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Biomedical subjects

R A Kaplan

Publications and source records attributed to R A Kaplan.

At least 37 records · Page 2Linked to original sources
PubMed1984

Measurement of spatial stability of spark position in burst-mode breakdown with the Nd:YAG laser.

Measurements to determine the precise position of the spark produced by optical breakdown in ocular media with a repetitive sequence of pulses from a Nd:YAG laser have been made. The results show that the location of the spark along the beam axis remains fixed within +/- 10 micrometers (the resolution of the experiment) for pulses with a time separation of 20 milliseconds, indicating that the surgical effects of a sequence of pulses can be cumulative.

Lasers↗
PubMed1981

In vitro stimulation of 25-hydroxycholecalciferol 1 alpha-hydroxylation by parathyroid hormone in chick kidney slices: evidence for a role for adenosine 3',5'-monophosphate.

We studied the effect of parathyroid hormone (PTH) on the in vitro conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol [1,25-(OH)2D3] by kidney slices from vitamin D-deficient chicks. Bovine PTH (bPTH) stimulated 1,25-(OH)2D3 production at low concentrations, with maximal stimulation (65%) at a concentration of 25 ng/ml bPTH in the absence of theophylline. Higher concentrations of bPTH resulted in less stimulation. The addition of 5 mM theophylline to the incubation buffer decreased basal 1,25-(OH)2D3 production but potentiated the stimulation of 1,25-(OH)2D3 production by PTH. Maximal stimulation (170%) was observed with 2 ng/ml bPTH in the presence of theophylline. Maximal stimulation of cAMP production by the kidney slices required 2- to 3-fold larger concentrations of bPTH. However, cAMP by itself stimulated 1,25-(OH)2D3 production, with maximal stimulation (70%) at 10(-7)-10(-5) M cAMP. We conclude that stimulation by PTH of 1,25-(OH)2D3 production can be potentiated by theophylline and mimicked by cAMP. However, such stimulation occurs at PTH concentrations lower than that required for optimal stimulation of adenylate cyclase activity.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1981

Parathyroid hormone has a positive inotropic action in the rat.

Parathyroid hormone (PTH: synthetic bovine, amino terminus 1-34 amino acids) demonstrates a positive inotropic action on the isolated papillary muscle of the rat heart. The effect was evident at PTH concentration of 10(-12)M, and the maximum inotropic effect occurred with PTH concentrations greater than 10(-11)M. Biologically inactive PTH (PTH treated with H2O2) was without effect. The inotropic effect of PTH was partially blocked by propranolol and also suppressed in the papillary muscle of the rat pretreated with reserpine. Methoxyverapamil completely blocked the inotropic action of PTH. PTH was without effects on adenylate cyclase activity of the myocardium. Results show the presence of an inotropic action of PTH in vitro and suggest that this action of PTH is partially mediated by releasing the endogenous myocardial norepinephrine which exerts a positive inotropic effect via beta-adrenergic stimulation and by an increase in Ca++ influx across plasma membranes, but independent of adenylate cyclase activation. The inotropic action of PTH may be of significance in normal cardiac function.

Animals↗
PubMed1980

Metabolism of C4 and factor B in rheumatoid arthritis. Relation to rheumatoid factor.

Metabolic turnover determined by radioiodide labeled C4 and Factor B was studied in 18 patients with rheumatoid arthritis (RA) and 19 normal control subjects as a means of estimating the relative ratio of consumption of components in the classical and alternative pathways of complement activation. Predominance of fractional catabolic rate (FCR) of C4 over Factor B was demonstrated with differentially labeled C4 and Factor B. The hypercatabolism occurred in the extravascular space. C4 FCR correlated significantly with rheumatoid factor (RF) determined in a hemolytic assay (rs = 0.72), measured as IgG RF (rs = 0.57), and as IgM RF (rs = 0.45). There were no significant correlations with several other antibodies measured. These results are consistent with the hypothesis that RA is a systemic, extravascular immune complex disease, in which RF immune complexes play a significant pathogenetic role principally via activation of the classical pathway of complement.

Adult↗
PubMed1980

Frentizole therapy in systemic lupus erythematosus.

Seven corticosteroid dependent patients with active systemic lupus erythematosus (SLE) were given frentizole in order to assess its effect on their clinical manifestations. Three patients exhibited slight clinical improvement, 2 patients did not change, and 2 deteriorated. Five of the 7 patients developed subclinical and reversible liver damage related to frentizole. This study, although preliminary and uncontrolled, suggests that frentizole is of limited value in the management of patients with SLE.

Adult↗
PubMed1980

Pathogenetic role of 1 alpha,25-dihydroxyvitamin D in sarcoidosis and absorptive hypercalciuria: different response to prednisolone therapy.

Intestinal hyperabsorption of calcium (Ca) is frequently observed in sarcoidosis and is characteristic of absorptive hypercalciuria (AH). The potential pathogenetic role of 1 alpha,25-dihydroxyvitamin D [1,25(OH)2D] in these two conditions was sought by a careful assessment of the circulating concentration of this vitamin D metabolite and various measures of Ca metabolism before and after prednisolone therapy. In eight patients with sarcoidosis, prednisolone treatment (50 mg/day for 8 days) produced a significant fall in serum 1,25(OH)2D [4.8 +/) 1.9 to 3.3 +/- 1.0 (SD) ng/dl; P less than 0.025], concomitant with a significant decrease in the fracitional intestinal Ca absorption (alpha) from 0.58 +/- to 0.14 to 0.46 +/- 0.13 (+/- SD; P less than 0.005). Urinary Ca and serum parathyroid hormone did not change significantly. However, in six patients with AH, prednisolone therapy resulted in a nonsignificant rise in serum 1,25(OH)2D from 3.6 +/- 0.7 to 4.4 +/- 1.0 ng/dl and no significant fall in alpha (from 0.73 +/- 0.08 to 0.70 +/- 0.10). Urinary Ca was significantly increased in AH patients from 230 +/- 35 to 343 +/- 74 (SD) mg/day (P less than 0.005), while serum parathyroid hormone rose slightly. Serum 1,25(OH)2D and alpha were significantly correlated (r = 0.543; P less than 0.05) for patients with sarcoidosis but not in AH patients. These results suggest that the hyperabsorption of calcium in sarcoidosis is dependent on the serum concentration of 1,25(OH)2D, while in AH it may result from additional vitamin D-independent processes.

Calcitriol↗
PubMed1980

Activation of the fourth component of complement (C4): assessment by rocket immunoelectrophoresis and correlation with the metabolism of C4.

The classical pathway of complement (C) is activated in several diseases, and this activation characteristically involves the activation of C4, the fourth component of C. Since activation of C4 ultimately produces the polypeptide fragment C4d, we have applied immunoelectrophoresis in gels containing antibodies that precipitate C4d and C4 (rocket immunoelectrophoresis) as a means of detecting and quantitating C4 activation. Plasma C4 produced a single precipitin line after rocket immunoelectrophoresis, whereas plasma containing C4d produced two precipitin lines corresponding to C4d and C4. The areas enclosed by the respective precipitin line(s) were quantitated by planimetry and approximated the amounts of C4d and C4 present in the specimen. The ratio of the areas of C4d/C4 as measured in this analysis correlated significantly with the in vivo metabolism of radiolabeled C4. Our method detected C4d in the plasmas of some patients with rheumatoid arthritis, hereditary angioedema, systemic lupus erythematosus, or chronic urticaria with hypocomplementemia. These studies indicated that determination of the C4d/C4 ratio is useful in the evaluation of in vivo C activation and also may be applicable to the study and management of diseases associated with C activation.

Angioedema↗
PubMed1979

The physiologic hyperparathyroidism of pregnancy. Is it primary or secondary?

Controversy exists over whether the increase in maternal serum parathyroid hormone levels observed during the second half of pregnancy is due to autonomous parathyroid function or is secondary to changes in maternal serum ionized calcium levels. In order to study this problem further, 9 subjects were followed serially throughout normal pregnancy. Total serum calcium, ionized calcium, parathyroid hormone (PTH), calcitonin, and albumin levels were measured monthly. Six of these subjects had the studies repeated 6 weeks postpartum. Serum ionized calcium levels were found to decrease from 3.81 +/- 0.12 mg/dl to 3.63 +/- 0.18 mg/dl between 21 and 25 weeks' gestation. This decrease was significant at P less than 0.01. The ionized calcium remained in this lower range until term. A significant return to 3.77 +/- 0.1 mg/dl was observed 6 weeks postpartum. Serum PTH levels showed a significant rise after 21 weeks' gestation (P less than 0.05). No serial change in serum calcitonin was observed during pregnancy, although the mean level of the group was significantly higher than in nonpregnant controls (P less than 0.01). The increase in maternal serum PTH observed during pregnancy appears to be due in part to a decrease in maternal serum ionized calcium.

Adolescent↗
PubMed1978

Selective effects of thiazide on intestinal absorption of calcium and adsorptive and renal hypercalciurias.

The effect of long-term thiazide therapy on the intestinal Ca absorption was measured in 10 well-defined cases of absorptive hypercalciuria with intestinal hyperabsorption of Ca and 8 with renal hypercalciuria ("renal leak" of Ca), many of whom had hyperabsorption of Ca. In most cases of absorptive hypercalciuria, the intestinal hyperabsorption of Ca persisted during treatment, despite restoration of normal urinary Ca. In contrast, the intestinal Ca absorption decreased significantly during thiazide therapy in 7 of 8 patients with renal hypercalciuria commensurate with the "correction" of the renal leak of Ca and secondary hyperparathyroidism. The results support the hypothesis that the intestinal hyperabsorption of Ca in absorptive hypercalciuria may be primary, whereas that in renal hypercalciuria may be associated with the hyperparathyroid state.

Adult↗
PubMed1978

Prostaglandin-mediated hypercalcemia in transitional cell carcinoma of the bladder.

A patient with known transitional cell carcinoma of the bladder and hypercalcemia was evaluated for urinary prostaglandin levels when no bone metastases or elevated parathormone levels could be demonstrated. Urinary levels of prostaglandin E metabolite were assessed in relation to serum and urinary calcium levels during treatment. The serum calcium levels decreased from the 13.0 mg. per cent range whenever the rpimary tumor was manipulated (transurethral resection) or when other treatments directed at the tumor were used (radiation therapy and chemotherapy). Serum and urinary calcium levels, and urinary prostaglandin E metabolite decreased when 3 gm. aspirin were given daily. These data suggest that the somewhat unusual hypercalcemia in our patient was caused by a prostaglandin-secreting transitional cell carcinoma. Prostaglandin-secreting tumors are reviewed herein.

Animals↗
PubMed1978

Metabolism of factor B of serum complement in rheumatoid arthritis.

An increased rate of catabolism of radio-iodinated Factor B has been shown in five out of ten patients with rheumatoid arthritis. Serum levels of Factor B were normal, the increased catabolism being matched by increased synthesis. The patients showing high catabolic rates had more manifestations of extra articular disease than did those with normal catabolic rates and they had higher rheumatoid factor titres. In seven patients, the catabolic rate for Factor B correlated significantly with the rate of IgG catabolism. In this series, the Raji-cell assay for immune complex-like material was in the normal or near normal range in all but one patient.

Adult↗
PubMed1977

Peripheral diabetic neuropathy treated with amitriptyline and fluphenazine.

The pain of diabetic peripheral neuropathy responds poorly to current modes of treatment. We treated eight patients with this disorder whose pain was refractory to standard regimens but who experienced remarkable pain relief within two to five days after treatment with fluphenazine hydrochloride, amitriptyline hydrochloride, or a combination of the two. In four patients whose regimens were discontinued, pain recurred within two days and again remitted on reinstitution of the drug regimens. These findings suggest that fluphenazine alone or in combination with amitriptyline may be of benefit in treating the painful peripheral neuropathy associated with diabetes.

Adult↗
PubMed1977

Bacterial meningitis. Limitations of repeated lumbar puncture.

A retrospective chart review of 47 pateints with bacterial meningitis was conducted with respect to current guidelines used to define an adequate duration of antimicrobial therapy. Fifty percent (19/38) of patients had an inadequate response to therapy as defined by repeated lumbar puncture (LP) findings (ie, a cerebrospinal fluid (CSF) blood cell count greater than 50/cu mm and/or a CSF glucose value less than 45 mg/100 ml) at the end of therapy. No cases of relapse were seen. Persistent CSF abnormalities were not associated with the presence of complicating disease but were associated with prolongation of antimicrobial therapy beyond 13 days. Patients having persistent CSF abnormalities at the time antibiotics were stopped had a higher CSF blood cell count and a lower glucose value on initial lumbar puncture than those not having persistent abnormalities (P less than .001). These results emphasize the limitations of the role of repeated LP in defining an adequate duration of antimicrobial therapy.

Adolescent↗