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Biomedical subjects

J Hurwitz

Publications and source records attributed to J Hurwitz.

279 records · Page 16Linked to original sources
PubMed1966

Methylation of DNA.

The methylated bases of DNA are formed by the transfer of the methyl group from S-adenosylmethionine to a polynucleotide acceptor. This transfer is catalyzed by highly specific enzymes which recognize a limited number of available sites in the DNA. The mechanism for the recognition is presently unknown. In some instances, there is evidence that other cellular components, such as lipopolysaccharides, can influence the methylation reaction. Certain bacteriophages induce new methylases upon infection of their hosts. Phage T3 is unique in establishing an environment in which methylation of neither the phage nor the host nucleic acid can occur. By superinfecting T3-infected cells with other phages, the latter can be obtained with methyl-deficient DNA. Although a great deal is known about the enzymology of the methylation reaction, and there appears to be a strong correlation between the in vitro and in vivo reactions, studies in which DNA is either supermethylated or totally unmethylated have not yielded any insight as to what the possible function of the methylated bases may be.

Alkylation↗
PubMedDate not supplied

Management of groin hernias by laparoscopy.

The surgical treatment of groin hernias continues to undergo technical modifications. The introduction of minimally invasive surgery had added a possible new dimension, replacing an inguinal approach by laparoscopy. Conceived some 15 years ago, the thesis was subjected to a clinical trial where coincidental abdominal hernial openings were closed at laparotomy. This study was followed by an experimental study at which time the openings were closed laparoscopically. The satisfactory results led to the development of a stapling instrument that could be passed through a cannula at laparoscopy and used to close the abdominal hernial opening. The clinical trial of treating hernias by laparoscopy was originally directed to the management of indirect inguinal hernias, but its use has since been expanded to include treatment of direct, femoral, obturator, incarcerated, recurrent, and bilateral hernias. The laparoscopic anatomy of the inguinal hernia, different from that seen by an inguinal approach, is briefly reviewed. The details of the operative technique are presented, as are the bases of other laparoscopic techniques that have evolved. Thirty-one hernial orifices have been closed and followed over 18 months. The results appear to be satisfactory in 27 instances. There were early technical failures in 2: One patient developed a recurrence after 5 months, later shown to be due to a sliding hernia; and symptoms of meralgia paresthetica of indeterminate origin appeared in one case. The advantages over the traditional approach are described; the disadvantages of the laparoscopic approach are those of laparoscopy itself and the absence of a long-term follow-up.

Adolescent↗
PubMedDate not supplied

Propafenone-theophylline interaction.

A 63-year-old man with ventricular tachycardia (VT) refractory to drug therapy was admitted for surgical ablation of the VT with coronary artery bypass graft surgery. He developed increased theophylline concentrations with decreased calculated theophylline clearance after propafenone therapy for recurrent VT was initiated. Within 1 day after the addition of propafenone 150 mg every 8 hours to a drug regimen that included theophylline sustained-release tablets 300 mg every 12 hours, the patient demonstrated increased theophylline serum concentrations and decreased calculated theophylline clearance. Despite a decrease in theophylline dosage, theophylline concentrations continued to rise as the dosage of propafenone was increased to 300 mg every 8 hours. Theophylline was discontinued due to a rising theophylline level, improved oxygenation, and absence of wheezing. Both propafenone and theophylline are hepatically metabolized by the cytochrome P-450 enzyme system. The decrease in theophylline clearance of 25% to 69% in this patient may be due to competitive metabolism resulting in enzyme inhibition and increased theophylline concentrations. Since propafenone and 5-OH-propafenone levels were not measured, it is unknown whether propafenone clearance was affected as well. Health care practitioners should be aware of this possible drug interaction and monitor theophylline concentrations and the electrocardiogram closely if the agents are coadministered.

Coronary Artery Bypass↗