Neural encoding of individual words and faces by the human hippocampus and amygdala

Patients with lesions in the medial temporal lobe (MTL) of the brain, which includes the hippocampus, amygdala and parahippocampal gyrus, are severely impaired in their ability to remember and recognize words or faces which they saw only a short time ago. These lesions also prevent the effect of word repetition on cortical event-related potentials that are associated with these tasks. We have been able to study the response of individual neurons in the human medial temporal lobe to such delayed recognition tasks in epileptic patients undergoing neurosurgery. We found that some MTL neurons preferentially fired on sight of one particular word from a set of ten words used in a memory task, and others fired in response to one particular face. This stimulus-specific firing was maximal during the time that the neocortical event potentials are most sensitive to stimulus repetition, suggesting that the MTL contributes specific information to the cortex during the retrieval of recent memories.     

Expression of human proteoglycan in Chinese hamster ovary cells inhibits cell proliferation

In studying the functional role of an extracellular matrix proteoglycan, decorin, we have made observations that suggest a role for this proteoglycan in the control of cell proliferation. Extracellular matrices are made up of different combinations of collagens, elastin, hyaluronic acid, proteoglycans and various glycoproteins such as fibronectin. Most of these components can interact with cells, and much of the control of cell adhesion, migration and differentiation appears to be mediated by these interactions. Earlier studies have also attributed growth-regulatory activities to intact extracellular matrices, but the individual molecules responsible for these effects have not been characterized. We report here that Chinese hamster ovary (CHO) cell lines expressing human decorin from a stably transfected complementary DNA construct form a more orderly monolayer and grow to a lower saturation density than control cells lacking decorin. The extent of the morphological changes correlates with the level of decorin expression, and the saturation density is inversely proportional to it. The reduction in the saturation densities of the cell lines with the highest expression of decorin is more than 50%. These results reveal a novel growth inhibitory mechanism which may be related to contact inhibition of cell proliferation.     

Pattern of covariation between life-history traits of European birds

A large amount of variation is found in most reproductive traits of birds. Clutch size for instance, can vary from 1 to 15 between species of similar body weight. The adaptive significance of this variation is only poorly understood. According to life-history theory, large clutch size and early onset of reproduction are expected when the chances of survival are low. There is some support for the existence of such a relationship from studies of single species. Here I present evidence that, in European birds, clutch size is increased, and onset of reproduction occurs earlier in life, when the probability of survival is low.     

MHC polymorphism pre-dating speciation

Two features distinguish the polymorphism of the major histocompatibility complex (MHC) loci from that of other loci: its high diversity and the large genetic distance between MHC alleles. More than 100 alleles exist in natural populations in the mouse at each of the functional class I and class II alleles, all alleles occurring at frequencies that cannot be explained by recurrent mutations. Some of the alleles differ by approximately 70 nucleotides in the coding region alone and some of the products of the allelic genes differ by more than 50 amino acids. It has generally been assumed that these differences accumulated after species inception. Here, we present evidence for an alternative explanation of the origin of MHC polymorphism: a large part of the MHC polymorphism pre-dates speciation and is passed on from species to species. We describe allelic differences that must have arisen before the separation of mice and rats from a common ancestor more than 10 million years ago.     

Noradrenaline contracts arteries by activating voltage-dependent calcium channels

Noradrenaline (NA) regulates arterial smooth muscle tone and hence blood vessel diameter and blood flow. NA apparently increases tone by causing a calcium influx through the cell membrane. Two calcium influx pathways have been proposed: voltage-activated calcium channels and NA-activated calcium-permeable channels that are voltage-insensitive. Although voltage-activated calcium channels have been identified in arterial smooth muscle, voltage-insensitive calcium channels activated by NA have not. We show here that NA contractions of rabbit mesenteric arteries increase with depolarization. The increase parallels the elevation of open-state probability (P0) of single, voltage-dependent calcium channels. The action of noradrenaline can be explained by NA-activating voltage-dependent calcium channels, rather than by opening a second type of channel. We show directly that NA increases the open-state probability of single calcium channels. Thus, in the presence of NA, calcium entry through voltage-dependent calcium channels can regulate smooth muscle tone at physiological membrane potentials. These results may have relevance to pathophysiological conditions such as hypertension.     

高梁叶中的多核纤维和分隔纤维

高粱(Sorghum vulgares Pers.)叶中的纤维在发育过程中出现多个细胞核现象,细胞核的数目1～7个,一般为1～3个。这种多核纤维的细胞核形状也不同,有圆球形、纺锤形和伸长的线形。纤维中出现的多核现象是由于纤维在早期发育过程中连续进行核分裂形成的,或者是发育的分隔纤维在形成横隔前出现短暂的多核时期。除这种多核纤维外,高粱叶中还青许多具有生活原生质体的分隔纤维。     

汽轮发电机端部似稳涡流场数学模型

导出了描述发是端部涡流场的边值问题，并讨论了此问题的确定性。导出了与此边值问题等价的条件变化问题，并给出了三维行波场下变分式的具体形式。对ＱＦＳ－３００－２型汽轮发电机的端部场作了实例计算，计算结果与测试结果是一致的，证实了本文所提出的数学模型的正确性。     

Suppression of in vitro haematopoiesis following human immunodeficiency virus infection

Viral infections are frequently associated with haematological disorders. Abnormalities including leukopenia, anaemia and thrombocytopenia are commonly observed in patients with the acquired immune deficiency syndrome (AIDS) or the AIDS-related complex (ARC). The underlying cause of these haematological abnormalities is poorly understood. We report here that bone marrow progenitors isolated from AIDS or ARC patients are responsive to recombinant human granulocyte-macrophage colony stimulating factor (rGM-CSF) and recombinant erythropoietin. Antibodies present in the serum of patients infected with the human immunodeficiency virus (HIV), however, could suppress the growth of these progenitors, but not the growth of progenitors from HIV seronegative controls. A component of this immune-mediated suppression appears to be antibodies directed towards the envelope glycoprotein (gp120) of HIV.     

Assignment of multiple endocrine neoplasia type 2A to chromosome 10 by linkage

Multiple endocrine neoplasis type 2A (MEN2A) is one of several kinds of cancers that appear to be inherited in an autosomally dominant fashion. We have assigned the MEN2A locus to chromosome 10 by linkage with a new DNA marker (D10S5). The linkage led us to investigate other chromosome 10 markers and demonstrate linkage between the disease locus and the interstitial retinol-binding protein (IRBP) gene. The D10S5 locus was sublocalized to 10q21.1 by hybridization in situ and the IRBP gene to p11.2----q11.2 with a secondary site at q24----q25. The linkages were established using 292 members of five families, three different restriction fragment length polymorphisms (RFLPs) at D10S5 and two RFLPs recognized by the IRBP probe. The recombination frequencies from pairwise linkage analysis between the disease and two marker loci D10S5 and IRBP were 0.19 and 0.11, with maximum lod scores of 3.6 and 8.0 respectively. Ordering of the three loci by multipoint analysis placed the IRBP gene approximately midway between the disease and D10S5 loci.     

The genetic defect in familial Alzheimer's disease is not tightly linked to the amyloid beta-protein gene

Amyloid beta-protein (AP) is a peptide of relative molecular mass (Mr) 42,000 found in the senile plaques, cerebrovascular amyloid deposits, and neurofibrillary tangles of patients with Alzheimer's disease and Down's syndrome (trisomy 21). Recent molecular genetic evidence has indicated that AP is encoded as part of a larger protein by a gene on chromosome 21 (refs 5-7). The defect in the inherited autosomal dominant form of Alzheimer's disease, familial Alzheimer's disease (FAD), has been mapped to the same approximate region of chromosome 21 by genetic linkage to anonymous DNA markers, raising the possibility that this gene product, which could be important in the pathogenesis of Alzheimer's disease, is also the site of the inherited defect in FAD (ref. 5). We have determined the pattern of segregation of the AP gene in FAD pedigrees using restriction fragment length polymorphisms. The detection of several recombination events with FAD suggests that the AP gene is not the site of the inherited defect underlying this disorder.