Small ubiquitin-related modifier (SUMO)-1, SUMO-2/3 and SUMOylation are involved with centromeric heterochromatin of chromosomes 9 and 1 and proteins of the synaptonemal complex during meiosis in men.

Background: Post-transcriptional modification by SUMOylation is involved in numerous cellular processes including human spermatogenesis. For human male meiosis, we previously showed that the small ubiquitin-related modifier-1 (SUMO-1) protein localizes to chromatin axes in early pachytene spermatocytes, then to kinetochores as meiosis progresses. Here, we delineate possible functional roles based on subcellular localization for SUMO-1 and SUMO-2/3.

Mono-(2-ethylhexyl) phthalate increases spermatocyte mitochondrial peroxiredoxin 3 and cyclooxygenase 2.

Mono-(2-ethylhexyl) phthalate (MEHP), the biologically active metabolite of the plasticizer di-(2-ethylhexyl) phthalate, is a member of a class of chemical compounds with known adverse effects on the male reproductive system. Recent studies showed that oxidative stress and mitochondrial dysfunction in germ cells may contribute to phthalate-induced disruption of spermatogenesis. To determine whether the redox-protein mitochondrial thioredoxin-dependent peroxidase, peroxiredoxin 3 (Prx3), may be a component of germ cell homeostasis mechanisms, this study first examined the physiologic relevance of Prx3 in the rodent testis by determining its cell-specific expression.

Synaptic defects at meiosis I and non-obstructive azoospermia.

Background: Recent advances in immunofluorescence methodology have made it possible to directly monitor protein localization patterns in germ cells undergoing meiosis. We used this technology to examine the early stages of meiosis in testicular material obtained from men presenting for evaluation at infertility clinics.

Methods: Specifically, we compared meiotic progression, synapsis and recombination in 34 individuals with obstructive azoospermia ('controls') to 26 individuals with non-obstructive azoospermia (NOA) ('cases').

Meiotic synapsis proceeds from a limited number of subtelomeric sites in the human male.

The formation of the synaptonemal complex (SC) is a crucial early step in the meiotic process, but relatively little is known about the establishment of the human SC. Accordingly, we recently initiated a study of synapsis in the human male, combining immunofluorescence and fluorescence in situ hybridization methodologies to analyze prophase spermatocytes from a series of control individuals. Our results indicate that synapsis is a tightly regulated process, with relatively little variation among individuals.

Hepatic glutamine metabolism.

Expression of high activities of both glutamine synthetase and glutaminase allows the liver to play a major role in the regulation of glutamine homeostasis. The liver shows net glutamine output in metabolic acidosis, in prolonged starvation and animals bearing tumors, net glutamine uptake in the postabsorptive state, on consuming high protein diets, and in uncontrolled diabetes or sepsis. Liver glutamine synthetase is expressed only in a small population of perivenous cells that allows it to salvage any ammonia not incorporated into urea in periportal cells.