Leg weakness in neurosarcoidosis.

A 22-year-old man had leg weakness and decreased hearing. A diagnosis of neurosarcoidosis was made, based on neuroimaging studies and lymph node biopsy. Post-treatment neuroimaging, in particular magnetic resonance imaging along with clinical course, is useful in monitoring response to therapy.

Guillain-Barré syndrome and cytomegalovirus infection during pregnancy.

We report a case of Guillain-Barré syndrome and associated cytomegalovirus infection during pregnancy. A 15-year-old black adolescent had progressive ascending paralysis and vague sensory symptoms during week 10 of her first pregnancy. Diagnosis of Guillain-Barré syndrome was confirmed by electrophysiologic findings consistent with acute demyelinating polyradiculoneuropathy. A mild elevation of anti-GM1 antibodies was also detected. The patient improved with plasmapheresis treatment; however, fetal death occurred 10 weeks later. Cytomegalovirus placentitis was confirmed histologically. Acute demyelinating polyneuropathy during pregnancy warrants consideration of a concomitant, primary maternal and fetal cytomegalovirus infection.

Low back syndromes. The challenge of accurate diagnosis and management.

The causes of low back pain range from ruptured lumbar disks and spinal stenosis to compression fractures and osteoarthritis. Although surgery may be indicated in some cases, conservative measures are often effective, and preventive regimens may be successful in patients who are obese or otherwise physically unfit. In patients who have been injured on the job or in an automobile accident, the question of compensation may hinder treatment. Hysterical patients may need psychiatric referral.

The roles of nitrate and ammonium in the regulation of the development of nitrate reductase in Chlamydomonas reinhardii.

The regulation of the development of nitrate reductase (NR) activity in Chlamydomonas reinhardii has been compared in a wild-type strain and in a mutant (nit-A) which possesses a modified nitrate reductase enzyme that is non-functional in vivo. The modified enzyme cannot use NAD(P)H as an electron donor for nitrate reduction and it differs from wild-type enzyme in that NR activity is not inactivated in vitro by incubation with NAD(P)H and small quantities of cyanide; it is inactivated when reduced benzyl viologen or flavin mononucleotide is present. After short periods of nitrogen starvation mutant organisms contain much higher levels of terminal-NR activity than do similarly treated wild-type ones. Despite the inability of the mutant to utilize nitrate, no nitrate or nitrite was found in nitrogen-starved cultures; it is therefore concluded that the appearance of NR activity is not a consequence of nitrification. After prolonged nitrogen starvation (22 h) the NR level in the mutant is low. It increases rapidly if nitrate is then added and this increase in activity does not occur in the presence of ammonium, tungstate or cycloheximide. Disappearance of preformed NR activity is stimulated by addition of tungstate and even more by addition of ammonium. The results are interpreted as evidence for a continuous turnover of NR in cells of the mutant with ammonium both stimulating NR breakdown and stopping NR synthesis. Nitrate protects the enzyme from breakdown. Reversible inactivation of NR activity is thought to play an insignificant rôle in the mutant.

Pyridine nucleotide specificity and other properties of purified nitrate reductase from Chlorella variegata.

Nitrate reductase (NR) (EC 1.6.6.2) from Chlorella variegata 211/10d has been purified by blue sepharose affinity chromatography. The enzyme can utilise NADH or NADPH for nitrate reduction with apparent K m values of 11.5 µM and 14.5 µM, respectively. Apparent K m values for nitrate are 0.13 mM (NADH-NR) and 0.14 mM (NADPH-NR). The diaphorase activity of the enzyme is inhibited strongly by parachloromercuribenzoic acid; NADH or NADPH protects the enzyme against this inhibition. NR proper activity of the enzyme is partially inactive after extraction and may be activated after the addition of ferricyanide. The addition of NAD(P)H and cyanide causes a reversible inactivation of the NR proper activity although preincubation with either NADH or NADH and ADP has no significant effect.