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Biomedical subjects

R Nathan

Publications and source records attributed to R Nathan.

At least 55 records · Page 3Linked to original sources
PubMed1992

Traumatic disruption of the triangular fibrocartilage complex. Pathoanatomy.

The surgical pathology in 42 cases of traumatic triangular fibrocartilage complex (TFCC) disruption comprised a spectrum of injury resulting in five basic stages of increasingly severe ulnar wrist instability. In all cases, detachment of the articular disk from its ulnar insertion was the principal cause of distal radioulnar joint instability; in 28 (67%), concomitant injury to the adjacent extensor carpi ulnaris sheath, the ulnocarpal ligaments, or the peritriquetral ligaments compounded the instability. Thus, rather than an isolated event, peripheral disruption of the disk often proved the major constituent of multicomponent lesions--lesions consistently suitable for repair. In this series of destabilizing TFCC disruption requiring operative treatment, awareness that some injuries selectively affect the articular disk, whereas others compromise wider zones of wrist anatomy, was essential to successful surgery.

Adolescent↗
PubMed1991

Intranasal fluocortin butyl in patients with perennial rhinitis: a 12-month efficacy and safety study including nasal biopsy.

Fluocortin butyl (FCB) is a recently developed topical intranasal corticosteroid that is inhaled as a powder and has been demonstrated to be well tolerated and to improve symptoms and signs of perennial rhinitis in previous short-term studies. This multicenter, open-label study evaluated the efficacy and safety of FCB during a 12-month treatment period in patients with perennial rhinitis. Treatment was initiated with one inhalation of FCB in each nostril three times a day (total dosage, 3 mg/day). In subsequent months, one third of the patients was maintained at the dosage of 3 mg/day, one third at a lower dosage of 2 mg/day, and the remaining one third of the patients at a larger dosage of 4 to 8 mg/day. Of 109 patients enrolled in the study, 90 patients (82.6%) completed all 12 months of treatment. Symptom and sign scores decreased significantly (p less than 0.001) at the 2-month evaluation compared to scores at baseline, and the improvement was maintained throughout the 12-month study period. After 12 months, greater than 80% of the patients had substantial control of symptoms. Specimens of nasal biopsies, performed at the beginning and end of treatment, revealed a decrease in eosinophils and other cellular infiltrates, a slight tendency of an increase in mast cell counts, and a trend toward normalization of the nasal mucosa. There were few adverse effects. Mean plasma cortisol levels were normal before and after corticotropin stimulation at baseline and after 12 months of FCB therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Intranasal↗
PubMed1991

Classification of distal radioulnar joint disorders.

The wrist is one of the most complex articulations in the human body. The distal radioulnar joint (DRUJ) is particularly controversial, enduring as the area least understood with regard to anatomy and pathomechanics. The popular systems of classifying DRUJ disorders are based on etiology and treatment, but this approach has inspired schemes that are cumbersome, redundant, and incomplete. The need for an improved system prompted us to devise a simplified system that is based on the pathomechanics of dysfunction and the mechanical requirements for optimal joint function.

Humans↗
PubMed1990

The influence of stimulation pulse frequency on the generation of joint moments in the upper limb.

Six muscles of the upper limb were stimulated transcutaneously. This communication reports the influence of the stimulation pulse frequency on the isometric joint moment generated by each muscle. A lower frequency of stimulation, the critical fusion frequency, was found for each muscle at which contractions ceased to be tetanic. This fusion frequency was correlated with muscle function. The magnitude of the joint moment was examined as a function of the stimulation pulse frequency for the six muscles tested. Parabolic curves were found to best fit this relationship; the magnitude of the moment reaching a maximum at typically 50 Hz, and often decreasing at higher frequencies. The slope of the linear portion of the relationship between the generated joint moment and the stimulation current intensity was shown to be a function of the stimulation pulse frequency. This function was found to be similar to the form of the joint moment versus pulse frequency curve. Fatigue curves were plotted at different stimulation frequencies; demonstrating reduced fatigue at lower stimulation frequencies. A model was presented of the fatigue curve as an exponential function of time. We conclude that a stimulation frequency of 15 Hz is optimal for the upper limb muscles with a working range of 15-50 Hz where stimulation frequency is one of the parameters used to modulate the muscle contraction force.

Elbow Joint↗
PubMed1987

The acutely injured wrist. An anatomic basis for operative treatment.

Rational guidelines are provided for the early operative treatment of the severely injured wrist. The prominent anatomic features of the wrist as well as clinically relevant kinematics and pathomechanics are reviewed. Diagnostic and operative techniques applicable to acute injury are described. The authors point out that while the concept of prompt restoration of normal anatomic relationships in the acutely injured wrist may appear to be simple, the clinical application of the concept is quite difficult. However, an accurate diagnosis along with early meticulous surgical intervention will generally lead to a good result.

Biomechanical Phenomena↗
PubMed1986

Effect of acidosis and hypoxia on intestinal blood flow of sheep fetus.

In sheep fetuses 110-130 days of age acidosis (blood pH 6.95; produced by infusion with 1.1 M lactic acid) significantly lowered blood flow (ml/min/100g) to the full thickness wall of the jejunum from 135 +/- 11 to 93 +/- 14 and in the full thickness wall of the ileum from 122 +/- 13 to 95 +/- 11. The decrease was mainly due to the decline in blood flow to mucosa of the segment, where flow decreased from 182 +/- 20 to 83 +/- 14 in the jejunum and from 130 +/- 10 to 107 +/- 9 in the ileum. Fetal hypoxemia (PaO2 of 14.9 mm Hg; induced by allowing ewes to breath 11.1% O2 and 88.9% nitrogen) reduced blood flow only to the jejunal mucosa from 142 +/- 14 to 99 +/- 16. The reduction in blood flow to the full thickness wall of the jejunum and the ileum did not change significantly from the control period, when PaO2 was 25 mm Hg.

Acidosis↗
PubMed1985

Intestinal calcium absorption is enhanced by D-glucose in diabetic and control rats.

The effect of glucose on intestinal absorption of calcium was studied in the jejunum and ileum of control, diabetic (streptozotocin-induced), and insulin-treated diabetic rats. Intestinal absorption was determined in vivo using an in situ one-pass perfusion technique. In the jejunum of control and diabetic rats, net absorption and unidirectional lumen to mucosa flux of calcium and net absorption of water were significantly greater during perfusion of an isotonic NaCl solution, containing 15 mmol/L of glucose, than during perfusion of the same solution containing 15 mmol/L of mannitol instead of glucose. To determine if net absorption of calcium and water were related, the jejunum was perfused with a hypotonic solution (260 mosmol/kg) in separate groups of rats. Although net absorption of water was equivalent during perfusion of the hypotonic solution to that noted during perfusion of the isotonic glucose-containing solution, rate of absorption of calcium was not enhanced. Thus, it appeared that, if the enhancement in absorption of calcium by glucose was an effect on the passive absorption of calcium, it was through a mechanism not related to passive absorption of water. As expected, jejunal absorption of calcium was lower in diabetic than in control rats. Because in diabetic rats the metabolism of vitamin D to its active metabolite, 1,25-dihydroxy vitamin D, is defective, the enhancement in absorption of calcium by glucose did not appear to be due to a mechanism influenced by vitamin D metabolism. In the ileum, rate of absorption of calcium was lower than in the corresponding jejunum and was not significantly altered by the presence of glucose in the perfusion solution, by perfusion of a hypotonic solution, or by the diabetic state. The mechanism of action of glucose on calcium absorption in the jejunum needs to be studied further.

Animals↗
PubMed1985

Intrahepatic biliary tract abnormalities in children with corrected extrahepatic biliary atresia.

Three children with surgically corrected extrahepatic biliary atresia developed recurrent cholangitis associated with bile lakes that failed to drain via the hepatoportoenterostomy. Surgical or percutaneous drainage of these cysts was followed by both resolution of the infection and spontaneous internal drainage. We postulate that the ongoing inflammatory process resulted in intrahepatic biliary obstruction, which caused cholangitis and bile cysts. Successful treatment required not only antibiotics but drainage of the bile lakes. Development of bile cysts is a new cause of recurrent cholangitis seen in extrahepatic biliary atresia.

Bile↗
PubMed1984

Computed tomography and aging: results in a normal elderly population.

CT studies on 212 normal elderly individuals were analyzed for ventricular enlargement and cortical atrophy. Results show a positive correlation between ventricular enlargement and age with greater degrees of ventricular enlargement and cortical atrophy in men as compared to women. While some degree of atrophy is common in normal elderly individuals it is mild, minimal, or noexistent in 86%.

Age Factors↗
PubMed1984

Association of beta hydroxybutyric acidosis with isoniazid intoxication.

Acute metabolic acidosis associated with accumulation of lactate has been previously reported in isoniazid (INH) intoxication. To our knowledge, association of INH toxicity with beta-hydroxybutyric acidosis has not been demonstrated previously. The present report documents the occurrence of beta-hydroxybutyric acidosis in patients with INH intoxication. The reason for the lack of previous reports of this association is not clear, although failure to measure plasma beta-hydroxybutyrate levels in previous studies is a likely possibility. Our patients received intravenous sodium bicarbonate, anticonvulsants and dialysis which resulted in complete reversal of metabolic acidosis and other manifestations of INH toxicity.

3-Hydroxybutyric Acid↗
PubMed1983

Critical comparison of transcutaneous PO2 and tissue pH as indices of perfusion.

A critical laboratory evaluation of transcutaneous PO2 monitoring and tissue pH monitoring in lower abdominal island flaps based on the superficial inferior epigastric vessels in rabbits revealed that transcutaneous PO2 values correlate poorly with tissue survival under circumstances of decreased arterial inflow. The inability of the transcutaneous PO2 monitor to accurately predict viability of the flaps in this study is attributed to physiologic changes in the microcirculation and not to instrument error. Tissue pH was, in all instances, a reliable index of the perfusion status of the flaps.

Abdomen↗
PubMed1982

Intestinal maturation: in vivo loss of calcium in suckling and adult rats.

Intestinal permeability to Ca is greater in infant than in older rats, predisposing the infant rat to hypocalcemia. The present studies compared in suckling and adult rats the amount of Ca lost into the intestinal lumen in relation to plasma Ca during an acute 2-h in vivo recirculation perfusion of the jejunum and ileum with an isotonic NaCl solution either free of or containing CaCl2. Rats had been injected with radioactive 45CaCl2 24 h prior to the perfusion. Secretion of Ca was determined from rate of appearance of 45Ca into the lumen. During perfusion of the solution free of Ca, rate of secretion of Ca into the intestinal lumen (both jejunum and ileum) was about the same in the suckling and the adult rats, about 7.3 mumol/2 h. However, rate of secretion based on body weight was 10-fold greater in the suckling than in the adult rats. The relatively greater loss of Ca in suckling rats resulted in a significant drop of serum Ca, from 2.95 mumol/ml to 2.02 mumol/ml. In adult rats serum Ca was maintained to within normal limits. During perfusion of solutions containing 2 mmol/L of CaCl2, all rats absorbed Ca, and absorption rates were greater in the jejunum and ileum of the suckling than of the adult rats. Thus, because of the possibility of excessive loss of Ca through the intestinal tract, it appears advisable to allow young infants enough dietary Ca to maintain concentration of ionized Ca in the intestinal lumen to above that in serum.

Animals↗