Increased thymic B cells but maintenance of thymic structure, T cell differentiation and negative selection in lymphotoxin-alpha and TNF gene-targeted mice

TNF, lymphotoxin (LT) and their receptors are expressed constitutively in the thymus. It remains unclear whether these cytokines play a role in normal thymic structure or function. We have investigated thymocyte differentiation, selection and thymic organogenesis in gene targeted mice lacking LTalpha, TNF, or both (TNF/LTalpha-/-). The thymus was normal in TNF/LTalpha-/- mice with regard to cell yields and stromal architecture. Detailed analysis of alphabeta and gammadelta T cell-lineage thymocyte subsets revealed no abnormalities, implying that neither TNF nor LT play an essential role in T cell differentiation or positive selection. The number and distribution of thymic CD11c+ dendritic cells was also normal in the absence of both TNF and LTalpha. A three-fold increase in B cell numbers was observed consistently in the TNF/LTalpha-/- thymus. This phenotype was due entirely to the LTalpha deficiency and associated with changes in the hemopoietic compartment, rather than the thymic stromal compartment of LTalpha-/- mice. Finally, specific Vbeta8+ T cell deletion within the thymus following intrathymic injection of staphylococcal enterotoxin B (SEB) was TNF/LT independent. Thus, despite the presence of these cytokines and their receptors in the normal thymus, there appears no essential role for either TNF or LT in development of organ structure or for those processes associated with T cell repertoire selection.     

A mobile group II intron of a naturally occurring rearranged mitochondrial genome in Kluyveromyces lactis

Summary Mitochondrial intron content is variable in the yeast Kluyveromyces lactis. Strains can be divided into three classes depending on the structure of the cytochrome oxidase subunit 1 (COX1) gene: (1) those containing intron K1 cox1.1, (2) those containing K1 cox1.2, 3 and 4 and, (3) those that contain all four introns. In addition, strains belonging to the first class (designated Type B strains), have an altered mitochondrial gene order relative to strains from classes (2) and (3) (Type A, Hardy et al. 1989). Crossing experiments reveal that K1 cox1.1 (a group II intron) transfers at high frequency (89%) to mitochondrial genomes lacking this intron. By contrast, the mobility of the remaining introns (all group I) is of the order of 7%.     

Staging equine seminiferous tubules by Nomarski optics in unstained histologic sections and in tubules mounted in toto to reveal the spermatogenic wave

Nomarski optics were used to identify stages of the spermatogenic cycle of seminiferous tubules in sectioned tissue or in whole dispersed tubules and to characterize the equine spermatogenic wave. Embedded tissues were sectioned at 20 microns. Whole dispersed tubules were obtained by enzymatic digestion of thin slices of fresh testis. Dispersed tubules were fixed, dehydrated in graded levels of alcohol, infiltrated with Epon, and mounted in toto on glass slides. Stages of the spermatogenic cycle could be identified under Nomarski optics in both histologic sections and tubules mounted in toto. Stage dependent nuclear chromatic and cytoplasmic changes in spermatogonia, spermatocytes, and spermatids were evident. Spermatid development included chromatin condensation, nuclear elongation, acrosomal development from the Golgi and proacrosomic granules, migration of the annulus and mitochondrial alignment, and the transient appearance of the chromatoid body and manchette. Both nuclear and cytoplasmic details of Sertoli cells were revealed. In tubules mounted in toto, the spermatogenic wave along the length of the tubules occurred as a consecutive set of stages occupying small regions along the tubular length. The spermatogenic wave in the horse is more similar to that of humans than that of rats. The combination of enzymatic isolation of seminiferous tubules and identification of spermatogenic stages by Nomarski optics facilitates examination of the spermatogenic wave in species whose tubules are tightly bound and not easily teased apart.     

Regional myocardial metabolism of high-energy phosphates during isometric exercise in patients with coronary artery disease

BACKGROUND. The maintenance of cellular levels of high-energy phosphates is required for myocardial function and preservation. In animals, severe myocardial ischemia is characterized by the rapid loss of phosphocreatine and a decrease in the ratio of phosphocreatine to ATP. METHODS. To determine whether ischemic metabolic changes are detectable in humans, we recorded spatially localized phosphorus-31 nuclear-magnetic-resonance (31P NMR) spectra from the anterior myocardium before, during, and after isometric hand-grip exercise. RESULTS. The mean (+/- SD) ratio of phosphocreatine to ATP in the left ventricular wall when subjects were at rest was 1.72 +/- 0.15 in normal subjects (n = 11) and 1.59 +/- 0.31 in patients with nonischemic heart disease (n = 9), and the ratio did not change during hand-grip exercise in either group. However, in patients with coronary heart disease and ischemia due to severe stenosis (greater than or equal to 70 percent) of the left anterior descending or left main coronary arteries (n = 16), the ratio decreased from 1.45 +/- 0.31 at rest to 0.91 +/- 0.24 during exercise (P less than 0.001) and recovered to 1.27 +/- 0.38 two minutes after exercise. Only three patients with coronary heart disease had clinical symptoms of ischemia during exercise. Repeat exercise testing in five patients after revascularization yielded values of 1.60 +/- 0.20 at rest and 1.62 +/- 0.18 during exercise (P not significant), as compared with 1.51 +/- 0.19 at rest and 1.02 +/- 0.26 during exercise before revascularization (P less than 0.02). CONCLUSIONS. The decrease in the ratio of phosphocreatine to ATP during hand-grip exercise in patients with myocardial ischemia reflects a transient imbalance between oxygen supply and demand in myocardium with compromised blood flow. Exercise testing with 31P NMR is a useful method of assessing the effect of ischemia on myocardial metabolism of high-energy phosphates and of monitoring the response to treatment.     

Trisomy 3p23----pter and monosomy 11q23----qter in an infant with two translocation carrier parents.

A newborn male infant with multiple congenital abnormalities was found to be trisomic for 3p23----pter and monosomic for 11q23----qter. His parents were both carriers of a balanced reciprocal translocation. Considerable overlap in phenotype-karyotype correlations was found between the two chromosomal syndromes in the patient.     

Estimation of the genetic contribution of presenilin-1 and -2 mutations in a population-based study of presenile Alzheimer disease

Two closely related genes, the presenilins ( PS ), located at chromosomes 14q24.3 and 1q42.1, have been identified for autosomal dominant Alzheimer disease (AD) with onset age below 65 years (presenile AD). We performed a systematic mutation analysis of all coding and 5'-non-coding exons of PS -1 and PS -2 in a population-based epidemiological series of 101 unrelated familial and sporadic presenile AD cases. The familial cases included 10 patients of autosomal dominant AD families sampled for linkage analysis studies. In all patients mutations in the amyloid precursor protein gene ( APP ) had previously been excluded. Four different PS -1 missense mutations were identified in six familial cases, two of which where autosomal dominant cases. Three mutations resulted in onset ages above 55 years, with one segregating in an autosomal dominant family with mean onset age 64 years (range 50-78 years). One PS -2 mutation was identified in a sporadic case with onset age 62 years. Our mutation data provided estimates for PS -1 and PS -2 mutation frequencies in presenile AD of 6 and 1% respectively. When family history was accounted for mutation frequencies for PS -1 were 9% in familial cases and 18% in autosomal dominant cases. Further, polymorphisms were detected in the promoter and the 5'-non-coding region of PS -1 and in intronic and exonic sequences of PS -2 that will be useful in genetic association studies.      

Paternal mosaicism for a novel PBX1 mutation associated with recurrent perinatal death: Phenotypic expansion of the PBX1‐related syndrome

Autosomal dominant (de novo) mutations in PBX1 are known to cause congenital abnormalities of the kidney and urinary tract (CAKUT), with or without extra‐renal abnormalities. Using trio exome sequencing, we identified a PBX1 p.(Arg107Trp) mutation in a deceased one‐day‐old neonate presenting with CAKUT, asplenia, and severe bilateral diaphragmatic thinning and eventration. Further investigation by droplet digital PCR revealed that the mutation had occurred post‐zygotically in the father, with different variant allele frequencies of the mosaic PBX1 mutation in blood (10%) and sperm (20%). Interestingly, the father had subclinical hydronephrosis in childhood. With an expected recurrence risk of one in five, chorionic villus sampling and prenatal diagnosis for the PBX1 mutation identified recurrence in a subsequent pregnancy. The family opted to continue the pregnancy and the second affected sibling was stillborn at 35 weeks, presenting with similar severe bilateral diaphragmatic eventration, microsplenia, and complete sex reversal (46, XY female). This study highlights the importance of follow‐up studies for presumed de novo and low‐level mosaic variants and broadens the phenotypic spectrum of developmental abnormalities caused by PBX1 mutations.     

Attenuated LTP in hippocampal dentate gyrus neurons of mice deficient in the PAF receptor

Platelet-activating factor (PAF), a bioactive lipid (1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) derived from phospholipase A(2) and other pathways, has been implicated in neural plasticity and memory formation. Long-term potentiation (LTP) can be induced by the application of PAF and blocked by a PAF receptor (PAF-R) inhibitor in the hippocampal CA1 and dentate gyrus. To further investigate the role of PAF in synaptic plasticity, we compared LTP in dentate granule cells from hippocampal slices of adult mice deficient in the PAF-R and their age-matched wild-type littermates. Whole cell patch-clamp recordings were made in the current-clamp mode. LTP in the perforant path was induced by a high-frequency stimulation (HFS) and defined as >20% increase above baseline of the amplitude of excitatory postsynaptic potentials (EPSPs) from 26 to 30 min after HFS. HFS-induced enhancement of the EPSP amplitude was attenuated in cells from the PAF-R-deficient mice (163 +/- 14%, mean +/- SE; n = 32) when compared with that in wild-type mice (219 +/- 17%, n = 32). The incidence of LTP induction was also lower in the cells from the deficient mice (72%, 23 of 32 cells) than in the wild-type mice (91%, 29 of 32 cells). Using paired-pulse facilitation as a synaptic pathway discrimination, it appeared that there were differences in LTP magnitudes in the lateral perforant path but not in the medial perforant path between the two groups. BN52021 (5 microM), a PAF synaptosomal receptor antagonist, reduced LTP in the lateral path in the wild-type mice. However, neither BN52021, nor BN50730 (5 microM), a microsomal PAF-R antagonist, reduced LTP in the lateral perforant path in the receptor-deficient mice. These data provide evidence that PAF-R-deficient mice are a useful model to study LTP in the dentate gyrus and support the notion that PAF actively participates in hippocampal synaptic plasticity.