Pharmacological and behavioral components of tolerance to LSD and mescaline in rats

A fixed-ratio schedule of water reinforcement (FR-10) was used to examine the relative contributions of pharmacological and behavioral mechanisms in the development of tolerance to the disruptive effects of LSD and mescaline in the rat. Rats treated daily with LSD or mescaline before operant testing developed tolerance to the impairement of responding, while rats treated daily after each session did not display tolerance when the drugs were administered before testing. These results indicate that behavioral compensatory mechanisms may be involved in the development of tolerance to the disruptive effects of LSD and mescaline on fixed-ratio (FR-10) performance.     

Regional hip blockade. A simplified technique for the relief of intractable osteoarthritic pain

A regional anaesthetic technique is described using a blind anatomical approach to the obturator nerve and nerve to quadratus femoris, as a means of alleviating the disabling pain of chronic osteoarthritis of the hip, when arthroplasty is not available.     

Sperm morphology as diagnosed by strict criteria: probing the impact of teratozoospermia on fertilization rate and pregnancy outcome in a large in vitro fertilization population

OBJECTIVE: To investigate the predictive value of sperm morphology assessed by strict criteria on IVF outcome. DESIGN: Retrospective analysis of all IVF cycles (January 1987 to December 1992). MAIN OUTCOME MEASURES: All patients were assigned to one of three groups based on sperm morphology: P-pattern (< 4% normal forms), G-pattern (4% to 14% normal forms), and N-pattern (> 14% normal forms). Morphology pattern was related to other semen characteristics and IVF outcome. RESULTS: Despite corrective measures at oocyte insemination, the fertilization rate was significantly different among the three morphology groups, P < G < N. N-pattern sperm produced a mean fertilization rate over 85% regardless of low motility or concentration. In a cohort study, P-pattern cycles produced a lower implantation rate and lower ongoing pregnancy rate, independent of the lower fertilization rate. CONCLUSIONS: Strict morphology is an excellent biomarker of sperm fertilizing capacity, independent of motility and concentration. P-pattern sperm may denote a poorer prognosis for establishing a pregnancy, even after a satisfactory fertilization rate is achieved.     

Recurrent abdominal pain during childhood

RAP offers a complex and often confusing array of symptoms and diagnostic possibilities. This may be due to its unique age of presentation, its inherent somatic and cognitive developmental issues, or the physiology of abdominal pain itself. A careful examination of the historic and physical findings should produce a therapeutic plan that addresses somatic, psychological, and environmental aspects of the child. This process will avoid overly simplistic and premature misdiagnosis or potentially unnecessary investigations that convey a sense of disinterest, haste, and disbelief in the problem. The successful management of RAP lies in the recognition that serious underlying disease frequently is not present and that time usually is on our side. It is the process of continued and thoughtful evaluation and reassurance over time that counts.     

On the feasibility of using an atmospheric discharge plasma as an RF antenna

The plasma produced by a laser-guided, electric discharge in the atmosphere has been formed in the shape of a folded monopole antenna with a characteristic frequency of 112 MHz. This plasma antenna has been used to transmit and receive signals at 112 MHz. While the plasma remained conducting, the signal transmitted from, and received on, the plasma antenna was within -1pm1dB of that transmitted from and received on a "standard" copper folded monopole antenna of the same size. During this time the signal transmitted from, and received on, the plasma antenna also remained approximately constant in amplitude (fluctuationssim pm1dB). This useful lifetime of the plasma antenna was varied fromsim 200 mus togeq 2000 mus by changing the dration of the electric discharge sustaining the plasma columns. In these experiments, the noise from the plasma antenna was not distinguishable from that developed using a copper antenna, but in both cases the noise was much larger than the true thermal noise background.     

Endothelium and high blood pressure

Due to its strategic anatomical position, the endothelium is constantly exposed to the different risk factors for atherosclerosis. During the last decade it has become clear that hypertension profoundly affects endothelial function. Depending on the form of hypertension, endothelium-dependent relaxation is impaired in most vascular beds. In spontaneous hypertension, the production of nitric oxide, which in endothelial cells is formed from L-arginine via the constitutively expressed enzyme endothelial nitric oxide synthase, represents the main mediator of endothelium-dependent vasodilation and seems to be enhanced. On the other hand, the release of endothelium-dependent contracting factors such as prostaglandin H2 and thromboxane A2 have been demonstrated in this model of hypertension. Similar results have been obtained in the forearm circulation of patients with essential hypertension. In contrast, in models of salt-sensitive hypertension no release of vasoconstrictor prostanoids can be found indicating a decreased production of nitric oxide. Thus, in spontaneous hypertension an increased production of nitric oxide seems to occur, which is ineffective due to either the simultaneous release of endothelium-dependent vasoconstrictors and/or inactivation of nitric oxide, or due to anatomical changes such as hypertension-induced intimal thickness which inhibits its action on vascular smooth muscle cells. In summary, in hypertension, endothelium-dependent vasodilation is blunted and the endothelial L-arginine nitric oxide pathway is altered. These changes seem to represent a consequence rather than a cause of hypertension.