubricants of both types of prostheses. The frictional force produced by the metal on metal prosthesis increased linearly with load, in both the dry and lubricated states. This was not the case with the plastic to metal joint. The results show that at low physiological loads the effort required to articulate the prostheses are comparable while at higher loads the friction force of the metal to plastic is significantly lower. Friction readings taken with no lubricant indicate the serious damage which would result in the human body if a metal to metal prosthesis became devoid of liquid. The load and speed behavior of the prostheses require different interpretation of the data than presently postulated.