Biomedical subjects

Jonathan Karp

Publications and source records attributed to Jonathan Karp.

3 recordsLinked to original sources

PubMed2006

Spiny mice (Acomys cahirinus) do not respond to thymus-independent type 2 antigens.

Analysis of the immune system of spiny mice (Acomys cahirinus) has been limited. Originally grouped with Mus, Acomys has recently been placed closer to Meriones (gerbils). This study compared immunity in Acomys, Mus, and Meriones. Lymphocytes from all rodents examined proliferated in response to mitogen and superantigen stimulation. Only Mus T cells responded to anti-CD3 stimulation. Acomys, like Meriones, and Mus that express xid, did not respond to thymus-independent type 2 antigens. Flow cytometric analyses revealed that T cell-specific MAbs did not bind Acomys or Meriones lymphocytes. The B cell-specific anti-CD45R (B220) MAb detected all rodent B cells and revealed the absence of a CD45R(lo) subset in the peritoneal cavity of Acomys and Meriones. Bone marrow from Acomys and Meriones failed to reconstitute B cell function in SCID mice. Thus, in terms of immunity, Acomys appears to be more similar to Meriones than Mus.

Animals↗

PubMed2006

Corticosterone modulates auditory gating in mouse.

Previous studies suggest that circulating glucocorticoids may influence the encoding and processing of sensory stimuli. The current study investigated this hypothesis by measuring the generation (amplitude), gating (recovery cycle), and sensitivity (intensity function) of auditory evoked responses in C57BL/6 mice treated with chronic corticosterone (0, 1, 5, 15, or 30 mg/kg/day for 14 days). We found that low-dose corticosterone (5 but not 1 mg/kg/day) enhanced the amplitude and improved gating of evoked potentials without affecting the intensity function. In comparison, higher doses (15 and 30 mg/kg/day) decreased the amplitude and impaired gating of evoked potentials, also without altering the stimulus intensity function. At all doses, lower amplitudes of evoked potentials were significantly correlated with higher circulating corticosterone levels. These data highlight the need to consider serum glucocorticoid levels when assessing human disease states associated with aberrations of information processing such as schizophrenia and depression.

Animals↗

PubMed2005

Ketamine produces lasting disruptions in encoding of sensory stimuli.

The current study analyzed the acute, chronic, and lasting effects of ketamine administration in four inbred mouse strains (C3H/HeHsd, C57BL/6Hsd, FVB/Hsd, and DBA/2Hsd) to evaluate vulnerability to ketamine as a drug of abuse and as a model of schizophrenia. Serum half-life of ketamine was similar between all strains (approximately 13 min). Also, the ratio of brain-to-serum ketamine levels was 3:1. Examination of multiple phases of auditory processing using auditory-evoked potentials (AEPs) following acute ketamine (0, 5, and 20 mg/kg) treatment revealed C3H/HeHsd mice to be most vulnerable to ketamine-induced alterations in AEPs, whereas FVB/Hsd mice exhibited the least electrophysiological sensitivity to ketamine. Overall, the precortical P1-evoked potential component increased in amplitude and latency, whereas the cortically generated N1 and P2 components decreased in amplitude and latency following acute ketamine across all strains. Brain catecholamine analyses indicated that ketamine decreased hippocampus epinephrine levels in C3H/HeHsd but elevated hippocampus epinephrine levels in FVB/Hsd, suggesting one potential mechanism for AEP vulnerability to ketamine. Based on results of the acute study, the immediate and lasting effects of chronic low-dose ketamine on AEPs were examined among C3H/HeHsd (sensitive) and FVB/Hsd (insensitive) mice. We observed a decrement of the N1 amplitude that persisted at least 1 week after the last exposure to ketamine across both strains. This lasting deficit in information processing occurred in the absence of acute changes among the FVB/Hsd mice. Implications for both ketamine abuse and N-methyl-D-aspartate hypofunction models of schizophrenia are discussed.

Anesthetics, Dissociative↗