Persistent infection with neurotropic herpes viruses and cognitive impairment

BACKGROUND

Herpes virus infections can cause cognitive impairment during and after acute encephalitis. Although chronic, latent/persistent infection is considered to be relatively benign, some studies have documented cognitive impairment in exposed persons that is untraceable to encephalitis. These studies were conducted among schizophrenia (SZ) patients or older community dwellers, among whom it is difficult to control for the effects of co-morbid illness and medications. To determine whether the associations can be generalized to other groups, we examined a large sample of younger control individuals, SZ patients and their non-psychotic relatives (n=1852). Method Using multivariate models, cognitive performance was evaluated in relation to exposures to herpes simplex virus type 1 (HSV-1), herpes simplex virus type 2 (HSV-2) and cytomegalovirus (CMV), controlling for familial and diagnostic status and sociodemographic variables, including occupation and educational status. Composite cognitive measures were derived from nine cognitive domains using principal components of heritability (PCH). Exposure was indexed by antibodies to viral antigens.

RESULTS

PCH1, the most heritable component of cognitive performance, declines with exposure to CMV or HSV-1 regardless of case/relative/control group status (p = 1.09 × 10-5 and 0.01 respectively), with stronger association with exposure to multiple herpes viruses (β = -0.25, p = 7.28 × 10-10). There were no significant interactions between exposure and group status.

CONCLUSIONS

Latent/persistent herpes virus infections can be associated with cognitive impairments regardless of other health status.

The distribution of neurons expressing calcium-permeable AMPA receptors in the superficial laminae of the spinal cord dorsal horn

The superficial dorsal horn is a major site of termination of nociceptive primary afferents. Fast excitatory synaptic transmission in this region is mediated mainly by release of glutamate onto postsynaptic AMPA and NMDA receptors. NMDA receptors are known to be Ca2+-permeable and to provide synaptically localized Ca2+ signals that mediate short-term and long-term changes in synaptic strength. Less well known is a subpopulation of AMPA receptors that is Ca2+-permeable and has been shown to be synaptically localized on dorsal horn neurons in culture (Gu et al., 1996) and expressed by dorsal horn neurons in situ (Nagy et al., 1994; Engelman et al., 1997). We used kainate-induced cobalt uptake as a functional marker of neurons expressing Ca2+-permeable AMPA receptors and combined this with markers of nociceptive primary afferents in the postnatal rat dorsal horn. We have shown that cobalt-positive neurons are located in lamina I and outer lamina II, a region strongly innervated by nociceptors. These cobalt-positive neurons colocalize with afferents labeled by LD2, and with the most dorsal region of capsaicin-sensitive and IB4- and LA4-positive afferents. In contrast, inner lamina II has a sparser distribution of cobalt-positive neurons. Some lamina I neurons expressing the NK1 receptor, the receptor for substance P, are also cobalt positive. These neurons are likely to be projection neurons in the nociceptive pathway. On the basis of all of these observations, we propose that Ca2+-permeable AMPA receptors are localized to mediate transmission of nociceptive information.

Sudden infant death with periventricular leukomalacia

Periventricular leukomalacia (PVL) is a form of cerebral infarction occurring in neonates, particularly in low-weight and premature infants. PVL is well-known to neonatologists, but generally considered nonfatal. Many infants with PVL die in the hospital with multiple medical problems. Those infants with PVL who survive because of intensive care will have serious motor and sensory deficits, but these problems are rarely recognized before one year of age. When infants with PVL die at home, death seems sudden and unexpected. However, it is important to distinguish death caused by PVL from the Sudden Infant Death Syndrome because the implications for the family are quite different. This case report emphasizes that PVL may be fatal.

Hemoperfusion in a child who ingested diquat and died from pontine infarction and hemorrhage

A 2 1/2 year old boy accidentally ingested the herbicide diquat. Progressive neurologic dysfunction preceded his death 143 hours after poisoning. Brain stem infarction and purpura were noted at post mortem and closely resembled the brain stem pathology in 3 of 7 adults who died after diquat ingestion. Renal, gastrointestinal and pulmonary involvement in this child also resembled that seen in adults after ingestion of diquat. Hemoperfusion was performed six times in an effort to lower the body diquat burden. Cellulose-coated, activated charcoal was first employed 40 hours postingestion and removed diquat from serum with clearances of 104 and 39 ml/minute at the initiation of hemoperfusion and 6 hours later, respectively. Serum diquat concentrations decreased rapidly during charcoal hemoperfusion. However, marked rebound in serum diquat concentrations were noted between charcoal treatments, indicating extensive sequestration of diquat by tissues. Thrombocytopenia and hypocalcemia, the major complications of charcoal hemoperfusion, were easily treated. Unlike charcoal, Amberlite XAD-4 resin hemoperfusion did not remove diquat from serum. Charcoal hemoperfusion may temporarily reduce serum diquat concentrations. Whether the early institution and daily performance of charcoal hemoperfusion will minimize diquat-induced damage to brain and other organs is not clear from this case and will only be determined in future studies.

The oxyphil cell in abnormal parathyroid glands. A study of 114 cases

The parathyroid oxyphil cell is apparently capable of parathyroid hormone secretion. To investigate the significance of oxyphil cells in abnormal human parathyroid glands, we compared histologic and clinical features in a retrospective study of 114 cases of hyperparathyroidism, Parathyroid glands were classified by the presence or absence of significant numbers of oxyphil cells. Significant numbers of oxyphil cells were found in 91% of all cases of secondary hyperparathyroidism, 69% of all cases of single adenoma, and 55% of all cases of primary multiple-gland hyperparathyroidism. Oxyphil cells are more common in women. Among cases of primary multiple-gland hyperparathyroidism, oxyphil cells were associated with greater mean serum calcium levels (P = .003). The oxyphil cell of the parathyroid gland is associated with hyperparathyroidism, and may secrete more hormone than the chief cell.