Median frequency of the myoelectric signal

Summary A study was performed to investigate the changes that occur in the median frequency of the myoelectric signal during local ischemia or reduction of intramuscular temperature produced by surface cooling. Data was obtained from experiments which involved the first dorsal interosseous muscle of 10 female and 16 male subjects. These subjects were asked to perform isometric constant-force abduction contractions of the index finger at 20% and 80% of maximal voluntary contraction level. The initial median frequency (IMF) of the myoelectric signal during the first 0.5 s of contraction was calculated. Results showed a significant reduction of the IMF in contractions performed under ischemic conditions; upon release, the IMF recovered quickly. At 80% maximal voluntary level of contraction, a greater decrease of the IMF was recorded. Similar results were demonstrated during reduction of intramuscular temperature with gradual recovery of the IMF after cooling. These results demonstrate that the median frequency of the myoelectric signal displays behavior similar to that reported for conduction velocity and this is consistent with the notion that accumulation of metabolic byproducts in muscle tissue causes a decrease in the conduction velocity of the muscle fibers.Dr. R. Merletti was on a leave of absence from the Institute of Electrical Engineering, Politecnico di Torino, Italy     

T lymphocytes in children with recurrent respiratory infections: effect of the use of thymostimulin on the alterations of T-cell subsets

OKT3-, OKT4- and OKT8-positive cells were estimated in 303 children with recurrent respiratory infections. The patients (selected by a score method) had experienced 13 or more infections a year. Modifications in T-cell subsets were observed in 154 patients (50.8%). Decreased OKT3- and OKT4-positive cells were present in 80 children (26.4%), while 74 patients (24.4%) showed normal values of OKT3-positive cells but decreased OKT4- and increased OKT8-positive cells. An attempt at treatment with thymostimulin was undertaken in a group of randomly chosen children with modifications in T-cell subsets. The use of thymostimulin induced the treated children more readily than the untreated ones to show improvement in both the score for respiratory infections and the distribution of T-cell subsets.     

New studies on the Macushi Indians of northern Brazil

Demographic data and genetic information concerning 40 genetic systems are reported for three populations of Macushi Indians, and have been compared to those already obtained for three other communities of this tribe. These are young populations (mean age, 19 years), with a low sex ratio (90), low percentages of non-Indian ancestry (1-2%) and of marriages between locally born persons (34). Intertribal unions (14%) are less frequent than among their neighbours, the Wapishana. Fertility is high (average of 8.2 children per woman who completed reproduction), but the variance in family size and the frequency of premature deaths relatively low for populations at this cultural level. This conditions the lowest Index of Opportunity for Selection (0.45) calculated thus far among South American Indians. No variation was observed in 20 genetic systems, limited variation in 3, and larger variability in the remaining 17. In 13 of the 29 comparisons (45%), the Macushi gene frequencies present values in the middle third of the range observed among South American Indians. The previously reported private genetic polymorphism of esterase A was encountered in one of the three villages. A comparison of the genetic distances between villages with and without this polymorphism, and a similar comparison for the villages of the neighbouring Wapishana, yields no clue as to the tribe in which this polymorphism originated.     

Cytogenetic and clinical studies in gonadal dysgenesis with 46,X,Xt(qter leads to p221::p223 leads to qter) karyotype: review and phenotype/karyotype correlations.

Chromosome analysis by Q, R, and C banding was performed in a case diagnosed clinically as gonadal dysgenesis and the karyotype was shown to be 46,X,Xt(qter leads to p221::p223 leads to qter). Localisation of the breakpoints in the fused X chromosomes and replication studies have led to a hypothesis on the origin of the translocation. A comparison of clinical and cytogenetical findings in this and other published cases has also been made in an attempt to detect some phenotype/karyotype correlations.     

Semi-automated analysis of manually reconstructed tracks of progressively motile human spermatozoa

Several alternative algorithms for computer-assisted derivationof measurements of movement characteristics from manually reconstructedtracks of progressively motile human spermatozoa were compared.Fifty tracks were reconstructed at 30 Hz from video recordingsand analysed using traditional manual methods and by four combinationsof computer algo rithms. The best algorithm set was identified(‘Video-mot.mdpt’) and the values for the curvilinear,average path and linear velocities (V_CVL, V_AVE and V_LIN respectively),the amplitude of lateral displacement of the sperm head aboutthe axis of progression (A_H) and the number of times the spermhead crossed the average path (the ‘beat/cross frequency’,BXF) obtained using it were compared to those obtained by manualanalysis. There was a considerable time saving when the computer-assistedmethod was used and the values it gave for the various movementcharacteristics showed good correspondence with those obtainedmanually. In addition, repeated data entry and analysis wasfound to be highly reproducible. When the tracks were re-plottedat 6 Hz (as used by the multiple-exposure photomicrography methodfor sperm motility analysis) insufficient information remainedin the tracks for reliable determination of anything other thanV_LIN We conclude that the Videomot.mdpt program provides reliablevalues for the movement characteristics of progressively motilehuman spermatozoa, and believe it will be of great value inthe validation of commercial systems providing automated spermmovement analysis and in laboratories which do not have accessto such costly equipment.     

Selective depletion of the OKT 4+ 4B4+ subset in lymph nodes from HIV+ patients

We have used 4B4 and 2H4 monoclonal antibodies in conjunction with OKT 4 to quantify T cell subsets in lymph node suspensions from human immunodeficiency virus (HIV) positive subjects with lymphadenopathy syndrome. The data indicate that the reduced OKT 4:OKT 8 ratio was due to a depletion of the OKT 4+ 4B4+ subset. In contrast, there were no differences compared to reactive controls, considering the OKT8+ subpopulation. These alterations may be related to the immunological deficiency associated with HIV infection.     

Blood platelets in human essential hypertension

Blood platelets of patients with essential hypertension display signs of both increased sensitivityin vitro to aggregating stimuli believed to contribute to thrombosis and of activationin vivo possibly expressing the release of vasoactive products. The mean features of the modified platelet profile in hypertension include an increased ₂-adrenergic receptor density, an enhanced rate of adhesion/aggregation in particular in response to ADP and arachidonic acid, a greater sensitivity for thrombin and adrenaline to stimulate increases in cytoplasmatic-free Ca²⁺, increased resting levels of cytoplasmatic-free Ca²⁺, a reduced content of serotonin often combined with a defective uptake mechanism, a facilitated efflux rate of noradrenaline, an exaggerated release reactionin vivo as indicated by the increased plasma levels of Betathromboglobulin and a shortened platelet life span. These changes occur to various extents in some, but not all, hypertensive patients and are not always strictly related to the degree of blood pressure increase. On the contrary, platelet cyclooxygenase and thromboxane synthetase activity are in the normal range.     

Oxatomide protectsTrichinella spiralis infected mice from lethal anaphylaxis

Infection withTrichinella spiralis in mice was accompanied by allergic sensitization as evidenced by anaphylactic death after intravenous injection of the antigen. Pre-treatment of the animals with oxatomide, a new orally active antiallergic drug, resulted in significant protection of the animals; the lowest effective dose of the compound was 1.25 mg/kg orally. In contrast to cyproheptadine, oxatomide offered little protection against serotonin toxicity in mice.The present data suggest that, in this model of systemic hypersensitivity, the anti-anaphylactic effect of oxatomide can be attributed mainly to inhibition of release of allergic mediators.     

Dissociation between onset of natural killer E-rosette forming cells and of T3-positive cells following HLA-mismatched T cell depleted bone marrow transplantation.

We have studied immunological reconstitution following partially HLA-incompatible T cell depleted bone marrow transplantation, compared with reconstitution following HLA identical T cell depleted and HLA identical untreated bone marrow transplantation. We often observed an early emergence of E-rosette forming cells that were T3 negative and displayed strong natural killer activity in the first group of patients. This activity was shown with fresh leucocytes as well as interleukin 2 grown cells. The appearance of T3+ cells was delayed in this situation compared to that observed in HLA identical bone marrow transplantation. The delay in T3+ cell differentiation and in cellular immune function development probably explains why NK rosette forming cells are early detected within 3-4 months following HLA mismatched bone marrow transplantation. This NK subset is likely to be present at an early stage in all types of bone marrow transplantation, but is most commonly observed simultaneously with the T3+ cells in HLA identical untreated bone marrow transplantation. The respective role of T cell depletion and HLA incompatibility in this phenomenon are discussed while patients' conditioning, cyclosporine A and graft-versus-host disease have been shown to be irrelevant for the dissociation between NK E-rosette forming cells and T3+ subset onsets.