Adaptive changes in locomotor activity following botulinum toxin injection in ankle extensor muscles of cats.

The present study investigated the adaptations made in motor behavior following a temporary reduction in ankle extensor activity in the walking cat. Temporary muscle weakness was induced by injecting botulinum toxin into the lateral gastrocnemius (LG), plantaris (PL), and soleus (SOL) muscles, or SOL alone. The medial gastrocnemius (MG) muscle was not injected. Adaptations in the level of muscle activity were recorded using chronically implanted electromyographic (EMG) electrodes. Serial recordings were made prior to botulinum toxin injections and for several days following the injections. Kinematic analysis of ankle joint movements was made from video records to assess the impact of the botulinum toxin injections on the function of the ankle joint during walking. Following injection of the LG, PL, and SOL muscles with botulinum toxin, the amplitude of the MG burst increased over a period of a few days to a week. This increase was similar to the previously reported changes produced in MG following transection of the nerves serving LG, PL, and SOL. Following the weakening of the ankle extensor muscles, there was a temporary deficit in ankle function during walking as evidenced by a marked increase in the amount of ankle flexion that occurred at stance onset. This functional deficit recovered relatively quickly and was not associated with a return of the EMG pattern to the preinjection pattern. After recovery from the initial injections, a second injection of botulinum toxin into SOL alone was performed. No functional deficits were observed in the ankle movements during walking following this second injection. However, weakening SOL produced increases in the burst amplitudes of the MG, LG, and PL muscles over a period of a few days. This suggests that normal movements at the ankle during walking can be generated with more than one pattern of ankle extensor activity and that there is flexibility in how the necessary torque is produced. A final procedure, transection of the nerves serving LG, PL, and SOL, failed to produce any functional deficits in ankle movements. The implication is that adaptations to the neural control of ankle extensor activity that were induced by the initial procedure persisted after the recovery of the injected muscles and were sufficient to compensate for the subsequent challenges.     

Genetic variation in ICF syndrome: evidence for genetic heterogeneity

ICF syndrome is a rare autosomal recessive immunoglobulin deficiency, sometimes combined with defective cellular immunity. Other features that are frequently observed in ICF syndrome patients include facial dysmorphism, developmental delay, and recurrent infections. The most diagnostic feature of ICF syndrome is the branching of chromosomes 1, 9, and 16 due to pericentromeric instability. Positional candidate cloning recently discovered the de novo DNA methyltransferase 3B (DNMT3B) as the responsible gene by identifying seven different mutations in nine ICF patients. DNMT3B specifically methylates repeat sequences adjacent to the centromeres of chromosome 1, 9, and 16. Our panel of 14 ICF patients was subjected to mutation analysis in the DNMT3B gene. Mutations in DNMT3B were discovered in only nine of our 14 ICF patients. Moreover, two ICF patients from consanguineous families who did not show autozygosity (i.e. homozygosity by descent) for the DNMT3B locus did not reveal DNMT3B mutations, suggesting genetic heterogeneity for this disease. Mutation analysis revealed 11 different mutations, including seven novel ones: eight different missense mutations, two different nonsense mutations, and a splice-site mutation leading to the insertion of three aa's. The missense mutations occurred in or near the catalytic domain of DNMT3B protein, indicating a possible interference with the normal functioning of the enzyme. However, none of the ICF patients was homozygous for a nonsense allele, suggesting that absence of this enzyme is not compatible with life. Compound heterozygosity for a missense and a nonsense mutation did not seem to correlate with a more severe phenotype.     

Strategic control and medial frontal negativity: beyond errors and response conflict

Errors in timed choice tasks typically produce an error-related negativity (ERN) in the event-related potential (ERP). The error specificity of the ERN has been challenged by studies showing a correct response negativity (CRN). Forty-five participants engaged in a flanker task in which both compatibility between flankers and target and the probability of compatible flankers were manipulated. Correct responses elicited a CRN, the amplitude of which increased with the degree of mismatch between the presence of conflict and conflict probability, even on low-conflict (compatible) trials. The fronto-central N2 component was larger on high-conflict (incompatible) correct response trials. However, in contrast to some recent accounts, this N2 was largest for highly probable stimuli. These findings suggest revision to models of the effects of conflict on response-related negativity to account for strategic adjustments made in preparation for the response.     

ImuVert activation of natural killer cytotoxicity and interferon gamma production via CD16 triggering

The effect and mechanism of action of ImuVert, a new biological response modifier consisting of ribosomes and natural membrane vesicles of Serratia marcescens, on endogenous natural killer (NK) cells and activated NK activity has been analyzed. The studies showed that endogenous NK activity of peripheral blood mononuclear cells (PBMC) from normal cell donors was significantly increased (P less than 0.03) against K562, U937, and Molt-4 target cells. PBMC from cord blood of newborn infants lacking NK activity were upregulated (1.5-4 fold over endogenous NK activity) by ImuVert. Other studies showed that the abnormal NK activity of PBMC from patients with the human immunodeficiency virus (HIV) infection was significantly augmented in vitro (P less than 0.01) by ImuVert. ImuVert strongly stimulated interferon gamma production and in combination with interleukin 2 produced synergistically enhanced interferon gamma production and greater cytotoxicity than that induced by either alone. Studies on lymphocyte differentiation antigen expression following treatment with ImuVert indicated that ImuVert triggers interferon gamma production through binding the low affinity IgG Fc receptor, type III, CD16. The studies suggest that ImuVert may trigger interferon gamma production by binding to the Fc receptor and that the amplitude of the ensuing reaction and the ability of ImuVert to induce cytotoxicity in a setting where this activity has been down regulated is based on the absence of suppressor activation or direct contra suppressor activity.     

Brain regions and their dynamics in prospective memory retrieval: a MEG study.

We measured brain activity using magnetoencephalography in five participants during ongoing tasks that included prospective memory, retrospective memory, and oddball trials. Sources were identified in the hippocampal formation and posterior parietal and frontal lobes. Posterior parietal cortex activation had an earlier onset in the prospective memory condition than retrospective memory or oddball conditions, a higher level of theta activity in the retrospective condition, and higher levels of upper alpha in the prospective and oddball conditions. Activation of the hippocampal formation had a longer duration in the retrospective memory and prospective memory conditions than the oddball condition, but prominent alpha and theta band activity was present in all three conditions. We interpret the early (87 ms) onset of activity in parietal cortex as evidence for an initial noticing of appropriate conditions for a PM response. Hippocampal activity may reflect a subsequent memory search for the intended action.     

Genetic variants of chronic granulomatous disease: prevalence of deficiencies of two cytosolic components of the NADPH oxidase system

Chronic granulomatous disease, a syndrome of recurrent infections and failure of oxidative microbicidal activity in phagocytes, results from defects in the gene for one of several components of an oxidase system that can undergo activation. To determine the relative prevalence of certain of the genetic variants of this disorder, we used immunoblotting to detect two specific neutrophil cytosolic proteins of 47 and 67 kd recently shown to be required for oxidase activation. Chronic granulomatous disease is usually an X-linked disorder associated with the absence of membrane cytochrome b558. Of our 94 patients with chronic granulomatous disease, however, 36 had a phenotype characterized by autosomal inheritance, normal membrane oxidase components (including cytochrome b558), and functionally defective cytosolic activity in a cell-free oxidase system. We studied 25 of these 36 patients and found that 22 lacked the 47-kd cytosolic protein, and the remaining 3 were missing the 67-kd component. Patients with chronic granulomatous disease whose functional defect was localized to the neutrophil membrane (classic X-linked cytochrome b-negative type and two other rare variants) had normal amounts of both cytosolic components. We estimate that approximately 33 percent of all patients with chronic granulomatous disease are missing the 47-kd cytosolic oxidase component and about 5 percent of patients are missing the 67-kd component. Chronic granulomatous disease caused by a defect in any cytosolic factors other than the 47-kd and 67-kd proteins, if it exists, is apparently rare.     

Proprioceptive input patterns elevator activity in the locust flight system

1. In the locust, Locusta migratoria, the roles of two groups of wing sense organs, hind wing tegulae and wing-hinge stretch receptors, in the generation of the flight motor pattern were investigated. A preparation was employed that allowed the intracellular recording of neural activity in almost intact tethered flying locusts or after selective manipulations of sensory input. The functions of the two sets of receptors were assessed 1) by studying the phases of their discharges in the wingbeat cycle (Fig. 3), 2) by the selective ablation of input from the receptors (Figs. 4-7), and 3) by the selective stimulation of the receptor afferents (Figs. 8-12). 2. Input from the tegulae was found to be responsible for the initiation of elevator activity (Figs. 9 and 10) and for the generation of a distinct initial rapid depolarization (Figs. 4, 5, and 8) characteristic of elevator motor neuron activity in intact locusts (Figs. 1 and 16). 3. Input from the wing-hinge stretch receptors was found to control the duration of elevator depolarizations by the graded suppression of a second late component of the elevator depolarizations as wingbeat frequency increased (Figs. 6, 7, 11, and 12). The characteristics of this late component of elevator activity suggested that it is generated by the same (central nervous) mechanism that produces the elevator depolarizations recorded in deafferented animals (Fig. 2). Apparently this late component contributes to the intact pattern of elevator depolarizations only at lower wingbeat frequencies and is abolished by the action of stretch-receptor input at frequencies above approximately 15 Hz (Figs. 1, 2, and 4). At these high wingbeat frequencies elevator activity is dominated by the rapid depolarizations generated as a result of tegula input. 4. The present study demonstrates 1) that the timing of elevator motor neuron activity is determined by phasic afferent input from tegulae and stretch receptors and 2) that input from the stretch receptors controls the duration of elevator activity in the wingbeat cycle following the wing movement that was responsible for the generation of the receptor discharge.     

Triggering of locust jump by multimodal inhibitory interneurons

1. The locust jump is triggered by a sudden inhibition of activity in hindleg flexor tibiae motoneurons following cocontraction of the hindleg flexor and extensor tibiae muscles. The main result of this investigation was the identification of two interneurons (one for each hindleg) that monosynaptically inhibit flexor tibiae motoneurons and whose properties are all consistent with them being the trigger interneurons for initiating a jump. 2. These interneurons receive strong excitatory input from many sensory modalities (visual, auditory, tactile, and proprioceptive). Because of their multimodal response characteristics, we designated them M-neurons. A particularly strong excitatory input to each M-neuron is from both descending contralateral movement detector (DCMD) interneurons. 3. The threshold for spike initiation in the M-neurons is high (approximately 14 mV). As a consequence, input from any one sensory modality alone rarely initiates action potentials. 4. Each M-neuron is depolarized by sensory input from leg proprioceptors. We propose that proprioceptive feedback during the cocontraction phase depolarizes the M-neurons to decrease their threshold, thus enabling extrinsic sensory stimuli to generate action potentials in both M-neurons and in so doing trigger a jump. The function of the proprioceptive gating of inhibitory transmission from the various sensory systems to the flexor motoneurons (via the M-neurons) is to ensure the development of a strong isometric contraction of the extensor tibiae muscle, and thus a powerful jump in response to external stimuli. 5. Insofar as the initiation of the locust jump depends on sensory convergence onto large identified interneurons, this behavior is similar to ballistic movements in some other animals such as the crayfish tail flip and the startle response in fish. The unique feature of the locust jump is that the trigger interneurons initiate the jump only after a preceding phase (cocontraction) has been accomplished.     

Relapsing diabetes can result from moderately activating mutations in KCNJ11

Neonatal diabetes can either remit and hence be transient or else may be permanent. These two phenotypes were considered to be genetically distinct. Abnormalities of 6q24 are the commonest cause of transient neonatal diabetes (TNDM). Mutations in KCNJ11, which encodes Kir6.2, the pore-forming subunit of the ATP-sensitive potassium channel (K(ATP)), are the commonest cause of permanent neonatal diabetes (PNDM). In addition to diabetes, some KCNJ11 mutations also result in marked developmental delay and epilepsy. These mutations are more severe on functional characterization. We investigated whether mutations in KCNJ11 could also give rise to TNDM. We identified the three novel heterozygous mutations (G53S, G53R, I182V) in three of 11 probands with clinically defined TNDM, who did not have chromosome 6q24 abnormalities. The mutations co-segregated with diabetes within families and were not found in 100 controls. All probands had insulin-treated diabetes diagnosed in the first 4 months and went into remission by 7-14 months. Functional characterization of the TNDM associated mutations was performed by expressing the mutated Kir6.2 with SUR1 in Xenopus laevis oocytes. All three heterozygous mutations resulted in a reduction in the sensitivity to ATP when compared with wild-type (IC(50) approximately 30 versus approximately 7 microM, P-value for is all <0.01); however, this was less profoundly reduced than with the PNDM associated mutations. In conclusion, mutations in KCNJ11 are the first genetic cause for remitting as well as permanent diabetes. This suggests that a fixed ion channel abnormality can result in a fluctuating glycaemic phenotype. The multiple phenotypes associated with activating KCNJ11 mutations may reflect their severity in vitro.     

藏汉民族线粒体基因组全序列的比较研究

目的 以藏汉民族线粒体基因组全序列为基础,进行Haplogroup构建和系统发生分析,在全序列水平上比较核苷酸的变异,阐释可能的变异机制和蕴含的生物学意义.方法 采用Applied Biosystems 3730DNA自动测序仪分别对40名藏族和50名汉族的标本进行线粒体DNA序列测定,应用phredPhrap 16.0软件进行全序列拼接,并以rCRS(revised Cambridge Reference Sequence)为标准与测定序列进行比对分析;根据MTTO-MAP的标准,通过Network方法进行Haplogroup构建和系统发生的分析,并结合其它方法对产生的数据进行深入解读.结果 数据分析结果显示:在系统发生上,藏汉民族90个线粒体DNA序列归类到13个Haplogroups,除M9以外,其它各Haplogroup出现频率之间比较差异无统计学意义;通过两个民族的线粒体DNA全序列比对,发现21个分布频率有统计学意义的变异位点,其中的5个为新变异位点;另外,对D-Loop区的5个突变位点进行了单倍型构建,90个标本可分为2种Supertype,发现在藏汉民族之间Supertypel和Supertype 2的分布频率均有统计学意义.结论 藏汉民族在种族起源和系统发生上具有较近的母系遗传关系;在全序列有统计学意义的位点究竟是适应性或者中性选择,抑或是一种病理性突变尚需深入的探讨.