Expression of the Volvox gene encoding nitrate reductase: mutation-dependent activation of cryptic splice sites and intron-enhanced gene expression from a cDNA.

Use of the nitrate reductase encoding gene (nitA) as selection marker has facilitated the successful nuclear transformation of Volvox carteri. The Volvox nitA gene contains 10 introns. A stable nitA mutation in the Volvox recipient strain 153-81 resides in a G-to-A transition of the first nucleotide in the 5' splice site of nitA intron 2. This mutation resulted in at least three non-functional splice variants, namely: (1) intron 2 was not spliced at all; (2) a cryptic 5' splice site 60 nt upstream or (3) a cryptic 5' splice site 16 nt downstream of the mutation were activated and used for splicing. When we used nitA cDNA (pVcNR13) for transformation of V. carteri 153-81, a low efficiency of about 5 x 10(-5) transformants per reproductive cell was observed. Re-integration of either intron 1 (pVcNR15) or introns 9 and 10 (pVcNR16) in the transforming cDNA increased transformation rates to 5 x 10(-4). In parallel, pVcNR15-transformed Volvox exhibited growth rates that were 100-fold increased over the pVcNR13-transformed alga. This intron-enhancement of nitA gene expression appears to be associated with post-transcriptional processing and 'channelling' of the message. These data suggest an important role of splicing for gene expression in V. carteri.

Carpal tunnel syndrome: surgical and nonsurgical treatment.

A retrospective study was performed to evaluate treatment for carpal tunnel syndrome. Two hundred sixty-five patients were treated over a 4 1/2-year period. Only patients in whom studies showed abnormal nerve conduction (a median nerve sensory latency greater than 3.6 msec or a median distal motor latency greater than 4.3 msec) were included in the evaluation. Nonsurgical treatment consisted of patient education, wrist splinting, B vitamins, nonsteroidal anti-inflammatory medication, steroid injections, and job change or modification when possible. A follow-up history, physical examination, and repeat nerve conduction studies were performed at 3- to 9-month intervals, depending on the severity of symptoms and the degree of abnormal latencies. Surgery was performed on 77 patients and 95 hands. The remaining 188 patients were treated nonsurgically. Both surgically and nonsurgically treated patients considered the results to be satisfactory.

Neurological evaluation of occupational hand pain.

The evaluation of the patient with pain, weakness, or numbness of the hand or upper extremity begins with knowledge of neuroanatomy and of the proper examination techniques. Neurological diseases of the peripheral nerves or central nervous system often present with vague complaints or minimal findings on clinical examination that may be diagnosed only with a combination of radiologic and neurodiagnostic studies. However, tests alone cannot determine the best treatment as each case must be individualized. An understanding of the utility and limitations of the electromyogram and nerve conduction studies is important when treating these patients.

Acute regulation of lymphocyte beta-adrenoceptor activity in pheochromocytoma.

The effect of an acute endogeneous catecholamine stimulation on the regulation of lymphocyte beta-adrenoceptor activity was studied in a patient with pheochromocytoma. Baseline blood pressure, heart rate, adrenoceptor density, and plasma concentrations of epinephrine, norepinephrine, and cyclic adenosine monophosphate were normal. Excessive spontaneous increases of catecholamine concentrations were accompanied by a rise in blood pressure, bradycardia, and an acute up-regulation of beta-adrenoceptors. Plasma concentrations of cyclic adenosine monophosphate paralleled the increase in receptor density and blood pressure. After normalization of catecholamine plasma levels, blood pressure, and beta-adrenoceptor density returned to baseline values. This observation adds support to the theory that an acute catecholamine stimulation leads to an acute sensitization of the beta-adrenoceptor-adenylatecyclase-cyclic-adenosine-monophosphate system leading to blood pressure elevation.

Adrenergic hyposensitivity during long-term diuretic therapy--a possible explanation for the antihypertensive effect of diuretics?

The long-term effect of hydrochlorothiazide on beta 2-adrenoceptor density on mononuclear cells was investigated in 10 male patients with essential hypertension. There was a 40% reduction in beta 2-adrenoceptor density but no change in receptor affinity. This down-regulation of beta 2-adrenoceptors may explain the observed adrenergic hyposensitivity after long-term diuretic therapy. If lymphocytic beta 2-adrenoceptors represent presynaptic beta-adrenoceptors, a down-regulation of presynaptic beta 2-receptors may occur too, and result in a decrease of adrenergic transmitter release. Under this assumption long-term diuretic treatment causes its antihypertensive effect by modulating adrenergic sensitivity at the receptor level on the presynaptic side leading to an attenuated response to pressor hormones on the postsynaptic vascular side.

Beta 2-adrenoceptor density on membranes and on intact mononuclear cells in essential hypertension.

Alterations in the status or in the regulation of adrenoceptors may contribute to essential hypertension. This could be studied using the recently introduced radio-ligand binding techniques to characterize the adrenoceptors on human peripheral blood cells. The present study shows that patients with essential hypertension have a twofold increase of beta 2-adrenoceptor density on intact mononuclear cells as compared to normotensive controls: 859 +/- 260 (n = 10) vs. 420 +/- 119 (n = 10) maximal binding sites for (+/-) 125-Iodocyanopindolol expressed as molecules per cell (P less than 0.001). Furthermore, there is a highly significant correlation (r = 0.86) between the calculated mean arterial blood pressure and the beta 2-adrenoceptor density over a wide range of normal and increased blood pressure. These findings could only be demonstrated with intact mononuclear cells but not with membrane fractions. No difference was found in receptor affinity between patients with essential hypertension and normotensive controls. Thus, essential hypertension is combined with a higher beta 2-adrenoceptor density on intact mononuclear cells which might represent, for example, an increased density of prejunctional beta 2-adrenoceptors. Mean arterial blood pressure is positively correlated with beta 2-adrenoceptor density over a wide range of blood pressure in normotensives and hypertensives. The expression of beta 2-binding sites on the cell surface is possibly altered in essential hypertension resulting in a disparity between intracellular and extracellular binding sites as compared with normotensives.

[Direct determination of phenylalanine in serum by derivative spectrophotometry (author's transl)]. / Direkte Bestimmung von Phenylalanin in Serum mittels Derivativspektrophotometrie.

A simple and precise method is described for the determination of phenylalanine in serum or plasma, using derivative spectrophotometry. After the removal of protein and uric acid, 100 microliters serum or plasma are analysed directly for phenylalanine. The magnitude of the difference between the peak minimum at 254 nm and the peak maximum at 257 nm of the derivative spectrum (2nd derivative of the absorption spectrum) is directly proportional to the phenylalanine content. The precision was 2.1-10.3%, depending on the concentration of phenylalanine. Recovery was between 97.1 and 101.1%. Sensitivity was 5 mg/l serum. The method was compared with a column chromatographic determination of phenylalanine.