The decerebrate human: associative learning

Phasic changes in cardiac reactivity to innocuous stimuli, presented in a sensory disparity paradigm, were used to evaluate habituation and learning processes in five decerebrate subjects. Three subjects showed systematic changes over trials in the pattern of cardiac response to simple auditory or visual stimuli, indicative of habituation. In addition, tests for associative learning were given after repeated presentations of two paired stimuli. The appearance of a marked cardiac orienting response, to the unpredictable omission of the second stimulus, documented the development of a conditioned association in these same three subjects. One additional subject failed to show a consistent pattern of response to the stimuli, and another demonstrated a consistent response which was not subject to habituation. Overall, these findings support the view that learning processes are not solely the product of the cerebral hemispheres, but reflect general integrative features of the human neuraxis.     

Topical corticosteroid therapy complicating congenital glaucoma

A 4-month-old infant with congenital glaucoma had been treated with a topical antibiotic-corticosteroid for three months. This fact complicated initial management, delaying definitive diagnosis and therapy. Topical steroid therapy in infants can produce a condition simulating congenital glaucoma. Since there is little rationale for using topical steroids to treat most infantile external disease processes, they are best avoided. When steroids are used for a prolonged period, some strategy for detecting glaucoma should be adopted.     

Flavonol glycosides and flavonol glucoside gallates from Peltophorum africanum

In this study of interactions occurring within the heart, isolated superfused strips of rabbit atria, containing the sinoatrial (s.a.) node, were subjected to sinusoidal subthreshold current pulses of varied frequencies and intensities. A.C. current from an R.C. oscillator was applied through a Grass stimulation isolation unit, push-pull connection, and non-polarizing (Ag-AgCl-KCl-Tyrode Agar-Agar) electrodes. A Grass polygraph and tachometer were used to record the applied pulses and nodal firing rates; simultaneous magnetic tape recordings were obtained and used for data analysis. Suction electrode recordings and oscilloscope displays were used to determine how the cyclic impulses affected cellular activity. The s.a. nodal rhythm was modified by subthreshold A.C. current applications; when frequencies were low, firing rates of the node were modulated by the A.C. and mean rates were reduced. As frequencies were progressively increased, slow waxings and wanings in heart rate were produced. These periodic fluctuations were not readily correlated with either the A.C. frequency nor the intrinsic nodal rate, but were representative of the difference between the two. As applied current frequency neared the pacemaker's intrinsic rate, a synchronization occurred and the discharges locked in at a specific phase of the applied current alternation. This synchronization maintained during slight further increases in A.C. frequency but above a critical rate this relationship broke down and the waxing and wanings in frequency of pacemaker rate again developed. It was concluded that pacemaker action of the s.a. node is effected by integration of cellular activity through electron coupling.     

建立精密的直流浮动电流源

尽管有源滤波器的理论家和设计者都对GIC（通用阻抗变换器）非常熟悉，但一般模拟人员对它并不了解。一个单端口有源电路一般包括低成本运放、电阻和电容，GIC将容抗转换为感抗，因而可以替代滤波器中以RLC传输函数描述的电感。另外，GIC输入阻抗方程的灵活性允许进行虚拟阻抗的设计，这在实际元器件中是不存在的，例如依赖频率的电阻。GIC是30年前推出的，已广泛应用于交流电路和有源滤波电路。     

Nails and claws in primate evolution

The issue of whether nails or claws were present on the digits of the last common ancestor of living primates is central to the understanding of the ecological context in which the order originated. Two lines of evidence are available, the shape (claw, nail, toilet-claw) and the histological structure (one or two horny strata). Here we review the existing data regarding the shape and histological structure of cheirideal appendages in primates and present new information from a wide range of living primates. We demonstrate the presence of a typical toilet-claw in Daubentonia madagascariensis and discuss its consequences, since the alleged lack of such structures in this species has long obscured the issue. The general view that primate nails, with the exception of those in New World primates, consist of only one layer is disproved by the presence of two distinct strata in the nails of the feet of three out of seven catarrhine species examined, as well as in Lemur catta. The combined new and old data indicate that the last common ancestor of the extant primates had lost the typical mammalian claws of its ancestors and developed nails on all pedal digits except digit II, which bore a toilet-claw. All nails as well as the toilet-claw originally consisted of two layers. We present a new hypothesis regarding the adaptational significance of these changes.     

The changing nature of office work: effects on repetitive strain injuries

This historical perspective underscores that there is rarely a simple connection between the demands of a particular technology and the risk of occupational disease.     

Application of dried blood spot specimens for serologic subtyping of human immunodeficiency virus type 1 in Thailand

Dried blood spot (DBS) specimens were assessed as an alternative to plasma for human immunodeficiency virus type 1 (HIV-1) serotyping by V3 loop peptide enzyme immunoassay. Nested PCR capable of distinguishing HIV-1 subtypes B and E was used as the reference standard. Ninety-two percent of DBS samples were typeable as either HIV-1 subtype B or E. Serotype results with DBS and plasma were identical for 254 of 257 specimens. A simple DBS collection method provides a convenient alternative for conducting HIV-1 serotype surveillance while retaining sensitivity and specificity.