Brain-derived neurotrophic factor enhances cholinergic contraction of longitudinal muscle of rabbit intestine via activation of phospholipase C.

Brain-derived neurotrophic factor (BDNF) belongs to the neurotrophin family of proteins best known for its role in neuronal survival, differentiation, migration, and synaptic plasticity in central and peripheral neurons. BDNF is also widely expressed in nonneuronal tissues including the gastrointestinal tract. The role of BDNF in intestinal smooth muscle contractility is not well defined. The aim of this study was to identify the role of BDNF in carbachol (CCh)- and substance P (SP)-induced contraction of intestinal longitudinal smooth muscle. BDNF, selective tropomyosin-related kinase B (TrkB) receptor agonists, and pharmacological inhibitors of signaling pathways were examined for their effects on contraction of rabbit intestinal longitudinal muscle strips induced by CCh and SP. BDNF activation of intracellular signaling pathways was examined by Western blot in homogenates of muscle strips and isolated muscle cells. One-hour preincubation with BDNF enhanced intestinal muscle contraction induced by CCh but not by SP. The selective synthetic TrkB agonists LM 22A4 and 7,8-dihydroxyflavone produced similar effects to BDNF. The Trk antagonist K-252a, a TrkB antibody but not p75NTR antibody, blocked the effect of BDNF. The enhancement of CCh-induced contraction by BDNF was blocked by the phospholipase C (PLC) antagonist U73122, but not by ERK1/2 or Akt antagonists. Direct measurement in muscle strips and isolated muscle cells showed that BDNF caused phosphorylation of TrkB receptors and PLC-γ, but not ERK1/2 or Akt. We conclude that exogenous BDNF augments the CCh-induced contraction of longitudinal muscle from rabbit intestine by activating TrkB receptors and subsequent PLC activation.

Data driven AI (artificial intelligence) detection furnish economic pathways for microplastics.

Microplastics pollution is killing human life, contaminating our oceans, and lasting for longer in the environment than it is used. Microplastics have contaminated the geochemistry and turned the water system into trash barrel. Its detection in water is easy in comparison to soil and air so the attention of researchers is focused on it for now. Being very small in size, microplastics can easily cross the water filtration system and end up in the ocean or lakes and become the prospective challenge to aquatic life. This review piece provides the hot research theme and current advances in the field of microplastics and their eradication through the virtual world of artificial intelligence (AI) because Microplastics have confrontation with clean water tactics.

Epidemiology of Mycoplasma bovis in Pennsylvania veal calves.

The objective of the study was to estimate the prevalence and incidence of Mycoplasma bovis, a common cause of pneumonia, in veal calves. Using simple random sampling, 252 calves from 4 veal herds located in central Pennsylvania were selected and longitudinally followed for monthly collection of nasal swabs. Bronchial swabs and lung lesions were collected at the slaughterhouse. Nasal, bronchial, and lung lesion swabs were cultured for bacterial respiratory pathogens. Ninety lung lesions were identified, of which 41.1, 1.1, 1.1, 7.8, and 4.4% were culture positive for M. bovis alone, Pasteurella multocida alone, Mannheimia haemolytica alone, M. bovis and P. multocida co-infection, and M. bovis and M. haemolytica co-infection, respectively. The data indicate that potential interventions, such as therapeutics, vaccines, or management control measures, would be most effective before 50 d of age based upon the cumulative incidence of colonization.

Contractile agonists attenuate cGMP levels by stimulating phosphorylation of cGMP-specific PDE5; an effect mediated by RhoA/PKC-dependent inhibition of protein phosphatase 1.

BACKGROUND AND PURPOSE: In gastrointestinal smooth muscle cGMP levels in response to relaxant agonists are regulated by PKG-mediated phosphorylation and activation of phosphodiesterase 5 (PDE5). The aim of the present study was to determine whether contractile agonists modulate cGMP levels by cross-regulating PDE5 activity and to identify the mechanism of action. EXPERIMENTAL APPROACH: Dispersed and cultured muscle cells from rabbit stomach were treated with the nitric oxide donor, S-nitrosoglutathione (GSNO), or with a contractile agonist, ACh and GSNO. PDE5 phosphorylation and activity, and cGMP levels were determined. KEY RESULTS: GSNO stimulated PDE5 phosphorylation and activity and increased cGMP levels in gastric smooth muscle cells. Concurrent activation of cells with ACh augmented GSNO-stimulated PDE5 phosphorylation and activity, and attenuated cGMP levels. The effect of ACh was blocked by the m3 receptor antagonist and by inhibitors of protein kinase C (PKC) or RhoA, but not by the m2 receptor antagonist or inhibitors of PI hydrolysis. The effects of ACh on PDE5 phosphorylation and activity, and cGMP levels were mimicked by a low concentration of tautomycin (10 nM), and a high (1 microM) but not low (1 nM) concentration of okadaic acid. PDE5 was associated with protein phosphatase 1 (PP1) and dephosphorylated by the catalytic subunit of PP1 but not PP2A. CONCLUSION AND IMPLICATIONS: In gastrointestinal smooth muscle cGMP levels are cross-regulated by contractile agonists via a mechanism that involves RhoA-dependent, PKC-mediated inhibition of PP1 activity. This leads to augmentation of PDE5 phosphorylation and activity, and inhibition of cGMP levels.

Development of endosulfan tolerant strain of an egg parasitoid Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae).

A strain of T. chilonis, an egg parasitoid of lepidopteran pests tolerant to the most commonly used cyclodiene insecticide--endosulfan was developed in the laboratory. Tolerance to endosulfan was induced by exposing adult parasitoids sequentially from a sub-lethal concentration (0.004%) to the field recommended concentration (0.09%). The strain acquired tolerance to the insecticide after 341 generation of continuous exposure with LC50 values of 1074.96 ppm as compared to LC50 of (70.91 ppm) in susceptible strain. The genetical study showed that F1 crosses exhibited a semi-dominant response to endosulfan with degree of dominance value (D) of 0.58. The resistant factor of tolerant strain was 15.1 folds and of F1 cross were 8.53 folds over susceptible strain. Under net house conditions, the tolerant strain parasitised 56% Helicoverpa armigera eggs on potted cotton plants immediately after an insecticide spray, compared to 3% by the susceptible strain. High percentage survival of the immature stages of the tolerant strain proved their ability to withstand the insecticide load. Breakdown of insecticide tolerance in the strain occurred after four generations in absence of insecticide load. Use of the tolerant strain as a component of bio-intensive IPM in various crops where insecticide use is higher is discussed.

Effect of dietary supplementation of garlic, ginger and their combination on feed intake, growth performance and economics in commercial broilers.

AIM: The present study was carried out to evaluate the effect of supplementation of garlic, ginger and their combination in the diets of broiler chickens and assessment in terms of feed intake, growth performance and economics of feeding. MATERIALS AND METHODS: A total of 240 1-day-old Cobb-400 broiler chicks were randomly assigned to four dietary treatments each with three replicates of 20 chicks per replicate (n=60). Four experimental diets were formulated in such a way that control diet (T1) contained neither ginger nor garlic. While, birds in group T2 and T3 were fed with diets containing 1% garlic and ginger, respectively. Diet 4 (T4 group) contained a combination of 1% of garlic and ginger. The feeding experiment was carried out for 42 days, and different parameters evaluated includes feed intake, weight gain, feed conversion ratio, gut morphometry, and economics of feeding in terms of return over feed cost (ROFC) and European Performance Efficiency Index. RESULTS: Feed intake of experimental birds in ginger and mixture of garlic and ginger supplemented groups, i.e., T3 and T4 groups have significantly (p<0.05) higher feed intake as compared to control. While, feeding of garlic have non-significant effect on feed intake as compared to other groups. A body weight gain (g/bird) was found to be significantly (p<0.05) higher in garlic (T2 group) and ginger (T3 group) supplemented group as compare to control and garlic and ginger mixture supplemented group (T4 group). Feed conversion ratio was significantly (p<0.05) lower in ginger (T3 group) supplemented group as compare to other groups. Mean villi length, villi width and cryptal depth were significantly (p<0.05) higher in T3 group than rest of all three groups, indicating increased absorptive surface area. ROFC was significantly (p<0.05) lower in T3 and T4 groups as compare to control. However, it was not significantly different between control and T2 group. CONCLUSION: On the basis of the results of the study, it is concluded that supplementation of garlic improves the performance of broilers when added at the rate of 1% of broiler ration and can be a viable alternative to antibiotic growth promoter in the feeding of broiler chicken.

Signal transduction in gastrointestinal smooth muscle.

Signal transduction in gastric and intestinal smooth muscle is mediated by receptors coupled via distinct G proteins to various effector enzymes, including PI-specific PLC-beta 1 and PLC-beta 3, and phosphatidylcholine (PC)-specific PLC, PLD and PLA2. Activation of these enzymes is different in circular and longitudinal muscle cells, generating Ca(2+)-mobilizing (IP3, AA, cADPR) and other (DAG) messengers responsible for the initial and sustained phases of contraction, respectively. IP3-dependent Ca2+ release occurs only in circular muscle. Ca2+ mobilization in longitudinal muscle involves a cascade initiated by agonist-induced transient activation of PLA2 and formation of AA, AA-dependent depolarization of the plasma membrane and opening of voltage-sensitive Ca2+ channels. The influx of Ca2+ induces Ca2+ release by activating sarcoplasmic ryanodine receptor/Ca2+ channel and stimulates cADPR formation which enhances Ca(2+)-induced Ca2+ release. The initial [Ca2+]i transient in both muscle cell types results in Ca2+/calmodulin-dependent activation of MLC kinase, phosphorylation of MLC20 and interaction of actin and myosin. The sustained phase is mediated by a Ca(2+)-independent isoform of PKC, PKC-epsilon DAG for this process is generated by PLC- and PLD-mediated hydrolysis of PC. Relaxation is mediated by cAMP-and/or cGMP-dependent protein kinase which inhibit the initial [Ca2+]i transient and reduce the sensitivity of MLC kinase to [Ca2+]i. Relaxation induced by the main neurotransmitters, VIP and PACAP, involves two cascades, one of which reflects activation of adenylyl cyclase. A distinct cascade involves G-protein-dependent stimulation of Ca2+ influx leading to Ca2+/calmodulin-dependent activation of a constitutive eNOS in muscle cells; the generation of NO activates soluble guanylyl cyclase. The resultant activation of PKA and PKG is jointly responsible for muscle relaxation.

Association of milk components with intra-mammary inflammation in Jaffrabadi buffaloes.

AIM: To study the alteration of major milk components such as milk fat, protein, lactose, solid not fat (SNF) and total solids (TS) and their association with different degree of intra-mammary inflammation (IMI) in Jaffrabadi buffaloes. MATERIALS AND METHODS: Milk samples (n=1516) were collected from Jaffrabadi buffaloes separately from each quarter. Milk samples were analyzed for milk fat, protein, lactose, SNF and TS percent on the same day using milk analyzer "LACTOSCAN." Milk samples were checked for IMI by California mastitis test (CMT), and the results were expressed as negative (0), +, ++, and +++ CMT score. The traits of milk components which showed significant difference (p<0.05) between samples from inflamed and non-inflamed quarters were analyzed by receiver operating characteristic (ROC) analysis to see the accuracy and degree of association with IMI. RESULTS: Among several milk components, milk protein and lactose percent showed a significant difference (p<0.05) between milk samples from normal and inflamed quarters. Though, during the early stage of mammary gland inflammation milk protein percent remained significantly high (p<0.05), later with an increase in the degree of severity of inflammation it did not show any difference. Milk samples from normal udder quarters had significantly higher lactose percent than inflamed quarters (p<0.05). Milk lactose percent decreased gradually with an increase in the degree of severity of inflammation. ROC analysis revealed that milk samples having lactose content below the threshold values had significantly higher chances to come from inflamed udder quarters (p<0.05). Though, the value of the area under curve (AUC) indicated that milk lactose was significantly associated with IMI (p<0.05), the accuracy was moderate (AUC=0.71-0.75). CONCLUSIONS: The results of the present study indicated that milk lactose percent gradually and significantly reduced during IMI and can be used as a marker for identification of IMI in buffaloes. However, ROC analysis further confirmed that using milk lactose IMI can be identified with moderate accuracy.

Stimulation of synthesis and release of brain-derived neurotropic factor from intestinal smooth muscle cells by substance P and pituitary adenylate cyclase-activating peptide.

BACKGROUND: Brain-derived neurotrophic factor (BDNF) is a neurotrophin present in the intestine where it participates in survival and growth of enteric neurons, augmentation of enteric circuits, and stimulation of intestinal peristalsis and propulsion. Previous studies largely focused on the role of neural and mucosal BDNF. The expression and release of BDNF from intestinal smooth muscle and the interaction with enteric neuropeptides has not been studied in gut. METHODS: The expression and secretion of BDNF from smooth muscle cultured from the rabbit intestinal longitudinal muscle layer in response to substance P (SP) and pituitary adenylate cyclase-activating peptide (PACAP) was measured by western blot and enzyme-linked immunosorbent assay. BDNF mRNA was measured by reverse-transcription polymerase chain reaction. KEY RESULTS: The expression of BNDF protein and mRNA was greater in smooth muscle cells (SMCs) from the longitudinal muscle than from circular muscle layer. PACAP and SP increased the expression of BDNF protein and mRNA in cultured longitudinal SMCs. PACAP and SP also stimulated the secretion of BDNF from cultured longitudinal SMCs. Chelation of intracellular calcium with BAPTA (1,2-bis-(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid) prevented SP-induced increase in BDNF mRNA and protein expression and SP-induced secretion of BDNF. CONCLUSIONS & INFERENCES: Neuropeptides known to be present in enteric neurons innervating the longitudinal layer increase the expression of BDNF mRNA and protein in SMCs and stimulate the release of BDNF. Considering the ability of BDNF to enhance smooth muscle contraction, this autocrine loop may partially explain the characteristic hypercontractility of longitudinal muscle in inflammatory bowel disease.

Longitudinal smooth muscle of the mammalian intestine. A model for Ca2+ signaling by cADPR.

Ca2+ mobilization in muscle cells from the circular muscle layer of the mammalian intestine is mediated by IP3-dependent Ca2+ release. Ca2+ mobilization in muscle from the adjacent longitudinal muscle layer involves a distinct, phosphoinositide-independent pathway. Receptors for contractile agonists in longitudinal muscle cells are coupled via a pertussis toxin-sensitive G protein to activation of PLA2 and formation of arachidonic acid (AA). The latter activates Cl- channels resulting in depolarization of the plasma membrane and opening of voltage-sensitive Ca2+ channels. Ca2+ influx via these channels induces Ca2+ release by activating sarcoplasmic ryanodine receptor/Ca2+ channels. The increase in [Ca2+]i activates membrane-bound ADP ribosyl cyclase, and the resultant formation of cADPR enhances Ca(2+)-induced Ca2+ release.

A new technique of arterial switch operation with in situ coronary reallocation for transposition of great arteries.

Coronary artery translocation is the most important step in achieving a successful result in arterial switch operations. Although a few centers have reported excellent results, coronary artery transfer requires a high technical expertise. We report a new technique of arterial switch operation without coronary translocation. By creating flaps in the proximal great arteries, the coronaries are transferred to the neoaorta without distortion of their original anatomic position. This technique avoids problems related to coronary translocation. Because coronary buttons are not excised, there is no need for nonviable material to be used in reconstruction of neopulmonary artery. Arterial wall is sutured to arterial wall, so postoperative bleeding is lessened. This technique can be used for any type of coronary anomaly and great arterial relationship. Coronary perfusion is well maintained. Two patients with transposition variants and ventricular septal defects have been operated on successfully with this technique. Postoperative investigations showed good coronary perfusion, without right or left ventricular outflow obstruction or leakage through the semilunar valves. This technique achieves anatomic correction for transposition of the great arteries, just as a conventional arterial switch operation does, but it avoids problems related to coronary artery translocation. We believe that it is a much simpler, more reliable, and more reproducible operation than others in current use, and it can be carried out by many cardiac surgeons with acceptable results. The early results are encouraging, although longer follow-up and more cases are essential.

Expression of functional receptors for vasoactive intestinal peptide in freshly isolated and cultured gastric muscle cells.

Vasoactive intestinal peptide (VIP) receptors were characterized in freshly isolated and cultured smooth muscle cells from guinea pig stomach by radioligand binding and by measurement of relaxation in single isolated and cultured cells. 125I-VIP bound to both freshly isolated and cultured muscle cells: binding was rapid, specific, saturable and temperature-dependent, and was inhibited in a concentration-dependent fashion by VIP, VIP10-28, PHI and secretin, in this order. Competition curves for VIP could be resolved into high- and low-affinity components, yielding similar binding constants in freshly isolated and cultured cells (high-affinity Kd 0.11 and 0.22 nM; low-affinity Kd 59 and 37 nM; high-affinity binding sites: 1183 and 1021 per cell, representing about 1% of total binding sites). VIP10-28 inhibited 125I-VIP binding completely and acted as potent competitive antagonist of VIP-induced relaxation (Ki 0.5 nM). PHI and secretin, however, inhibited partly 125I-VIP binding: the pattern of inhibition implied that VIP interacts with VIP-preferring receptors that are recognized by PHI and secretin as well as with VIP-specific receptors. The pattern of binding is consistent with recent evidence indicating that VIP activates two signalling pathways, a VIP-specific, nitric oxide/cGMP-dependent pathway and a common cAMP-dependent pathway shared by all three peptides. PHI and secretin were relatively more potent as relaxant agents than as inhibitors of 125I-VIP binding raising the possibility that PHI and secretin could interact additionally with PHI- and secretin-preferring receptors in mediating relaxation.

Selective expression of vasoactive intestinal peptide (VIP)2/pituitary adenylate cyclase-activating polypeptide (PACAP)3 receptors in rabbit and guinea pig gastric and tenia coli smooth muscle cells.

In both functional and radioligand binding studies of gastric smooth muscle from rabbit and guinea pig, vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) show equal potency indicating that the receptor type is either a VIP1/PACAP2 or a VIP2/PACAP3 receptor. We have characterized the VIP/PACAP receptor expressed in freshly dispersed and cultured gastric and tenia coli smooth muscle cells of rabbit and guinea pig by reverse transcriptase-polymerase chain reaction (RT-PCR), Northern analysis, and cloning of the first extracellular domain. Specific primers based on cDNA sequences for rat VIP1/PACAP2, VIP2/PACAP3 and PACAP1 receptors were designed spanning the first extracellular domain. A 275 base pair product corresponding to VIP2/PACAP3 receptor was amplified by RT-PCR in muscle cells from both species. No RT-PCR product was obtained with primers for VIP1/PACAP2 and PACAP1 receptors. The deduced amino acid sequences showed 90% similarity in rabbit and 77% in guinea pig to the sequence in rat. The location of the aspartate, tryptophan and glycine residues and all six N-terminal cysteines required for VIP binding were conserved. The sequence in guinea pig tenia coli differed from that in guinea pig stomach by two amino acid residues, Phe40 and Phe41. Northern analysis revealed a single 3.9 kilobase (kb) mRNA corresponding to VIP2/PACAP3 receptors in rabbit and a 2.1 kb mRNA in guinea pig gastric and tenia coli muscle cells. We conclude that only VIP2/PACAP3 receptors are expressed in smooth muscle cells of rabbit and guinea pig. The two amino acid difference in the sequence obtained from guinea pig tenia coli may reflect the distinct binding and functional properties of this tissue.

Novel techniques of bidirectional Glenn shunt without cardiopulmonary bypass.

BACKGROUND: We report novel techniques of performing bidirectional Glenn shunt (BDG) without cardiopulmonary bypass (CPB). METHODS: Five cases of single ventricle and pulmonary stenosis (PS) complex were taken up for BDG without CPB. The criteria for case selection were an unrestrictive atrial septal defect (ASD), no atrioventricular (AV) valve regurgitation, and no other intracardiac defects requiring correction. A temporary shunt was established between the superior vena cava (SVC) and contralateral branch pulmonary artery (PA) for venous drainage during SVC clamping for BDG anastomosis in four cases. In case 5, a shunt was put between the SVC and right atrium (RA) for venous drainage, and modified Blalock Taussig shunt and patent ductus arteriosus (PDA) were left open until the completion of the BDG. RESULTS: Central venous pressure (CVP) increased to a mean of 22.4 mm Hg during SVC clamping, with improvement of oxygen (O2) saturation from 62.4% to 82.4%. After Glenn shunt, CVP and O2 saturation maintained at 13.2 mm Hg and 87.4%, respectively. Postoperatively, there were no neurological abnormalities and no hospital mortality. CONCLUSIONS: Our technique provides an excellent venous drainage with improvement of O2 saturation during SVC clamping. It avoids problems related to CPB and economy. It is easily reproducible, with excellent results in a selected group of patients without compromising the completeness of repair.

A new repair for anomalous left coronary artery.

We report a new technique of left coronary artery implantation to the aorta with interposition of a tube created from the great arterial wall for anomalous left coronary artery from pulmonary artery. This technique was used in 3 patients, of which 2 patients survived. It achieves two coronary artery repair and avoids problems related to extensive mobilization of coronary artery for translocation. It is easily reproducible.

Role of limited posterior thoracotomy for open-heart surgery in the current era.

BACKGROUND: The earliest open-heart operations were performed employing the thoracotomy approach. Over the years, median sternotomy has become the routine way of approaching the heart. However, lately there has been progressive enthusiasm in minimally invasive techniques for accessing the heart. We present our technique of correction of congenital heart defects employing the limited posterior thoracotomy approach. METHODS: From June 1997 to April 1998, 27 patients underwent correction for various intracardiac defects without any mortality. There were 19 ostium secundum defects, with or without other associated anomalies. There were six sinus venosus defects with partial anomalous pulmonary venous connections. Two patients had perimembranous ventricular septal defects, while 2 patients had partial atrioventricular defects. In 2 other patients, pulmonary stenosis was repaired, using pulmonary valvotomy in 1 patient, whereas the other patient required short transannular patch. RESULTS: The median age was 7 years and the median weight was 20 kg. The median skin-to-skin time was 260 minutes. The median bypass time was 63.25 minutes and the median cross-clamp time was 35.0 minutes. All the patients were extubated within 12 hours following surgery and the median ICU stay was 24 hours. Three patients required blood transfusions in the ICU for significant blood loss and the mean chest drainage was 85 cc per 24 hours. None of the patients had phrenic nerve palsies. None of the patients required additional analgesics other than routine ibuprofen or ketorolac tromethamine. Short-term follow-up revealed no functional or physical disability of the thoracic wall and the right arm. All who underwent surgery with this approach were happy with the limited visibility of their scars. CONCLUSIONS: Limited posterior thoracotomy offers a viable alternative for midsternotomy and submammary thoracotomy. It has the advantage of a scar in the back that does not impede the future growth of the breast tissue and the pectoralis major. Our approach does not need any new instruments and hence no contraptions are necessary to perform the operation with this approach. Our results have shown satisfactory short-term results and better cosmesis.

Evolving surgical management for ventricular septal defect, pulmonary atresia, and major aortopulmonary collateral arteries.

BACKGROUND: The purpose of this study was to evaluate the results of various surgical modalities that have been evolving for the treatment of ventricular septal defect, pulmonary atresia, and major aortopulmonary collateral arteries. METHODS: From 1993 to May 1997, 14 patients (group 1) were treated with staged unifocalization through thoracotomies and final repair by midsternotomy. From June 1997 to February 1998, 10 patients (group 2) were treated with midsternotomy, single-stage complete unifocalization, and repair. RESULTS: In group 1, 14 patients had 21 procedures (1.5 procedures per patient), of which 3 patients (21%) had final correction. There were two deaths (14%). One patient died of blocked shunt. Another patient who had aneurysmal dilation of homograft tubes that were used for unifocalization died after final repair because of low cardiac output. In group 2, 10 patients had ten surgical procedures for complete unifocalization and 9 of 10 (90%) of them achieved final correction. One patient with low cardiac output in whom we did not close the ventricular septal defect died (10%) of suprasystemic right ventricular pressure. CONCLUSION: In single-stage complete unifocalization, more patients had final correction. It reduces the number of operations and hospitalization and hence is more cost effective than multistaged procedures.

Action of dantrolene sodium on single motor units of cat muscle in vivo.

Dantrolene sodium, a skeletal muscle relaxant, was investigated for its action on single motor units of the peroneus tertius muscle in cats anaesthetized with pentobarbitone sodium. Motor axons were isolated in ventral root filaments and their muscle units were identified as either fast-fatiguable (FF), fast-resistant (FR), fast-intermediate (FI) or slow-resistant (S). Dantrolene sodium (2 mg/kg) was administered intravenously in a solution of 1,2-propanediol. Effects were observed on the twitches, unfused tetanic contractions and maximal tetanic tensions of 78 motor units in 5 experiments. Contractile tension was depressed whereas muscle action potentials appeared unaffected. Maximal tetani were less depressed than unfused tetani and twitches. The reduction of tension was more pronounced for fast (FF, FR and FI) than for slow units. After drug injection, the mean tensions developed at the end of a 3 s period of stimulation at 40/s were: 13.1%, 10.6% and 12.7% of pre-drug control for FF, FR and FI units, respectively, and 67.1% for S units. Upon prolonged stimulation at 40/s fast units depressed by Dantrolene sodium were able to potentiate back to their initial pre-drug tension.

Calculation of stereotactic coordinates from the computed tomographic scan.

A protocol has been developed to use the GE 8800 scanner and its resident programs to calculate stereotactic coordinates, which has made it possible to use any stereotactic apparatus without modifying the apparatus in order to introduce a cannula into any lesion visualized on a computed tomographic (CT) scan to biopsy tumors, drain abscesses, implant radioisotopes, etc. The CT scanning is done in a routine fashion except that a lateral ScoutView, with the planes of each CT slice indicated, is included. Once the CT scan has been completed, resident programs for measuring distances are used to establish a zero point on a reference plane, from which all other coordinates can be defined. The stereotactic procedure is done at a separate time in the operating room, using the coordinates derived from the CT scan. The ScoutView image is compared to the lateral x-ray film taken during the stereotactic procedure to establish the location of the targets. It has been estimated that the accuracy of this system is 3 mm. Abscesses less than 1 cm in diameter deep within the cerebral hemisphere have been accurately aspirated and tumor biopsies have been successfully taken.

Surgical treatment of major intracardiac lesions associated with discordant atrioventricular connexion.

Thirteen patients with a discordant atrioventricular connexion underwent repair of major associated intracardiac defects. Of the patients, 10 had a discordant ventriculoarterial connexion while 3 had double outlet from the morphologically right ventricle. A ventricular septal defect was the most frequently encountered lesion, present alone or in combination with other lesions in all patients. The other major lesions were pulmonary stenosis in 8, Ebstein's malformation of the left atrioventricular valve in 2, and calcific aortic valve disease in one. The operations performed were closure of the ventricular septal defect in 4 patients, closure of the ventricular septal defect with pulmonary valvotomy in 3 patients (one of whom subsequently underwent replacement of the left atrioventricular valve). Modified Fontan's procedure was performed in 6 patients, one of whom also had replacement of the aortic valve. There was no operative death, although there was one early death on the 40th postoperative day due to septicemia. There has been no late death after an average follow-up of 1.2 years. There was one case of surgically induced complete heart block. All other patients are in normal sinus rhythm in New York Heart Association functional class I or II. Elective repair of major intracardiac anomalies in association with a discordant atrioventricular connexion can now be accomplished safely. The modified Fontan's procedure is a viable alternative in certain cases to the placement of an external valved conduit for relief of pulmonary outflow tract obstruction.