Effects of fatty acids on hepatic gene expression

Polyunsaturated fatty acids (PUFA) have dramatic effects on hepatic lipid metabolism by regulating the transcription of specific genes encoding enzymes involved in glycolysis and lipogenesis. The S14 gene, a putative lipogenic protein, has been used as a model to define the molecular basis of PUFA action on hepatic gene expression. We have shown that PUFA-regulated hepatic transcription factors target cis-regulatory elements located between -220 and -80 bp upstream from the 5' end of the S14 gene. Peroxisomal proliferators (PP) also have dramatic effects on hepatic lipid metabolism through effects on gene expression. The mechanism of PP action is mediated, at least in part, through nuclear receptors, i.e. PP activated receptor (PPAR). We found that the potent PP, i.e. WY14,643, suppressed mRNAS14 and the activity of an S14CAT fusion gene in cultured primary hepatocytes. Preliminary mapping studies showed that WY14,643 cis-regulatory elements were located either within the S14 proximal promoter (-290 and +19), the S14 TRE (-2900 to -2500) or both regions. Gel shift analysis showed that PPAR did not bind S14 promoter elements. These studies suggest that PUFA- and PP-regulated factors may share common cis-acting elements within the S14 promoter. However, if PUFA control of S14 gene transcription is mediated by PPAR, this mechanism does not involve direct interaction of PPAR with the S14 proximal promoter.

Severe peripheral ischemia after vasospasm may be prevented by spinal cord stimulation. A preliminary report of a study in a free-flap animal model

Electric spinal cord stimulation (SCS) is at present used in many centers to treat ischemic pain and ischemia in peripheral vascular disease. The most promising results have been obtained in cases where a vasospastic component is dominating. The knowledge concerning the mechanisms behind these effects has been scanty, but recent experimental studies indicate that suppression of sympathetic activity and the release of vasoactive substances may be important. A problem with many of the animals studies aimed at exploring these mechanisms is that they have almost exclusively been performed on normal animals without ischemia. However, in studies of the responsiveness of local ischemia to various pharmacological substances and to electrical transcutaneous nerve stimulation, animal models with ischemic skin flaps have been used. We applied SCS via chronically implanted electrodes in a model of local vasospasm in the rat, induced by mechanical stimulation of the vessel supplying an island flap in the groin. Male Sprague-Dawley rats were used. First, a monopolar system for spinal cord stimulation, with the intraspinal cathode at vertebral level T11, was implanted in halothane anaesthesia. After about three days of recovery the rats were anaesthetized with chloral hydrate ip and a groin neurovascular flap based on the epigastric vessels was raised. Microcirculation in the flap as well as in a control area in the contralateral groin was monitored by laser Doppler technique. Vasospasm was induced by gently pinching the superficial epigastric artery with microforceps. Two groups of animals were submitted to two spasm periods, one with SCS applied for 20 min. by 50 Hz; 0.2 msec and with 2/3 of the intensity required for a motor response before the first period. The second group, receiving sham SCS, served as a control. Both degree of ischemia after spasm provocation and the time to recovery were evaluated. In general SCS affected basal flow very little. In the control group the rats demonstrated increasing vasospastic reactions with subsequent flap ischemia to the two mechanical provocations. In the experimental group a response pattern emerged indicating that pre-spasm SCS could both reduce the spasm amplitude and significantly shorten the time for restoration of a satisfactory microcirculation in the flap. Some few trials with pharmacologically induced spasm by topical application of noradrenaline onto the feeding vessel also followed the same pattern. In conclusion, SCS seems to be able to reduce vasospasm, especially if the treatment is given before the ischemic period. This approach may supply an animal model for further studies of possible mechanisms behind the microcirculatory effects of SCS.

Receptive field properties of cat retinal ganglion cells during short-term IOP elevation

PURPOSE

To examine and compare receptive field properties of cat retinal ganglion cells before and during intraocular pressure (IOP) elevation.

METHODS

Responses of cat retinal ganglion cells to two sets of specially designed light or dark spots and annuli were recorded extracellularly. Receptive field properties were studied comparatively before and during short-term constant IOP elevation induced by keeping the retinal perfusion pressure at a critical level of about 30 mm Hg.

RESULTS

All the responses, including properties of different types of receptive fields and different components of the cells' receptive fields, decreased during short-term IOP elevation. The responses of off-center cells were more tolerant of IOP elevation than those of on-center cells, whereas the responses of Y cells were less sensitive to IOP elevation than those of X cells. The responses of the centers of the receptive fields exhibited pronounced resistance to IOP elevation than those of the surround. The peak responses of the post-stimulus time histogram of all cells declined less than the mean responses during IOP elevation.

CONCLUSIONS

The varied effects of short-term IOP elevation on different types (X and Y, on-center and off-center) of retinal ganglion cells and their receptive field properties may reflect the different degrees of ischemic effects on the retinal pathways that project to the different types of ganglion cells.

An experimental animal model of spinal cord stimulation for pain

In spite of the routine usage of spinal cord stimulation (SCS) as treatment of chronic pain, there is an insufficient understanding of the mechanisms underlying its effect. The method was originally developed as a spin-off from experiments demonstrating the inhibitory control of nociceptive signals by the activation of large afferent fibers, and on the basis of these findings the gate-control theory was advanced. Later experiments showed that stimulation of the dorsal columns can inhibit the relay of nociceptive impulses to second-order neurons in the dorsal horn. It should be emphasized that all these experiments were performed with acute noxious stimuli; it is now universally recognized that SCS in patients is preferentially, or exclusively, effective for chronic neuropathic types of pain. For these and other reasons the mode of action of SCS in clinical pain cannot be inferred from these early animal experiments. In ongoing studies we have used animal models of mononeuropathy (rat) in which we have applied SCS acutely or chronically with stimulation parameters similar to those used in patients. In these animals the first component of the flexor reflex appears with a lower stimulus threshold in the nerve lesioned than in the intact, sham-operated leg. SCS was applied at the approximate level of Th-XII during 10-20 min and produced a marked augmentation of the stimulus threshold. This abnormally high threshold was not normalized until 30-60 min after the end of SCS. In awake animals SCS was applied via an implanted spinal electrode and the effect on behavior changes associated with mononeuropathy was studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies on long-acting insulin: crystal structure of Arg-B31 human insulin at 2.0A resolution

The crystal structure of Arg-B31 human insulin (ABHI), a long-acting insulin derivative, has been determined at 2.0 A resolution by using X-ray diffraction analysis. The final crystallographic R factor of the structure model after the refinement is 0.189 with the bond length r. m. s deviation of 0.018 A. The refined structure of ABHI showed that the conformation of B-chain C-terminal residues was more stable than that in the native molecule. A striking structural feature of ABHI was an additional ion pair formed between Arg-B31 of molecule I and Glu-B21 of molecule II in a dimer, and three ionic bonds between the neighbouring molecules thereby appeared on the surface of ABHI hexamer. These secondary bonds generated by the insertion of the residue Arg-B31 should make the rate of dissociation of ABHI hexamer slow down when it was injected into the body and the property of protraction should be produced by a 'depot effect'. This ought to be the main structure basis of the prolonged action of ABHI. The results observed here demonstrate that the main idea we used in search for long-acting insulin is reasonable and correct which goes like this: making some additional non-covalent bonds between insulin monomers so as to slow down the dissociation of insulin oligomers and gain the protraction from a 'depot effect', which may be used as a principle in the further research. It also shows an impressive example that the experimental result reported here is in agreement with the theoretical prediction before the structural determination.

Effects of atrial natriuretic factor on patients with renovascular hypertension

Previous studies have shown the effects of atrial natriuretic factor (ANF) on rats with renovascular hypertension (RVH). In the present study low dose alpha-hANF (0.025 microgram/kg/min) was administered intravenously for 60 minutes to seven RVH patients. Results demonstrated an inhibition of renin-angiotensin-aldosterone system (RAAS), reduction of plasma catecholamine and arginine vasopressin(AVP), diuresis and natriuresis, increase of hematocrit and creatinine clearance, and slight decrease of blood pressure. These results showed that most factors involved in the establishment and maintenance of RVH are affected by ANF infusion.

[Transplantation of fetal adrenal medullary to the brain in Parkinson's disease]

The adrenal medullary tissue removed from the fetus donor aborted at the age of 24 weeks was cultured for one week. Approximately 200-300 mg tissue was placed at the head of bilateral caudate in 17 severe patients with PD. Follow-up lasted for 3 to 18 months. Improvement was observed in all patients 3 months after grafting. Clinical analysis showed that the efficacy was significant and that one of the 17 patients relapsed. The response rate of 6 to 12 months was 87.5%. Immediately after operation, the drug was withheld or decreased in dosage. The low density areas in the head of caudate nucleus was found by CT within 1 to 10 days, and disappeared one month after operation. We conclude that the human fetal adrenal medullary tissue can survive in the human brain and is associated with functional effect. Transplantation of the brain tissue is useful in the treatment of PD.