Dynamic pressure–flow relationship of the cerebral circulation during acute increase in arterial pressure

The physiological mechanism(s) for the regulation of the dynamic pressure–flow relationship of the cerebral circulation are not well understood. We studied the effects of acute cerebral vasoconstriction on the transfer function between spontaneous changes in blood pressure (BP) and cerebral blood flow velocity (CBFV) in 13 healthy subjects (30 ± 7 years). CBFV was measured in the middle cerebral artery using transcranial Doppler. BP was increased stepwise with phenylephrine infusion at 0.5, 1.0 and 2.0 μg kg^–1 min^–1. Phenylephrine increased BP by 11, 23 and 37% from baseline, while CBFV increased (11%) only with the highest increase in BP. Cerebrovascular resistance index (BP/CBFV) increased progressively by 6, 17 and 23%, demonstrating effective steady-state autoregulation. Transfer function gain at the low frequencies (LF, 0.07–0.20 Hz) was reduced by 15, 14 and 14%, while the phase was reduced by 10, 17 and 31%. A similar trend of changes was observed at the high frequencies (HF, 0.20–0.35 Hz), but gain and phase remained unchanged at the very low frequencies (VLF, 0.02–0.07 Hz). Windkessel model simulation suggests that increases in steady-state cerebrovascular resistance and/or decreases in vascular compliance during cerebral vasoconstriction contribute to the changes in gain and phase. These findings suggest that changes in steady-state cerebrovascular resistance and/or vascular compliance modulate the dynamic pressure–flow relationship at the low and high frequencies, while dynamic autoregulation is likely to be dominant at the very low frequencies. Thus, oscillations in CBFV are modulated not only by dynamic autoregulation, but also by changes in steady-state cerebrovascular resistance and/or vascular compliance.     

Vertical transmission of hepatitis. 3 years' follow-up

An infant with an acute hepatitis B infection developed the chronic aggressive form of the disease. The immunoserologic findings in the child and his mother suggest a vertical hepatitis B virus transmission. The mother was found to be an asymptomatic HBs-Ag carrier but HBe-Ag negative. The importance of a screening program for HBs-Ag in pregnant women is discussed. It is suggested that newborns at risk should get passive-active immunisation post partum as early as possible.     

Mitochondrial myopathy with lactic acidosis and deficient activity of muscle succinate cytochrome-c-oxidoreductase

A male infant had severe muscular hypotonia from birth. Recurrent vomiting with dehydration and severe metabolic acidosis complicated the course. Elevated lactate (up to 12.3 mmol/l; n<2), pyruvate (0.4 mmol/l; n<0.05) and alanine levels were found in serum with an abnormal lactate/pyruvate ratio (>30; n<15). In urine the concentrations of lactate, pyruvate, alanine and of several intermediates of the citric acid cycle were increased. In muscle, numerous disseminated ragged red fibres were found by light microscopy; muscle fibres were found to contain subsarcolemmal aggregates of mitochondria, lipid droplets and glycogen by electromicroscopical methods. More-over, mitochondria with a typical circular arrangement of cristae were noticed.In liver homogenates normal activities of pyruvate carboxylase and pyruvate dehydrogenase complex were found; in liver mitochondria also succinate-cytochrome-c-oxidoreductase activity was normal. However, in muscle no succinate-cytochrome-c-oxidoreductase activity was detectable.The patient became increasingly lethargic and died because of sepsis at 5 months of age.     

Parotid gland tumours: a 15-year experience.

Between 1973 and 1988, 302 patients underwent surgical operations for parotid gland swelling. Primary operations were performed in 293 cases, while secondary operations for recurrent tumour were performed in nine cases. A total of 244 patients (80.8%) were found histologically to have either a benign parotid tumour or a tumour-like lesion, while 58 patients (19.2%) were diagnosed as having malignant tumours. Two hundred and eighty-nine patients underwent superficial and total conservative parotidectomy and in 13 cases a radical parotidectomy was performed. The median follow-up was 5 years (range 1-15 years). Permanent facial nerve palsy, tumour recurrence, Frey's syndrome and parotid fistula were recorded as 0.7, 0.7, 2.1 and 0.4%, respectively. Thus, with full understanding of the surgical anatomy of the parotid gland and correct tumour identification, preservation of the facial nerve and serious postoperative complications can be minimized following superficial and/or total conservative parotidectomy.     

Renal transport of aromatic acids in patients with phenylketonuria

Renal clearance of phenylpyruvic acid is maximal at a plasma concentration of 40–60 µmol/l. This concentration is obtained with plasma phenylalanine concentrations of 1.0–1.2mmol/l, the threshold for separating classical phenylketonuria from phenylketonuria variants.     

The thermal origin of spontaneous activity in the Limulus photoreceptor

1. Discrete depolarizations of the photoreceptor cell membrane called discrete waves occur spontaneously and in response to illumination in the eye of the horseshoe crab, Limulus. Each light induced discrete wave is caused by the absorption of a single photon.2. The frequencies of spontaneous and light induced discrete waves were studied at different temperatures from 0 to 25 degrees C using a new method of counting them to avoid errors due to their temporal overlap.3. The frequency of spontaneous discrete waves followed the Arrhenius relationship with activation energy equal to 48.6 kcal.4. The frequency of the discrete waves caused by a fixed level of steady illumination was not significantly changed when the temperature of the cell was changed.5. The relationship of the frequency of spontaneous discrete waves to temperature was compared to a prediction based on the relationship of the quantum relative spectral sensitivity of the Limulus eye to the temperature of the eye. The prediction was in good agreement with observation and suggests that spontaneous discrete waves result from thermally induced cis to trans isomerizations of visual pigment molecules.     

Orbital radiotherapy for thyroid-related orbitopathy

PURPOSE OF REVIEW: Orbital radiotherapy has been one of the primary treatment modalities for moderate to severe thyroid-related orbitopathy. In this review the authors discuss the role of orbital radiotherapy in this disease with particular emphasis on questions raised by recent studies. RECENT FINDINGS: Despite its widespread use, until recently there have been few well-designed, randomized clinical trials on the role of orbital radiotherapy for thyroid-related orbitopathy. Although most the literature points to a favorable effect of orbital radiotherapy, recent studies have provided us with conflicting results. SUMMARY: Orbital radiotherapy remains a safe and a widely used treatment option for severe and progressive thyroid-related orbitopathy. More randomized clinical trials are needed, especially to examine the role of orbital radiotherapy for severe thyroid-related orbitopathy characterized by severe congestion and/or compressive optic neuropathy with and without the use of corticosteroids. There is a wide consensus among clinicians that this subgroup of patients is the most frequent one to which orbital radiotherapy is offered.     

l-Proline catalyzed one-pot synthesis of polysubstituted pyridine system incorporating benzothiazole moiety via sustainable sonochemical approach

The efficient, highly convenient synthesis of polysubstituted pyridine derivatives was established via the reaction of N-(benzothiazol-2-yl)-2-cyanoacetamides with an assortment of arylidene malononitriles and arylidene ethyl cyanoacetates in the presence of l-proline as an efficient organocatalyst for this type of ultrasonic-mediated Michael addition. The mechanistic pathway and factors affecting this reaction were also established. The main characteristics of this procedure are high yields, use of a cost-effective catalyst, and easy work-up and purification.

The l-proline catalyzed ultrasonic-mediated synthesis of polysubstituted pyridone derivatives through the reaction of N-(benzothiazol-2-yl)-2-cyanoacetamides with an assortment of arylidenes has demonstrated as an efficient protocol.     

Thyrotropin-releasing hormone has profound presynaptic action on cultured spinal cord neurons

Thyrotropin-releasing hormone (TRH) receptors are widely distributed throughout the nervous system. In particular, both the dorsal and the ventral horn (VH) neurons contain a rich distribution of TRH receptors, and TRH application to these sites has profound physiological effects. Currently the mechanism of action of TRH is not known. We examined the effect of TRH on ventral horn neurons using intracellular and patch-clamp techniques. Our results indicate that TRH application profoundly increases the firing rate of VH cells by decreasing membrane conductance. More importantly, TRH causes a significant increase in frequency and amplitude of postsynaptic potentials. Under voltage-clamp condition, TRH reduces holding current and causes a significant increase in the rate of occurrence and the amplitude of excitatory postsynaptic currents (EPSCs), an effect that lasts for more than 5 minutes. This effect of TRH is not observed in cultured neurons pretreated with tetanus toxin. TRH also fails to alter the characteristics of the EPSCs when it is applied to a region of the cell that is sparsely innervated. These results provide strong evidence that presynaptic mechanisms have a significant role in the excitatory effect of TRH on the VH neurons. Because there is evidence that trophic factors are released from presynaptic terminals, by increasing synaptic activity, TRH can have a trophic influence on the spinal cord neurons. In addition, because there are a significant number of TRH containing neurons within the spinal cord, it is likely that TRH has a major role in information processing within the spinal cord.